Page 1

South African

Sugar Technologists'

Association

Proceedings

of the

FORTY-FOURTH

ANNUAL CONGRESS

HELD AT MOUNT EDGECOMBE

15th-19th JUNE, 1970

The Copyright of these papers is the property of the Association

The Association does not hold itself responsible for any of the opinions

expressed in papers published herein

Published by

South African Sugar Technologists'

Association

SOUTH AFRICAN SUGAR ASSOCIATION EXPERIMENT STATION

MOUNT EDGECOMBE, NATAL

PRICE FOR EXTRA COPIES R5.00

Printed in the Republic of South Africa by The Natal Witness (Pty) Ltd.

Proc. Annual Cong. S. Afr. Sugar Tech. Ass. No. 44 pp. 1-216 Durban, 1970

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Proceedings of The South African Sugar Technologists' Association —June 1970

THE SOUTH AFRICAN SUGAR TECHNOLOGISTS' ASSOCIATION

The South African Sugar Technologists' Association was

founded in 1926. It is an organisation of technical

workers and others directly interested in the technical

aspect of the South African Sugar Industry. It operates

under the aegis of the South African Sugar Association,

but is governed under its own constitution by a Council

elected by its members.

The office of the Association is situated on premises

kindly made available to it by the South African Sugar

Association at the latter's Experiment Station at Mount

Edgecombe.

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Proceedings of the South African Sugar Technologists' Association — June 1970

CONTENTS

FRONTISPIECE ii

THE SOUTH AFRICAN SUGAR TECHNOLOGISTS' ASSOCIATION V

OFFICERS OF THE SOUTH AFRICAN SUGAR TECHNOLOGISTS' ASSOCIATION vii

LIST OF MEMBERS AND GUESTS viii

OPENING ADDRESS by D R . G. S. J. KUSCHKE ix

REPLY by M R . A. A. LLOYD xii

PRESIDENTIAL ADDRESS xii

REPLY by M R . i. B. ALEXANDER xvii

SI UNITS IN THE SUGAR FACTORY by G. N. ALLAN AND A. VAN HENGEL 21

CONTAINERISATION by D. S. WILKES 30

T H E FACTORY BALANCE by S.A.S.T.A. CHEMICAL CONTROL COMMITTEE 33

A FACTORY CHLORIDE BALANCE by A. W. MACGILLIVRAY 36

A SOLIDS BALANCE INVESTIGATION by E. L. MULLER . 40

SYRUP WEIGHING AT EMPANGENI by R. D. ARCHIBALD AND M. A. KARLSON 46

D R Y SOLIDS, SPINDLE AND REFRACTIVE BRIX DATA by G. D. M C G R A T H 48

SOME IMPRESSIONS OF THE SUGAR INDUSTRIES OF MAURITIUS AND REUNION by J. R. GUNN 51

NOTES ON AIR POLLUTION IN THE SUGAR INDUSTRY by B. ST. C MOOR 54

WATER CONSERVATION IN SUGAR MILLS by D. J. L. HULETT 57

STAINLESS STEEL IN THE SOUTH AFRICAN SUGAR INDUSTRY by C G. W. ROFFEY AND I. A. ELSDON-DEW . . 60

THE INTERDEPENDENCE OF CANE PREPARATION, PARTICLE SIZE, DISPLACEABILITY, AND LIQUID HOLDUP IN FIXED BED DIFFUSERS b y R . W . REIN . . . . . . 6 4

T H E MUTUAL CLARIFICATION PROJECT—PROGRESS REPORT No . 2 by L.M.S.A. JULLIENNE, M. MATIC AND M. TEOKAROVIC 71

COMPOSITION OF SOUTH AFRICAN FINAL MOLASSES by A. W. MACGILLIVRAY AND M. MATIC 81

FACTORS AFFECTING ENZYMATIC STARCH HYDROLYSIS IN SUGAR SOLUTIONS by I. A. SMITH 88

DECOMPOSITION PRODUCTS OF ENZYMATIC STARCH HYDROLYSIS by J. BRUIN 94

THE ISOLATION AND PARTIAL CHARACTERISATION OF OLI­GOSACCHARIDES IN REFINERY MOLASSES by P. G. MOREL DU BOIL, K. J. SCHAFFLER, G. W. COMRIE AND D. M. OOSTHUIZEN 98

SOME ASPECTS OF FACTORY OPERATION AT THE TONGAAT SUGAR COMPANY FACTORY by G. G. CARTER, W. S. GRAHAM AND B. ST. C. MOOR 104

TRIALS ON B.M.A. CONTINUOUS CENTRIFUGALS by G. G. CARTER 108

IMBIBITION RE-CYCLING by M. H. PHIPSON . 1 1 4

SUMMARY OF AGRICULTURAL DATA: SUGARCANE CROP 1968/69 AND 1969/70 by i. L. DU TOIT AND M. G. MURDOCH 117

OPTIMUM IRRIGATION LEVELS FOR CANE UNDER BURNT AND TRASHED CONDITIONS Ay J. M. GOSNELL . . 121

SOME ASPECTS OF THE USE OF PLASTIC PIPING IN LAND DRAINAGE by B. PITHEY 131

STOOL POPULATIONS AND YIELD OF SUGARCANE UNDER IRRIGATED CONDITIONS AT PONGOLA by i. P. BOYCE 136

THE TONGAAT FIELD DIARY — A USEFUL MANAGEMENT TOOL by J. N. S. H I L L 144

THE RESULTS OF PRE-EMERGENCE HERBICIDE SCREENING TRIALS FOR SUGARCANE IN NATAL by F. E. RICHARDSON 148

A COMPARISON OF METHODS OF PHOSPHATE APPLICATION TO RATOON CANE by P. K. MOBERLY AND G. H. WOOD . 155

SOIL STERILIZATION AND THE GROWTH OF TOPS AND ROOTS AT THE MOUNT EDGECOMBE ROOT LABORATORY by J. GLOVER 162

PERKINSIELLA SACCHARICIDA KIRKALDY (HOM: DELPHA-CIDAE) AN INSECT PEST OF SUGARCANE IN SOUTHERN A F R I C A ^ R . H . G . H A R R I S 169

ALUMINIUM TOXICITY — A GROWTH LIMITING FACTOR IN SOME NATAL SANDS by M. E. SUMNER . . . . 1 7 6

THE EFFECT OF SILICA ON CANE GROWTH by P. DU PREEZ 183

T H E INFLUENCE OF WATTLE-BRUSH BURNING ON CANE GROWTH by J. H. MEYER 189

A COMPARISON OF THE EFFECTS OF UREA AND SULPHATE OF AMMONIA ON SUGARCANE by J. M. GOSNELL . . 200

LEAF SCALD DISEASE OF SUGARCANE IN SOUTH AFRICA by G. ROTH AND G. M. THOMSON 204

WEATHER REPORT FOR THE YEAR 1ST JUNE, 1969 — 31ST MAY, 1970 b y J . GLOVER . . . . . . 208

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Proceedings of The South African Sugar Technologists' Association —June 1970 vn

OFFICERS 1970-71

President T. G. CLEASBY

Hon. Secretary (Mrs.) M. WELLS

Life Patron DR. H. H. DOODS

Vice-President J. B. ALEXANDER

Hon. Technical Secretary D. J. COLLINGWOOD

Former Presidents

1926-27 M. Mc MASTER 1927-28 M. Mc MASTER 1928-29 H. H. DODDS 1929-30 H. H. DODDS 1930-31 G. S. MOBERLY 1931-32 G. C. DYMOND 1932-33 G. C. DYMOND 1933-34 B. E. D. PEARCE 1934-35 E. CAMDEN-SMITH 1935-36 G. C. WILSON 1936-37 G. C. WILSON 1937-38 J. RAULT 1938-39 P. MURRAY 1939-40 P. MURRAY 1940-41 E. P. HEDLEY

1941-42 1942-43 1943-44 1944-45 1945-46 1946-47 1947-48 1948-49 1949-50 1950-51 1951-52 1952-53 1953-54 1954-55 1955-56

F. W. HAYES A. MCMARTIN G. BOOTH G. S. MOBERLY G. S. MOBERLY W. BUCHANAN W. BUCHANAN J. L. DU TOIT H. H. DODDS A. MCMARTIN G. C. DYMOND G. C. DYMOND G. C. DYMOND G. C. DYMOND J. B. GRANT

1956-57 1957-58 1958-59 1959-60 1960-61 1961-62 1962-63 1963-64 1964-65 1965-66 1966-67 1967-68 1968-69 1969-70

J. B. GRANT J. P. N. BENTLEY J. P.N. BENTLEY J. P. N. BENTLEY J. L. DU TOIT J. L. DU TOIT J. L. DU TOIT J. R. GUNN J. R. GUNN J. R. GUNN L. F. CHIAZZARI L. F. CHIAZZARI T. G. CLEASBY T. G. CLEASBY

Former Vice-Presidents

1926-27 1927-28 1928-29 1929-30 1930-31 1931-32 1932-33

L. E. ROUILLARD H. H. DODDS G. S. MOBERLY G. S. MOBERLY G. C DYMOND A. C. WATSON A. C. WATSON

1934-34 J" G. C. DYMOND "\ E. CAMDEN-SMITH

1934-35 1935-36 1936-37 1937-38 1938-39 1939-40 1940-41

B. E. D. PEARCE E. CAMDEN-SMITH J. RAULT P. MURRAY E. P. HEDLEY E. P. HEDLEY F. W. HAYES

1941-42 1942-43 1943-44 1944-45 1945-46 1946-47 1947-48 1948^19 1949-50 1950-51 1951-52 1952-53 1953-54 1954-55 1955-56

{

A. MCMARTIN 1956-57 G. BOOTH 1957-58 F. B. MACBETH 1958-59 G. BOOTH 1959-60 W. BUCHANAN 1960-61 G. C. DYMOND 1961-62 G. C. DYMOND 1962-63 G. C. DYMOND 1963-64 J. L. DU TOIT 1964-65 O. W. M. PEARCE 1965-66 O. W. M. PEARCE 1966-67 K. DOUWES-DEKKER 1967-68 J. B. GRANT 1968-69 K. DOUWES-DEKKER 1969-70 G. C. DYMOND

W. G. GALBRAITH

W. G. GALBRAITH J. L. DU TOIT J. L. DU TOIT J. L. DU TOIT J. DICK J. P. N. BENTLEY J. P. N. BENTLEY L. F. CHIAZZARI L. F. CHIAZZARI L. F. CHIAZZARI T. G. CLEASBY T. G. CLEASBY J. B. ALEXANDER J. B. ALEXANDER

J. B. ALEXANDER G. S. BARTLETT J. P. N. BENTLEY L. F. CHIAZZARI

Council of the Association

T. G. CLEASBY D. J. COLLING WOOD J. L. DU TOIT J. R. GUNN

D. J. L. HULETT W. B. KRAMER T. R. LOUDON M. MATIC

G.W. SHUKER G. D. THOMPSON J. WILSON

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viii Proceedings of The South African Sugar Technologists' Association — June

List of members and guests who attended the

Forty-fourth Congress 15th-19th June, 1970

ABEL, E. J. M. ALEXANDER, H. P. ALEXANDER, J. B. ALEXANDER, K. E. F. ALLAN, G. N. ANDERSON, J. ANDERSON, N. ANDRIES, P. A. ASHE, G. G.

BAILEY, E. D. BANI ABBASSI, N. BARNES, A. C. BARTLETT, G. S. BAX, G. BEATER, B. E. BENTLEY, J. P. N. BERGH, P. BISHOP, R. T. BLACK, W. B. BLAKE, B. V. BOAST, W. B. BOND, R. S. BOOYSEN, S. S. BOURNE, J. H. BOWES, N. I. BOYCE, J. P. BRETT, P. G. C. BREWITT, A. J . D. BRIGGS, R. H. BROKENSHA, M. A. BROMLEY, C. K. BROWNE, E. L. BROWN, J. W. BROWN, P. W. BROUARD, J. E. P. BRUCE, N. E. BRUIJN, J. BUCHANAN, E. J. BULLOCK, J. S. BURNS, R. F. BYARD, W. E. BYRNE, L. G.

CAIRNS, P. A. CAMDEN-SMITH, D. CAMPBELL, R. CARGILL, J. M. CARNEGIE, A. J. M. CARR, R. J. CARREYETT R. A. CARTER, G. G. CHADWICK, J. K. CHANCE, W. J. F. CHIAZZARI, L. F. CHRISTIANSON, W. O. CLEASBY, T. G. CLUTTERBUCK, N. F. COETZEE, D. J. COLE, E.

COLLINGWOOD, D. J . COLLINGWOOD, R. J. COMRIE, G. W. CONUN, G. H. COURTS, B. COUVE, J. COVAS, T. CROOKES, D. V. CROOKES, L. N. CROOKES, P. J. CROOKES, P. J. M.

DANESH DEZFULI, A. R. DAHL, R. G. DAVIES, W. F. DAWES, V. H. DECKER, G. DEDEKIND, E. T. J. DENNY, M. E. DENT, C. E. D'HOTMANDE VlLLIERS, O Mc. D. DICK, J. DICK, J. DODDS, H. H. DOUGLAS, E. DOVEY, P. A. DUCKWORTH, J. R. DUNSMORE, (MRS.) A. DURANDT, H. K. DEFROBERVILLE, P. DE RAUVILLE, F. DE ROBILLARD, P. M. DE RUYTER, A. J. M . J . DE LA FAYE, G. DU TOIT, J. L. DU PREEZ, P.

EDRISSI, S. M. H. EDWARDS, B. R. EDWARDS, J. ELLIOTT, H. F. ELLIS, (MRS.) E.

FAGAN, R. C. FARQUHARSON, J. B. FAYDHERBE, R. E. FERNS, W. FOKKENS, F. FORD, R. H. FOTHERINGHAM, H. FRANCIS, D. W. FRANGS, G. B. FREAN, N. H. FREAMS, G.

GlLHLLAN, E. C. GIRDLER, J. GIRLING, L. A. GLISSON, F. G. GLOVER, J. GOSNELL, J. M. GOURLEY, I. N. GRAHAM, W. S. GRANGER, J. B. GREENFIELD, M. S. GRICE, L. D. C.

HAGE, P. HAEE, N. G. HALL, D. M. HALSE, C. G. HALSE, R. H. HALSTEAD, E. HAMLYN, D. HAMMOND, A. G. HAMMOND, G. P. HANKINSON, A. D. HARDIE, J. G. HAREL, J-P. HARMSWORTH, J. HARRIS, R. H. G. HARRIS, V. G. HAVEMANN, C. H. HAYSOM, G. D. L.

HEBBLETHWAITE, J. HELINGA, D. N. HEMPSON, W. J. HILL, D. R. HILL, J. N. S. HILL, T. I. HOEKSTRA, R. G. HOLTON, S. G. HOPKINS, T. HOWES, A. M. HULETT, D. J. L. HULETT, H. B. W. HULETT, J. R. HUNTLEY, J. K.

IRLE, E.

JAMES, G. L. JEHRING, G. JENKINS, E. B. JENNINGS, R. JOHNSTON, H. W. JOHNSTON, M. A. JONES, F. R. JULLIENNE, A.

KARLSON, M. A. KELLERMAN, G. H. KING, N. C. KING, S. KING, S. T. N. KOENIG, M. J. P. KOENIG, P. KRAMER, F. A. KRAMER, W. B. KRUMM, (MRS.) G. KUSCHKE, G. S. J.

LAAPER, J. N. LABUSCHAGNE, A. W. LAMUSSE, A. LAMUSSE, J. P. LANDREY, O. P. LAUGHTON, (MISS) M. LAX, R. LEANDY, C. A. LECLEZIO, R. LESUR, G. LINDEGGER, R. LINTER, J. LIONETT, R. E. LONG, A. C. LOUDON, T. R. LUND, G.

MACGRATH, G. MACGREGOR, W. I. MACVICAR, C. N. MAGASINER, N. MANDY, S. MANN, Q. V. LABAT MARC. MARKHAM, R. J. MARSHALL, D. MARTENS, W. MARTIN, J. MARTIN, W. MATIC, M. MEYER, G. H. MEYER, J. H. MEYER, N.

MITCHELL-INNES, MISS L. MOBERLY, P. K. MORGAN, C. E. MORGAN, M. MOOR, B. ST. C. MOREL DU BOIL, MISS P. MORRIS, B. S. MORRISON, E. MORRISON, K. F. MORTAZANI, S. N. MULDOON, R. MULLER, E. L. MURDOCH, M. G. MURRAY, J. P. M A C GILLIVRAY, A. W. Me KENNA, A. Mc NAUGHTON, A.

NORTH-COOMBES, S.

ODENDAAL, C. J. O 'DONOVAN, G. P. DIGBYOVENS, R. OLDFIELD, J. S. B. ORCHARD, E. R.

PALMER, J. H. K. PAYN, G. C. PEARCE, O. W. M. PEARSON, C. H. O. PENFOLD, V. PENNEFATHER, M. PERK, C. G. M. PERSHOUSE, G. V. PHEASANT, B. PHIPSON, M. H. PITHY, L. B. POLE, R. PREEN, B. V. PRESTON, W. H. PRINCE, P. PRINGLE, D. H. PSIFIS, A. M.

RABE, A. RAFFRAY, C. G. RANK, J. N. RAULT, J. RAVAISOU, G. B. REIN, P. W. RENAUD, C. L. RENNIE, L. L. RENTON, R. RIC-HANSEN, R. W. RICHARDSON, F. E. RISHWORTH, A. W. RITCHIE, G. A. D. ROBERTSON, J. M. RODGER, B. ROSTRON, H. ROTH, G. ROUTLEDGE, D. A. RUSK, G.

SAUZIER, J. SAVILLE, R. F. SAYERS, A. D. SCHAFFLER, K. J. SEMPILL, N. D. SCHMIDT, C. G. SCHMIDT, H.

SCHUMANN, G. T. SERRURIER, C. SHARP, W. SHERRARD, C. D. SHUKER, G. W. SINGERY, L. C. SIMMS, C. H. SMITH, I. A. SMIT, J. DU T. SOFFIANTINI, V. A. SOUCHON, C. L. A. SOUCHON, G. H. SOUCHON, M. H. T. STATHAM, R. STEAD, B. A. STENDER, O. STEFFEN, J. E. L. STEIN, A. G. STEWART, B. STEWART, MISS P. STEWART, M. J. STRACHAN, D. W. STRACHAN, MRS. E. R. STROVER, R. M. SUMNER, M. E.

TAYFIELD, D. TAYLOR, A. J. M. TOEKAROVIC, M. 1 HERON, C. H. B. THOMAS, J. P. THOMSON, G. M. THOMSON, MISS S. THOMPSON, G. D. TOMLINSON, K. TOY, W. F. TURNER, Q. A.

VANIS, M. VINTON, MISS J. VAN DOKKUM, J. VAN HENGEL, A. VAN NlEKERK, G. J. VAN DER POL, C . VAN DER RIET, F. E. VON DE MEDEN, E.

WADE, D. C. WALSH, W. H. WARNE, D. E. WATSON, V. WELLS, MRS. M. WESSELS, M. H. WHITEHEAD, C. WILKES, D. WILKES, MRS. H. WILKINSON, A. D. WILLIAMS, A. WILLIAMS, A. H. WILLIAMS, J. WILSHER, J. P. WILSON, B. T. WISE, C. T. WISE, P. WOOD, R. A. WORMALD, T. C. WORTHINGTON, R.

YOUNG, C. M.

ZADRKZIL, M. W.

Jk

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FORTY-FOURTH ANNUAL CONGRESS

Proceedings of the Forty-fourth Annual Congress of the South African Sugar Technologists' Association, held at the South African Sugar Association's Experiment Station, Mount Edgecombe, from the 15th to 19th June, 1970.

-June 1970

NNUAL CONGRESS

,ial Congress of the South African Sugar the South African Sugar Association's ibe, from the 15th to 19th June, 1970.

Proceedings of The South African Sugar Technologists'' Association

The President: Ladies and Gentlemen — I have great pleasure in asking Dr. G. S. J. Kuschke, Chairman of the Industrial Development Corpora­tion, to open our Forty-fourth Annual Congress.

OPENING ADDRESS Dr. Kuschke: Mr. President, Dr. Dodds, Ladies

and Gentlemen. In view of the traditional and vital place of agriculture in the South African economy as earner of foreign exchange and supplier of raw materials, the South African Sugar Industry can be proud of its record.

Its achievements demonstrate that the challenges facing many of the industries in the coming decade can be met successfully, if approached with imagina­tion and determination.

Countries, and even regions within countries, are differently endowed with productive resources. Some may be richer than others in their wealth of capital, other countries may benefit from the size, skills and initiative of their people. Mineral wealth or good soil and climate for agricultural production may give others an advantage.

A combination of a country's wealth of these re­sources and, the way in which they are applied inevitably shape its growth pattern.

A country endowed with resources to facilitate a sizable agriculture sector, and equally well endowed with mineral weath provides its industry with a strong base for advancement.

In the initial stages of a country's economic de­velopment, this usually takes the form of export earnings by agriculture and mining to pay for the much needed imports of capital equipment. With this the country can start to build railroads, tele­communication and other infrastructural facilities. Equally important, these earnings can also pay for the machinery needed to start factories.

As manufacturing expands the relationship between agriculture, mining and other sectors be­comes more complex. Agricultural and mining pro­ducts go into manufacturing industry as raw materials. As a matter of fact, the presence of these raw materials at advantageous prices is a vital base for the establishment of the factories.

Manufacturing progressively pulls people into em­ployment and higher income brackets, which enlarges the market for agricultural and other products. Thus,

the whole process of growth and industrialisation is launched.

South Africa has already advanced a long way on the road of industrialisation. This must to a large extent be ascribed to the country's relatively favourable position in respect of the various pro­ductive resources.

However, all development and growth are de­termined by the limitations imposed by available re­sources. We are all aware of their nature: inter alia, shortages in skilled labour, capital, water, transport.

In some resources we have abundance, such as some minerals, and the wonderful climate which is really too good so that it brings the problems of water supply and consistent agricultural production.

It is into this frame that we have to fit our canvas and paint the economic picture as we see it.

Although climatic conditions and the quality of our soil limit us to intensive cultivation of only 10% of the total surface area of the country, the agricul­tural sector is more vital to our economy and, in particular to manufacturing industry, than the 11 % contribution the Gross Domestic Product tends to tell.

Agriculture is as much as it ever was, a vital member of our economic family, and in 1967 pro­duced goods to the value of some Rl 500 million.

In that year (the latest for which figures are available) no less than 52% or R781 million went as raw materials for our domestic manufacturing in­dustry. Agricultural exports amounted to R271 million.

Agricultural raw materials bought by manufac­turing in 1967 constituted 21.9% of industry's total demand for raw materials.

In that same year, 1967, the food processing in­dustry in the Republic produced goods to the value of Rl 257 million and exported R184 million.

Exports of agricultural products in the ten-year period of 1958 to 1968 amounted to 24% of our total exports excluding gold.

These earnings were equal to 71% of total im­ports of machinery (excluding motorcars, etc.).

The roots of agriculture in South Africa's inter­national trade go deep. A large proportion of South Africa's exports of manufactured products has agriculture as its base. To illustrate this we need mention only one sector, the food processing

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X Proceedings of The South African Sugar Technologists' Association — June 1970

industry, which represents 25% of the total exports of manufactured products.

The impact of agriculture on our economy as a whole and the manufacturing industry in particular is therefore considerable, and the well-being of one can not be divorced from the other.

A projection to the end of this decade indicates by 1979:

Gross value of agricultural production, R2 400 million.

Supply to domestic industry, Rl 250 million. Gross value of food processing output, R2 300

million. Exports of agricultural products, R440 million. Exports of processed agricultural products, R350

million. This is perhaps not dramatic growth, but it is solid

growth, and therefore provides a sound foundation. And there is nothing to stop it growing.

On the contrary, more sophisticated methods and management, mechanisation and use of industrial products such as fertilizers, weed-killers, dips and other chemical products, will ensure intensity of farming growth and steadily enhanced productivity. Similarly, greater productivity of the labour em­ployed has already made for better results, and this will continue steadily.

The same pattern applies to our mining industry, even though we might for a moment exclude the role of the dominant gold mining industry from our calculations.

We estimate the contribution of the mining sector (excluding gold) to Gross Domestic Product at only 4%, but supplies of raw materials to manufacturing amounts to 7% of total demand. At the same time export earnings amounted to 24% of total exports (excluding gold) for the period 1958 to 1968. There­fore as earner of foreign exchange mining (exclud­ing gold), is of the same magnitude as agriculture. In the same period (1958-1968) exports of manufac­tured products amounted to 50% of total exports (excluding gold), while the contribution of manufac­turing to Gross Domestic Product was 28% in 1968.

The total export performance in manufactured goods is therefore almost exactly equal to the com­bined results of agricultural and mining exports, excluding gold. This, however, is not enough since the negative contribution by industry to our balance of payments at present amounts to R450 million per annum and on the expected and desired growth rate, assuming the present import/export ratio is to be maintained, would amount to Rl 100 million deficit per annum by the end of this decade. This therefore demands a considerable improved per­formance by industry.

From the foregoing, it is clear that the considerable advances in South Africa's manufacturing industry would not have been possible without the particular characteristics, and qualities of our agricultural and mining sectors.

However, the past 20 years have demonstrated to us that South Africa's economic future will largely depend on the advances of manufacturing industry. This will also benefit agriculture through the income

generating effect of a rapid industrial expansion. This does not only mean that an increase in the income of people presently employed, will occur, but the large numbers of our growing population presenting themselves for employment will be given their right­ful privilege of working and making their contribu­tion to the Republic's economy, and at the same time enhancing their standard of living.

Economic growth does not come by itself. Obstacles are many and we must continuously plan our course to make the best use of our resources. This we can already see in our efforts, especially this year, to conserve our scarce water resources.

In the years to come, South Africa will be forced to increase its exports, not only of agricultural and mining products, but particularly those of manufac­tured goods. The earnings of our gold mining in­dustry, which in the past supplied the bulk of our foreign exchange earnings, may diminish in the years to come.

Incidentally, I do not believe that this will be the case, given an aggressive marketing and research approach for industrial and other non-monetary uses of gold. Be all that as it may, in the period 1958-68, gold -supplied 38.3% of South Africa's exports (in­cluding gold).

Our ever-expanding imports demand an improved export performance, which will have to come from minerals, agricultural products and above all manu­factured goods. There is still an arms-length, and virtually disinterested, approach to exports by most of our manufacturers. I find this disturbing indeed since a day of reckoning will come if manufacturing industry does not balance its import/export account. Manufacturing industry cannot expect to be riding on the backs of other sectors in so far as export earnings are concerned. The deficit caused by industry's imports must be

filled by greater exports of manufactured articles. This objective must become a national philosophy, and a way of life—but it needs effort and application.

To enable our manufactured products to com­pete successfully on the international market, we will have to keep costs at the lowest possible level at each stage of the production process. This can only be attained with continuous productivity gains.

Drought and other natural phenomena makes this not easy to attain in the agricultural sector. How­ever, viewed over the long term, our farming com­munity has succeeded in this. In the period 1947/48 to 1966/67 the physical volume of agricultural pro­duction increased at an average rate of 4% per annum. At the same time total acreage increased only marginally which implies substantial increases in productivity, if measured in this way. However, increases in production are not attained that easily, as you know better than I do. The farming com­munity had to incur heavy expenses in respect of modern farming equipment, fertilizers and all other tools which research introduced on the farm. It therefore, does not necessarily follow that unit pro­duction costs decreased in this period.

For the future, efforts in research will be im­portant to keep production costs as low as possible.

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-JUM 1970 Proceedings of The South African Sugar Technologists'' Association

This is not only true from the profit point of view, but productivity gains in agriculture have a direct bearing on the competitiveness of a large pro­portion of South Africa's exports.

The years to come will not be without obstacles. Agriculture and the manufacturing industry will have to find ways and means to overcome the harmful effects should Britain enter the European Comman Market.

Less developed countries all over the world are awakening to modern farming methods. Although most of their production is, and for years to come will be confined to, their respective home markets, the present world supply and demand position will change as a result.

Some countries also will find it advantageous to enter the export markets, which will mean keener

, competition facing traditional world suppliers. As these countries will probably produce at lower labour costs than the more advanced countries, tradi­tional suppliers will have to rely on efficiency and in­creasing productivity.

In a world which continuously requires of us adjustments to changing conditions and, in view of the traditional and vital place of agriculture in the South African economy as earner of foreign exchange and supplier of raw materials, the South African Sugar Industry indeed can be proud of its record.

The achievements of the Sugar Industry demon­strate that the challenges facing many of our indus­tries in the coming decade can be met successfully, if approached with imagination and determination.

In this respect I want to mention your achievement of increasing your position as a sugar exporter from seventh in 1965 to fourth in 1969. This was achieved in the most adverse of conditions. After relatively high world prices in the early years of the decade, dramatic increases in production and exports were achieved in a time of extremely low international prices. Your determination and those of the govern­ment to fix your sights on the long-term benefits to be derived from this, resulted in South Africa now being one of the major sugar producers of the world.

The excellent results of your sterling efforts now also deserve better international prices, and we hope with you that these will improve to the benefit of your Industry.

It is significant that this success could not have been achieved without breaching the barriers which face so many industries through the relative smallness of the South African market. Although the home market assisted in your strategy, perhaps particularly as a result of the local price policy, the international market is the only one which could absorb the rapid expansion in production.

This is demonstrated by the change in reliance on the home market. Whereas the home market con­sumed 66% of total production in 1960 and only 34% was exported, today 52%, is exported and only 48% is consumed locally.

Another achievement was the diversification in export markets effected during the nineteen sixties.

In 1960 88% of sugar exports went to the U.K., Rhodesia and Canada. In 1968 77% of total exports went to Japan, Canada and the United States.

These achievements made Sugar one of the fastest growing sectors in South African agriculture. In the period 1960 to 1969 the Sugar Industry grew at an average annual rate of no less than 7.7% compared with all agriculture advancing at 4% per annum.

Agricultural exports increased at a rate of 6% per annum since 1960. This was enhanced by the growth in exports of sugar at a rate of 8%, per annum. This is indeed phenomenal—and may your success con­tinue.

Research, and combined as well as individual efforts by grower, miller and research officer to make the Sugar Industry the most efficient one in agri­culture, all played a role in your achievements. Many sectors of industry and agriculture can take a lesson from the way in which the Sugar Industry incurred, without hesitation, expenditure on research. Expenditure on research in your industry amounted to R1.5 million in 1967/68 of which the industry contributed R1.4 million.

This money was certainly put to good use, as is illustrated by the fact that yield per acre increased at an average rate of 2.1",', per annum over the period 1947-1967.

At the same time research contributed to increased efficiency and productivity in the use of water and labour, the increase in the sucrose content of sugar­cane, better use' of soils, cane-breeding and several other aspects.

The South African Sugar Industry is in high esteem among the world producers, and the advisory work you do for neighbouring states is in the best tradition of research and the advancement of less developed countries.

In all our growth and development we have to look into the future.

The picture I see is that South Africa will con­tinue to provide its growing population with a rising income and standard of living. The present Gross Domestic Product per capita of- our population of R19 million is R530 per annum, and I believe that it will be some Rl 500 per capita per annum by the year 2000.

Our total population will exceed 40 million by that time but on this projection and expectation this large population will have a per capital Gross Domestic Product equivalent to the average for Europe today.

I do not know what the saturation point of sugar consumption per capita may be but it seems to be of the order of 45 kg. per annum per person.

This would mean that the Sugar Industry will have a domestic market of some 2 million tons by the year 2000.

This is approximaately equal to the present pro­duction in the Republic. It is, however, unthinkable that there will be no further increase in production, or that there will be no exports by that time because the local market has absorbed the full output. It is

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Xll Proceedings of The South African Sugar Technologists' Assocation —June 1970

probably true that South Africa's acreage for sugar production is limited and increases will therefore have to rely on increased yields per acre. This once again highlights the emphasis and continued efforts in the field of research.

South Africa's Sugar Industry must continue to supply the world market and remain a substantial earner of foreign exchange. Optimistic forward pro­jections indicate that the market should be there through the combination of total population growth of the world and the enhancement of the standard of living of the many millions throughout the world who are not yet substantial consumers.

The United Nations projects a population in AD 2000 of 6 200 million. Total sugar consumption at that lime for the world as a whole, calculated at South Africa's present consumption level, would mean a demand in excess of 200 million tons per annum. This is more than three times the present world production.

There is no doubt that new areas elsewhere in the world will come into cultivation and that technical knowledge will continue to increase the yields. South Africa cannot participate to a meaningful extent in production expansion through increases in acreage under cultivation and it will therefore have to main­tain its position through increased yield and efficiency.

The performance of our Sugar Industry to date leads one to say with complete confidence that our country will maintain its position as a supplier of sugar to the local market but also remain an exporter at high level.

A large market tends to bring new products into the supply area and the Sugar Industry will at all times have to take note of possible future competi­tion from artificial sweeteners. There have been threats in this direction in the past and there has probably been a breathing space through the ban­ning of the use of cyclamates in the United States of America. This will, however, not be the last word in what could be a very lucrative market.

The future competitive position of our Sugar In­dustry will therefore depend on price and a very vigilant marketing policy which must needs be built on an efficient and low-cost operation.

It gives me great pleasure to declare your Congress open.

Mr. A. A. Lloyd, in reply to Dr. Kuschke's open­ing address:

Mr. President, Dr. Dodds, Dr. Kuschke, Ladies and Gentlemen.

Our Association has established a reputation for the distinguished guest speakers who have done us the honour of opening its Annual Conference.

They have come from within our own country and from overseas and we have been privileged to hear eminent scientists, doctors, professors and directors of research.

But seldom, if ever, have we had the unique experience of listening to a man who in 1970 stands among the leaders of industrial development in a country which is among world leaders in this field.

I regard it therefore, as a great privilege to have been invited to express on behalf of our Association, our sincere thanks and appreciation to Dr. Kuschke, for his most stimulating, inspiring and thoughtful address to us this morning.

He and I have a few things in common. If we may accept the findings of the Financial Mail, who elected him "Business Man of the Year in 1967" — then I can safely say that neither of us own a yacht, nor a sprawling country estate — nor were we million­aires — at least not in 1967. The share market has probably ensured that this happy state is less likely in 1970.

But from these negative similarities the pattern changes, and I, being somewhat of a specialist in sugar, find it quite impossible to match the brilliance of his industrial and business record since 30 years ago he forsook an academic career offered under a Rhodes scholarship.

Since the departure from the scene of Dr. van der Bijl and Dr. Hendrink van Eck, a new leader of industry has arisen. How else can I describe a man who today not only directs the policy of the Indus­trial Development Corporation as its chairman after 21 years of dynamic contribution, but today is chair­man of 16 companies, director of 31 others and serves on the Prime Minister's scientific and econ­omic advisory board; the Orange River project as President of the Institute of Management and in numerous other capacities.

It takes me all my time to concentrate on sugar, but our distinguished guest is deeply involved in carpets, china, cellulose, chemicals, coal, oil and gas. He is concerned with textiles, porcelain, aluminium, zinc, platinum, iron, steel, pulp and paper. His interests include shipping and aircraft, phosphate and knitware, water and electricity, metals and minerals, banking and finance.

This is a breathtaking record of a man who by hard work, big thinking, meticulous planning and collective inspiration of a staff of over 100 executives, coupled with an enlightened approach to manage­ment which is noted for its fluency, drive and success, has made an enormous contribution to the industrial development of our country.

We are indeed fortunate to have been afforded the opportunity of hearing an outstanding speaker who is said to deliver 30 addresses every year.

He has brought to our industry a breadth of vision and infused us with his own spirit. For this we are most sincerely grateful to him for the sacri­fice of valuable time to come here and address us today.

On your behalf, I thank Dr. Kuschke most warmly for a great contribution to the success of our 44th Congress which he has so ably declared open.

PRESIDENTIAL ADDRESS

Dr. Dodds, Dr. and Mrs. Kuschke, distinguished guests, fellow technologists.

In rising to address you as your President for the second time, my task of finding a subject has been made easier by the Government's decision to

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-June 1970 Proceedings of The South African Sugar Technologists' Association

declare 1970 as Water Year. A great deal has already been written and said about it, but I feel as techno­logists and as an industry, the subject of water is so important that one more contribution — I hope an objective one — will not be out of place.

Let be say at the outset that the idea of focusing attention on water in this way, and at this time, is most commendable. What is important, however, are the results which will follow the detailed delibera­tions which are taking place and, in particular, their impact on the sugar industry. Water Year 1970 is a subject which gives me an opportunity of highlight­ing a number of the submissions made by the Sugar Industry to the Commission of Inquiry into Water Resources during 1967 and 1968 and which, I understand, will shortly be presenting its findings to the Government. This information involves facts and figures accumulated by a large number of people, and I would like to gratefully acknowledge their work. At a personal level I am able to utilise a contribution I made on behalf of the South African Sugar Technologists' Association at the Symposium recently held in Durban to mark Water Year 1970. The economy of effort appeals to me and I hope it will not detract from the importance of what I have to say.

To quote from one of the Water Year publications: "Water is basic, it is cheap, it is bountiful and always available". Have you ever thought what would happen the day you turned on the tap and there was no more water? Or too little water for a bath? Or too little to keep a factory going? South Africa is a land of plenty. Its mineral resources are virtually unlimited. On the African Continent it is the undisputed leader in all spheres. The most important factor that will affect its future growth is water. South Africa's water shortage is not a problem that arose overnight. The country's natural water resources remained constant whilst its popu­lation and economy grew spectacularly — a process that creates greater demand day by day.

Our average rainfall is 460 mm (220 million mor-gen feet) per year, of which 91% evaporates or transpires and only 20 million morgen feet reaches our rivers. Of the 20 million morgen feet, we can, with all the methods available now and in the future, store at the utmost 10 million morgen feet in our dams for use when necessary. It is estimated that our population will double itself within the next thirty years. At the present rate of consumption we will then need 11 million morgen feet per year. That means that within thirty years we will have a yearly shortage of 1 million morgen feet. This is then the challenge — to change the estimated future water shortage despite rising costs into a surplus so that South Africa's economic growth will not be retarded. The best brains here and abroad are being employed to meet this challenge. A master water plan for the entire country is being drawn up at present. Numer­ous possibilities are being investigated — research on the purification and re-use of municipal and industrial effluent has already reached an advanced stage. The de-salting of sea water, coupled with the development of nuclear power stations, can become

a reality in the near future. The possibility of better and sensible utilisation of underground resources is being investigated. The evaporation of water in reservoirs can be limited. Ingenious methods of leading water from one catchment a r e a to another can be utilised. Despite the investigation of these and other possibilities, it is clear that water is not only the concern of the government scientists and other leaders. "Success will ultimately depend on how each individual uses water."

The Sugar Industry requires water for domestic, industrial and agricultural purposes. It is very for­tunate that, at the present time, it is in only limited competition for water from other users . Industrial expansion in Natal, however, will lead, to a growing demand for water. Good supplies of w a t e r are avail­able in the larger rivers such as t h e Umfolozi, Tugela, Umkomaas and the Umzimkulu, and we will see later that an increased use of water from these rivers will not seriously affect the Suga r Industry. On the other hand, industrial expansion on any of the smaller rivers, without the provision for storage, will be damaging to the Industry as surplus water is not available.

The growing demand for urban water supplies to satisfy the increasing number and size of towns and villages, including holiday resorts, scattered through­out the Sugar Industry, will be a growing threat to the traditional water supplies available to the Industry, particularly as these towns a n d villages look to the smaller rivers on which the Sugar Industry is entirely dependent to satisfy their growing demands. It is interesting to note that the North Coas t Regional Water Supply Corporation estimates t h a t within the foreseeable future they will require as much as 30 cusecs to satisfy their commitments between Durban and Tongaat. This water is not available without storage.

Of the total water used today, agriculture uses 82%. This high proportion is regarded with envy by industrial and domestic users. Agriculture will have to justify the use of this high proportion to an ever increasing extent in the future. It has a responsibility to utilise this water wi th a much greater efficiency than it does today b u t I, for one, cannot see the agricultural proportion decreasing to any extent if we are not only to satisfy people's thirst but also to feed them.

Agriculture has another responsibility in view of the fact that only 9% of the country's total rainfall finds its way into the rivers and streams and only A\% can be stored. Approximately 91 % is absorbed by the soil and is entirely available for crop and pastures. Agriculture's responsibility is to use this God-given water as effectively as possible and to pro­duce the maximum amount of food and essential raw products. Because the Sugar Industry in South Africa has developed in a marginal rainfall area, it has a great deal to teach agriculture generally about the efficient use of rainfall by well established prin­ciples such as deep land preparation, mulching and drought resistant varieties.

The water requirement of sugar c a n e is better known than for any other commercial c rop . Potential

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XIV Proceedings of The South African Sugar Technologists' Assocation — June 1970

evapotranspiration (Et) or the maximum water re­quirement of sugar cane has been measured accur­ately by means of Lysimeters in South Africa and in several overseas sugarcane growing countries. Repeated experiments on the North Coast have shown that Et can be reliably estimated in this area on the basis of the U.S.W.B. Class A pan evapora­tion using a I : 1 ratio. Further work has shown that the 1 : 1 ratio holds good for all practical pur­poses where sugar cane is grown. Mean daily esti­mates of water requirements for fully canopied cane can be calculated for each day, week or month of the year. It is therefore possible to get a reliable estimate of the water deficits for crop production in the various regions where cane is grown.

Field practice demands that a very thorough exploitation of available moisture in the surface strata of soil takes place before irrigation water is re­applied. It has been shown that this does not limit the transpiration from crops on deep sandy-textured soil but on heavier soils having low hydraulic con­ductivity, wilting may occur soon after irrigation during periods of high evaporative demand. Under these conditions, actual evapotranspiration will fall progressively below the potential level and the growth of the plant will suffer.

The average result of a large number of irriga­tion experiments in Natal indicate that approxi­mately one ton of cane is obtained per acre for each inch of irrigation applied. In 15 crops harvested over the past ten years, the application of 16" water per annum has resulted in the production of an addi­tional 15 tons cane per acre. In these experiments a wide range of ratios from 0.4 to 1.6 tons of cane per inch of water applied is not entirely unexpected. Good rainfall conditions tend to make irrigation water applications inefficient and result in low ratios being obtained. In contrast, dryland cane may suffer so severely in extremely dry years that the apparent response to irrigation becomes inflated due to mor­tality of stalks when no irrigation water is applied. This results in high ratios being obtained.

Water duty is defined as the area which is irrigated per cusec of water pumped or removed from the source at the time of peak water use by the crop. The South African Sugar Association Experiment Station provides an advisory service which recom­mends water duties on the basis of the method of irrigation to be used; the rainfall probabilities for the area concerned; the predicted E, for the area; the total available moisture holding capacity of the soil in the effective rooting depth; and the duration of daily irrigation operations.

Recommended water duties have varied from 70 acres per cusec in the Eastern Transvaal for furrow irrigation to 200 acres per cusec on the Natal Coast deep soil requiring supplementary irrigation by over­head sprinklers. Recent work, however, at the Pon-gola Research Station has shown that the most economical water duties by overhead sprinkler irrigation is far higher than was originally envisaged. There is no reason why this should not hold good for other crops and, if it is the case, it could make an important contribution to the more economical

use of water by agriculture. Supplementary irrigation is practised in areas

where the rainfall is between 35" and 45" per annum on about 53 000 acres, whilst full irrigation is applied in areas where the rainfall is less than 30" on about 74 000 acres, mainly in the Eastern Transvaal and Pongola. Data from the Sugar Industry Central Board's survey on cane production giving the areas under irrigation in each of the four main regions of the Sugar Industry is:

North and South Coasts 41,200 acres Zululand 24500 acres Northern N a t a l and Eastern

Transvaal (including the Nkwa-leni Valley) 62 000 acres

Natal Midlands 250 acres The scope for the future development in irrigation

will, in the main, depend on the availability of water. The supplementary and full irrigation of sugarcane can be economically viable in a large number of areas. In the case of the majority of sugar mills in the Industry, the area under cane can only decrease as a result of land being required for housing and industrial development, limited alter­native crop production and for a variety of other reasons. The loss of these cane supplies can only be made up by more intensive cultivation. Improved varieties and agronomic practices will, no doubt, result in improved yields, but again it must be stressed that water is the main limiting factor, and major increases in yield result from the application of irrigation water.

It has been conservatively estimated that if ade­quate water supplies were available, up to 50 000 acres could immediately be brought under econ­omical supplementary irrigation in Natal. This does not include major expansion of the area under full irrigation in Northern Natal and Pongola. This represents a minimum of 600 000 tons of cane to the Industry where management, transport and sugar factories already exist. In order to exploit this potential, water conservation is essential.

Water consumption by South African sugar fac­tories varies considerably from one mill to another depending on the design. At most factories, water consumption includes domestic water for the com­munity and, in some cases, this extends to a complete town with additional industry.

As far as water management is concerned, one can differentiate between three types of factories:

(a) complete recycling of cooling water, (b) partly recycling of cooling water, (c) no recycling of cooling water.-

If a factory operates with a complete recycling system of cooling water, more water is discharged by the mill than is taken in as a large amount of water enters with the cane. The amount of water present in cane is approximately 69%. Of this water, 15% remains in the bagasse and a negligible quantity leaves the mill in the form of molasses. So an amount of water equal to 54% of the amount of cane processed by a factory is evaporated and re­covered or discharged as condensate. For every 100 tons of cane per hour this amounts to 10 800 gallons

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-June 1970 Proceedings of The South African Sugar Technologists'" Association

per hour or \ cusec. In the case of part or no recycling factories, the

water discharged, which is the sum of the overflow cooling, boiler blow-off and blow-down and floor and tank washing, approximates to the total water re­quired to operate the factory less the domestic re­quirements. Sugar factories therefore quite inde­pendent of the degree of water recycling, consume only small quantities of water. The water discharged is either returned to its source or usefully used for irrigation.

The message from Water Year 1970, however, is that in the future all factories will be required to use water more effectively and, in the long run, complete recycling and the maximum re-use of water will be enforced.

The fact that nearly all sugar factories presently return water to rivers and streams is another import­ant factor in the efficient use of water. "We all know that there is no such thing as pollution of rivers and streams by factories."

The Sugar Industry has always been conscious of problems associated with and caused by river pol­lution. It has collaborated with the National Institute of Water Research Department of the C.S.I.R. in studying river pollution by sugar factories. Detailed microbiological and hydrological investigations are in progress on individual rivers with the full co-oper­ation of the South African Sugar Millers' Associa­tion, through its Sugar Milling Research Institute and also individual companies.

One of the express aims of Water Year 1970 is to focus attention on the pollution of water sources, and industrialists generally are going to have to face up to effluent problems or accept the severest action. The greatest pollution of rivers, however, is tragically from the country's greatest asset — soil. Taking into consideration Water Year, the new Soil Conservation Act and all the talk by organised (and disorganised) agriculture, I am convinced that in­sufficient work is being done to tackle this problem objectively. As somebody said at the Durban Water Symposium, the approach has been wrong in the past. Soil conservation has been promoted as a duty to make a future way of life possible. This is non­sense, as the blatant disregard for conserving land is a crime and should b.e punished as severely as the industrialist who allows effluent to pollute rivers and streams. More money will have to be spent and there will have to be greater co-operation between Agri­culture, the Department of Agricultural Technical Services, Water Affairs and Bantu Administration if pollution of rivers by soil is to be avoided.

Having discussed the use of water by the Sugar Industry, we will now turn our attention to the water supplies available to the Sugar Industry. We will see how limiting these supplies are in terms of the Mean Annual Run-off, Normal flows and Minimum low flows of rivers on which the Sugar Industry depends.

The rivers flowing through the Natal Sugar Industry excluding the Eastern Transvaal are the Pongola, Mkuze, Umsinduse and Umsinere, Hlu-hluwe and Ingweni, Umfolozi, Enselini, Nyalazi, Umhlatuzi. Amatikulu, Tugela, Sinkwazi and

Nonoti, Umvoti, Umhlali, Tongaat, Umhloti, Umhlanga, Umgeni, Umlaas, Illovo, Umkomaas, Ifafa, Umzumbe, Umtwalumi and Umpanbanyoni and the Umzimkulu.

The records of river flows in Natal are very limited and cover relatively short periods, thus only approxi­mate estimates can be made of their run-off poten­tials. It is estimated that the annual run-off of Natal rivers is between 8 000 000 and 10 000 000 acre ft. per annum, almost twice that of the Orange River. The mean total run-off pattern during the year has been estimated to vary from a maximum of approxi­mately 20 000 cusecs in December, January, Febru­ary and March, to a run-off of 3 000 to 7 000 cusecs in May, June, July, August and September.

The main areas of good run-off lie along the Drakensberg and, to a lesser extent, in the mist belt North and North-West of Pietermaritzburg. By far the most important river in the province is the Tugela which has an estimated mean annual run-off of approximately 3 600 000 acre ft. Other large rivers are the Umfolozi (M.A.R. 1 000 000 acre ft.), the Umzimkulu (M.A.R. 800 000 acre ft.), the Umkomaas (M.A.R. 800 000 acre ft.), the Umgeni (M.A.R. 600 000 acre ft.) and the Pongola (M.A.R. 700 000 acre ft.).

These six major rivers account for over 80% of the available water in Natal, and the remaining twenty or so rivers are all small with mean annual run-offs usually under 200 000 acre ft. The total discharge of the Natal rivers vary tremendously from year to year and also from month to month. It happens quite often that 50% or more of the annual discharge can occur within two months of the year.

The rivers of Natal can broadly be classified into those which can be utilised by the Sugar Industry and those which cannot.

The Tugela River passes through the cane belt in a very narrow gorge and not more than a dozen cane farms lie along its banks within easy pumping distance. Steep and high valley sides make pumping costly, and it is only a few miles from the mouth that the countryside becomes flatter. Except for industrial sites, this river can be of very little use to the Sugar Industry until such time as cheap hydro-electric power or even atomic power becomes available. The Tugela Basin development will place increasing demands on the flow of this river.

The Umzimkulu River also passes through the sugar growing areas in narrow and deep gorges and in a very narrow neck with only a few farms along its banks. A mill already exists at its mouth and the potential for irrigation is small.

The Umkomaas River, also on the South Coast, again has cut a deep narrow valley and is of little value to the Sugar Industry. It is already support­ing some industrial development.

The Umgeni River is heavily committed to supply­ing Durban and Pietermaritzburg and offers little further prospect for the Sugar Industry.

The Umfolozi River provides better prospects for irrigation. This river is noted for the amount of silt carried in times of flood. Dam sites exist but the silt load is such that dam construction could not

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XVI Proceedings of The South African Sugar Technologists' Association —June 1970

be undertaken until the catchment area, which lies mainly in Bantu Reserves, can be stabilised for conservation measures. Flooding and sand-silt deposition on the Umfolozi Flats is a serious prob­lem.

It is therefore a fact that Natal's five largest rivers are only of very limited use at the present time to the Sugar Industry, and these rivers account for approximately 75% of the available water in Natal.

The total annual flow of all the remaining rivers and streams is estimated to be less than 3 000 000 acre ft. per annum. The majority of these rivers have a mean annual run-off of less than 200 000 acre ft. per annum and run dry or have very low flows dur­ing the winter months or drought periods.

Estimations have shown that the Sugar Industry is entirely dependent on water which flows into the areas used for sugarcane cultivation as the mean annual run-off from areas actually under sugarcane falls far short of the Sugar Industry's requirements for industrial, urban and agricultural purposes. The Sugar Industry is therefore concerned with any de­velopment requiring water between the areas of sugarcane cultivation and the source of the rivers, as it will adversely affect the water resources of the Sugar Industry. Developments in the Bantu areas have a particular significance in this respect.

Attempts have been made to summarise the pre­sent and future use of water from the rivers serving the Sugar Industry in Natal. The mean annual run­off (M.A.R.) has been calculated from rainfall records and the nature and area of the catchment. The M.A.R. has been converted into an average flow and one-third M.A.R. has been taken as the run­off during a dry year and an estimated normal flow of the river. Where figures have been available, re­corded low flows have been considered.

In spite of the fact that the figures used are, at best, approximations due to paucity of factual data, a number of very important facts emerge which are vital to the Sugar Industry.

Practically all the rivers serving the Sugar Industry cannot meet the present and/or the anticipated future demand for water. An exception is the Umvoti River which still has potential for further irrigation of European, Bantu and Indian cane lands. All the water from this river should be reserved for the Sugar Industry.

The rivers which cannot satisfy the demand are the Mkuze, Hluhluwe, Nyalazi, Enseleni, Umhla-tuzi, Amatikulu, Sinkwazi, Nonoti, Umhlali, Ton­gaat, Umhloti, Umhlanga, Umlaas, Illovo Umzumbe and the Ifafa — a formidable list.

In all cases the recorded low flow falls below the present water requirements. In a large number of cases the estimated average low flows fall below the present water requirements and, in all cases, below the estimated future requirements.

In support of the figures referred to above, the growing number of petitions presented to the Depart­ment of Water Affairs to construct dams is testi­mony to the fact that rivers serving the Natal Sugar Industry cannot meet the present demand for water for increasing periods of every year.

A memorandum was presented to the Department of Water Affairs in August, 1966, by the North Coast Regional Water Supply Corporation, Timberit Wood-board Limited and The Tongaat Sugar Company Limited, which explained the fact that the river was no longer able to meet the present demand for water, and in view of projected development, particularly the development of Verulam as an Indian residential and industrial area, the construction of a dam was essential.

The flow of the Umhloti River has been gauged at Oakford Priory since 1953. At the present time, 36 cusecs is required at Oakford, and it has been estimated that 60 cusecs will be required by 1970. It is interesting to note that had assured draw-off been available then, in 1970, 45 cusecs would have been required.

Taking the period 1952/53 to 1964/65, the Umhloti • has failed to satisfy even the present demand for water during the six summer months, from September to April, in nine years out of the last twelve. The situation is much worse during winter. The need for a dam on the Umhloti River has been realised by the Department of Water Affairs, but there seems little likelihood of it being completed before 1975. Until this happens, there can be little, if any, Indian development in the Ottawa/Verulam complex.

Cane growers of the Amatikulu Mill Group made representation in 1965 in regard to a proposed dam on the Amatikulu River. Favourable reports of the dam site have been received and flow records are being kept.

It is understood that petitions on behalf of farmers in the Nkwaleni Valley have reached a stage where the Department of Water Affairs is actively studying the feasibility of constructing a dam. Specific farmers in the lower reaches have made representations regarding flooding and sand depositions on good agricultural land due to erosion and poor farming methods in the upper catchment of this river.

The Tongaat River provides water for industry, agriculture and the township of Tongaat. In order to secure these supplies, my own company has con­structed two private dams of over 700 000000 gallons total capacity on a tributary of the Tongaat River.

The Illovo River was the subject of a survey by the Town and Regional Planning Commission of Natal in 1960. Since this investigation, a growing demand for water, particularly by the Amanzimtoti township, has embarrassed the Illovo Sugar Com­pany which draws water for industrial and agricul­tural purposes.

A petition on behalf of farmers riparian to the Hluhluwe River led to the construction of a dam on the river in 1965. This is the only Government dam constructed within the Sugar Industry.

The Pongola Mill Group have repeatedly approached the Department of Water Affairs regard­ing the water shortage, particularly during spring and early summer, which has resulted in reduced crops. Notwithstanding the construction of the Josini

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— June 1970 XVH Proceedings of The South African Sugar Technologists' Association

Dam, they have asked for a dam to be constructed to ensure their own water supplies.

The present situation is highly unsatisfactory, and increasing attention must be paid to the growing water shortages on rivers serving the Sugar Industry.

What can be done to alleviate the situation? The majority of rivers serving the Sugar Industry

have good dam sites, although some of them are situated in the Bantu Reserves.

The Town and Regional Planning Commission have authorised two firms of consultants to investi­gate the possibilities of dam sites in Natal on the South Coast, the North Coast and Zululand. These reports cover preliminary investigations only, and possible sites have been selected by studying aerial photographs and contour maps, and only brief visits were made to many, but not necessarily all the sites. Further preliminary surveys will be required to examine these sites in more detail and calcula­tions made regarding the cost of construction and water charges. The dams which would probably receive priority are those which would benefit the widest cross-section of the community, i.e. the mul­tiple projects serving industry, municipalities and farming.

It appears that the silt load of Natal rivers is higher than the other provinces. The run-off from all the Natal rivers is about 25% of the country's total, but the amount of silt carried is 42%, thus the building of dams in this province is probably more complicated than in the others in that addi­tional provision must be made to by-pass silt-laden storm water, e.g. Nagle Dam, or considerable pro­portion of dams' storage capacity must be taken up in siltation.

Underground water resources are exercising the minds of hydrologists throughout the world to an increasing extent.

A number of factors influence the amount and availability of groundwater supplies from underly­ing rock formations. These include the amount of rainfall falling on an area, the topography and vege­tation of the area, the nature of the underlying rocks, structures in these rocks and the presence or other­wise of igneous intrusions within these rocks. It is generally agreed that the prospects for large under­ground water supplies in Natal is not as good as it is in other areas of South Africa. Nonetheless, in my opinion, the true potential of underground water resources should be investigated.

An additional source of water for the Sugar Industry which is not strictly true groundwater lies in the lower courses of all the rivers of the region. These rivers all contain alluvial infill of the order of 120 ft. deep at their mouths. It is even deeper in the case of the large rivers. The larger the river the further the alluvial infill extends inland but, in gen­eral, rock floors only appear in the river bed some three to four miles inland from the seas.

It should prove possible to sink wellpoints into this alluvial sand and abstract a considerable amount of water from it, for as is generally known, a very large percentage of total river flow can take place in its sandy bed. This aspect is being actively ex­

plored by one sugar company at the present time. Ladies and gentlemen — These are the facts. In

Water Year 1970, the rivers and streams on which the industry is dependent are already over-com­mitted. To date the Government has been persuaded to build only one dam which serves a limited num­ber of growers who are a considerable distance from their nearest mill.

If we superimpose on this, the fact that by the year 2000 South Africa's population will be between 30 000 000 and 40 000 000, also that we must anti­cipate a dramatic improvement in the standard of living of a larger proportion of our population. Again we expect Natal's industrial development to continue at a rate above the average for the whole of South Africa. There are schemes afoot to divert the flow of Natal rivers into the Transvaal (and if this is practical, why not the Umzimkulu to the Cape and/or Transkei!). I have stated that approximately 75% of Natal's water resources are of limited use to the Sugar Industry due to the situation of the main rivers.

Bearing all these facts in mind, can we imagine the industry's water resources in ten and twenty years' time — the situation is frightening beyond compre­hension. The water we extract from the cane will not even be our own if we do> not act now and act as an Industry, for there is a great deal to be done.

Since I became associated with Water Year 1970, I have had a growing conviction that this project must result in an industrial awakening to the paucity of its water supplies and a resolution to do something positive about them.

I believe one possible answer is to entrench in the Industry's organisation a Water Resources Board or Committee. Logically it could be under the direc­tion and guidance of one or more of the Industry's Technological Organisations. What would this com­mittee do? In my opinion, it would employ or retain experts to advise the Industry and its members on all matters relating to water resources. It would act as a watchdog jealously guarding the Industry's rightful water supplies. It would progressively study the rivers and streams on which the Industry depends and plan, in principle, to optimise these water resources to the benefit of the Industry. It would co-ordinate action by individual members of the Industry. It could advise on matters of conser­vation and pollution. Lastly, but not least, it would promote the importance of diminishing water resources relative to the growth of South Africa within the Industry itself.

Mr. J. B. Alexander, in reply to the President's address:

Mr. President, Dr. Dodds, Dr. Kuschke, Ladies and Gentlemen.

We have rather come to take for granted the eloquence and wisdom of our President's speeches. This morning's address was no exception for though most of us have recently been made well aware of the value of water and the ever increasing concern regarding its conservation within our country, I believe that nothing talks like the hard statistics which we have heard this morning. When I say

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XV111 Proceedings of The South African Sugar Technologists'' Association — June 1970

"hard" statistics it is perhaps debatable whether cer­tain of the statistics were not more vital than hard.

The stark facts should leave us all in no doubt that the proper use of water is not just the problem of the Karoo farmer, but a challenge to each and every one of us, whether we are large or small users of this valuable commodity. The findings of the Commission of Inquiry confirm the unique degree of partnership which exists in our Sugar Industry and if we are to remain a virile and competitive industry we must work together to find the most economic and equitable utilisation of the resource which you, Mr. President, so rightly highlight as the main limiting factor to our whole industry.

You have drawn attention to the fact that the old requirement of a sugar factory having to be situated on a river is unnecessary. The point has

been adequately demonstrated by several factories in Natal which have had to change to a system whereby the only make up water taken in by the factory is in the incoming cane.

The word "change" reminds me of resistance to change which you stressed in last year's address. I think that all of us must guard against the "R.C Factor" for it is highly likely that we will be faced with some degree of change in the near future as a result of the Commission of Inquiry into the Sugar Industry.

The sooner we can adjust to changed circum­stances the shorter will be the pain of change and the sooner will the attainable benefit be derived.

Mr. President, I am sure I speak on behalf of all those present when I express my thanks to you for a most thought provoking address.

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Proceedings of The South African Sugar Technologists'1 Association — June 1970 1

FORTY-FIFTH ANNUAL SUMMARY OF LABORATORY REPORTS OF SUGAR FACTORIES IN SOUTHERN AFRICA COVERING THE 1969 — 1970 SEASON

by CHARLES G. M. PERK

Sugar Milling Research Institute

Note: Except where otherwise stated, all data in this summary are as declared by the factories in their final laboratory reports.

INTRODUCTION

The final manufacturing results of the sugar factories reporting regularly to the Sugar Milling Research Institute have been compiled again in a number of tables which are to be found at the back of this summary. These tables contain the following data: •

Table A: Final Production of the S.A. Factories specified according to the grades of sugar made by each mill.

Table B: Tons of sugar made and tons of cane crushed, composition and varieties of cane crushed, rainfall, throughputs and time account; performances.

Table C: Sucrose balance, analysis of juices, syrup, filter cake and of final molasses.

Table D: Data regarding masses cuites and their exhaustions; consumption of clarifying agents and of additional fuels.

Table E: Comparative manufacturing results of recent years (S.A. Factories).

Table F: Average manufacturing results of S.A. factories by monthly periods for the 1969-1970 season.

Table G: Comparative data of S.A. factories from 1925 to 1969.

Note: We take this opportunity to draw special attention to the last two tables which give a comprehensive review of the last season and of the results from 1925 onwards.

In addition to these seven main tables, there are many

smaller tables in the text to illustrate the discussions of the different subjects.

METRICATION

At the request of the Metrication Committee, the present summary is still based on British Units. However, where Metric Units would have led to different figures, the latter are also shown.

To transfer the different weights, volumes and terms from British Units into Metric Units the following conversion factors were used:

MULTIPLY BY TO OBTAIN Tons of 2,000 lbs 0.907185 Metric Tons Cubic feet 0.02832 m3

Cu ft per short ton 0.031217 m3 per metric ton Lbs per cu ft 16.018 kgm"3

Btuperlb 2.3261 kJ kg-1

Lbs/hr/cu ft T.R.V. 16.018 kgh"1 m"3 T.R.V. Lbs/hr/sq ft E.D.A. 4.8824 kgtr1 mr2 E.D.A.

Note: T.R.V. stands for Total Roller Volume of the milling tandem(s). E.D.A. stands for Effective Drainage Area of the diffuser.

The Lower Calorific Value (or L.C.V.) of Bagasse:

British Units: 7 650—18S—86. 4W Btu/lb bagasse

Metric (SI) Units: 17 795-42S—201S kJkgr1

bagasse "S" stands for sucrose % bagasse "W" stands for moisture % bagasse

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2 Proceedings of The South African Sugar Technologists' Association — June 1970

SUGAR AND CANE PRODUCTIONS OF THE SOUTH AFRICAN SUGAR INDUSTRY IN RECENT YEARS

In the following two tables the official production figures of sugars and the tonnages of cane crushed in the last five seasons are compared.

TABLE 1 (British Units) Tons of 2,000 Lbs.

Season

1965/66 . 1966/67 . 1967/68 . 1968/69 . 1969/70.

Official Sugar

Tonnages

I 001 784 1 794 100 2 008 704 1 659 399 1 788 499

Tons Cane

Crushed

9 266 324 15 545 625 18 643 889 15 123 331 16 300 826

Cane to 96° Sugar

Ratio

8.97 8.43 9.03 8.91 8.87

TABLE 2 (Metric Units) Tons of 1 000 kg

Season

1965/66 . . 1966/67 . . 1967/68 . . 1968/69 . . 1969/70 . .

Official Sugar

Tonnages

908 803 1 627 581 1 822 266 1 505 381 1 622 499

Tons Cane

Crushed

8 406 269 14 102 756 16 913 471 13 719 657 14 787 865

Cane to 96° Sugar

Ratio

8.97 8.43 9.03 8.91 8.87

Note: As Sezela, Gledhow and Pongola do not publish the actual bagged tonnages of the sugars, but record only figures representing the sugars passing from the rawhouse to the refinery department of their factories, the official tonnages of sugars differ materially from the figures recorded in tables derived from the final laboratory reports. In the previous summary the latter figure was 5 500 tons or 3.3% more for the whole crop than the official tonnages of sugars made in the 1968/69 season. This year the total according to the laboratory reports is 5 224 tons or 2-9% more than the official sugar tonnage as recorded in tables 1, 2 and A. These discrepancies explain why the same cane to sugar ratios cannot be shown in all tables.

THE CANE CROPS OF THE 1969 SEASON

We will start with a comparison of the past season of the South African Sugar Industry with the 41 year average of previous seasons by monthly periods:

TABLE 3

Month

May . . . June . July . . • August . . September October . . November December January . .

Sucrose % Cane

1969/70

11.79 12.15

' 12.84 13.55 13.94 13.42 12.84 12.29 12.25

41 year averages

12.43 12.95 13.54 14.01 14.29 14.09 13.57 12.90 12.47

Mixed Juice Purity

1969/70

84.16 84.15 84.44 84.68 84.92 84.71 84.47 84.16 83.83

41 year averages

84.04 84.94 85.52 85.74 86.07 86.08 85.71 84.81 83.90

The comparison shows that the sucrose content of the cane stayed well below the 41 year average.

From a processing point of view the so much lower juice purities of the past season are a greater drawback than the lower sucrose content as the lower purities cause higher sucrose losses, higher heat consumption and reduction of boiling house capacity.

Another and better method of evaluating the quality of a cane crop is the comparison of the results of the Optimum Periods of the different cane crops, as seen in table 4.

TABLE 4

COMPARISON OF THE CANE HARVESTED DURING THE OPTIMUM PERIODS OVER THE

LAST TWENTY SEASONS

Season

1950 1951 1952 1953 1954 1955 1956 1957 1958 1959

Mean

1960 1961 1962 1963 1964 1965 1966 1967 1968 1969

Mean

Percent Cane

Sucrose

14.79 13.47 14.39 14.32 13.97 14.45 13.84 13.73 13.77 13.99

14.07

14.11 14.11 13.77 13.91 14.41 13.10 14.14 13.51 13.26 13.30

13.76

Fibre

15.99 16.36 15.98 16.31 15.96 15.60 15.70 15.24 15.73 15.76

15.86

15.16 14.46 15.32 15.38 15.20 15.44 14.76 14.78 15.28 14.90

15.07

Purity of Mixed Juice

86.69 84.94 86.71 86.07 86.42 86.39 86.19 85.86 85.10 86.06

86.04

86.10 86.69 83.51 86.09 86.01 84.53 86.65 83.74 83.63 84.63

85.16

Tons Cane/ Ton 96°

Sugar

7.70 8.62 7.94 8.04 8.31 7.91 8.27 8.32 8.32 8.21

8.16

8.16 7.99 8.33 8.15 7.85 8.82 8.11 8.59 8.70 8.51

8.32

Table 4 also shows how sucrose content of the cane and purity of the juice are so much lower in recent years than they were a decade before. As in the previous summary we raise the question again as to how far mechanical loading of cane has caused this decline in cane quality because of an increased delay between cutting and crushing of the cane.

Finally, in the following table the quality of the cane harvested in the Optimum Periods is compared with the cane crushed before July and after November, for the last five years.

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Proceedings of The South African Sugar Technologists' Association —

TABLE 5 CANE HARVESTED DURING THE OPTIMUM

PERIODS COMPARED WITH CANE CRUSHED BEFORE JULY AND AFTER NOVEMBER OF

THE LAST FIVE SEASONS

Season 1965/66 Optimum Period Balance of Crop

TOTAL CROP

Season 1966/67 Optimum Period Balance of Crop

TOTAL CROP

Season 1967/68 Optimum Period Balance of Crop

TOTAL CROP

Season 1968/69 Optimum Period Balance of Crop

TOTAL CROP

Season 1969/70 Optimum Period Balance of Crop

TOTAL CROP

/o Of

Crop

67 33

100

55 45

100

58 42

100

65 35

100

62 38

100

Percent Cane

Sucrose

13.10 12.76

12.99

14.14 13.20

13.72

13.51 12.21

12.92

13.26 12.81

13.11

13.30 12.19

12.88

Fibre

15.44 15.83

15.57

14.76 15.50

15.09

14.78 15.29

15 01

15.28 15.40

15.32

14.90 15.25

15.03

Purity Mixed Juice

84.53 83.50

84.22

85.65 84.29

85.06

83.74 82.92

83.41

83.63 83.41

83.60

84.63 83.53

84.25

Cane to 96° Sugar Ratio

8.83 9.26

8.97

8.11 8.78

8.40

8.59 9.57

9.03

8.70 9.33

8.91

8.51 9.49

8.86

In the following four tables the monthly figures of Mhlume, Ubombo Ranches, Luabo and Marromeu, for "Sucrose % Cane" and "Mixed Juice Purity" are compared with the five year averages of previous seasons:—

TABLE 6 MHLUME

Month

May . . . June July . . . August . . September October . . November December

Sucrose % Cane

1969

11.06 11.93 12.72 13.39 14.76 14.69 13.93 13.32

Mean

12.55 13.23 13.86 14.32 14.49 14.73 13.84 12.73

Mixed Juice Purity

1969

82.68 83.79 83.68 84.77 86.89 86.81 87.16 86.61

Mean

83.06 84.04 84.86 85.92 85.71 86.20 85.47 84.64

TABLE 7 UBOMBO RANCHES

Month

May . . June . . July . . . August . . September October . . November December

Sucrose % Cane

1969

10.00 11.23 12.13 13.39 14.59 13.61 13.03 12.43

Mean

12.02 12.28 12.78 13.66 14.14 14.00 13.36 12.93

Mixed Juice Purity

1969

77.04 80.39 80.33 84.03 85.68 85.49 85.53 84.22

Mean

81.35 81.79 82.35 83.24 84.52 84.18 83.99 83.37

TABLE 8 LUABO

Month

June . July . . . August September October . .

Sucrose % Cane

1969

12.43 13.07 13.45 13.77 13.60

Mean

12.61 13.30 14.17 14.60

(14.55)

Mixed Juice Purity

1969

85.01 87.30 87.66 88.88 86.55

Mean

84.40 85.99 87.36 87.49

(86.81)

TABLE 9 MARROMEU

Month

June July . . . August September October . . November

Sucrose % Cane

1969

13.16 13.94 13.38 14.71 15.57 13.91

Mean

12.20 13.24 14.30 15.33 15.98 15.62

Mixed Juice Purity

1969

82.10 82.80 82.61 85.12 86.07 83.62

Mean

82.30 83.23 85.36 86.64 86.27 85.67

Perusing these four tables, we see some really good figures such as 15.57 % sucrose in cane (October—Marro­meu); 88.88° purity mixed juice (September—Luabo); 87.16° mixed juice purity (November—Mhlume); . 14.76% sucrose in cane (September—Mhlume), etc.

THE CANE VARIETIES

In the following table, i.e. table 10, the percentages of the main cane varieties of Mhlume, Ubombo Ranches, Luabo, Marromeu and Nchalo are shown:

TABLE 10

Factory

N:Co.310 . N:Co.376 .

Mhlume

24.12 63.24

Ubombo Ranches 1 Luabo

19.67 67.62

28.50 58.50

Mar­romeu

28.57 61.30

Nchalo

69.20 29.88

With the exception of Nchalo, the main variety seems to be N:Co.376, as in South Africa.

In table 11, the change in the varietal scene of the South African cane belt is shown.

TABLE 11 PERCENTAGES OF THE MAIN CANE VARIETIES

CRUSHED IN RECENT SEASONS

Season

Co.331 . . N:Co.310 . N:Co.293 . N:Co.376 . N:Co.382 . N:50/211 .

1965/66

2.70 40.15 4.51

32.19 3.35 3.52

1966/67

1.83 33.63 5.98

36.45 4.89 3.56

1967/68

1.41 24.77 6.21

41.46 6.42 3.80

1968/69

1.30 19.21 7 .03

44.52 6.43 3 .08

1969/70

0.60 13.47 4.40

52.60 3.95 3.64

The replacement of N:Co.310 by N:Co.376 is slowing down, as a number of North Zululand growers do not join in this replacement.

As the Midland (Natal) factories plant from 3 to 7 % of the old-fashioned variety Co.331 we continue showing

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Proceedings of The South African Sugar Technologists' Association —June 1970

this variety in our tables, notwithstanding the fact that the average percentage of Co.331 is less than 1 %.

The distribution N :Co.293 seems to have reached its saturation point during the 1968/69 season and the same can be said about N:Co.382. The extension of N:50/211 seems to be stationary.

TIME ACCOUNT AND LENGTH OF THE S.A. CRUSH­ING SEASON

In 1969 the seven day week was introduced as a basis of the time account, replacing the six-day week as a basis. This was done to emphasise the time lost by weekend stops. Reducing the time wastefully spent for weekend stops will shorten the season, or when main­taining the length of the season it will make it possible to crush more cane with the same plant. In the following tabic, i.e. table 12, the hours available time and the length of the season in weeks as far as the two previous seasons are concerned, are more or less estimated as these figures were not recorded. From 1969/70 the hours available time, i.e. the calendar days of 24 hours which elapsed from the start of the season until the close have been recorded on the laboratory reports. Also recorded were the hours spent for weekend stops, the hours available time minus the hours of weekend stops giving the hours mill open. Table B at the back of the summary shows that the percentage of hours of weekend stops differs from factory to factory. Some factories stop 24 hours each week (with both tandems) because of week­ends, while another factory stops alternative weekends with one of the two milling trains for a period of 8 hours only. Returning to table 12, we repeat the warning that as available time and hours of weekend stops are roughly estimated as far as the previous seasons are concerned, this season's time account cannot be com­pared too closely with the accounts of the two previous seasons.

TABLE 12

Season

Tons cane crushed (BU) Tons cane crushed (M)

Hours available time . Hours mills open . Hours actual crushing.

Tons cane per hour (BU)

Tons cane per hour (M)

No. of mills crushing . Average lengths of

season: I n weeks . . . . In hours (available) . In hours mill open In hours crushing . .

Industrial averages of: Total hours of

stoppages . . . Weekend stops . . Stops for lack of cane Other hours of

stoppages . . .

1967/68

18 643 889 16 913 363

135 479 120 963 105 436

177 160

20

40 6 774 6 048 5 272

22.18% 10.71% 4.02%

7.45%

1968/69

15 123 331 13 719 657

114 244 102 003 87 905

172 156

20

34 5712 5 100 4 395

23.06% 10.71% 5.36%

6.99%

1969/70

16 300 826 14 787 864

120 577 105 438 92 572

176 160

20

36 6 029 5 272 4 629

23.23% 12.55% 5.16%

5.52%

REFRACTOMETRIC AND HYDR0METRIC DETERMIN­ATION OF BRIX

When a number of years ago the refractometer started to replace the hydrometer for determining the apparent dry matter of sugar solutions, it came quickly to the fore that the refracto brix could not entirely replace the spindle brix. We refer here to those cases where the specific gravity of the solution is involved, e.g. where volumes have to be converted into weights with the aid of the specific gravity of the solutions.

Three examples of this are: (a) when using the Schmitz table, because the function

of the brix here is to indicate the specific weight of the sugar solution;

(b) when converting cu ft or m3 of masses cuites into tons of masses cuites and

(c) when converting the weight of final molasses of a certain brix into tons of molasses of 85° brix.

Attention is drawn to the fact that in the event of the Schmitz table, the uncorrected brix should be used and in the case of conversion of volumes of masses cuite into weights, the brix should be corrected to the same temperature at which the volume of the masses cuite is determined, i.e. approximately 65°C.

'W" (Brixfree Water % Fibre in Final THE TERM Bagasse)

In table 13 the check figures called "W" are shown, but they do not give much cause for rejoicing. However, finding the reason for an abnormal figure for "W" can be tedious.

TABLE 13 COMPARISONS OF THE VALUE OF "W" OF

THE DIFFERENT FACTORIES FOR RECENT YEARS

Season

ML . . . PG UF EM FX EN AK DK GD DL GH MV JB UC TS ME IL RN SZ UK MH UR LB MR NH

1969

(18) 26 23

(11) 30

(45) 20 36 26 23 24 29 28

(30) 34 24 27 27 24 27 20 30

C c (32)

1968 J 1967

(neg.) 30 39

(12) 24

(43) 23 33 26 19 17 24 25

(29) 33 26 24 41 30 39 40 28

(9) 32 30

(13) 23

(45) 18 30 21 14 15 24 25

(25) 28 25 27 25 25 30 17 29

ane laundry ane laundry

(18) -

1966

32 23 25 21

(31) 16 26 21 17 15 23 27

(33) 27 16 25 21 24 18 25 27 35 — —

1965

29 25 27 20 46

8/24 29 26 21 21 22 — — 28 18 20 16 21 25 36 20 29 5

Note: The figures in brackets refer to factories where milling-cum-diffusion. is applied.

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- June 1970 Proceedings of The South African Sugar Technologists'" Association

A SET OF NEW PERFORMANCE INDICATORS

During the past season a set of new figures have been introduced which can be used to evaluate the perfor­mance of the factories. They are:

(i) Corrected Milling Loss, according to R. R. Follet-Smith (published in the May and August, 1969, issues of the International Sugar Journal).

(ii) Whole Reduced Extraction, according to Mittal , (Proc. 11th Congress ISSCT, 1962, pp. 1046-1151).

(iii) Reduced Boiling House Recovery, E.S.G. (See "System of Cane Sugar Factory Control" 2nd Ed., p. 35.)

(iv) Reduced Overall Recovery, E.S.G. (Loc. cit. p. 36).

The whole reduced extraction is found by subtracting "corrected milling loss" from 100.00%; the result being the extraction which would have been obtained if the sucrose and the fibre content of the cane both had been 131%.

The reduced boiling house recovery, E.S.G. estimates the boiling house recovery which would have been obtained if the purity of the mixed juice had been equal to 85° and the result expressed in the form of E.S.G. (Equivalent Standard Granulated is simply the crystal in the sugar calculated with the aid of the Winter Formula "S-0.4 (B.S.)").

Multiplying "Whole Reduced Extraction" with "Re­duced Boiling House Recovery, E.S.G." gives us "Reduced Overall Reduced Recovery, E.S.G." being the Overall Recovery in Crystal, when the sucrose content of the cane is 13 |%, the fibre content of the cane 1 3 | % and the purity of the mixed juice 85°.

By using this method to obtain more or.less com­parable figures for:

(a) extraction

(b) boiling house performance and

(c) the performance of the complete factory

table 14 reveals that the highest whole reduced extraction was obtained by Dalton UC, a factory equipped with a B.M.A. diffuser. Dalton UC is followed by Mount Edgecombe with its 21-roller tandem and lllovo with its 18-roller mill.

The highest reduced boiling house recovery E.S.G. was obtained by the modern plant of Amatikulu, closely followed by Felixton and Tongaat.

Thanks to the high extraction, Dalton UC is also first with respect to the performance of the whole factory as indicated by the whole reduced overall recovery E.S.G., closely followed by Tongaat and Amatikulu.

TABLE 14

WHOLE REDUCED EXTRACTION AND WHOLE REDUCED OVERALL RECOVERY, E.S.G.

Symbol of

Factory

ML PG UF EM FX EN AK DK GD DL GH MV JB UC TS ME IL RN SZ UK MH UR LB MR NH

Average .

Corrected Milling Loss

5.01 4.41 4.83 4.19 4.62 3.99 4.52 5.36 5.82 3.93 4.63 5.48 4.13 1.80 4.09 2.94 2.96 4.06 4.60 4.27 5.07 4.94 8.48 9.42 4.69

4.08

Whole Reduced

Extraction

94.99 95.66 95.17 95.81 95.38 96.01 95.48 94.64 94.05 96.07 95.37 94.52 95.87 98.20 95.90 97.06 97.04 95.74 95.40 95.73 94.93 95.06 91.52 90.58 95.31

95.92

Reduced Boiling House

Recovery, E.S.G.

85.04 89.88 89.71 88.06 90.15 85.81 90.35 88.54 89.38 89.22 89.28 89.30 87.33 88.16 90.25

87.58 87.96 87.92 88.08 88.93 88.69 87.87 87.79 84.70

85.99

Whole Reduced Overall

Recovery, E.S.G.

80.78 85.98 85.38 84.37 85.99 82.39 86.27 83.79 84.07 85.72 85.15 84.40 83.72 86.57 86.55

84.99 84.22 83.88 84.32 84.42 84.30 80.42 79.52 80.73

85.35

Comparing the figures of two neighbouring factories, i.e. Jaagbaan and Dalton UC, we see that Dalton UC obtained, owing to its diffusion plant, 2.33% more whole reduced extraction and as its reduced boiling house recovery, E.S.G., is also higher, i.e. 0.83% more, the reduced overall recovery E.S.G. is 2.85% higher than that of Jaagbaan.

The Swaziland factories Mhlume and Big Bend obtained similar figures for reduced overall recovery, E.S.G. because where one is lower in whole reduced extraction the other made up by its higher reduced boiling house recovery E.S.G.

We think that table 14 is a very interesting table which is worthwhile perusing.

THE RATIO BETWEEN THE WEIGHT OF N0NSUCR0SE IN TOTAL FINAL MOLASSES AND THE WEIGHT OF N0NSUCR0SE IN MIXED JUICES

Note I: The weight of nonsucrose is found by subtracting the weight of the sucrose from the weight of the brix in the material in question.

Note II: Total Final Molasses is the weighed final molasses plus the film of final molasses around the crystals of the weighed sugars.

Note III: The brix of the material in question can be determined with the aid of the specific gravity (spindle or hydro­meter brix), with the aid of the refractometric index (refracto brix) or by drying at 105°C (dry matter), as is the case with sugars.

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6 Proceedings of The South African Sugar Technologists'1 Association — June 1970

To add to the confusion we have the problem that the mixed juice of pure milling factories cannot truly be compared with the mixed juice of a milling-cum-diffusion factory. In the latter case approximately 40% of the mixed juice has passed some kind of juice clarifi­cation inside the diffuser. We have only to point to the fact that the percentage of filter cake discharged from a milling-cum-diffusion factory is only 3/5th of that of a pure milling factory.

It would therefore be a good idea to compare non-sucrose in total final molasses with nonsucrose in clarified juice. However, here again we have the difficulty that some factories use the refracto brix for the boiling house products, while most of the mills use the spindle brix throughout. If we want to compare the effect of diffusion on (he nonsucrose ratio we should divide the factories into four groups:

(a) pure milling and spindle brix

(b) pure milling and refracto brix

(c) diffusion and spindle brix

(d) diffusion and refracto brix

TABLE 15 NONSUCROSE RATIOS BASED ON CLARIFIED JUICE

(a)

PG 0.926

UF 0.924

DK 0.954

GD 0.901

GH 0.970

MV 0.996

JB 0.993

IL 0.982

RN 0.950

SZ 0.992

UK 0,996

UR 0.918

LB 0.829

MR 0.825

(b)

FX 0.839

AK 0.823

DL 0.833

ME H.T.M.

MH 0.826

TS 0.829

— — — _

— _ _ —

(c)

UC 0.940

EN 0.946

— — — — — — — — — — — —

(d)

ML 0.836

EM 0.887

NH 1.031

— — — — — — — — — — —

Table 15 gives us quite a different picture to that of the following table, i.e. table 16, where we tried to make the different factories comparable by converting the out­going nonsucrose of all factories to "spindle brix non­sucrose", like the nonsucrose in mixed juice of all factories.

TABLE 16

NONSUCROSE RATIOS OF MILLING FACTORIES COMPARED WITH THOSE OF MILLING-CUM-DIFFUSION

ONES ("BRIX" IN MIXED JUICE AND IN WEIGHED FINAL MOLASSES DETERMINED

WITH THE AID OF THE HYDROMETER)

Pure Milling Factories

Mill

PG UF FX AK DK GD DL GH MV JB TS IL RN SZ UK MH UR LB MR

Average

Ratio

0.82 0.85 0.79 0.82 0.90 0.86 0.84 0.84 0.89 0.87 0.85 0.87 0.82 0.92 0.88 0.85 0.85

• 0.92 0.74

0.85

Diffusion Factories

Mill

ML EM EN UC

Average

NH

Ratio

0.94 0.88 0.95 0.88

0.91

1.06

Note: The N.S. Ratio of Nchalo was not included into the average for diffusion factories because of doubt regarding its final molasses weight.

Table 16 gives us the impression that the diffusion factories produce more final molasses than com­mensurate with the purity of the mixed juice, but table 15 does not confirm this.

Although using clarified juice as a starting point makes the different factories better comparable, it still does not take into account something that might happen in the diffuser. In this respect using clarified juice as base is not any better than using mixed juice.

Of course we could also try to compare the differences in purities between first expressed juice and clarified juice in order to make out if diffusion leads to a greater portion of nonsucrose in the juice than in the event of pure milling. However here we will meet the difficulty that the drop in purity between first and last expressed juices depends on many factors, for example in the case of pure milling on the degree of cleanliness of the tandem. Further there is the effect of the degree of extraction on this drop. In addition the curve described by the drop in purity by increased pressure and extraction is not the same for every cane.

The staff of Dalton UC is convinced that the treatment of the press water, i.e. the method of clarification applied to the juice squeezed out by the dewatering mill(s), has a great effect. During the period that the press water was returned directly to the diffuser (by­passing the press water clarifier) the nonsucrose ratio

Page 22

Proceedings of The South African Sugar Technologists'' Association —June 1970 7

dropped materially. As a result of this test Dalton UC as well as Malelane will only screen their press waters in the 1970/71 season.

THE REDUCING SUGARS BALANCE

TABLE 17 REDUCING SUGARS BALANCE

Mill

ML PG UF EM FX EN AK DK GD DL GH MV JB UC TS ME IL RN SZ UK MH . . . . UR LB MR NH

Per 100 R.S. in mixed juice there is present in:

Clear Juice

104% 99%

103% 92% 90% 87% 94% 88%

114% 96% 63%

104% 98% 87% 88% 93% 97% 81% 88%

' 97% 87% 95%

100% 100% 90%

Syrup

105% 74%

106% 81% 86% 79% 87%

106% 81% 93% 61%

111% 100% 87% 83% 98% 67% 64% 75% 96% 55% 83% 87% 90% 80%

Total Final Molasses

148%

114% 107% 94%

108% 116% 116% 79%

106% 62%

115% 105% 80% 81%

H.T.M. 98% — 91% 84% — 95% 88%

142% 93%

It is usually understood that the percentage of R.S. in clarified juice should be slightly less than that in mixed juice as a result of the high pH directly after liming. The high temperature in the first effect causes the neutral pH point to move to a smaller pH which causes the H-ion concentration as well as the OH-ion concentration to increase, which means that, depending on the magnitude of the pH at 20°C, formation of R.S. by inversion as well as destruction of R.S. by OH-ion takes place. If the retention in the first effect is short and the pH at 20°C well above 7.00 the R.S. percentage in syrup should not differ much from the R.S. percentage in clear juice. Usually the percentage of R.S. in Total Final Molasses is again around 100%.

Some factories show percentages which vary materially from the standard values. This does not always mean that abnormal destruction of R.S. has taken place or that more than normal R.S. has been formed owing to inversion; it can be that the analysis has not been carried out exactly as it should be, i.e. the sample has not been correctly diluted.

Note: With regard to the change in H-ion and OH-ion con­centrations by higher temperatures see "Reduction of Retention Time of Juice at High Temperature" by C. G. M. Perk; Int. Sug. Jnl. 1966, 68, 361-363.

SUCROSE, BRIX, N0NSUCR0SE BALANCES. ETC.

TABLE 18 PARTS OF UNDETERMINED LOST SUCROSE,

BRIX AND NONSUCROSE PER 100 PARTS PRESENT IN CLARIFIED JUICE

Mill

ML* EM* FX* AK* DL* TS* MH* NH*

PG UF EN DK GD GH MV JB UC IL RN SZ UK UR LB MR

Sucrose

4.08% 2.70% 1.52% 1.23% 1.60% 0.40% 1.52% 2.10%

0.02% 0.74% 1.61% 1.64% 1.24% 0.44% 0.93% 2.97% 2.09% 2.58% 2.67% 0.11% 1.08% 1.87% 1.02% 2.49%

Brix

6.27% 4.09% 3.68% 3.50% 3.79% 2.83% 3.58%

-5 .07%

1.03% 1.87% 2.29% 2.03% 2.86% 0.70% 0.83% 2.62% 2.70% 2.55% 3.00% 0.20% 1.00% 2.89% 2.59% 4.78%

Non-Sucrose

16.27% 11.25% 16.14% 17.04% 16.67% 17.08% 17.60%

-16.06%

7.49% 7.75% 6.45% 4.61%

12.61% 2.98% 0.35% 0.70% 5.98% 2.36% 4.95%

- 0 . 7 8 % 0.39% 8.24%

12.26% 17.49%

Ratio

53.37° 55.17° 35.16° 30.17° 35.98° 12.13° 37.14°

Negative

1.74° 33.43° 60.87° 69.92° 37.12° 53.60° 94.54° 95.85° 65.10° 86.56° 76.74° 47.13° 95.35° 54.39° 34.01° 44.07°

• indicates that brix of the boiling house products is determined v«th the aid of the refractometer.

The undetermined sucrose, brix and nonsucrose losses together with the ratio between the tons unde­termined sucrose and brix losses are shown in table 18. We draw attention to the fact that as these balances are based on "clarified juice" the undetermined sucrose loss will differ from that shown in Table C as the latter is based on 100 sucrose in cane and the former on 100 sucrose in clarified juice.

Generally the undetermined sucrose loss should be approximately 1 % of the sucrose originally present in clarified juice and the ratio between tons undetermined lost sucrose and tons undetermined lost brix approxi­mately 80%.

THE QUANTITY (VOLUME) OF C-MASSECUITES

The quantity of C-m.c. to be boiled is related to the following items:

(1) the quantity of nonsucrose entering the factory with the mixed juice.

(2) the nonsucrose ratio (3) the purity of the C-m.c. and (4) the circulation ratio With regard to the nonsucrose ratio this figure indicates

nothing else than the ratio between the tonnage of non­sucrose in mixed juice to the tonnage of nonsucrose in final molasses and sugars. We are not allowed to speak of "recovered" nonsucrose in total final molasses for two reasons:

Page 23

Proceedings of The South African Sugar Technologists' Association — June 1970

Firstly, because the nonsucrose in mixed juice cannot be taken as "Input" as other nonsucrose substances (clarifying agents) are added, and moreover nonsucrose is formed during processing.

Secondly, the nonsucrose originally present in mixed juice is of a completely different composition to the nonsucrose present at the end of the manufacturing process.

In the following table (table 19) the cubic feet of C-m.c. per ton of nonsucrose in mixed juice of all factories are shown, together with the related factors (Nonsucrose Ratio, Circulation Ratio and Purity of the C-m.c.) in order to investigate a possible connection between the abovementioned four items.

TABLE 19

Mill

ML PG UF EM FX EN AK DK GD DL GH MV JB UC TS IL RN SZ UK UR MH LB MR NH

Cu ft of C-m.c. per ton

Non-Sucrose in Mixed Juice

60.19 cu ft/ton 56.31 cu ft/ton 51.91 cu ft/ton 64.28 cu ft/ton 48.49 cu ft/ton 63.06 cu ft/ton 50.52 cu ft/ton 64.75 cu ft/ton 50.24 cu ft/ton 52.62 cu ft/ton 61.74 cu ft/ton 53.74 cu ft/ton 62.27 cu ft/ton 55.37 cu ft/ton 55.56 cu ft/ton 60.80 cu ft/ton 52.32 cu ft/ton 67.59 cu ft/ton 55.61 cu ft/ton 63.53 cu ft/ton 67.00 cu ft/ton 79.35 cu ft/ton 63.76 cu ft/ton

Non-Sucrose Ratio

(Spindle)

0.864 0.818 0.849 0.884 0.794 0.948 0.819 0.899 0.834 0.839 0.838 0.891 0.870 0.880 0.851 0.971 0.823 0.923 0.884 0.847 0.853 0.916 0.740 1.060

Circu­lation Ratio

(Excess)

30% 25% 21% 22% 12% 26% 27% 32% 29% 23% 31% 21% 30% 21% 21% 24% 17% 15% 17% 32% 32% 63% 65%

Purity of

C-m.c.

R 57.99 S 60.79 S 57.09 R 59.50 R 60.04 S 58.77 R 59.87 S 60.06 S 54.26 R 59.49 S 60.60 S 56.00 S 60.70 S 57.78 R 58.29 S 61.38 S 59.88 S 59.66 S 59.78 S 61.60 R 62.84 S 59.50 S 60.50

Perusing Table 19 we see a number of factories showing a high cubic footage of C-m.c. per ton of NS in mixed juice, which large volumes cannot always be explained by the other items.

In connection with the relation between the nonsucrose circulation and the purity of the pre-cured C-sugar we reprint here the table which accompanied the Monthly Summary No. 4 of the 1969/70 season.

TABLE 20

PURITY OF THE SINGLE-CURED C-SUGAR ADJUSTED TO THE RECIRCULATION RATIO

Purity of C-m.c. . Final Molasses Purity

Recirculation Ratio (Minus 100)

10% 20% 30% 40% 50% 60% 70%

55° 35°

57*° 37i°

60° 40°

Purity of C-sugar

89 82 77| m 72 70i 68|

90 84 79* 76i 74 72i 71

901 85 81 78 76 74i 73

CONSUMPTION OF CLARIFYING AGENTS AND OF ADDITIONAL FUELS

Particulars about these two subjects can be found in the lower part of Table D at the end of the Summary.

Page 24

TABLE A

SOUTH AFRICAN SUGAR ASSOCIATION FINAL PRODUCTION 1969/70 SEASON

SHORT TONS

I &

MILL

LOCAL MARKET

White

Refinery

Raws Brown

EXPORT MARKET

High Pol

Very High Pol Adjusted to

Low Pol High Pol Low Pol

H.T.M.

(Sugar)

Equivalent)

TOTAL

I

Malelane.

Pongola .

Umfolozi . .

Empangeni .

Felixton .

Entumeni

Amatikulu .

Doornkop .

Glendale.

Darnall .

Gledhow.

Melville .

Jaagbaan

Union Co-op. .

Tongaat .

Mount Edgecombe

Illovo

Sezela

Renishaw

Umzimkulu .

TOTALS . .

107,827

44,255

11,318

116,018

81,037

68

42,209

109,324

69,427

17,174

105

23,305

21,056

248

18,634

8,519

254

100,038

20,701

83

42

10,159

8,626

38,953

8,290

240

1,198

3,659

17,832

95

76 312 83

2,740

— 71 548

2,498

7,410

50

33,926

80

— —

8,785

—

32,344

8,800

41,172

6,921

—

25,140

29,824

—

57,413

112

62,969

— 4,994

(Syrup) 177

38,197

— 78,083

47,303

91,568

35,412

75,619

17,141

21,123

35,397

4,483

267

271

4,433

2,755

1,588

324

658

7,790

933

698

9,962

593

601

9,852

6,121

3,528

721

1,461

17,310

2,073

1,551

63,544

116,453

83,208

121,032

109,564

103,829

24,649

182,031

42,533

23,381

131,003

151,289

39,560

65,932

23,679

188,655

86,743

48,061

122,332

33,994

90,571

360,523 441,278 126,687 394,931 323,563 24,200 53,773 63,544 1,788,499

Page 25

10 Proceedings of The South African Sugar Technologists' Association — June 1970

TABLE

SUGAR MADE AND CANE CRUSHED, CANE COMPOSITION AND VARIETIE:

(Season 1969 - 197(

SYMBOLS indicating factories: ML PG* UF EM FX EN AK DK GD DL GJ

Short Tons of Sugar Made . . . . 114127 (84,138) 120,673 109,716 103,825 24,625 181,800 42,533 23,424 130,867 (154,* Metric Tons of Sugar Made . . . . 103534 (76329) 109474 99533 94188 22339 164926 38585 21250 118721 (1401( Percentage of White Sugars made . . 92.42% 53.18% Nil Nil Nil 45.96% Nil Nil Nil Nil 76.74 Average "Pol of AH Sugars made . . 99.73° 98.77° 98.23° 98.78° 98.66° 99.26° 98.09° 97.85° 98.46° 98.08° 99.6

Short Tons of Cane Crushed . . . . 1,104,305 696,9581,098,3871,033,966 962,812 223,3081,590,788 378,198 211,764 1,138,712 1,423,« Metric Tons of Cane Crushed . . . . 1 001 809 632 270 996 440 937 998 873 448 202 582 1 443 139 343 094 192 109 1 033 022 1 2915

Season started on 30.4.69 21.5.69 23.6.69 1.6.69 17.5.69 2.6.69 8.5.69 29.5.69 6.6.69 15.5.69 9.6. Season completed at 4 .3 .70 10.1.70 8.1.70 15.2.70 11.2.70 4.1.70 12.2.70 7.2.70 18.2.70 14.2.70 21.3.

Per hour actual crushing: Short tons of cane crushed . Metric tons of cane crushed Short tons of fibre milled Metric tons of fibre milled . Short tons of brix processed Metric tons of brix processed Short tons of sugar bagged. Metric tons of sugar bagged

Time Account: Hours crushing % available hours Hours weekend stops % available hou Hours lack of cane % available hour Other hours of stoppages % avail, hours

Composition of Cane Crushed: Sucrose per cent cane . . . . Fibre per cent cane Tons cane per ton of sugar. . . . Tons cane per ton of 96° sugar . . Java Ratio

Cane Varieties Crushed: Co.331 N:Co.310 N:Co.293 N:Co.376 N:Co.382 N.50/211

Total Rainfall during 1969: Inches

Performances: Specific feed rate (Ib./h/c. ft) . . Specific feed rate (kg/h/ms t.r.v.) . Specific feed rate (lb./h/sq. ft) Specific feed rate (kg/h/m2 e.d.a.) Imbibition % cane Imbibition % fibre Lost absolute juice % fibre . . .

Boiling house recovery . . . . Overall recovery

215.01 195.05 29.53 26.79 32.38 29.38 22.22 20.16

69.33 r 7.05 i 9.29

14.34

13.11 13.64 9.68 9.31

91.16

Nil 32.80 0.20

56.29 1.32 Nil

9.39

9

?

— —

34 24 167

39.28 288

40.82 94.86 82.89 78.63

157.33 142.73 21.06 19.12 24.45 22.21

(18.99) (17.23)

79.87 15.47 1.02 3.64

13.81 13.39 (8.28) (7.95) 80.78

Nil 81.41 0.32

16.42 0.13 0.12 1.60

29.86 758

34.73 556 — —

37.17 278

35.18 95.76 90.16 86.34

260.76 236.56

35.78 32.46 38.36 34.80 28.65 25.99

88.88 2.36 2.77 6.00

12.84 13.72 9.10 8.90

78.85

Nil 77.84

Nil 8.71

10.87 1.47 1.11

32 88 835

35.58 570 — —

39.63 289

37.13 94.97 88.47 84.02

208.61 189.25 37.63 34.14 30.72 27.87 22.13 20 08

79.69 10.26 2.53 7.52

12.93 18.04 9.42 9.16

77.15

Nil 31.87 0 11

33.09 1.80 1.68

31.45

47.85 1216

— —

37 81 185

51.38 285

30.81 94.28 85.96 81.05

188.34 170.86 29.48 26.74 26.98 24.47 20.31 18.42

78.77 9.72 4.96 6.55

12.63 15.64

9.27 9 02

77.12

0 06 35.64 0 01

43.94 7.71 1.95

10 69

55 40 1407

41 86 671 — —

36.51 233

34.02 94.47 89.17 84.24

54.79 49.70

7.21 6.54 7.96 7.22 4.85 4.40

78.67 13.61 2.84 4.88

13.04 13.16 9.07 8.77

78.35

0.22 1.24

25.54 61.01 4.72 5.38

18.91

45.60 1158

— —

21 00 103

39.47 300

32.51 96.04 87.38 83.92

292.72 265.55

43.68 39.63 43.20 38.10 33.45 30.35

81.38 12.95

1.68 3.99

13.09 14.92

8.75 8.56

79.06

0 04 2.67 0.82

19.61 0.63 1.42

74.81.

36 83 935

45 08 722 — —

43 99 295

32.14 94.93 90.24 85.67

79.50 72.12 12.54 11.38 11.28 10.23 8.94 8 11

78.55 15.47 3.70 2.27

12.99 14.80

8.89 8.72

77.14

0.41 2.92 7.54

73.52 9.60 2.24 3.77

39 84 1194

57.61 923 — —

32.95 223

42.65 94.07 90.08 84.69

48.06 43.60

7.11 6.45 6.83 6.20 5.32 4 82

71.77 15.44 9.84 2.94

12.97 14.80 9.04 8.81

79.69

4.33 11.40 2.50

58.70 1.72 2 45

18.90

33 22 844

57 68 924 — —

38.32 259

43.97 93.26 89.93 83.96

208.56 189.20 30.22 27.42 31.12 28.23 23.97 21.74

82.68 10.74 4.66 1.92

13.17 14.49 8.70 8.52

79.60

0.63 3.59 0.17

80.11 0.27 3.75

11.48

42 27 1074

49 86 799 — —

53.34 368

30.86 95.74 89.37 85.56

253. 230. 40. 36. 36. 32. 27. 24.

82. 10.

1. 5.

12. 15. (9.: (8.! 78

n ? 0

69 3 5.

18

37 <

53 i

37 •

40 93 89 83

The sugar tonnages of these three factories do not reflect the actually produced quantities of sugar. Like the other boiling house data they refer solely to processing in the rawhouse department and not to the whole factory.

X

Page 26

Proceedings of The South African Sugar Technologists' Association — June 1970 11

HROUGHPUTS AND TIME ACCOUNTS, PERFORMANCES

MV JB UC TS ME IL RN SZ* UK

39,546 65,895 23,734 188,806 (86,744) 48,059 33,994 (124,551) 90,577 35 875 59 779 21531 171282 (78 693) 43 598 30 839 (112 991) 82 170

Nil Nil Nil Nil Nil Nil Nil 66% Nil 98.06° 98.56° 97.88° 98.42° H.T.M. 97.85° 98.63° 99.64° 98.73°

155,048 631,073 220,852 1,748,628 807,958 443,048 327,818(1,116,090) 787,459 (22 094 572 500 200 354 1 586 329 732 967 401 926 297 392(1 012 500) 714 371

4.5.69 17.5.69 19.5.69 6.6.69 28.5.69 8.5.69 19.6.69 16.6.69 14.6.69 9.1.70 6.12.69 20.12.69 23.2.70 14.1.70 11.1.70 26.2.70 28.2.70 11.2.70

79.48 192.39 57.69 315.87 185.47 103.19 78.65 251.53 171.46 72.11 174.53 52.34 286.55 168.27 93.61 71.35 228.18 155.55 12.00 27.85 8.66 49.60 28.30 15.17 12.26 37.92 24.54 10.89 25.26 7.85 45.00 25.68 13.76 11.12 34.40 22.26 11.27 27.98 8.34 43.77 26.46 14.96 10.91 36.55 24.82 10.22 25.39 7.57 39.71 24.01 13.57 9.90 33.15 22.51 8.85 20.09 6.20 34.10 H.T.M. 11.19 8.16 28 07 19.72 8.03 18.22 5.62 30 94 H.T.M. 10.15 7.40 25.46 17.89

71.68 68.09 73.82 79.17 78.32 72.68 68.89 72.79 78.84 16.09 13.18 14.95 9.76 15.64 17.25 15.62 12.20 14.19 6.12 9.42 4.19 4.39 4.59 8.34 8.96 7.43 4.39 6.11 9.31 7.04 6.68 1.45 1.72 6.53 7.58 2.56

12.92 12.62 12.31 12.36 12.35 12.72 12.31 13.14 13.19 15.10 14.48 15.01 15.70 15 26 14.70 15.59 15 08 14.31

. 8.98 9.58 9.31 9.26 H.T.M. 9.22 9.64 (8.96) 8.69 8.79 9.33 9.13 9.03 H.T.M. 9.04 9.39 (8 69) 8.45

78.26 80.59 78.55 77.16 78.60 78.49 78.15 78.52 79.64

0.65 6.95 3.07 0.23 1.02 1.20 Nil 0.13 0.31 3.37 2.28 0.47 5.01 3.44 3.53 3.53 2.10 5.63 0.01 51.01 63.39 1.05 6.15 Nil Nil 0.07 2.14

47.78 15.97 7.09 53.13 44.07 78.26 78.26 81.15 90.25 1.37 22.07 24.56 5.56 1.95 10 68 10.80 3.14 0.28 3.45 0.40 1.08 12.21 7.90 2.13 6.78 0.95 0.51

43.37 1.32 0.34 22.81 35.47 4 20 0.63 12.46 0.88

48.29 30.21 37.15 44.88 51.02 46 40 46.85 47 85 45.75 1227 767 944 1140 1296 1179 1190 1215 1162

43.63 38.71 — 53.61 47.05 37.32 48.35 75.10 64.32 699 620 — 859 754 598 774 1203 1030 — — 33.40 _ _ _ _ _ _

45.68 38.28 35.31 34.32 50.54 39.10 35.59 44 85 36.48 302 264 235 219 331 266 228 297 255

41.15 34.31 15.83 30.76 25.40 33.25 34.56 35.52 35 08 93.74 95.42 97.91 95.02 96.53 95.66 94.86 94.79 95 42 90.19 84.45 87.25 90.50 — 87.21 87.57 88.88 90.21 84.54 81.54 85.43 85.99 — 83.43 83.07 84.25 86.08

Totals and

Means

(1,792,077) (1,625,745)

20% 98.68°

16,300,826 14 787 865

30.4.69 21.3.70

176.05 159.70 26.46 24.00 25.57 23.20 19.35 17.56

76.77 12.55 5.16 5.52

12.88 15.03 (9.10) (8.86) 78.78

0.60 13.47 4.40

52.60 3.95 3.64

21.34

41.54 1055

41.22 274

34.15 94.98 88.58 84.13

MH UR LB MR NH

87,829 84,808 78,181 74,587 29,640 79 677 76937 70 925 67 664 26 889 2.17% 21.40% 55.40% 64 48% 37.14% 98.56° 98.72° 98.93° 99.17° 97.58°

761,694 803,176 725,693 691,600 266,106 690 997 728 629 658 344 627 410 241407

19.5.69 2.5.69 5.5.69 5.5.69 24.4.69 19.1.70 1.1.70 4.11.69 21.12.69 24.11.69

164.16 161.31 204.93 151.12 70.40 148.92 146.24 185.91 137.09 63.87 23.44 21.33 28.16 22.33 9.85 21.26 19.35 25.55 20.26 8.94 24.28 23.19 28.11 22.42 10.65 22.03 21.04 25.50 20.34 9.66 18.93 17.02 22.08 16.30 7.84 17.17 15.44 20.03 14.78 7.11

78.89 85.01 80.67 82.94 74.26 6.67 7.55 9.11 9.25 12.53

10.53 4.90 5.55 3.11 0.95 3.91 2.54 4.68 4.64 12.26

13.37 12.55 13 03 13.78 13.46 14.28 13.22 13.74 14.78 14.00 8.67 9.48 9.28 9.17 8.98 8.45 9.16 9.01 8.87 8.83

81.17 80.65 Cane Laundries 80.50

Nil Nil Nil Nil Nil 34.12 19.67 28.50 28.57 69.20

Nil Nil Nil 0.21 Nil 63.24 67.62 58.50 61.30 29.88 0.14 Nil 9.70 8.99 Nil

Nil 3.54 Nil Nil Nil 2.50 9.17 3.30 0.93 0.92

33.36 23.73 47.46 41.13 ? 847 603 1205 1044 ?

66.96 65.97 73.81 70.22 — 1073 972 1182 1125 —

_ _ _ _ 30.98 — — — — 151

27.92 28.04 27.52 28 48 42.03 196 212 200 193 300

36 44 37.18 61.76 63.39 32.46 94 62 94.98 91.21 89.79 95.14 89.81 87.38 89.71 86.64 84.85 84.98 82.99 81.83 77.98 80.73

Page 27

12 Proceedings of The South African Sugar Technologists'1 Association — June 1970

TABLE I

SUCROSE BALANCE, ANALYSIS OF BAGASSE, JUICE*

(Season 1969 - 197C

FACTORY SYMBOL: ML

Sucrose Balance: Lost in Bagasse (a) Lost in Filter Cake (b). . . . Lost in Final Molasses (c). . . Undetermined Sucrose Losses (d) . Boiling House Losses (b)-\-(c)+(d) Sum of All Losses (a )+(6)+(c)+(a

Final Bagasse:

Moisture % Bagasse . . . .

Bagasse % Cane L.C.V. in btu per lb. Bagasse . L.C.V. in kJ per kg Bagasse . . Brixfree Water % Fibre . . .

First Expressed Juice:

Degrees (Apparent) Purity. .

Last Expressed Juice: Degrees Brix Degrees (Apparent) Purity. . . Purity Drop

Mixed Juice:

Degrees (Apparent) Purity. .

Degrees Gravity Purity Reducing Sugars/Sucrose Ratio .

Clarified Juice: Degrees Brix Degrees (Apparent) Purity. . Reducing Sugars/Sucrose Ratio . Average pH

Filter Cake: Sucrose % Filter Cake. . . Filter Cake % Cane . . . .

Syrup: Degrees Brix Degrees (Apparent) Purity. . . Reducing Sugars/Sucrose Ratio . Average pH

Final Molasses: Spindle Brix (undiluted) Refracto Brix (undiluted) . . . Pol/Spindle Brix Purity. . . . Sucrose/Spindle Brix Purity . Pol/Refracto Brix Purity . Sucrose Refracto Brix Purity . Percentage Reducing Sugars . Percentage Sulphated Ash. Reducing Sugars/Ash Quotient . Molasses of 85° Spindle Brix % Ca

5.14 0.44

11.93 3.86

16.23 ). 21.37

2.09 54.56 42.23 32.29 2898 6741

18

19.20 84.12

3.08 65.10 19.02

14.08 —

1.56 82.56 6.10

13.09 82.03

6.39 7.25

1.76 3.30

60.97 82.40

6.43 6.26

— 84.91

— —

37.47 41.02 18.45 11-38

1.62 ne 4.72

P C

4.26 1.06 8.33 0.03 9.41

13.67

2.01 51.28 45.80 29.23 3183 7404

26

19.74 86.63

2.55 69.41 17.22

14.42 85.02

1.61 84.95 3.18

14.09 86.37

3.18 7.18

2.47 5.92

64.19 85.73 2.39 6.59

93.22 —

38.98 — — — —

— 3.47

UF

5.03 0.76 9.49 0.70

10.95 15.98

1.99 54.84 42.31 32.43 2876 6690

33

19.12 85.16

1.95 70.25 14.91

13.72 82.92 2.24

— 3.59

13.22 83.97

3.73 7.07

1.96 5.00

62.59 83.95

3.83 6.39

94.06 —

38.95 38.04

— —

10.25 15.25 0.67 3.77

EM

5.72 0.19

10.69 2.35

13.23 18.95

1.77 54.32 43.12 41.85

2925 6803

11

19.77 84.77

3.58 69.09 15.68

13.45 —

1.97 82.80 4.11

13.20 83.69

3.80 7.30

0.79 3.17

61.80 84.65

3.32 6.50

— 89.32

— —

40.81 40.65 13.59 13.21

1.03 4.00

FX

5.53 0.76 8.04 1.43

10.23 15.76

1 99 52.70 44.55 35.10 3061 7120

30

19.21 85.22

2.42 72.41 12.81

14.13 —

1.93 83.29 4.49

12.71 85.22

4.06 7.30

1.60 6 00

61.56 85.90

3.87 6.30

— 89.17

— — —

38.68 15.80 16.14 0.98 3.29

EN

3.96 0.80 9.78 1.54

12.12 16.08

1.60 56.75 40.91 32.16 2718 6322

45

18 87 88.23

1.28 69.55 18.68

13.53 —

1.97 86.26 2.51

13 02 86.14 2 20 7.47

2 09 5.00

61.83 85.96

2.00 7.01

91.08 —

42.11 40.36

— — —

13.01 —

3.63

AK

5.06 0.57 7.53 1.17 9.27

14.33

1.94 53.69 43.73 34.13 2926 6807

20

19.05 86.87

1 81 75.38 11.49

12.77 —

2.70 84 17 3.59

12.52 85.66

3.38 7.46

1 50 5 03

59.76 86.52

3.16 6.66

— 89.04

— —

36.71 38.81 16.27 13.79

1.18 3.22

DK

5.99 0.62 6.97 1.73 9.32

15.31

2.27 53.51 43.18 34.27 2986 6945

36

19.20 87.73

3.39 69.92 18.81

14.38 86.03

1.70 86.10 2.99

13.87 86.72 2.26 7.40

1.61 5.00

58.81 86.60

3.20 6.50

92.40 —

36.81 39.04

— —

13.15 — —

2.98

GD

6.64 0.27 8.24 1.06 9.30

16.04

2.58 52.03 44.44 33.30 3108 7230

26

18.91 86.69

3.04 73.02 13.67

13.54 85.18

1.51 —

4.61

13.48 85.72 4.87 7.08

1.16 3.00

61.33 86.11 4.07 6.62

94.18 —

36.91 38.91

— —

15.18 15.70 0.97 3.24

DL

4.26 0.49 8.16-1.53

10.18 14.44

1.75 52.33 45.11 32.12 3097 7204

23

19.15 86.44

1.82 68.40 18.04

12.31 —

1.92 84.52 3.63

11.63 85.45

3.49 7.40

1.31 4.95

62.51 85.70

3.37 6.60

— 85.72

— — —

40.14 13.67 14.98 0.92 3.34

&

6. 0.! 9.:

o.< 15.' 21.!

2.: 53.i 43.: 36.' 291 69;

19.: 85.1

2.1 67.. 18..

14.1

1.: 84 J 5.:

13.. 86-

3.: 7..

1. 4.

60. 86.

3.

87.

39.

10.

3.

L.C.V. (Bagasse: British Units) = 7650 - 18S - 86.4M btu per lb. Bagasse. Lower Calorific Value (metric units) 17 795 — 42S — 201M kJ per kg. S stands for Pol % Bagasse; M indicates moisture % Bagasse.

Page 28

Proceedings of The South African Sugar Technologists' Association —June 1970 13

FILTER CAKE, SYRUP AND FINAL MOLASSES

MV JB UC TS ME IL RN SZ* UK

6.26 4.58 2.10 4.98 3.47 4.34 5.14 5.21 4.58 0.70 0.64 0.32 0.46 0.43 0.41 0.56 0.55 0.47 7.63 10.48 10.12 8.18 — 9.28 8.70 9.89 7.84 0.87 2.76 2.04 0.39 — 2.54 2.52 0.10 1.03 9.20 13.88 12.48 9.03 — 12.23 11.79 10.54 9.34

15.46 18.46 14.58 14.01 — 17.02 16.93 15.75 13.92

2.38 1.72 0.85 1.75 1.31 1.65 1.79 2.01 1.84 52.34 54.39 49.35 52.95 51.25 53.58 53.13 52.86 53.61 44.37 42.95 49.27 44.66 46.67 43.87 44.19 44.27 43.64 34.03 33.70 30.46 35.16 32.70 33.50 35.06 34.06 32.79 3085 2919 3371 3044 3198 2991 3027 3047 2985 7176 6790 7841 7080 7440 6957 7042 7087 6943

29 22 30 34 24 27 27 24 27

19.00 18.77 18.48 18.62 18.43 18.86 18.46 19.06 18.78 86.90 83.40 84.82 86.00 85.23 85.95 85.31 87.78 88.22

2.19 1.88 3.82 2.42. 1.44 2.12 2.91 2.19 1.90 72.30 63.80 62.47 73.07 62.96 64.62 70.44 69.90 67.44 14.60 19.60 22.35 12.93 22.27 21.33 14.87 17.88 20.78

12.70 13.91 13.79 13.98 12.11 13.72 13.83 13.11 13.96 — — 83.39 — — 83.53 84.16 85.74 86.82

1.48 0.60 1.44 1.26 1.67 2.42 1.15 2.04 1.40 85.42 82.80 83.44 84.74 83.56 84.00 — — 86.97 3.30 5.83 5.06 5.22 5.06 4.76 3.27 3.78 3.36

11.87 12.93 14.05 13.87 11.36 13.21 15.15 12.51 13.22 86.67 84.50 84.24 85.44 84.72 85.47 85.94 86.50 88.20 3.46 5.75 4.41 4.60 4.75 4.65 2.67 3.36 3.26 7.20 7.50 7.20 7.27 7.33 7.43 7.00 7.60 7.60

1.80 1.76 1.05 1.70 0.90 1.46 1.63 1.33 1.59 5.00 4.54 3.79 3.36 5.92 3.54 4.27 5.42 4.00

59.99 62.50 60.90 64.30 56.70 62.64 55.81 61.93 59.64 86.14 83.70 84.04 85.48 85.17 84.88 85.22 86.84 87.58 3.68 5.68 4.40 4.36 4.98 3.21 2.10 2.87 3.23 6.80 6.80 6.30 6.52 6.39 6.74 6.80 6.60 7.20

92.50 90.76 92.62 — — 91.38 92.68 90.86 85.41 — — — 84.30 86.67 — — — —

36.86 — 39.06 — — 36.97 38.74 40.83 38.09 37.03 38.93 39.33 — — 39.10 — 41.43 39.80

— — — 39.10 40.84 — — — — — — — 39.97 42.67 — — — —

14.75 17.61 13.95 15.94 14.24 15.17 — 12.25 10.99 — 13.32 11.34 14.14 14.73 11.50 — 13.74 — — 1.32 1.23 1.13 0.97 1.32 — 0.89 —

3.13 3.98 3.75 3.15 — 3.55 3.25 3.60 3.06

Averages

5.02 0.55 9.01 1.29

10.85 15.87

1.89 53.30 43.97 34.18 3011 7005

(27)

19.00 86.06

2.42 68.78 17.28

13.57

1.81 84.25 4.17

13.12 85.45 3.91 7.32

1.58 4.49

61.03 85.45 3.68

91.37

38.43

14.18 13.79 1.05 3.55

MH UR LB MR NH

5.38 5.02 8.79 10.21 4.86 0.30 0.23 0.40 0.97 0.84 7.90 9.99 8.06 8.98 11.54 1.44 1.77 0.92 1.86 2.03 9.64 11.99 9.38 11.81 14.41

15.02 17.01 18.17 22.02 19.27

2.30 2.09 3.40 4.04 1.88 51.37 53.34 54.68 52.26 57.40 45.55 43.80 40.86 42.46 40.18 30.68 30.19 33.63 34.81 34.83 3170 3004 2864 3062 2658 7375 6987 6663 7123 6182

20 30 C.L. C.L. 26

19.01 18.40 C.L. CX. 19.40 86.68 84.59 87.15 85.10 86.19

2.67 1.98 3.96 7.20 3.18 75.31 73.16 76.49 76.20 77.67 11.37 11.43 10.66 8.90 8.52

15.31 14.69 14.61 15.84 14.11 85.56 82.60 85.47 — 84.12 1.12 1.99 1.68 1.72 2.07

— 82.94 86.64 83.38 84.67 3.41 5.60 4.66 3.64 4.18

15.17 14.30 15.10 15.50 14.15 87.22 84.00 86.09 84.70 85.37 2.99 5.34 4.69 3.67 3.79

? 7.20 7.10 6.70 7.60

1.62 0.71 1.36 2.85 2.64 2.45 4.02 3.83 4.51 4.27

64.21 62.30 63.80 62.20 56.07 87.07 83.90 85.60 84.60 85.20 3.24 4.68 4.07 3.33 3.37

? 6.70 6.80 6.70 7.20

— 90.76 90.09 91.50 — 89.75 — — — 81.27

— 37.59 38.33 39.48 — — 38.87 39.86 41.46 —

40.91 — — — 41.43 — — — — 43.01 — 16.52 15.91 19.36 10.28 — 14.13 13.07 15.24 — — 1.17 1.22 1.27. —

3.24 3.80 3.10 3.51 4.53

Page 29

14 Proceedings of The South African Sugar Technologists'' Association — June 1970

TABLE D

DATA REGARDING: MASSECUITES, EXHAUSTIONS, CONSUMPTION OF

(Season 1969 - 70)

SYMBOLS OF FACTORIES

Brix in Mixed Juice % Cane. .

A-Massecuite: Cu. ft. per short ton Brix* hi per metric ton Brix* . . Brix of massecuite Purity of massecuite . . Purity of A-molasses . . . Purity Drop Exhaustion

Purity A-m.c.—Purity Syrup. .

B-Massecuite Cu. ft. per short ton Brix* hi per metric ton Brix* . . Brix o f massecuite . . . . Purity of massecuite . . . Purity of B-molasses . Purity Drop Exhaustion

C-Massecuite Cu. ft. per short ton Brix* hi per metric ton Brix* . . Brix o f massecuite . . . . Purity of massecuite Purity of C-molasses . Purity Drop

Exhaustion

White Sugar Massecuites : Lb. sugar per cu. ft. m.c.'s Kg. sugar per hi m.c.'s. . .

Total Volume of all m.c.'s: Cu. ft. per short ton Brix* hi per metric ton Brix* . .

Clarifying Agents: Per 1000 tons of Cane

Tons Coke Tons Lime Tons Sulphur . . . .

p.p.m. Mixed Juice Phosphoric Flocculants

Additional Fuels: Per 1000 Tons of Cane

Tons o f Fuel Oil . . . Tons of Coal Tons o f Wood . . . . Converted into tons Bagasse

ML

15.06

41.29 12.85 92.24 83.22 68.11 15.11 56.93

0.79

13.82 4.30 93.82 70.73 47.28 23.45 62.89

10.50 3.27

95.67 57.99 37.47 20.52 31.40 56.59

33.66 53.92

. 104.13 32.41

9 9 t

•> 9 9

9 9 9 9

PG

15 56

27.88 8.70

90.70 86.69 72.26 14.43 60.00

0.96

12.41 3.87

93.41 76.53 58.17 18.36 57.35

8.45 2.64

97.94 60.79 38.98 21.81 35.01 58.80

41.60 66.64

68.36 21.34

5.165 0.521 0.604 0.014

Nil 0.665

Nil 6.263

— 25.05

UF

14.71

t30.56 9.54

93.50 87.86 71.16 16.70 65.90

3.91

10.25 3.20

95.17 71.14 51.33 19.81 57.21

8.87 2.77

98.01 57.09 38.95 18.14 29.12 52.05

— —

49.68 15.51

— —

0.512 —

Nil 0.330

Nil 2.638 0.377 11.00

EM

14.73

28 43 8 88

93.20 86.10 68.50 17.60 64 89

1.45

9.85 3.07

94.90 70.40 49.70 20.70 58.46

11.06 3.45

97.10 59.50 40.81 18.69 30.66 53.07

— —

49.34 15.40

— —

0.635 —

Nil Nil

Nil 0.976 4.041

8.75

FX

14.32

28.54 8 91

92.84 87.21 69.67 17.54 66.31

1.31

8.27 2.58

93.86 71.55 49.53 22.02 60.98

8.10 2.53

96.24 60.04 38.38 21.66 33.83 58.54

— —

44.91 14.02

— —

0.580 —

Nil Nil

Nil 12.203

Nil 48.81*

EN

14.52

23.24 7.25

92.47 85.81 69.99 15.82 61.43

- 0 . 1 5

14.21 4.44

96.29 71.01 51.77 19.24 56.18

8.66 2.70

98.87 58.77 42.11 16.66 28.45 48.97

9 9

9 9

— —

1.881 0.837

— 0.668

Nil 5.150 5.374 27.05

AK

14.76

29.31 9.15

93.73 89.90 70.10 19.80 73.66

3.38

9.16 2.86

93.81 72.34 48.47 23.87 64.03

8.00 2.50

95.90 59.87 36.71 23.16 35.09 61.12

— —

46.47 14.51

— —

0.494 —

— —

Nil 0.256

Nil 1.03

DK

14.19

29.44 9.19

94.44 89.85 72.38 17.47 70.40

3.25

10.08 3.15

94.81 74.17 52.22 21.95 62.00

9.00 2.81

97.49 60.06 36.81 23.25 35.86 61.26

— —

48.51 15.14

— —

0.512 Nil

Nil Nil

Nil Nil

10.211 12.253

GD

14.22

21.22 6.62

92.90 85.16 64.74 19.42 65.44

- 1 . 9 5

13.93 4.35

95.06 73.00 50.52 22.48 62.24

7.45 2.32

98.79 54.26 36.91 17.35 27.17 50.68

— —

42.60 13.29

— —

0.529 Nil

Nil 1.517

Nil Nil

0.940 1.13

DL

14.92

29.99 9.36

94.55 87.92 69.34 18.58 60.60

2.22

7.57 2.36

94.88 70.91 48.22 22.69 61.80

8.14 2.54

96.66 59.49 37.47 22.02 34.04 59.19

— —

45.70 14.26

— —

0.506 Nil

Nil Nil

Nil Nil

0.703 0.84

G:

12.1

30. • 9.<

93.( 89. i 72. < 17.2 69.<

3 . :

12.: 3.1

94. < 74.: 52. ' 21.1 61 . '

9.' 2.«

97.( 60.1 39.1 20.1 33.1 57.1

47.! 75.:

76.: 23.;

4. 0.

0.6

I 12.2 1.8 51.

* Brix in Mixed Juice. t Weighed Averages of A-l and A-2 strikes. X Inclusive paper factory

Exhaustion is: "recovered crystal per 100 sucrose in massecuite". Crystal % Massecuite is: "recovered crystal per 100 parts of massecuite".

Page 30

Proceedings of The South African Sugar Technologists' Association —June 1970 15

CLARIFYING AGENTS AND OF ADDITIONAL FUELS

MV JB UC TS ME IL RN SZ UK

14.18 14.55 14.46 13.86 (13.03) 14.49 13.87 14.53 14.47

35.00 30 08 30.60 30.10 (31.27) 37.07 21.03 33.71 30.68t 10.93 9.39 9.55 9.40 (9.76) 11.57 6.57 10.52 9.58 91.51 92.96 92.52 92.74 91.39 92.44 93.70 92.56 92.43 88.66 86.40 85.87 86.40 86.29 88.91 85.51 87.17 87.43 72.34 69.90 67.96 69.17 70.95 74.60 67.52 72.52 71.78 16.32 16.50 17.91 17.23 15.34 14 31 17.99 14.65 15.66 66.55 63.44 65.10 64.68 61.19 63.36 64.77 61.16 63.44

2.52 2.70 1.83 0.92 0.81 4.03 0.29 0.33 -0 .15

11.45 11.40 12.62 8.29 (15.48) 11.87 11.42 16.62 8.88 3.58 3.56 3.94 2.59 (4.83) 3.70 3.57 5.19 2.77

93.93 94.96 94.68 93.58 93.44 93.31 95.61 95.33 95.27 72.46 75.20 70.58 69.06 71.48 75.75 74.06 72.44 73.55 46.31 53.10 47.59 50.94 53.38 53.94 49.51 48.91 51.00 26.15 22.10 22.99 18.11 18.10 21.81 24.55 23.53 22.55 67.22 62.66 62.22 53.45 54.31 62.51 65.65 63.58 62.57

7.84 10.71 9.19 8.48 (9.41) 9.74 8.28 9.66 7.25 2.44 3.34 2.87 2.65 (2.94) 3.04 2.58 3.12 2.26

96.66 97.84 97.16 94.77 95.92 97.60 97.33 99.19 97.94 .56.00 60.70 57.78 58.69 59.81 61.38 59.88 59.66 59.78

36.86 38.93 39.06 39.10 41.34 36.97 38.74 40.77 38.69 19.14 21.77 18.72 19.59 18.47 24.41 21.14 18.89 21.09 29.30 34.88 29.85 30.48 30.20 37.80 33.59 31.63 33.69 54.13 58.73 53.16 54.81 52.64 63.09 57.63 53.46 57.54

— — — — — — — 36.94 —

54.29 52.19 52.41 46.87 (56.16) 58.68 40.73 87.05 46.81 16.95 16.29 16.36 14.64 (17.53) 18.32 12.72 27.17 14.61

_ _ _ _ _ _ _ 3.637 — — — — — — — — 0.523 —

0.637 0.856 0.860 0.580 0.567 0.519 0.671 1.819 0.533 Nil Nil Nil Nil Nil — — 0.001 —

37.84 147.72 112.27 Nil — — — 0.477 894 6.31 6.659 6.909 263.7 — 7.496 — — 73

Nil Nil Nil ? Nil — Nil 0.048 — 5.591 Nil 22.408 ? 0.062 3.850 Nil 4.141 Nil 2.377 9.508 0.702 ? — 9.180 Nil 0.523 1.859 25.22 11.41 90.47 ? 0.248 26.416 Nil 17.480 2.23

Averages

14.52

30.01 9.36

92.79 87.11 70.28 16.83 65.01

1.66

11.49 3.59

94.55 72.53 50.76 21.77 60.96

8.91 2.78

97.20 59.11 38.74 20.37 32.32 56.25

—

—

—

MH UR LB MR NH

14.79 14.37 13.71 14.83 15.12

27.83 30.94 31.44 27.20 — 8.69 9.66 9.82 8.49 —

92.19 91.70 93.52 93.11 — 85.74 87.90 83.76 87.08 — 67.54 71.90 69.45 70.88 — 18.20 16.00 14.31 16.20 — 65.39 64.78 55.92 63.88 —

-1 .33 4.00 -1 .84 2.48 —

13.66 12.69 16.56 16.91 — 4.26 3.96 5.17 5.28 —

93.41 94.10 94.18 95.76 — 73.06 75.30 72.93 73.93 — 54.52 52.00 52.77 52.52 — 18.44 23.30 20.16 21.41 — 55.62 . 64.47 58.53 60.99 —

9.68 10.84 10.71 10.59 — 3.02 3.38 3.34 3.31 —

95.57 97.90 98.27 101.19 — 62.84 61.60 59.50 60.50 — 40.91 37.59 38.33 39.48 — 21.93 24.01 21.17 21.02 — 35.47 37.66 33.73 35.15 — 59.06 62.45 57.69 57.41 —

47.16 31.38 — 54.95 65.38 43.50 — 76.18 —

51.89 64.32 58.71 82.36 — 16.20 20.08 18.33 25.71 —

0.856 1.407 1.412 1.295 — — 0.002 0.316 0.007 —

— — — 0.340 — 5.419 2.416 0.874 0.491 —

— — — 2.436 — 0.002 8.958 1.233 — —

_ _ 7.594 15.647 — 0.008 35.833 14.045 33.392 —

1 m3 fuel oil is equivalent to 6.1 short or 5.5 metric tons of bagasse. 1 short or 1 metric ton of fuel oil is equivalent to 6 short resp. 6 metric tons of bagasse. 1 short or 1 metric ton of coal is equivalent to 4 short resp. 4 metric tons of bagasse. 1 m3 fire wood is equivalent to 0.46 short or 0.42 metric tons of bagasse of 3 000 btu/lb. resp. 6 978 kj/kg.

Page 31

16 Proceedings of The South African Sugar Technologists'" Association — June 1970

TABLE E

COMPARATIVE MANUFACTURING DATA OF RECENT YEARS (S.A.

SEASON

CANE Sucrose "/„ Cane Fibre % Cane

JUICES Brix" First Expressed Juice . Purity of First Expressed Juice. Purity of Last Expressed Juice . DROP in Purity Purity of Mixed Juice Reducing Sugars/Sucrose Ratio

MILLING Imbibition % Fibre LOST ABSOLUTE JUICE % FIBRE Imbibition % Cane EXTRACTION Sucrose % Bagasse Moisture % Bagasse Bagasse % Cane Lower Calorific Value (btu/lb.) . Available btu per lb. Brix . . . .

1969/70

12.88 15.03

1968/69

13.11 15.32

1967/68

12.92 15.01

19.00 86.06 68.78 17.28 84.25 4.17

19.54 85.49 69.72 15.77 83.60 4.23

19.16 85.26 71.43 13.83 83.41

3.81

274 34.15 41.22 94.98

1.89 53.30 34.18 3,011 7,085

268 34.38 41.12 94.74

1.98 53.52 34.93 3,008 7,070

261 38.32 39.15 94.15

2.19 53.47 34.53 2,991 7,084

1966/67

13.72 15.09

19.84 86.97 72.43 14.54 85.06

3.62

262 37.91 39.60 94.22

2.29 53.52 34.56 2,985 6,788

MILLS)

1965/66

12.99 15.57

19.27 86.30 72.30 14.00 84.22

3.73

261 37.58 40.57 93.99

2.20 52.98 35.42 3,033 7,414

RECOVERIES BOILING HOUSE PERFORMANCE Boiling House Recovery . . . . Overall Recovery Tons Cane per Ton Sugar . . . .

FILTER CAKE Sucrose % Cane . Filter Cake % Cane

88.58 84.13 9.10

96.19 87.40 82.72 9.06

95.82 87.52 82.33 9.28

1.58 4.49

2.08 4.71

2.10 4.71

95.96 88.38 83.27 8.63

2.16 5.21

95.65 87.67 82.40 9.20

1.57 5.62

FINAL MOLASSES GRAVITY PURITY . Degree Brix . . . . Weight at 85° Brix % Cane

38.43° 91.37

3.55

39.40 91.81

3.78

38.75 92.03

3.69

40.65 93.45

3.47

39.91 91.72

3.59

AVERAGE SUGAR POLARISATION 98.68° 98.42° 98.34° 98.58° 98.49°

SUCROSE BALANCE Lost in Filter Cake 0.55 0.77 0.80 0.82 0.68 Lost in Final Molasses 9.01 9.64 9.38 8.75 9.38 Undetermined Losses 1.29 1.51 1.57 1.38 1.53 LOST IN BOILING HOUSE 10.85 11.92 11.75 10.95 11.59 Lost in Bagasse 5.02 5.36 5.92 5.78 6.01 TOTAL OF ALL LOSSES 15.87 17.28 17.67 16.73 17.60

CU. FT. OF MASSECUITES PER TON BRIX A-massecuite 30.01 29.30 29.44 29.02 B-massecuite 11.49 11.67 11.74 10.30 C-massecuite 8.91 9.25 9.59 8.83 TOTAL 50.41 50.22 50.77 48.15

EXHAUSTION OF MASSECUITES A-massecuite 65.01 64.73 65.05 62.85 B-massecuite 60.96 60.35 61.31 58.36 C-massecuite 56.25 56.15 58.28 55.59

PURITY RISE A-massecuite purity 87.11 86.26 86.07 86.68 85.91 Syrup purity 85.45 84.92 84.59 86.03 85.06 RISE + 1 . 6 6 +1 .34 +1 .48 +0 .65 + 0 . 8 5

DENSITY ("BRIX) OF SYRUP 61.03° 61.23° 59.96° 60.35° 59.33°

27.89 11.78 9.14

48.81

62.78 59.53 56.37

|

Page 32

TABLE F AVERAGE MANUFACTURING RESULTS BY MONTHLY PERIODS FOR SOUTH AFRICAN MILLS

(Season 1969 - 1970)

END OF MONTHLY PERIOD:

TONS SUGAR MADE & ESTIMATED

TONS CANE CRUSHED . . . .

TONS CANE CRUSHED PER HOUR ACTUAL CRUSHING

SUCROSE % CANE

FIBRE % CANE

TONS CANE PER TON OF 96° SUGAR

LOST ABSOLUTE JUICE % FIBRE

IMBIBITION % FIBRE

SUCROSE EXTRACTION . . . .

SUCROSE % BAGASSE . . . .

MOISTURE % BAGASSE . . . .

BOILING HOUSE RECOVERY . .

OVERALL RECOVERY

MIXED JUICE PURITY . . . .

R.S./SUCROSE RATIO

SUCROSE/SPINDLE BRIX PURITY OF FINAL MOLASSES

SUCROSE LOST IN FINAL MO­LASSES % SUCROSE IN CANE

UNDETERMINED LOST SUCROSE % SUCROSE IN CANE

MONTHLY RAINFALL (INCHES) . RAINFALL FROM 1st JANUARY .

Month To Date

Month To Date

To Date

Month To Date

Month To Date

Month To Date

Month To Date

Month To Date

Month To Date

Month To Date

Month To Date

Month To Date

Month To Date

Month To Date

Month To Date

Month To Date

Month To Date

Month To Date

Month To Date

May 31 1969

(54,927) (54,927)

563,893 563,893

184 184

11.79 11.79

14 30 14.30

(9.98) (9.98)

35 35

269 269

95 06 95.05

1.76 1.76

54 85 54.85

(85 81) (85.81)

(81.57) (81.57)

82 95 82.95

4.92 4.92

38.01 38.01

9.06 9.06

(3.77) (3.77)

3.98 22 86

June 28 1969

(159,730) (214,657)

1,510,277 2,074,170

165 170

12.35 12.20

14 60 14 52

(9.22) (9.42)

36 35

268 268

94.95 94.98

1.85 1.83

53 86 54.07

(88 55) (87.78)

(83.97) (83.30)

84 15 83.83

4.03 4.11

38.21 38.10

9 04 9.03

(1.28) (1.99)

0.64 23.17

Aug. 2 1969

(265,230) (479,887)

2,390,063 4,464,232

176 173

12.84 12.54

14.50 14 53

(8 79) (9.07)

34 34

272 270

95.14 95 07

1 88 1 86

53.55 53.79

(89 34) (88.64)

(84.93) (84.19)

84 44 84.16

4.02 4.50

39.10 38.57

8.29 8.62

(1 31) (1.63)

0 73 23.85

Aug. 30 1969

(227,472) (707,359)

1,943,007 6,407,239

176 174

13.55 12.85

14.60 14 55

(8 32) (8 83)

34 34

278 272

95 14 95.02

1.99 1.90

53.13 53.59

(89.59) (88.94)

(85.15) (84.50)

84 68 84.33

3.97 4 03

39.08 38.74

8.79 8.68

(1.50) (1.54)

0.54 24.28

Sept. 27 1969

Nov. 1 1969

Nov. 29 1969

Dec. 27 1969

Feb. 1 1970

Feb. 28 1970

Mar. 21 1970

(226,404) (249,535) (195,176) (158,541) (172,981) (70,938) — (933,763) (1,183,398) (1,378,474) (1,537,015) (1,709,996) (1,780,934) (1,792,077)

1,895,431 2,165,300 1,779,446 1,524,722 1,683,579 735,978 — 8,302,670 10,467,970 12,247,416 13,772,138 15,455,719 16,191,695 16,300,826

178 175

13.93 13.10

14 94 14.64

(8 15) (8.66)

32 34

277 273

95.32 95.15

1.93 1.90

52.26 53.28

(88 76) (88.92)

(84.62) (84.61)

84.92 84.47

3.87 3.98

38.50 38.52

8.26 8.57

(1.60) (1.56)

* 2.98 27.19

173 174

13 42 13.16

14 92 14.70

(8 50) (8.63)

31 34

278 274

95.29 95.18

1.86 1.89

53.60 53.34

(88.34) (88.80)

(84.17) (84.51)

84.71 84.52

3.80 3.95

39.02 38.23

9.03 8.67

(1.51) (1.45)

6.14 33.94

171 174

12.84 13.09

15 62 14 83

(8.81) (8.65)

32 33

273 274

95' 02 95.15

1.84 1.89

53.03 53.30

(89.37) (88.88)

(84.92) (84.57)

84.47 84.51

3.98 3.96

38.45 38.27

8.30 8.61

(1.20) (1.42)

3.98 37.80

176 174

12.29 13.03

15.51 14 91

(9.34) (8.72)

32 33

276 274

94.82 95.12

1.81 1.88

53.05 53.27

(88.21) (88.81)

(83.64) (84.47)

84.47 84.51

4.38 4 06

38.50 38.30

9.14 8.67

(1.45) (1.43)

3.66 41.54

179 175

12.25 12.94

15.66 14.99

(9.48) (8.80)

35 33

260 273

94.50 95.05

1.90 1.88

53.08 53.25

(87.48) (88.68)

(82.65) (84.29)

83.83 84.41

4.63 4.12

37.84 38.42

10 12 8.82

(1.20) (1.39)

3 07 3.07

199 176

11.75 12.89

15.80 15.03

(10.11) (8.85)

34

310 275

93.80 95.00

1.98 1.89

54.13 53.30

(88.57)

(84.14)

81.00 84.25

4.10

37.62 38.37

9.00

(1.30)

2 09 5.16

176

12.88

15.03

(8.86)

34

274

94.98

1.89

53.30

(88.58)

(84.13)

84.25

4.17

38.43

9.01

(1.29)

—

Page 33

Proceedings of The South African Sugar Technologists' Association —June 1970

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Page 34

Proceedings of The South African Sugar Technologists' Association—June 1970 19

DISCUSSION

Mr. Perk: I try and introduce at least one new item into my report each year.

For example, the nonsucrose ratio was introduced to have a check figure at hand to assess the accuracy of the recorded final molasses weights. Members should remember that in 1952 only ten factories published their final molasses weights and it took seventeen years before all mills had final molasses scales. There were factories which took the total 'tanker weights' as the weight of the produced molasses over the season; the molasses weight being therefore available only once a season. There was another mill which measured the volume of the produced molasses. It was this mill that showed the biggest deviations from the normal nonsucrose ratio. It is not only the nonsucrose ratio which I use as a check on the accuracy of the final molasses weight; the reduc­ing sugars balance, the circulation ratio of final molasses inside the system "C-m.c. pans and centrifugals" also throw a light on the accuracy of the final molasses weights.

Quotations of the Monthly Weather Report were this year omitted as other papers deal with this subject more thoroughly. The results of the weather on the ripening of the cane is shown in a number of tables where "sucrose content of the cane by months" and "purity of the mixed juice by months" are compared with average values for these properties.

As far as the South African cane belt is concerned, the 1969/70 season started with a very low sucrose content of the cane and during the whole season the sucrose content stayed below the forty-one year averages. The mixed juice purity started at a normal value but did not improve during the course of the season.

Table 4 shows how much lower the average juice purity and the average sucrose content of the cane har­vested during the last ten optimum periods were than the corresponding values of the previous decade. It is particularly the lower juice purities which affect the boiling house most, by reducing recovery, increasing sugar losses and steam consumption, and overloading the backend of the factory.

Marromeu's mixed juice showed a purity of 88.88° in September 1969. Luabo's maximum sucrose content of 15.57%, though high according to South African standards, is still below the mean value of 15.98% for the October month.

The mixed juice purities and the sucrose contents of the cane harvested by Mhlume and Big Bend do not differ much from the values obtained in other years.

With regard to the time account and length of seasons, the introduction of the seven-day week or the week of 168 hours available time brings to the fore how much

time could be won if the weekend stop could be reduced in length. In the last season the average time lost by weekend stops was twenty-one hours per week; the highest loss being twenty-nine hours, the smallest loss four hours per week, i.e. eight hours per milling tandem in alternative weeks.

In a chapter on refractometric and hydrometric brix determination it is pointed out that the refractometric brix, although it gives a closer approach to the actual dry matter content of the product, cannot replace the spindle brix in all cases as the refracto brix is not directly related to the specific gravity of the product.

A new factory performance indicator has been intro­duced. The part which is really new is the use of the "corrected milling loss according to Follet-Smith" as a yardstick for the performance of the extraction plant, the plant being either a diffuser or a milling train.

Subtracting the corrected milling loss from 100% gives us the whole reduced extraction according to Mittal i.e. the extraction which might have been expected had cane of 13J% fibre and 1 3 | % sucrose been milled.

Multiplying the whole reduced extraction with reduced boiling house recovery, E.S.G. leads to an overall recovery which would have been achieved had the purity of the mixed juice been 85°, in addition to 13|-% fibre and 13 |% sucrose in the cane; the result being indicated as "crystal".

N.B.: For the calculation of the crystal content of the sugar the Winter Formula with a factor of 0.4 is used. Java used for the calculation of the crystal content of a sugar the Winter Formula with a factor 0.5 after converting the pol of the sugar into sucrose content. (Addition of 0.3° for the difference in temperature during polarisation). South Africa is going to use a factor of 0.661 in the formula: S - y - times (B - S) = crystal percentage.

The nonsucrose ratio based on mixed juice appeared to indicate that diffusion factories produced more molasses from their nonsucrose introduced with the mixed juice than did the pure milling factories. However, as about 40% of the mixed juice of a diffusion factory has passed a purification process inside the diffuser, mixed juice of a pure milling factory cannot be compared with that of a diffusion factory. This is apparent when we compare the quantities of filter cake produced by the one and by the other.

For a better basis of comparision, we introduced in 1969 "the nonsucrose ratio based on clarified juice analysis". This change-over eliminated the indication that diffusion factories made more final molasses from their nonsucrose introduced with the juice than did pure milling factories.

However, it still leaves the question unresolved as to whether the diffuser (under similar conditions) extracts more impurities than the milling tandem.

Page 35

20 Proceedings of The South African Sugar Technologists'' Association—June 1970

The abnormal figures encountered in the Reducing Sugars Balance are attributed more to mistakes made when analysing the products for reducing sugars content than to abnormal inversion or abnormal destruction of reducing sugars.

I refer now to the Sucrose, Brix and Nonsucrose balances and the Ratio or Purity of the Undetermined Losses.

As all these balances are based on the clarified juice analysis no discrimination has been made between diffusion and milling factories. However, as some fac­tories apply the refractometer when analysing the boiling house products and others the hydrometer, the results had to be divided into two groups i.e. factories using the refractometer and those determining their brix with the spindle.

Attention is drawn to the three factories which publish the results only of their rawhouse departments and not of the complete combination of refinery and rawhouse departments. They all show very low undetermined sucrose and brix losses. In such cases small inaccuracies in both losses will lead to abnormal figures for the non-sucroses losses and for the ratio (or purity) of the undeter­mined losses. For example, Sezela shows a negative nonsucrose loss and Pongola a too low purity of the losses.

A note under Table 16 tells us that the average of the diffusion factories does not include Nchalo because there is doubt about the correctness of the final molasses weight. This remark was based on the results shown in Table 18 i.e. a negative brix loss, a negative nonsucrose loss and a negative figure for the purity of the undeter­mined losses. This is an example how other properties in addition to the nonsucrose ratio can pinpoint an incorrect final molasses weight. •

As regards the quantity (volume) of C-Massecuite, Table 19 deals with the cu ft of C-m.c. as recorded per ton of nonsucrose in mixed juice. As this table deals with diffusion and pure milling factories it would have been better if the volume of massecuite had been based on the quantity of nonsucrose in clarified juice.

Mr. Jennings: The cane/sugar ratios in South Africa over the years compare unfavourably with the figures

achieved in Australia. In Australia the figure has been below 7.0 whereas we are fortunate if we record a figure of 8.5.

Mr. Perk mentions one avenue of investigation we should pursue to reduce the cane/sugar ratio, namely, deterioration of cane after harvesting.

An aspect which has not been covered is planned harvesting of cane — programmed ripening trials.

Mr. Perk: The emphasis in South Africa has always been on tons cane per acre, and not on tons of available sugar per acre which is of course the really important figure.

As regards metrication, I note that rainfall is being reported in millimetres to two decimal places, an accuracy which I do not think can be achieved.

Mr. Jennings: Mr. Perk has refered to accuracy of reporting. Dr. Parker of Tate & Lyle recently mentioned that the most accurate buffer solution obtainable has a standard error of 0.045 pH and yet we find people who insist on reporting pH to two places of decimals.

Mr. Allan: The Time Account of factories makes interesting reading. The figures for UF are 88.88% for crushing hours per cent available hours. Another factory goes as low as 68.09 %.

Half the factories keep to the average of 76 % but those below this should look into the reasons for the time lost.

Mr. van Hengel: We have a factory with two tandems and when we stop a tandem for maintenance we record this as hours of stoppage.

Does U F do the same ?

Mr. Perk: UF shuts down each tandem on alternative week-ends but does not record this period in hours of stoppage.

I merely produce the figures declared by the factories — I cannot vouch for their accuracy.

Mr. van Hengel: In that case the figures can be highly misleading.

Mr. Alexander: (in the chair) 1 wish to thank Mr. Perk for this his last paper on the summary of laboratory reports.

We shall sorely miss his reports at future meetings.

HAYNEftSIBSON lOBNJ — 28617

Page 36

Proceedings of The South African Sugar Technologists'' Association — June 1970 21

SI UNITS IN THE SUGAR FACTORY* By G. N. ALLAN (Sugar Milling Research Institute)

and A. VAN HENGEL (Huletfs Technical Management Division)

Abstract This paper lists the more common units used in the

SI system and shows how the coherent units may be derived from a few basic conversion factors. Attention is drawn to metric sizes and strengths of materials and a factory calculation is illustrated.

General When the introduction of the metric system in

South Africa was approved in principle in 1966, it was decided that the SI system of units would be adopted. SI stands for Systeme International d'Unites. The units are a coherent system of metric units recom­mended by the International Standards Organization (I.S.O.) for adoption throughout the world.

Historically, the development of a rational system of units required two factors to ensure its adoption. One was a decimal fraction system and the other was a breakdown of the rigid social and political system in Europe before 1795.

The decimal fraction was developed in the 16th century and the Napoleonic wars swept aside the regional barriers. One of the lasting results of these campaigns was the adoption of the metric system throughout Europe and overseas dependencies such as South America. England, by a narrow margin, rejected the system at the time, and is only now converting to the SI system of units, the pressure coming from the engineering manufacturers with an eye to the European Common Market.

The cgs (centimetre, gramme, second) system was used for many years, mainly by scientists, until a pro­posal was put forward by Giorgi in 1902 for the use of the mks (metre, kilogramme, second) system as a more practical system for engineering and commercial use. It was eventually adopted in 1946 by the International Electrotechnical Commission and the more sophisti­cated coherent system as it stands today was accepted in 1954 and given the name SI.

The SI units are coherent. A coherent system is one in which a number of basic units is chosen and then any combination of these units will result in the correct unit for any new quantity without the use of conversion factors.

Basic Units The basic units of the system are accurately defined

in terms of modern technology and are given in Appendix 1. The units are: Quantity Name of Unit Symbol Length metre . m Mass kilogramme kg Time second s Electric current ampere A Thermodynamic

temperature kelvin K Luminous intensity candela cd

Two other units must be mentioned, viz. the radian and the revolution. The steradian is a solid angle measure and is not often used.

Multiples and submultiples A recommended system of multiples and submul­

tiples of the basic units has also been established and is in powers of 103 or 10~3. The numerous and varied factors of 3, 12, 2 240, etc. are now replaced by mul­tiples of 10. mega M 1000 000 106

kilo k 1 000 103

1.0 milli m 0.001 10~3

micro /x 0.000 001 lO"6

Others less frequently encountered are tera T 1012 giga G 10° nano n 10~9 pico p 10~12

The non-recommended multiples which are never­theless still in very common use are: hecto h I02 deca da 10 deci d 10-1 centi c 10~2

Prefixes When a prefix is used the new unit is treated as a

whole, e.g. 1km8 = (103m)3 = 109m3

Only one prefix should be used in a unit, e.g. km/s not mm/^s

No plural must be used and no full stops after units e.g. 2 kg and not 2 kgs.

Use of symbols in texts The decimal point is being retained in South Africa

to separate whole numbers and decimals. In Europe a comma is used for this purpose and, to avoid con­fusion, numbers are to be grouped in threes to the left and right of the decimal point; no commas are to be used, e.g. 4 760 221

0.304 62172 A zero must precede all decimal quantities. Units written out in full will all have small letters,

but abbreviations of units named after people will have capital letters, e.g. gramme g

newton N kilogramme kg ampere A

The correct abbreviation of kilowatt-hour is kWh. If symbols are wrongly used, say KWH, this means °kelvin watt henry, which is at best a little confusing.

Areas and volumes are expressed as m2 or m3 and the abbreviations sq and cu are not to be used.

The new units may appear using indices rather than the solidus / , kgm~3 in preference to kg/m3 or

* Written at the request of the S.A. Sugar Millers Factory Metrication Committee.

Page 37

22 Proceedings of The South African Sugar Technologists' Association — June 1970

kJ s^1 rrr2 K"1 rather than the older form of Btu/ (hr. sq. ft. °F). As Js~ l = W, by definition the SI unit of heat transfer rate is Wrrr2 K -1.

Basic SI units Length m

The metre was originally proposed as j X 10~7

of the meridian through Paris and a metal bar was made to this length and accepted as the standard metre in 1875. The metre is now redefined in terms of atomic radiationcorresponding to the length of thisbar.

In small work and in engineering drawing practice the millimetre is to be used and for surface texture the micrometre would be appropriate.

The centimetre is not a recommended unit and the kilometre will be used for lengths where the mile is now commonly used. lm = 39.37 in 1 in = 25.4 mm 0.001 in = 25.4/xm 1 mile = 1.609 3 km

Mass kg The kilogramme is the mass of a standard platinum

cylinder, and is the unit of mass which should be used generally. For very large masses the metric ton which is equal to 1 000 kg will be used and for very small masses the gramme and milligramme are the appro­priate units. 1 metric ton = 1 000 kg = 2 204.6 lb 1 oz = 28.35 g 1 lb = 0.453 592 kg

Time s The second should be used wherever possible in

calculations and occurs in units involving velocity, power, heat flow rates, etc. The use of the hour and minute will of course continue to be used, but the use of the second in mechanics and thermodynamics as mentioned above immediately simplifies calculations. Road speeds will be given in km/h. The use of the symbol h in hour is in itself confusing as h also stands for hecto = 102.

Temperature K or °C The fundamental scale of temperature is the kelvin

scale in which O K is taken as absolute zero and the triple point of water at 273.16 K.

The temperature intervals of this scale are equal to the Celsius scale which sets 0°C for the freezing point of water (273.15K) and 100°C for the boiling point (373.15K) under normal atmospheric conditions. This Celsius scale is well known even in non-metric countries and will be used in all general references to temperature.

The term centigrade is used in infrequent angular measurement of a 400° circle and must not be used in connection with temperatures.

5 K = - ( °F + 459.67)

9 °R = (°F + 459.67) degrees Rankine K = (°C + 273.15)

5 °C = - (°F - 32)

9

Some sources distinguish between actual tempera­ture and temperature difference by the terms °C and deg C, but this has not been recommended by ISO and therefore not be used.

Electric current A The ampere is defined as a current which would pro­

duce in two infinitely long parallel conductors of neglible cross section placed 1 m apart in vacuo, a force of 2 x 10~7 newton.

Giorgi recognised the need of a fundamental electri­cal quantity with his system of mechanical units in 1902 and suggested the ohm as it was then the most accurate unit available, being measured in terms of a mercury column. The present unit (adopted in 1946) avoids dependence on physical properties.

Luminous Intensity cd Luminous intensity has the unit candela and is the

luminous flux per unit solid angle. Luminous flux is a measure of radiant energy which is capable of produc­ing visual stimulus, and is in part a physiological quantity. The value of the candela is such that the brilliance of total radiation at the temperature of solidification of platinum is 60 candela per square centimetre.

Named units of the SI Refer to fig. 1

Force N Force = mass x acceleration and its unit, the newton

is that force which when applied to a mass of 1 kilo­gramme will produce an acceleration of 1 metre per second per second. I N = 1 kg x 1 ms-2

= 1 kgms-2

This is of course an absolute unit and no gravita­tional factor is involved. 1 dyne = lg x 1 cms -2

109 dyne = 1 J m = 1 Nm2

1 erg = 1 dyne x 1 cm 107 ergs = 107 dyne x 10-2m 1 joule = 107 dyne x 10_2m 1 Nm = 107 dyne x 10-2m IN = 105 dyne 1 N = 7.223 poundal. Now that the newton has been defined let us clearly differentiate between mass and weight. Weight is a force with which a mass is attracted to a centre of gravity. A one kilogramme mass (a quantity of matter) remains the same even if measured on the moon. The weight of this mass on a lunar expedition could vary from the gravitational attraction of earth, to weightless­ness, to the gravitational attraction of the moon. The weight (or force of attraction) of 1 kilogramme mass on earth is 9.806 newton, on the moon its weight would be about 1.6 newton.

F = mass x acceleration = 1 kg x 9.806 ms-2

= 9.806 kgms-2

= 9.806 N

Page 38

Proceedings of The South African Sugar Technologists' Association — June 1970

COHERENT SYSTEM - S1 UNITS

23

FIGURE I

In the Government Gazette No. 2595 of 31st December 1969 in the Weights and Measures Act, an amendment occurs: "1 . The deletion of the word "WEIGHT" in the head­ing of item 1 and the substitution therefor of the word "MASS".

Energy ~\ Work )• J Heat J

By definition, work = force x distance. The joule is that amount of work done when a force of 1 newton is moved through a distance of I metre. 1 j = l N x 1 m

= 1 Nm = 1 kgm2s-2

As a unit of heat it is the direct thermal equivalent of the defined amount of mechanical energy and is thus independent of conversion factors for the mechanical equivalent of heat

1 kWh 1 Btu =

Power

Power

= 3.6 MJ = 1.055 kJ

W work

time

1 erg leal

The watt is equal to 1 joule per

1 W = j

= l _ s Nm

= l — s

= 1 kgm2s-3

= io-7 J = 4.186 8J

second.

The watt will be used to express all quantities of power whether mechanical, electrical or thermal

l h p = 1 kW =

745.7 W = 1.341 hp

1 W = 3.414 Btu/h

Page 39

24 Proceedings of The South African Sugar Technologists' Association — June 1970

Electric Potential V The volt is specified as WA~'

WA l = J A - ' s - 1

----- kg m2A 's :t

For practical use the volt remains identical to what it was, only the definition has changed.

Units not named Pressure Nm a (pascal)

Pressure, which is defined as force per unit area, is measured in newtons per square metre ( N m 2 ) . The value of 1 Nm 2 is too small for practical purposes ( I N m * (). 145038 X 10 ;' Ibf/sq in)and IhekN/m^ and MNm 2 are more acceptable (0.145 and 145 lbf/ sq in respectively). There is, however, merit in a unit which is at roughly atmospheric pressure and for this reason the unit bar has been selected (I bar — 10° Nm " 14.503 8 Ibf/sq in) even though this is not a recognised multiple in the SI system. The submultiple is the millibar.

An "atmosphere" in physics is defined as an air pressure which is in equilibrium with a mercury column of 760 mm. Mercury with a specilic gravity of 13.6 will then exert a pressure of 13.6 x 76 • 1033.6 gfcnr2

I.033 6kgfcm 2

In the past the technical atmosphere was taken as 1 kgfcm "* The bar is defined as 105 N m ' 2

105

= — N cm - 2

10* = lONcm-2

1 On earth one newton is—-— part of a kg weight and

9.806 hence 10 Ncmr2 = 1.0198 kgfcm-2, likewise it can now easily be shown that

1 bar = 1 000 millibar -= 1.019 8

1.033 6 = 0.986 6 "atmosphere'"

and 1 atmosphere = 1 000 = 1 013.6 mbarapprox..

0.986 6

Heat Units There seems to be more mystery than necessary

around the heat unit of the new SI metric system. Here follow a number of ways to convert the Btu

into kilojoules (k.I). lBtu 1 lb X 1"F

0.453 6 kg X 0.555 6nC = 0.252 kcal (not used any longer)

I kcal -•-•••• 426.9 kgf.in (Joule's heat equivalent). .-. 1 Btu -- Alb.9 X 0.252 = 107.58 kgf.m

To check: 1 kgf.m - I kgf x 1 m

- 2.205 lbf X 3.280 84 ft =••= 7.233 ft. lbf

.-. 1 Btu = 7.233 X 107.58 = 778.2 ft lbf (Joule's heat equivalent).

Obviously, whether we go from the kcal or the Btu, we find that:

1 Btu = 107.58 kf.m

The kg force is not used any more and the kg mass takes its place. Now as the average acceleration of the gravity force = 9.81 ms -2

I kgf = 9.81 Newton .-. 1 Btu = 9.81 X 107.58 = 1055.1 Nm

By definition we know that 1 Nm = 1 joule (J) or I Btu = 1 055 J

= 1.055 kJ

Identically:

1 kcal = 1

= 3.968 Btu 0.251

1 kcal = 3.968 X 1.055 = 4.187 kJ

The factor Btu/lb can now easily be converted in kJ/kg

1.055 kJ Btu/lb =

0.453 kg = 2.33 kJ kg-1

Another approach would be: lkWh

3 412 Btu 1 Btu

= 3 412 Btu = 3 600 kWs = 3 600kJ = 3 600 kJ = 1.055 kJ

Specific entropy in kJ kg - 1 K_1 can be calculated as follows:

Btu 1.055 kJ

lb X °R 0.453 kg X 0.555 K = 4 .187kJkg- 1 K- 1

Also the conversion for the heat transfer coefficient is easy:

1 Btu/(sq ft°Fhr) 1.055 kJ

0.304 82m2 X 0.555 °C X hr

= 20.44 kJm- '^C-^- 1

= 0.005 67kJm-2 OC-1s-1

= 5.678 Wm-2 0C~ l

= 5.678 Wm-^K-1

Summary of units commonly used in thermodynamics are given below:

Imperial Units SI Units Quantity of heat Btu X 1.055 = kJ Heat flow rate Btu/hr X0.293 = W Specific enthalpy Btu/lb X2.326 = kJkg-1

Specific heat Btu/(lb°F)x4.187 = kJ kg-^C" 1

Specific entropy Btu/(lb°R)x4.187 = kJ k g - 1 ^ 1

Coefficient of heat transfer Btu/(ft2°Fhr)

X 5.678 = Wm-^C- 1

Page 40

Proceedings of The South African Sugar Technologists'" Association —June 1970 25

TABLE I Saturated Water and Steam

Pressure from the triple point up to 100kN/m2(l bar) (100kN/m2 = 1 bar = 14.5 lbf/in2)

Pressure kN/m2

P

0.611

80 85 90 95

100

101.325

Celsius temp. °

t

0.01

93.5 95.2 96.7 98.2 99.6

100.0

Specific volume C m3/kg

Water Steam Vf V g

0.001000 206.2

0.001039 2.087 0.001040 1.972 0.001041 1.869 0.001042 1.777 0.001043 1.694

0.001044 1.673

Specific internal energy kJ/kg

Water Uf

zero

391.6 398.5 405.1 411.4 417.4

419.0

Steam u g

2 375.6

2 498.8 2 500.8 2 502.6 2 504.4 2 506.1

2 506.5

Specific enthalpy

Water hf

+ 0.0

391.7 398.6 405.2 411.5 417.5

419.1

kJ/kg Evapora'r hfg

2501.6

2 274.1 2 269.8 2 265.6 2 261.7 2257.9

2 256.9

i Steam hg

2501.6

2 665.8 2 668.4 2 670.9 2 673.2 2 675.4

2 676.0

Specific entropy kJ/kg K

Water Sf

zero

1.233 1.252 1.270 1.287 1.303

1.307

Steam Sg

9.157

7.435 7.415 7.395 7.377 7.360

7.355

Pressure kN/m2

P

0.611 Triple point

80 85 90 95

100 1 bar

101.325 latm

Steam Tables The various columns are set out (in Table 1) and

values around standard atmospheric pressure are given as well as the triple point mentioned in the tempera­ture definitions.

The suffixes used in all the columns indicate: f Saturated liquid state g Saturated vapour state fg Difference between saturated vapour and liquid

state Two or three Total Heat/Entropy diagrams are

available differing only in size and clarity of printing. A good one is available in the Haywood Tables which have been issued to all mills. The Keenan and Keyes Steam Tables will be used as the Standard reference tables and this book also includes a very large H/0 diagram.

Area m2

The square metre will be the basic unit of area except for very small areas like the cross-sectional areas of wires, etc.

The square metre is now used in survey area measure­ments and its multiple, the hectare, is used for larger area measurements. lm2 = 10.764 sqft 1mm2 = 0.001 55 sq in 1 hectare = 104 m2 = 2.47 acres

Volume m3

The cubic metre is the basic volumetric unit but is rather on the large side and for smaller measurements the litre or dm3 will be used. The term litre should not be used for precision measurements. 1 m3 = 35.315 cu ft 1 litre = 1.76 pints 1 Imp gal = 4.546 litres

Stress Nm.-2

The basic unit of stress is the same as for pressure, i.e. newtons per square metre. Again this unit is too small for calculating stresses in materials and the kNm~2 and MNm-2 are used.

Usage of the hectobar may also be found, but the MNm -2 (or N mm-2) seems to be published more frequently.

1 MNm-2 = 145.038 Ibf/sq in 1 hectobar = 1 450.38 lbf/sq in

The units used for Moduli, e.g. Youngs Modulus will again be Nm~2, but of a higher order, i.e. GN m - 2

particularly for metals. 1 GNm-» = 145 000 lbf/sq in

Hardness Hardness is usually obtained by certain physical

tests involving indentation of metal surface and these numbers will remain, as no direct conversion is pos­sible between them. The four hardness numbers in common use are Brinell, Vickers, Rockwell and Shore.

Density The simplicity of the metric system is best illustrated

in calculation of density. In fact, for water at 4°C and under normal atmospheric pressure the units of mass and volume are identical. For any other material the ratio between units of mass and volume are identical at the specific weight of the material.

1 litre is the volume occupied by 1 000 g of water at prescribed conditions. The litre is the equivalent of 1 cubic decimetre.

The mass of 1 cm3 of water The mass of 1 dm3 of water The mass of 1 m3 of water

The mass of 1 cm3 of mercury = 454

1 lb/cu ft =

U l k g

1000 kg 1 metric ton 13.6 getc.

-gcm-

1 lb/cu ft 1 lb/cu ft

30.48 X 30.48 X 30.48 0.016 gem-3

0.016 kg dm - 3 or kg per litre 0.016 metric ton per m3

Viscosity The units of viscosity are given below and as yet

have not been given names in the SI units. The cgs definition of dynamic viscosity is given as a basis for consideration. Absolute or dynamic viscosity, meas­ured in poise, is the resistance (in dynes per square centimetre of its surface) offered by a layer of" the fluid to the motion, parallel to that layer, of another layer of the fluid at a distance of 1 cm from it with a relative velocity of 1 cm/s. The dimensions of the Poise in the old system are dyne sec/cm2. In the new SI system these units have been replaced and the unit of dynamic viscosity is measured in Nsm-a.

Page 41

26 Proceedings of The South African Sugar Technologists' Association — June 1970

The name poiseuille (PI) has been suggested for this new unit.

Poise -= dyne s cm~2 can be multiplied by 10"1 to give the SI units of Nsm 2.

dyne s Poise = —

cm2

10 •r> N s

10" m2

== 10" Ns m-2

centipoise = 10~3Nsm-2

The centipoise (cP) == 10~3 Nsm 2 is listed by S.A.B.S. as a unit which may be used.

Kinematic viscosity, which is dynamic viscosity divided by mass density is given in mV but again the centistoke (cSt) which equals 10~

Poise Stoke =

m V 1 may be used.

mass density dyne s cm3

— X cm2 g

g X cm s cm" X

cm2 cm'

= 10-4m2s-1

centistoke = 10_6m2s_1

Volume flow m3s_1

The cubic metre per second is the basic volumetric flow measurement (cumec) but small units will be more commonly used and these are the litre per second and the cm3 s_1.

m s s - i _ 35.315 ft3/sec (cusec) litre s_1 = 13.2 gal/min

1 f tV 1 == 0.028 nvV1

Mass flow kg s - 1

For calculations involving the flow of liquids in pipes, etc. kgs -1 should be used

1 kgs" = 7 936.6 lb/hr

Electric Units These are derived from the basic units as shown in

fig. 1 taking the volt as a derived unit from the basic watt and ampere. These units have been in use for many years and the system as a whole will not require much rethinking by electrical engineers.

Properties of some metals The properties of some commonly used engineering

materials are given in Table 2 in SI units so that the order of magnitude of the units can be established for conversions which may have to be carried out. The second set of values in Imperial units are from another source and axe NOT arithmetical conversions of the SI table.

Mild steel as used in normal boiler plate, RSJ's, austenitic stainless steels 18/8 and higher grades of cast iron will fall under the following ranges: Yield Stress 200 - 300 MNm-2

20 - 30 hbar 15 - 20 tons/sq in

Tensile Strength 300 - 450 MNm-2

20 30 tons /sq in A reasonable working stress in a steel structure

would be between 100 and 200 MN/m-2.

Preferred Numbers In the production of engineering materials it is not

sufficient merely to convert the Imperial sizes to the

TABLE 2 Properties of Some Metals and Alloys

Aluminium Copper Brass Phosphorbronze

IRON: Wrought Cast Mild Steel High C Steel

Aluminium Copper Brass Phosphorbronze IRON: Wrought Cast Mild Steel

Melting Point

K

933 1 356 1 200 1270

1 500 1600

°F

1210

1 850

2 200 2 500

Density

kgm"3

2710 8 960 8 370 8 850

7 850 7 600 7 800 7 700

Ibs/cuft

160

545

480 450 493

Specific Heat Capacity

Jkg-'K-1

875 386 365

444

Btu/(lb°F)

0.219

0.092

0.114 0.116

Youngs Modulus

GNiti"8

70 107-130

100 120

210 100-130

210 210

psi x 10"

10.0

17.0 16.0

29.5 14 7 30.0

Poisson's Ratio

0.34 0.36

0.34-0 40 0 38

0.28 0.23-0.30

0 28 0.29

Ultimate Strength

MNm-2

90-150 200-350 350-510 65 %C 35 %7n (Yellow) 450-700 9

330 210&73O*

490 1600

psix 103

19

40 66

48 32 57

0%C.il0%Sn

%C %Mn %Si 0 7 0 05 0 15 3 5 2 0 0 15 0 45 0 2 10 0 26 0 16

1 060 Strain Hardened

85%Cul5%Zn(Red) 10%Sn Annealed.

•Tensile & Compressive

Page 42

Proceedings of The South African Sugar Technologists'" Association — June 1970 11

nearest convenient metric size, but that a logical sequence of an increase in strength should go with increase in size. This size increase should be a geometric series, each size should be larger than the previous one by the same percentage. (B.S. 2045).

The SI system first expected that every size in the series should have one ten times as great. It then required the number of intermediate stepstobedecided. This number was fixed at five, ten, twenty, forty or eighty. If the first series from 1 mm to 10mm must be divided into five steps, then the common ratio is 8-\/10 or 1.585, and every size would be 1.585 larger than the lower one. The series would then be

1 1.585 2.51 3.98 6.31 10 Rounded off values are

1 1.6 2.5 4 6.3 10 This is called the R5 series because the fifth root often is used. R stands for Renard. As the 58 |% rise is often found too great the RIO series is used, each size increasing 1.259 times, or by 25.9 % The rounded off series is 1 1.25 1.6 2.0 2.5 3.15 4.0 5.0 6.30 8.0 10 Similarly there are R20, R40 and R80 series. These numbers are known as Preferred Numbers, the R5 series being first choice and so on. Plate, round bar and bolt sizes have been adopted using this basis and the nearest sizes to inch sizes are tabulated below:

METRIC SIZES FOR BASIC MATERIALS

Inch

Mild Steel Plate

•3 4

.5

6

8

•10

.12

-15

18

•20

•22

.25

Bright Steel Shafting

-3

Black Bolts

20

22

-24 -25

millimetre

5 - 6

_ 8

'10

•12

"16

-20

-24

It can be seen that the Renard series has not been rigidly adhered to and where costly alterations to steel rolling mills have to be made, Imperial sizes are being continued. This is the case with all structural sections.

Pipe and pipe threads will be manufactured to British Specifications but with metric dimensions.

Screw Thread The ISO metric screw thread is to be adopted as the

standard for the new system. The thread angle is 60° with the top flattened and the bottom rounded. Specifications will give exact details of the three classes of fits to be made. (B.S. 3643.) The pitch will be expres­sed in mm and not as so many threads per unit length. It is expected that stocks of black bolts will be readily available during 1971. (B.S. 4190).

Drawing Office Practice The S.A.B.S. have issued a Standard No. 0111 on

drawing office practice. All drawings will be dimen­sioned in mm, the number only appearing on the dimension line and not the unit mm. Scales will be of the order of 1:2, 1:5, 1:10, etc. 1:100 will replace the building plan scale of 1/8" = 1 ft. Drawing paper will be ISO 'A' series, which is based on a rectangle of 1 m2

with sides in the ratio of 1 to y/2.

Tolerances The ISO standard for Limits and Fits has been

published as BS 4 500 : 1969. This is a formidable journal and the S.A.B.S. are preparing an abridged version which will be available for practical use in the workshop.

Example of SI units in a calculation 300 metric tons of mixed juice per hour at 14° Bx

and 30°C are to be pumped through a juice heater using vapour at 1.3 bar abs. The required temperature is 44°C and the heater has 14 passes of 26 tubes each. The tubes are 2" O.D. and 16 ga X 4 m long. The static pumping head is 6 m. What size motor must be used on the pump, how much vapour will be condensed and what is the coefficient of heat transfer of the heater ?

mass Juice flow rate

14° Bx Flow rate

Tube area per pass

Juice velocity =

Pressure drop across heater

V D C L

mass density 1.056 54 S.G.

300 X 1 000 X 1 n r s -

1000 X 1.056 54 3 600 0.078 87 m V 1

TO!2

X 26 4

0.046 312 m2

0.078 87 m3s_1

0.046 312 1.703 ms-1

V2

P = 0.002 — C(L-f-l) D

flow velocity ms_1

tube diameter m number of passes tube length m

Page 43

"*W**™«M

28 Proceedings of The South African Sugar Technologists' Association — June 1970

1.7032

P = 0.002 X X 14 (4 + 1) 0.047 6

= 8.529 4 m Assuming a 50% pump and transmission efficiency: Power required = 300x 1 000X 9.81X (8.529+6)

3 600 X 0.5

Heat required for juice per hour

kg m ( — X — X m)

s s2

= 23 754 watts = 23.754 kW

= 300 X 1 000 X (44 - 30) X (0.9 X 4.186)

k g h - i X ^ x k J k g - ^ C - 1

Heat available = M X (2 687 - 449) in steam

kg x kJ kg-1

Mass steam required 300x 1 OOOx 14x(0.9x4.186)

M = 2 242

= 7 070 kg h - 1

Heating Surface x Coeff. Heat Transfer x log mean temp. diff.

= Flow rate x Temp, risex Spec. Heat

H.S. = 0 . 0 4 7 6 x 3 . 1 4 1 6 x 2 6 x 1 4 x 4 = 217 m2

44 - 30 Log mean temp. = = 69.6°C

diff. 2.3 1og77

Coeff. H.T. =

63

300 X 1 000 •X14X-

(0.9X4.186)

3 600 217x69.6 = 0.291 k W m - ^ C - 1

= 291 Wm-^C- 1

To check order of magnitude of results: 1

23.754 kWx = 31.8 hp 0.746

7 070kgh"1x2.204 1

291 Wm-«°C-1x — 5.678

15 582 lbs/hr

51.25 Btu/ (ft2hr°F)

Simple derivation of units By remembering a few important conversion factors

it is very easy to build up the correct form of any of the SI units.

Area We must know 1 in = 25.4 mm

1 acre = 4 840 sq yds 1 hectare = 10 000 m2

Then: 12 inches = 304.8 mm lft = 0.304 8 m 3 ft = 0.9144 m

1000 1 metre = 36X = 39.37 inches

914.4

How many miles in a kilometre?

1 km = 1 000 m 1000 39.37

X -12 5 280

= 0.621 36 miles How many acres per hectare ?

1 ha = 10 000 m2

1 acre = 4 840 sq yds 1 acre = 4 840x0.9144x0.914 4

10 000

Volumes 1 cuft

lm»

4 046.8 2.471 acres.

0.304 8x0.304 8x0.304 8 m3

0.028 316 8 m3

39.37x39.37x39.37 61 023 cu ins 61 023

cuft 1 728

35.314 cuft 35.314

— cu yds 27

1.307 9 cu yds

Note: 1 Imperial gallon Then 1 gallon

= 0.16 cuft = 0.16x0.028316 = 0.004 5 m3

= 4.5 dm3 (or litres)

Temperature If we remember that both Fahrenheit and Celsius

scales start at different points and that the Fahrenheit scale covers 180° from freezing to boiling and the Celsius scale covers 100° from freezing to boiling, it is not difficult to remember that

(°Cx 180) °F = +32

100

°C = (°F - 32) x 100

180

Freezing point (ice) ... Room temperature ...

°c 0

20 30

°F 32 68 86

l l

Page 44

Proceedings of The South African Sugar Technologists' Association — June 1970 29

Body temperature

Boiling point (water)

36.9 60 80

100

98.4 140 176 212

Heat Units Remember: = 0.555 5 °C

= 25.4 mm 453.6 g

Then: 1 lbf/sq in

1°F 1 in 1 lb 1 Btu = 1.055 kJ

1 lbf 453.6 gf

1 sqin 25.4x25.4 mm2

453.6X10-3 kgf

25 .4x25.4xl0- 2 cm 2

= 0.070 3 kgf cm-2

lbf or 1 lbf/(sq ft °F hr) =

sq f tx°Fxhr

453.6 gf

144x25.4x25.4x0.555 5 x 3 600

453.6X10"3

144x25.42x 10-6X0.555 5 x 3 600 kgfm-2°C - V

= 0.002 44 kgfm->°C-1s-

or 1 Btu/(sq ft hr) = Btu

sqf txhr

1.055 kJ

122x25.42xl0-6 m 2 x3 600 s

= S . l S x l O ^ k J m ^ s " 1 ' = 3.15 Wm~2

It will be sufficient to remember the four basic conversions given above.

Factory Conversion The main factors in factory conversion have been

(1) Conversion of scales and weighbridges to read kilogrammes

(2) Alterations to laboratory control sheets

(3) Recalibration of process vessels for stocktaking

(4) Education of factory personnel at different levels and of different interests

(5) Conversion of gauges, charts, etc.

Pressure Units It has been decided that for low pressure and

vacuum measurements the bar absolute will be used. For vacuum measurements the sub-multiple millibar absolute will replace inches of mercury.

Boiler pressure gauges and other process lines will be measured in bars (gauge).

1 bar = 105 Nm-2 = 100 kNm"2

1 bar = 14.503 8 lbf/sq in = 750.062 mm Hg = 29.530 in Hg

1 atm = 760 mm Hg = 1.013 25 bar

Millibars abs

300 280 260 240 220 200 180 160 140 120 100

Vac. gauge in Hg.

21.061 21.651 22.242 22.832 23.423 24.014 24.604 25.195 25.785 26.376 26.967

Sat Temp °C

69.1 67.5 65.9 64.1 62.2 60.1 57.8 55.3 52.6 49.4 45.8

APPENDIX I Basic SI units and Definitions

METRE: Length equal to 1 650 763.73 wavelengths in vacuo of the radiation corresponding to the transition between the energy levels 2p1(> and 5 d5 of the krypton 86 atom. KILOGRAMME: The mass of the international prototype kilogramme in the custody of the Bureau International des Poids et Mesures in Sevres, France. SECOND: The duration of 9 192 631770 oscillations of a radiation corresponding to a transition between the two hyper-fine levels F = 4, M = O and F = 3, M = O of the fundamental stage 2 S £ of an atom of caesium 133. AMPERE: The constant current which, if maintained in two parallel rectilinear conductors of infinite length, of negligible cross section and placed at a distance of one metre apart in vacuo, would produce between these conductors a force equal to 2 x 10 _7 newton per metre length. KELVIN: A unit of temperature equal to the fraction 1/273.16 of the temperature of the triple point of water. CANDELA: The luminous intensity in a direction perpendicular to the surface of 1/600 000 square metre of a black body at the temperature of the freezing point of platinum at a pressure of 101 325 newton per square metre.

References use extensively in the text Basic Guide to the Metric System in South Africa South African Bureau of Standards 2nd Ed. 1969 Metric Sizes for Basic Materials

S.A.B.S. SI Units in Engineering

Blackman, D. R. Macmillan 1969 Steam Tables

Keenan, H. J. et al John Wiley 1969 Thermodynamic Tables in SI (metric) Units

Haywood, R. W. Cambridge University Press Materials Selection for Process Plants

Gackenbach, R. E. Reinhold Publishing Corp. 1960 Engineers Diary

Collins 1965 Engineering Materials and Design

Metric Data Sheets Jan. 68 — March 69 Metrication: New Standards for Components

E.M.P.E. Certificated Engineer. March 1969 Metrication: Preferred Numbers

E.M.P.E. Certificated Engineer. Jan. 1969

Page 45

30 Proceedings of The South African Sugar Technologists'' Association — June 1970

CONTAINERISATION By D. S. WILKES

Hulett's South African Refineries Limited

Abstract The definition and principles of a container are

outlined. The particular application at Hulett's Refineries, Rossburgh, is cited. Overseas develop­ments are briefly outlined.

Introduction With the increasing use of containerisation as a

means of packing goods for transportation overseas, as well as in South Africa, it was thought that a worthwhile investigation would be to determine the effect of the introduction of this method of packing at the Refinery. The results obtained were suffi­ciently promising to warrant a more detailed study. It is hoped that this short paper will arouse sufficient interest to enable the Industry to be adequately pre­pared when containerisation arrives.

Definitions Before attempting to outline the effects of con­

tainerisation, it would be as well to define the subject matter.

The definition of a freight container according to the International Organisation for Standardisation1, is as follows:

"Freight container shall mean an article of trans­port equipment: (a) Of a permanent character and accordingly

strong enough to be suitable for repeated use. (b) Especially designed to facilitate the carriage

of goods, by one or more modes of transport, without intermediate reloading.

(c) Fitted with devices permitting its ready hand­ling, particularly its transfer from one mode of transport to another.

(d) Or designed as to be easy to fill and empty."

The term "freight container" includes neither vehicles nor conventional packing.

Definition of general purpose of freight container "Freight container of rectangular configuration,

weatherproof, for transporting and storing a number of unit loads, packages or bulk materials, that con­fines and protects the contents from loss and damage, then can be separated from the means of transport, handled as a unit load, and trans-shipped without rehandling the contents."

There are at present two series of containers which have been standardised upon by the international committee, and these are shown in Table I and II.

Applications These can be summarized by three major func­

tions: 1. To provide weatherproof storage. 2. To confine and protect packs. 3. To be transported by various means as a unit

load. The advantages of weatherproof storage are more

than obvious, especially when one is dealing with a perishable product like sugar. Far too often we have heard of cases in which a sudden storm caught a crew unloading a railway truck unawares or a vehicle driver forgot to take along a tarpaulin or the ship's hold could not be closed in time to prevent damage to sugar.

To confine and protect 20 metric tons of refined sugar from Durban to Walvis Bay or Durban to the Reef is no small undertaking. However, the follow­ing uncontrollable hazards no longer exist with con­tainers: (a) Theft, at present very prevalent. (b) Multiple handling, an ever-present hazard. (c) Rain and weather hazard.

The only hazard which is still present is, of course, bad hyster driving when loading and unloading, and this is surely controllable.

Hysters capable of handling 20 metric ton loads have been developed and the advantages of trans­porting 20 pallet loads with one lift are self-evident.

Specific Advantages to the Refinery Apart from the cost of raw sugar, one of the

biggest expenditures at the Refinery is packing materials and this at present exceeds Rl million rand per annum.

A considerable amount of this is necessary in order to ensure that the package is strong enough to withstand the rigours of the South African distribu­tion system.

With the introduction of containerisation, the need for this strength requirement is greatly reduced. The saving in packing materials that would be realised by the reduced strength requirements is of the order of R200,000 per annum. This is the maximum and is based on the assumption that a 2-ply valve sack and baler bag would be sufficiently strong to contain refined sugar on a container journey.

Claims involving damage to pockets and packed sugar at present cost the Refinery in excess of R20.000 per annum. When one considers that 45 per cent of the Refinery's inland despatches are trans-

Page 46

Proceedings of The South African Sugar Technologists'1 Association — June 1970 31

ported at railway risk and that all shipments coast­wise are covered separately by insurance, the total cost of damage to packed refined sugar must be enormous. In addition, the current trend is towards an increasing pre-pack tonnage and as all pre-packs are carried at Refinery risk the value of the claims on the Refinery can only increase. The total cost should be reduced by at least 80 per cent by using con­tainerised traffic.

The time-consuming practice of loading railway trucks and motor vehicles unit by unit would also be greatly reduced and with corresponding saving of labour costs.

Limitations With all these advantages, there are of course

drawbacks. Containers are not cheap items to pro­duce, and neither is the equipment to handle them. They cost approximately R2,000 each and a typical cost of a fork-lift truck is approximately R41,000. An example of the cost involved in using containers overseas is as follows:

The hiring charge for a 20-ton container shipment between depots costs R270. A period of four days loading time is granted free of charge, thereafter R2 per day or part thereof.

Overseas Development To present a brief summary of overseas develop­

ments is extremely difficult, owing to the fact that the container concept is so widespread. However, it would suffice to list some of the major overseas com­mitments: (a) The Port of London Authority R51.4 million. (b) Britain/Australia weekly service R154 million. (c) In America 80 steamship companies have to date

invested $2.5 billion and some 250,000 con­tainers are at present in daily use.

(d) In Europe the Port of Rotterdam's weekly volume of' containers in 1968 was 2,500 com-

' pared with 1,600 in 1967. (e) The shipping subsidiary of Tate & Lyle Limited

has invested R40.000 in 20 containers solely for use by the Refinery for the shipment of bulk sugar to customers.

A typical cost reduction schedule showing the effect on overseas traffic is enclosed as Appendix A.2

Before concluding, it should be noted that a modi­fication of the container concept has been introduced with a fair amount of success in Australia. This system, called the Canetainer System, involves the use of 10-ton containers for the transporting of cut cane from the field to the factory.

Acknowledgement The author wishes to record his thanks to the

Management of Hulett's S.A. Refineries for allowing him to publish some of the information included in this paper.

References 1. ISO/TC 104 (secretariat - 61) 138 F/F draft 150 recom­

mendation No. 1055. 2 Proceedings International Container Symposium Lon­

don - 1968.

TABLE I

Container Designation

1 A 1 B 1 C 1 D 1 E 1 F

Height

mm 2440 2440 2440 2440 2440 2440

Width

mm 2440 2440 2440 2440 2440 2440

Length

mm 12200 9150 6100 3050 2032 1175

Rating

m Tons 40.640 30.480 20.320 10.160 7.112 5.080

TABLE n

Container Designation

2 A 2 B 2C

Height

mm 2100 2100 2100

Width

mm 2300 2100 2300

Length

mm 2920 2400 1450

Rating

mTons 7 7 7

RATING = MAX GROSS WT.

APPENDIX A Comparison of Conventional and Container shipping costs on International trade routes to and from the United Kingdom port to

port excluding inland transport.

World Zone

South America North America Africa Middle East Far East Australia India Soviet Bloc

Conventional R. per ton

43.4 38.0 46.4 39.2 46.6 58.8 48.0 33.2

Container R. per ton

23.2 17.0 21.6 24.6 27.0 33.8 29.8 16.2

Photo—Tate & Lyle Times.

Page 47

32 Proceedings of The South African Sugar Technologists'' Association — June 1970

Discussion Mr. Collingwood: Would a container in this

country belong to the railways or to the manufac­turer?

If a twenty tone container requires twenty pallets to load it, do the pallets remain in the container?

Mr. Wilkes: The general manager of the South African Railways says that the S.A.R. will provide the containers, including the pallets.

The actual packing must be done by the con­signor.

Mr. Hoekstra: Does the type of container used for sugar limit its suitability for use for other products, i.e. for return freight?

Mr. Wilkes: Tate and Lyle used containers for bulk sugar but at this stage I think we should restrict ourselves to containers for bagged sugar, packed on pallets.

We are not responsible for filling a container for return freight.

Mr. Renton: Was containerisation in Britain de­veloped by British Railways or by private enterprise and when are the railways in this country likely to introduce such a system?

Mr. Wilkes: British Railways do not operate in the same manner as South African Railways.

The Port of London Authority started con­tainerisation between U.K. and U.S.A. and savings were such that British Railways quickly followed suit.

The South African Railways are interested in con­tainers but no date has yet been set for their intro­duction.

I understand "Bosal" exhausts are using containers for exports, but only from the dockside,

Mr. Francis: How does containerisation affect storage problems?

Mr. Wilkes: Containers do assist with storage. Using straddle trucks, they can be stacked three high.

The trucks can handle up to 42 tons and the time spent in handling freight is reduced consider­ably.

Mr. Alexander (in the chair}: The cost of con­tainers is so high that a container would be a rather expensive method of storage.

Dr. Matic: A small manufacturer may not have the equipment to unload these containers.

Mr. Wilkes: The standard container is 8 feet by 8 feet and has large doors at one end through which can be driven a hyster complete with pallet.

Mr. Allan: If the container arrived on a trailer would the trailer be left at the factory? It would be quite a problem to lift the container off the trailer.

Mr. Wilkes: There is a system in America where the container, using the truck's pneumatic system, is lifted a few inches off the truck and is supported on legs while the truck drives off.

Mr. Poree: If the consignor wants the container back he is presumably responsible for the return journey, so must he try and develop a return trade?

Mr. Wilkes: As both containers and transport will belong to the railways, there will be simply a de­murrage problem, as at present.

An outside private organisation might be used for loading containers and bringing them to a railway depot.

Page 48

Proceedings of The South African Sugar Technologists' Association — June 1970 33

FACTORY BALANCE SYMPOSIUM

THE FACTORY BALANCE S.A.S.T.A. Chemical Control Committee

Abstract The interests of the Committee in aspects of the

Factory Balance are outlined and figures given to show the financial implications of undetermined loss and non-sucrose ratio. The work of the Committee on the influence of suspended solids on mixed juice analysis, the determination of refractometer brix, and industry-wide standardisation of sampling, analysis, and reporting, is reviewed.

Introduction The importance which should be attached to the

control of loss in industry cannot be overstressed. The ability to assess when and where losses occur is a necessary forerunner to effective loss control.

When it is remembered that our industry enjoys a world-wide reputation for efficiency it is startling to note the considerable financial implications of sugar factory losses in South Africa.

What has this to do with the Chemical Control Committee?

All calculations of sugar factory losses are based on factory data for weights and analyses. It has long been realised that many of the so-called losses grouped as "undetermined" are by no means genuine. Apparent losses of sucrose are caused by errors in weighing, sampling and analysis of factory products. These fictitious sucrose losses are very much the province of chemical control.

Non-sucrose ratio* has been used as an indicator of the fate of impurities in the factory. Non-sucrose ratios vary considerably from factory to factory. This variation is important in that the ratio is an expres­sion of molasses production. A high non-sucrose ratio reflects an excessive molasses production. Yet, despite the proven parallel between N.S.R. and molasses weighed out of the factory, doubt exists as to the validity of non-sucrose ratio for indicating performance, for the figure depends upon the accuracy of the brix determination in mixed juice and molasses, analyses which do not inspire general confidence! And so non-sucrose ratio, and its larger cousin the factory brix balance, become im­portant aspects for the consideration of the Committee.

Calculations, summarised in the Appendix, indi­cate that the cost to the industry through factories losing more sucrose in molasses than the industrial average amounted to over R600,000 last season. At the same time the total cost to the industry through undetermined sucrose losses in excess of the indus­trial mean amounted to over R400,000. The latter figure can be considered a minimum, for the indus­trial average undetermined loss, 1.54%, is a figure

Non-sucrose in Sugar and Molasses * N.S.R. = — •

Non-sucrose in Mixed Juice

which an industry with a reputation for efficiency should not tolerate without an explanation. If an uncontrollable undetermined loss of 1% is taken as a basis for calculation, this cost soars to over R700,000 for the season.

Matters Considered by the Committee 1. Suspended Matter in Mixed Juice

Suspended matter can affect the official sucrose determination in at least two different ways, namely through sampling in the factory and through the analytical techniques used. When appreciable amounts of suspended matter are present in the juice, although they are weighed in their entirety, the per­forated sampling tube canted at an angle can act in a way similar to a DSM screen, selectively passing a sample richer in juice and hence in sucrose. Once having reached the laboratory, a portion of the juice is clarified and filtered, in this way removing all suspended and most colloidal matter before the two portions of juice are measured out for the Jackson and Gillis sucrose determination.

An investigation of the selectivity of the present mixed juice sampling device was undertaken by the Sugar Milling Research Institute at the request of the Committee. The findings, that the device was indeed selective against suspended matter, were accompanied by suggestions for improved sampling of mixed juice.

At the same time the Committee initiated the accumulation of data on the quantity of suspended matter in mixed juice from different factories. A method for the determination of suspended matter was devised, and this was the subject of a paper pre­sented to the 1969 Congress of this Association2. The accumulated data were used as the basis for a letter sent to the South African Sugar Association contain­ing the following recommendations:—

(1) Hourly catch samples should be taken from the mixed juice pipe leading to the weigher.

(2) Samples should be composited with mercuric chloride and analysed on a shift basis.

(3) The method of analysis using filtration2 should be used for the determination of sus­pended solids in mixed juice.

(4) The sucrose per cent in mixed juice should be determined in the normal manner by J. and G. methods on the usual four-hourly sample, but the weekly sucrose percentage should be corrected for the suspended matter determined as described above.

The recommendations of the Committee were re­ferred by the Sugar Association to the millers and growers. The discussions are still proceeding.

2. The Use of Refractometers for Factory Control Following the success of the decision by Hulett's

to adopt the refractometer in place of the spindle for the determination of brix in factory products from

Page 49

34 Proceedings of The South African Sugar Technologists' Association — June 1970

clear juice onwards, the Committee has considered recommending the use of the refractometer through­out the industry.

A problem lies in the details of the method of analysis, particularly sample preparation. Graham and MacGillivray' have indicated the extent to which suspended and colloidal matter may influence refrac­tometer readings in juices and extracts, and their work is being extended by the S.M.R.I. to include other factory products.

There is no doubt that refractometer brix gives a truer indication of the soluble solids content of a juice than spindle brix. A logical follow-up of the adoption of the refractometer from clear juice on­wards would be an extension to the complete fac­tory through changing the method of determination in mixed juice, at present defined by the Sugar Act. The Committee has suggested that parallel deter­minations of brix in mixed juice should be carried out by the two methods. This suggestion will be adopted by some factories in the 1970/71 season. The details of the exact method of sample preparation and analysis have recently been finalised by a sub­committee.

3. Standardisation of Factory Methods and Reporting The true significance of differences between fac­

tory balances can only be appreciated if the data supplied are based on standard procedures. Stan­dardisation of the method used for determining brix has already been mentioned. There are other mea­sures which have been considered by the Committee.

A recommendation has been put forward that all factories should weigh final molasses. This is an essential prerequisite for industry-wide comparisons of undetected losses and non-sucrose ratios.

The weighing of syrup is a step which may well gain favour when an investigation of losses is intensi­fied. The Committee has undertaken to "encourage" factories to weigh syrup. The current paper on weigh­ing syrup at Empangeni may, or may not, lend weight to the encouragement!

The Committee has recently initiated, through the S.M.R.I., a survey of the methods of sampling and analysis used in all factories. From the results of this survey it will be possible to make suggestions to certain factories with the object of improving standardisation throughout the industry.

Two matters relating to reporting have been dealt with by the Committee. A recommendation has been put forward that all factories should submit data on non-sucrose ratio to the S.M.R.I. for inclusion in the weekly summary of factory returns. This step has been taken because considerable differences have been found between the seasonal average non-sucrose ratios for different factories. Taking clarified juice as starting point, the N.S.R. for factories using spindle brix varied from 0.901 to 0.996, and for fac­tories using refractometer brix from 0.829 to 0.887. Non-sucrose ratio is in itself a statement of factory balance, but, while a ratio of nearly 100% may please the academic, in the case of non-sucrose ratio the lower the better! Calculation shows that the differ­ence in N.S.R. between 0.996 and 0.901 is worth 68 cents per ton of sugar to the "less well balanced"

factory. For refractometer factories the difference between 0.887 and 0.829 is worth 42 cents per ton of sugar. While it is not suggested that the mere re­porting of these data will solve the overall problem, it will be appreciated that collection of reliable data must form the first step in any methodical scientific approach to the problem.

The second item dealing with reporting may seem less directly connected with the factory balance. This was the decision, taken after long consideration, to abandon the use of Boiling House Performance.-One of the grounds on which B.H.P. was attacked was its dependence on mixed juice purity, itself influenced by the accuracy of determination of both brix and sucrose. In fact B.H.P. was intimately tied up with the accuracy of determination of factory balance.

4. Other Matters Considered by the Committee The Committee decided to send a questionnaire to

other sugar-producing countries, giving details of the "non-sucrose ratio" and "undetermined loss" prob­lems, and asking for their experience. Any pertinent information from other industries could be most useful.

Projects undertaken within the industry have been fully supported by the Committee. These have in­cluded three items to be discussed during this sym­posium, the chloride balance, solids balance, and isotope dilution method investigations, as well as research into non-sucrose constituents of juices and molasses which influence the sucrose determination.

Discussion Academic considerations apart, the factory

balance has considerable economic significance. The economic aspect can be divided into two problems which may be conveniently labelled undetermined loss and non-sucrose ratio.

It is the intention of the Committee to act as a clearing house for data received and to suggest and initiate new lines of investigation.

Not all the collection of data can be undertaken directly by the Chemical Control Committee. Some investigations may be conducted by individual members, in particular those representing the S.M.R.I. and Hulett's Research and Develop­ment, but the basic data collection will consume far more time than can be contributed by the mem­bers of the Committee. It has therefore been proposed that a technologist be appointed on a full-time basis to collect and collate statistical data and to undertake specific investigations at the Commit­tee's request.

It may seem that few of the measures mentioned in this report are likely to solve either of the major problems. Improvement to sucrose analysis of mixed juice or, more drastic, the adoption of the isotope dilution method, may reduce fictitious undetected losses, but real undetermined losses will continue to plague the industry, while above-average non-sucrose ratios will continue to reduce the profits of unfor­tunate factories.

By the application of scientific methods it should be possible, after a fair amount of reliable data

Page 50

Proceedings of The South African Sugar Technologists' Association — June 1970 35

has been accumulated through the present pro­gramme, to suggest lines of attack able to yield more positive results.

The purpose of this symposium will be well served if the discussion includes ideas on lines of investiga­tion not covered by the papers.

References 1. MacGillivray, A. W., and Graham, W. S. (1969). "Brix

Determination", Proc. S. Afr. Sug. Technol. Assoc. 43, 215-218.

2. Prince, P. A. (1969). "The Determination of Suspended Solids in Mixed Juice", Proc. S. Afr. Sug. Technol. Assoc. 43, 141-142.

APPENDIX A Calculated Loss of Revenue to the Industry

TABLE I Calculated loss of revenue for factories not attaining industrial average (8.90 %) for loss of sucrose in molasses per cent sucrose

in cane, 1969/70 season.

APPENDIX B

Economic Effect of Non-sucrose Ratio

The calculations have been based on 1,000,000 tons of cane, and the following assumptions:—

Sucrose % cane Extraction % Mixed Pol of

Juice Purity % Sugar,

Non-sucrose in Boiling House Final Molasses

°S sugar %

Recovery % Purity %

13.5 95 85 98.7 0.9

90 38

Tons sucrose in mixed juice = 1,000,000 x 0.135 x 0.95

Factory

L O P H I M J N

'Extra' Loss (over 8.90%)

0.38 0.39 0.59 0.88 1.22 1.58 1.79 2.88

To

Tons 'extra' Sucrose Lost

214 661 832 267 327

1259 2393 4054

tal 10007

Loss in Rand at R60 per ton 98.7 pol sugar

13,020 40,200 50,580 16,200 19,860 76,500

145,440 246,420

608,220

Tons brix in mixed juice 100

= 128,250 x — 85

(a) Tons non-sucrose in mixs = 150,882 - 128,250 Tons sucrose in sugar = 128,250 x 0.90

Tons sugar 100

TABLE U Calculated loss of revenue for factories not attaining industrial average (1.54%) for undetermined loss of sucrose per cent sucrose

in cane, 1969/70 season. Factory 'Extra' Loss

(Over 1.54%) Tons 'Extra' Sucrose Lost

Loss in Rand at R60 per ton 98.7 pol sugar

I J K L M N

0.50 0.81 0.98 1.00 1.22 2.50

134 1083 395 563 972

3519

Total 6666

8,160 65,840 24,020 34,250 59,060

213,900

405,230

115,425 x 98.7

(b) Tons non-sucrose in sugar = 116,945 x 0.009

(c) Non-sucrose ratio A

0.901

Note: Factories H, I, J, N, operate diffusers. TABLE JJI

Calculated loss of revenue for factories losing more than 1% of sucrose in cane 'undetermined'. 1969/70 season.

Factory 'Extra' loss (over 1.00%)

Tons 'Extra' Sucrose Lost

Loss in Rand at R60 per Ton 98.7 pol sugar

A B C D E F G H I J K L M N

0.03 0.16 0.16 0.26 0.43 0.52 0.53 0.54 1.04 1.35 1.52 1.54 1.76 3.04

31 44

333 381 523 780 260 164 279

1805 613 868

1402 4279

Total 11762

1,860 2,700

20,220 23,160 31,800 47,400 15,780 9,960

16,980 109,740 37,260 52,740 85,200

260,100

714,900

128,250

150,882

22,632

115,425

116,945

1,053

(d)

(e)

Tons non-sucrose recovered = (a x c)

Tons non-sucrose in molasses = (d - b) Tons sucrose in molasses

38 = x e

20,391

19,338

11,852

22,541

21,488

13,170 100 - 38

The difference in sucrose lost in molasses, 1,318 tons, is equivalent to 1,335 tons of 98.7 pol sugar. At R60 per ton this amounts to R80,100, or in other words:—

R0.08 per ton cane R0.68 per ton sugar.

By means of a similar calculation it can be shown that a non-sucrose ratio difference between 0.887 and 0.829 is worth:—

R0.05 per ton cane R0.42 per ton sugar.

For discussion on this Paper, see page 50.

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36 Proceedings of The South African Sugar Technologists" Association —June 1970

FACTORY BALANCE SYMPOSIUM

A FACTORY CHLORIDE BALANCE By A. W. MACG1LLIVRAY

Sugar Milling Research Institute

and

B. M. STUART Hulett's Research and Development

Abstract A chloride balance in a raw sugar factory has been

established. This balance compares favourably with the sucrose balance and could be used to detect chemical losses of sucrose. The use of chloride ions as tracers to detect losses in particular areas of the factory has been partially successful. The techniques of sampling and analysis are briefly described, and suggestions are made towards improving the accuracy of this work.

1. Introduction The discussion following the paper "Potentiometric

Determination of Chlorides in Molasses",1 at the 1969 congress, included lively comment on the use of chloride as the basis for factory balance calculations. The concept had been used with success by Davies and his co-workers" in 1941 for investigating the magnitude of sugar losses in the evaporators and pan station, and by Virginio Zanni3 in 1951, but little work has been reported since that time.

With the introduction of a quick and accurate potentiometric method for determining chloride, a routine factory chloride balance becomes a practical possibility. Chlorides are not subject to chemical destruction and, in common with other highly soluble inorganic ions can only be lost in the factory by physical removal, either through entrainment or absorption. A mass balance for chlorides over the factory should theoretically yield results approaching 100% recovery, and should definitely prove more reliable than a balance based on sucrose or total non sucrose, both of which may be altered chemically during the process.

Work has been carried out during the past season in an attempt to establish chloride balances in a raw sugar factory. This work has been partially success­ful in that a number of occasions a recovery of almost 100% was recorded over periods of two to three weeks.

At the same time at other factories, chloride was used as a tracer to pinpoint sugar losses. This pro­gramme has highlighted a number of unusual features.

The results so far are sufficiently promising to warrant continued and intensified investigation of the overall factory balance. If the techniques can be improved sufficiently to produce 100% confidence in the chloride balance, the adoption of the balance as a

routine feature of factory control may help to explain some of the anomalies of present comparative factory data.

2. Experimental 2.1 Chloride Analysis

The Metrohm Potentiograph (E.436) as described by Comrie1 was used throughout this work. AgNOa of either 0.05 or 0.IN strengths was titrated auto­matically against the various factory products, the end point being determined from the resultant milli­volt curve.

The factory products which were analysed were as follows:

(i) Mixed Juice: 15 to 20 g of juice was accu­rately weighed and diluted to 50 ml for titra­tion. The samples were not filtered before analysis and were therefore representative of the mixed juice as weighed.

(ii) Clear Juice: as for mixed juice. (iii) Filter Cake: A number of techniques were

used for this determination, none of them completely satisfactorily. At some mills it was possible to make a slurry of cake with distilled water, and titrate directly into this. At other factories this method did not give satisfactory results, and it was necessary to digest the cake with water or dilute HNOa and titrate the extract. Another technique used which gave a slightly improved titration curve was to add a known amount of chloride to the slurry before titrating.

(iv) Syrup: 4 g of syrup were weighed and diluted to about 50 ml.

(v) Sugar: 40 g of sugar were weighed and diluted to constant volume.

(vi) Molasses: 1 g of molasses was weighed and diluted to constant volume.

(vii) Stock: All products in stock were analysed for chloride at the beginning and end of each balance period,

(viii) Milk of Lime: 150 g of supernatant liquor was weighed, neutralized with HNOs and titrated directly.

2.2 Sampling Frequency 2.2.1. When a complete factory balance was being

established the various points sampled were as fol­lows:

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Proceedings of The South African Sugar Technologists' Association — June 1970 37

(i) Mixed Juice and Syrup: Both were continu­ously sampled and composited for each shift.

(ii) Filter Cake: An hourly catch sample was composited for each shift.

(iii) Sugar: Each truck was sampled and com­posited weekly.

(iv) Molasses: Each scale tip was sampled and composited weekly. No preservative was used at all.

2.2.2. During shorter tracer experiments, mixed juice, clear juice, filter cake and syrup were sampled either continuously where possible or frequent catch samples were composited for a period of four hours. In one experiment samples were composited for one week. Formaldehyde was used as a juice preserva­tive, both mercuric chloride and basic lead acetate being obviously unsuitable.

2.3 Sampling Methods 2.3.1. The normal factory samples of mixed juice,

syrup, filter cake, sugar and final molasses were used. 2.3.2. All intermediate products in stock were

sampled for chloride analysis. The difficulties en­countered in sampling the stock were:

(i) Syrup samples were not truly representative due to liquidation of the evaporators. The sample received was taken from the top of the tank and was usually of a very low brix.

(ii) Difficulties were encountered when composit­ing low grade massecuites and the crystal content of the final sample for analysis (1 g) fluctuated considerably. This produced sub­stantial variations in the chloride content of massecuites. A maximum of 17 730 ppm chloride and a minimum 16 400 ppm were determined on one massecuite.

(iii) The inaccuracy of determining accurately the quantity of solids in stock led to further errors. These factors made it difficult to determine accurately the quantity of chloride in stock and no doubt led to an undetermined chloride loss or gain.

3. Results 3.1 Example of a Chloride Balance

TABLE I Empangeni Chloride Balance

TABLE II

3.2 Undetermined Losses at Empangeni

No. of weeks Date

Type of loss Undm CI" loss/ gain % CI~ in m. juice

Undm Sue. loss/gain % Sue. in m. juice

Undm Solids loss/gain % solids inc.juice

Undm N. Sue. loss/gain % N. Sue in c. juice

2 4.11.69/

18.11.69

0.88% gain

2.55% loss

5.85% loss

21.70% loss

2 18.11.69/ 30.11.69

0.93% loss

1.14% loss

4.41% loss

19.77% loss

2 30.11.69/ 14.12.69

8.27% loss

2.73% loss

5.17% loss

17.17% loss

5 14.2.69/ 18.1.70

0.29% gain

1.33% loss

1.06% loss

0.28% gain

Total 11 4.11.69/ 18.1.70

1.33% loss

1.76% loss

3.35% loss

11.15% loss

3.3 Chloride tracer experiments at 1L and TS At these two factories an intensive investigation

was carried out in the clarification and evaporation stations. Mixed juice, clear juice and syrup were sampled continuously, or as nearly continuously as was possible, and analysed four-hourly for chloride. Filter cake was sampled hourly and a four-hourly composite was analysed.

All calculations were based on the assumption that there was no loss of chloride from the system:

Mixed Juice • ->- Clear Juice ->- Syrup

Filter Cake

except that which was removed in the filter cake. Thus, by determining the tons of chloride in the mixed juice and the filter cake, the tons of chloride in the clear juice and syrup could be calculated. From these figures, and the ratios of Pol/chloride, Brix/chloride and reducing sugar/chloride, the tons of pol, Brix and reducing sugars respectively could be deduced.

18/11/1969

Metric Tons Mixed Juice 48.662 Lime 0.010 Stock (17.11.69) 22.986

-30/11/1969

Sugar Molasses Filter Cake

Metric Tons 1.541

42.699 0.194

Stock (30.11.69) Undm. Loss

26.772 0.452

Specimen calculation

(a) Mixed Juice: Tons of mixed juice %Pol 12.07 Tons of Pol %Brix 14.45 Tons of Brix % red. sug 0.46 Tons of red. sug. % chloride 0.088 Tons of chloride

(b) Filter Cake Tons of filter cake %pol 1.49 Tons of pol

13 391.207 1 616.319 1 935.029

61.466 11.843

459.430 6.845

71.658 71.658

Undm. CI- loss % CI- in mixed juice = 0.93% % chloride

Tons of Brix 8.195 (based on purity of m.j.)

Tons of red. sug. 0.231 (based on red. sug/sucrose ratio in m.j.)

0.026 Tons of chloride 0.119

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38 Proceedings of The South African Sugar Technologists'1 Association — June 1970

(c) Clear Juice pol/CI

Brix/CI

reg. sug/CI

= 136.74 Therefore tons pol =

= 160.07 tons Brix =

46.18 tons red. sug. =

(d) Syrup pol/CI

(11.843-0.119) x 136.74 1 603.139 11.724 x 160.07 1 876.661 11.724x46.18

54.141

136.12 Therefore tons pol

Brix/CI = 159.39 tons Brix red. sug/CI = 41.25 tons red. sug.=

" - - - • • (1 616.3)9 6.335 tons

loss of pol in clarification

loss of pol in evaporation

loss of brix in clarification =

loss of brix in evaporation =

1 603.139 -7.368 tons (1 935.029-50.173 tons 1 876.661 -7.973 tons = 12.63

11.724 x 136.12 1 595.871 1 868.688 48.361

6.845)-I 603.139

1 595.871

8.195)-1 876.661

1 868.668

purity of loss in clarification purity of loss in evaporation = 92.41 loss of reducing sugars in

clarification

loss of reducing sugars in evaporation

(61.466 - 0. 7.094 tons

54.141 - 48 5.780 tons

The results of two week runs at tabulated below in table III.

TABLE III

231) - 54.141

,361

IL and TS are

Clarification

pol lost % pol in mixed juice brix lost % brix in mixed juice red. sug. lost % red. sug. in mixed juice % increase in chloride % non-sucrose

Evaporation

pol lost % pol in mixed juice brix lost % brix in mixed juice red. sug. lost % red. sug. in mixed juice

TS

1.10 gain 1.49 loss

18.24 loss 17.16

TS

0.48 loss 0.34 loss 3.80 loss

IL

0.39 loss 2.59 loss

11.54 loss 15.32

IL

0.46 loss 0.41 loss 9.40 loss

3.4. Another series of experiments were carried out in four factories simultaneously, using the normal factory analysis for pol, brix and reducing sugar, and compositing the routine factory samples for a week for chloride analysis. Each factory was studied for two weeks. The results are as follows:

TABLE IV

Clarification

pol lost % pol in mixed juice brix lost % brix in mixed juice r.s. lost % r.s. in mixed juice % increase in chloride % non-sugars

Evaporation pol lost % pol in mixed juice brix lost % brix in mixed juice r.s. lost % r.s. in mixed juice

Factory

1.41 loss 2.87 loss 6.27 gain

10.11

3.11 gain 4.13 gain 9.50 gain

B

2.07 loss 3.10 loss

10.17 gain

9.34

3.01 gain 2.19 gain 0.15 gain

0.15 loss 0.51 loss 0.45 gain

3.00

9.23 gain 8.62 gain

12.03 loss

D

3.04 loss 4.83 loss

33.32 loss

15.51

4.83 gain 4.61 gain 0.81 gain

4. Discussion In a raw sugar factory 95% of the chloride is

removed in the final molasses, whereas the majority of sucrose is removed in sugar. Any inaccuracy caused by the weighing of final molasses will influ­ence the chloride balance far more than the sucrose balance. This may be the reason why the determina­tion of a chloride balance at Felixton was unsuccess­ful. Final Molasses at Felixton is weighed in a beam balance, which is probably not as accurate as the balance at Empangeni.

Investigation has shown that the chloride content of juices obtained from cane from different areas varies considerably. The chloride in juice from mixed variety of cane from Nkwaleni averaged over 1 500 ppm representing 5.3% of non-pol solids. Variety 376 cane from Empangeni contained 900 ppm chloride, representing 3% of non-pol solids. With this varia­tion possible it is evident that the chloride content of mixed juice can fluctuate considerably over even short time intervals.

The compositing of mixed juice for chloride analysis was examined. Variation between the analysis of the composite and the average analysis of the individuals were significant. The technique of compositing is to be improved possibly with the addition of a juice preservative. Formaldehyde was found to have no effect on the chloride determina­tion.

No record was kept of the amount of water added after the mixed juice scales. This water consisted mainly of condensate, very low in chloride, and had little or no effect on the chloride balance.

Greater accuracy of the chloride analysis can be achieved by using a larger sample weight and/or a reduction in the silver nitrate normality. This should improve the accuracy of the overall balance.

At Empangeni all syrup is accurately weighed, hence it was possible to establish a chloride balance after the syrup scales. The chloric recovery from syrup to sugar and final molasses was 99.8% over a period of 6 weeks 30/11/1969 - 18/1/1970. Over the same period the sucrose recovery was only 98.74%, an undetermined loss of 1.26%.

The work which was done at IL and TS showed results which could be related to some extent with the normal factory balance over the test period. The apparent gain in pol in clear juice at TS is not explained, but is possibly due to the fact that stock changes were not taken into account in this relatively short run. At IL the loss in pol was found repre­sented approximately 50% of the undetermined loss for the test period.

The figures obtained at the other factories are much less reliable, owing to the rather extended periods over which samples were composited for chloride analysis. However, in spite of this there are some rather anomalous results which should be looked at in more detail. Factory C, for example, showed a very low increase in CI % non-sucrose during clarification. Chloride being completely soluble, this figure should provide some indication

Page 54

Proceedings of The South African Sugar Technologists' Association — June 1970 39

of the insoluble non-sucrose removal in the filter-cake. The average for the six factories investigated was 11.74% increase in chloride % N-S, whereas at factory C it was only 3%. There is some indication here that the clarification station at this factory should be investigated.

Another example is the apparent reducing sugar loss at factory D. A loss of 33.32% in reducing sugars at this particular factory represented more than 200 tons. This loss was highly unlikely to have occurred in fact, and the indication is that' the analysis is suspect. Here again further investigation is warranted.

5. Conclusion If the technique of mixed juice compositing can be

improved, representative stock stamples taken and molasses weighing perfected, a highly accurate chloride balance should be achieved.

This method of investigating a factory balance shows promise, particularly with regard to pinpoint­ing chemical losses of sucrose in particular areas of the factory. The techniques which have been used

in the investigations reported here were not suffi­ciently reliable to provide a 100% balance, but with suitable improvements in the current season it is hoped that the method can be perfected into a really useful tool in factory control.

6. Acknowledgements

The authors wish to thank the management and the personnel at the various factories involved for their assistance with sampling and analysis.

7. REFERENCES

1. Comrie, G. W., 1969. "Potentiometric Determination of Chlorides in Molasses", Proc. S. Afr. Sug. Technol. Ass. 43 (1969), 151-154 and discussion p. 155.

2. Davies, J. G., Yearwood, R. D. E., Foster, H. T., and Dunlop, J. W. T., 1942. "Undetected Losses during Evaporation and Pan Boiling", Sugar (1942), 37, 12, 29-33.

3. Zanni, V. 1951. "Determination of Sugar Losses in Juice Concentration, using the Chloride Method" (1951), Azucar, 3, 43-45.

For discussion on this Paper, see page 50.

•

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40 Proceedings of The South African Sugar Technologists' Association — June 1970

FACTORY BALANCE SYMPOSIUM

A SOLIDS BALANCE INVESTIGATION By E. L. MULLER

Hulett's S.A. Sugar Mills and Estates Limited

Abstract This paper is an abridged version of a thesis which

was submitted to the Sugar Milling Research Insti­tute in accordance with the requirements for the Sugar Technology Course.

The objectives of the thesis were to assess the magnitude and significance of errors inherent in the various methods of brix determination, and to investi­gate a method for calculating a true solids balance in a raw cane sugar factory. The methods of analysis and the facts revealed by the literature survey have been omitted from this paper.

Introduction Brix is a parameter of major importance to fac­

tory control. This investigation was undertaken to assess the magnitude and significance of errors inherent in the various methods of brix determina­tion.

A literature survey which was carried out revealed that a number of investigators throughout the world have looked into the problems associated with brix determinations. The effects of suspended solids, dilu­tion, different techniques of oven drying, etc., have been related to the densimetric and refractometric methods of determining the dissolved solids in fac­tory materials.

It might be justifiable to say that a comparison of methods for determining dissolved solids is un­necessary, since a vast amount of research has already been done in this field. Also, most investigators have been led to the same conclusions, that is, most methods for determining brix are influenced by fac­tors such as suspended solids, non-sugars, etc., and that these factors introduce an error into factory control.

However, the erroneous influence that these fac­tors have on factory calculations and performances has never been examined in any great detail. Examination in detail is therefore the aim and scope of the investigation.

The determination of total solids in factory materials thus enables a solids balance to be made. The procedure which has been adopted for this balance is based on:—

Solids Entering Factory Solids Leaving Factory

Total solids in Mixed Juice Solids in Filter Cake solids in Lime added Solids in Molasses solids in Phosphate

added Solids in Sugar solids in Flocculant

added solids in Bagacillo

added

Due to the relatively small quantity of moisture in the chemicals added, the weights of these materials, as recorded by the factory, have been used.

The investigation was carried out at Darnall where the vacuum flotation clarification process was in use.

The Brix Balance In other countries, e.g. Java, an attempt was made

to introduce a brix balance by assuming no loss of sucrose during clarification, other than in filter cake. Despite the shortcomings of this method as used in Java, it is applied in the Hulett mills and recently there was an occurence at Empangeni which proved its value beyond any doubt.

For a number of years, the "non-Sucrose Ratio" as defined by Perk',J has found a rather strong following.

Non-Sucrose Ratio=

Tons non-sucrose in final molasses + tons non-sucrose in sugar

Tons non-sucrose in mixed juice

Tons sucrose in mixed juice Tons sucrose in sugar Tons sucrose in molasses Tons sucrose in combined losses Tons brix in mixed juice Tons brix in sugar Tons brix in molasses Tons brix in combined losses

= J = S = M = L = ] = s = m = c

Then: (s+m—S—M)

Non-Sucrose Ratio= s+m+c—S—M—L

(s+m—S—M)

(s+m—S—M)+c—L

Substituting W=(s+m—S—M)

W Non-Sucrose Ratio =

W+c—L The value of W and L are determined fairly

accurately and, moreover, are more or less constant quantities. Obviously, variations in the non-sucrose ratio are caused by variations in "c" (tons brix in combined losses).

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Proceedings of The South African Sugar Technologists' Association — June 1970 41

Assume: S =75 Normal factory with 2.35% s =76 loss in cake+undetermined, M = 8 89% B.H.R. L =2 40 purity final molasses m = 2 0

For a Non-Sucrose Ratio = 0.9.

W 13

W + c — L 13—2 + c c=3.44%

For a Non-Sucrose Ratio=0.8 W 13

W + c — L 13—2+c c=5.25%

It is therefore submitted that an evaluation of the brix loss will give a better understanding of factory performance than does the present non-sucrose ratio, although it is not suggested that the N-S ratio be discarded.

In the following report, one must differentiate be­tween a brix balance and a solids balance as the latter includes all suspended (insoluble) solids.

Solids in Mixed Juice Solids in mixed juice is the starting point of the

solids balance and the accuracy of the balance there­fore depends to a great extent on the determination of this factor.

Sampling of Mixed Juice The determination of total solids in mixed juice

entails two separate analyses. Firstly, dissolved solids on filtered juice, which can be found by a number of methods and, secondly, suspended solids. The accuracy of the latter determination is more depen­dent upon the sampling procedure than the actual method of analysis.

The mixed juice sampling device recommended for use in South African factories1 does not give a repre­sentative distribution of sand and other insoluble material in the final sample. Two reasons can be given for this:

(a) If there is not sufficient turbulence in the scale tank before it tips, most of the heavy suspended particles will settle to the bottom of the tank. When the tank empties the juice which reaches the sampling tube first, will contain the greater proportion of sand, yet will represent only an insignificant portion of the total sample.

(b) The tube itself can be compared to a D.S.M. screen, especially if the holes are canted to one side to regulate the quantity of juice obtained per tip. It must be remembered that the recom­mended tube' consists of 15 holes, each 3/32" diameter x 1" pitch. Thus, a large pro­portion of the sand is deflected away from the tube.

To obtain a representative hourly sample, an en­tirely new sampling device would have to be em­ployed. However, at the time of the investigation no such device was available. The necessity for an hourly representative sample becomes apparent in the solids balance when one calculates the tons of total solids in mixed juice, i.e. Tons suspended solids+Tons dissolved solids.

The same problem exists when weighing out the juice for the analysis of suspended solids, i.e. the difficulty to ensure an even distribution of insoluble material in the 200 g taken.

At the time of the investigation, there remained no choice but to analyse the sample as received by the available system. More attention will be drawn to this at a later stage in this paper.

Solids in Other Material Added a. Lime

It is difficult to assess, from one week to the next, the quantity of lime consumed by the process. How­ever a fairly accurate estimation can be made of the weight of lime used over a period of one month.

Also, the quantity of solids in lime added is rela­tively small compared to the total solids in mixed juice. (Solids in Lime % Solids in Mixed Juice= 0.4%).

Thus one can use the monthly estimated weight of lime without introducing any significant error in the solids balance.

b. Mono-Calcium Phosphate This material is delivered in bags of known weight,

and an accurate account of the number of bags used per shift is kept.

Solids in M.C.P. % Solids in Mixed Juice amounts to 0.17%. With an accurate monthly weight of M.C.P. available, the quantity of solids added in this material is easily arrived at.

c. Flocculant The addition of this material is likewise care­

fully controlled, and amounts only to 0.004% of the solids in mixed juice.

Again the consumption of flocculant is known to the pound and this facilitates its use in the solids balance.

d. Bagacillo This material is added to the muds leaving the

clarifiers and although it was possible to measure the flow rate of the bagacillo in pounds per minute, a more reliable method of determining the quantity added had to be found.

The method finally decided upon is as follows: The dry bagacillo content of the mixed juice varies

only slightly from hour to hour. By analysing the mixed juice for dry bagacillo per cent a fairly accurate average can be found.

The same applies to the bagacillo content of the filter cake. Assuming that the bagacillo content of clear juice is negligible, the difference between baga­cillo in filter cake and bagacillo in mixed juice will

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42 Proceedings of The South African Sugar Technologists Association — June 1970

2. The average suspended solids per cent mixed juice is also applied to the factory recorded weight of mixed juice. (This analysis has since become part of the daily routine carried out at all Hulett factories.)

3. The average dry bagacillo per cent filter cake is used to estimate the quantity of bagacillo added to the muds from the factory recorded weight of filter cake.

4. An average figure for dry bagacillo per cent mixed juice enables one to apply this figure to the factory recorded weight of mixed juice.

Analysis of Mixed .Juice

give the amount of bagacillo added to the muds. This method is dependent on a reliable weight of filter cake.

The solids in the filtrate do not have to be taken into account as they are re-cycled continuously.

Solids in Material Leaving the Factory a. Solids in Filter Cake

The determination of solids in filter cake necessi­tates both weighing the material and analysing for moisture. Unfortunately, no factories weigh all their filter cake but estimate the total output by weighing an occasional S.A.R. truck and road transport vehicle. The method in use at Darnall is as follows:

An individual truck or lorry is weighed every tenth time it collects filter cake and a record of the number of loads is kept. The average weight of every tenth load is taken as the weight per individual load. Although it is not accurate, this method had to be used for calculating the total solids balance. If this weight is overestimated then the total solids lost in undetermined will, of course, be underestimated, and vice versa.

b. Solids in Sugar Due to the fact that the sugar is weighed accurately

and that moisture determinations are done on samples from each truckload no difficulties are found in cal­culating tons of solids in sugar leaving the factory.

c. Solids in Molasses The determination of solids in final molasses is

done on a weekly composite sample using the Karl Fischer8-'''• 1 0 ' u titrimetric moisture method. The analyses are done weekly by the staff of the Hulett's Central Laboratory.

Solids in Stock The impossibility of determining accurately the

quantity of solids in stock, necessitates the use of "Made and Estimated" figures for sugar and molasses.

Errors are frequently made in estimating the weekly stock and these will therefore give erroneous figures for solids in sugar and molasses made and estimated. However, by doing a solids balance on the monthly or to-date figures one can minimise the effect of these stock errors. Moreover they are, eventually, self-correcting.

Results of Investigation The methods used in this investigation for calculat­

ing the total solids balance relies on the application of factors to the monthly or to-date figures supplied by the factory.

These factors are as follows: 1. The average difference between factory re­

corded mixed juice brix (spindle) and dry sub­stance per cent filtered mixed juice. This enables one to arrive at an estimated dry substance per cent filtered mixed juice from the factory figures.

No. of Analyses

60

Spindle Brix

Filtered

12.80

Un-filtered

12.96

Dry Subs /o

Filtered M.J.

12.79

Suspen­ded

Solids % M.J.

0.37

Dry Baga­cillo

% M.J.

0.06

Spindle Brix

Record­ed by

Factory

13.08

These figures are the arithmetic means obtained during the period of investigation. The last column shows the weighted mean brix recorded by the fac­tory during the same period.

The disparity between the factory figure (13.08) and that recorded by the author (12.96) is due to two factors:

1. The hydrometer used by Darnall was checked against an S.M.R.I. calibrated spindle and found to be 0.1° out.

2. The technique used by the testers was found to be incorrect. They immersed the spindle into the jar as soon as the vessel was filled. This procedure leads to air bubbles adhering to the hydrometer.

This difference of 0.12 was consistent with each hourly sample and is therefore not due to the fact that the one figure is an arithmetic mean, while the other is a weighted mean.

Analysis of Filter Cake

Bagacillo

Moisture %

56.0

Rate of Addition

65 lb/min.

Filter Cake

Dry Bagacillo %

8.66

No. of

Tests

25

Filter cake was analysed for moisture in parallel with the laboratory and no difference was found. A check was made on the amount of evaporation occur­ring from the filter cake between the sampling point and the weighbridge. This was found to be negligible and only occurred from the top layer of cake in the truck. Thus, the mill figures for moisture per cent cake are used in the solids balance.

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Proceedings of The South African Sugar Technologists' Association — June 1970 43

It was stated previously that in the solids balance, the quantity of dry bagacillo added to the muds is found by difference, i.e.:

Tons dry bagacillo added = Tons dry bagacillo in filter cake - Tons dry bagacillo in mixed juice.

To check the accuracy of this assumption, one can compare the quantity of bagacillo found by measur­ing the rate of addition (65 lb. per minute), with that found by analysing the filter cake for dry bagacillo per cent (8.66%)- The latter figure should be greater than the former because of the bagacillo already con­tained in the mixed juice.

In fact, the difference between the two figures should equal the quantity of bagacillo in mixed juice (0.06% on juice).

The following figures will illustrate the above check on the accuracy:

Darnall—August 1968: Tons mixed juice=184 776 Tons filter cake= 7 866

By Analysis Tons dry bagacillo in filter=

8.66

100 x 7 866 = 681 tons

Tons dry bagacillo in mixed juice= 0.06

x 184 776 = l l l t o n s 100

By difference tons bagacillo added ... = 570tons

By Measuring the Rate of Addition 65 lb. per minute at 56.0% moisture

is equivalent to 590tons Difference 20tons A similar calculation for September gives a dif­

ference of 16 tons. We can therefore accept the analysis figures to be

sufficiently accurate for the purposes of a monthly solids balance.

Calculation of the Solids Balance The complete method of calculation is given in

Annexure I. The results of this typical example are as follows:

Solids In Mixed Juice:

Suspended Solids

Dry Substance Chemicals:

Lime Mono-calcium

Phosphate Separan

Bagacillo

684 23 343

95

42 1

570

Solids Out

Filter Cake . 1 862 Molasses ... 4 209 Sugar ... 17 883

Total (Tons) 24 735 23 954

Undetermined Solids Lost: 781 tons. Undetermined solids lost per cent solids in clarified

juice=3.41%. The factory reported the following losses for the

same period: Per cent in

Tons Clarified Juice Brix 848 3.65 Sucrose 398 2.01

Discussion of Results At the outset of this investigation it was realised

that it would be difficult to draw concrete conclusions from the results obtained. However, it was felt that an investigation would at least reveal the short­comings in more detail and thus provide sufficient information to enable us to orientate our way of thinking towards establishing a more reliable system for tracing losses in the factory.

The results of the balances are difficult to evaluate and lead one to a choice of two conclusions:

(a) The solids balance is as inaccurate as the simple brix balance as applied in all the Hulett mills.

(b) The solids balance, despite being more accurate analytically (because it is based on dry substance), has nevertheless given answers which are, for all practical purposes, the same as the brix balance. This, therefore, seems to indicate that both methods have the same degree of reliability.

Due to the following reasons, the former conclu­sion seems the more likely one:

1. It was mentioned earlier that the determination of suspended solids per cent mixed juice was known to be inaccurate due to the sampling procedure employed.

2. The weight of filter cake is more of an estimate than a true weight and can influence the final results considerably.

3. The application of "factors" to the Mill Report Sheets can only lead to reliable results if they are determined over a long period. That is, they should result from routine analyses so as to obtain weighted averages for the period under consideration.

4. The brix balance as applied in the Hulett mills assumes no loss of sucrose during clarification, other than in filter cake: Then: Tons sucrose in clear juice=tons sucrose in mixed juice - tons sucrose in filter cake. Tons brix in clear juice=

tons sucrose in clear juice x 100

purity of clear juice These assumptions clearly give rise to the fol­lowing inaccuracies: (a) Losses of sucrose do occur during clarifica­

tion and the magnitude of these losses can differ widely from factory to factory.

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44 Proceedings of The South African Sugar Technologists' Association—June 1970

(b) ft is known that the presence of large quan­tities of insoluble solids cause an error in the determination of sucrose in mixed juice, and this error is carried forward into the brix balance.

(c) An apparent purity of clear juice (i.e. pol/ brix ratio) is used to calculate the tons of brix in clear juice.

It would appear that our measuring tools have be­come too crude for this investigation and that the increase in factory efficiency has gone beyond the point of reliable information.

Conclusions Although a step in the right direction has been

taken by using dry substance instead of specific gravities and refractive indices, the solids balance, as presented in this report, requires refinement.

Empangeni Mill now lends itself to a more reliable investigation due to the following:

1. A sampling device has been designed and installed at Empangeni to give a representative sample of mixed juice for the determination of suspended solids.

2. A rilTler apparatus has been designed and tested to enable sub-sampling of the mixed juice sample.

3. Empangeni has installed a Servo-Balans to weigh syrup.

A point to bear in mind is the possible introduc­tion of the new cane payment system in South Africa. This system would make the water scales available for syrup weighing and once the syrup sampling problems have been solved, one would know what quantity of material is entering the boiling house.

If any further work is envisaged on this project, the following recommendations are tentatively put forward:

1. All analyses must be done on a routine basis so as to obtain weighted averages.

2. Filter cake must be weighed. 3. Correct sampling procedures must be adopted. 4. Syrup scales must be installed. 5. At present, it is doubtful whether any existing

laboratory staff could handle the extra work load entailed and one would therefore require extra staff.

In view of these last-mentioned factors, an analogy to Lost Absolute Juice % Fibre is being sought for application in the boiling house. That is, one must attempt to express the sucrose losses in terms of a substance which remains a constant quantity (other than that which is actually lost) such as fibre in the milling tandem. At present, an investigation is being conducted by Hulett's Research and Develop­ment Department into the feasibility of a chloride ion balance.

If this proves successful, it will be possible to ex­press sucrose as a ratio to chloride in all factory materials thus enabling one to pinpoint any losses.

Acknowledgements I wish to place on record my thanks to the Direc­

tors of Hulett's S.A. Sugar Mills and Estates Limited for permission to publish process records and other data used in this paper.

I am particularly indebted to Mr. J. B. Alexander, Research and Development Consultant, and to Mr. R P. Jennings, Chief Research Chemist, for their valued counsel on many occasions.

References Although all these references are not used in this abridged

report, they are given for the convenience of those wishing to make use of them.

1. Laboratory Manual for South African Sugar Factories, S.A.S.T.A., 1962.

2. Clayton, J. L. "Brix and Purity of Raw Juices." Proc. 26th Conference, Q.S.S.C.T., 1959, p. 131.

3. Deicke, R. "Preliminary Investigations into the Influence of Suspended Solids on the Brix of First Expressed Juice." Proc. 25th Conference, Q.S.S.C.T., 1958, p. 159.

4. Laboratory Manual for Queensland Sugar Mills, 4th Edition, Bur Sug. Expt. Stns., 1961, p. 57.

5. Clayton, J. L. "Refractometer Brix for Factory Con­trol." Proc. 29th Conference, Q.S.S.C.T., 1962, p. 235.

6. Jensen, E. D. "A Comparison of Methods for the De­termination of Dissolved Solids." Proc. 29th Conference, Q.S.S.C.T., 1962, p. 227.

7. Graham, W. S., and MacGillivray, A. W. "The Deter­mination of Brix." Proc. 43rd Congress, S.A.S.T.A., 1969.

8. Honig, P., and Sattler, L. "Determination of Water in Molasses." I.S.J., Vol. LVIII, 1956, p. 92.

9. Douwes Dekker, K. "The Composition of South African Final Molasses." Proc. 31st Congress, S.A.S.T.A., 1957, p. 92.

10. Zerban, F. W. "Determination of Moisture in Sugar Solutions with the Karl Fischer Reagent." Ind. Eng. Chem., Anal. Ed., Feb. 1946, p. 138.

11. Oosthuizen, D. M. "The Determination of Water in Raw Sugar Using the Karl Fischer Method." Proc. 43rd Congress, S.A.S.T.A. 1969.

12. Relf, E. T. "Determination of Dry Substance in Molasses and Massecuites." Proc. 25th Conference, Q.S.S.C.T., 1958, p. 189.

13. Smart, S. G., and Mitchell, J. J. I.C.U.M.S.A. Report, I.S.J. 52, p. 244.

14. Vandenberg, H. "The Application of a 'Dirt-Correction' Factor when using Juice Scales." Proc. 20th Conference, Q.S.S.C.T., 1953, p. 95.

15. Douwes Dekker, K., and Laubscher, P. J. "The Effect of Removing Bagacillo from Mixed Juice on Sugar Manufacture." Proc. 25th Congress, S.A.S.T.A., 1951, p. 57.

16. Anon. "Comparison of the Results obtained on 'Muddy' juice samples by the Official Jackson and Gillis method No. 4 for the determination of sucrose in Mixed Juice with the Normal Weight Method." Annual Re­port, Sugar Milling Research Institute (S.A.), 1955, p. 15.

17. Smith, N. "1936 Seasonal Investigation on Hot and Cold Liming." Bur. Sug. Expt. Stns. Tech. Comm., No. 3, 1937.

18. Wright P. G. "Removal of Suspended Solids from Mixed Juice." Proc. 26th Conference, Q.S.S.C.T., 1959, p. 177.

19. Perk, Charles G. M. "Forty-first Annual Summary of Laboratory Results." Proc. 40th Congress, S.A.S.T.A., 1966.

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Proceedings of The South African Sugar Technologists' Association — June 1970 45

ANNEXURE I

CALCULATION OF THE SOLIDS BALANCE

The following factors are applied in the calculation :

1. The difference between factory recorded spindle brix and dry substance % filtered mixed juice = 13.08 — 12.79 = 0.29 2. Suspended Solids % Mixed Juice 0.37 3. Dry Bagacillo % Filter Cake 8.66 4. Dry Bagacillo % Mixed Juice 0.06

Although many balances were calculated, the following is given as a typical example.

BALANCE FOR DARNALL — AUGUST 1968

The complete method of calculation is given in this example:

(a) Factory figures from Monthly Report Sheet Tons Mixed Juice weighed 184 776 Tons filter cake 7 866 Tons lime 95 Tons Mono-Calcium Phosphate 42 Tons Separan 1 Tons Sugar made and estimated 17 959 Tons Molasses made and estimated 5 231 Mixed juice spindle brix 12.97 Moisture % sugar 0.423 Karl Fischer solids % Molasses 80.47 Moisture % filter cake 76.33

(b) Estimated Figures Dry substance % filtered mixed juice = 12.97-0.29 12.68

(c) Calculation of Balance 0.37

(1) Tons suspended solids in mixed juice = x 184 776 = 684 100

(2) Tons actual mixed juice = tons mixed juice weighed - tons of suspended solids = 184 776 - 684 == 184 092 12.68

(3) Tons dry substance = estimated dry substance % mixed juice x (2) = x 184 092 = 23 343 100

(4) Tons total solids in mixed juice = tons dry substance + tons suspended solids = (3) + (1) = 23 343 + 684 = 24 027 8.66

(5) Tons dry bagacillo in filter cake == dry bagacillo % filter cake x tons filter cake = x 7 866 = 681 100

0.06 (6) Tons dry bagacillo in mixed juice = dry bagacillo % mixed juice x tons mixed juice weighed = x 184 776 = 111

100 (7) Tons dry bagacillo added to the mud = (5)- (6) = 681 - 111 = 570

(8) Tons total solids into clarifiers = total solids in mixed juice + tons lime + tons mono-calcium phosphate + tons Separan = 24 027 + 9 5 + 4 2 + 1 = 24165

76.33 (9) Tons solids in filter cake = tons cake - tons moisture in cake = 7 866 x 7 866 = 1 862

100 (10) Tons solids in mud leaving the clarifiers = Tons solids in filter cake - tons dry bagacillo added to mud = 1 862 - 570 = 1 292

(11) Tons solids in clear juice = tons solids into clarifiers (8) - tons solids in mud (10) = 24 165 - 1 292 .. .. = 22 873 80.47

(12) Tons solids in Molasses made and estimated = x 5 231 = 4 209 100

0.423 (13) Tons solids in sugar made and estimated = 17 959 - ( x 17 959) = 17 883

100 (14) Solids In Solids Out

Mixed Juice : Suspended solids 684 Filter Cake 1 862 Dry Substance 23 343 Molasses 4 209

Chemicals : Lime 95 Sugar 17 883 M.C.P. 42 Separan 1

Bagacillo 570

Total 24 735 23 954 Undetermined Solids lost = 781 tons.

The factory reported the following losses for this period Tons % in Clear Juice

Brix 848 3.65 Sucrose 398 2.01

For discussion on this Paper, see page 50.

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46 Proceedings of The South African Sugar Technologists'' Association — June 1970

FACTORY BALANCE SYMPOSIUM

SYRUP WEIGHING AT EMPANGENI By R. D. ARCHIBALD and M. A. KARLSON

Hulett's S.A. Sugar Mills & Estates, Ltd., Empangeni

Abstract In an attempt to locate untraced sucrose losses, a

Servo Balans was installed at Empangeni factory to weigh syrup. Over a twelve-week period the un­traced sucrose loss between mixed juice and syrup amounted to 181 tons, and the loss after syrup to 836 tons.

Introduction If an accurate weight and analysis of syrup is

known, the factory can be broken into two sections, and sucrose losses divided between 'clarification/ evaporation' and 'crystallisation'.

Empangeni factory experienced persistently high untraced losses during both the 1968/69 and 1969/70 seasons. Attempts were made to discover the cause of these losses, using both conventional and uncon­ventional techniques. All efforts were unsuccessful; the untraced loss remained untraced.

The decision was taken during the first week of October, 1969, to install a scale in the factory for weighing syrup. A suitably sized Servo Balans was located at Triangle. The dismantling, transport, servicing, and installation of the scale was achieved almost without a hitch, and the system was opera­tional by 10th November, 1969.

Equipment, Sampling and Analysis Syrup was weighed by means of a fully automatic,

100 ton per hour, Servo Balans.

The sample was taken from the scale discharge, using a perforated |" OD brass tube canted at an angle, and placed in such a way that the holes covered the entire width of the scale discharge. The device was virtually identical to that recommended for sampling mixed juice'.

The hot syrup was cooled by means of an Alfa Laval type P20 plate heat exchanger, which has a designed capacity equivalent to 20 gallons of syrup per hour. The cooled sample was collected in covered stainless steel buckets.

The samples were analysed for refractometer brix and pol." A series of comparisons was made between pol and true sucrose analyses, but the differences found were insignificant.

Although the scale had not been assized after transportation and erection, it was checked by pump­ing water in series through the syrup and imbibition scales. The total difference over a series of 100 tips was only 500 lbs, representing an error of 0.2%. This is within the 0.25% tolerance of the scale.

Results In Table 1 the actual tons of sucrose in weighed

syrup from week to week are compared with the tons of sucrose in syrup calculated from figures for mixed juice and filter cake. The Table also shows the un­traced sucrose loss for the whole factory, expressed as a percentage of sucrose in mixed juice.

TABLE 1

Tons of sucrose in syrup

Factory week No.

26 27 28 29 30 31 32 33 34 35 36 37

Total/ Average:

Tons weighed

3523.1 3282.7 3074.2 3333.9 2552.6 3359.4 3563.1 3024.5 3056.8 2931.7 2711.5 2203.0

36616.5

sucrose in syrup calculated

3409.5 3276.0 3013.5 3340.4 2584.5 3369.0 3557.1 3150.4 3065.9 2920.4 2739.8 2371.4

36797.9

Difference % (on Calculated)

+ 3.33 + 0.20 + 2.01 - 0 1 9 -1 .23 -0 .28 + 0.17 -4 .00 -0 .30 + 0.39 - 1.03 -7 .10

- 0 . 4 9

Factory Undetected loss %

2.22 1.44 3.83 0 1.87 1.40 0.77* 4.27 5.21 1.29 6.48 5.75

2.75

* undetected gain. Calculated tons sucrose in syrup = tons sucrose in mixed juice -tons sucrose in filter cake + tons sucrose in previous clear juice stock — tons sucrose in present clear juice stock — tons sucrose in clear juice used for B sugar magma.

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Proceedings of The South African Sugar Technologists' Association — June 1970 47

Discussion Over a twelve-week period, the tonnage of sucrose

in mixed juice was 36,970 tons. Of this amount 1,017 tons was lost 'untraced'. ? * -*- .;"

Over the same period the difference between the weighed and calculated tonnage of sucrose in syrup was 181 tons. £>- ^ *V

It would appear that, although there is some loss of sucrose prior to the syrup scale, a more substantial loss occurs during the crystallisation process. Over the period in question the untraced loss of sucrose after the syrup scale amounted to 836 tons, an average of 70 tons per week.

Routine laboratory measurements showed that mixed juice entering the factory during the period from week 26 to week 37 contained 1,431 tons of suspended matter. This inflated the tons of sucrose in mixed juice by 160 tons. Because of an inefficient sampling method this figure is certainly an under­estimate, but even so, suspended matter accounts for

over 88% of the 'untraced sucrose loss' before the syrup scale. Chemical losses of sucrose in the clari-fiers must also be considered.

Losses during crystallisation are less easy to explain. The answer may well lie in the destruction of sucrose in the crystallisers themselves, and to a lesser extent in the pans. The danger of losses of this type was stressed by Mr. Frank Chapman at a recent meeting of this Association.

The week-to-week fluctuations in the differences between weighed and calculated sucrose in syrup are a cause for concern. This matter will be investigated during the 1970/71 season, both at Empangeni and at Amatikulu, where it is hoped to install Hulett's second syrup scale.

Reference 1. Laboratory Manual for South African Sugar Factories,

published (1962) by S. Afr. Sug. Technol. Ass. pp. 33-34.

For discussion on this Paper, see page 50.

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48 Proceedings of The South African Sugar Technologists' Association — June 1970

FACTORY BALANCE SYMPOSIUM

DKY SOLIDS, SPINDLE AND REFRACTIVE BRIX DATA By G. D. McGRATH

The Tongaat Sugar Company Limited

prior to taking the readings. All readings were made at 20° C.

Results and Discussion The results of the spindle and refractometer brix

measurements are shown in Figure 1. The spindle brix follows a general rise until week number 18 is reached after which it follows a general downward trend which levels off before the end of the season. The refractometer brix was more nearly constant but showed a rise towards the end of the season when attempts were being made in the factory to produce a higher brix final molasses. The difference between these two parameters is shown in Figure 2. This difference increased from the initial values of about 2.5 units to a maximum of more than seven units and finally decreased to three units at the end of the season. Consequently it is apparent that refractometer brix measurements may not be used

2 7 12 17 22 27 32 37 42

WEEK NUMBER

FIGURE It Spindle and refractometer brix measurements of final molasses for 42 weeks.

It was found that the difference between spindle and refractometer brix of final molasses was not con­stant during the crushing season but no explanation for this has been given. The difference between re­fractometer brix and dry solids was usually about three units, but the difference between spindle brix and dry solids which was much larger also varied considerably.

Experimental Analyses of spindle and refractometer brix as well

as of dry solids were carried out on weekly composite samples of final molasses over the 1969/70 season. Spindle brix and dry solids were determined by the methods given in the Laboratory Manual for South African Sugar Factories. Refractometer brix was measured on samples which had been diluted one to one by weight with distilled water and filtered through S & S type 613 filter paper using filter aid

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Proceedings of The South African Sugar Technologists' Association — June 1970 49

17 22 27

WEEK NUMBER

FIGURE 2: Difference between spindle and refractometer brix measurements for 42 weeks.

11

B R

F F E R E N C E

SPINDLE BRIX -SOLIDS

17 22

WEEK NUMBER FIGURE 3: Spindle and refractometer brix compared with dry solids measurements for 42 weeks.

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50 Proceedings of The South African Sugar Technologists' Association —June 1970

to control the brix of final molasses within specifica­tions which are defined in terms of spindle brix.

Attempts have been made to relate the magnitude of the difference between spindle and refractometer brix with properties of the molasses such as purity, reducing sugars content, non-sugars content, etc., but no clear pattern has emerged.

Finally the brix data are compared with dry solids in Figure 3. Over a large part of the season the dif­ference between refractometer brix and dry solids remained close to three units but the difference between spindle brix and dry solids was very much greater and also showed bigger variations in this difference.

Discussion In the non-sucrose balance the non-sugar re­

moval during clarification is normally not take'n into account. However, it is considered that defeca­tion is mainly a removal of suspended solids and that any removal of soluble non-sugars is negligible. For this reason a gap in the non-sucrose balance is most likely due to analytical errors, which are at present still unknown.

The reliability of our present data could be checked by applying the Monte Carlo technique, in which the actual data are compared with a ran­domly generated uniform distribution. If the prac­tical results are of the same order as those obtained from the randomly generated distribution the results can be regarded as valueless.

Consideration should be given to whether the sucrose balance or the brix balance shows the greater inaccuracy. At present the latter is the most suspect, but research will be carried out into the isotope dilution method and the pol determinations will be compared with the sucrose value obtained by this new technique.

Recently the factory balances for brix and sucrose have been compared with the chloride balance. The chloride determination itself was considered suffi­ciently accurate by most investigators, but the largest errors are likely to be in the weighing and sampling of molasses. This has to be very reliable as 95% of the chloride ion leaves the factory in the molasses.

If the brix determinations are carried out by spindle measurement, the non-sucrose ratio is ap­proximately 80%. Using the refractometer, which is considered to be more accurate, the value obtained drops to 70% and even lower when using dry solids

determinations. This is a clear indication that the analytical methods are not fully reliable.

At the moment non-sucrose balances are related to mixed juice, but the values obtained will vary with the suspended matter. For this reason it might be decided in future to use only filtered mixed juice for analyses.

In reporting data, too many dedcimal places should not be given, particularly if the accuracy of the analysis is considered doubtful.

In connection with the syrup weighing at Empan-geni there appear to be deviations of more than 1 % between juice and syrup. These differences obviously cannot be explained by wrong stock taking and sampling errors are most likely.

If the non-sucrose ratio is expressed in terms of monetary value it can be stated that 1 % absolute is equal to R0.08 per ton of sugar, which is high com­pared to bonuses or penalties for sugar quality, which are of the order of R0.02 per ton of sugar. For this reason more knowledge on the determina­tion or meaning of the non-sucrose ratio is im­portant. In Hulett's factories the figure varies between 67-89%.

According to Tate and Lyle, sucrose in molasses is on the average 3% absolute too high if compared with the C14 technique.

If this is correct the non-sucrose balance will im­prove, but the undetermined losses will increase.

Kestoses are dextra rotrary and show identical be­haviours in acid and enzymic hydrolysis.

Inversion cannot be proved from reducing sugar ratio as this normally decreases during the process in the factory but other sucrose degradation might take place. It is, however, possible to determine the effect of retention time of juice on sucrose concentra­tion or pol in laboratory experiments. This can be done under variable conditions of time, temperature and pH.

At Empangeni it was indicated that losses occurred after the syrup stage. For this reason more investiga­tions have to be carried out into sucrose losses dur­ing boiling and crystallizing. In the refinery of Hulsar, A-massecuites showed a significant relation between the temperature at which the strike was dropped and the drop in purity of massecuite during crystallization. The same result was found at Jaag-baan for C-massecuite.

It is the opinion of Tate and Lyle Technical Ser­vices that a large part of the sucrose losses in South African factories takes place during the long reten­tion of crystallized products.

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Proceedings of The South African Sugar Technologists' Association — June 1970 51

SOME IMPRESSIONS OF THE SUGAR INDUSTRIES OF MAURITIUS AND REUNION

By J. R. GUNN

The Tongaat Sugar Company Limited

During September 1969 the author visited both Mauritius with peaks not much higher than 1 000 latest technical developments on those two islands. The first comment that must be made is that at both places the hospitality of the officials of the sugar companies is overwhelming and there is real evi­dence of great progress in their industries. There is also a tremendous contrast between the two islands both in geophysical nature and in economic back­ground. Reunion, with its tallest peak of 3 069 metres, has a very high labour wage whereas Mauritius and Reunion for a short survey of the metres still benefits from relatively lower labour costs. Sugar from Reunion is sold in the European Com­mon Market at a high price because that island is considered to be part of metropolitan France and, of course, at the moment, Mauritius has the advan­tage of British Commonwealth preference price.

Milling

On both islands the cane is delivered to the mills in a spotless trash-free condition and it has not been found necessary to install high vertical feeding hop­pers to assist feeding the mills. A number of the mills which were visited successfully employed high­speed rubber belts as inter-carriers. The mill mana­gers claim a substantial reduction in maintenance and down time.

Extra heavy-duty shredders are now becoming more popular in Mauritius.

At Savanna factory in Reunion, Messrs. Fives Lille have an experimental turbine-driven gear train coupled to one mill. This is virtually a king-size torque arm gear box with the output gear shaft rigidly coupled to the square of the top roller. The reduction gears are carried in a housing which floats up and down with the top roller and which applies the torque reaction to a robust link which is attached to the housing and anchored to the ground. The tur­

bine is mounted on a fixed foundation and is coupled to the conveyor belt to the de-watering mills. Stella coupled drive shaft. This gearing was completing its second season and had caused no trouble at all.

Diffusion

A D.D.S. diffusion system is operating at Stella in Reunion using crusher bagasse followed by three de-watering mills. This is a fairly old diffuser with a bucket-wheel for transferring the diffuser bagasse to the conveyor belt to the de-watering mills. Stella has experienced trouble with the system and had

to remove the shredder before any reasonable re­sults were obtained. No settling or liming of press water is practised.

All the factories visited in Reunion used bacterial disinfectants on the milling trains.

Clarification

All the factories visited in Mauritius employed hot liming, some before and some after the flash tank. Most of them were using a saccharate principle which they claimed gave a higher filterability sugar than by injecting milk of lime. Syrup from the fourth vessel of the evaporator is used to prepare the saccharate.

No factories in Mauritius use enzymes for starch degradation as they claim that the natural enzymes process is adequate and that there is no detectable sucrose destruction. In Reunion there is no starch problem.

Of the eight factories visited in Mauritius, two were employing the Rapifloc filtering system and were sending the filtrate through to the evaporators. Some of the factories were using a clarification flocculant aid continuously and some intermittently. All the factories passed the clarified juice through stationary wire mesh screens before it was pumped to the clarifier. They claim that the screens gather a significant amount of foreign matter immediately after a week-end shut down.

In order to change clarification techniques and in particular to reduce residence time in the clarifier, Mr. Emile Hugo of Reunion has installed a system which could deal with clarification and filtration of mixed juice in 20 minutes. Briefly it consists of a large tank for progressively liming heated juice with a residence time of 10 minutes followed by 10 minutes' treatment in a pressure filter which pro­duces clear juice and filter cake. It appears that there has been some difficulty in achieving successful operation of this plant.

Pan Boiling and Crystallisation

The use of a two-boiling system is common prac­tice in Mauritius. The A massecuites are cooled for a period of about four hours in rapid water-cooled crystallisers and a drop in purity of between 25 and 27 degrees is expected between A massecuite and A mollasses. A molasses is then boiled into C mas­secuite which is water cooled and then mainly single cured on continuous centrifugals. Electric resistance reheating is now gaining favour in Mauritius and Reunion.

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52 Proceedings of The South African Sugar Technologists' Association — June 1970

All the factories visited in Reunion were using the three massecuite system except for one which was boiling four massecuites. In all cases the B or penultimate molasses was being centrifuged to re­move scum and solids which were then mixed with the final molasses. The amount of reject material was very small. In Reunion, both A and B mas­secuites are cooled in the crystallisers.

Power Generation and Air Pollution In Mauritius all the factories visited supply power

to the Central Electricity Board and therefore they are in a position to somewhat control the amount of surplus bagasse and also to turn the surplus bagasse to a financial advantage. At La Mare in Reunion, the surplus bagasse is being very successfully converted into "Bagaplan" bagasse particle board for which there is a ready market in the French territories.

At one factory in Mauritius the exhaust steam of the back pressure turbo-alternator feeding the grid system has been connected to the vapour one system of the factory to give a larger pressure drop across the turbine so that more power can be expected for the same quantity of steam.

Very little is done regarding air pollution and in all cases where some action is being taken the problem has been tackled by using expansion chambers equipped with water sprays through which the flue gasses pass. The smutty water is either used as surface irrigation or is passed over vibrating screens to separate the smuts from the water. It was interesting to note the difference in smoke emission at one factory which had two boilers of equal capacity but of different design and each with its own stack. The stack connected to the boiler using "spreader" firing was positively worse than the other boiler which employed a stepped-grate type of furnace.

Research in Mauritius

The Mauritius Sugar Industry Research Institute is a very active organisation which is investigating many of the industry's problems on an industrial basis and also those particular to an individual fac­tory. They have evolved a satisfactory regression formula for the exhaustion of final molasses. How­ever, as this was developed from data obtained from existing plant and it is expected that techniques and equipment will improve, three degrees of purity are deducted from the derived result so that the difference between achieved and expected purities will not be negative.

Extensive work has been done on particle size and distribution of crystals in massecuites. This has led to an investigation of particle size and distribution of slurries used for pan seeding. The M.S.I.R.I. is of the opinion that false grain is being developed by using insufficient slurry in the pan and because of this there is a shortage of nuclei on which sucrose can be deposited. The thought is put forward that it is infinitely better to have too much than too little slurry for pan seeding.

Discussion Mr. Buchanan (in the chair): A wage comparison

between Mauritian and South African workers in the sugar industry would be most interesting.

I think the relationship between clean cane, low fibre and surplus bagasse is interesting. Has the effec­tive fuel value of trash something to do with this?

Mr. Moor: As Mr. Gunn is unfortunately away ill, I will try to answer the questions on his behalf. (a) Mr. Gunn has commented that although wages

in Reunion are much higher than in Mauritius, the cost of living was correspondingly higher, resulting in a comparable standard of living.

(b) In Mauritius bagasse moistures down to forty-five are achieved, compared to our fifty % or more. Yet Mr. Gunn observed that even when this very dry bagasse falls ten feet after leaving the final mill, little or no dust is generated, whereas the relatively damp South African bagasse dusts badly in similar circumstances. It appears possible that lack of trash is responsible for this absence of dust.

Mr. Buchanan: Yes, but is the calorific value of trash different from that of fibre, and is this why there is a surplus of bagasse in Mauritius despite the low fibre content of the cane?

Mr. Magasiner: I think the main reason for the bagasse surplus is the moisture content of the fuel.

Mr. Lenfema: Cane is trashed while it is growing in Mauritius due to the heavy rainfall and the strong winds.

It is also cut much younger than in South Africa. Mr. Renton: I am interested in the torque arm gear

box attached to the top roller at Savannah mill. Is it a single or a multiple drive unit?

Mr. Moor: I believe it is a triple reduction gear train with the output shaft rigidly connected to the square of the top roller with a flexible input shaft from the turbine.

Dr. Matic: Regarding clarification, how much sac-charate is used for liming and is there colour forma­tion during the preparation of saccharate?

Also, in connection with use of natural enzymes, how is the juice obtained and what are the pH's like?

Dr. Graham: I presume the application of natural enzymes would be under similar conditions to those used previously in South Africa.

Mr. Pershouse: In Australia syrup is mixed with the lime to a deep chocolate colour. Although there is a problem of high pH, the retention times are short in Australia.

Some factories put the saccharate into the eye of the final juice pump before the juice goes through the heater.

Mr. Carter: I believe in Australia they make a 24° Brix syrup solution, using 8° Be lime.

Dr. Marie: Our experience has been that there is not much difference in sugar quality whether hot or cold liming is used.

Mr. Young: Mr. Gunn mentions an expected purity of final molasses with a formula derived from a re­gression analysis.

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Proceedings of The South African Sugar Technologists'lAssociation —

It is implied that the expected purity is used for practical purposes instead of the normal molasses formula.

I am interested to know what parameters were used in determining the regression formula.

Mr. Lamusse: They were Brix converted to dry matter, reducing sugar and ash.

Thirty percent of the factories were getting better than the expected purities.

Mr. Williams: I noticed the absence generally of shredders in Mauritius, but the preparation was excel­lent through the use of knives. A 72" mill might have as many as 100 knives, and would often give as good a preparation as a shredder.

Mr. Buchanan: 1 also noted this in Mauritius, but we hold generally that a shredder is necessary for good milling performance.

Mr. Hulett: In Mauritius, is it customary to have the knives running backwards or forwards?

Mr. Williams: I did not observe the direction of rotation, but I did notice that the speed employed for

— June 1970 53

the secondary set was 600 rpm compared to 500 rpm for our factories.

Dr. Matic: I understand that the preparation by knives is good enough to be considered suitable pre­paration for a diffuser. Some of the knives were shaped differently to ours.

Dr. •Graham: A two boiling system is used in Mauritius, starting with a massecuite purity of 88, but A-massecuites are water cooled.

This should contribute to reduced losses from de­composition in the boiling house, as well as making possible the phenomenal purity drops in the A massecuites of up to 27°.

The boiling house recovery shows figures ranging up to 93, and they have high overall recoveries because of high mill extractions.

Mr. Buchanan: This paper indicates the value to our industry of trips overseas undertaken by ex­perienced technologists.

Our S.M.R.I. should be interested in the work being done by the Mauritius Research Institute on particle size and distribution of slurries used for pan seeding.

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54 Proceedings of The South African Sugar Technologists' Association —June 1970

NOTES ON AIR POLLUTION IN THE SUGAR INDUSTRY By B. ST. C. MOOR

The Tongaat Sugar Company Limited

Summary A topic currently commanding urgent attention

with the proposed scheduling of the sugar industry in terms of the Atmospheric Pollution Prevention Act is discussed in general terms. A variety of causes and remedies are commented upon and fields for further research suggested in the hope of stimulat­ing fruitful discussion.

Introduction On the morning of 10th December, 1969, a number

of persons interested in the reduction of air pollution caused by boilers in the sugar industry chanced to arrive at the Engineers' Offices, Tongaat, simul­taneously and the opportunity was taken to convene an informal forum for discussion of this vexed topic. This paper is a direct result of those discussions and much of what follows forms a synthesis of ideas expressed by those present, who were:—

Mr. N. Allan of the S.M.R.I. Dr. E. C. Halliday of the C.S.I.R. Mr. N. Boegman of the C.S.I.R. Mr. N. Magasiner of John Thompson Africa

(Pty.) Limited. Mr. J. Michley of John Thompson Africa (Pty.)

Limited. Mr. J. van Dokkum of the Tongaat Sugar

Company. Mr. B. St. C. Moor of the Tongaat Sugar

Company. Dr. Halliday is the Chief Air Pollution Control

Officer with the C.S.I.R. and he and Mr. Boegman have been charged with the task of investigating and combating this problem in the sugar industry. Their visit to Tongaat on this occasion was for purposes of preliminary fact-finding and problem assessment.

Mr. Magasiner and Mr. Michley had been in­volved in association with Tongaat Sugar Company with investigations into means of preventing smuts from bagasse-fired boilers and had been conducting experimental work on a pilot plant at Tongaat.

Perspective Air pollution in general is undesirable when one

or both of two circumstances prevail. These are, first, when it forms a health hazard (e.g. poisonous gases); and, secondly, when it forms a social amenity hazard (e.g. unsightly, light obstruction or dirt fall­out).

In the sugar industry the problem is almost en­tirely of the second type, and is primarily associated with the fall-out of incompletely combusted particles ("smuts") rather than with the true "smoke". The remedy lies either in prevention, by avoiding the generation of smuts (Generation) or in cure, by removing generated smuts from gases before their release (Removal).

Generation 1. Bagasse as a fuel presents problems. With the

miller pushing mills to high capacities, high moisture contents can be expected (South African moistures tend to be higher than most). Further, bagasse is generally a non-homogeneous fuel, with heavy and light fractions, large and small particles inter­mixed. These properties are not conducive to com­plete and even combustion, but to overcome these limitations of bagasse as a fuel is probably too costly and too complex to be a feasible solution to the problem.

2. In similar vein, the presence in South African bagasse of a relatively high volume of trash residue, which is light and flakey, could be aggravating. A change in the basis of cane payment may help here.

3. In any bagasse-fired boiler or incinerator, adequate furnace area is essential in order to ensure a low gas velocity and thus minimise carry­over. Unfortunately it is seldom easy to redesign existing furnaces.

4. Adequate height of the furnace is also impor­tant, in order to allow a sufficient period of time before contact with the tubes and extinction of the flame front. Any incompletely burnt particles at this stage will carry over as smuts.

5. Another contributory factor to smuts genera­tion can be the lack of draught control on a boiler. Fitting of such control may often be simple and inexpensive.

6. Spreader stokers are far greater offenders than the hearth-type furnace as the principle of combus­tion in suspension is bound to induce carry­over. However, it is accepted that spreader stokers are essential for dual fuel (coal/bagasse) boiler firing.

7. Boiler selection based exclusively on cost must cause boiler designers to rate their designs immoder­ately. It is recommended that sugar engineers include the requirement that the plant be "smut-free" in tender specifications for new boilers. Stan­dards of freedom from smuts for bagasse-fired boilers have not yet been defined, but it is hoped that Dr. Halliday and his colleagues at the C.S.I.R. will be able to assist in this regard.

8. Boiler users are also to blame for accepting situations of under-capacity, in which boilers are forced beyond their design loads. Perhaps this is the greatest single cause of the smut nuisance in the industry.

9. Another major cause of smuts carry-over from certain boilers is the lack of air heaters. The rela­tively moist bagasse found in the S.A. sugar industry will not burn to complete combustion in most boilers unless combustion is initiated with pre­heated air.

10. Correct training and supervision of boiler operators in such matters as fuel bed levels,

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Proceedings of The South African Sugar Technologists'' Association —

steady fuel supplies, fuel distribution across the furnace and draught control is also essential.

11. It has been suggested that the common prac­tice of mixed firing of bagasse and coal causes more smuts than either fuel used on its own, and should be avoided. To avoid this practice may require larger bagasse storage facilities with improved recovery plant.

It is worth noting that many of the remedies pro­posed in this section are inexpensive, and often have side benefits which would enable the measures to pay for themselves.

Removal If measures to prevent the generation of smuts

are either not feasible or unsuccessful, then the less satisfactory solution can only lie in their capture and removal from the flue gases. Comments to be made on some methods tried are:—

1. Spinners and cyclones are of dubious effective­ness in dealing with the relatively large particles of low density which constitute the bulk of bagasse smuts.

2. The cost of electrostatic precipitators, which would probably be effective, is prohibitive (one price quoted was nearly three times that for an equivalent cyclone system).

3. Partial success has been achieved at Tongaat using water sprays in a "smuts chamber". Essentials are adequate volume and dispersion of sprays, low gas velocities through the chamber (Dr. R. Morris has quoted a maximum of 3 m/s) and a brick-, con­crete- or stainless steel-lined stack to resist internal corrosion. In order to provide sufficient water a recycling system with small make-up and leak-off was instituted. Smuts screened from the spray water is disposed of with the factory filter cake. Problem areas in the system are choking of the sprays, pump maintenance and screening the smut-bearing water. These have now been largely overcome.

4. A system of removal being tried in Australia involves bubbling the flue gases through about 25 mm of water. In addition to the disposal and stack corrosion difficulties, this method also imposes an additional head on the induced draught fan and would normally require an increase in power here of about 15%.

5. Engineers of John Thompson Africa have recently carried out extremely promising experi­ments at Tongaat involving filtering the flue gases through various screening media. On the pilot plant most success was achieved using a 40-40 per inch mesh stainless steel vibrator screen as filter medium. This system virtually guarantees the dry removal of 99% by volume of all particles over 0.25 mm in size, and a large proportion of all finer smut particles. The disadvantages of the system would appear to be cost (R20,000 to R30,000 for a fully automatic unit for a 40t/h boiler) and increased I.D. fan power requirements owing to the pressure drop of approximately 25 mm w.g. across the filters.

6. In a very few instances, an acceptable alterna­tive to removing the smuts could be to spread it a bit more thinly over the downwind terrain. One way to do this is to increase stack heights.

— June 1970 55

Conclusion Dr. Halliday has persuaded the South African

Sugar Millers' Association to agree to the industry's being declared a "Scheduled Industry" in terms of the Atmospheric Pollution Prevention Act. All mills will thus be required to take stock of their position in the very near future. To assist in this, Dr. Halliday proposed the formation of a study group comprising mill engineers together with S.M.R.I. and C.S.I.R. representatives. This group has been formed and with the assistance of Dr. Halliday and his staff should be able to play a constructive part in "cleaning up" the skies over the industry.

The foregoing discussion demonstrates that solu­tions need not be very costly and could well be self-financing. Study avenues in this field could include quantitative studies of satisfactory furnace design principles; methods of measuring stack emis­sions; criteria for satisfactory stack conditions; the development and evaluation of smuts removal sys­tems; and alternative uses for bagasse to obviate the need for incineration.

Discussion Mr. Magasiner (commenting on his slide projec­

tions): I agree that the most intelligent way to solve the problem is to eliminate the cause. Correct fur­nace design goes a long way to achieving this. At our company's second International Conference on Boiler Plant for the Cane Sugar Industry in Australia last year the factors affecting carry over were discussed at length and parameters were quantified using an acceptable visual stack emission as the guiding criterion.

Apart from furnace configuration, bagasse moisture content and grading were high-lighted as the most important single factors affecting performance. The lower the moisture content, the lower the smut emis­sion from a given unit. The University of Natal is at present attempting, on our behalf, to formalise the empirical data which we have gathered together.

By the way, there was strong evidence presented at our conference to indicate that a correctly designed hearth type furnace set in a Dutch Oven was the most effective available from a grit and smut suppression and combustion point of view. Initial cost, size limi­tations and maintenance unfortunately ruled it out as a commercial proposition under present-day con­ditions.

While mechanical collectors of the cyclone or multi cyclone type are capable of collecting a substantial proportion of the denser grits, they are unable to collect the smut particles which have a very much lower density.

The performance of a collector drops as the density of the particles to be collected is reduced. If the aerodynamic drag on the particles is high, as is the case with bagasse smut, the reduction in performance is very much greater and the collector efficiencies are reduced even more radically. To aggravate the prob­lem still further, any air leakage into the collector through the dust discharge system causes a substantial reduction in performance.

The problem has been analysed in detail by. the Sugar Research Institute in Mackay, Australia, who

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56 Proceedings of The South African Sugar Technologists' Association —June 1970

have concluded that wet collectors of the scrubber type are the only suitable machines available at present.

The wet type collector, however, suffers from a number of very serious disadvantages. These are:— (a) The gases leaving the collector are saturated. The

ductwork, induced draught fan and chimney must therefore be protected against corrosion. The ducting and chimney can be Gunnite lined but this is expensive and would probably have to be renewed every four odd years. The induced draught fan would have to be made of stainless steel.

(b) The water absorbed by the gases would amount to approximately 10%—15% of the M.C.R. evaporation of the boiler plant.

(c) In order to avoid creating a water pollution prob­lem, the water used in the collector would have to be filtered and re-circulated. A simple vibrat­ing screen appears to be quite adequate for this duty. The solids contents of the re-circulated water apparently stabilises at about 0.3% by weight.

Because the wet collector in solving the smut emis­sion problem creates a number of expensive subsidiary problems, it seems worthwhile to spend a bit more time in trying to make the dry collector work before admitting defeat.

Towards the end of last year, we tested, in con­junction with Tongaat, a filter device. Unfortunately, for reasons beyond our control, our experiments were curtailed before we were able to finally establish ultimate performance limits.

The preliminary results appeared to be reasonably promising and indicate that further work is warranted. Provision has been made in the ductwork of the new boiler being installed at Tongaat to carry out these tests.

Having collected the grit and smuts the problem of disposing of them remains. They must be damped down to eliminate a fire hazard and to prevent them blowing about in the wind. The mechanical design of equipment to successfully handle these wastes is an interesting problem in its own right and one which I feel should be divorced from the broader problem of collection.

Mr. Buchanan (in the chair): For avoidance of air pollution, should trash be burnt in the field or in the factory furnace?

Mr. Moor: Burning in the fields does not overcome the problem of pollution, it merely spreads it over a wider area, although the fields may at least derive some benefit from the burnt carbon particles.

Mr. Kramer: How high does Mr. Moor think the bagasse furnace should be in relation to the furnace grate area?

Mr. Moor: There are no criteria that I am aware of giving ratio of furnace area to height or furnace volume to calorific output of the boiler at M.C.R.

I think that air pollution study group should in­vestigate this.

Mr. Allan: Before we do anything, we must estab­lish scientifically a satisfactory level of emission.

We can improve existing stack conditions by taking note of all the points Mr. Moor has raised.

An elementary way to begin is to pay more atten­tion to the boiler house.

Some sugar factories have already installed dust collecting equipment.

Fortunately we have a reasonable amount of time to set our houses in order.

I take issue with Mr. Moor on one point. I am not convinced that, if a spreader stoker boiler is fired correctly and its fuel to air ratio is correct, that it is a worse type of unit than any other.

Mr. Moor: I would agree with Mr. Allen if he also mentioned design of the spreader stoker furnace.

If two identical furnaces are fired, one with a spreader stoker and the other with a quiescent bed, then the spreader stoker will emit more from the stack than the other, because in the quiescent bed there is a period for bagasse to be heated before going to the gas passes. Therefore, it requires less time to com­plete its combustion and is likely to undergo more thorough combustion. Often with spreader stokers, furnace areas and furnace heights have been kept to the barest minimum with an eye to cost and no account has been taken of pollution.

Mr. McLunan: With coal, are not toxic effects more important than visible emission, and does this not apply to bagasse as well?

Mr. Moor: Apart from the central refinery in Dur­ban, most sugar factories only use coal intermittently as an auxiliary fuel. The factories are generally situated out of town and I have not heard of any complaints about toxicity of flue gases. The toxic effects of coal gases are mainly associated with con­centrations of sulphur dioxide. Bagasse, unlike coal, contains only negligible quantities of sulphur.

Mr. vau Hengel: To limit increased use of coal in the sugar industry as bagasse utilisation projects de­velop, we should investigate bagasse saving methods and endeavour to make changes in process operations rather than boiler operations.

Mr. Dick: Have any attempts been made to pul­verise bagasse to make it more uniform before firing?

Mr. Magasiner: An enormous amount of horse power would be required for this purpose.

Mr. Strong: Pollution is a matter of economics. When a new boiler is required the first consideration is price. It is difficult to convince management to spend more in order to prevent pollution.

Mr. Allan: One of the objects of the study group is to set up reasonable criteria which we know will give us an acceptable smut emission.

Boiler manufacturers in future will only be able to sell boilers to the sugar industry that comply with our reasonable standards.

Dr. Mansfield: Surely the important point is the concentration of material coming down — and what goes up must come down!

Mr. Allan: That sounds correct but it is possible to do as Rand Carbide did, namely, build an enor­mously high stack so that emissions simply disappear into the atmosphere. The cost of the stack was, how­ever, very high.

Page 72

Proceedings of The South African Sugar Technologists' Association — June 1970 57

WATER CONSERVATION IN SUGAR MILLS By D. J. L. HULETT

Deon Hulett and Partners

The year 1970 has been declared water year. What is "water year"? It is an attempt by the Govern­ment to make both industry and the public more conscious of the part they must play in the con­servation of water.

The country's economic growth and prosperity depends on an adequate supply of water—but this supply is dwindling at an alarming rate.

At present, the Government is attempting to con­serve our natural water resources by building dams and by passing legislation through parliament mak­ing it a criminal offence to misuse water.

This means that in the very near future industry will be forced to take measures to halt unnecessary waste and pollution.

Contrary to Press reports—I refer in particular to an article in the Natal Mercury dated 13th March which was headlined "Rubbish . . . by Industry". We all know that industry does cause pollution and we in the sugar industry should make every effort to eliminate this problem and prevent unnecessary waste.

With this in mind I would now like to discuss:

Sugar Mill Effluent Elimination If one considers the overall water balance of a

sugar mill (see Fig. 1) one can see that the amount of water coming in with the cane is almost enough to maintain the operation of the factory and it is this criterion which led engineers to have the courage to build mills such as Empangeni and Jaagbaan, remote from rivers, which have to rely only on water obtained from boreholes for the operation of the mills.

Mills where an abundant supply of water has existed have not, however, bothered to conserve water and so the usage has become greater as the mill gradually expanded. What is happening now to these mills is the materialisation of a twofold problem. One is that the supply of water is running low due to the demand on the river and the other is that restrictions are being placed on the disposal of effluent.

What can be done about this situation? There are two solutions— (a) to build dams and store large quantities of

water and install effluent treatment plants and effluent disposal schemes to cope with the water; and/or

(b) to close up the system and make maximum use of the water by careful selection and recirculation.

It is this latter choice that I wish to discuss in this paper.

Imbibition Water

Consider the water balance sketch (Fig. 1) of a typical sugar mill. The first large water requirement is the imbibition water required for washing the sugar out of the crushed cane.

Most mills require that this water be applied cold for various reasons. The two main reasons are to prevent roller slip when large quantities of imbibi­tion water are used on mills operating at high fibre throughputs and to obviate the mill house becoming wet and clouded with steam on cold evenings.

The hot condensate collected from the evaporator tail ends, pans and heaters is generally sufficient to supply this water and it is simply a matter of cooling this water to a suitable temperature for application to the mills. This is best achieved by first flashing the condensate down the evaporator to 71° C cor­responding to the 335 mbar vacuum prevailing in the calandria of the last effect and then cooling with cold mixed juice down to about 32° C in a counter current liquid-liquid heat exchanger. Should really cool imbibition water be required it may be neces­sary to by-pass the hot return juice from the Oliver filters around this liquid-liquid heater in factories where this filtrate is returned to the mixed juice tank.

Boiler Feed Water

From a steam economy point of view and from the safety angle with regard to sugar contamination, all the low pressure steam should be fed to a pre-evaporator in which the clear juice is boiled to pro­duce vapour at about 1.4 bar for the supply of pans and heaters and other general use. In this way it is possible to collect most of the steam generated in the boilers as condensate and return it to the boilers as feed. This condensate is withdrawn from the pre-evaporator calandria at about 2.03 bar and is flashed to below atmospheric pressure, the flash heat being utilised for juice heating or boiling the tail vessels of the evarporator.

A certain amount of make up, however, is in­evitable due to the loss of the flash and the inevit­able leaks. This make up for the boilers should be obtained from the second effect of the evaporator calandria condensate. Multiple layer wiremesh en-trainment preventers can achieve a very high efficiency in the scrubbing of sugar entrainment from the vapour produced in the pre-evaporator provided, of course, that it has been correctly designed and properly maintained.

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58 Proceedings of The South African Sugar Technologists'' Association — June 1970

Boiler Feed Water Storage At this point it seems pertinent to mention that

accidents do happen even in the best organised and controlled systems and in order to obviate the use of untreated water for boiler feed, it is therefore very wise to have at least four hours' storage of con­densate or treated water. Preferably most of this water can be stored out of circuit, i.e. allowed to get cold but must be readily available to the main boiler feed water pumps either by gravity or a reliable independent pumping system.

Bearing Cooling Water Considerable quantities of water are used for

cooling purposes other than in the pan and evaporator barometric condenser system. This water should be arranged to circulate in a closed system, including a cooling tower and a sand filter. This water requires to be looked after and cared for in the same way as that of a swimming pool. Neglect of this system can cause corrosion of the various internals or the build up of algae with conse­quent blockage of the various small cooling passages. Water loss from this system is usually very small as the amount of heat dissipated is not very great.

The Main Condenser Circulating System This water is circulated in large quantities but,

provided there is no leak in the system, this water level should gradually increase until a slight over­flow occurs.

This excess occurs from the fact that water is con­densing from the pans and evaporator tails into the system and evaporating again in the cooling tower. However, for each kg of steam condensed, less than

1 kg of water need be evaporated in the cooling tower as some of the cooling (possible 20% in this climate) is achieved by conduction to the air drawn through the tower and not by the transfer of latent heat through evaporation.

Storage of Water for Week-end Washdown The overflow from the condenser cooling system

should be stored in a reservoir of suitable dimensions to allow sufficient water to be stored for the week­end washdown requirements. A sufficiently large pumping station must be connected to this reservoir so that pans and evaporator vessels, which require quick filling for cooling down for maintenance pur­poses, can be filled in a relatively short time. The dam for a 300 metric tons per hour mill could con­tain, say, 1 500 nr' and a 150 mm system capable of delivering 38 1/s would be sufficient. Water used for washing out the pans and evaporators must be re­turned to this dam. An aeration paddle operating on the surface of the water will easily allow the collected sugar to be digested and the water to be purified sufficiently by the following week-end for re-use.

Dunder Water (The Mill Water Effluent) Dunder water is the term given to the general

effluent from a sugar mill and it is made up generally of floor washing, water leaking from bearings or running off hot bearings on the mill, the overflow from the cooling pond, odd condensate leaks or that which is being deliberately dumped, wash water from the pans and evaporators and innumer­able other sources, even possibly from the drain of a hand-basin at the centrifugal station.

The elimination of this dunder water is obviously

EVAPORATOR WATER BALANCE ON 100 CANE

Ex Steam 50

Clear Juice 114xCane

includes 14 Bx. H 2 OinM.J . 100 »

< r

I Condensate to boiler 52Vi

1

1 >

Syrup 20

'

^ Condenser 10

Sweet Water Condensate including pan and heaters 67'/i

Mills 50 * * 1 7 i i Oliver filters and hot water services

Page 74

Proceedings of The South African Sugar Technologists' Association — June 1970 59

possible but, of course, it requires careful planning and attention to detail in order to achieve this.

The week-end washout water has been dealt with in a previous paragraph. Mill bearing water leaks can be routed into the juice or imbibition systems provided that the bagasse is weighed for mill balance calculations. The floor washing can be minimised or possibly even eliminated if the floors are suitably laid and paved so that they can be cleaned with a brush or a mop. Of course, attention will have to be paid to the elimination of molasses leaks from crystallizers and pump glands and the sugar dust problem, but monies spent toward this end do bring a return in the saving of undetermined losses and at the same time greatly improve the appearance of the plant. It is after all a food factory and should, as such, be kept spotlessly clean.

Domestic Supply and Sewage Effluent No sugar factory can operate without personnel

and with personnel comes the problem of domestic water supply and sewage disposal. The factory waters discussed so far are not suitable for domestic purposes and apart from that are not sufficient in quantity. This water supply has to be obtained from a stream, river, boreholes, or piped from a suitable dam site or regional supply and the sewage effluent resulting therefrom will need to be treated in a suit­able sewage works.

I have attempted to indicate to you how one should be able to operate a sugar mill with as little water as possible. The systems I have described I know are feasible. It is the responsibility of all of us who are involved in the operating of the sugar mills to see that we play our part in the crusade to save our water supplies.

Discussion Dr. Mansfield: There is a problem of lack of water

in a factory at the end of the season when the cane supply ceases but the boil-off continues for some days.

This should be kept in mind when contemplating siting a factory away from a river. It is for the same reason necessary to have a storage dam.

Mr. Kramer: Mr. Hulett mentions returning con­densate to the cooling tower. Did it go back into the top of the tower?

Dr. Mansfield: Yes, because the amount of heat to be removed from the condensate was comparatively negligible.

Mr. Phipson: It was mentioned that when condenser water was used for imbibition it caused trouble in the factory.

Mr. Hulett: The condensate from the latter vessels of the evaporators and the pans is clean and at Darnall it is put through a heat exchanger to cool it before applying it to the mill. It does no harm at all.

Initially, however, the hot water was directed straight into the cooling pond and water drawn from there for imbibition caused trouble.

Mr. Phipson: Is it therefore acceptable to use, for imbition, water from condenser outlets?

Mr. Hulett: Yes, provided that the system is of small volume and is clean as at Jaagbaan. Dirty cooling pond water will cause trouble in the factory.

Mr. Rennie: I think that any dam for storage of water for weekend wash down would have to be very carefully designed to avoid creating smells, even though aeration would assist purification.

Mr. Hulett: Ponds can be designed with proper aeration facilities to accelerate the period of stabili­sation.

SUGAR MILL WATER BALANCE ON 100CANE

Filter Cake 5 x 70% water

i ,

Flash 6°F

100 Cane

70% Water 15%Brix 15% Fibre

3.5 1.1

70

2.5

+4 Net Gain

40

.1

18.2

-+• Molasses 3 x 20%

-* Sugar Drier 12x1%

->Bagasse35x52%

Cooling Pond Evaporation 80% of Steam 50

Boiler Blowdown 5%x 50

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60 Proceedings of The South African Sugar Technologists' Association —June 1970

STAINLESS STEEL IN THE SOUTH AFRICAN SUGAR INDUSTRY

By C. G. W. ROFFEY* and I. A. ELSDON-DEW**

Until five years ago South African sugar engineers and technologists were reluctant to consider stainless steel for these reasons:

(i) cost,

(ii) different fabrication techniques compared to traditional mild steel,

(iii) lack of knowledge about stainless steel.

This paper attempts to clarify the above points, highlight some of the progress made to date and outline future applications.

TABLE 1

A.I.S.I. Metallurgical Series Structure

y Ferritic

4 0 0 ^

^ Martensitic

300 Austenitic

Major Alloying Elements

Fe. Cr.

Fe. Cr. C.

Fe. Cr. Ni.

Basic Properties

Magnetic Non

Hardenable

Magnetic Hardenable

Non Magnetic Hardenable

The metallurgical types of Stainless Steel and their basic properties

(a) Stainless steel as a material "Stainless Steel" is not a single metal—it is the name

given to a group of iron based alloys containing a minimum of 11 % chromium. Although the basic stainless steels are divided into three metallurgical categories, it will be noted from Table 1, that the A.I.S.I. numbering system only differentiates between the nickel containing Stainless Steel (300 series) and the non-nickel containing Stainless Steel (400 series) The A.I.S.I. specifications cover a large range of stainless steels many of which are tailor made to oper­ate at temperatures of —273° C to -+• 1 000° C, to combat a wide range of acids, alkalis, gases etc., and with mechanical properties ranging from the hardness of razor blade steel to the ductility of deep drawing steel.

Fortunately the sugar technologist has only 3 stain­less steels to consider, and Table 2 gives the respective A.I.S.I. specifications.

TABLE 2

A.I.S.I. No.

304

316

430

Chromium %

18

18

17

Nickel %

8

10

—

Molybdenum %

—

3

—

* Metallurgical and corrosion consultant. ** R. Jackson and Co. (Natal) (Pty.) Ltd.

The basic composition of A.I.S.I. 430, 304, 316.

(i) A.I.S.I.—304. This is the basic stainless steel in the 300

series, containing 18% chromium and 8% nickel. It is one of the most versatile stainless steels having excellent corrosion resistence, extremely good ductility, and excellent weld-ability. Most sugar engineers will be familiar with this grade due to its extensive use as tub­ing for juice extraction.

(ii) A.I.S.I.—316. This is another nickel containing stainless

steel similar in mechanical properties to A.I.S.I. 304. The addition of 2—3% molybdenum greatly increases the pitting resistance and so this stainless steel is only used in applications calling for ultra high corrosion resistance, e.g. highly by acidic or alkaline environments.

(iii) STELEX 430. This is a straight 17% chrome stainless steel

made by Southern Cross Steel Co. (Pty) Ltd. at Middleburg to the basic A.I.S.I. 430 specifica­tion.

Stelex 430 does not have quite the same level 6f corrosion resistance as A.I.S.I. 304, but being a nickel free stainless steel, it is significantly cheaper whilst offering vastly better resistance to corrosion than mild steel.

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-June 1970 61 Proceedings of The South African Sugar Technologists' Association

The U.T.S. values and relative hardness of these stainless steels are compared to mild steel and 70/30 brass in Table 3.

TABLE 3

U.T.S. p.s.i.

MN/ms

h bar

Hardness B.H.N.

Mild Steel

60 000 413.685 41.369

120

Stelex 430

75 000 517.107 51.711

190

A.I.S.I. 304/316

85 000 586.054 58.605

180

Brass 70/30

45 000 310.264 31.026

120

Note: 10 000psi= 68.948 meganewtons per square metre = 6.895 hectobars

14 500 psi = 10 hectobars

The strength and hardness characteristics of Stainless Steel compared to mild steel and 70/30 brass

(b) Stainless Steel Costs. The kg for kg costs of the stainless steels as com­

pared to mild steel and 70/30 brass are given in Table 4.

TABLE 4

Mild Steel 70/30 Brass

Stelex A.I.S.I. A.I.S.I.

430 304 316

1 10

44 84

13

The basic cost comparison of mild steel 70/30 brass and Stainless Steel.

Although the initial material costs of stainless steel appears prohibitive, practical experience in the sugar industry over the past 2 years has shown that the thickness of stainless steel can be reduced by at least 25 % compared to mild steel with the resultant savings in material, handling, and fabrication. In several in­stances more complex fabrications such as pan con­densers have been made in STELEX 430 at only double the price of mild steel and with far superior corrosion and abrasion characteristics.

Experience to date has shown that a life of 10—12 times is possible with Stelex 430 against convential mild steel, and thus the saving on maintenance and replacement cost is more than offset by the initial capital cost of stainless steel.

(c) Stainless Steel Fabrication. Most mill engineers have now developed welding,

and fabrication techniques for Stelex 430 and A.I.S.I. 304 to suit their own staff and workshop lay out. Excellent weldability for Stelex 430 has been achieved by using the standard austenitic electrodes, such as A.I.S.I. 310. In many cases STELEX 430 has been successfully welded in as a replacement part of a mild steel construction using these same electrodes.

The higher hardness and strength of the stainless steels has posed certain cutting problems in view of the limited shearing capacities in most units. However the introduction of powder and disc cutting now appears to have overcome these difficulties.

Stainless Steel in Crushing/Juice extraction Stelex 430 has made a significant contribution to

machinery life and reduction of maintenance costs in this part of the mill. It has been proved to be ideal for abrasive areas such as intercarrier bottoms and boots, and current results indicate an average wear of 0.25mm—0.38mm per season as compared to an average loss of 3.81 mm—4.46mm for mild steel plates subjected to similar duty. At two mills the last two intercarriers in the tandem show that the Stelex 430 plates installed have even less wear ± 0.05mm (± .002in) during one seasons operation. Thus in com­parison with mild steel, a life factor of over 10—12 times has been obtained from Stelex 430 for an initial installation cost including raw material of 3 times that of mild steel.

Some Mills, to save on initial capital, are now using 6mm Stelex 430 as liners instead of the conventional 10mm or 12mm mild steel.

Continuing on the tandem, Donnelly chutes situated over the rollers have been fabricated from 3mm Stelex 430 and after one season operation, no wear has taken place, (± 0.05mm). Juice gutters, maceration tanks, under pans have all been fabricated from Stelex 430 usually in 5mm thickness, and on testing a maceration tank after 3 full seasons operation, other than the removal of the original mill scale, there was no sign of wear and even more important, no pitting attack. (See Fig. la & 6) In this case it is worth noting that 5mm Stelex 430 was used for the fabrica­tion in place of 10mm mild steel, again saving on material cost.

In diffusers some experimental plates of perforated Stelex 430 have been installed and after one season are standing up far better than the mild steel counter­parts. In addition, Stelex 430 is being used as side plates to combat the corrosion that normally occurs in this area.

Primary juice lines are also an excellent application for Stelex 430 and piping of 100mm x 3mm wall and 150mm X 3mm wall are being installed this year at three sugar mills, also supplied are collars and pressed bends, fabricated from Stelex 430.

Screw conveyors especially the bottoms have shown good results with Stelex 430 although trouble has been experienced with the flights. This is a welding problem and with the correct technique is being overcome. Juice scale tanks have now been manufactured and installed in three mills, and once again Stelex 430 lends itself to this type of application.

At several mills this year Stelex 430 is being used as a repair material for badly corroded or eroded plates, as it can easily be welded to mild steel.

Prior to the introduction of Stelex 430 many vessels e.g. maceration tanks and storage tanks were fabrica­ted from A.I.S.I. 304, which now appears to be a

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62 Proceedings of The South African Sugar Technologists'' Association —June 1970

quality (and price) in excess of the normal require­ments.

It is apparent that STELEX 430 has opened up applications to the use of stainless steel in the mill operation which were previously considered far too expensive with the traditional 300 series stainless steels.

Stainless steel in the processing operation In contrast to the rapid progress with STELEX 430

in the crushing operation A.I.S.I. 304 has been a well established material for centrifuges etc. in the sugar processing operation. However recent upheavals in the price of copper together with more advanced tech­niques for the manufacture of stainless steel tubing has resulted in the significant use of A.I.S.I. 304 for juice heater and evaporater tubes in place of 70/30 brass.

Stainless steel tubing for this application is currently less than half the price of brass tubes. The superior mechanical strength of A.I.S.I. 304 (See Table 3) allows the use of 18g stainless steel tubing compared with 16g or 14g brass.

This thinner wall facilitates easier expansion of the tubes into the tube plate, furthermore stainless steel has a better resistance to scaling, and cleaning opera­tions do not have to be as frequent or as stringent as brass. Whilst South African installations are still giv­ing satisfactory results after 5—6 years operation, some overseas mills have now had stainless steel tubes for over 12 years.

Some overseas mills have used A.I.S.I. 430 tubes for over 8 years, but limited supplies have to date precluded the wide spread use.

The resistance to pitting of STELEX 430 has been employed extensively in pan condensers with excellent results. Vacuum pipes are also being fabricated from 6mm thick STELEX 430 compared to 10mm mild steel, which helps considerably with the erection of these pipes.

FIGURE la: Maceration tank in Stelex 430 showing no signs of corrosive attack.

FIGURE lb: An identical tank in mild steel under same conditions as tank in la. Shows heavy pitting attack.

Conclusion Experience in the South African sugar industry over

the past three years indicates that A.I.S.I. 304 is a well established material for juice evaporator and heater tubes, and should continue to grow at the expense of brass.

The many successful applications of the recently introduced STELEX 430 indicates that there will be a rapidly increasing demand for this stainless steel to combat general corrosion and abrasion particularly in the crushing operation.

Discussion Mr. Moor: Dr. Roffey dealt with corrosive proper­

ties but not with strength and fatigue resistance." Dr. Roffey: The fatigue limit of the 430 series will

be slightly lower than that of the 300 series, but the fatigue limit of the 300 series is considerably higher than that of mild steel.

As regards mechanical properties. With the 300 series, work hardening will take place depending on the amount of cold work. The U.T.S. can go up from 17 tons square inch to 32 tons square inch with about 10% cold work, which is approximately a 90° bend.

Recent developments in the U.K. have produced a stainless steel with 60 tons U.T.S. and 55 tons yield strength, in a fully ductile state.

Generally speaking, all stainless steels are stronger than mild steel and several stainless steels are now available with the strength of very high tensile steels.

Mr. Elliot: What sort of treatment should be given in a mill to tubing with regard to passivation or annealing?

Dr. Roffey: In terms of softening the austenitic stainless steels are the opposite of mild steel.

To soften stainless steel you must heat it higher than 1 050° C and then quench. The only way you can harden it is by working it.

If you heat it with a gas torch you will get carbide precipitation and the stainless steel may become sensi­tised and will corrode badly at the sensitised areas.

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Proceedings of The South African Sugar Technologists' Association — June 1970 63

Passivation and removal of oxide films is carried out using a ten percent nitric acid solution with one percent hydrofluoric acid and, if desired, a small amount of potassium dichromate.

Mr. Stender: Chromium stainless steel is sensitive to chrome carbide precipitation in the welding pro­cess. Can you make any recommendations?

Dr. Roffey: A low carbon stainless steel or titanium or niobium stabilised stainless steels should be used.

A welding rod with high nickel and high chromium content should also be used with the same low carbon analysis or titanium additions as the parent metal.

Mr. Williams: Will this also apply to building up stainless steel shafting?

I once built up a pump shaft by metallising and after a short time it left the parent metal.

Dr. Roffey: This was probably because the wrong rod was used. It is usually safe, with the 300 and 400 series, to use the type 310 rod.

Mr. Renton: The 410 series has been recommended for mills for abrasion resistance but this has not been mentioned in the paper.

Also, there has been more use of stainless steel in

centrifugal baskets in the sugar industry but there have been some unfortunate results because of stress corrosion.

Dr. Roffey: I omitted 410 because it is difficult to fabricate. It has 12% chromium and very high carbon so that it is hard and brittle.

It is difficult to combat stress corrosion cracking in stainless steel. The trouble in centrifugals has been due to a combination of stress and corrosion. Their combination gives a force many times stronger than either of them individually and therefore failure, when it comes, is rapid. The main corrosion is due to chlorides and in all cases the stress has to be tensile. Therefore, the ways to eliminate stress corrosion cracking are either to apply a compressive stress, to eliminate chlorides, or to use a material that is not susceptible, such as Incanel, which can be expensive.

Mr. Fokkens: We like to insert stainless steel liners into tanks. Is a 310 electrode the one to use to weld stainless steel to mild steel?

Dr. Roffey: Yes, the 310 is the correct electrode to use.

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64 Proceedings of The South African Sugar Technologists Association —June 1970

THE INTERDEPENDENCE OF CANE PREPARATION, PARTICLE SIZE, DISPLACEABILITY, AND LIQUID

HOLDUP IN FIXED BED DIFFUSERS By P. W. REIN

Huletfs Research and Development, Mount Edgecombe

Abstract Observations on the use of Displaceability Index

and sieve analysis as a means of characterizing cane preparation are given. Data on liquid holdup in fixed beds of bagasse are presented; both dynamic and static holdup are shown to be dependent on flow rate and the degree of cane preparation.

Introduction It is now a well-established fact that the degree

of cane preparation has a considerable effect on diffuser extraction. Moreover, cane preparation affects the maximum obtainable percolation rate, and juice holdup and retention time. There is, therefore, a need for some quantitative means of characterizing cane preparation. This is no easy task, due to the nature of bagasse particles, which constitute a wide range of complex shapes and sizes.

Markham4 recently investigated Displaceability Index as a measure of cane preparation, and demon­strated a relationship between bagasse particle size as obtained by sieve analysis and Displaceability Index. Further observations on these two methods of particle characterization are presented, as well as liquid holdup data in a fixed bed diffuser.

The subject of this paper forms part of a much wider investigation into sugar diffusion; thus only preliminary results are presented.

Sieve Analysis Sieve analysis is a well-established and widely

applied procedure, and it was a logical step to apply it to the analysis of bagasse samples.

Bagasse samples were sieved in two stages; firstly in a sieving box containing three coarse screens for two minutes, after which the residue was transferred to smaller sieves and sieved for ten minutes. The methods of preparation of bagasse samples are given in Appendix I.

A typical cumulative size distribution is shown as curve A in figure 1, on log normal probability co­ordinates. The inflection in the curve corresponds to the change from large to small screens. In order to assess whether the inflection was due to sieving tech­nique or to some sudden change in shape factor at that point, the following procedure was carried out: any particle retained on one of the coarse screens which could have passed through that screen was pushed through by hand; sieving of the smaller par­ticles was then continued for a further 30 minutes.

The resulting size distribution is marked B in figure 1; this plots as a straight line and thus follows the log normal distribution law. In such cases, the mean size is obtained from the 50% point. In order to obtain a characteristic particle size from the sieve test, the straight portion of the curve A was projected as shown by the dotted line in figure 1. The point where this crosses the 50% horizontal was taken as the characteristic particle size. This procedure was applied to all the sieve tests, and characteristic sizes closer to the mean of the true distribution are obtained.

It is unlikely that anything other than relative values of bagasse particle size can be obtained by sieve analysis. As with all sieving operations, results depend on the time of screening, method of shaking, and screen loading. In sieving bagasse, further diffi­culties are encountered due to the fibrous nature of the bagasse; tangling between particles, sticking of particles to the screens, and high values of particle length to breadth ratios all lead to low sieving efficiencies.

It is only possible therefore to compare particle size in this way when identical sieving procedures are adhered to.

Displaceability Index The use of the Displaceability Index (DI) was first

reported by Payne6 as a direct measure of the avail­ability of sugar in bagasse. Since then, Markham4

has reported some results which show that DI depends on bagasse particle size.

The method of determining DI as proposed by Markham has been used here, except that brix values measured by means of a precision refractometer have been used instead of pol measurements.

Figure 2 confirms that a direct relationship exists between characteristic particle size and DI, which may be written in the form:

DI = kdc" (1)

where n has the value -0.275 and k is 88.0. It should be noted that these values of k and n hold only when dc is determined as described in the previous section.

The determination of DI is more accurate and reliable and less dependent on experimental tech­nique than the determination of dc, and thus it is felt that DI is a better method of characterization of cane preparation. Once again, the value of DI depends to some extent on the procedure employed; it is suggested that the procedure described by Mark­ham4 be standardized.

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Proceedings of The South African Sugar Technologists' Association — June 1970 65

Liquid Holdup Liquid holdup in a packed bed may be considered

as consisting of two parts, static holdup and dynamic holdup. Thus we may write:

HT = Hs + HD (2) Dynamic holdup may be thought of as a measure

of the amount of liquid flowing through the bed. Static holdup has been identified with stagnant pockets of liquid in the bed11, but perhaps a better idea is obtained by referring to observations by Shul-man et al.7 on the flow of dye injected into a packed bed. He observed semi-stagnant pockets of liquid, and splashing and the random motion of liquid over the packing surfaces deposited or removed dye from pockets by means of a slow random dilution process. Thus a certain amount of exchange of liquid between the flowing liquid and stagnant regions occurs.

A brief description of some of the published work on holdup follows, in the light of which the present holdup data may be discussed. Static Holdup

The static holdup is normally taken as being equi­valent to the adherent holdup, i.e., the residual liquid which remains in the bed on draining. This implies that Hs is independent of flow rate; however, one can envisage the volume of stagnant regions decreas­ing as the flow rate increases.

Gelbe3 states that the adherent holdup is equal to the highest value of Hs at zero throughput. If the influence of the flowing film on the static holdup is taken into account, the value of Hs decreases with increasing flow rate, approaching zero at a high enough flow rate. This is a more plausible point of view.

Published data on static holdup are characterized by a considerable amount of scatter. This data shows that Hs is strongly dependent on packing material, shape and size7'9, and also when adherent holdup is considered, on conditions in the packed bed before draining10.

It has been shown that static holdup should depend on We/Fr, i.e., the ratio of Weber to Froude num­bers3'10. This ratio represents the ratio of gravity to surface tension forces. Dynamic Holdup

Dimensional analysis leads to the following rela­tion for HD

5: HD = f(Fr/Re, Re) (3)

where Fr and Re are the Froude and Reynolds numbers respectively. The most general correlations which have been proposed for HD are of this form2, but scatter is still up to approximately 20 %.

Shulman et al.7'8 found dynamic holdup to be independent of packing shape and material. This supports a theory proposed by Davidson2 that all random packings of a given size are equivalent to a series of sloping surfaces which are indistinguishable from one another. According to Davidson's model, for liquid in laminar flow.

HD = f r(Re)i "I (4)

where Gr is a modified Grashof number.

Gelbe3 reduced the scatter in correlation of dyna­mic holdup data by assuming that Hs varies with flow rate. He proposed the following correlation:

*>-'(£)"" [£]-«* (5)

where S is a shape factor. For Re< 1, where the influence of inertia is negligible, n = l / 3 (cf Davidson2), and for R e > l , where inertia increases and viscous drag decreases, n—5/11.

A number of other correlations have been pro­posed. These will not be discussed here, save to point out that the dependence of HD on flow rate has not been established satisfactorily.

Experimental Liquid Holdup Results A brief description of the pilot plant diffuser is

given in Appendix II.

Dynamic Holdup This was calculated as the product of mean resi­

dence time and flow rate once steady state flow conditions were achieved. Mean residence time was taken as the time interval between injection of a dye into the top of the bagasse bed to the peak in outlet dye concentration. Experimental results are shown in figure 3. These data were obtained with bagasse bed heights varying from 30" to 35". The temperature of the percolating juice was 75°C; a few points obtained at 60°C and 90°C are included in figure 3 as they showed no significant variation. Flooding occurred at values of HD = ca. 300 lb.

A marked effect of cane preparation can be seen, and four curves can be drawn through the data for the four types of preparation used (see Appendix I). A certain amount of scatter can be observed, which is to be expected as significant variations between bagasse samples occur even with the same method of preparation.

It is clear from the preceding discussion that if constant liquid properties are assumed, HD is a function of flow rate and particle size only. Asssuming DI to be a measuring of* particle size, a correlation of the following form is indicated:

HD = AL» DIm (6)

where A, n and m are constants. Multilinear regres­sion analysis showed L and DI to be significant at the 0.5% level. "Values of A, n and m, and their standard deviations are given in Table I.

A more general form of correlation was obtained as:

HD 1 = A1 L"1 DIml (7)

where HD 1 is defined as holdup per lb. fibre. The corresponding value of the constants are given in Table I. In both cases dynamic holdup can be pre­dicted with a standard deviation of 15%. Thus a usable correlation for dynamic holdup has been obtained, but indicates perhaps that DI alone is not sufficient to specify the dependence of HD on particle size.

The values of n and n1 as given in the Table lie in between the values of exponents on flow rate

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66 Proceedings of The South African Sugar Technologists'' Association — June 1970

(or Re) of 5/11 proposed by Gelbe3 and 0.75 proposed by Mohunta and Laddha5.

Static Holdup

Consideration of the nature of bagasse leads one to expect significantly higher values of the static holdup in a bed of bagasse than in a bed of conven­tional packing materials used in absorption or distil­lation, to which most data on holdup refer. This is due to the complex shapes of the bagasse particles and the affinity of bagasse for water, and the error involved in assuming Hs equal to the adherent holdup is greater in this case than with conventional packing materials.

Values of Hs were calculated by subtracting the dynamic holdup from the total holdup, which could be readily obtained from the weight of the contents of the diffuser. Experimental data are shown in figure 4. Again a dependence on flow rate and cane preparation can be observed. The scatter is more pronounced in this case, which on the basis of the preceding discussion is not unexpected; static holdup is a function of particle shape and size.

Values of the ratio of adherent holdup to fibre varied from 5 to just over 6. No significant trends could be discerned, other than a slight dependence on cane preparation. It can be seen from figure 4 that extrapolation to zero flow rate leads to a value between 5 and 6, thus supporting the contention that adherent holdup is equal to H3 at zero throughout3.

A correlation of static holdup/fibre ratio in terms of flow rate and DI was obtained by multilinear regression:

Hsx = B LP DI< (8)

Values of the constants B, p and q are given in Table I. It was found that DI is significant at the 0.5 % level, and L at the 5 % level. The standard deviation in predicted values of Hs1 is 19%.

Discussion The relations given above for holdup will be in­

fluenced by the density of packing and bed height. Nevertheless, it is probable that the relationship be­tween holdup, L and DI will still have the same form. Further, in the case of different liquid properties, different holdup values will be obtained. The effect of varying properties on liquid holdup has been thorough­ly investigated by Shulman et. al.7'8.

Residence time of juice in diffusers has assumed a new importance recently; high residence time systems are associated with the production of more molasses and a consequently higher loss of sugar. The implica­tions of a high static holdup are that some of the juice may remain in the bed for a long period of time, and have a far greater than average residence time in the bed. Higher static holdups are associated with coarser preparations; however, the total holdup of juice is less than that obtained with finer preparations. Higher flow rates significantly reduce the static holdup.

Conclusions 1. The fact that a relationship exists between DI and

particle size has been confirmed. Values of the constants in this relationship will depend on the method used to characterize particle size.

2. DI is a more reliable measure of cane preparation than particle size. Since it is still a relative measure of cane preparation, values of DI depend on the method of determination.

3. Static and dynamic holdup exhibit a strong de­pendence on cane preparation.

4. Both static and dynamic holdup depend on flow rate. The ratio HD/HS increases markedly with flow rate.

5. DI has been used as a measure of cane prepara­tion to provide working correlations to predict holdup in fixed bed diffusers.

Acknowledgements The author wishes to express his thanks to Mr. M. R.

Joyce for his help in obtaining the experimental data, to Mrs. R. Wilkes who was responsible for the fine sieving tests, and to Mr. C. M. Young of Hulsmith for carrying out the multilinear regression analyses.

Further, the author is indebted to the Manager and Staff of Hulett's Mount Edgecombe Mill for their help and co-operation.

Finally, the advice and encouragement of Professor E. T. Woodburn and Dr. B. V. Preen are gratefully acknowledged.

Nomenclature DI = displaceability index dc = characteristic particle size (mm or ft) dD = particle size (mm or ft)

Vs

Fr = Froude Number = gdp

g = acceleration due to gravity (ft/sec2) Gr = modified Grashof Number = gdp

3 p2

HT = total holdup (lb) HQ = dynamic holdup (lb) Hs = static holdup (lb) HD 1 = HD/lb fibre Hs1 = Hg/lb fibre L = liquid mass velocity (lb/min ft2) Re = Reynolds Number dp L

V-V = Velocity of liquid based on empty column (ft/sec) We = Weber number = V2 pdp

tx = liquid viscosity (lb/min ft) p = liquid density (lb/ft3) cr = surface tension (lb/ft)

References 1. Buchanan, J. E., Ind. Eng. Chem. Fundam., 1967, 6,

400. 2. Davidson, J. F., Trans. Instn. Chem. Engrs., 1959, 37,

131. 3. Gelbe. H., Chem. Eng. ScL, 1968, 23. 1401 4. Markham, R. G., Proc. S. Afr Sug. Technol. Assoc,

1969, 43, 230. 5. Mohunta, D. M., and Laddha, G. S., Chem. Eng. ScL,

1965, 20, 1069. 6. Payne, J. H., Repts. Hawaiian Sug. Technol., 19 Ann.

Meeting, 1960, 107.

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Proceedings of The South African Sugar Technologists' Association —

7. Shulman, H. L., Ullrich, C. F., and Wells, N. A., A.I. Chem. E. Jl., 1955, 1, 247.

8. Shulman, H. L., Ullrich, C. F., Wells, N., and Proulx, A. Z., A.I.Chem. E. Jl., 1955, 1, 259.

9. Standish, N., Chem. Eng. ScL, 1968, 23, 945. 10. Turner, G. A., uad Hewitt, G. F., Trans. Instn. Chem.

Engrs., 1959, 37, 329. 11. Van Swaaij, W. P. M., Charpentier, J. C, and Viller-

maux, J., Chem. Eng. Sci., 1969, 24, 1083.

TABLE I Values of regression coefficients and standard deviations for

equations (6), (7), and (8).

A n m

A1

n1

m1

B P q

Regression Coefficient

0.010 0.472 1.887

0.00052 0.494 1.728

1780 -0.154 -1.306

Standard Deviation

0.048 0.153

0.048 0.155

0.059 0.189

APPENDIX I

Preparation of bagasse samples Bagasse samples were taken from the milling tan­

dem at Mount Edgecombe after the first mill. The bagasse could then be further prepared by the use of a small Hippo Mill, a fixed hammer shredder, with provision for the introduction of screens on the outlet in order to attain finer preparation.

The various degrees of preparation referred to in the text are:

PI First mill bagasse. P2 First mill bagasse, after passing through

the Hippo mill without a screen. P3 As above, but with a coarse screen in the

. Hippo mill. P4 As above, but with a fine screen.

APPENDIX II

Description of the pilot plant diffuser The diffuser consisted of a 2 ' D. mild steel column

6' high. The bagasse bed rested on a screen located towards the bottom of the column. The diffuser itself rested on three knife edges; two of them rested on a rigid supporting framework on one side of the column, and acted effectively as a pivot. The third

— June 1970 67

knife edge was attached to a Phillips PR 6101P/02HK load beam; any increase in weight in the diffuser increased the force on the load beam. This produced a signal proportional to the force, which was led to a recorder. Thus the weight of the contents of the diffuser could be continuously monitored.

The weight of the vessel itself was counter balanced by means of a weight-and-pulley system. A fine tare adjustment on the power supply to the load beam enabled accurate elimination of the weight of the vessel for recording purposes.

In operation, water or juice was pumped from a stirred thermostatistically controlled tank through a flow controller and into a flow distributor, suspended independently of the diffuser just above the bagasse bed.

At the commencement of a run, the weight was observed to increase; after a few minutes, the weight tended to a constant value, indicating steady state flow conditions. All holdup data reported here referred to steady state operation only.

Discussion Mr. Bruijn (in the chair): Do you favour a coarse

or fine preparation for diffusion? Mr. Rein: I suggest somewhere in between. If it is

too fine, the maximum flow rate is limited. On the other hand, if it is too coarse the extraction will be low.

Mr. Bruijn: Is not the flow rate connected with the type of diffuser, or does this apply to all diffusers, i.e. does it only apply to a percolation diffuser.

Mr. Rein: This applies mainly to percolation diffusers.

Mr. Jullienne: No mention is made in the paper of the effect of air locks. Was this investigated.

Mr. Rein: This was not investigated. It is more important when flooding occurs but as these data were taken when the bed was not flooded, air locks should have little effect.

Mr. Renton: Mr. Rein says that in the case of static hold up some of the juice may remain in the bed for a long time, i.e. longer than the usual residence time.

Percolation bed diffusers have a higher juice re­tention than fibre retention. Therefore, if there is static hold up, does this juice have less residence time than juice that is percolated.

Mr. Rein: The boundary between static and dyna­mic hold up is not absolutely defined, and there is interchange between the two.

Some parts of static hold up will be more firmly held in bagasse beds than others and it is those parts which are most firmly held that might be caught in the bed near the beginning of the diffuser, be taken to the end, and recirculated to the beginning.

Page 83

68 Proceedings of The South African Sugar Technologists' Association June 1970

90

80

70

UJ

IM CO

cc UJ

o 2

I.V h-X C3

60

RO

40

30

?o

10

^

^,+JT

J*? ^T

^c^ ^^^

^X

s&

s , Sk

0.4 0.5 1.0 2.0 3.0 4.0 5.0

SCREEN MESH OPENING (mm.) FIGURE I

100

90

80

70

Q 60

50

40

10.0

** I * \ i ^ % ^ ^

^^5^i ^ ^ «

• >

0.8 1.0 2.0 3.0 4.0 5.0

CHARACTERISTIC PARTICLE SIZE (mm.) FIGURE 2

Page 84

Proceedings of The South African Sugar Technologists' Association — June 1970 69

300

100 200

FLOW RATE (Ib./min.)

FIGURE 3

i 300

Page 85

70 Proceedings of The South African Sugar Technologists'1 Association —June 1970

t 4 CO

Q. 3 Q _ j

° 3 y i -< h-

_ ^ 3 o—• —.

x + V

^ 1 N*

\

)

C \

\ •

\ «

\ i

\

X '

X

\ x

\

•

\

\

o -^

0

• o

©

- ^ %

D

\

+

o

o

^

" O " "»

\

+ ^

o p 1

+ p o L

• P3

x PA

I

O

• ^

0

100 200 FLOW RATE (Ib./min.)

FIGURE 4

300

ik

Page 86

Proceedings of The South African Sugar Technologists' Association — June 1970 71

THE MUTUAL CLARIFICATION PROJECT-PROGRESS REPORT No. 2

By L. M. S. A. JULLIENNE*, M. MATIC and M. TEOKAROVIC

Sugar Milling Research Institute

Abstract Data collected in connection with the Mutual

Clarification Project during the 1969-70 season are presented and discussed in relation to juice and sugar quality. An explanation is offered for partial removal of starch which happens in the factories not using a specific removal process. The results of a factory test comparing liming at the boiling point of juice with the normal liming method are reported.

Introduction Ten factories submitted data required for the

Mutual Clarification Project during last season and weekly summaries were regularly issued by the Sugar Milling Research Institute from August onwards. Details of participating factories (and lengths of their contribution) are summarised in Table 1. Although several mills continued crushing during January 1970, the week ending 4th January, 1970, was used as a closing week for the purpose of calculating average performance figures.

The procedure followed and the analytical methods used in this project have been described in the pre­vious report (1).

TABLE 1 Factories Participating in M.C.P.

Factory EM

No. of weeks 18

Period 2.8.69 7.12.70

Factory

Mixed Juice P 2 0 6 ppm/juice

Starch ppm/Bx

Purity

Clear Juice P 2 0 5 ppm/juice

Ca (Mg) ppm/juice

Starch ppm/Bx

Suspended matter % clear juice

Turbidity

FX

25

23.8.69 8.2.70

Max. Av. Min.

Max. Av. Min.

Av.

Max. Av. Min.

Max. Av. Min.

Max. Av. Min.

Max. Av. Min.

Max. Av. Min.

AK

28

2.8.69 8.2.70

DL

28

GH

24

2.8.69 16.8.69 8.2.70 1.2.70 30

JB

17

2.8.69 .11.70

TABLE 2 Analysis of Mixed and Clear Juices

EM

250 229 200

2075 1704 1150

83.16

40 31.7 20

—

1590 1238 700

.023

.010

.006

85f 77.3 74

FX

324 308 288

2182 1852 1490

83.54

64 57.3 52

700 558 507

1570 1255 1000

.473

.050

.008

.710

.516

.330

AK

237 193 124

2865 2137 1560

84.48

76 58. 32

590 565 549

1847 1325 853

.020

.011

.007

.270

.219

.190

DL

230 192 139

2092 1725 1494

84.71

51 3 40.5

3!

552 527 488

1668 1409 1158

.042

.032

.018

.200

.141

.110

GH

280 267 230

2032 1514 762

85.00

51 48.5 40

—

1550 1019 529

.037

.025

.018

.330

.247

.180

TS

18

2.8.69 18.1.70

JB

143 129 115

2095 1668 1362

82.00

36 30.6 29

841 613 560

879 678 592

.043

.030

.014

.290

.274

.260

ME

24

2 .8 . 11 .1 .

TS

303 264 228

2360 1620 1189

84.87

55 44.1 38

680 641 580

1523 1271 922

.029 ...013

.005

.320

.202

.140

IL

20

69 2.8.69 70 4.1.70

ME

272 209 170

2470 1716 1060

83.63

85 39.5 15

710 642 539

2130 1553 1200

.240

.095

.017

.380

.250

.180

IL

188 156 125

2470 1237 869

84.10

UK

28

2.8.69 8.2.70

UK

335 318 290

2175 1859 1316

87.18

45 44 34.3 33.8 28 30

864 689 525

894 690 497

.066

.034

.012

624 583 546

892 628 305

.090

.034

.010

.440

.285

.200

•Present address—The Tongaat Sugar Co. Ltd. fKopke

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72 Proceedings of The South African Sugar Technologists' Association — June 1970

Results and Discussion

General A survey of participating factories was carried out

during the season and the information relevant to M.C.P. is summarised below:

All factories extract juice by conventional milling, the only exception being EM, which uses diffusion. In the latter case, the press water is limed to pH 7.0 and returned to the diffuser. At JB and 1L starch removal, using enzymes present in the juice, is prac­tised. Lime is added to the mixed juice to bring the pH to 6.0, after which the juice is kept in retention tanks for eight minutes at 70°C. At UK starch is removed from the mixed juice by the Rabe process. All other factories, except ME, use the starch removal processes in the syrup stage.

The juice is heated to boiling point and flashed be- • fore liming at EM, FX, AK, DL, TS and ME. At JB lime is added to boiling juice before the flash tank and IL practises the conventional liming method. The juice leaving the vacuum clarifier at UK is heated to boiling point and flashed before being sent to subsidisers.

The pH of muds is brought up to 7.0 at JB and the pH of filtrate to 7.5 at IL by the addition of lime. Flocculant is also used. No chemicals are added to the muds at other factories.

Mixed Juice and Clear Juice The average analytical values of various para-"

meters determined in mixed and clear juices are presented in Table 2. In order to give an indication of the fluctuations which occurred, the maximum and minimum values obtained are also recorded. The average analytical figures for sugars (affinated) produced by the participating mills in the period under review are reproduced in Table 3.

TABLE 3 Analysis of Affinated Sugar (Average Values 31.12.69)

EM FX AK DL GH JB TS IL UK

ppm

950 1012 660 710 894 987 860

1016 910

ppm

245 165 76 95

187 135 133 135 149

ppm

32 31 22 35 16 20 30 25 18

°/o

0.076 0.084 0.047 0.068 0.057 0.074 0.071 0.050 0.049

% 39 44 55 48 48 41 52 41 38

The amount of phosphate present in mixed juice fluctuated considerably at all factories but on the whole was reasonably high. Two exceptions were JB and IL, where the phosphate was consistently low. Mono-calcium phosphate as well as flocculant were therefore regularly added to the mixed juice at JB. At IL only flocculant was used. Although UK had the highest P2Os content of mixed juice, both phos­phate and flocculant were continuously added in

order to fulfil the requirements of the Rabe process. TS used flocculant only intermittently. The average consumption of these chemicals and of lime by various factories is given in Table 4.

TABLE 4 Consumption of Chemicals (Average)

Factory

EM FX AK DL GH JB TS ME IL UK

kg lime/ metric ton cane

0.58 0.53 0.51 0.53 0.55 —

0.60 0.54 0.52 0.51

* Seven weeks only ** One week only

kg phosphate/ metric ton cane

0.089 —

0.053** —

0.079

Flocculant, ppm mixed juice

3.61 0.47* 5.00** 5.02 6.75

There is no correlation between the soluble phos­phate content of clear juice and the amount of inorganic P2Os found in the affinated sugar. This is illustrated in Fig. 1, where the factories are arranged in a descending order of phosphate crystal content. If the level of phosphate in clarified juice is taken as an index of the efficiency of juice clarification, as is sometimes done (4), one will have to conclude that clarification at, for example, AK and GH was not very good. Yet the phosphate contents of their crys­tals were low. In contrast, at DL phosphate in the clear juice was considerably lower than in the above two factories but phosphate in crystal was the highest recorded. It appears therefore that, within limits, boiling house work plays a more important role in determining the amount of P3Os included in the crystal, than does clarification.

The level of phosphate attained in clarified juice seems to be dependent on the amount of soluble phosphate present in mixed juice. Why this should be so is not clear, as better phosphate removal would be expected in the case of mixed juices rich in phos­phate. In this connection the good performance achieved by IL is particularly surprising.

As expected, a reasonably good correlation (correlation coefficient 0.63) was found between the suspended matter present in clear juice and the filter-ability of affinated sugar (Fig. 2a). This was also true, although to a smaller extent, in the case of ash in sugar (Fig. 3a). The importance of efficient clari­fication if good quality sugar is to be produced is therefore obvious. In this connection it would appear (Table 2) that clarifier capacities at EM and FX are not adequate.

If FX is excluded, there was also a correlation between turbidity of clear juice and filterability of sugar (Fig. 2b). However, the influence of turbidity on the ash content of affinated sugar seems to be negligible (Fig. 3b).

The average Ca (Mg) content of the clarified juices was about 600 ppm (Table 2) but varied considerably not only between factories but also within one fac-

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Proceedings of The South African Sugar Technologists' Association

tory. The smallest fluctuations were recorded at AK, DL and UK and the largest at IL and JB. Somewhat surprisingly, no correlation was found between Ca (Mg) content of clear juice and percentage ash in affinated sugar (Fig. 3c). A possible explanation for this may perhaps be found in the fact that the greatest single component of the ash in sugar is potassium (3), and the contribution of Ca (Mg) is therefore somewhat obscured.

Starch Removal In the last report (1) attention was drawn to the

fact that a considerable but erratic drop in starch content between mixed and clear juice is recorded in the factories which are not using any specific method to accomplish this removal. As shown in Table 5, the elimination of as much as 45% of the starch present in mixed juice has been recorded this season. In order to explain this disappearance of starch, an investigation was carried out at AK.

TABLE 5 Per cent Starch Removal between MJ and CJ

Factory

AK TS DL FX ME

June

44.8 27.4 31.3

July

44.1 4.6

27.2

Aug.

42.0 10.5 22.9

Sept.

43.0 10.5 14.3 33.6 25.0

Oct.

38.0 25.5 13.5 29.7 10.0

In the first part of this investigation it was estab­lished that no significant starch removal takes place in the clarifiers. This is apparent from Table 6, where the results of starch analysis on daily com­posite samples of mixed juice, limed juice, clear juice and returned to Oliver filtrate are reproduced. A small amount of starch is removed in the muds as indicated by the analysis of limed and clear juices and this would explain the fact that the starch con­tent of the returned filtrate is higher than that of the clarified juice. It is clear, however, that the bulk of the starch is decomposed before juice reaches the clarifier and for this reason the tank situated under the mixed juice scale and into which Oliver filtrate is returned was next investigated. For this purpose continuous hourly samples of mixed juice and returned Oliver filtrate reaching the tank, and of a mixture of the two leaving the tank, were analysed for starch content. The results are reproduced in Table 7. The large difference between the "expected" starch content of the mixture of mixed juice and filtrate (calculated from brix and starch balances) and that actually found is a clear indication that the removal is taking place during the retention time of the juice in the tank.

It was found that the mixture of mixed juice and returned filtrate at an average temperature of 40 °C and pH 5.5 remains, under normal working condi­tions, two to three minutes in the tank before it is pumped to the heaters. One would therefore expect that under those conditions the soluble starch

June 1970 73

TABLE 6 Daily Composite Starch Figures at AK

Stream

Mixed juice Limed juice t learjuice Filtrate

Mixed juice

Filtrate

Mon.

1695

1230 1560

Starch, ppm

Tues.

1620 1132 1078 1280

Wed.

2015 1200 1173 1500

Thur.

2220 1680 1500 2420

TABLE 7 Continuous Hourly Samples at AK

MJ + F (after tank)

Expected MJ 4- F

% Removal n tank

1

1468

784

878

1 390

33

Starcr , ppm /Bx

2

1 300

1010

907

1275

28

Fri.

2440

1250 1920

3

1 355

1 172

1228

1340

8

returned in the filtrate would be efficiently hydro-lysed by the enzymes present in the mixed juice. This hypothesis was tested in the laboratory experiment which simulated factory conditions. Mixed juice con­taining 15% filtrate (average undiluted filtrate % mixed juice at AK is 17.1% — see Table 10) and adjusted to pH 5.5 was placed in a thermostatically controlled heated tank and kept at 40°C. Samples of the mixture were collected at intervals and analysed for starch. The results- reproduced in Table 8, confirmed that a starch removal in excess of 40% could be obtained under such conditions.

TABLE 8 Starch Removal — Laboratory Experiment

(Mixed juice containing 15% filtrate; temp. 40°C; pH 5.5)

Time

0 min

0.5 „

2.0 „

5 0 „

8.0 „

15.0 „

Starch, mg/1

0.41

0.33

0.24

0.19

0.19

0.19

% removal

—

19.6

41.5

53.7

53.7

53.7

It would appear therefore that the recorded differ­ences in starch content between mixed juice and clear juice are due to the enzymatic hydrolysis of the soluble starch in the returned filtrate which takes place in the tank situated under the mixed juice scales. The difference in the magnitude of the removal at various mills can be explained by the fact that normal working conditions vary from fac­tory to factory, i.e. different enzyme content of juice, different amount of filtrate containing soluble starch,

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74 Proceedings of The South African Sugar Technologists' Association — June 1970

different pH and temperature and different tank dimensions giving variable retention times.

pH Data The pH's of the treated juice, clear juice and syrup

recorded by various mills are summarised in Table 9. The low pH of syrup at FX as well as the high pH of syrup at UK are worth noting.

The considerable fluctuation in the pH of treated juice at ME, where automatic liming is not practised, was confirmed by three-hourly continuous pH record­ings. Differences of up to one pH unit were obtained in these runs. A closer investigation of the pH control even in the factories which have automatic liming systems will be rewarding. In a number of cases the electrode is situated too far from the point of lime addition, resulting in a significant response lag.

Performance of Filters Information on filter station performance is pre­

sented in Table 10. In view of the uncertainty about the accuracy of

figures supplied, it is difficult to discuss the results. It would appear from the figures returned that at several factories retention of filters was on the low side despite a satisfactory average per cent suspended solids in muds. If the latter figures are correct either insufficient bagacillo was added to muds or possibly the bagacillo was too coarse. These and other points need closer investigation and a further study of indi­vidual filter stations is clearly indicated.

Comparison of "Hot" and Normal Liming In both Australia and Mauritius (2) the opinion is

strongly held that liming at the boiling point of juice results in better clarification and sugar of higher quality. A limited amount of laboratory work carried out previously in South Africa did not support this view. It was therefore decided to undertake- as part of this project, an investigation into the relative merits of liming at the boiling point of juice (referred to here as hot liming) and liming at about 70°C (referred to here as normal liming).

At the beginning of the last season UF switched from normal to hot liming. However, the facilities for normal liming are still available at this mill and thanks to the co-operation of the factory, which agreed to apply over a period of eight weeks hot and cold liming alternately, a controlled factory scale test was arranged.

Hot liming is carried out at UF at 102°C. Lime at 6° Be, fed by gravity from an automatically con­trolled splitter box, is introduced into the juice line about 300 mm before the flash tank. After flashing, the juice flows through a pipe with mixing baffles for a distance of 2 m and eventually reaches a distri­bution box from where it is fed to clarifiers. The pH electrode, situated in the distribution box, is 6 m distant from the flash tank. This represents about 40 seconds juice retention time. The splitter box is operated by a Leeds and Northrup pH controller through an electrical servo-motor. The limed juice is normally kept at pH 7.3-7.4, which results in a clear

TABLE 9 pH Data

Factory

Treated juice

Clear juice

Syrup

Factory

% Suspended solids in mud

Retention

Undiluted filtrate % mixed juice

Filter cake % cane

Max. Av. Min.

Max. Av. Min.

Max. Av. Min.

Max. Av. Min.

Max. Av. Min.

Max. Av. Min.

Av.

EM

8.1 8.0 7.9

7.4 7.2 7.2

6.6 6.4 6.3

EM

10.8 8.6 6.8

80.7 79.2 77.4

14.8 11.7 7.8

3.22

F X

8.0 7.9 7.8

7.3 7.2 7.1

6.5 6.3 6.2

AK

8.3 8.1 8.0

7.6 7.4 7.2

6.7 6.6 6.5

DL

8.1 7.8 7.7

7.7 7.3 7.1

7.1 6.5 6.2

TABLE 10 Filter Station Performance

FX

5.9 5.1 1.2

86.2 69.7 59.0

55.8 57.3 44.7

6.00

AK

5.2 4.5 3.9

86.2 78.1 75.1

40.7 17.1 10.1

5.07

DL

5.4 4.1 3.3

93.2 90.7 87.7

—

5.06

GH

8.0 7.9 7.6

7.5 7.3 7.3

6.9 6.8 6.7

GH

7.3 6.1 4.3

89.4 83.3 79.1

4.70

JB

8.5 8.3 8.2

7.7 7.5 7.4

6.8 6.6 6.5

JB

10.0 8.1 6.4

91.7 89.4 86.1

16.1 12.8 8.6

4.54

TS

8.2 8.0 7.9

7.3 7.2 7.2

6.7 6.5 6.5

TS

8.3 6.8 5.5

79.4 70.7 62.6

35.8 18.1 5.3

3.32

ME

8.3 8.1 7.2

7.4 7.3 7.2

6.6 6.4 6.2

ME

13.0 9.4 7.3

86.1 76.8 61.5

19.7 15.8 13.0

5.94

1L

8.0 7.9 7.9

7.6 7.4 7.3

6.9 6.7 6.7

IL

9.9 7.7 5.5

87.8 79.6 69.5

22.4 18.6 4 .3

3.53

UK

8.2 8.1 8.1

7.8 7.6 7.4

7.4 7.2 6.8

UK

16.0 8.9 5.0

96.0 92.9 88.6

18.6 14.9 11.4

4.00

Sucrose % filter cake Av.. 0.80 1.65 1.49 1.32 1.46 1.76 1.68 0.89 1.47 1.61

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Proceedings of The South African Sugar Technologists' Association — June 1970 75

juice of pH 6.8-6.9. The control system keeps this latter pH within very close limits.

The normal liming is carried out at 70°C in a tank equipped with a stirrer. Retention time in the tank is approximately four minutes. The limed juice is pumped through a secondary heater into the flash tank, from where it follows the same path as described above. The pH of the limed juice is 7.5-7.7, resulting in a clear juice pH of 7.0-7.1.

The change from one liming method to the other was effected every second Friday. Sampling com­menced on Monday following the change and the analyses were carried out on the following:

(a) mixed juice—daily composite, (b) limed juice (taken from distribution box)—

four catch samples daily, (c) clarified juice—daily composite (d) mud (taken before addition point of bagacillo)

—daily composite of four catch samples, (e) filtrate from Oliver filters—daily composite,

TABLE 11 Clarification Data (UF)

P206 mg/1 MJ

Sulph. Ash % MJ

P2Os mg/1 CJ

Sulph. Ash % CJ

Colour CJ

Turbidity CJ

% Suspended solids in muds

Retention of filters

"Hot" Liming

2 weeks average

209

0.470

21.0

0.516

0.35

0.15

5.0

87.2

Normal Liming 2 weeks average

200

0.472

17.8

0.521

0.72

0.46

6.0

89.9

"Hot" Liming 2 weeks average

207

0416

19.9

0.467

0.43

0.25

4.5

82.8

TABLE 12 Analysis of Affiliated Sugar (UF)

Normal Liming 2 weeks average

212

0.407

23.2

0.482

0.70

0.60

7.1

86.6

"Hot" Normal "Hot" Normal Liming Liming Liming Liming 2 weeks 2 weeks 2 Weeks 2 weeks average average average average

Gums, ppm 667 800 725 550

Starch, ppm 42 68 35 50

P205 Inorg., ppm 17 13 13 18

P a05 Total, ppm 27 23 23 20

Ash (S04) % 0.108 0.085 0.080 0.130

Ca, ppm 139 146 160 135

Mg, ppm 21 17 21 19

Colour (unaffinated) 0.27 0.24 0.23 0.21

Susp. matter % 0.013 0.020 0.015 0.010

Filterability 43 48 51 49

(f) sugar—weekly composite. The results are reproduced in Tables 11 and 12. It is apparent from Table 11 that there was a

significant difference in respect of colour and tur­bidity of clear juices produced by the two liming methods. In both cases better juice was obtained by hot liming. However, normal liming resulted in higher solids in muds despite a decrease in flocculant addition (3.4 ppm for hot liming and 1.9 ppm for normal liming). This was confirmed in laboratory settling experiments using limed juice (Fig. 4) during which mud volume after 120 minutes was found to be 30% smaller in the case of normal liming. It appears also that slightly better filter retention was obtained when the normal liming method was used.

In contrast, the results of the analyses of affinated sugars produced during this period (Table 12) were remarkably uniform. No significant differences in either filterability or colour were found. It would appear from this investigation that the method of liming has little influence on sugar quality. However, further experiments must be carried out before final conclusions on the merits of hot liming are arrived at.

Conclusions As stated already in the previous Progress Report,

the basic aim of the M.C.P. was twofold: to point out sources of inefficiency in the clarification process and to provide information necessary for effecting improvements. The first part has now been largely fulfilled. Further accumulation of weekly data has become unnecessary and will be discontinued.

Filter stations and pH measurement have emerged as two obvious subjects for further study. Additional work is also required in connection with hot liming. It is therefore proposed to concentrate on these aspects of the M.C.P. in the coming season and in this way it is hoped to achieve the second part of the basic aim.

Acknowledgements Our thanks are due to personnel of all factories

which submitted data during last season and particu­larly to the management and staff of Amatikulu and Umfolozi mills, without whose help a part of this work could not have been carried out.

REFERENCES

1. Buchanan, E. J., Graham, W. S., Jullienne, L. M. S. A., Matic, M., 1969. Mutual clarification project—progress report No. 1. Proc. S. Afr. Sug. Technol. Ass. 43 (1969), 190-198.

2. Dupont de St. Antoine, J., 1969. Measures taken in Mauritius to improve raw sugar filterability. Int. Sug. J. 71 (1969), 40-44.

3. Honig, P., 1953, Principles of Sugar Technology, Vol. 1, 291.

4. Laboratory Manual for Queensland Sugar Mills, 1970, Bureau of Sugar Experiment Stations, Fifth Edition, Brisbane (1970), 129.

Discussion Mr. Bruijn (in the chair): There are correlations

between the properties of clear juice and the quality of raw sugar, although they may not be very good.

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76 Proceedings of The South African Sugar Technologists' Association —June 1970

Has not the importance of clarification been over­rated and should we rather not be studying the boiling and crystallisation stages?

Dr. Matic: It is mentioned in the paper that once a certain level of clarification has been achieved, what­ever that level may be, then the boiling house opera­tions are very important.

If the juice is badly clarified and full of suspended matter, then of course there will be an effect on the final product.

Dr. Graham: It is stated that at Umfolozi lime is fed by gravity into the juice line before the flash tank. Is this correct?

In table 11 the colour figure given for hot liming is very low. The pH also has a marked effect on colour measurement and has this been taken into account?

When turbidity was measured, was compensation made for colour?

In this paper when hot liming is mentioned, it does not refer to saccharate liming.

What is the pH of mud at Jaagbaan that it has to be brought up to 7.0?

Why is the pH of the clear juice at Illovo brought up to 7.5?

Dr. Matic: I will answer the questions in reverse order.

The figures reported in the paper are as reported by the factories and they have been averaged.

Colour and turbidity were determined by standard methods and the pH has been adjusted as is normally done in colour measurement.

Mr. Conijn would perhaps explain the arrangements of Umfolozi.

Mr. Bruijn: The turbidity was measured by filtering off some of the juice and using the filtered juice as a blank, so colour was compensated for by the filtered solution.

Mr. Conijn: At Umfolozi, we do not inject into the flash tank but into the feed pipe about one foot from the flash tank, by gravity feed.

Mr. van Hengel: The pH's at Umfolozi of 6.8 and 6.9 when using hot liming and 7.0 and 7.1 when using normal liming, are considerably lower than other fac­tories, i.e. Umzimkulu 7.6.

I think we should look critically at clarified juice pH and the resulting syrup pH. To take Umzimkulu as an example, I do not think it necessary to keep the pH of the syrup as close to 7.0 as possible at this temperature.

I think that, provided there is reasonable clarifi­cation, the pH of the syrup or clarified juice has an influence on whether or not free flowing C massecuites will be obtained.

Mr. Thumann, formerly of Umfolozi, and his suc­cessor, Mr. Conijn, I am sure agree with me on this.

Mr. Conijn: I think the pH should be kept as low as possible because of the effect on the colour of the sugar.

Mr. Jennings: The low syrup pH at Felixton corresponds with the best non-sucrose ratio for Natal factories and the high pH at Umzimkulu corresponds with the highest non-sucrose ratio for factories con­tributing to the M.C.P.

When the M.C.P. was first discussed, some tech­nologists were critical of the decision to base all the conclusions on quality of sugar and I think the results have proved them right.

The crystallisation stage appears to be of over­riding importance. Is it not possibly time to start a Mutual Crystallisation Project?

Some data on molasses should also have been sub­mitted to the M.C.P.

Dr. Matic: It is possibly premature at this stage to start a Mutual Crystallisation Project, but I agree that crystallisation should be studied.

Data on molasses have not been included because they are presented in the next paper.

Consideration was given to including in the M.C.P. data on syrup analysis, but it was decided that the response from factories would be poor if too much was requested of them.

We did compare results from syrup as opposed to clear juice, using data from Hulett factories. Plotting of calcium and magnesium in clear juice against sul-phated ash in syrup gave poor correlation, when ash in syrup was compared with conductivity ash in crystal, a resonably good correlation was obtained.

I therefore do not think we have lost much by not including figures for syrup.

Mr. Alexander: Were the analyses performed on juices at the factories comparaible, as otherwise the conclusions drawn may not be justified?

At least syrup samples could be analysed at one point and would therefore be comparable.

In figure 3, turbidity of clarified juice and suspended matter in clarified juice is plotted against conductivity ash in afrinated sugar — what is the connection be­tween the two? Turbidity and suspended matter are insoluble materials in the juices, whereas conductivity in afnnated sugar must result from ionised material. Is it expected that suspended matter at some stage goes back into solution to contribute towards the conductivity ash?

Dr. Matic: I think your suspicion regarding the analyses might be correct. We looked into the ways certain parameters were analysed and there are differences between factories, so correlations could be affected. Unfortunately, in these co-operative efforts it is difficult to force factories to do everything as you would like it done. However, our conclusions are only tentative and really indicate trends only.

Regarding turbidity, suspended matter and con­ductivity ash, one would expect the conductivity ash to result from soluble inorganic material. These graphs were plotted to indicate trends and were pre­sented without trying to explain why turbidity and suspended matter appeared to show some correlation with conductivity ash.

Mr. Jullienne: Could not the inslu'ble P2Or> in the clear juice be connected with the soluble P2Os in sugar.

Dr. Matic: This point was not discussed in our paper because we did not have separate figures for organic and inorganic phosphate.

A certain amount of Phosphate, in addition to in­organic phosphate, is present in crystal and this might influence the line of phosphate shown here, but not •to a great extent.

Page 92

*WNP*MPVSF*i

Proceedings of The South African Sugar Technologists' Association —June 1970 77

FIGURE 1

350

P205 ppm MJ

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78 Proceedings of The South African Sugar Technologists' Association —June 1970

.04

E .02

FIGURE 2

.50 O FX

(B)

.40

.30

S .20

OUK OJB

OEM

OGH

O D L

O A K

OTS

.05 O F X

(A)

.03

u

O U K O I L

OJB O D L

OGH

.01 O E M

OTS O AK

30 40 50

Filterability, affinated sugar

-ii1

Page 94

Hivjnnatviii muw »t i wmiMKi niMuwiM!*

Proceedings of The South African Sugar Technologists' Association — y«ne 1970

FIGURE 3 700

600

.50

.20

•10Jr-

.05

° .04 -

.03 -

.02 -

OUK

OAK

-UK

OAK

.05

OGH

OGH

J L

OTS

ODL

OTS

OEM

(C)

O FX

(B)

J L

OFX

(A)

.06 .07

% cond, ash, affinated sugar

.09

79

Page 95

80 Proceedings of The South African Sugar Technologists'1 Association —June 1970

FIGURE 4

• HOT LIMING •COLD LIMING

O > D

^

o 00

o CM ** ° — «.

10 15 20 25 30

TIMEMIN.-

JA

Page 96

Proceedings of The South African Sugar Technologists' Association — June 1970 81

COMPOSITION OF SOUTH AFRICAN FINAL MOLASSES

By A. W. MACGILLIVRAY and M. MATIC

Sugar Milling Research Institute

Abstract A survey has been carried out on the com­

position of final molasses from South African sugar factories. Regional and seasonal trends in various parameters have been noted, and the degree of exhaustion of the molasses has been commented upon. Included in the survey are data on the non-sucrose constituents of molasses, and the inorganic ash components. Comparisons are made with a similar survey conducted in 1955/1956.

Introduction A detailed survey of the composition of South

African final molasses was carried out 15 years ago3. Since then three new factories have been opened in order to serve newly developed areas, the combined crushing rate of the mills has more than doubled and the average crushing rate has increased by 70%. Purity of mixed juice has dropped by about two points and the varietal scene has altered significantly (Co.331 and N.Co.310 varieties represented 80% of the cane crushed during 1955/56 season compared to 20% during the 1969/70 season). The methods of clarification have also changed. In 1955, defecation was practised by eight out of 17 factories. There was one carbonatation factory and the remaining mills used sulphitation. Profound changes, which could have influenced the composition of final molasses, have therefore taken place in the industry in the inter­vening years and it was felt that a new survey of the final molasses was highly desirable.

In order to assess the seasonal influences on the molasses composition, it was intended to collect four samples of final molasses from each factory, i.e. at the beginning of July, September, November and January. Ten mills supplied all four samples. Three samples were received from seven factories, either because they stopped crushing before January or for some other reason. RN sent two and PG one sample. ME, which produced high test molasses, was omitted from this survey.

Except for EN, where sulphitation is used, all other factories clarified their juice by either normal defecation or vacuum flotation (SZ, UK). However, ML, GH, SZ and PG are factories-cum-refineries. The first three use carbonatation with polishing sulphitation in their refining process and PG uses melt carbonatation only.

The analytical results obtained in the survey are presented in this paper and seasonal and regional influences on molasses and ash composition are dis­cussed. Target purities are calculated by using the Douwes Dekker, Queensland and Mauritian formu­lae and are compared with the final molasses purities actually achieved.

Experimental The molasses samples which were analysed were

composite samples from each factory for the first week of July, September, November and January respectively. The analyses for sucrose, reducing sugars, ash, dry solids, colour and viscosity were done as soon as possible after receipt of the samples to avoid any effects of deterioration. Analyses of the ash constituents and the organic non-sugars were completed at the end of the season when all the samples were available.

The methods of analysis were as follows:

(a) Dry Solids The method is detailed in the Laboratory Manual

for South African Sugar Factories (1962) pages 67-8.

(b) Refractometer Solids The solids were determined on undiluted molasses

at 20 °C using an Atago Refractometer.

(c) Sucrose This determination was by Lane and Eynon titra­

tion after acid hydrolysis7.

(d) Reducing Sugars By Lane and Eynon titration7.

(e) Sulphated Ash As described in the Laboratory Manual for South

African Sugar Factories (1962), page 56.

(f) Colour An approximately 50 Brix refined sugar solution

was decolourised with 1% (on solids) of active car­bon. The solution was filtered over kieselguhr (0.7% on solids) on a Buchner funnel, and the pH was adjusted to 7.0 ± 0.1 with dilute HC1 or NaOH. The Brix was then adjusted to 50.0° ± 0 . 1 . One gramme of molasses and 99.0 g of the sugar solu­tion were mixed to obtain a homogeneous solution. The colour was then determined by ICUMSA Method IP as is used for raw sugars. The colour attenuation was corrected for dry solids by multiply­ing the result by -j y-r, in order to eliminate the

effects of the varying water contents of the molasses.

(g) Viscosity The samples were adjusted to 80.0% dry solids by

adding the calculated weight of water to a known weight of molasses and viscosity was determined with a Hoppler Falling Ball Viscometer, at 25° and 50°C

Page 97

82 Proceedings of The South African Sugar Technologists Association — June 1970

(h) Filierability Two per cent by weight of molasses was added to

a 60° Brix refined sugar solution, and the filter-abilities were determined by the Nicholson and Horsley method8. The filterabilities obtained were then expressed as a percentage of the figure obtained for the refined sugar solution, which was determined as a blank.

(i) Starch, Wax and Gums These were determined as described by Douwes

Dekker'.

(j) Aconitic Acid Thirty-five grammes of molasses were dissolved in

250 ml water, and 50 ml of neutral lead acetate were added. The precipitate was washed free of wax and fats, and dried. Decarboxylation was carried out by boiling the precipitate with glacial acetic acid in the presence of potassium acetate. The C0 2 given off was collected and the amount determined, from Which the aconitic acid was calculated.

(k) CaO, MgO and K20 These were determined as described by Douwes

spectroscopy10.

(1) Chloride This was determined by automatic potentio-

metric titration as described by Comrie2.

(m) Sulphate This was determined gravimetrically by precipita­

tion with BaCl2.

(n) Protein Nitrogen was determined by the micro-Kjeldahl

method.

(o) Silica As described by Vogel11.

Results and Discussion The analytical data are presented in Tables I, II

and IV.

Dry Solids and Refractometer Solids Refractometer solids in Table I have been deter­

mined on undiluted molasses samples. It was felt that the error which is obtained by this method is of a similar order to that when samples are diluted and filtered prior to reading. The average difference between refractometer solids and dry solids found for these samples was 2.78%, with a standard deviation between results of 0.82. A limited number of deter­minations carried out at the S.M.R.I. on various dilutions of molasses give differences ranging from 3 to 6.

The dry solids of the samples analysed varied between 76.89 and 84.79 with an average figure of 81.53. This is 2.18% higher than the average found in the previous survey3 of Natal final molasses. This may be due either to the improvement which has been made in centrifugal performance in the last 15 years or to lower viscosities of final molasses. Unfortunately no comparative figures are available.

Pol and Sucrose A number of the samples analysed were found to

have a pol value lower than the chemically deter­mined sucrose. In all but one of these cases the samples were taken during November, when the re­ducing sugars were generally low. Conversely the greatest differences between sucrose and pol were found in samples having a high reducing sugars con­tent. The effect of this phenomenon on the apparent and gravity purities is obvious and some of the anomalous results which have been found in the past by the factories may have been due to this discrepancy.

Colour It has been noted in the past that low pol sugars

produced at certain factories were very much higher in colour than at others. As this was largely due to the colour of the final molasses coating, it was thought to be of some interest to present compara­tive data for molasses colours. It is apparent from Figure 1 that the molasses colours were at a mini­mum during September, when mixed juice purities were highest. During November and January colours were substantially higher. One exception to this was JB, where no seasonal influence was observed. Dis­regarding EM and DL, both of whom produced very highly-coloured molasses, there appeared to be a regional influence, as molasses produced on the South Coast and in the Midlands were higher in colour than those from Zululand and the North Coast.

Surprisingly, there appears to be no correlation between the nitrogen content of molasses and the colour.

Viscosity It has been observed by a number of workers1 •5-9

that the limiting factor in molasses exhaustion is viscosity. In order to determine any seasonal or regional influences on the viscosities of Natal final molasses, the viscosities were determined at a fixed dry solids content of 80%. In most cases the viscosity of molasses from any one mill tended to reach a maximum during November. A very wide spread in viscosities between factories was observed, with figures ranging from 14 to 128 poises at 50°C and 93 to 855 poises at 25 °C.

Filterability It was felt that an indication of the suspended

matter in molasses could be obtained from a filter-ability measurement. A method was devised which approximated to the conditions of the Nicholson and Horsley filterability test8, and comparative figures were obtained for the September and January samples. A marked seasonal influence was observed, with a drop in filterability occurring towards the end of the season. This is in agreement with the trend found in the results of filterability tests of unaffinated low pol raw sugars in South Africa.

Exhaustion of Final Molasses As was mentioned earlier, the main limiting fac­

tor in molasses exhaustion is the viscosity. This has been borne out by this survey, in which it was found

Page 98

— June 1970 83 Proceedings of The South African Sugar Technologists' Association

0.65 f

0.55

that in most cases the highest molasses purities occurred in November, when the highest viscosities were recorded.

A number of formulae for the exhaustibility of final molasses are based on the ratio of reducing sugars to ash. Of the molasses samples analysed in this survey, almost all had the lowest reducing sugars/ash ratio in November, and a definite correla­tion is apparent with the degree of exhaustion. The data produced in this survey were applied to three different molasses exhaustion formulae, viz. the Douwes Dekker formula4: P = 35.886 - 0.08088 R + 0.26047A; the Queensland formula1 : P = 40.67 -17.80 log X; and the Mauritian formula9: P = 44.6O - 4X, where P = target purity, R = RS% non-sucrose, A = ash % non-sucrose, and X = RS/ ash.

In general the best agreement between the actual true purity and the target purity was obtained with the Douwes Dekker formula. However, in cases where particularly low reducing sugar/ash ratios were found, such as at EN and the South Coast mills, the Queensland formula provided better agreement. The formula originally derived from experimental data in Mauritius was as indicated above. However, it was found that a number of factories were con­sistently improving on the target, and hence it was decided to arbitrarily reduce the constant factor by three. Despite the fact that the equation was used in its original form when applying it to the results of this survey, the differences between true and tar­get purities were greater in most cases than with the

July Sept. Nov. Jan.

other two formulae. This would seem to indicate that by Mauritian standards Natal final molasses is poorly exhausted, but as yet no direct comparison between viscosities have been made.

Composition of Dry Solids The composition of the molasses samples, on a dry

solids basis, are shown in Table II. There was a definite seasonal influence upon the

reducing sugars content as a percentage of the solids (Figure 2). November samples were the lowest in every case, whilst in general the January samples were the highest. The opposite seemed to be the case with the sulphated ash percentage dry solids (Figure 3), where January was the lowest and November the highest.

On a regional basis the lower South Coast mills of RN, SZ and UK were low in reducing sugars, as was noted in the previous section. EN was also very low in reducing sugars. An explanation for this may possibly be found in the relatively high pH's which are used in the Rabe process at SZ and UK, and which are also found in the sulphitation process used at EN.

Three factories which were conspicuous for their low ash per cent dry solids figures were ML, JB and UC. All three of these mills service newly developed cane-growing areas, some distance inland. The low ash content is probably not due to the type of cane grown in these areas as there is a con­siderable difference between the varieties found in the Eastern Transvaal and in the Midlands.

i i

-±- ' ' • 1 1 • 1 1 1 1 - J 1 I I i i I 1 _ PG ML UF EM FX EN AK DL DK GH GD MV TS JB UC IL RN SZ UK

FIGURE 1: Seasonal variation of molasses colour.

Page 99

84 Proceedings of The South African Sugar Technologists' Association — June 1970

20.0

16.0

10.0 PG ML UF EM FX EN AK DL DK GH GD MV TS JB UC

FIGURE 2: Seasonal variation of reducing sugar content of molasses.

IL RN SZ UK

22.5

20.0

July

. Sept.

Nov. Jan.

12.5 PG ML UF EM FX EN AK DL DK GH GD MV TS JB UC

FIGURE 3: Seasonal distribution of ash content of molasses. RN SZ UK

>k • %

Page 100

Proceedings of The South African Sugar Technologists' Association — June 1970 85

Seasonal influences in the gum content (Figure 4) are also apparent, with November again having the highest figures, and January the lowest. There seemed to be a slight increase in wax content from September to January while the protein content declined slightly over the same period. No seasonal differences could be detected in the aconitic acid contents.

Table III shows the comparison between the average non-sucrose constituents of the molasses produced in July/September 1955 and September/ January 1969/70. The carbonated ash shown for 1969 has been calculated from the relationship:—

Carbonated ash=sulphated ash x 0.752. This is an aoproximation based on the figures presented by Douwes Dekker'1.

TABLE m Average composition of the "Non-Sucrose" of Final Molasses

Total non-sucrose % molasses Reducing sugars % N-S Carbonated ash % N-S Starch % N-S Gums % N-S Wax % N-S Crude protein % N-S U.O.M. % N-S

1969/70 45.95 33.80 24.27 ' 0.34 5.86 1.10

11.88 22.75

1955/6 42.75 30.50 26.75

1.04 7.43 0.94 7.13

27.30

It would seem from Table III that the reducing sugars are higher and the ash lower now than was the

case 15 years ago. This is reflected in the true purities of final molasses which were on the average 46.2 in 1955 and 44.7 in 1969/70 seasons.

As was to be expected, owing to the introduction of starch-removal processes, the starch and total gums are lower than in 1955. The sum of the protein and undetermined organic matter is very similar in both surveys and the difference in protein figures is not thought to be significant. Wax content is of very much the same order in both cases.

Composition of the Inorganic Ash of Molasses The composition of the ash of the final molasses

samples analysed is shown in Table IV. Potassium represents roughly one-third of the ash

in most cases. Magnesium is a major constituent, but in contrast to the figures reported in 1955, in no case was the magnesium content higher than that of the calcium. JB, and to a lesser extent UC, are low in magnesium while EN, JB and UK are rather higher than average in calcium.

An interesting feature of Figure 5, where average results for various constituents are plotted, is the relationship between potassium and chloride on the one hand and calcium and sulphate on the other. Very little regional or seasonal trend in inorganic constituents is apparent.

The molasses samples from EN were somewhat different from the rest of the factories in their ash composition, particularly with respect to potassium, chloride, calcium and sulphate. This was no doubt due to the sulphitation process still practised in this factory.

FX EN AK DL DK GH GD MV TS JB UC

FIGURE 4: Seasonal distribution of gums content of molasses.

Page 101

86 Proceedings of The South African Sugar Technologists' Association — June 1970

20.0

10.0

K,0

. * - „ • MgO

EN AK OL DK GH GD MV TS

FIGURE 5: Distribution of ash constituents.

Acknowledgements The authors wish to thank Mr. R. A. Wood of

the S.A.S.A. Experiment Station, Mount Edgecombe, for nitrogen analysis, and the personnel of all fac­tories for their co-operation in collecting molasses samples. The analyses were carried out by the Sugar Milling Research Institute's Analytical Laboratory staff and their help is gratefully acknowledged.

References Anon., 1960. A Final Molasses Exhaustion Formula. Sugar Research Institute Tech. Rep. 64, 1960. Comrie, G. W., 1969. Potentiometric Determination of Chlorides in Molasses. Proc. S. Afr. Sug. Technol. Ass. 43 (1969), 151-5. Douwes Dekker, K., 1957. The Composition of South African Final Molasses. Proc. S. Afr. Sug. Technol. Ass., 31 (1957), 92-107. Douwes Dekker, K., 1949. Some Remarks on the Exhaustibility of Final Molasses, on the Winter Ratio and on the Colour of White Sugar. Proc. S. Afr. Sug. Technol. Ass., 23 (1949), 40-3. Graham, W. S., 1966. Some Notes on Natal C Mas-secuites and C Molasses. S.M.R.I. Quat. Bull. No. 30 (1966), 101-7. I.C.U.M.S.A. Proc. of 14th Session, 1966, 129. Laboratory Manual for South African Sugar Factories. S. Afr. Sug. Technol. Ass. (1962), pp. 51, 52, 56, 67.

8. Nicholson. J. I., and Horsley, M., 1956. The Design and Performance of a New Test Filter. Proc. of 9th Con­gress, I.S.S.C.T. 2 (1956), 271-287.

9. de Saint Antoine, J. D. de R., and Vignes, E. C, 1968. Further Notes on the Exhaustibility of Final Molasses.

Mauritius Sug. Ind. Research Inst. Annual Report (1968), 129-33.

10. S.M.R.I. unpublished results. 11. Vogel, A. I., 1961. A Textbook of Quantitative

Inorganic Analysis. Longmans, 3rd Ed. (1961), 580-1.

Discussion Mr. Jennings: When viscosity was measured, was

any allowance made for air and the presence of grain? I notice that reference No. 10 is to an unpublished

report by the S.M.R.I. and I hope that this will soon be made available.

In Table IV we start with sulphated ash percentage solids in molasses and then there are a number of constituents which add up to about 75% of the ash. Where is the other 25%?

I would like to hear Mr. Hoekstra's opinion of the Douwes Dekker formula.

Mr. MacGillivray: When measuring viscosity, the samples were not re-aerated and grain was not taken into account.

De-aeration is very difficult to carry out success­fully and I am not sure that the viscosities obtained on de-aerated samples are any more significant. At the time we did these tests we were particularly in­terested in how the molasses from different mills would handle at the Terminal, and in this context viscosity is a function of the degree of aeration to quite a marked degree. I think there is a valid point about grain.

We warmed the samples and added the applicable

Page 102

Mill

PG

ML

UF

EM

FX

EN

AK

DL

DK

G H

O D

MV

TS

JB

UC

IL

RN

SZ

UK

AVE

Month

NOV

JULY SEPT NOV

JULY SEPT NOV JAN

JULY SEPT NOV JAN

JULY SEPT NOV JAN

JULY SEPT NOV JAN

JULY SEPT NOV JAN

SEPT NOV JAN

JULY SEPT NOV JAN

SEPT NOV JAN

JULY SEPT NOV JAN

JULY SEPT NOV JAN

JULY SEPT NOV JAN

JULY SEPT NOV

JULY SEPT NOV

JULY SEPT NOV JAN

JULY NOV

JULY SEPT NOV

JULY NOV JAN

RAGE

Dry solids % 81.62

79.45 80-36 79.80

82 67 82 88 8! 48 82 28

84 00 83 37 81 19 83 03

82 56 84 (4 83 15 84-71

78 08 78 89 78 94

83 58 84 42 83 38 84 79

80 64 79 14 79.31

81 20 82 32 82 35 83.19

77.49 81.29 81.96

81 83 83.23 83 67 82 36

81.90 82 88 83 S3 81.78

79.94 82 32 78 97 80.35

79 98 80.36 82.36

84 14 83.30 83 21

81 06 82.11 80 12 82 30

83.16 77.72

80 85 79.52 79.66

80 64 79.32 76.89

81.53

Rcfr.

(Undilute)

84.05

81.94 83.20 81.54

85.39 84.56 84 72 85 (.8

. 86 90 85 80 84 93 86 02

86 40 85 70 86 39 87.44

81 32 8t 80 82 69 83.8!

86.62 85.20 86.90 87.08

82.86 82 34 82 59

83 37 84.30 85.54 86.34

80 00 84 12 85.09

84 05 84 06 85 74 84-70

84.78 84.06 84 09 84.84

82 37 84 20 82.14 83.09

84 25 83 60 86.94

87.99 86.10 86.94

84.90 84.80 83.52 85.69

85.56 80.94

83.62 81.56 K2 71

80 64 79 32 76.89

34.16

Pol

35.84

31.44 32-48 37.92

34 74 36.40 36.44 34 92

36 14 33.76 36 68 33 20

31 00 33 48 33 48 29 16

33.94 37 40 39.16 35 52

34 00 34.44 36 84 3! 24

33 24 36 04 31.48

33 92 32 88 35.94 32 32

33.12 40 04 33.20

32 80 33 60 34 08 28.76

31.20 33 16 34 48 31.20

30 52 31.72 35.16 32.44

30 26 32 04 31.12

33.92 34 00 35.16

30.96 32 68 32 28 29 04

35.64 38.60

36.64 35.36

32.88 34.80 30.76

33.84

Sucrose

37.50

35.66 34.72 41.90

38.34 39.46 36 53 38.62

39 09 36 42 38 65 38.72

34 62 34 44 34 08 34 45

35 81 36 96 3') 00 37 27

35 90 35 07 36 31 35.09

35.00 35.09 34.96

37.43 35.95 36 59 35.23

35.44 38.56 37.47

36 22 37.04 37.49 34 29

34 17 34 37 35 40 34.30

33.83 32.74 33.73 35.65

34.54 34 01 39.22

37.98 36.20 36.93

34.85 33.99 32.46 34.48

39.10 35.60

38.16 37.34 37.91

34.87 34.28 33.35

36 11

Red

11.61

21.10 17.26 13.04

14 72 13 28 13 11 16 87

12 38 15 34 10 77 14 70

15 23 15 59 13 79 19 88

11 43 10 38 8.03

10.86

16 20 16.61 12 04 11, 33

16 06 9 69

15.79

14 84 15 28 12 67 16 57

14 93 10 94 16.08

13 88 15.19 12.07 17.97

16.74 16.80 13.37 16.49

17.66 18.33 12.73 16 59

15 95 14 61 14.95

16.32 15.08 13.95

16.45 15.50 13 46 18.33

13.78 8.83

13.51 12 86 9.73

12.79 8.60

11-25

14 52

Sulph. Ash %

15.18

10.99 12.95 11.94

16.41 16 87 16 03 14 67

16 62 14 84 15 25 14 41

16 80 17 01 16 47 15 16

15 19 15 33 16 44 16 09

15.76 15 89 16 83 15 00

14 63 16 05 13 25

14 55 15 ?4 15 50 15 33

13 58 14 50 13.78

17 15 15 82 17 08 15.04

16 iO 15 54 16 21 15 66

15 05 14 98 15.68 14.10

1! 65 13 58 S3 80

13.30 13.30 13.52

14.42 15.12 15 67 14-33

15.61 14.91

15 05 14 84 14.85

14 14 16 38 13.16

15 04

(a 'c) 560 mn

Viscosity in poise at 8 0 % D.S.

50°C 25°C

31.6 | 74.8

32.9 46.8 46.1

36 9 31 5 35.2 33.5

li lit 4 , 8

63 0 128 3 5 1 7 56 0 5 1 7 96 5 41 6 50.9

38.6 77 8 32 8 43 6 40 4 98 4 37 9 49.1

38 0 27 6 38 2 35 0 44.3 76 0 38.7 93 4

34 7 53 3 31.7 , 24 5 38 1 86 5 39.7 58 1

39 7 35 0 50 4 60 0 46 9 40.5

33 7 ! 44.6 31 5 44 7 41 5 ' 59 0 36 8 45.1

33 9 18 2 37 5 90 5 39 2 51.4

37 3 33 I 3 1 2 i 22 9 39 7 52 3 37.4 38.7

32 5 46.6 28 0 ' 25.1 30 9 — 34.6 51.0

29.0 38 4 25 9 31 6 30 8 50 1 32.1 57.7

47 3 71 0 48 5 56 2 48 3 120.7

47.7 1 65.1 42.9 ; 55.5 42 1 71.9

42 3 49.3 41.7 55.0 39.7 i 68.5 41.3 : 52 2

47,9 44 2 43.6 | 49.4

42 2 j 51 6 . ,36 1 27.8 ' 42.4 ; 89.2

34.1 45.8 44.5

39.3

23.6 24.8 14.3

51.9

542.2

213.1 283.7 142.8

337 2 197 0

398.6

730 8 450 8 777 1 366 1

656.7 342 3 797 1 415.6

233 5 298 3 594 8 924.6

519.7 182 0 494 4 543.8

320 3 471 2 337.5

444.2 338 6 397 0 305.1

136 9 619.5 440.3

258 0 226 0 364 6 292.0

542 4 280 0

441 8

300 5 274 9 384 7 523.3

659.7 558 5 R55.8

573 2 447.1 429.5

430.2 513.1 630.3 411.7

340 1 344.5

471 3 252 1 775 5

226 4 135.9 93.7

422.5

Proceedings of The South African Sugar Technologists' Association ~- June 1970

Fi l ab

R e d . S u g a r / A . s h

R a t i o

I Target Purity \ Douwes- l Australian Mauritia ! Dekkcr j Formula Formula

True Purity - Target Purity Douwes-Dckker Australian Mauritiat

1 0 3 1 0 4 O 71

0 ' S 9

O 9 0

O 9 o 0 . 3 2 0 - 8 5

O . 9 7

44,88 43.20 52.45

46 38 47.61 44.83 46 94

41 93 40 93 40 99 40 67

45 86 46 85 49 39 46 .18

4 3 40 4 4 34 4 4 08

4 6 10 4 3 67 4 4 43 42 35

44 26 44 50 44 81 41.63

41 72 41 47 42 23 41.94

42 32 39 77 42 71 44,37

47 20

« 45 26 4 4 89 45 21

.18.53 40.22 41.30

42 84 43 53 42.82 41.51

43 30 41 48 4.1 18 41 67

42 44 42 26 42.36 40 54

4.1 39 44 97 43 58

41.39 43.60 40.79

41 80 41.95 42 47 41.42

41.43 42.65 41,03

41.43 42.37 41.67

41 29 40.77 42.64 41.10

40 87 40 97 40.97

42 51

M

35.63 38.46 40.00

41 48 42 49 42 20 39.60

43 00 40 44 43 32 40 52

41 31 42.02 38 58

40 44 40 37 43 32 39 13

39 93 44 62 39 33

40 52 40 83 42 20 40 08

39 93 42 89 39.46

40.37 40 07 42 20 40 29

39 46 39 13 42 30 39.39

39,07 .19 72 40 44

&a

36.92 39.28 40,24

41.00 41.44 41,32 40 00

41.64 411 48 4! 76 40 52

40 96 411 92 41 24 .19.36

39 92 39 72 41,36 39 88

39 92 40.32 40 28

39,68 40 1)8 40 48

40.52 41 1ft 39 48

41.00 41.12 42,00

3.54 4. OH 2 01 5,43

i 24 2,20 4.42 4 96

1.20 O 06 0 45 0.62

2 01 O 74 3 29

4 34 1.72 1.96 0.93

0.12 0,04 0.14 O 27

1 00 O 07 3.27

2 32 1.35 2 04

ft

9.25 4,74 12.45

3,47 0.28 4.75

5 58 2 84 2 22 2 22

i .39 0 03 1.65

2 86 2 86 2 94

7.96 3.92 12.21

4.90 3 20 5,84

5.53 5 53 5 80

2.90 3.74 3.05

5 46 3 38 3 90

Page 103

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Page 104

Proceedings of The South African Sugar Technologists' Association — June 19J

TABLE IV Composition of the Ash of Final Molasses?

Sulphated Ash % solids in Molasses K.O % Ash CaO % Ash MgO % Ash R 2 O s % Ash SiO, % Ash SOT %Ash CI" % Ash P , 0 5 % Ash

Sulphated Ash % solids in Molasses K t O % Ash CaO % Ash MgO % Ash RjO s % Ash SiOs % Ash S O ? %Ash CI" % Ash P s 0 5 % Ash

lSh

Sulphated Ash % solids in Molasses K.O % Ash CaO % Ash MgO % Ash R . O , % Ash SiO, % Ash SO=f % Ash CI" % Ash P , 0 6 % Ash

Sulphated Ash % solids in Molasses K.O % Ash CaO % Ash MgO %Ash R s O , % Ash SiO, % Ash SO1? %Ash CI" % Ash P , 0 5 % Ash

ML

JULY

13.83 30.66 8.10 6.43

11.93

SEPT

16.11 27.44

9.25 6.21 1.74 1.97

16.45 11.81

1.43

NOV

14.96 23.86 12.63 5.95

10.67

JAN

—

AK

JULY

18.86 31.07 7.90 7.42

16.42

SEPT

18.82 29.54

8.29 6.69 0.21 1.54

13.07 16.52

1.15

NOV

20.18 29.38

7.93 6.84

15.21

JAN

17.69 28.66 10.29 6.67 0.68 2.54

14.98 14.63 1.19

MV

JULY

19.66 26.09

9.31 7.63

15.06

SEPT

18.75

NOV

19.34 28.34

8.01 6.72

15.96

JAN

19.15 25.54 9.14 7.36 0.99 2.51

14.83 15.55 0.98

R N

JULY

18.77 30.47

8.95 7.46

15.37

SEPT

—

NOV

19.18 20.12 10.37

7,25

16.01

JAN

—

U P

JULY

19.85 28.56

7.00 7.00

17.19

SEPT

20.35 29 63

5.80 5.65 0.59

15.13 16.71 0.85

NOV

19.67 32.13 7.42 6.56

16.81

JAN

17.83 30,34 7.18 6.34 0.50 2.41

13.57 15.73 0.89

DL

JULY

—

SEPT

18.14 29.71

6.89 6.84 0.72 2.15

15.32 16.80 1.77

NOV

20.28 30.82

8.73 6.41

16.63

JAN

16.71 26.39

8.20 7.60 1.08 3.05

14.42 16.23 1.85

TS

JULY

18.83 33.08 6.69 3.19

16.72

SEPT

18.20 38.68 8.13 6.10 0.33 1,98

15.82 17.20 0.86

NOV

19.86 29.31

9.82 6.39

16.75

JAN

17.55 34.02 8.72 6.38 0.74 2.05

10.12 15.56

1.17

SZ

JULY

18.61

16.25

SEPT

18.66 26.58

8.57 7.07 0.91 1.77

16.72 16.48 0.64

NOV

18.64 31.65 7,99 7.13

16.38

JAN

—

EM

JULY

19.79 25.57

9.55 5.61

15.12

SEPT

17.80 26 97

8.48 6.40 2.02 2.92

15.84 16.03

1.65

NOV

18.78 26.89

8.73 6.23

15.41

JAN

17.36 26.67

8.81 5.99 1.32 2.59

11.52 15.10

1.61

D K

JULY

17.92 30.19 7.37 7.70

16.42

SEPT

18.87 30.58

9.22 7.47 1.01 1.59

14.57 16.52

1.15

NOV

18.82 26.46

8.61 6.80

15.21

JAN

18.43 27.40

8.84 6.56 0.70 1.79

13.94 14.63

1.19

JB

JULY

17.07 28.35 11.07

5.15

13.57

SEPT

16.90 33.85 10.06 4.17 1.77 0.71

14.67 13.01 0.37

NOV

16.76 27.50 11.63 4.71

13.69

JAN

—

UK

JULY

18.35 19.02 8.34 8.12

17.15

SEPT

—

NOV

21.45 30.82 8.90 5.87

16.88

JAN

17.84 39.13

8.95 8.00 1.62 1.85

15.02 20.32 0.92

FX

JULY

20.35 28.94

8.21 6.49

16.70

SEPT

20.22 27.30

7.37 5.19 0.35 2.08

14.98 16.88

1.30

NOV

19.81 25.44

8.13 7.17

16.38

JAN

17.90 25.36

8.99 7.09 0.61 2.15

13.52 16.06

1.34

G H

JULY

—

SEPT

17.52 29.79

8.16 6.68 0.91 2.00

15.01 16.92 0.68

NOV

17.84 29.65

8.18 6.56

16.45

JAN

16.81 27.54

9.46 6.72 0.83 2.20

18.56 15.82 0.75

UC

JULY

15.81 28.84

8.03 5.44

14.95

SEPT

15.97 32.31 9.70 6,82 1.31 1.50

15.97 15.22 0.52

NOV

16.25 31.45 9.91 4.80

14.70

JAN

—

EN

JULY

19.45 25.50 12.96

6.53

13.14

SEPT

19.43 26.09 12.76 5.87 0.51 2.11

17.76 12.52 0.57

NOV

20.83 19.73 12.82 5.47

11.96

JAN

20.0 22.0 13.7 •5.8 0.5 1.9

16.S 12.3 0.<

G D

JULY

20.96 33.40 7.16 6.49

15.69

SEPT

19.01 30.30

8.36 5.73 0.89 1.52

13.47 16.40 1.41

NOV

20.41 31.11 7.40 5.88

16.19

JA>.

18.; 30.: 9.i 6.( O.i 2,<

13.! 15.( i . :

IL

JULY

17.79 30.97 7.53 6.58

16.71

SEPT

18.41 36.01 7.60 6.14 0.98 1.30

12.17 16.51 0.47

NOV

19.56 27.76

8.84 5.62

16.49

JAh

17.' 35.: 10.< 5.! 0.1 2.:

13.: 15.< 0.1

AVERAGES

JULY

18.49 28.71

8.56 6.73

15.49

SEPT

18.32 30.32

8.55 6.22 0.95 1.79

15.13 15.70 1.00

NOV

19.01 27.91

9.22 6.31

15,46

JA>

17.! 29.:

9. ' 6.i 0.! 2.;

14. 15.. 1.

Page 105

Proceedings of The South African Sugar Technologists' Association —

amount of water to bring them to 80% solids and we hoped this would take care of grain.

Our atomic absorption data has not yet been pub­lished as we are not sure that our methods tie up with conventional methods of determination of calcium and magnesium.

Regarding the balance of the ash, the fact that the constituents were determined independently of the sulphated ash will have caused the difference in the total. If the various constituents were shown as a percentage of carbonated ash they would total ap­proximately 100%.

We were trying to show the difference in various ash levels between the samples and we also wished to show how the constituents fell in the samples from different mills.

The intention was not to do a total ash balance. Mr. Hoekstra: We are endeavouring to make a

mathematical model of a sugar factory, including the boiling house, and we thought the Douwes Dekker formula might assist in putting molasses exhaustion on a more scientific basis. Purity = A„ + A, x Reducing Sugar + A2 x Sulphated Ash

Total Non-Sucrose Total Non-Sucrose

where A„ A, and A2 are constants But Purity = Sucrose x 100

Total Solids and Total Non-Sucrose = Total Solids-Sucrose

As sucrose is by implication on the left-hand side and the right-hand side of the equation we suspected

— June 1970 87

there might be a mathematical bias in the formula. When a Douwes Dekker correlation was done by

multiple linear regression analysis on the actual re­sults of four Hulett factories, approximately 300 sets of data, we found a fair mathematical correlation — about .6.

We wondered what the correlation would be if, in­stead of actual factory data, random values of purities, reducing sugar/total non-sucrose, and sulphated ash/ total-non-sucrose were used. Yesterday, Mr. Young mentioned the Monte Carlo technique and we used this technique for generating these random values.

We determined from factory data what the means and the standard deviations were for these three vari­ables. We got the computer to generate sets of random numbers corresponding to those particular means and standard deviations.

Doing a multiple linear regression analysis on these sets of data, we got a correlation co-efficient of approximately .5, as compared with the .6 for actual data.

Therefore, although there is an improvement of .1 when using actual data, most of the correlation is due to mathematical bias inherent in the formula.

We tried reducing sugar/ash, ash/reducing sugar, and also reducing sugar/reducing sugar plus ash.

We again got a correlation of approximately .5 with random numbers but we did not get as good a correlation when using actual factory data.

So, although we have not yet found a formula that does not have an inherent mathematical bias, our conclusion is that the Douwes Dekker formula is still slightly better than the others.

Page 106

88 J'mtveilings of The South African Sugar Technologists'' Association — June 1970

FACTORS AFFECTING ENZYMATIC STARCH HYDROLYSIS IN SUGAR SOLUTIONS

By I. A. SMITH

Hulett's Research and Development

Abstract Laboratory investigation of the hydrolysis of starch

by bacterial oc -amylase in both technical and pure sucrose solutions has been carried out. The influence of reaction time, brix, viscosity, starch concentration, and enzyme dosage is represented in graphical form.

1. Enzyme Reactions The action of hydrolysing enzyme can in its

simplest form be represented by the formation of an enzyme-substrate complex

E + S **= ES

and the subsequent breakdown of this complex to yield free enzyme and the reaction products

ES E + P,. + P2

As would be expected, the rates of progress of these reactions are dependent on:

(a) Concentration of enzyme, (b) Concentration of substrate, (c) Temperature, (d) Viscosity of reacting solution.

A number of other factors also affect enzyme catalysis in general. These include:

(e) pH, (f) Cofactors (coenzymes and activators) which

enhance the reaction, (g) Enzyme poisons and inhibitors which slow

or stop the reaction, (h) Thermal inactivation of the enzyme. The

magnitude of this effect is in turn reduced by the protective action of certain sub­stances, usually including the substrate. It is known that the enzyme in question (°c amylase derived from Bacillus subtilis) is protected in this way by sucrose as well as by starch.

(i) Substrate composition. The ratio of the two constituent molecular species of starch, amy lose and amylopectin, varies according to source. Even starches from the same source have been found to display substan­tial differences in degree of polymerisation of the linear amylose fraction and in chain length of the branched amylopectin7.

2. Scope of Investigation Some effects of temperature, pH and reaction time

on enzymatic starch hydrolysis have been reported3. Subsequent work revealed the importance of the brix

factor and also the interdependence of brix and temperature. A rather more extensive programme was then initiated to assess enzyme performance quantitatively over ranges of brix and temperature likely to obtain in a sugar factory. The results of this investigation are reported here, together with some findings on the effect of independent variation in starch content and in enzyme dosage.

3. Experimental Test solutions used were mill syrup and a synthetic

refined sugar/A.R. soluble starch solution with a ratio of starch to sucrose (0.2%) comparable to that normally found in syrup.

A solution of soluble starch only was used to obtain the curve labelled 'no sucrose' in figure 1, the ratios of starch to solution and enzyme being iden­tical to those for the 7.5 brix level.

Two commercial enzyme preparations were em­ployed.

Reaction was carried out in test tubes of approxi­mately 50 ml capacity, held at constant temperature in a Colora waterbath. Transfer of the tube contents to beakers containing alcohol stopped the reaction by enzyme inactivation. This step also precipitates the remaining starch as the first step of the starch deter­mination method, based on that of Alexander1.

4. Results Note that in the work reported in sections 4.1, 4.2

and 4.3, a constant enzyme-to-solids ratio is main­tained as would be the case with equivalent-cost application in the process. Variations in brix thus entail proportional changes in concentration of enzyme, starch and any other substances that partici­pate in or affect the reaction.

4.1 Temperature and Brix Figure 1 shows the effect of temperature at various

brix levels for sucrose/starch solutions. The fall-off in activity with increasing temperature, presumably due to thermal inactivation, becomes progressively less severe as the brix rises, and has disappeared (in this temperature range) at 60 brix. Optimum hydrolysis at this point has, however, fallen well below that found at lower brix values.

In Figure 2 the same type of information, this time for syrup, is plotted as starch hydrolysis against brix for three temperature levels. Here the lowest tem­perature gives significantly inferior results except at very low brix. The 71. TC curve shows the best optimum performance. This agrees with previously published information1.

Page 107

Proceedings of The South African Sugar Technologists' Association —

Curves B and C in Figure 3 represent enzyme per­formance in sucrose/starch and in syrup solutions respectively, all other conditions being the same. Apart from a lower peak, the curve for syrup shows better performance below about 35 brix. Presumably these differences can be accounted for in terms of the factors mentioned in (d) to (i) in Section 1.

4.2 Viscosity Values for the viscosity of pure sucrose solutions2

were used to derive the plots shown in Figure 4. While the effect on viscosity of the starch present in the solutions used has not been taken into account, it is felt that for comparative purposes this method is permissible. The curves A and B do not intersect as do the corresponding plots against brix A and B in Figure 3. It thus appears that the positive slopes of the 60 and 70 brix curves in Figure 1 can be accounted for in terms of viscosity alone.

4.3 Reaction Time Figure 5 shows starch hydrolysis in syrup against

reaction time, plotted independently for the three temperature levels investigated. At 45 brix, starch hydrolised after 15 minutes is some 70% of that after 45 minutes, and at 7.5 brix this figure is even higher. It is known that where a thermal inactivation effect is present, reaction velocity falls off pro­gressively to zero. The plot for 7.5 brix at 79.4°C shows complete inactivation to have taken place below 15 minutes reaction time.

4.4 Enzyme Dosage Increasing weights of enzyme were added to solu­

tions of sucrose/starch and of syrup, each of the same composition throughout. The curves in Figure 6 show quite different profiles for the two test solu­tions. Performance in syrup is superior at lower levels of dosage, as with brix (Figure 3).

Note that the enzyme dosage axis is logarithmic, and that for example to raise the hydrolysis in syrup from 50% to 60% under these conditions would require nearly double the quantity of enzyme.

4.5 Starch/Sucrose Ratio A fixed weight of enzyme was added to sucrose/

starch solutions of the same brix but containing vary­ing quantities of starch. Figure 7 shows little change in per cent starch hydrolised. with increasing concen­tration of starch. From this it can be inferred that a roughly constant percentage as against weight of starch should be degraded in factory juices of different starch content.

5. Discussion Only a few of the factors'mentioned in Section 1

are subject to any degree of control in a sugar mill. Of these, temperature and especially brix have a pro­nounced effect on the action of commercial bacterial amylases. It appears that previous anomalous find­ings on the thermostability of these enzymes can be explained in terms of brix.

Investigation of the effect of pH has not been

— June 1970 89

included in this work. Bruijn and Jennings quote figures for starch hydrolysis at different levels of pH\ but no further references to its effect in sugar solutions have been found. It is conceivable that a relationship analogous to the brix/temperature inter­dependence may exist for pH.

Acknowledgements The author would like to thank Mr. V. Soffiantini,

who carried out some of the experimental work, and Mrs. R. Wilkes and Mr. G. Schumann, who drew the graphs.

REFERENCES 1. Alexander, J. B., 1954. 'Some notes on starch in the

sugar industry'. Proc. S. Afr. Sug. Technol. Ass., 28, 100-104.

2. Browne, C. E., and Zerban, F. W„ 1941. 'Sugar Analysis'. John Wiley & Sons, New York. pp. 510-511.

3. Bruijn, J., and Jennings, R. P., 1968. 'Enzymatic hydro­lysis of starch in cane juice'. Proc. S. Afr. Sug. Technol. Ass., 42, 45-50.

4. Ibid., p. 48, Table 4. 5. Ibid., p. 49, Table 5. 6. Dixon, M., and Webb, E. C, 1964. 'Enzymes'. Long­

mans, London, p. 63. 7. Manners, D. J., 1962. 'Enzymatic synthesis and degrada­

tion of starch and glycogen', Advances in Carbohydrate Chemistry, 17, 391.

Discussion Mr. Bruijn: Referring to Figure 6, the author says

that the initial high rate of decomposition of the starch is due to the syrup containing calcium. But do the curves cross over at a dosage of 80 mg per kilo?

The conclusion must be that, in this case, starch in the sucrose solution is not the same as starch in syrup. It appears that in industrial sugar solution part of the starch is not easily attacked by the enzyme.

In Figure 2, if the temperature is raised, the opti­mum shifts to the higher brix, probably due to a reduction in viscosity. Nevertheless, the optimum at lower concentration is higher than the efficiency at higher concentration, so lower temperatures seem to be more favourable overall.

In Figure 6, at 55 brix and an enzyme concentra­tion about the same as is used in factories, only 40% of the available starch is removed, the same as in Figure 2 at a temperature of 71 °C, where 85% is removed.

Because the viscosity is high, the only difference between a laboratory experiment and a factory ex­periment is the circulation.

Therefore, if you have a high brix solution, does circulation make a difference?

Mr. Smith: I did one test in the laboratory to test the effect of agitation. I used both a high speed stirrer with a small blade and a viforo mixer and I found no difference between these and a solution that was stirred vigorously for a few seconds and left standing. So at the brix used, which was 45, there appeared to be very little difference with stirring.

As regards stirring in the reaction vessel in a fac­tory, it may increase the rate of reaction but is it not better to design the vessel so that the juice passes through on the first in first out principle?

Page 108

90 Proceedings of The South African Sugar Technologists' Association —June 1970

As regards the theory that some portion of the starch may not be susceptible to attack, I do not feel that this is shown here. In Figure 6, the curve tails off to a level approaching about 70%, but this does not mean that 30% is not susceptible to reaction. In Figure 2, under different circumstances, we get to 80% at one point and under more favourable conditions we might get up to 100%, as we have done in laboratory work.

Dr. Matic: Figure 5 shows the percentage rather than the amount of starch that is reduced under various conditions.

Why is it that the percentage, as against the weight of starch produced, appears to stay the same?

Mr. Smith: I cannot give an explanation, although of course the concentration of the starch increases and this will tend to speed up the reaction.

Mr. Cox: Regarding Dr. Matic's query, the reaction exhibits first order kinetics; this means that the re­action has a discrete and definite half-life.

Therefore, any given quantity of reactant will be degruded by a constant percentage in unit time. When

the active sites of the enzyme have become saturated, as would occur with an excess of reactant, the re­action takes on the characteristics of a zero order reaction. In this case the quantity of material de­graded in unit time will be constant at any given temperature. The reaction velocity remains constant regardless of the amount of reactant added.

Under the conditions described, however, the re­action clearly exhibits first order characteristics, and on this basis the degradation of a constant percentage of material in unit time under isothermal conditions is in accordance with theory.

Mr. Jennings:: The enzyme usage is expressed as mg/kg brix. As we seem doubtful about the brix, I suggest we might express it as mg/kg final production of sugar.

Mr. Smith: Yes, because it could then be related to sugar lost.

For short periods, such as a day or less, it is difficult to relate juice or syrup throughput to sugar tonnage: however, for normal weekly reporting of enzyme con­sumption, a sugar basis is certainly preferable.

Page 109

^ ^ ^ • • • n m s B ^^*^^^mmmmmm tm-mmmmmtmmm

Proceedings of The South African Sugar Technologists' Association — June 1970 91

100-

9 0

8 0

7 0 -

Q LU (J) > _J O or Q > i

X o ac < t-

6 0 "

5 0 -

4 0 "

3 0

20-

10-

45 BRIX

50 60 70 80 I

90

TEMPERATURE (°C) FIGURE T: Test solution: Sucrose/starch.

Enzyme dosage: 10 mg CS-250/kg brix. Reaction time: 30 minutes.

Page 110

92' Proceedings of The South African Sugar Technologists' Association — June 1970

1C0-

90-

80-

Q LU </> 70 >

O or so-Q >-X

50-X o or < 40-

30-

2 0 -

10-

A- 79-40C

71-1 °C

62-8 °C

- 1 — 10 20 30

i * 0

FIGURE 2: Test solution: Syrup. Enzyme dosage: 10 mg Enzyme A/kg brix. Reaction time: 30 minutes.

100

50

BRIX

100-i

60 —r~ 70 lo 90 100

BRIX FIGURE 3: Test solution — curves A and B: Sucrose/starch.

Test solution — curve C: Syrup. Enzyme dosage: 10 mg Enzyme A/kg brix. Reaction time: 30 minutes. Temperature — curve A: 54.4°C. Temperature — curves B and C: 79.4°C.

i 1

1 10 VISCOSITY (CENT IP0 ISE)

FIGURE 4: Test solution:- Sucrose/starch. Enzyme dosage: 10 mg Enzyme A/kg brix. Reaction time: 30 minutes. Temperature — curve A: 54.4°C. Temperature — curve B: 79.4°C.

100

Page 111

Proceedings of The South African Sugar Technologists' Association — June 1970 93

o LLI </) 80->-_ j

o (X o > 6 0 -I

X

< h-<s>

^o 20 -

0-

A-

o .

/ /

/ / 1 /

/ / / /

' / /

62-8°C

7-5 Bmx^__-—-

. ^ - " " O

^ 4 5 BRIX

o

15 30 45

100

80

60

40

20 -

100

B- 71-1°C

- 1 — 15 30 45

R E A C T I O N T I M E ( M I N U T E S )

FIGURE 5: Test solut ion: Syrup. Enzyme dosage: 10 mg Enzyme A /kg br ix.

100

100-

1000

mg ENZYME B / kg BRIX

FIGURE 6: Brix: 45. Temperature: 80°C. Reaction time: 20 minutes.

Q UJ </> > 90 —i O £ O > I

I O a. < tn

8 0 -

7 0 -

6 0

45 MINUTES^

X

500 — I

1000

15 MINUTES 0 ~—

1

2 0 0 0 6000

mg STARCH/kg BRIX

FIGURE 7: Enzyme dosage: 10 mg Enzyme A /kg br ix. Test solutions: Sucrose/starch. Brix: 45. Temperature: 7 l . l ° C .

Page 112

Proceedings of The South African Sugar Technologists' Association — June 1970

DECOMPOSITION PRODUCTS OF ENZYMATIC STARCH HYDROLYSIS

by J. BRUIJN

Sugar Milling Research Institute

Introduction In the Rabe process, starch is mechanically re­

moved by a flotation process without leaving any residue in the juice.

The sugar industry now applies an enzymatic pro­cess to reduce the quantity of starch in raw sugar. This process is operated in such a way that the unaffinated raw sugar contains approximately 100 ppm of starch. The hydrolysis products, however, remain in the syrup and may be partly included in the crystal.

Various authors have published data on the hydro­lysis of starch by B. subtilis a-amylase '•2',1-

Robyt and French used various glucans, among others amylose and amylopectin. They added to these substrates (cone. 0.1—1%) 0.1 amylase unit * per mg of glucan.

The oligosaccharide distribution which they obtained in the digest is shown in Table 1.

TABLE I Hydrolysis with B subtilis a-Amylase

Amylose 60 min.

% 2.3

10.1 12.8 6.0

10.2 20.6 14.7 23.3

180 min % 5.3

12.3 22.0 10.5 14.8 30.1 5.1 0.0

Amylopectin 60 min

/o 1.4 5.5 8.2 0.9 4.9

14.0 9.8

55.3

180 min % 3.3 8.3

10.8 2.5 6.7

26.8 9.2

32.4

* One amylase unit as defined by French is that amount of enzyme which reduces the blue value of a 1% soluble starch solution at 40°C in one minute. At present one unit of enzyme activity (U) is that amount that will catalyse the transformation of l/imol. of substrate (or 1/u equivalent of the group attacked) per minute under optimum conditions of pH and temperature*.

Unfortunately it is rather difficult to analyse accurately for all the hydrolysis products of starch in syrup, juice or any other sugar-house product.

Experimental Enzyme Digest

No effort was made to treat amylose and amy­lopectin separately as the factory only treats the com­plete starch mixture.

The factory conditions were simulated by using a potato starch solution which was boiled for twenty minutes and autoclaved for five minutes at .3 bar.

The concentration was adjusted to 400 mg/1 and the pH to 6.5. Ten mg/1 each of sodium chloride and calcium chloride were added. Bactamyl D.200 was added in the range 5-15 mg/1 to the starch solution, which had been heated to 65°C. The hydrolysis was carried out in such a way that approximately 90-95% of the starch was decomposed.

Under these circumstances 5 mg/1 of enzyme powder gave an increase in reducing power of 0.25 mg glucose equivalent per minute.

Little increase in hydrolysis was obtained between 30 and 120 minutes. Alcohol was added to the mix­ture (1.6 times the volume) to stop the reaction and the solution was evaporated on a rotary film evaporator. Final drying was carried out in a desiccator.

Quantitative determination of Oligosaccharides The oligosaccharides were separated by paper

chromatography at room temperature using butanol: ethanol: water (2:1:1) as eluant. The quantitative determination was a modification of the method of Whistler & Hickson8.

Guide strips were developed in silver nitrate reagent.7 After the centre of the paper had been cut in between the fractions, the individual oligo­saccharides were extracted in water by digesting the papers for one hour. As it was found that filter paper fibres interfered with the determination, the extract was filtered through a .45/* millipore filter, washed and made up to a suitable volume. To an aliquot of the filtrate (normally 10 ml) 2 ml hydro­chloric acid (10 N) was added and the mixture was heated for twenty-five minutes in a boiling water bath.

After careful neutralisation using Bromo Thymol Blue (0.005%) as an indicator, the oligosaccharides were subsequently determined as glucose, according to the method of Hagedorn and Jensen1.

A chromatogram of the oligosaccharides is shown in Fig. 1—Determination of polysaccharides.

Oligosaccharides larger than G„ (maltooctaose) are not easy to separate by paper chromatography, although it is possible. Thin layer chromatography will separate to G3I1—G2,,.

Higher carbohydrate polymers are best separated by gel chromatography. This does not separate each individual sugar but separates groups of com­ponents according to their molecular weight.

The gel used was Sephadex G 50*, which separates

* Pharmacia Fine Chemicals Uppsala Sweden.

Page 113

Proceedings of The South African Sugar Technologists' Association — June 1970 95

S 2 HRS. REDUCTION 93"%,

*• 5 O O 64 MINS. REDUCTION 82% O Jjl

J S 31 MINS REDUCTION 74% -^ *.

» S» fg MINS REDUCTION 35%

» £ £ i§ 5 MINS REDUCTION 15%

0

MALTOSE

2 MINS REDUCTION 7%

FIGURE 1

polysaccharides in the range Mw 500—10,000, ex­cluding the higher Mw. The column used was 1.7 x 43 cm and 1 ml fractions were collected. The eluants used were either 0.15 M sodium chloride solution or distilled water. In these experiments no difference was observed between the two. One ml of eluant containing 1 mg of carbohydrate was placed in the column and washed into the gel with a few ml of eluant. Subsequently the reservoir with eluant was connected and the run started. The calibration of the column was carried out with Dextran T40* (Mw=40,000) Dextran T„ (Mw = 10,000) and glucose (Mw=180). The analysis of the fractions was carried out by a phenol-sulphuric acid method5.

Results and Discussion The distribution of oligosaccharides formed dur­

ing enzymatic hydrolysis is given in Table II below: TABLE n

Oligosaccharide composition of a starch hydrolysate after treat­ment with B. subtilis a-amylase Potato Starch cone: 400 mg/1

G2 G, G4 G6 G6 G, G8 >G8 Total recovered carbohydrate in %

5 ppm enzyme

% 1.8 4.8 8.8 3.2 4.5

18.5 15.0 3.3

40.1

99

10 ppm enzyme

X 4.0 7.8

10.2 4.5 7.8

21.4 11.3

25 ppm enzyme

% 8.0 8.7

10.0 3.8

12.8 26.8 4.8

»G7 32.0 > G , 26.1

97 101

This distribution of oligosaccharides compares well with those published by Robyt and French. The main oligosaccharides formed are G3, G6, G7. With higher enzyme concentrations the amount of G, (glucose) increases and G7 decreases.

The results of the gel chromatography of the starch hydrolysate are shown in Fig. 2. The calibra­tion of the column is shown in Fig. 3.

The fractions 56—90 were collected in a separate analysis and combined. After evaporation of the eluant the residue was separated by paper-chro-matography and proved to contain the oligo­saccharides G!—G7 in the same proportions as found before. The first peak, which was 30% of the total amount of carbohydrate present in the enzymatic hydrolysate has its maximum at fraction 32. The Dextran T10 shows a maximum at fraction 28. The average Mw of the polysaccharides in the enzymatic hydrolysate is for this reason < 10,000.

Conclusion The hydrolysis of starch B. subtilis a-amylase re­

sults in two groups of carbohydrates. One contains a mixture of oligosaccharides (70%) in which G3, G6 and G7 are predominant. With higher quantities of enzyme the amount of G7 decreases. The second group are polysaccharides (30%) with an average Mw < 10,000.

Summary The decomposition products in a starch hydro­

lysate obtained by B. subtilis a-amylace were in­vestigated.

The starch concentration used was 400 mg/1 and the concentration of enzyme powder (a commercial product) between 5 and 25 mg/1.

The oligosaccharides in the hydrolysate were analysed by quantitative paper chromatography. The predominant oligosaccharides were G3, G„ and G7.

The polysaccharides formed were analysed by gel chromatography using Sephadex G 50. The average Mw of these polysaccharides was found to be below 10,000 and represented approximately 30% of the total quantity of carbohydrate in the hydrolysate.

Page 114

96 Proceedings of The South African Sugar Technologists' Association — June 1970

- c 490 nM

1 -

M^ 10.0 00 '.w J L.

20 40 60 80 100 FRACTION NUMBER

FIGURE 2: Gel chromatography of a starch hydrolysate using Sephadex G50.

. E 490 nM

Mw 40,000

J I 1 L.

M w 180

20 40 60 80 100 FRACTION NUMBER

FIGURE 3: Calibration of a Sephadex G50 column with Dextran T40 and glucose.

Page 115

Proceedings of The South African Sugar Technologists' Association —

Acknowledgement Thanks are due to Mrs. M. Roberts for the ex­

perimental work.

References 1. F. J. Bates Polarimetry, Saccharimetry and the Sugars

p. 198 U.S.A. Gov. Print. Office Washington (1942). 2. J. Robyt and D. French

Arch Biochem & Biophys 100 451 (1963). 3. W. Banks e.a. Carbohydrate Research 12 79 (1970). 4. Commission on Enzymes, International Union of Bio­

chemistry 1961. Enzyme units p. 7 Pergamon Press, Oxford (1961).

5. M. Dubois e.a. Analyt. Chem. 28 350 (1956).

6. J. Osugi Rev. Phys. Chem. Jpan 5/ 957 (1958). 7. W. E. Trevelyan e.a. Nature 166 52 (1950). 8. R. L. Whistler & J. C. Hickson.

Analy. Chem. 27 1514 (1955).

Discussion Mr. Alexander (in the chair): Do any of the

oligosaccharides in the hydrolysate co-crystallise with sucrose?

Mr. Bruijn: I have not done any work on this. But a subject under investigation at the moment is to try and find out why some factories produce elongated crystals, which, according to an Australian publica­tion, are due to dextran.

We have analysed massecuites, which gave elongated crystals, for their total polysaccharide con­tent but found no difference in the total quantity compared with other massecuites.

At present I am isolating the total quantity of polysaccharides and putting them through columns to try and find any difference in molecular weight.

Mr. Comrie: Mr. Bruijn mentions that the oligo­saccharides G20 to G2S were separated by thin layer chromatography, using silica gel. We have had no success with this method.

Also, did he use streaking techniques for his paper chromatography, or only the spots as shown on the slides?

I must congratulate him on Table II, where his total carbohydrate recovery was near 100%.

Mr. Bruijn: I did carry out thin layer chromato­graphy, but not very successfully, hence I used paper chromatography.

Dr. Murray: I would like to know more about the kinetics of starch hydrolysis. The kinetics shown by Mr. Smith appear to be zero order under his experi­mental conditions.

— June 1970 97

However, the kinetics shown by Mr. Bruijn's ex­periments under factory conditions are not of zero order. Now in a normal chemical reaction, if the order changes then the products of the reaction may change and, of course, if the products change this means that the subsequent chemical and physical behaviour of the system will change. If then one produces different products by changing hydrolysis conditions then might this not have an effect on the crystallisation of sucrose and impurities intercalated at a later stage?

Does the mechanism of starch hydrolysis vary with reaction conditions?

Mr. Bruijn: A lot has been published about the mechanism of the amylase attack on starch but I would have to study this to answer your question.

Mr. Cox: Starch hydrolysis has the characteristics of a first order reaction. One of the characteristics of this type of reaction is that it has a fixed and definite half life; therefore the percentage of starch hydrolysed in mixtures will remain constant, since until the point is reached at which all the actual sites on the enzyme are saturated, the speed of reaction will increase in proportion to the concentration of starch present. When all the active sites are saturated the kinetics change to zero order. This does not entail however that the molecularity of the reaction has changed, only that the availability of active sites. which under constant enzyme concentration will re­main constant, has become the limiting factor. Under these conditions the mechanism of the reaction should remain exactly the same as when there still remained some active sites available, that is, as when the kinetics were still of the first order.

Dr. Matic: Over ninety percent of the original material was hydrolysed as determined by the starch-iodine colour determination. However, thirty percent of the hydrolysate according to gel-chromatography had an average molecular weight of 10.000 and there­fore it would be expected to give blue colour. These two results seem to be contradictory.

Mr. Bruijn: It has been published that malto oligosaccharides with a molecular weight greater than 10 give a coloured iodine complex.

There seems to be a discrepancy in the results. It is however likely that the malto oligosaccharide has to be unbranched to give this colour. In the hydrolysate obtained most of the larger oligo­saccharides obtained will be branched.

Page 116

98 Proceedings of The South African Sugar Technologists' Association — June 1970

THE ISOLATION AND PARTIAL CHARACTERISATION OF OLIGOSACCHARIDES IN REFINERY MOLASSES

By P. G. MOREL DU BOIL, K. J. SCHAFFLER, G. W. COMRIE and D. M. OOSTHUIZEN

Huletfs Research and Development

Abstract Two trisaccharides have been isolated by carbon

chromatography from cane refinery molasses. Raf-finose was detected and characterised by hydrolysis. The other carbohydrate yielded, on hydrolysis, fruc­tose and glucose in the ratio of 2:1, indicating a fructosylsucrose. Concentrations of each trisaccha-ride were approx. 0.5% by weight.

Introduction The determination of sucrose in molasses is of

prime importance to the efficient running of a sugar­cane factory. When the conventional methods for sucrose determination were drawn up, the influence of impurities such as raffinose, kestoses and poly­saccharides was not fully realised.

The application of the invertase method in beet molasses was questionable because of the presence of raffinose, kestose and levan39. These compounds are all hydrolysed to monosaccharides and thus a falsely high sucrose value is obtained. The polarisa­tion methods for the determination of sucrose are also suspect because of oligosaccharide interfer­ence39- 10. De Whalley13 has noted that a raw sugar shows an elevation of pol of 0.4 for every 1 % kestose present. Clerget molasses, however, shows an in­crease in sucrose content of 0.8 for the same concentration of kestose present.

Sutherland", along with Leonard and Richards30, identified polysaccharides as being the major cause of crystal elongation. On the other hand, however, Japanese workers 28, concerned about the refining quality of raw sugars, have considered the effects of starch, silica, phosphate, gum and oligosaccharide impurities on the formation of needle-shaped crys­tals in raw sugars. They concluded that oligosaccha­rides are a dominant factor and gums a secondary factor in the formation of elongated crystals. Exten­sive studies into the kinetics of sucrose crystal growth have been carried out by Smythe36-37-38. Oligosaccha­rides have been found to poison the growing sucrose crystal by adsorption. The most effective inhibitors of sucrose crystal growth appear to be those oligo­saccharides derived from sucrose by substitution on the primary hydroxyl group attached to C8 of glu­cose. Therefore raffinose and neo-kestose (II) are reported to be much more powerful inhibitors than 1-kestose (III) and 6-kestose (IV).

These oligosaccharides have the same sucrose moiety and their occurrence is due to transglyco-

sylation. Kestoses are fructosylsucroses which have been formed by the enzymatic transfer of a fructose radical to one of three primary hydroxyl groups of sucrose by the action of invertase17. The formation of these fructosylsucroses has been observed with invertase from a wide variety of sources—fungal, bacterial and plant extracts1'3'*-5-7'22-25. Methods of preparation of these kestoses have been outlined by Gross21. One of these methods was modified slighdy and used to prepare 6-kestose in our laboratories.

Raffinose, although occurring mainly in beet sugar factories, has been reported in cane sugar products. Gross23 detected raffinose in raw sugar produced from cane. Binkley9 later verified this by isolating raffinose and crystalline 1- and 6-kestoses from cane final molasses.

It was decided therefore to study the occurrence of oligosaccharides in South African sugar factories. Refinery molasses was chosen as the initial starting material.

Several chromatographic media have been used for the separation of sugars. Ion exchange32 and more recently, dextran18 and polyacrylamide gels27-34 have been used in the separation of carbohydrates.

Carbon was first proposed as a chromatographic medium for the separation of carbohydrates in 194141. Six years later the separation of a mixture of glucose, sucrose and raffinose was reported using carbon as the stationary phase and a 4% aqueous phenol solution as eluant11. Whistler and Durso43

extended the technique of Tiselius and in 1950 re­ported the use of aqueous ethanol as an eluting agent for sugars from a carbon-celite column. Small vari­ations of eluant composition, degree of dilution of sugars and the presence of inorganic salts did not affect the separation.

The method of Whistler and Durso43 was adopted and proved successful in the isolation of two tri­saccharides from refinery molasses.

Experimental All concentrations were carried out at 40 °C under

reduced pressure.

Paper Chromatography Paper chromatography was carried out using the

continuous descending technique on Whatman No. 1 paper, or (for preparative work) Whatman No. 3MM. The following solvent systems were used.

Page 117

^^^^^^^^•[^^•••IWllWMWMIllWMlMMWIIWlWMllMUItaillllllJflillllllJIIlLIIIIIIIIIII

Proceedings of The South African Sugar Technologists' Association — June 1970 99

CHoOH

I. Sucrose

CH2OH

HOCH

CH2OH

CH20H

HOCH, / 0

CH20H

CH2OH

II Neo-kestose III l-kestose

CH2OH

CH2OH

IV 6-kestose

Page 118

100 Proceedings of The South African"Sugar Technologists' Association —June 1970

A:41 Butan-l-ol: Ethanol : water (2:1:1 by volume) B:2 Propan-1-ol: Ethylacetate : water

(7:1:2 by volume) C:2"' Propan-2-ol: Butan-2-one : Formdimethylamide

: water (10:5:1:4 by volume) D:'" Butan-l-ol: Ethanol : water (4:1:5 by volume)

upper phase.

Drying after solvent development was achieved at 100°C except in preparative work where drying was by a cold air draught.

Aniline-diphenylamine6 was used as the detecting reagent.

Thin Layer Chromatography Thin layer chromatography was performed on

20 x 20 cm plates using Silica Gel G (Merck, ace. to Stahl). The Silica Gel was slurried with water (unless otherwise stated), spread to a thickness of 0.35 mm, air-dried for 10 minutes and finally activated at 100°C for one hour.

The following solvent systems were used:

E: Ethylacetate : Acetic Acid : water (6:3:2 by volume)

F: '2 Chloroform : Acetic Acid : water (6:7:1 by volume)

Drying after solvent development was achieved at 100°C except where otherwise stated.

Aniline-diphenylamine6 was used as the detecting reagent.

Characterisation of Carbon-Celite Column The arnylose sample was prepared by fractionation

of potato starch according to the method of Gilbert19. Approximately 8 g of potato starch (B.D.H.) was used to give 0.6 g of arnylose in the form of the stable butanol-amylose complex.

The arnylose was partially hydrolysed using sul­phuric acid42. The Somogyi-Nelson26-31 micro-method for reducing sugars was used to follow the course of the hydrolysis. The reaction was stopped after 32.5% apparent conversion to glucose. Kuhn's29

formula indicates that an optimum yield of dextrins containing from 3 to 8 glucose units would be present at this stage. The solution was de-ionised (Amber-lite M.B.-l) and concentrated to 5 ml.

50 g of a carbon (B.D.H. acid washed) - celite (Hyflo Supercel) mixture (1:1) was slurried with water and packed into a column (350 x 25 mm). The column was compacted by passing through 500 ml of water at 3.0 ml/min. The hydrolysate (2 ml) was applied to the column and eluted with water at a flow rate of 1.5 ml/min. The eluant was collected in 15 ml fractions and monitored with an throne1". A large carbohydrate peak was detected. After com­plete removal of this peak 5% EtOH was pumped through the column and the eluant again monitored with anthrone. The elution procedure was repeated stepwise to a final concentration of 30% EtOH.

The fractions containing the individual peaks were concentrated and spotted on Whatman No. 1 paper.

The chromatogram was developed using Solvent A. After development (72 hours) the paper was dried, sprayed and the respective rg values determined (Table II). Separation up to D.P. 10 with 30% EtOH confirmed that the entire oligosaccharide range had been covered.

TABLE II R „/ lcose values of fractionated arnylose hydrolysate

on Whatman No. 1 using solvent A

Fraction ^glucose ^glucose of Hydrolysate

H„0 1.00 1.00 5% EtOH 0.65 0.67 10% EtOH 0.42 0.40 15% EtOH 0.25 0.26 20% EtOH 0.17 0.18

0.10 0.09 25% EtOH 0.07 0.05

0.03 0.03 30% EtOH 0.02 unresolved

Isolation of the Oligosaccharides from Refinery Molasses

Initial Separation A column (500 x 40 mm) was packed with a slurry

of 270 g of a carbon (BDH acid washed) -celite (Hyflo Supercel) mixture (1:1) in water. The column was allowed to settle and compacted by pumping through 500 ml of 5% EtOH at a flow rate of 3.0 ml/min. Refinery molasses (5 g) was taken up in 20 ml of 5% EtOH, applied to the column, which was developed with 5% EtOH (2.0 ml/min.). The eluant was monitored with anthrone16 and the frac­tion 840-3 000 ml on analysis by paper and T.L.C. showed the presence of glucose, fructose and sucrose only. A portion of this fraction was concentrated, hydrolysed with invertase and re-chromatographed. No disaccharides were detected.

The developing solvent was changed to 10% EtOH and collected in 15 ml fractions. The tri-saccharide fraction was detected after 860 ml and was completely removed by 1260 ml. Analysis showed two peaks incompletely separated. The frac­tions containing the trisaccharides were concentrated to 10 ml.

Purification of the 10% Fraction The concentrated trisaccharides were re-chromato­

graphed on a smaller column (350 x 25 mm) using 50 g of carbon-celite. The column was packed as in the arnylose calibration. Sucrose was eluted with 5% EtOH and the trisaccharides were eluted with 10% EtOH at 1.5 ml/min. Two peaks, incompletely separated, were evident after analysis with anthrone (Fig. 1).

Semi-quantitative analysis with anthrone indicated 26 mg and 36 mg carbohydrate (as raffinose) in each peak (A and B respectively). The fractions contain­ing the peaks were concentrated separately and analysed by paper chromatography (Solvent A).

Page 119

Proceedings of The South African Sugar Technologists' Association — June 1970 101

Rechromatogram of 10% EtOH

Fraction

3.0 |—

0.0 •"—Vs"

Elution Volume (ml)

FIGURE 1

The concentrates from peaks A and B were applied to Whatman 3MM paper and developed with Sol­vent A for* 48 hours. The papers were dried in a stream of cold air and indicator strips on either side of the paper sprayed. The sections corresponding to the desired carbohydrate spots (i.e. pure peak A or B) were cut from the unsprayed portion of the paper and the sugars eluted with water using the method of DimlerM. Elution was continued for two to three hours in a humidified cabinet during which time 8 to 12 drops of eluant containing all the carbohydrate was collected.

Hydrolysis Partial acid hydrolyses were conducted with

0.005N H2S04 for one hour at 60°C. Complete hydrolysis was effected with 0.05N H2S04 for two hours at 100°C. Enzymatic hydrolysis was carried out by incubation for two hours at 60°C with inver-tase (10 mg Convertit/ml).

All hydrolyses were carried out using the ultra-microtechnique of Porter". Using this method from 0.01 to 6.05 ml of sample containing about 20 to 50 /Ag of sugar was hydrolysed in sealed tubes approximately 100 x 2 mm. Acid solutions were neu­tralised with ion-exchange resin (Amberlite MB1) prior to paper chromatography (Solvent D).

T.L.C. of the peak B hydrolysate was carried out on Silica Gel G impregnated with sodium acetate buffer12. The plates were run three times using sol­vent F. Drying was effected in a stream of cold air between each run.

Fructose/Glucose Ratio of Peak A The invert hydrolysate of pure peak A was ana­

lysed for total reducing sugars according to the Somogyi-Nelson method26-31 and for ketose using the resorcinol-HCl method15'20. A fructose/glucose ratio of 1.7 : 1 was obtained.

Preparation of 6-kestose 6-kestose was prepared by a method based on

that of Gross". 150 gm. of cellulose (Whatman CF 11) was slurried with the solvent isopropanol: butanol : water (7:1:2) and packed into a column (550 x 40 mm). After settling and compacting by pumping 300 ml of the same solvent through the column at l.Oml/min, 5 gm of the sucrose-invertase syrup21 was taken up in the solvent and applied to the column. The solvent was pumped at a flow rate of 0.64 ml/min through the column and 6.4 ml frac­tions collected. Individual fractions were analysed by T.L.C. using solvent E. Crystallisation from abso­lute methanol was effected in a dessicator contain­ing anhydrous silica gel m.p. 138-139° (lit., m.p. 144-145°).

Results and Discussion Fractionation of the amylose hydrolysate on the

carbon column yielded glucose, maltose, maltotriose and maltotetraose when eluted with water, 5% EtOH, 10% EtOH and 15% EtOH respectively. Similar analysis on a refinery molasses sample showed that no sugar was present in the 15% frac­tion and hence it was assumed that the two sugars eluted in the 10% peak were both trisaccharides. The EtOH concentration in the molasses fractiona­tion was increased stepwise as shown in Fig. 2. It can be seen that the concentration of higher sugars is small compared with that of the trisaccharide fraction. From the amylose hydrolysate calibration the entire range of D.P. 1-10 was covered by in­creasing the EtOH concentration from 0 to 30%.

Analysis of peak A yielded the following results:—

1. Paper chromatography in several solvents gave R sucrose values characteristic of 1 or neo-kestose (Table I).

2. Invertase hydrolysis yielded glucose and fruc­tose on analysis by chromatography. The linkages therefore must be of the fi -type.

3. Complete acid hydrolysis gave glucose and fructose while partial hydrolysis yielded fruc­tose, glucose, sucrose and the original sugar.

4. Determination of the fructose/glucose ratio after invert hydrolysis yielded a ratio of 1.7: 1.

On the basis of these observations peak A has been tentatively classified as a kestose. Comparison °f ^sucrose values rules out the possibility of 6-kestose. Electrophoretic analysis will show whether 1- and/or neo-kestose is present.

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102 Proceedings of The South African Sugar Technologists'1 Association — June 1970

Chromatographic Separation of Refinery Molasses on Carbon-celite column

EtOH concentration

25%

'Elution volume (ml x 103)

FIGURE 2

R sucrose

Whatman No. 1 paper

Solvent System

Sucrose ... Raffinose ... 1-Kestose ••• ... 6-Kestcse Peak A Peak B Prepared 6-Kestose

*Minor

A

l.CO 0.47 0.69 0.61 0.72 0.46 1.00* 0.67*. 0.58

spots.

B

1.00 0.46 0.68 0.58 0.72 0.48 1.00* 0.67* 0.57

C

1.00 0.50 0.78 0.69 0.78 0.49 1.00* 0.78* 0.67

Analysis of peak B gave the following results:— 1. Paper and T.L.C. gave Rsucrose values charac­

teristic of raffinose (Table I). 2. Acid hydrolysis yielded glucose, fructose and

galactose. 3. Invertase hydrolysis yielded melibiose and

fructose. On the basis of these observations, peak B has

been tenatively indentified as raffinose. Semi-quantitative analysis has shown that peaks

A and B are present in refinery molasses in the order of 0.5% by weight.

Acknowledgements The authors are indebted to Dr. W. W. Binkley

of New York Trade Laboratories, N.Y., for samples of 1- and 6-kestose and to Mr. J. Bruijn of the Sugar Milling Research Institute for his advice on carbon column chromatography.

References

1. Albon, N., Bell, D. J., Blanchard, P. H., Gross, D., and Rundell, J. T., 1953. J. Chem. Soc. 24.

2. Albon, N., and Gross, D., 1952. Analyst 77, 410. 3. Allen, P. J., and Bacon, J. S. D., 1956. Biochem. J. 63.

200. 4. Bacon, J. S. D., 1954, Biochem. J. 57, 320. 5. Bacon, J. S. D., and Bell, D. J., 1953. J. Chem. Soc.

2528. 6. Bailey, R. W., and Bourne, E. J., 1960. J. Chromatog.

4, 206. 7. Barker, S. A., Bourne, E. J., and Carrington, T. R.,

1954. J. Chem. Soc. 2125. 8. Binkley, W. W., 1964. I.S.J. 66, 46. 9. Binkley, W. W., 1964. ibid. 66, 185.

10. Carruthers, A, Dutton, J. V., Oldfield, J. F. T., Elliott, C. W., Heaney, R. K., and Teague, H. J., 1963. 16th Ann. Tech. Conf. Brit. Sug. Corp.

11. Claesson, S., 1947. Arkiv. Kemi., Mineral Geol. 24A (32), 9.

12. De Stefanis, B. A., and Ponte, J. G., Jr., 1968. J. Chromatog 34, 116.

13. De Whalley, H. C. S., 1952. I.S.J. 54, 127. 14. Dimler, R. J., Schaefer, W. C, Wise, C. S., and Rist,

C. E., 1952. Anal Chem. 24, 1411. 15. Dische, Z., 1962. Methods in Carbohydrate Chemistry,

Academic Press, New York, 1, p. 488. 16. Fairbairn, N. J., 1953. Chem. and Ind. 86. 17. Fischer, E. H., Kohtes, L., and Fellig, J., 1951. Helv.

Chim. Acta. 34, 1132. 18. Flodin, P., Gregory, J. D., and Roden, L., 1964. Anal.

Biochem. 8, 424. 19. Gilbert, L. M., Gilbert, G. A., and Spragg, S. P.,

1964. Methods in Carbohydrate Chemistry, Academic Press, New York, 4, p. 26.

20. Gray, D. J. S., 1950. Analyst 75, 314. 21. Gross, D., 1962. Methods in Carbohydrate Chemistry,

Academic Press, New York, p. 360. 22. Gross, D., Blanchard, P. H., and Bell, D. J., 1954.

J. Chem. Soc. 1727. 23. Gross, D., Gardiner, F. J., and Butters, R. W.,

1962. I.S.J. 64, 69. 24. Hammer, H., 1968. Acta. Chem. Scand. 22, 197.

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Proceedings of The South African Sugar Technologists' Association —

25. Henderson, R. W., Morton, R. K., and Rawlinson, W. A., 1959. Biochem. J. 72, 34.

26. Hodge, J. E., and Hofreiter, B. T., 1962. Methods in Carbohydrate Chemistry, Academic Press, New York, 1, p. 380.

27. John, M., Trenel, G., and Dellweg, H., 1969. J. Chromatog. 42, Aid.

28. Kamoda, M., Onda, F., Ito, H., Shirasaki, T., Miki, T., and Ando, T., 1968. Proc. of the 13th Congress of I.S.S.C.T. 362.

29. Kuhn, R., 1930. Ber. 63, 1503. 30. Leonard, G. J., and Richards, G. K, 1969. I.S.J.

71, 263. 31. Marais, J. P., De Wit, J. L., and Quicke, G. V., 1966.

Anal. Biochem. 15, 373. 32. McCready, R. M., and Goodwin, J. C. 1966. J.

Chromatog. 22, 195. 33. Partridge, S. M., 1946. Nature 158, 270. 34. Pontis, H. G., 1968. Anal. Biochem. 23, 331. 35. Porter, W. L., and Hoban, N., 1954. Anal. Chem. 26,

1847. 36. Smythe, B. M., 1967. Aust. J. Chem. 20, 1087. 37. Smythe, B. M., 1967. ibid. 20, 1097. 38. Smythe, B. M, 1967. ibid. 20, 1115. 39. Stachenko, S. (referee), 1962. I.C.U.M.S.A. Proc. 14th

Session, Copenhagen, Subject 8. 40. Sutherland, D. N., 1968. I.S.J. 70, 355. 41. Tiselius, A., 1941. Arkiv. Kemi., Mineral Geol. 14B

(32), 8. 42. Whelan, W. J., Bailey, J. M., and Roberts, P. J. P.,

1953. J. Chem. Soc. 1293. 43. Whistler, R. L., and Durso, D. F., 1950. J. Amer.

Chem. Soc. 72, 677. 44. Whistler, R. L., and Hickson, J. L., 1955. Anal. Chem.

27, 1514.

Discussion Mr. Alexander (in the chair): We do not know

where this investigation will lead us, but it may ex­plain some of the anomalies we have in the sugar industry, such as undetermined losses.

— June 1970 103

Dr. Matic: A prepared 6-kestose appears to be im­pure, as shown by the melting point and chromato­graphic behaviour. This should be borne in mind when further work is carried out.

Mr. Schaft'ler: The melting point is not as it should be because we only re-crystallised 6-kestose once, owing to lack of time before writing this paper.

Mr. Comrie: In Table I it is shown that 6-kestose contained minor spots and was not as pure as we would have liked. The main spot had an R sucrose value of .58.

Mr. Carter: Can this now be regarded as a routine analysis to be carried out by ordinary laboratory personnel?

Mr. Schaffler: The results reported in this paper are part of a research project which is being carried out to identify oligosaccharides in sugar products.

Once the oligosaccharides have been identified, a routine quantitative thin layer chromatographic method will be adopted.

Initial experiments in this aspect of the work are now in progress.

Mr. Jennings: At the recent ICUMSA meeting, kestoses and disaccharides were discussed and methods mentioned at the previous Copenhagen meet­ing were tentatively approved.

One difficulty in setting up routine methods for kestoses is to obtain standard samples. We have ob-"tained samples of 1-kestose and 6-kestose from the New York trade laboratory.

Mr. Dutton, of British Sugar Corporation, has done determinations of kestoses and raffinoses in cane molasses from all over the world. The largest amount of kestose and raffinose found in combination was .5% in cane refinery molasses.

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104 Proceedings of The South African Sugar Technologists" Association — June 1970

SOME ASPECTS OF FACTORY OPERATION AT THE TONGAAT SUGAR COMPANY FACTORY

By G. G. CARTER, W. S. GRAHAM and

B. ST. C. MOOR

The Tongaat Sugar Company Limited

A review of several of the operations carried out in a raw sugar factory has been presented. Proven solutions to some of the practical problems which were being experienced at the Tongaat Sugar Com­pany factory are described, while mention is also made of some still unresolved practical difficulties which, it is hoped, will provoke fruitful discussion.

Trials with an Ultrasonic Electrode Cleaner A commercially available ultrasonic electrode

cleaner was tried on the electrodes which measured the pH of limed juice at its boiling point. The local representatives of the supplier had stated that the ultrasonic electrode cleaner could be used satisfac­torily on boiling juices but it was only subsequent to its installation that the contrary opinion of a representative from the parent company in Europe was learned. It was explained that the electrode cleaner would prove unsatisfactory in liquids at boil­ing point because the energy imparted by the elec­trode cleaner would cause a vapour layer on the electrode surface, i.e. the liquid on the surface of the electrode was made to boil. This was borne out in practice.

The unit did show the anticipated benefit of keep­ing the electrodes clean but it also caused un­expected damage. In particular it caused the porous plug on the reference electrode to be dislodged and was the probable cause of some broken glass elec­trodes. Further, the sealing of the ultrasonic probe itself was unsuitable for the conditions of use.

The Distribution of Limed Juice to the Clarifiers More than one type of commercial arrangement

for the distribution of limed juice to the clarifiers had been tried at Tongaat without success when it was decided to design a plant to perform this im­portant function. Incidentally, unsuccessful plant included vee-notch weirs and submerged adjustable gates.

The requirements of the plant were:— (a) The proportion of the total factory flow of

juice lo each clarifier should be easily adjust­able over a wide range (including zero, i.e. clarifier shut off).

(b) Once set, the ratios of the flows to each clari­fier should be unaffected by variations in the total factory flow. i.e. the proportions to be independent of the total.

(c) The flow to each clarifier should be easily and accurately measurable at all flow rates.

Attaining these objectives was complicated at Tongaat by:—

(i) The wide variations in flow stemming from two different-sized milling trains which gave nominal crushing rates of 0, 120, 180 and 300 tons/hour, depending on what plant was running.

(ii) Wide variations of clarifier capacities, with two 24 ft. Dorr and four 22 ft. Bach clarifiers.

The above objectives have been successfully achieved under all conditions of operation in a rela­tively simple and inexpensive manner by distributing the juice from a quiescent tank through a series of adjustable Cippoletti weirs. Cippoletti weirs were chosen in preference to vee-notch weirs for two major reasons. First, the vee-notch form does not permit simple adjustment whilst retaining the pro­portionality condition (b) above. Secondly, the vee-notch discharge being proportional to H2-5 suffers from a markedly bunched scale for large values of H, which means that precision of measurement is sacrificed at large flows.

An excellent weir form for the required purpose would be a suppressed rectangular weir for which the discharge Q is given by—

Q = 3.33 LH1-5 in f.p.s. units where L is the length of weir and H the height of the free upstream liquid surface above the base of the weir. A series of such weirs with a common base level positioned round a tank would discharge in the ratio of their lengths. However, if a simple gate were introduced to adjust the length L of such a weir, its form would be changed immediately to that of an unsuppressed weir. With two end contrac­tions the flow from a rectangular weir becomes Q = 3.33 (L - O.l H) H'-5.

Apart from the more complicated calculation this implies, the property of Q being proportional to L for a given H has now been lost. This means that the ratio of the flows through different weirs would no longer be independent of the total flow. This was the problem which led to the selection of a Cippoletti weir form.

A Cippoletti weir is a trapezoidal weir whose side angle 6 (Fig. 1) is selected such that the increase of length with height just compensates for the effect of the end contractions and the formula for such a weir reverts to the desired form of—

Q = 3.33 LH1-4

The angle 9 for this property was determined by Cippoletti to be such that tan 6=0.25.

Page 123

Proceedings of The South African Sugar Technologists' Association — June 1970 105

FIGURE 1: Illustration of a Cippoletti weir.

If Q is expressed in metric tons per hour while H and L are given in centimetres the equation for the flow of juice (S.G. 1.06) over a Cippoletti weir is-

O = 0.06795 x L x H1-1

The product 0.06795 x H1-5 was calculated for different values of H and these values used to con-

SCALE A

SCALE B

^OUTLETS

w?a

SCALE A

SCALE B

O

WEIRS

QUIESCENT

ZONE

I-o o

NLET

FIGURE 2: T.S.C. juice distribution tank.

FIGURE 2A: Details of scales in Figure 2.

struct the (scale A) which indicated the height of juice above the weirs. Hence the product of this reading and the weir opening in centimetres read from another scale (scale B), gave the quantity of juice passing through the weir.

Details of appropriate H/L ratios, free ventilation and chamfered edges, etc., required in the design of such a box can be found in any standard hydraulics or engineering handbook. The arrangement of the Tongaat installation is depicted diagrammatically in Fig. 2.

A check on the accuracy of these weirs was made on a number of occasions by comparing the calcu­lated flow through the weirs with the recorded flow from an orifice plate. The agreement was within 1-2%.

A problem which was found with the weir box was a build up of sand which was such in the latter part of the year that it was necessary to flush it out once per week. To facilitate this operation it is desir­able to have the bottom sloping towards the drain outlet.

Clarifiers Although all the heated juice at Tongaat passed

through a suitable flash tank the Bach clarifiers had flash tanks which were attached to each unit. One of

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106 Proceedings of The South African Sugar Technologists' Association—June 1970

these had been removed a few years ago when some test work was being carried out on this clarifier and it had functioned satisfactorily since then without the flash tank. The other Bach flash tanks were re­moved during the past season and no problems have been experienced as a result. It should be mentioned that the emergency overflow of the Bach clarifier was located in its flash tank, but in view of the rela­tively large diameter of these clarifiers such an over­flow was considered to be unnecessary under pre­sent circumstances. The main advantages of their removal were the reduction in maintenance and pro­vision of extra space on the clarifier floor. It was noticed thai the juice entered the clarifier at a slightly higher temperature after they had been removed.

T.S.C. operated two 24 ft. Rapidorr clarifiers and in the past it had been found that one of them had a marked tendency to retain caked mud in the mud compartments. A close study of the units was made in order to find the cause of the difference in per­formance. Two features that were noted were—

(a) different rates of rotation of the scraping gear; and

(b) juice take-off pipes in the one clarifier were set about 20 cm too low.

Although these two features were modified to bring the characteristics of the unsatisfactory clarifier into line with the better one it was not successful in achieving the desired improvement.

After seven weeks of operation in July/August the mud in the lower mud compartment had built up to the level of the inspection port. On the other hand, no significant mud build up occurred during the last 16 weeks of operation. Analysis of juice samples from this clarifier after a week-end shut-down showed a greater increase in R.S.R. than did any of the other clarifiers. Some comparative data of the R.S. ratios after a week-end shut-down were:—

5.26 and 7.12 6.36 and 10.16.

Juice Retention in Clarifiers

Trials run in Bach clarifiers at 55 and at 80 tons juice per hour seemed to indicate that there was less loss of sucrose with the lower retention time of 1.7 hours compared with 2.4 hours. This conclusion was based mainly on the change in R.S.R. from clarifier feed to clarified juice. As a guide to what happens in the clarifier it is sug­gested that this comparison is more meaningful than the change in R.S.R. from mixed juice to clarifier juice which is sometimes used as a rough indicator.

Filter Station

The retention of the filter station was known for some time to be low and attempts were made to improve it. These filters had been altered some years ago in such a way that the feed entered through two pipes in the bottom of the tray and the overflow was taken off from the one end instead of along the length of the filter.

Observations showed that the sprays were im­pinging too strongly on the cake and also delivering too much water. This resulted in erosion of the cake and dilution of the bagacillo/mud mixture in the filter tray. Consequently retention was being re­duced in two ways, viz., by—

(a) washing off cake which had been picked up by the filter; and

(b) diluting the feed to the filter which has often been shown to result in lower retention.

New finer sprays were fitted and this did lead to improved results. Using water at a pressure of 3.8 bar absolute, these sprays delivered 200 ml/minute over a circle of diameter 20 cm when the spray was set 20 cm from the filter drum. However, it is still possible for the operator to add too much water on the top of the filter with the above-mentioned effects, but the answer to this is considered to lie in proper training of the operators.

A further aspect of filter operation which was examined was the setting of the cut off and applica­tion of vacuum to the panels of the filter drum. It was found that for a particular filter different panels appeared to cut off at different heights above the mud discharge point while some panels did not appear to break vacuum completely. It was only towards the end of the season that the cause of this unsatisfactory behaviour, viz. eroded or incom­plete brass strips separating the panels, was found. The leaks occurred between the drum and the strip as well as on the screen side of the strip. Some leakage of vacuum also occurred on the strips seal­ing the ends of the panels. It is expected that the necessary attention to this will result in a further im­provement in filter operation.

One other modification which seemed to have been well worth while was the fitting of steaming pipes along the length of the filter drums. These were set approximately 25 mm from the drum and con­sisted of 1.5 in. n.b. pipes with 1/16 in. diameter holes drilled at | in. centres. These were used to steam-clean the filters using 7 bar gauge steam once every two days and examination has indicated that after a full season's operation the screen and com­partment behind it were still in a satisfactory state of cleanliness" for filter operation. Consequently it was not necessary to use the caustic soda cleaning treatment which had proved so successful on a pre­vious occasion.

Pan Boiling Attention is drawn here to one aspect of the

operation of continuous centrifugals curing C masse-cuite, viz. the effect of irregular size grain. While a continuous machine can cope much more readily than a batch machine with a boiling containing all sizes of grain there can be appreciable loss of small crystals through the screen. Because of this, particu­lar attention must always be paid to the grain regu­larity of the C boilings. At T.S.C. it was found that the regularity of boilings was not satisfactory and investigation showed that a major cause of this was the introduction of fine crystal in the B molasses and more especially in the wash from the double curing

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June 1970 Proceedings of The South African Sugar Technologists' Association 107

of C sugar. The presence of the exceptionally large quantity of crystal in the wash was a direct result of crystal breakage in the continuous C fore-curers. A very noticeable improvement was achieved by dissolving this grain through the use of thermostatically controlled silent steam blowers on the pan suction tanks.

Stirrers were also employed so that localized over­heating, which would cause caramelization, was minimized and also the feed to the pans was main­tained at a uniform temperature. By heating the liquor in the suction tanks only, the amount of de­composition attendant on this practice was further minimized.

Discussion Mr. van Hengel (in the chair): Tongaat uses steam

blowers to improve the position regarding crystal in wash.

I think the present system of storage tanks for B-molasses should be reconsidered. These have been replaced at Mount Bdgcombe by one large vertical tank, which pumps continuously to a blow-up tank and continuously overflows so that solution of fine particles is taking place.

It may be that the difference in reducing sugar ratio between limed and clarified juice should be investi­gated before the difference between mixed juice and clarified juice but what do these differences really convey to us?

Dr. Graham: A major reason why Tongaat operates as at present is the belief that decomposition can be minimised by holding molasses in storage at as low a temperature as is practicable.

Hence, only the molasses in the pan feed tanks is heated to dissolve fine grain.

The reducing sugar differences referred to are used as an indicator of chemical changes in the clarifier.

Dr. Matic: Is it the intention to measure pH at the boiling point of the juice?

Dr. Graham: No, because we do not know how to clean electrodes at boiling point with the ultrasonic cleaner.

The other problem is that the electrodes simply do not last, whether they are being cleaned or not.

Dr. Matic: Dr. Parker mentioned a German make of electrode which would stand up to these condi­tions.

Mr. Cargill: Did Tongaat solve the problem of differences in clarifier capacities?

Mount Edgecombe last year installed an automatic flushing system for their electrodes.

Dr. Graham: Although we have modified the clari-fiers and are now using a reliable measuring device which controls the flow of juice, we are still having trouble and are getting an uneven build-up of mud.

Mr. Renton: Empangeni did at one stage introduce mechanical wiping of electrodes but this is no longer carried out.

Mr. Chiazzari: I am very interested in Tongaat's clarification system.

Regarding filter stations and the scaling up of the backing screens we have found that we cannot leave our screens for a week before cleaning them and we try and purge them every eight hours.

In connection with fine grain in wash, our centri­fugals are fitted with a device operated by a timer, to feed water into the monitor casing.

By diluting the molasses in the casing, a smaller pump is required and much of the dissolving of fine crystal is affected.

We put low pressure vapour into our tanks and we seldom have trouble with microscopic grain coming back.

Dr. Graham: Our after-curers were continuous machines but we did not add water and often the wash looked more like massecuite than molasses.

Regarding our filters, an operator on each shift is responsible for two and he normally cleans one machine every second day.

In connection with clarification, the pH of the clari­fied juice is governed by two factors: (1) it should be minimum otherwise the quantity of final molasses is excessive; (2) we do not want an increase in re­ducing sugars from clarified juice to syrup, which is indicative of sucrose hydrolysis.

Mr. Bruijn: This morning we heard that the pH must not be too high because of decomposition of reducing sugars and because more molasses would be made.

Now we are told not to keep the pH too low be­cause we will increase reducing sugars in the syrup.

There is no exact point where the one reaction stops and the other starts.

Dr. Graham: A compromise is necessary when de­ciding the pH at which the juice must be controlled. This value should be such that the destruction of both sucrose and reducing sugars is minimised.

Mr. van Hengel: The construction of our evapora­tors must be able to cope with the conditions which are optimum both ways and there is need for an intensive investigation.

Mr. Jullienne: Regarding bleeding of filters, it is important that they be properly cleaned at shut-down.

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108 Proceedings of The South African Sugar Technologists' Association — June 1970

TRIALS ON B.M.A. CONTINUOUS CENTRIFUGALS By G. G. CARTER

The Tongaat Sugar Company Limited

The Tongaat Sugar Company installed 10 new B M.A. K850 continuous centrifugals at the start of the 1969/70 season as a replacement for 19 obsolete batch type C machine used as forecurers.

The appreciable savings in maintenance and operational labour which were anticipated were realized, as well as lower final molasses purities.

This paper deals with the experience gained while operating these machines during the 1969/70 season and it must be stressed that these results are based on the difficult C massecuite conditions in S.A.

Description of the Machine The B.M.A. K850 (Fig. 1) is a continuous machine

comprising a vertically mounted conical basket spinning at 2,200 r.p.m. The angle of the cone is W and the top and bottom diameters are 850 mm and 360 mm respectively. The gravity factor is 2,265 measured at the top of the basket diameter, at full speed.

The drive is by means of a 30 kW electric motor mounted behind the centrifuge and connected to the basket spindle by means of five vee belts. The basket has no flywheel but requires a 10-minute wait to come to rest should the machine be switched off.

Lubrication of the two main bearings is done by a separate oil pump, which in case of failure switches off the main drive and a pilot lamp (see Fig. 1).

The distribution cone is elaborate and consists of an acceleration cup plus feed cone whereby the massecuite is both fed on to the screen and also lubricated with steam and water prior to the massecuite being purged on the screen.

The type of screen used for the curing of low-grade massecuite has slots 0.06 mm wide and 2.2 mm long and was composed of nickel with a hard chrome surface.

Massecuite was fed from a static finned reheater only capable of reheating 0.86 m3h—l per machine from 40°C to 55°C with water of 60°C. The unit was

KBS0

1199(A)

BMA TO 201 - 2 0 - 0 2

FIGURE 1

Page 127

RfffflWPHPHPiWffl' WH*WJPWWSPfPPmP«

Proceedings of The South African Sugar Technologists' Association — June 1970 109

unsuitable for the quantity of massecuite to be re­heated since the heating surface was well below requirements.

Massecuite flow from the reheater could be con­trolled by an automatic diaphragm valve. The con­trolling impulse comes from the power taken by the drive which is proportional to the feed rate. Because of fluctuations in the electrical supply to the machines these valves opened and closed ad lib. and were also electrically unreliable. The net result was that manual operation was adopted.

Wash water could be added through sprays at the apex of the basket as well as mid-basket whilst water could also be added inside the distribution cone to provide lubrication of the feeding massecuite (see Fig. 2).

Steam injection is provided inside the distribution cone to warm the massecuite (see Fig. 2).

Inspection of the sugar is possible on the top of the monitor casing and of the molasses by means of an inspection plate on the molasses drain.

Investigational Aspects A programme of work was drawn up and the

following points were studied:— (a) The effects of the temperature and quantity

of water and steam added in relation to the sugar quality and consequently machine throughput.

(b) The effects of the temperature and quantity of water and steam added in relation to the molasses purity.

(c) The effects of crystal size on the sugar and molasses purities.

(d) The effects of massecuite purity and its vis­cosity effects on machine throughput and molasses purity.

(e) The effects of massecuite temperature and its viscosity effects on machine throughput.

(f) The reliability of the machines with respect to screen life, electrical problems and com­ponent life, etc.

Thermometer thermometer thermometry termtmetro

Durchflu/bnengenme sser flow meter dibit metre medidor de paso misuratore di quantta

FIGURE 2

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110 Proceedings of The South African Sugar Technologists'' Association — June 1970

Results and Discussion In compiling the results the average conditions

from a series of experiments have been quoted and the various points dealt with in the order mentioned under investigational aspects.

(a) Tests to see the effects of the quantity of water on sugar quality and molasses purity.

1. From visual tests it was clearly seen that water added to the feed cone was essential to serve as a lubrication medium to the molasses film adhering to the sugar crystal and the sugar would not cure with­out it. The water which could be added by nozzles to wash the purging sugar on the screen was shown to wash the sugar through the screen if used in any quantity, or raised the final molasses purity, and consequently was never used.

2. An interesting feature of the tests was that the ratio of lubrication water to massecuite increased in a non-linear fashion as the throughput of massecuite was increased from 0.71 m3 to the maximum which was of the order of 1.23 m3h—\ This is shown in Table I and Graph 1.

TABLE I The effects of massecuite throughput on the amount of water

needed to effect a sugar purity of + t~---

m3 of Mass. per hour

0.72 0.87 0.99 1.15 1.23

Amt. of water Ratio of water in litre/hour

26.0 37.0 60.0 81.0 94.5

Mass. *

1.0 1.2 1.7 2.0 2.2

Purity of C sugar

86.7 85.8 84.7 84.8 84.3

* The ratio of water/mass, is calculated in this column using 0.72 cubic metres as a base.

The high ratio of water needed at the upper range of throughput resulted in a dilute molasses which was below the target refractometer brix of 86.0 set to prevent the operators adding too much water and thus washing excess sucrose into the final molasses.

1 '" re IIO s< *

D M

0-7O * - ' ' • •— • ' l-O IZ /••* / • « / • » 2-0 3-2

RATIO litres/ hour m3/hour

GRAPH 1: Showing effects of massecuite throughput on the amount of water needed to produce a sugar of 85.0 purity.

3. The effects of the quantity of water on sugar purity and molasses purity were found to be such that:—

(a) A point can be reached where the sugar purity will not increase much above a certain level however much water is added.

(b) The excess water merely serves to dilute the molasses brix to below an acceptable level and increased the difference between nutsch and final molasses purity.

(c) The increase in difference between final molasses and its nutsch purity became most marked with rising use of wash water when the sugar purity exceeded a level of 85.0.

TABLE ri The effects at 0.92 mah-1 (constant throughput) of increasing the

rate of water addition on sugar purity molasses brix and purity rise.

Rate of water Rise in Nutsch addition in 1/h Sugar Purity Molasses Brix difference

40.0 83.7 87.5 1.4 80.0 85.8 84.3 1.7

120.0 86.3 80.6 2.3 160.0 86.8 76.8 3.1

(b) Tests to see the effects of water temperature on sugar quality and molasses purity.

A series of experiments were conducted to see the effects of water temperature on sugar purity and the tests clearly showed that water at 80° C was better than at 60° C or 40° C in that less water at the higher temperature was needed to produce a superior quality C sugar.

TABLE III The effects of wash water temperature on the throughput and purity

of C sugar

m* of Mass Average Temp, of Purity Amount per Purity the wash of the of wash Molasses

hour of C Mass water °C C sugar water 1 /h Purity

0.99 58.5 80 84.7 46 38.6 0.97 58.6 60 84.1 55 37.9 0.99 58.8 40 82.7 66 38.3

(c) Tests to see the effects of steam on sugar quality.

Steam, at Tongaat, was found to be necessary to improve the quality of sugar produced at through­puts above 0.72 m3h—l. Attempts were made to see what steam pressure was most beneficial. Whereas J. Chen and workers in Peru showed an improve­ment in sugar quality between 1 and 2 atmosphere steam, at Tongaat no difference could be detected and the lower pressure steam was used. The quan­tity of steam added was increased by using a 6 mm copper pipe instead of a 3 mm copper pipe and the generally hotter atmosphere gave visually im­proved sugar quality. It was further seen that the lower the purity of the massecuite the more beneficial was the steam in producing higher purity C sugar by most probably providing better viscosity reduc­tion. This latter observation has not yet been con­firmed by quantitative measurements. With increas-

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Proceedings of The South African Sugar Technologists' Association —

ing steam pressure a higher molasses purity can be expected. (d) Tests to see the effect of increased massecuite

temperature on machine capacity and the quality of sugar produced.

Results are seen in Table IV where the effects of purging massecuite at 50° C and 60° C are shown. It is seen that the machines are able to use less water/m3 of feed at the same throughput and also can purge more massecuite at 60° C than 50° C. The rise in nutsch purity was, however, the same in both instances. This seems strange in the light of expected rise in molasses purity due to re­solution, but could have been disguised by the need for less wash water.

TABLE IV Illustrating the effects of massecuite temperature on maximum

throughput and water /feed ratio.

Masse­cuite

Temp. "C

60 50 60 50 60 50

Masse­cuite

Purity

59.5 59.7 58.7 58.3 58.0 59.1

Sugar Purity

86.3 85.2 85.7 85.9 85.8 84.3

Through­put in

m3

0.98 0.99 1.05 0.99 1.06 0.96

Molasses Amount Nutsch of water

Difference litre/hour

1.5 50.0 1.4 56.0 1.5 50.0 1.7 60.0 1.6 55.0 1.6 63.0

(e) Tests to see the effect of massecuite purity on machine throughput and the quality of molasses produced.

Massecuite purity was set at different levels during the season and it was seen that the general tendency was for the lower purity massecuite to take longer to purge, though at the start and finish of the season 56.0 purity (5:1 refractometer brix) massecuite was boiled and handled very well.

It is a known fact that the lower the third massecuite purity (at least to 55.0 (5:1 refracto­meter) the greater will be the probability of low molasses purity.

This was illustrated at T.S.C. where the purity of third massecuite was raised from 57.7 average for the period (8th June, 1969, to 14th June, 1969) to 58.8 for the period (15th June, 1969, to 21st June, 1969) and the molasses purity rose from 37.5 to 38.1. The following table shows the average molasses purity and its equivalent massecuite purity for the period of 42 weeks during the 1969/70 season.

Group

36.6—37.5 37 38 39

6—38.5 6—39.0 1—39.5

Number in Group

15 12 6 6

Average Nutsch Purity

37.1 37.9 38.9 39.4

Average Mas-secuite Purity

58 58 59

21 66 10

59.75

Similar results were found in tests conducted at Darnall as shown in the extract quoted below:—

"Massecuite Purity: This varied between 54.0 and 60.6. An attempt has been made to correlate mas­secuite purity with the nutsch purity to give an indi-

— June 1970 111

cation of whether a low massecuite purity leads to a potentially lower molasses purity.

In the first case, the nutsch purities were placed in the following groups:—

30.0—30.9 31.0—31.9 32.0—32.9 33.0—34.9

Each group was averaged with the corresponding massecuite purities and the following results were obtained:—

Group

30.0—30.9 31.0—31.9 32.0—32.9 33.0—34.9

Number in Group

9 19 12 9

Average Nutsch Purity

30.65 31.62 32.31 33.63

In the second case, the massecuite placed into groups, i.e.:—

Group

54.0—55.9 56.0—57.0 57.1—58.0 58.1—59.0 59.1—60.0

Number in Group

7 12 11 11 8

Average Nutsch Purity

31.66 31.98 31.82 32.55 32.60

Average Mas­secuite Purity

56.65 57.05 57.60 59.17

purities were

Average Mas­secuite Purity

55.34 56.65 57.61 58.72 59.40

From these results, one can say that the lower the massecuite purity, the lower will be the nutsch purity. That is, the lower the massecuite purity the greater is the potential of the massecuite to yield a lower purity of final molasses."

(f) Tests to see the effect of grain size on sugar and molasses purity from the continuous machines.

During the course of the season tests were con­ducted on the C massecuite grain size in order to assess its effect on sugar ipurity and molasses purity.

At the beginning of the season the grain size was of the order of 0.29 mm in length and massecuites were full of false grain. This slowed purging and produced sugar with a low pol and molasses of higher than necessary purity. The effects of false grain are very pronounced on continuous machine molasses purity, more so than in a batch machine where the crystal bed filters out the false gra in-giving, admittedly, a poor quality sugar.

Attempts were made to boil a larger grain but these merely served to reduce third-stage exhaustion since insufficient crystal was present so that a great amount of false grain still occurred.

Consequently, boiling techniques were changed to give a massecuite with many nuclei so that the false grain was greatly reduced and the grain size, be­cause of uniformity, still kept to 0.29 mm average. This grain gave improved curing and better quality sugar.

An interesting point which emerged was that the sugar produced by the continuous machines con­tained a lot of fine grain which, when made into a magma with B molasses, raised the purity of the

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112 Proceedings of The South African TSugarechnologists' Association — June 1970

wash from the after curers and caused more C strikes to be boiled. Double curing was thus abandoned and a noticeable improvement in third-stage recovery observed. (g) Tests made to observe the distribution pattern

of massecuite being purged on the centrifugal screen.

Using a stroboscope the distribution pattern of m/c on the screen of the machine was observed and the cause of many of the phenomena affecting the throughput of these machines seen.

The impeding effects of the distributor webs are such that lobes of massecuite under high pressure are sent up the basket at speeds which prevent satis­factory purging. Sketch No. 1 illustrates the pattern of these lobes on the basket.

(a) ACCELERATION CUP WITH INFLOW OF MASSE­CUITE

(b) WEB IMPEDING FLOW OF MASSECUITE TO BASKET

(c) MASSECUITE ON THE INSIDE OF THE FEED CONE

(d) FEED CONE DOWN WHICH MASSECUITE MOVES TO BASKET,

(e| HIGH SPEED LOBES OF MASSECUITE

(f) PURGED C SUGAR

(9) BASKET

SKETCH 1: Distribution pattern of massecuite on basket of B.M.A. centrifuge.

The effect of these lobes is to cause carry-over which contaminates the sugar with unpurged mas­secuite. This effect becomes greater as the through­put feeding these machines is increased. It also ex­plains why there is a need for a greater ratio of water to massecuite feed so as to reduce the viscosity of molasses film adhering to the sugar to low limits and thus enable purging of the high-speed zones. A throughput of greater than 1.14 nVh-1 resulted in a badly cured C sugar and 1.43 m3h—1 was never attainable. This carry-over effect explains why it is best to operate these machines at ± 0.86 m3h~' as the amount of wash water needed to achieve any sugar pol is significantly less, meaning less chance of washing sucrose into the molasses. Also the quality of sugar produced is of a higher value mean­ing less recirculation. From the above discussion it is thus recommended for South African conditions that when purchasing these machines a capacity of 0.86 nVh-' be considered as optimum.

It should be mentioned that the supplier has elaborated a modified massecuite feeding device which underwent preliminary tests at Darnall last season, and a 30% throughput increase was experi-

(h) The mechanical and electrical reliability of these machines.

A brief discussion of the mechanical features of

the machine shows that structurally the machines appear well made with the exception that:—

(a) The feed distributor webs on five out of ten machines sheared, causing lost time of up to 24 hours for their repair.

(b) Controllers supplied by Siemens were fitted to each of the ten B.M.A. machines in order to obtain automatic control of the massecuite feed. The signal to the controller was the wattage drawn by the motor driving the centrifugal basket. Deviations from the set point effected the required opening or clos­ing of the massecuite valve. The controller could be desensitized so that undesirable momentary fluctuations of up to 10% due to electrical interference would not alter the set­ting of the massecuite valve.

Experience showed that these controllers under Tongaat conditions were not satis­factory. This was due to voltage fluctuations exceeding 10%, causing hunting of the con­trol system.

It is appreciated that a technical solution can be found by, for example, installing a voltage stabilizer. Such an answer can, how­ever, be expensive.

(c) The screens tended to blind due to the deposi­tions in the screen slots of chrome deposits which were cleaned by placing the screens for two minutes in a flat bath of Hibitol and then washing with water and covering with a saturated solution of sodium carbonate. This problem is overcome by regular washing of the screens with hot water 3 times every 24 hours.

In order to check the screens a slide of molasses was taken once a shift and if high traces of sugar crystal were observed the machine was stopped to check for screen damage. The number of screens rejected be­cause of being irreparably damaged during the season totalled eight. The screens were eroded at their base by massecuite impinging above the wearing ring. In order to prevent this it is necessary to skim the base of the acceleration cup, thus lowering the feed cone in relation to the wearing ring. The changing of screens takes 45 minutes.

Conclusions The points which have emerged as being opera­

tionally desirable are:— 1. Steam of 1 bar absolute pressure should be pro­

vided through a 6 mm copper pipe to provide a good hot atmosphere for feeding in the massecuite.

2. Water at 80° C is best added via the distributor cup.

3. To ensure maximum sugar quality and mini­mum water addition (thus eliminating excess molasses dilution and consequential excess rise be­tween final molasses and nutsch purity) the machines need to be run at ± 0.86 m3_1 until the feed arrangement is improved to eliminate the tongues of contaminating unpurged massecuite.

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Proceedings of The South African Sugar Technologists' Association —

4. An operator is essential and needs to be sup­plied with information every hour on special notice boards. This information gives sugar quality (not below 85.0 purity) and molasses brix (of not less than 86.0 brix) thus ensuring minimum water usage and rise in molasses purity. The great advantage of continuous machines is that they afford the pro­cess manager the ability to control recycling since the C sugar quality can be varied within limits. The machines need constant operator attention to obtain the best results at all times.

5. If the massecuite could be fed hot (at 60° C), using very rapid reheaters to ensure minimum re­solution, then increased throughput and lower water usage can be expected.

These machines earned revenue by achieving sav­ings as follows:—

1. Only one operator per eight-hour shift is re­quired to work 10 continuous machines with savings in labour previously needed to operate 19 old batch-type machines, amounting to R21,000 per annum.

2. Savings in maintenance over the comparable number of batch-type machine are estimated at R3.000 p.a.

3. The earnings in revenue to Tongaat of these machines in one year has meant a gain in BHR of 0.8% which means additional revenue of some R80,000. This figure is high because of previous serious deficiencies in equipment. The earnings ability for a factory well equipped with fully auto­matic batch machines would be less.

The following table shows the massecuite purity and molasses purity which was obtained by the T.S.C. from 1962 to 1969 and shows dramatically the ability of the continuous machines in 1969 to cure a low purity third massecuite and its subse­quent production of low-purity molasses.

Massecuite Massecuite Final Mol. Type of Brix

*97.2 97.2 97.0 97.4 97.8 97.1 97.3 96.6

Purity

*57.3 59.3 58.6 59.6 59.5 59.8 59.9 60.3

Gravity Pur.

37.8 40.5 39.8 41.2 41.1 40.5 40.0 40.9

Year

1969 1968 1967 1966 1965 1964 1963 1962

C Centrifug

Continuous Batch

„ „ „ ,,

»!

* These two figures calculated from refractometer data using measured differences between refractometer and spindle brix. The difference in molasses purity between the 1969 year and the lowest year from 1962 to 1968 is 2.0%, which represents some 1.0% in BHR.

Acknowledgements The author wishes to thank all those members of

staff who assisted during the course of this investi­gational work and to also thank the Tongaat Sugar Company for permission to publish this paper.

Discussion Mr. van Hengel (in the chair): I concur with the

five points mentioned in the conclusion of your paper, except where it is stated that we must aim for the

— June 1970 113

highest possible sugar purity. Darnall has decided, unlike Tongaat, to maintain

double curing even with continuous machines. If we settle for a purity of C — sugar of 80, then

it is possible from a normal massecuite purity to have a circulation of 130. This is not pure enough to go to the remelter — it must be double cured.

As plenty of water is necessary and some capacity is lost by trying to get higher purity sugar, I think that it is better to settle for a slightly lower sugar purity and to double cure it.

Mr. Carter: Our view is this. Why buy fifteen machines and use ten to produce sugar of 80 purity when you can use fifteen to produce sugar of 85 purity with a lower recirculation load?

When you purge to a high purity you will have more molasses to dispose of.

Mr. Chiazzari: If you double cure, the molasses is being circulated to the C-massecuite.

If you single cure, are you not returning the re­circulation back to the raw sugar?

Mr. Carter: Yes, but we prefer to use as many machines as possible in order to get the minimum recirculation. We want to use all our machines to get the highest possible quality sugar.

Mr. van Hengel: The industry has spent a lot of money on the remelt system, which is designed basic­ally to crystallise our first product out of the most pure surroundings — to get the best sugar. This object is defeated if we do not double cure, particularly as this system has presented no difficulties.

Mr. Archibald: Has Tongaat experienced building up of sugar in the machines? It has been so bad at Empangeni that the machines have tripped. We now stop and wash down one machine daily.

We have also had trouble with the massecuite im­pinging onto the screen.

I agree with Mr. Carter that constant operator attention is necessary to ensure smooth running of the machines.

Mr. Hulett: I wish to refer to the correlation be­tween low massecuite purity and low molasses purity.

Before monthly averages are taken for massecuite and molasses purities, it can be seen that a very low purity molasses has been obtained from a high purity massecuite.

I feel we should put on a machine to drive a pan so that the same condition could be produced all the time and we might then be able to take a step forward in boiling C-massecuites.

Mr. Carter: On the basis of probability, when you boil a lower purity massecuite you will obtain a lower purity molasses.

It would be interesting to have mobility meters to indicate viscosities in our pans when boiling because of the different purities during the season.

Mr. Moor: Regarding the automatic controls for the massecuite feed. We were under the impression that they were operated from the amperage of the motor driving the centrifugal. But it is not purely an amperage control as it does take account of voltage fluctuations, but it becomes inaccurate under the con­ditions of voltage fluctuations such as sugar mills tend to have. However, the manufacturers are taking steps to correct this.

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114 Proceedings of The South African Sugar Technologists' Association — June 1970

IMBIBITION RE-CYCLING

By M. H. PHIPSON

Pongola Sugar Milling Company Limited

The generally accepted form of imbibition applica­tion considered at present to give optimum milling results is Quintuple Compound Imbibition, when re­ferring to six-unit milling tandems. The Imbibition % Fibre applied varies from mill to mill and falls in the 200% to 400% range. The mean Imbibition % Fibre for all South African factories for the year 1968/1969 was 286%.

An on-site inspection of any operating milling train incorporating inclined inter-carriers and Donnelly chutes will reveal that with an Imbibition % Fibre application of 268% the bagasses in transit between mills after imbibition application is not saturated. Further imbibition is not usually possible due to lack of evaporator heating surface or an adverse factory steam balance.

With these two factors in mind Imbibition Re­cycling was embarked upon. The object of re­cycling is to saturate the bagasse in transit between mills and an Imbibition % Fibre rate of at least 500% is necessary. This can be achieved in practice as indicated by re-cycle diagram (Fig. 1).

A weir is placed in the imbibition tank and a re­cycle pump installed. The re-cycle pump has first

call on the imbibition and when re-cycle rate is achieved, imbibition will flow over the weir at the normal or applier imbibition rate and be pumped to the next mill.

Re-cycling was introduced to our mills Nos. 2, 3, 4, 5 and 6, using four pumps and varying the combinations thereof.

Indifferent results were obtained when re-cycle was applied to No. 2 and No. 6 mills.

Best results were obtained on a combination of mills 3, 4 and 5 to which re-cycling was applied simultaneously for a greater part of the 1969/1970 crushing season at an Imbibition % Fibre rate of approximately 500%.

At this imbibition rate drainage became a problem and reabsorption over the top mill roller occurred. This was overcome by the installation of deflection plates at the bottom of the Donnelly chutes which deflected the bagasse away from mill top roll flanges and nose plates. A void round the outside periphery of the rolls is formed and drainage through the mill is achieved. This is assisted by setting the front plate of the Donnelly chute tangentially to mill top roll as per Fig. 2.

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Proceedings of The South African Sugar Technologists' Association —June 1970 115

Fig.2.

Test and Results—Observations Table I shows tabulated individual milling results

for week ending 23rd August, 1969, with no re­cycling.

Table II shows tabulated individual milling results for week ending 30th August, 1969, with re­cycling mills 3 and 4.

By comparison re-cycling appears to increase unit extraction by 6.64% for No. 3 mill and 6.33% for No. 4 mill, although last mill figures are inconsistent. Total increase in extraction for W.E. results under comparison was 0.34%.

TABLE I Individual Mill Test Week Ending 23rd August, 1969,

No Re-cycling

Moisture Sucrose %

Bagasse Total Extraction Unit Extraction Unit Extraction

Efficiency

1 55.10

9.60 70.99 70.99

2 54.30

7.14 80.31 9.32

3 54.20

5.18 86.54 6.23

4 53.72

5 53.72

6 53.60

3.46 91.51 4.97

2.40 94.19 2.68

1.90 95.53

1.34

TABLE II

Individual Mill Test Week Ending 30th August, Re-cycle Nos. 3 and 4 Mills

Moisture Sucrose %

Bagasse Total Extraction Unit Extraction Unit Extraction

Efficiency

1 55.80

9.33 72.04 72.04

2 54.20

7.13 80.82 8.78

3 53.50

4.78 88.17 7.34

4 52.33

2.92 93.28 5.12

5 52.21

2.03 95.26 2.17

1969,

6 53.47

1.79 95.87 0.41

72.04 31.40 38.29 43.25 32.38 9.13

TABLE in

Individual Mills Test No. 4 Mill with or Without Re-cycle

70.99 32.13 31.65 36.92 31.56 23.14

Moisture Sucrose % Bagasse ... Total Extraction Unit Extraction Unit Extraction Efficiency

No Re-cycle 3

56.40 4.45

88.22

4 55.65 3.20

91.97 3.75

31.82

Re-Cycling 3

55.65 4.70

87.72

4 56.15 3.10

92.15 4.43

36.55

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116 Proceedings of The South African Sugar Technologists'" Association — June 1970

Further tests were run on individual mills separ­ately. The re-cycle pump of a particular mill was run and then stopped at intervals of 30 minutes. Samples of bagasse and back roll juice were taken during the two conditions over a prolonged period and compared. Table III shows a comparison of No. 4 mill with and without re-cycle and Table IV shows a similar test on No. 5 mill.

TABLE IV

No Re-cycle 4 5

Re-Cycling 4 5

Moisture Sucrose %" Bagasse ... Total Extraction Unit Extraction Unit Extraction Efficiency

57.40 3.80

89.64

55.15 2.80

92.95 3.34

32.24

56.90 3.50

90.71

55.90 2.30

94.21 3.49

37.61

Discussion Mr. van Hengel (in the chair): I would like to ask

three questions:— (i) How do you define unit extraction efficiency,

and is imbibition liquid included or ex­cluded?

(ii) Is saturation prior to imbibition necessary? (iii) Will not the deflector plates, four inches

apart, reduce the size of the mill by eight inches, with a consequent loss of throughput, although there is a possible gain in extrac­tion?

Mr. Phipson: Unit extraction efficiency is the per­centage of available sucrose extracted by each mill.

I think saturation is necessary before imbibition. At Pongola there are old apron carriers between mills and the imbibition rate is 300% and the recycling is at 700 or 800%.

The deflection plates do reduce the width of the mill but the plates do not go into the throat of the mill so the bagasse balls out and its density is reduced, allowing drainage.

Mr. Moor: The author mentioned that samples were taken at particular points across the last mill and that high sucrose and moisture in bagasse were found on the edges. If the experiment was repeated, even without the reduction of the chute on the final mill, he would probably get the same result because the deflector iplates would cause a lack of compression on the edge of the mill.

Regards recycling, there is a sufficient difference in the brix between juice extracted from any one mill and the free juice in the bagasse leaving that mill to warrant recycling juice back onto that mill in the hopes of improved extraction.

We carried out trials at Tongaat but did not have adequate drainage in the mills and we did not have laboratory capacity to get sufficient results to come to any conclusions on recycling.

I understand Mount Edgecombe has also tried re­cycling but without showing any improvement.

Tongaat intends to study recycling again now that we have sufficient drainage.

Mr. Hulett: Mr. Phipson says recycling on the last mill pushed up moisture in bagasse so much as to al­

most put the boiler fires out. And yet from the tables recycling appears to have no effect on the bagasse moisture of the other mills.

Hippo-Valley is also recycling through the apron carrier and they claim increased extraction.

In a five roller Walker mill, where it is easy to separate the juice from the feeder rollers, this juice only can be recycled.

Mr. Phipson: I do not know why the moisture in bagasse of the last unit increased so appreciably seeing it did not do so on the preceding mills. How­ever, we stopped the imbibition recycling immediately.

Mr. Kramer: The author presupposes that the imbi­bition water does not mix properly with the bagasse layer. But is this so? When the bagasse goes through the two rollers of a mill, the maceration present in the blanket is forced out in a solid stream and so all the bagasse particles are saturated.

Mr. van Hengel: The Australians are convinced that imbibition takes place when bagasse enters the first opening of the mill. Such a strong stream of liquid pushes forward against the bagasse that satura­tion must take place.

Could not recycling assist in drastically reducing the amount of water applied to mills while retaining the same extraction?

Mr. Phipson: We are not taking a chance on whether the imbibition water comes in contact with the bagasse or not so we increase the imbibition and apply recycling.

Regarding reducing imbibition by applying recyc­ling, as imbibition and extraction are directly related, the more imbibition applied the more chance there is of good extraction.

Therefore, recycling will not replace imbibition — it is merely an attempt to improve extraction without installing additional plant.

Mr. Newton: The more water you apply the more work you have to do in the boiling house. Neverthe­less I feel we should support recycling because there is a prospect of gain and we do ensure saturation of bagasse.

It is very important to have adequate drainage of the milling tandem.

I think we should experiment by applying less maceration and less recycling and this would partly solve the drainage problem.

What is the optimum value of recycling? It must be borne in mind that the juice expressed

contains highly abrasive materials which are being recirculated and cause extra wear.

Mr. Phipson: I am not sure what the optimum value of recycling should be.

Mr. Renton: Huletts mills have for a long time been geared to take high imbibition rates and because of the value now being attached to fibre this re­cycling technique could become useful.

Recycling can be achieved without additional pumps by modifying existing piping arrangements.

Mr. Phipson: Pipes can be modified for one mill, but for more than one mill you require an additional weir or an additional pump.

Page 135

Proceedings of The South African Sugar Technologists'1 Association — June 1970 117

SUMMARY OF AGRICULTURAL DATA: SUGARCANE CROP 1968/69 AND 1969/70

By J. L. DU TOIT and M. G. MURDOCH

South African Sugar Association Experiment Station

Introduction As in previous years this summary is based on data

obtained from the Sugar Industry Central Board. The areas used are taken from the Survey of Cane Production conducted in 1969 and the tonnages and sucrose content of cane are from schedules of deliveries.

This year, for the first time, sucrose per cent cane and weight of sucrose produced per unit area are introduced. While the sucrose per cent cane for different regions is of interest, the differences between regions are small and compared with yield differences often insignificant with the result that the order of cane yields and sucrose yields for the different areas are very similar.

All data are, as from this year, given in metric units.

Total Areas and Yields Total areas under cane, total yields and sucrose data

are given in Table 1. The area under cane, while a little higher in the years 1966 and 1967, seems now to have settled down at about 330 000 hectares. There can be no doubt that, if allowances are made for periodic droughts, the average yield of cane per unit area per unit of time is increasing satisfactorily; but unfortuna­tely there are also indications that low sucrose per cent cane values are being recorded in recent years and the sucrose content of cane during the 1969/70 season was again particularly low. The average sucrose content of cane for the 10 year period 1945-1954 was 13.79 per cent and for the period 1955-1964 it was 13.53 per cent with the lowest annual sucroses for this 20 year period being recorded at 13.11 per cent in 1957/58 and 13.12 per cent in 1958/59. Since 1965, however, 13.11 per cent has only been exceeded once, in the 1966/67 season, when it was 13.72 per cent, and in three out of five years a figure below 13.0 per cent has been recorded.

During the 1969/70 season a total of 14.8 million tons cane was harvested with a yield of 5.8 tons sucrose

per hectare of cane under cultivation. This is well below the record figures of 1967/68 but appreciably better than for 1968/69.

Rainfall and Yield The low yields obtained in 1968/69 were due to a

severe drought. Up to the end of February 1969 the 1969/70 crop once again appeared seriously threatened by a most severe drought, but fortunately late rains from March 1969 on, did much to retrieve the situation. The consequent late growth was respon­sible for the season starting off with a very low sucrose content.

Table 2 gives yield and rainfall data for the industry during recent years. It will be seen from the table how very dependent our production is on rainfall but also that the yield per unit of rainfall has increased appreciably during the sixties. The ratio of yield to rainfall has, however, compared with the two pre­vious seasons dropped sharply during the 1969/70 season. This ratio, useful as it is, must be considered as a somewhat crude statistic being influenced by a number of factors some of which, such as going for farm mean peaks, are not connected with efficiency of production. Nevertheless the lateness of the rain must have had a considerable effect in reducing the figure for the 1969/70 season.

Group Production Table 3 shows that European growers were respon­

sible for 71 per cent of the sucrose produced during the 1969/70 season. All groups showed an increased production in 1969/70 compared with the previous season, but the Indian growers showed the greatest percentage improvement, although yields for both Indian and Bantu growers remain low. The rather old but poor yielding cane from the Bantu areas aver­aged slightly higher in sucrose content than cane from the other groups.

TABLE 1

TOTAL AREA UNDER CANE

1st May

1965 1966 1967 1968 1969

haxlO-3

327 339 337 331 330

SEASON

65/66 66/67 67/68 68/69 69/70

TOTAL CROP

CANE txl0-«

8.4 14.1 16.9 13.7 14.8

SUCROSE tx 10-°

1.09 1.93 2.18 1.80 1.91

SUCROSE V

CANE

13.0 13.7 12.9 13.1 12.9

AREA HARVESTED

hax 10-3

119 174 200 182

%

41* 53* 59 55

t CANE/ha

HARV­ESTED

71 81 85 75

UNDER CANE

29* 43* 50 41 45

t SUC./ha UNDER CANE

3.8* 5.9* 6.5 5.4 5.8

(* Area under cane for the previous season used.)