1980: Coal to Ammonia: Its Status

SteamOxygen

(Air»

Coat

Coal

Gas

Slagi

0 500 1000 1500 2000 2500Ash

Gas

Coal

7Steam

Oxygen(Air)

Char

| Gas

Coal

SteamOxygen

r Char

O 500 1000 1500 2000Temperature 'F

Figure 1. Moving bed gasifier. Figure 2. Fluidized bed gasifier.

SYNFUELS PROCESSING:

Coal to Ammonia: Its StatusWithin the next decade or so, coal will become the economicallycompetitive feedstock and fuel for ammonia production.

L. J. Buividas, M. W. Kellogg Co., Houston, Texas 77046

During the Tennessee Valley Authority (TVA) Symposiumon Ammonia from Coal (1), the utilization of coal as thefeedstock for ammonia was greatly emphasized. The poten-tial of coal was forecasted to be competitive by 1985 and by1990 coal-based ammonia would be king. As we all areaware, so far the only coal-based ammonia project in theUnited States is the TVA sponsored facility at MuscleShoals, Alabama, and this project is only a front-end retro-fit for the small existing 204 Mg (225 ton)/d ammonia plant(2).

The purpose of this article is not to predict how or whencoal will become king, but to give an insight on the presentstatus as related to the production of ammonia.

U.S.resources

There are over 100 ammonia plants in the U.S. having thecapability of producing over 18 million Mg (20 million ton)of ammonia per year (3) and which consume over 20 billionm3 (700 billion scf) per year of equivalent natural gas. Theammonia industry relies heavily on natural gas as thefeedstock and fuel. With the possibility that the supplynatural gas will become scarce or uneconomic, other alter-native feedstocks must be explored.

One candidate for supplementing our diminishing gassupplies is coal. The total U.S. coal reserves are estimatedto be over 1360 billion Mg (1500 billion ton) (4-6). Thesereserves include anthracite, bituminous, sub-bituminousplus lignite. The locations of the coal deposits are shown onthe Keystone's map (7) of the U.S. Coal Fields. The coaldeposits within the U.S.—over 390 Mg (430 billion ton) are

0149-3701/81/4698 $02.00 © 1981 AlChE

considered mineable—make up one-fourth the knownreserves in the world and have five times the energy valuesof domestic "recoverable" oil and gas (8).

The conversion of coal to useful gases is not a novelty andhas a history with both surges of interest and abandonment.During 1670, John Clayton is reported to have produced agas by heating coal within a laboratory retort. Over acentury later, W. Murdoch illuminated his home with coal-derived gas during 1792. The first coal gas company waschartered in London during 1812 and lights were installedat the London Bridge. The first U.S. coal gas company wasstarted in Baltimore, Maryland, in 1816.

Clark portrays the rise and fall of the coal gasificationindustry in the United States (9). More than 11,000 gasproducers were in operation during 1926, gasifying about13.6 million Mg (15 million ton) of coal per year. By 1948,only 4,000 units gasifying 3.6 million Mg (4 million ton) peryear were in operation. Today, only a few coal gas producersexist, and most of these have been mothballed. Althoughthe advent of natural gas in the 1940s and early 1950s had adepressing effect, the Federal Government did sponsorresearch for the gasification of coal through the Office ofSynthetic Liquid Fuels. At present, as a result of the oilembargo during the early 1970s and the increasing cost ofoil, interest in coal gasification has reawakened.

Various gasification systems

Without going into the details of the chemistry, a reviewof the main reactions (5,9,10), which probably occur duringthe gasification of coal, are:

67

Coal'fi

SlagSteam

Oxygen

Gast

fCoall

i Steamj OxygenI I i J_ _L »Slag

500 1000 1500 2000 2500

Figure 3. Entrained flow gasifier.

C + O2 = C02 (Combustion-Oxidation)C + H2O = CO + H2 (Steam-Carbon)C + CO2 - 2CO (Boudouard)C + 2H2 = CH4 (Hydrogasification)

In addition, there are at least two reactions that alter thegas composition in the coal gasification reactor or in thesubsequent processing units:

CO + H20 = C02 + H2 (Water Gas Shift)CO + 3H2 = CH4 + H2O (Methanation)

Figure 4. "Two-headed" gasifier.

Raw gasLiquid slag

6 Granulated slag

2 Gascompressors w

Rectisolsulfur

removal

2 Gascompressors

RectisolGOj removal

- *-

»

Nitrogenwish

*-

¥

Synthesisfas

compressor

Figure 5. AECI No. 4 ammonia plant.68

STEAM

AIR

NH3

* SULFUR

SLAG

Figure 6. Ammonia manufacture.

In simple terms, gasification systems can be classifiedinto three categories and each has been applied by threetechnically proven processes (9,11):

The Moving Descending Bed Process is practiced byLurgi, Figure 1. Since the coal moves slowly down thereactor, a more correct term would be a gravitational flowgasifier.

The Fluidized Bed Process, as shown on Figure 4, is adesign offered by Winkler (Davy McKee).

The Entrained Flow Process design is the type commer-cialized by Koppers-Totzek. Such a system is morecommonly known as the suspension reactor and is indicatedon Figure 5.

Texaco (12) and Shell-Koppers (13, 14) are activelyengaged in pilot unit and demonstration plant develop-ments with higher pressures utilizing the entrained flowprocess.

The above processes differ with respect to the parame-ters:

Reaction temperaturesFlow directions of reactants and productsResidence time of coal particlesSize range of feed coalThe obvious differences between the three processes,

Figures 1-3, are the gas outlet temperatures. Due princi-pally to variation of the gasification temperatures, theproduct gas compositions are also different.

New developments

Before going into the economics of coal to ammonia,summarized are the latest coal gasification programs whichare presently being sponsored, either entirely or partially,by the Department of Energy (DOE) (8). Several processeshave emerged from laboratory research as potentially prom-ising "second generation" technologies. Many have passedtheir first engineering tests at the "process developmentunit" stage and have been scaled up to the larger "pilot

plant" stage.Some of the major pilot plants include (8,15):HyGas. Operated for the Gas Research Institute by the

Institute of Gas Technology, Chicago, 111.BiGas. Operated for the Gas Research Institute by the

Bituminous Coal Research working with Stearns-Rogers,Inc., Homer City, Pa.

CO2 Acceptor. Operated for the Gas Research Instituteby Conoco Coal Development, Rapid City, South Dakota.Completed operations in 1977.

Synthane. Operated by the C-E Lummus Co., Bruceton,Pa. Operations ceased in December, 1978.

In addition, DOE is funding design studies for largerdemonstration plants. Three current designs are based on:

British Gas/Lurgi Slagging Gasifier. This is theadvanced version of the Lurgi and is being developed by theConoco Coal Development Co. in cooperation with theBritish Gas Co. A pilot-scale unit was tested at Westfield,Scotland.

CoGas. Being developed by the Illinois Coal GasificationGroup. Process was tested at pilot scale in Leatherhead,England.

The third demonstration plant is being designed byProcon, Inc., using data from the HyGas pilot plant.

More highly advanced coal gasification processes arepresently being developed. Three of them are:

Flash hydropyrolysis by Rockwell International.Catalytic gasification by Exxon Research & Engineering

Co.Westinghouse. Fluidized bed pressure gasification.Two firms—W.R. Grace and Memphis Light, Gas &

Water Division—are currently designing large demonstra-tion plants that will produce medium-Btu fuel gas forindustrial processes. The W.R. Grace plant will be locatedat Baskett, Ky., and will use the Texaco process. Memphisis to use the IGT U-Gas process and is to be located outsideof Memphis, Tenn.

During 1980, DOE will evaluate these two designs and the

69

IQ «TEAM MUM

mOMSIEMiniUM

TO STEAM DRUM

MOUNT STEUNMOERaf nan»

STEMM

OMR/ASHCMIWEYOR

Figure 7. Fluid bed gasifier.70

I

£Ml

.£

Ir

Figure 8. Ammonia from coal.

Crashed i ~3\cool »*

Feed-lockhopper

Pretreatment (if necessary)

Steam generation

Gasifier

Air (or oxygen) and steamAir (or oxygen) and steam l

Ash-lock hopper | 'f. {"~i Water

Ash/water

Figure 9. Ash-agglomerating gasifier, U-gas.

Row gas topurification

Second-stagedust removal

71

market for medium-Btu gas and will determine which, ifeither, of the projects should proceed toward construction.

Although the DOE projects and others are directedtoward high- and medium-Btu gas, the technology beingadvanced will be useful for the production of ammonia andfor other critical chemicals, such as ethylene, methanol, etc.

Present technologyNow that the coal resources and background of the coal

gasification processes have been reviewed, a summary of thepresent-day commercial coal gasifiers, which can be utilizedto produce synthesis gas (for ammonia) are presented inalphabetical order.

Koppers-Totzek uses the entrained bed coal gasifier,Figure 4, at essentially atmospheric pressure (14, 16). Theprocess flow-scheme for ammonia production is depicted onFigure 5. The investment for a complete self-sufficient 900Mg (1,000 metric ton) per stream day ammonia plant isreported to be about $200 million as of the first quarter of1979 (14). The investment includes the coal-handling, air-separation unit, coal gasification, raw gas purification,nitrogen wash unit, compression, ammonia synthesis,required refrigeration, off-gas and off-water treatment, plussteam generation, power generation and the cooling waterfacilities.

Since 1950, there are 20 ammonia plants having thecapacity range of 54 to 907 Mg (60 to 1000 ton)/d ammoniaproduction based on the K-T coal gasification process (14).

SIPM, BV and Krupp-Koppers GmbH have been devel-

NITROGEN . 1000 TPD

Figure 10.Production

ofammoniafrom coal,

U-gas.

GASEOUS STREAMS

SOLID STREAMS

PURGE GAS

72

HOTCARBONATE

RECYCLE HYDROGEN1200 TONS/DAY

oping the pressure-entrained bed gasifier since 1974 andthat an experimental unit, with a daily throughput of 136Mg (150 ton) of coal, has been in operation since early 1979(14).

The Lurgi gasifier, Figure 11, is a reactor for the perfor-mance of counter-current coal gasification in a slowlymoving bed under pressure, preferably at 3 MPa (30 bar)(17). The Lurgi coal-based ammonia plant flowsheets areshown on Figures 12 and 13. The main difference betweenthe two schemes is that for the first case, Figure 13, the offgases from the nitrogen wash unit are recycled throughsteam reforming and shift conversion whereas the secondscheme, Figure 12, has a separate ammonia plant for theoff-gases. The total cost (17) for a self-sufficient 907 Mg(1000 metric ton) per stream day NH3 plant includingoff-sites is about Deutsch mark (DM) 300 x 106 (equivalentto 160 M U.S. dollars) as of the first quarter of 1979. Twoammonia plants based on the Lurgi coal gasification process(16) had been placed into operation during 1956 and 1962,respectively.

The Texaco process scheme for the generation or rawammonia synthesis gas is indicated on Figure 14. The coalgasifier is a pressurized, entrained flow reactor (12). TheTexaco process for the production of ammonia from coal isshown on the block diagram, Figure 6. As of January, 1979,Texaco's capital cost estimate for a completely erectedbattery limits 907 Mg (1000 metric ton) per day ammoniaplant (Gulf Coast) is 134 million dollars for a bituminous,coal-based plant (12).

Winkler uses a fluidized bed gasifier, Figure 7, whichoperates at essentially atmospheric pressure (18). Since

COAL

DRYINGCARBONIZATION

GASIFICATION

COMBUSTION

02

STEAM

CRUDE GAS

ASH

Figure 11. Lurgi gasifier.

1926, 12 ammonia plants based on the Winkler coal gasifi-cation process have been placed into operation. ,

Figure 8 shows the block diagram for a high capacityammonia plant based on the Winkler coal gasificationprocess (18).

During the May 1979 TVA Symposium, Davy indicatedthat a grass-roots 1088 Mg (1200 ton)/d ammonia plant willhave a capital cost of 175 million dollars excluding coalhandling and storage, waste water treatment, administra-tion and maintenance building, ammonia product storageand shipping.

U-Gas. The Institute of Gas Technology (IGT) has beenactive in the development of a fluidized-bed gasifier, knownas the U-Gas process (19). Figure 9 is a sketch of the U-Gasgasifier (20). A flow-scheme for the production of ammoniais shown on Figure 10. IGT (19) has estimated that theinstalled cost (first quarter 1979) to be $149 million for aself-sustained 1088 Mg (1200 ton)/d ammonia plant.

Economics

In evaluating the coal technology for the production ofammonia, the capital and the energy costs are the keys for/the selection of the process. A number of factors play'important roles in the development of plant investment-^such as plant size & location; equipment, bulk material &transportation costs; contracterai considerations; costs oflabor & capital; and the international market situation.

The approximate investments for the coal-based ammo-nia plants were given previously. To determine how thevarious available feedstocks compete, the proponents of thevarious coal gasification processes have developed produc-tion cost curves. These are given in the following figures:

Krupp-Koppers (14)—Figure 15.Texaco (12)—Figure 16.Winkler-Davy McKee (IS)—Figure 17.U-Gas—IGT (19)—Figure 18.Examination of the curves reveals that the costs to

produce ammonia are in close agreement. A composite ofthe curves is shown on Figure 19 (21). To select thefeedstock for ammonia production, the delivered price ofthe fuels must be adjusted for differences in the efficiencyof use and in the capital and operating costs for differentfuels. At present, natural gas is the lowest cost raw material.Based on the 1985 projected prices of fuel (21), the cost toproduce ammonia will be almost the same using either coalor natural gas. If the predicted unit fuel costs do not deviatefrom the projected prices, by 1990 the coal-based ammoniaplants should be more economical, and by the year 2000coal will have a significant advantage over all other fuels.

In conclusion

Due to the low probability that large new gas and oilreserves will be discovered, the future prices of oil and gasare expected to increase rapidly. Even if the costs do notrise, the United States energy policy, directed towardslimiting imports and increasing the security of energysupply, is that the reliance on domestic coal resources willbe desirable.

Our coal reserves are tremendous and the cost of coal willprobably climb more slowly than the price of oil and gas. Ifthe energy prices rise as predicted, coal will be competitivefor ammonia production by 1985, definitely by the year2000. Thus, for economic energy policy reasons, coal willbecome the preferred feedstock and fuel for ammoniaproduction within the next decade or so. #

Literature cited1. Tennessee Valley Authority Symposium, "Ammonia from Coal" (May

8-10,1979)2. Waitzman, D. A., et al., "Ammonia from Coal," AIChE Safety in

73

MAKE UP VÄTER COAL 143 t/h9000 KW 1000 m3/h 800 »6 teol/h

i,, COAL HANDLING

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1 '

RECTISa

'i UQUD NITROGEN VAS

L VÄTER TREATMENT j*J 1

*NH3 SYNTHESIS

Figure 12. JAmmonia plant, NH3

coal-based dOOM/dav)case 2.

INVESTMENT COST(without cos based armnom plant)

206 Mio DM(with gas DQSCU ammona punt;

263 Me DM

„ ,z , * «. C.TITA»J um PO

fh=564 X^hoal/h

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t, ftAf. 1 im VIO TDCATfcJTMT^ UA3 LAJLUn InCAImtrll

». ., 188 ID teaiyhJ1 ADD FLEL GASA

18710ßlcol/h

p NH3 PLANTJ STARTING

' | CH^GAS

' ' V

3010 t TAROL/h NH3

0452 1 GASNAPH1A/h 25 t/h0.236 1 PHENOLE/h IBOOtAtey)s 31.4 1Q6lcal/h

|J

i

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835

COAL 89 l/h500 106 hcal/hHo=5600 hcol/h

INVESTMENT OOST 175 Mb CM

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coal/h STEAM BOLE*

ooal/h: 375

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! VÄTER TREATMENT

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REcnsaLOUD NITROGEN VASH LFua

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TNH3

416 t/h(1000 t/day)

1.920t lAROL/hQ287t GASNAPK1A/h01671 PHENOLE/h

S 20 »5|cQl/h

Figure 13. Coal-based ammonia plant, case 1.74

OXYGEN

COAL

WATER

SLURRY

PREPARATION

SLAG

COAL/WATERSLURRY

GASIFIER

SYNTHESIS GAS

RAW

RECYCLEWATER

SLAG

SLAGDEWATER1NG

SOOT/WATER

SYNTHESIS GAS

PARTICULATE FREE

GAS

SCRUBBER

CLARIFIEDRECYCLEWATER

CLARIFIER

SOOT/WATER RECYCLE

SOOT/WATER

MAKEUP

WATER

Figure 14. Direct quench mode.

260

240 -

220 -

200 -ja6

u9I

i050 100 I.SO 2.00 2.SO 3.00 3 SO 400 4.50

NATURAL GAS COST OR COAL COST, $/!06

I I I I I25 50 ?5

COAL COST, $/ton100

Figure 15. Costs: ammonia vs. rawmaterial, 907 Mg (1,000 ton)/d capac-ity.

Ammonia Plants Symposium, San Francisco, Ca. (November 25-29,1979).

3. "Brighter Days Ahead in Ammonia?" Farm Chemicals (March, 1979).4. U.S. Geological Survey (January 1,1967).5. Beckett, C. W., et al., Conference on Thermodynamics and National

Energy Problems, National Academy of Sciences, Washington, D.C.(June, 1974).

6. Chapter 27, "Factors Affecting Use of Coal, Modern Energy Technology,II, Research and Education Association (1975).

7. "Keystone Coal Industry Manual," McGraw-Hill Publ. (1973).8. "Gas from Coal Fossil Energy Technology," DOE (May, 1979).9. "Clark, E. L. "Coal Gasification—The State of the Art," TVA Ammonia

from Coal Symposium (May 8-10,1979).10. Chapter 37, "Modem Energy Technology," II, Research and Education

Assoc. (1975).11. Baron, G., C. Hafke, and H. Vierrath, "Present Status and Further

Developments of Lurgi Pressure Gasification Process," 3rd InternationalSymposium, Antwerp (October 20-21,1976).

12. Child, E. T., "Current Status of the Texaco Coal Gasification Process,"TVA Symposium (May 8-10,1979).

13. van der Bürgt, M. J., "Clean Syngas from Coal," Hydrocarbon Process-ing (January, 1979).

14. Beck, B., "The Koppers-Totzek Coal Gasification Process and Its RoleIn Today's Coal-Based Nitrogenous Fertilizer Production," TVASymposium (May 8-10,1979) (& Private Communications).Vogt, E. V., and M. J. van der Bürgt, Chem. Eng. Prag., p. 65 (March,1980).

15. Chapter 26, "Modem Energy Technology" II, Research and EducationAssoc. (1975).

16. Wintrell, R., "The K-T Process: Koppers Commercially Proven Coal andMulti-fuel Gasification Synthetic Gas Production in Chemical andFertilizer Industries," Salt Lake City (August 18-21,1974).

17. Becker, P. D. "Lurgi Pressure Gasification and Its Application forAmmonia Manufacture," TVA Symposium (May 8-10,1979).

18. Bailey, E. E., "Winkler Coal Gasification Process and Its Application inAmmonia Synthesis Plants," TVA Symposium (May 8-10,1979).

19. Patel, J. G., and D. Leppin, "The U-Gas Process for Ammonia Manufac-ture," TVA Symposium (May 8-10,1979).

20. Patel, J. G., "Clean Fuel from Coal Is Goal of U-Gas Process," Oil & GasJ. (August 1,1977).

21. Nichols, D. E., P. C. Williamson and D. R. Waggoner, "Assessment of

75

Alternatives to Present Day Ammonia Technology with Emphasis onCoal Gasification," Symposium on Nitrogen Fixation, Madison, Wis.(June 12-16,1978).

40O-J (SI conversion: Mg - ton x 0.907}

1000 METRIC TONS NH3/OAY347 DAYS/YEAR

40 (00 14020 40 60 80 100 120

PRICE OF FEEDSTOCK AND FUEL.$/METRIC TÖN

160

Figure 16. Cost: ammonia vs. feed-BlUUK. O.I1U 1UC71.

210

200

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160

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GASIFIER PRESSURE PSIA

Figure 17. Ammonia from coal, 19791st quarter.

L. J. Buividas, coordinator for inorganic chemi-cals technology for Pullman Kellogg, is responsiblefor improvement of existing processes and develop-ment of new technology. The holder of a B.S.Ch.E.from Tri-State Univ., a B.S. in petroleum engineer-ing from Tulsa Univ., and a M.S. in petroleumrefining engineering from the same school, he haswritten numerous articles relating to ammonia andhydrogen production.

2.00 2.50 3.75 5.00THERMAL PRICE OF RAW MATERIAL IN $/MM BTU

6.25

Figure 18. Ammonia selling price vs.feedstock cost.

450

S/MMBTU 0

NATURAL GAS LS/MCF 0

NAPHTHA, S/ton

FUEL OIL, S/fabl

COAL, S/ton20 40 60 80 100

ELECTRICITY, Umil/KWH 0

120 140

I

160

10 15 20 25

Figure 19. Revenue vs. feedstockcosts.

76

DISCUSSION

MARX, C.F. Industries: I would like to ask you or much work is being done on it?maybe anybody else in the audience. I know it's BUIVIDAS: There have been some announcementstough. Isn't it the natural way to gasify coal under- made to that effect. As far as the cost is concerned, Iground? How much is being spent on it and how have no idea.

77