ENERGY SELF-SUFFICIENCY AND COGENERATION IN LOUISIANA CANE SUGAR FACTORIES
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ENERGY SELF-SUFFICIENCY AND COGENERATION IN LOUISIANA
CANE SUGAR FACTORIES
Harold Birkett and Jeanie SteinAudubon Sugar Institute
BOILERS & COGENERATION
OBJECTIVES
• To present actual data on bagasse availability and analysis
• To present data on boiler efficiencies and suggestions for improving them
• To discuss factory modifications to reduce steam usage and increase electricity cogeneration
GAS COST ($) / MCF
0
2
4
6
8
10
12
14
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
CROP YEAR
$ / M
CF
GAS / TON CANE
0.00
0.25
0.50
0.75
1.00
1.25
1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006
CROP YEAR
GA
S, M
CF
Hurricane Lili
Tropical Storm Isidore
ELECTRICITY COST
5
6
7
8
9
10
11
12
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
CROP YEAR
CE
NT
S / K
WH
.
TRUE FIBER % CANE
10.0
10.5
11.0
11.5
12.0
12.5
13.0
1998 1999 2000 2002 2003 2004 2005 2006
CROP YEAR
FIB
ER
, %
CANE FIBER AVERAGE
1998-2006 AVG = 11.85; 2006 = 12.39
TRUE FIBER % PREPARED CANE
0
2
4
6
8
10
12
14
16
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35
SAMPLE
FIB
ER
, %
PREP CANE AVERAGE
2005 & 2006 CROPS; AVG = 11.88
TRUE FIBER % BAGASSE
0
5
10
15
20
25
30
35
40
45
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33
MILL TEST
FIB
ER
, %
.
FIBER, % AVERAGE
2005 & 2006 CROPS; AVG = 38.08
DRY FIBER (BAGACILLO) % MIXED JUICE
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
SAMPLE
DR
Y F
IBE
R,
%
DRY FIBER AVERAGE
2005 CROP; AVG = 0.39
BAGASSE % CANE
202224262830323436384042
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33
MILL TEST
BA
GA
SS
E %
CA
NE
BAG % CANE LESS 1% F%C AVERAGE AVERAGE (WITH 1% LESS F%C)
2005 & 2006 MILL TEST DATA; AVG = 31.41 VS 28.77
BAGASSE % CANE
29
30
31
32
33
34
1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006
CROP YEAR
BA
GA
SS
E %
CA
NE
.
BAGASSE % CANE AVERAGE
FACTORY REPORTED DATA; AVG = 31.8
MOISTURE % BAGASSE
48
50
52
54
56
58
60
62
5 15 25 35 45 55 65 75
SAMPLE
MO
IST
UR
E, %
.
BAGASSE MOISTURE AVERAGE
2005 & 2006 CROP (MILLING & BOILER SAMPLES); AVG = 53.86
ASH % BAGASSE
0
2
4
6
8
10
12
14
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
SAMPLE
AS
H, %
BAGASSE AVERAGE
2005 & 2006 CROPS (MILLING & BOILER SAMPLES); AVG = 5.19
ASH % BAGASSE
0
2
4
6
8
10
12
14
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
YEAR
AS
H, %
.
AVERAGE HIGH LOW
PRIMARY FACTORS AFFECTING BOILER EFFICIENCY
1. The quality of the fuel (bagasse).
2. The quantity of excess air used for combustion.
3. The temperature of the flue gases.
4. The completeness of the combustion.
OXYGEN % FLUE GAS
0
2
4
6
8
10
12
14
16
18
20
BOILER TEST
OX
YG
EN
, %
.
OXYGEN AVERAGE
2005 & 2006 CROPS; AVG = 7.99
BOILER EXCESS AIR
0
100
200
300
400
500
BOILER TEST
EX
CE
SS
AIR
, %
.
EXCESS AIR AVERAGE
2005 & 2006 CROPS; AVG = 72.8
FLUE GAS TEMPERATURE
300
400
500
600
700
BOILER TEST
FL
UE
GA
S T
EM
P,
F
FLUE GAS TEMP AVERAGE
2005 & 2006 CROPS; AVG = 450
PREHEATED AIR TEMPERATURE
300
400
500
600
700
BOILER TEST
PR
EH
EA
TE
D A
IR T
EM
P, F
.
PREHEATED AIR TEMP AVERAGE
2005 & 2006 CROPS; AVG = 457 F
BOILER EFFICIENCY
30
40
50
60
70
BOILER TEST
EF
FIC
IEN
CY
, %
.
EFFICIENCY AVERAGE
2005 & 2006 CROPS; AVG = 55.45
POUNDS STEAM PRODUCEDPER POUND BAGASSE BURNED
0
1
2
3
BOILER TEST
LB
S S
TE
AM
/ LB
BA
G
.
LBS STEAM / LB BAG AVERAGE
2005 & 2006 CROPS; AVG = 1.89
METHODS TO IMPROVEBOILER EFFICIENCY
1. Improve the bagasse quality (lower moisture & ash).
2. Reduce the level of excess air.
3. Reduce the temperature of the flue gases.
EFFECTIVE MOISTURE
EFFECTIVE MOISTURE =
56.75 %MOISTURE = 53.99 %
FIBER+S.S.= 41.15
ASH = 4.86
MOISTURE =53.99
TOTAL = 100.00
EFFECTIVE BAGASSE MOISTURE VS BOILER EFFICIENCY
40
45
50
55
60
65
50 52 54 56 58 60 62 64 66
EFFECTIVE MOISTURE, %
EF
FIC
IEN
CY
, %
.
2005 & 2006; r=0.58; Effective Moisture = Moisture % Ash-Free Bagasse
EFFECT ON BOILER EFFICIENCY
DECREASE INCREASE
MOISTURE %
BAGASSE BY 1%
EFFICIENCY BY
0.8%
ASH % BAGASSE
BY 1%
EFFICIENCY BY
0.5%
BOILER EFFICIENCY VSFLUE GAS TEMPERATURE
40
45
50
55
60
65
70
250 350 450 550 650 750
FLUE GAS TEMPERATURE, F
EF
FIC
IEN
CY
, %
.
USING AVG INPUTS, VARYING FLUE GAS TEMP ONLY
6260
56
BASIC ASSUMPTIONS:
• Grinding rate, tcd 10,000
• Cane, % pol 13.0 % fiber (true) 11.24
• Bagasse, % moisture 54.0 % ash 3.00
• Imbibition % cane 30.0
• Syrup purity 85.0
BASIC ASSUMPTIONS:
• Boiler efficiency,% 55.0• Boiler feed water temp, F 250.0• Power required, hp/tch 25.0• Electricity required, kw/tch 9.6• Turbine efficiency, % 50.0• Turbo-generator efficiency, % 68.0• Misc. steam usage, lb/hr
• Live steam 20,000• Exhaust steam 10,000
CASE 1TYPICAL LOUISIANA FACTORY
10,000 TCD
BAGASSE FROM MILL = 238,043 LB/HR EXCESS BAGASSE = 16,449 LB/HR= 6.9 %BOILERS
CONDENSATE EVAPORATOR LOW GRADE PANS
BFWDEAERATOR
447,620 LB/HR
221,594 LB/HR BAGASSE
STEAM210 PSIG392°F
20,000 LB/HR
MISCELLANEOUSMAKE-UP TO EXHAUST
0 LB/HR
BACK PRESST-G
(870 KW)
FACTORYTURBINES(10,417 HP)
395,088 LB/HR 32,512 LB/HR
MISCELLANEOUS
10,000 LB/HR24,193 LB/HR26,752 LB/HR350,796 LB/HR
QUAD, V1 FOR JUICE HEATERS
& HIGH GRADE PANS
15,859 LB/HR
BUY 3,130 KW
CASE 2HIGH PRESSURE STEAM & QUINTUPLE EFFECT EVAPORATOR
10,000 TCD
BAGASSE FROM MILL = 238,043 LB/HR EXCESS BAGASSE = 36,812 LB/HR= 15.5 %BOILERS
EVAPORATOR LOW GRADE PANS
BFWDEAERATOR
344,105 LB/HR
201,231 LB/HR BAGASSE
STEAM650 PSIG750°F
20,000 LB/HR
MISCELLANEOUSMAKE-UP TO EXHAUST
0 LB/HR
BACK PRESST-G
(6,392 KW)
FACTORYTURBINES(10,417 HP)
201,984 LB/HR 122,121 LB/HR
MISCELLANEOUS
10,000 LB/HR19,661 LB/HR0 LB/HR315,141 LB/HR
QUINTUPLEV1 TO ALL PANS & 3RD LJH
V2 TO 2ND LJH, V3 TO 1ST LJH
DESUPER-HEATINGWATER
20,697 LB/HR
SURPLUS 2,392 KW
CASE 3HIGH PRESSURE STEAM, TOPPING TURBINE &
QUINTUPLE EFFECT EVAPORATOR10,000 TCD
BAGASSE FROM MILL = 238,043 LB/HR EXCESS BAGASSE = 35,658 LB/HR= 15.0 %BOILERS
EVAPORATOR LOW GRADE PANS
BFWDEAERATOR
346,079 LB/HR
202,385 LB/HR BAGASSE
STEAM650 PSIG750°F
20,000 LB/HR
MISCELLANEOUSMAKE-UP TO EXHAUST
0 LB/HR
BACK PRESST-G
(221 KW)
FACTORYTURBINES(10,417 HP)
319,402 LB/HR 6,676 LB/HR
MISCELLANEOUS
10,000 LB/HR19,667 LB/HR0 LB/HR315,141 LB/HR
QUINTUPLEV1 TO ALL PANS & 3RD LJH
V2 TO 2ND LJH, V3 TO 1ST LJH
DESUPER-HEATINGWATER
18,730 LB/HR
TOPPING TURBINE 7,277 KW
210 PSIG/570°F
SURPLUS 3,498 KW
SUMMARY• Improving quality of bagasse (lower moisture and
lower ash) can improve boiler efficiency and increase steam production.
• Boiler efficiency can be improved (in La. primary area of improvement can be through installation of economizers to reduce high average flue gas temperature).
• Even without improvements in bagasse quality or boiler efficiency, use of high pressure steam and more efficient evaporator schemes can make La. factories energy independent or exporters of electricity.
ACKNOWLEDGMENTS
AMERICAN SUGAR CANE LEAGUE
ALL LOUISIANA SUGAR MILLS
BOILER WASTE HEAT RECOVERY
• ASSUMPTIONS (State Average for 2005 & 2006)
– Moisture % Bagasse 53.86– Ash % Bagasse 5.19– Oxygen % Flue Gases 7.99– Flue Gas Temperature, F 450– Preheated Air Temperature, F 457– Boiler Outlet Gas Temperature, F 707– Flue Gas Dew Point, F 150
• PRACTICAL DEGREE OF COOLING OF FLUE GASESBoiler Outlet Gas Temperature, F = 707Minimum Practical Flue Gas Temperature, F = 250Degree of Cooling of Flue Gases, F 457
• POTENTIAL COOLING OF FLUE GASES BY VARIOUS METHODS, F
Theoretical ActualUsing Air Preheaters 438 257Economizers 150 150Bagasse Dryers 427 ?
• RELATIVE WEIGHTS OF BOILER FLOWSBagasse = 1.00BF Water = 2.10Air = 3.92Flue Gas = 4.87
Air preheaters and economizers have no moving parts
and are very dependable. Their use may require fans and
pumps or higher head and horsepower.
Bagasse dryers have the following disadvantages:
1. Complex – multiple conveyors, rotating equipment, and cyclones.
2. High horsepower requirements – especially for fan on cyclone.
3. Dry bagasse is a fire hazard.
4. Higher furnace temperature may improve combustion but may also cause the ash to melt.
5. Increased pollution (particulate carryover).
BOILER EFFICIENCY VSFLUE GAS TEMPERATURE
40
45
50
55
60
65
70
200 250 300 350 400 450 500 550 600 650 700 750
FLUE GAS TEMP, F
EFFI
CIE
NC
Y, %
EFFICIENCY, %
No waste heat recovery, flue gas = 707 F
Current operation with a/h = 450 F (using only air preheaters)
Practical final flue gas temp = 250 F (requires air preheaters + economizers)
46.02
56.76
64.84
PREPARATION INDEX and
MILLING
PREPARATION INDEX VS TANDEM POL EXTRACTION
80
85
90
95
100
65 70 75 80 85 90
PREPARATION INDEX
PO
L E
XT
RA
CT
ION
, %
.
TANDEM EXT
2005 DATA, r = 0.49
PREPARATION INDEX VS TANDEM POL EXTRACTION
80
85
90
95
100
65 70 75 80 85 90
PREPARATION INDEX
PO
L E
XT
RA
CT
ION
, %
.
TANDEM EXT
2006 DATA, r = 0.23
PREPARATION INDEX VS FIRST MILL POL EXTRACTION
40
45
50
55
60
65
70
75
80
65 70 75 80 85 90
PREPARATION INDEX
PO
L E
XT
RA
CT
ION
, %
.
TANDEM EXT
2005 DATA, r = 0.73
PREPARATION INDEX VS FIRST MILL POL EXTRACTION
40
45
50
55
60
65
70
75
80
65 70 75 80 85 90
PREPARATION INDEX
PO
L E
XT
RA
CT
ION
, %
.
TANDEM EXT
2006 DATA, r = 0.18
FIRST MILL POL EXTRACTION VS TANDEM POL EXTRACTION
80
85
90
95
100
40 45 50 55 60 65 70 75
FIRST MILL EXTRACTION, %
TA
ND
EM
EX
TR
AC
TIO
N, %
.
POL EXT
2005 DATA, r = 0.66
FIRST MILL POL EXTRACTION VS TANDEM POL EXTRACTION
80
85
90
95
100
40 45 50 55 60 65 70 75
FIRST MILL EXTRACTION, %
TA
ND
EM
EX
TR
AC
TIO
N, %
.
POL EXT
2006 DATA, r = 0.83
FIRST MILL EXTRACTION VSTANDEM (5 MILLS) EXTRACTION
80
85
90
95
100
40 45 50 55 60 65 70 75
FIRST MILL EXTRACTION, %
TA
ND
EM
EX
TR
AC
TIO
N, %
.
POL EXT
2005 DATA, r = 0.92
FIRST MILL EXTRACTION VSTANDEM (5 MILLS) EXTRACTION
80
85
90
95
100
40 45 50 55 60 65 70 75
FIRST MILL EXTRACTION, %
TA
ND
EM
EX
TR
AC
TIO
N, %
.
POL EXT
2006 DATA, r = 0.98
FIRST MILL EXTRACTION VSTANDEM (6 MILLS) EXTRACTION
80
85
90
95
100
40 45 50 55 60 65 70 75
FIRST MILL EXTRACTION, %
TA
ND
EM
EX
TR
AC
TIO
N, %
.
POL EXT
2005 DATA, r = 0.53
FIRST MILL EXTRACTION VSTANDEM (6 MILLS) EXTRACTION
80
85
90
95
100
40 45 50 55 60 65 70
FIRST MILL EXTRACTION, %
TA
ND
EM
E
XT
RA
CT
ION
, %
.
POL EXT
2006 DATA, r = 0.89
PREPARATION INDEX VS INDIVIDUAL FACTORY TANDEM EXTRACTION
80
85
90
95
100
70 72 74 76 78 80 82 84 86 88
PREP INDEX
TA
ND
EM
E
XT
RA
CT
ION
, %
.
POL EXT
PREPARATION INDEX VS INDIVIDUAL FACTORY TANDEM EXTRACTION
80
85
90
95
100
70 72 74 76 78 80 82 84 86 88
PREP INDEX
TA
ND
EM
E
XT
RA
CT
ION
, %
.
POL EXT
PREPARATION INDEX VS INDIVIDUAL FACTORY TANDEM EXTRACTION
80
85
90
95
100
70 72 74 76 78 80 82 84 86 88
PREP INDEX
TA
ND
EM
E
XT
RA
CT
ION
, %
.
POL EXT
PREPARATION INDEX VS INDIVIDUAL FACTORY TANDEM EXTRACTION
80
85
90
95
100
70 72 74 76 78 80 82 84 86 88
PREP INDEX
TA
ND
EM
E
XT
RA
CT
ION
, %
.
POL EXT
PREPARATION INDEX VS INDIVIDUAL FACTORY TANDEM EXTRACTION
80
85
90
95
100
70 72 74 76 78 80 82 84 86 88
PREP INDEX
TA
ND
EM
E
XT
RA
CT
ION
, %
.
POL EXT
PREPARATION INDEX VS INDIVIDUAL FACTORY TANDEM EXTRACTION
80
85
90
95
100
70 72 74 76 78 80 82 84 86 88
PREP INDEX
TA
ND
EM
E
XT
RA
CT
ION
, %
.
POL EXT
PREPARATION INDEX VS INDIVIDUAL FACTORY TANDEM EXTRACTION
80
85
90
95
100
70 72 74 76 78 80 82 84 86 88
PREP INDEX
TA
ND
EM
E
XT
RA
CT
ION
, %
.
POL EXT
PREPARATION INDEX VS INDIVIDUAL FACTORY TANDEM EXTRACTION
80
85
90
95
100
70 72 74 76 78 80 82 84 86 88
PREP INDEX
TA
ND
EM
E
XT
RA
CT
ION
, %
.
POL EXT
PREPARATION INDEX VS INDIVIDUAL FACTORY TANDEM EXTRACTION
80
85
90
95
100
70 72 74 76 78 80 82 84 86 88
PREP INDEX
TA
ND
EM
E
XT
RA
CT
ION
, %
.
POL EXT
PREPARATION INDEX VS INDIVIDUAL FACTORY TANDEM EXTRACTION
80
85
90
95
100
70 72 74 76 78 80 82 84 86 88
PREP INDEX
TA
ND
EM
E
XT
RA
CT
ION
, %
.
POL EXT
PREPARATION INDEX VS INDIVIDUAL FACTORY TANDEM EXTRACTION
80
85
90
95
100
70 72 74 76 78 80 82 84 86 88
PREP INDEX
TA
ND
EM
E
XT
RA
CT
ION
, %
.
POL EXT
PREPARATION INDEX VS INDIVIDUAL FACTORY TANDEM EXTRACTION
80
85
90
95
100
70 72 74 76 78 80 82 84 86 88
PREP INDEX
TA
ND
EM
E
XT
RA
CT
ION
, %
.
POL EXT
ACKNOWLEDGMENTS
AMERICAN SUGAR CANE LEAGUE
ALL LOUISIANA SUGAR MILLS
TRUE FIBER % BAGASSE
0
5
10
15
20
25
30
35
40
45
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
YEAR
FIB
ER
, %
FIBER, % AVERAGE
AVG = 37.04
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