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ENERGY SELF-SUFFICIENCY AND COGENERATION IN LOUISIANA CANE SUGAR FACTORIES

ENERGY SELF-SUFFICIENCY AND COGENERATION IN LOUISIANA CANE SUGAR FACTORIES. Harold Birkett and Jeanie Stein Audubon Sugar Institute. BOILERS & COGENERATION. OBJECTIVES To present actual data on bagasse availability and analysis

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ENERGY SELF-SUFFICIENCY AND COGENERATION IN LOUISIANA CANE SUGAR FACTORIES

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  1. ENERGY SELF-SUFFICIENCY AND COGENERATION IN LOUISIANA CANE SUGAR FACTORIES Harold Birkett and Jeanie Stein Audubon Sugar Institute

  2. 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

  3. GAS COST ($) / MCF

  4. GAS / TON CANE Hurricane Lili Tropical Storm Isidore

  5. ELECTRICITY COST

  6. TRUE FIBER % CANE 1998-2006 AVG = 11.85; 2006 = 12.39

  7. TRUE FIBER % PREPARED CANE 2005 & 2006 CROPS; AVG = 11.88

  8. TRUE FIBER % BAGASSE 2005 & 2006 CROPS; AVG = 38.08

  9. DRY FIBER (BAGACILLO) % MIXED JUICE 2005 CROP; AVG = 0.39

  10. BAGASSE % CANE 2005 & 2006 MILL TEST DATA; AVG = 31.41 VS 28.77

  11. BAGASSE % CANE FACTORY REPORTED DATA; AVG = 31.8

  12. MOISTURE % BAGASSE 2005 & 2006 CROP (MILLING & BOILER SAMPLES); AVG = 53.86

  13. ASH % BAGASSE 2005 & 2006 CROPS (MILLING & BOILER SAMPLES); AVG = 5.19

  14. ASH % BAGASSE

  15. PRIMARY FACTORS AFFECTING BOILER EFFICIENCY • The quality of the fuel (bagasse). • The quantity of excess air used for combustion. • The temperature of the flue gases. • The completeness of the combustion.

  16. OXYGEN % FLUE GAS 2005 & 2006 CROPS; AVG = 7.99

  17. BOILER EXCESS AIR 2005 & 2006 CROPS; AVG = 72.8

  18. FLUE GAS TEMPERATURE 2005 & 2006 CROPS; AVG = 450

  19. PREHEATED AIR TEMPERATURE 2005 & 2006 CROPS; AVG = 457 F

  20. BOILER EFFICIENCY 2005 & 2006 CROPS; AVG = 55.45

  21. POUNDS STEAM PRODUCEDPER POUND BAGASSE BURNED 2005 & 2006 CROPS; AVG = 1.89

  22. METHODS TO IMPROVEBOILER EFFICIENCY • Improve the bagasse quality (lower moisture & ash). • Reduce the level of excess air. • Reduce the temperature of the flue gases.

  23. EFFECTIVE MOISTURE MOISTURE = 53.99 EFFECTIVE MOISTURE = 56.75 % MOISTURE = 53.99 % FIBER+S.S.=41.15 ASH = 4.86 TOTAL = 100.00

  24. EFFECTIVE BAGASSE MOISTURE VS BOILER EFFICIENCY 2005 & 2006; r=0.58;Effective Moisture = Moisture % Ash-Free Bagasse

  25. EFFECT ON BOILER EFFICIENCY

  26. BOILER EFFICIENCY VSFLUE GAS TEMPERATURE 62 60 56 USING AVG INPUTS, VARYING FLUE GAS TEMP ONLY

  27. 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

  28. 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

  29. CASE 1TYPICAL LOUISIANA FACTORY 10,000 TCD BAGASSE FROM MILL = 238,043 LB/HR 221,594 LB/HR BAGASSE EXCESS BAGASSE = 16,449 LB/HR = 6.9 % BOILERS STEAM 210 PSIG 392°F 447,620 LB/HR FACTORY TURBINES (10,417 HP) BACK PRESS T-G (870 KW) MAKE-UP TO EXHAUST MISCELLANEOUS 20,000 LB/HR 395,088 LB/HR 32,512 LB/HR 0 LB/HR 15,859 LB/HR 350,796 LB/HR 26,752 LB/HR 24,193 LB/HR 10,000 LB/HR CONDENSATE EVAPORATOR LOW GRADE PANS BFW DEAERATOR MISCELLANEOUS QUAD, V1 FOR JUICE HEATERS & HIGH GRADE PANS BUY 3,130 KW

  30. CASE 2HIGH PRESSURE STEAM & QUINTUPLE EFFECT EVAPORATOR10,000 TCD BAGASSE FROM MILL = 238,043 LB/HR 201,231 LB/HR BAGASSE EXCESS BAGASSE = 36,812 LB/HR = 15.5 % BOILERS STEAM 650 PSIG 750°F 344,105 LB/HR FACTORY TURBINES (10,417 HP) BACK PRESS T-G (6,392 KW) MAKE-UP TO EXHAUST MISCELLANEOUS DESUPER- HEATING WATER 20,697 LB/HR 20,000 LB/HR 201,984 LB/HR 122,121 LB/HR 0 LB/HR 315,141 LB/HR 0 LB/HR 19,661 LB/HR 10,000 LB/HR EVAPORATOR LOW GRADE PANS BFW DEAERATOR MISCELLANEOUS QUINTUPLE V1 TO ALL PANS & 3RD LJH V2 TO 2ND LJH, V3 TO 1ST LJH SURPLUS 2,392 KW

  31. CASE 3HIGH PRESSURE STEAM, TOPPING TURBINE & QUINTUPLE EFFECT EVAPORATOR10,000 TCD BAGASSE FROM MILL = 238,043 LB/HR 202,385 LB/HR BAGASSE EXCESS BAGASSE = 35,658 LB/HR = 15.0 % BOILERS STEAM 650 PSIG 750°F TOPPING TURBINE 7,277 KW 210 PSIG/570°F 346,079 LB/HR FACTORY TURBINES (10,417 HP) BACK PRESS T-G (221 KW) MAKE-UP TO EXHAUST MISCELLANEOUS DESUPER- HEATING WATER 18,730 LB/HR 20,000 LB/HR 319,402 LB/HR 6,676 LB/HR 0 LB/HR 315,141 LB/HR 0 LB/HR 19,667 LB/HR 10,000 LB/HR EVAPORATOR LOW GRADE PANS BFW DEAERATOR MISCELLANEOUS QUINTUPLE V1 TO ALL PANS & 3RD LJH V2 TO 2ND LJH, V3 TO 1ST LJH SURPLUS 3,498 KW

  32. 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.

  33. ACKNOWLEDGMENTS AMERICAN SUGAR CANE LEAGUE ALL LOUISIANA SUGAR MILLS

  34. 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

  35. PRACTICAL DEGREE OF COOLING OF FLUE GASES Boiler Outlet Gas Temperature, F = 707 Minimum Practical Flue Gas Temperature, F = 250 Degree of Cooling of Flue Gases, F 457 • POTENTIAL COOLING OF FLUE GASES BY VARIOUS METHODS, F TheoreticalActual Using Air Preheaters 438 257 Economizers 150 150 Bagasse Dryers 427 ? • RELATIVE WEIGHTS OF BOILER FLOWS Bagasse = 1.00 BF Water = 2.10 Air = 3.92 Flue Gas = 4.87

  36. 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: • Complex – multiple conveyors, rotating equipment, and cyclones. • High horsepower requirements – especially for fan on cyclone. • Dry bagasse is a fire hazard. • Higher furnace temperature may improve combustion but may also cause the ash to melt. • Increased pollution (particulate carryover).

  37. BOILER EFFICIENCY VSFLUE GAS TEMPERATURE Practical final flue gas temp = 250 F (requires air preheaters + economizers) 64.84 56.76 Current operation with a/h = 450 F (using only air preheaters) 46.02 No waste heat recovery, flue gas = 707 F

  38. PREPARATION INDEX and MILLING

  39. PREPARATION INDEX VS TANDEM POL EXTRACTION 2005 DATA, r = 0.49

  40. PREPARATION INDEX VS TANDEM POL EXTRACTION 2006 DATA, r = 0.23

  41. PREPARATION INDEX VS FIRST MILL POL EXTRACTION 2005 DATA, r = 0.73

  42. PREPARATION INDEX VS FIRST MILL POL EXTRACTION 2006 DATA, r = 0.18

  43. FIRST MILL POL EXTRACTION VS TANDEM POL EXTRACTION 2005 DATA, r = 0.66

  44. FIRST MILL POL EXTRACTION VS TANDEM POL EXTRACTION 2006 DATA, r = 0.83

  45. FIRST MILL EXTRACTION VSTANDEM (5 MILLS) EXTRACTION 2005 DATA, r = 0.92

  46. FIRST MILL EXTRACTION VSTANDEM (5 MILLS) EXTRACTION 2006 DATA, r = 0.98

  47. FIRST MILL EXTRACTION VSTANDEM (6 MILLS) EXTRACTION 2005 DATA, r = 0.53

  48. FIRST MILL EXTRACTION VSTANDEM (6 MILLS) EXTRACTION 2006 DATA, r = 0.89

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