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COAL GASIFICATION
GASIFICATION ONLY REASONABLE WHEN PLANT IS INTEGRATED
SOME PROCESSES ARE COMMERCIAL
H2S REMOVAL BY THE CLAUS PROCESS
H2S + O2 = H2O + SO2
H2S + SO2 = S + H2O
Energy Content Summary….
Type Btu/SCF
Producer Gas 90-120
Water Gas 341
Low-Btu 150
Intermediate-Btu 260-300
SNG 950
Methane 1054
Probable Uses….
• Low-Btu gas– Local electrical power generation
– Cannot be used for home or commercial heating
• Intermediate-Btu gas– Electrical power generation
– Feed stock for chemicals
– Town gas
• High-Btu gas…. Same as natural gas
Selection of a Gasifier
• Type of bed• Operating pressure• Slagging, non-slagging
Lurgi (fixed bed, high P, non-slagging)
Koppers-Totzek (entrained bed, low P,
slagging)
Wellman-Galusha (fixed, low P, non-slagging)
Winkler (fluidized, low P, non-slagging)
Figure 7-6. Pipeline gas from coal via Lurgi pressure gasification.
COALPREPARATION
OXYGEN-BLOWNCOAL
GASIFIERS
SCRUBBINGAND COOLING
CRUDE GASSHIFT CONVERSION
H2O+CO=H2+CO2
RECTISOLGAS
PURIFICATION
METHANATION3H2+CO=CH4+H2O
COMPRESSIONAND
DEHYDRATION
ELEMENTALSULFUR * 128 LTPD
CO2
H2S+CO2
GAS LIQUOR
25,303 TPD @ 8,920 Btu/lb FEED COAL
GAS LIQUOR SEPARATIONAND EFFLUENT
WATER TREATMENT
PIPELINE GAS290 MMSCFD@ 950 Btu/Scf
RECLAIMED WATERTO PLANT USE
NAPHTHA
COAL TAR
COAL OIL
PHENOLS
AMMONIA
TOTAL LIQUIDS8940 BBLS/day
155 tons/day
OILYGAS
LIQUOR
SULFURPLANT
TARRY GAS LIQUOR
N2
OXYGENPLANT
AIR
COAL FINES
STEAM
OXYGEN
STEAM ANDPOWER PLANT
ELECTRIC POWERTO PLANT USE
Figure 7-11. The Texaco gasifier (also Shell, Eastman)
System for In-Situ Gasification of Coal
From Wiser, 2000
Inject air and steam
Produce low-Btu gas
Chemical reactions
Financial Dilemma
• Synthetic natural gas cost
- >$10.00/106 Btu• Investment
- 75 x 1012 Btu/year plant, 30 year life
- $8 billion• Benchmark is cost of oil and gas energy sources
- Need a floor on the price of energy over a long time frame