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