Physical and numerical modeling results for controlling groundwater contaminants following shutdown of underground coal gasification processes
Groundwater contamination has resulted from some of in-situ gasification field tests, and concern over groundwater contamination may hamper commercialization. When UCG recovery operations are terminated, energy remains stored as heat in the adjacent masses of rock and coal ash, and this energy is transferred into the coal seam. Coal continues to pyrolyze as a result of the transferred energy; the products of this coal pyrolysis are a source of groundwater contamination resulting from UCG. A laboratory simulator was developed, and six simulations of UCG postburn coal pyrolysis have been completed. The simulations show that the products of coal pyrolysis are the source of most contaminants associated with UCG operations. Injection of water directly into the UCG cavity can limit postburn coal pyrolysis and reduce the production of contaminants by cooling the masses of rubble and coal ash in the cavity. Water flow through the coal towards the cavity also limits postburn pyrolysis and subsequent contaminant generation; however, steam produced in the heated portions of the coal limits the rate of water flow. Simulation results indicate that UCG field tests should be operated so that the flow of pyrolysis liquids and gases into the formation is prevented and that the natural influx of water into the cavity is allowed. This can be accomplished by minimizing gas leakage to the formation during gasification, venting the cavity after the gasification process is complete, and maintaining low postburn cavity pressures. 11 refs., 17 figs., 17 tabs.
- Research Organization:
- Western Research Inst., Laramie, WY (USA)
- DOE Contract Number:
- FC21-83FE60177
- OSTI ID:
- 6401789
- Report Number(s):
- DOE/FE/60177-2392; ON: DE87013750
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
010404* -- Coal
Lignite
& Peat-- Gasification
010900 -- Coal
Lignite
& Peat-- Environmental Aspects
CHEMICAL REACTIONS
COAL GASIFICATION
CONTROL
DECOMPOSITION
ENERGY TRANSFER
FIELD TESTS
GASIFICATION
GROUND WATER
HEAT TRANSFER
HYDROGEN COMPOUNDS
IN-SITU GASIFICATION
IN-SITU PROCESSING
OXYGEN COMPOUNDS
POLLUTION CONTROL
PROCESSING
PYROLYSIS
RECOMMENDATIONS
SIMULATION
TESTING
THERMOCHEMICAL PROCESSES
WATER
WATER INFLUX
WATER POLLUTION CONTROL