Pyrolysis of large coal blocks: implications of heat and mass transport effects for in situ gasification. [3 refs; comparison of block and powder pyrolysis]
Dewatering of coal blocks at in-situ moisture levels was shown to markedly affect pyrolysis gas production by being the rate-limiting mechanism in heat transfer, and by causing self-gasification of the block as steam diffuses from a shrinking core of damp coal through a hot, outer layer of char. Cracking of product oil vapors as they diffuse outward may also contribute to the increased combustible gas evolution of block pyrolysis compared to powder pyrolysis. These results influence modeling and design of in-situ coal gasification. Since no data are available on coal-block pyrolysis, improved understanding of heat and mass transfer effects significantly improves semitheoretical models which have depended on powder pyrolysis data. For satisfactory resource recovery, the shrinking core of unreacted coal makes it critical to limit flame-front speed. If the flame front moves too fast, only an outer layer of any large masses of coal will be gasified, leaving damp, ungasified centers behind the front. More experimentation is planned to quantify and expand these results. Specifically, a matrix of experiments is being performed at 0.3/sup 0/C/min and at 3.0/sup 0/C/min, proceeding to maximum temperatures of 500 to 1000/sup 0/C. Analyses will be made of data on oil, char, and gas yields; oil, char, and gas compositions; thermal histories; and oil and gas physical properties. Later experiments are planned to investigate the effects of pressure, reducing gas atmospheres, and other coal ranks (lignites, caking and noncaking bituminous coals). The ultimate result is a satisfactorily accurate model of pyrolysis as it affects in-situ coal gasification.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 7314561
- Report Number(s):
- CONF-770301-13
- Country of Publication:
- United States
- Language:
- English
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Lignite
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010406* -- Coal & Coal Products-- Pyrolysis & Cracking-- (-1987)
CARBONACEOUS MATERIALS
CHARS
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
COAL
COAL GAS
COAL GASIFICATION
COAL TAR OILS
CRACKING
DECOMPOSITION
DESIGN
DIFFUSION
DRYING
ENERGY SOURCES
ENERGY TRANSFER
FLUIDS
FOSSIL FUELS
FUELS
GASES
GASIFICATION
HEAT TRANSFER
IN-SITU GASIFICATION
IN-SITU PROCESSING
MASS TRANSFER
OILS
ORGANIC COMPOUNDS
OTHER ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
PROCESSING
PYROLYSIS
STEAM
THERMOCHEMICAL PROCESSES