Coal pyrolysis and methane decomposition in the presence of a hot char bed
The products of coal pyrolysis can have a significant impact on the ultimate products produced from underground coal gasification (UCG) systems, especially the hydrocarbons. As a result, some type of pyrolysis submodel is necessary to successfully model a UCG system. The underground system produces pyrolysis products characteristic of all temperature regimes simultaneously and continuously. In addition, these products undoubtedly are in contact with hot gas, char, and/or ash for a much longer time than is typical in powder pyrolysis experiments. In these experiments coal is continuously fed onto a hot bed of char. The pyrolysis products are swept down through the hot char before being removed from the reactor. In this paper we describe the results of these experiments, which have to date been performed at temperatures of 500 to 900/sup 0/C and pressures of 100 to 600 kPa. The data show that methane production reaches a peak near 800/sup 0/C and that the influence of the modest pressure change from 100 to 600 kPa is small. In conjunction with these lumped experiments we are also looking at the reactions of methane with hot char and gas, partly as a model compound for the pyrolysis process and partly because of methane's importance as a UCG product. We have conducted a variety of experiments using homogeneous reactors and reactors packed with char. The data from these experiments are presented and an engineering rate expression is derived for methane decomposition. The derived expression is consistent with the increased hydrogen production and decreased methane production seen in the continuous feed experiments for temperatures above 800/sup 0/C. We find the methane decomposition expression predicts that for typical UCG processes, methane cannot exist in the presence of char for more than 1.5 minutes at 900/sup 0/C or for more than 30 seconds at 1000/sup 0/C. 16 figures, 5 tables.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 5815831
- Report Number(s):
- UCRL-89009; CONF-830827-7; ON: DE83016563
- Country of Publication:
- United States
- Language:
- English
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010404* -- Coal
Lignite
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010406 -- Coal & Coal Products-- Pyrolysis & Cracking-- (-1987)
ALKANES
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON MONOXIDE
CARBON OXIDES
CARBONACEOUS MATERIALS
CHALCOGENIDES
CHARS
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
CHEMICAL REACTORS
COAL
COAL GASIFICATION
DATA
DECOMPOSITION
ELEMENTS
ENERGY SOURCES
EXPERIMENTAL DATA
FOSSIL FUELS
FUELS
GASIFICATION
HIGH TEMPERATURE
HYDROCARBONS
HYDROGEN
HYDROGEN COMPOUNDS
INFORMATION
MATERIALS
MEDIUM PRESSURE
METHANE
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PYROLYSIS
PYROLYSIS PRODUCTS
SUBBITUMINOUS COAL
TEMPERATURE EFFECTS
THERMOCHEMICAL PROCESSES
VERY HIGH TEMPERATURE
WATER
YIELDS