The Exxon Coal conversion technology we report herein is complicated, and the full exposition of it, as available via the above link, is extended.
But, it might well be worth the effort needed to read, and to attempt to understand the process.
In sum, as we comprehend it, Coal is catalytically reacted with Carbon Monoxide and Hydrogen to generate hydrocarbon liquids, Methane and a still-carbonaceous residue, i.e., "Char".
The liquids are recovered and sent on for refining into product.
The Char is reacted with Steam to produce even more Methane.
A portion of the total Methane produced in both the Coal and the Char gasification zones is recovered and sent on as product.
Another portion of the Methane is reacted with Steam to generate the Carbon Monoxide and Hydrogen required in the first, raw Coal, gasification zone.
Moreover, most of the heat energy required by some of the "endothermic" reactions is generated by other "exothermic" reactions in this "integrated" Exxon process.
The upshot seems to be that we can make both hydrocarbon liquids and a substitute natural gas, concurrently, out of Coal, in a process where most, if not all, of the energy needed to drive the process is derived from Coal.
Additional comment follows excerpts from:
"United States Patent 4,292,048 - Integrated Catalytic Coal ... Steam Gasification Process
Date: September, 1981
Inventor: Robert Wesselhoft, et. al., Texas
Assignee: Exxon Research and Engineering, NJ
Abstract: Hydrocarbon liquids and a methane-containing gas are produced from carbonaceous feed solids by contacting the solids with a mixture of gases containing carbon monoxide and hydrogen in a devolatilization zone at a relatively low temperature in the presence of a carbon-alkali metal catalyst. The devolatilization zone effluent is treated to condense out hydrocarbon liquids and at least a portion of the remaining methane-rich gas is steam reformed to produce the carbon monoxide and hydrogen with which the carbonaceous feed solids are contacted in the devolatilization zone. The char produced in the devolatilization zone is reacted with steam in a gasification zone under gasification conditions in the presence of a carbon-alkali metal catalyst and the resultant raw product gas is treated to recover a methane-containing gas.
Claims: An integrated catalytic devolatilization and steam gasification process for the simultaneous production of hydrocarbon liquids and a methane-containing gas from carbonaceous feed solids ... (and) wherein said carbonaceous feed solids comprise coal.
Summary: This invention relates to the devolatilization and gasification of coal and similar carbonaceous materials and is particularly concerned with an integrated catalytic devolatilization and steam gasification process carried out in the presence of a carbon-alkali metal catalyst to simultaneously produce both a methane-containing gas and hydrocarbon liquids."
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In fact, the full Disclosure reveals and directs that some Carbon Dioxide is co-produced by a couple of stages in the process and is to be removed from the product gases. It's disposition is not specified.
However, it seems logical to us to suggest that a portion of the Methane, produced by the total process and not Steam-reformed to generate Carbon Monoxide and Hydrogen for use in the initial Coal gasification, could, rather than all being shipped out as substitute natural gas product, instead be used to react with that recovered Carbon Dioxide, in a bi-reforming or tri-reforming process, such as explained best for us so far by Penn State University, but for variations of which, developed by others, US Patents have been granted, all as we've previously reported, to recycle that Carbon Dioxide in the production of additional liquid hydrocarbons, such as Methanol.
In any case, we have herein yet further, thirty years-old, confirmation, from our own United States Government, that we can produce all the "methane" and the "hydrocarbon liquids" we need out of our own domestic Coal.