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AssigneeThe United States of America as represented by the United States Department of Energy
InventorLarry A. Bissett
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The present invention is directed to a method of in situ coal gasification for providing the product gas with an enriched concentration of carbon monoxide. The method is practiced by establishing a pair of combustion zones in spaced-apart boreholes within a subterranean coal bed and then cyclically terminating the combustion in the first of the two zones to establish a forward burn in the coal bed so that while an exothermic reaction is occurring in the second combustion zone to provide CO.sub.2 -laden product gas, an endothermic CO-forming reaction is occurring in the first combustion zone between the CO.sub.2 -laden gas percolating thereinto and the hot carbon in the wall defining the first combustion zone to increase the concentration of CO in the product gas. When the endothermic reaction slows to a selected activity the roles of the combustion zones are reversed by re-establishing an exothermic combustion reaction in the first zone and terminating the combustion in the second zone.
A method for increasing the concentration of carbon monoxide in the gaseous product resulting from the in situ gasification of coal in a subterranean coal bed, comprising the steps of providing a pair of boreholes penetrating the coal bed at locations spaced from one another a distance sufficient to establish a combustion zone in each borehole, initiating an exothermic combustion reaction in both of said boreholes to establish combustion zones therein, supporting the combustion of the coal to provide a temperature in each combustion zone of about 2000.degree. F by conveying combustion-supporting medium into and discharging the resulting gaseous products of combustion from each combustion zone, maintaining the flow of combustion-supporting medium to the first combustion zone while interrupting the flow of combustion-supporting medium to the second combustion zone, maintaining the discharge of the gaseous products from the second combustion zone while interrupting the discharge of the gaseous products from the first combustion zone, said steps of maintaining and interrupting the flow of the combustion-supporting medium and the discharge of the gaseous products causing the gaseous products from the first combustion zone to pass through the coal bed disposed between the boreholes in a forward burn configuration into the second combustion zone where carbon dioxide in the gaseous products reacts endothermically with hot carbon defining the walls of the second combustion zone to effect the conversion of carbon dioxide to carbon monoxide.
Dependencies are inferred from the claim text.