Experimental studies on humidified/water influx O2 gasification for enhanced hydrogen production in the context of underground coal gasification

Abstract

Underground water present in aquifer has the tendency to encroach during underground coal gasification (UCG) operation because of pressure reduction in the reservoir. The water seepage into the cavity can act as a source for H2 production through char-steam gasification and water gas shift reaction. The enhanced production of H2 raises the production of hydrocarbons in UCG product gas. Low temperature steam or superheated steam can be used for the production of H2 enriched syngas in the in-situ gasification operation. However, low temperature steam causes difficulty in sustaining the combustion front in a UCG seam while superheated steam may lose its sensible heat through pipelines or ash heap in case of deep coal seam. It is necessary to utilize a cheaper gasifying medium for replacing steam in UCG for economic operation. In the present study, four different experiments were conducted using three different coal blocks, which are having similar properties, in order to simulate both the effect of ground water influx and O2/moisture gasification in the context of UCG. Novel humidified oxygen experiments show a better alternate to the steam based UCG gasification for enhanced production of H2 and hydrocarbons. Results show that a maximum concentration of 31% H2, 21% CH4 and 3% C2H6 is generated using humidified oxygen as a gasifying medium.