Underground coal-air gasification based solid oxide fuel cell system

Underground coal gasification (UCG) is a potential clean coal technology which converts coal into combustible gas in situ. The syngas produced from the UCG process using dry air contains more steam, tar and higher hydrocarbons compared to the conventional gasifiers. The focus of the present work is to use solid oxide fuel cells (SOFCs) to produce electrical power efficiently. To this end, a UCG system, based on air alone as the gasifying medium, is integrated with the SOFC system taking advantage of the high temperature exhaust from the latter to reform the syngas for producing hydrogen. Additional power is produced in the conventional way from a steam turbine making use of the unutilized fuel in SOFC. A detailed energy analysis of this system shows more than 4% thermal efficiency gain over an electricity generating system based entirely on a steam turbine cycle.