Conference article

Underground coal gasification (UCG) is a clean coal technology which converts coal into a combustible gas in situ without mining and without bringing up the ash contained in the coal. Thus; the attendant problems of coal washing; ash handling and disposal can be avoided. The combustible gas mixture; consisting primarily of hydrogen; methane; carbon monoxide--all of which are fuels for an solid oxide fuel cell (SOFC) system-- and carbon dioxide; can be fed to a battery of SOFC after gas cleaning to remove hydrogen sulphide and other impurities. A large portion; typically 50%; of the chemical energy contained in the product gas can be converted into electrical energy by the SOFC. The exhaust gases from the SOFC are typically at a temperature of the order of 600 to 800 deg C. Heat energy from these will be extracted to produce steam; part of which will be used for UCG and the rest will be sent for SOFC internal reforming and shifting reactions. The exhaust gases; consisting primarily of carbon dioxide and steam; will be finally fed through a condenser and will then be sent for compression and sequestration. Thus; the overall system envisaged makes use of oxygen-fed UCG and SOFC to generate electrical energy and an exhaust gas consisting primarily of carbon dioxide and the easily condensable steam which enables CO₂ sequestration. The overall integrated system can be divided into five units namely underground coal gasification; UCG product gas purification; electrical power generation from SOFC; heat recovery system and carbon sequestration unit. An energy analysis with heat integration of all the systems for a nominal 500 MWt will be discussed.

Underground coal gasification; Solid oxide fuel cell; Carbon sequestration; Heat integration