Underground coal gasification waste heat recovery - by injecting water and extracting steam for district heating or power generation

摘要

Waste heat produced during an in-situ gasification of coal seams which has not been utilized for gasification is recovered by pumping water into the worked out areas, pref. through boreholes which have been laid off after they have been used for the gasification circuit. The steam produced is extracted through boreholes. The water is, in the case of inclined coal seams, introduced at the deepest point. If the gasification is carried out at high pressures (40 bar), the water is introduced at the same pressure. This produces steam of high pressure and quality. In the case of thinner coal seams, it may be the decisive factor in making underground gasification profitable.