Modelling the environmental impact of underground coal gasification

Underground coal gasification has the potential to access vast energy resources in a safe, economical and efficient manner, with many environmental advantages over traditional methods. Previous trials have led to local environmental issues concerning surface subsidence, groundwater contamination and water table depletion. The risk of such issues can be greatly reduced however, through a greater understanding of the coupled thermal, mechanical and hydraulic phenomena involved. Such an understanding allows operators to design gasifiers to reduce or completely eliminate these risks. Numerical simulations provide a cost effective means of investigating these issues. This paper uses the commercially available 2D discrete element code UDEC to model these effects. Initial results show agreement with field trial experience and previous predictions, despite a relative lack of available validation data. Future modelling aims to investigate the influence of a number of design decisions on environmental performance to produce guidelines for future operations.