An Integrated Model for Underground Coal Gasification

Abstract

Abstract Underground coal gasification receives renewed interest in both Western and Eastern Europe because of the vast amounts of otherwise unminable coal deposits that occur on the European continent. A field test is currently being carried out in Spain. Other countries in Europe show interest in this method of utilizing coal resources. In this study we present a model that describes the development of an underground coal gasifier. Both permeable bed and channel surface gasification are combined with thermo-mechanical failure of both coal and overlying rock. By this combination the model predicts the channel development and thus the sweep efficiency of the gasification process. The model consists of two modules: the first module solves the flow equations in the entire flow domain. The second module selects a block of coal for gasification and a block of coal and/or rock for thermo-mechanically induced spalling. Other features such as ash content and heterogeneity are included in the model as well. Model calculations show that the ash content of the coal and the coal and rock spall rate determine largely the sweep efficiency of the gasification process. The model is used for field test evaluation purposes and can be used for extrapolation of the test results to other situations, e.g. the deep lying thin coal layers that occur in Northwestern Europe.