Retention and release of methane in underground coal workings |
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| Authors: | Satya Harpalani Malcolm J Mcpherson |
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| Institution: | (1) Department of Mining and Geological Engineering, University of Arizona, 85721 Tucson, Arizona, USA;(2) Department of Materials Science and Mineral Engineering, University of California, 94720 Berkeley, California, USA |
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| Abstract: | Summary During an investigation to study the gas flow characteristics of coal, adsorption and desorption rates of methane from powdered coal samples were measured. From adsorption tests, it was found that the capacity of coal to hold methane varies significantly with gas pressure. For pressures up to 4.14 MPa (600 psi) the amount of gas adsorbed was still rising and monomolecular saturation was not reached. Results of desorption tests were used to test three equations suggested by previous investigators to measure the quantity of desorbed gas. It was confirmed that no single equation would define adequately the complete desorption process. Changes of regime appeared to exist at desorption times of 100 s and, to a lesser extent, 1000 s following the initial release of ambient gas pressure. A hypothesis was advanced that initial flow was inhibited or choked by an efflux of desorbing gas molecules. This was followed by a short transitional period and a longer term regime of free flow with reduced resistance offered by the flow paths. |
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| Keywords: | Coal methane adsorption desorption |
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