Determination of the Gas Content of Coal

In coal mining the gas content of coal is required primarily to quantify the gassiness of coal for safe mining, but also to quantify potential greenhouse gas emissions from mining. In Australia the gas content of coal is determined using a direct method, whereby the gas desorbed from solid or crushed coal is collected and the volume and composition of the desorbed gas are measured. The determination of gas content is associated with errors of measurement of the volume and composition of the gas. It is undertaken at several stages of gas desorption. Relative errors and resulting uncertainties of determination are more significant for the estimation of lost gas during drilling and gas remaining in coal following the completion of the standard stages of measurements, whence the rate of gas desorption is significantly reduced. This paper discusses the current Australian method and potential errors and uncertainty associated with this method. A new method of measurement for measurement of remaining gas in coal following the completion of standard gas content testing is also suggested. The new method should allow the release of almost all remaining gas in powdered coal following the last stage of standard gas content testing.