A Method for the Measurement of Carbon Dioxide Desorption from Coal in the Elevated Pressure Range

Abstract

During the liberation of gas from a coal bed, the temperature of the system is decreased because desorption is an endothermic process and heat exchange with the surroundings is difficult. A method for measuring gas desorption in the elevated pressure range, enabling investigations under isothermal and quasi-adiabatic conditions, was described. The results of carbon dioxide desorption from Polish coal were presented. The study was carried out using different rates of decrease in the external gas pressure for different coal grain sizes. The non-isothermal desorption curves thus obtained were described using empirical equations. Extrapolation of the equation constants obtained enabled the desorption curves to be calculated for the limit of decrease in rate of the external gas pressure and of grain size. It was found experimentally that the dependence of the decrease in coal temperature on the amount of desorbed gas is linear provided that heat exchange with the surroundings is limited.