Coal seam gas desorption law and correction method for lost gas volume under compressed air sampling

LIU Xin; QI Ming; QI Liming

doi:10.11799/ce202602018

Abstract：Investigating the gas desorption law under compressed air sampling and exploring methods for determining lost gas volume are significant for improving the accuracy of coal seam gas content measurement.First,an experimental gas desorption apparatus was developed to simulate coal seam gas content measurement via compressed air sampling.Then,optimal experimental parameters for coal sample particle size and driving air pressure were determined through experiments,and the gas desorption law under different operating conditions for gas content measurement via compressed air sampling was systematically investigated.Finally,the intrinsic mechanism by which compressed air sampling promotes gas desorption from coal samples was analyzed,a correction method for estimating the lost gas volume under compressed air sampling was proposed,and this method was applied in field tests.The results show that compressed air sampling induces vibration,fragmentation,and dilution effects on gas-bearing coal samples,and the synergistic action of these three effects effectively promotes gas desorption.At the transition point between the initial air-driving desorption phase and the subsequent static atmospheric desorption phase,a distinct inflection point appears in the slope of the gas desorption curve.The relative error between the estimated lost gas volume,determined based on the subsequent static atmospheric desorption law,and the actual gas desorption amount during the initial air-driven phase was 24.2%-61.8%.After applying the correction method,this relative error was reduced to 1.5%-14.0%.Field tests indicate that the measured coal seam gas content increased by 1.13%-6.86%after correction compared to the uncorrected values.