Gas desorption characteristics of the high-rank intact coal and fractured coal

Abstract The objective of this work is to study the gas desorptioncharacteristics of the high-rank intact coaland fractured coal. The gas adsorption, mercury porosimetryand gas desorptionexperiments were carried out in this study. Then, the theories of thermodynamics, diffusion mechanism and desorptionkinetics were used to estimate the gas desorptioncharacteristics. The results of gas adsorption experiments show that the initial isostericadsorption heat of the intact coalis greater than that of the fractured coal, indicating that the gas molecules desorb more easily from fractured coalthan intact coal. Using the mercury porosimetry, we find that the diffusion channels of fractured coalare more developed than those of intact coal. The difficult diffusion form dominates in the intact coalduring the gas diffusing, while the easy diffusion form dominates in the fractured coal. The results of gas desorptionexperiments show that the initial gas desorptionvolume and velocity of the fractured coalare both greater than those of the intact coal. Using the Fick diffusion law, the study calculates the gas diffusion coefficients of the intact coaland fractured coal. The diffusion coefficients of the fractured coalare 2 times and 10 times greater than those of the intact coalat the time of 0–120 and 0–10 min, respectively.