Investigation of an Adsorption Model of Wet Coal That Considers Coal Seam Gas Pressure and Temperature Effects

Abstract

To investigate the effects of gas pressure and temperature in different coal seams on the adsorption behavior of water-bearing coal, an equilibrium constant was introduced to combine the L-F model and dual-L model to construct an excess adsorption model that accounts for changes in the volume and density of the adsorption phase. The results showed that the newly developed model effectively described the gas adsorption behavior of coal under varying temperature and moisture conditions. In the initial stage of gas pressure increase, the methane molecules rapidly occupied the micropore adsorption sites, leading to a rapid increase in adsorption phase density. As the pressure increased, the adsorption sites gradually approached saturation, causing the increase in the adsorption phase density to slow. As the temperature increased, the kinetic energy of the gas molecules increased, leading to desorption and a further reduction in adsorption phase density. Moreover, a positive correlation was observed between excess adsorption and adsorption phase density, with significant temperature sensitivity. At higher adsorption phase densities, an increase in temperature led to a decrease in excess adsorption. Compared with the L-F model and dual-L model, the newly developed adsorption model demonstrated significant advantages in terms of fitting accuracy and physical significance, thus providing more accurate predictions of coal adsorption capacity under the combined effects of gas pressure, temperature, and moisture in coal seams.