Research on adsorption characteristics of H2S, CH4, N2 in coal based on Monte Carlo method

In order to study the adsorption characteristics of H2S, CH4 and N2 by coal under different conditions, the new macromolecular structure model of Dongqu No. 2 was constructed, and the grand canonical Monte Carlo (GCMC) method was used to simulate the adsorption process of three types of gases in coal. The dependence of adsorption capacity of coal on its temperature, pressure and moisture content was analyzed. The results show that with the increase of pressure and temperature, adsorption isotherms of all the three gases follow Langmuir model. For pressure greater than 2 MPa, the influence of temperature on adsorption capacity was greater than that of pressure. With rise in temperature, the decrease in rate of H2S adsorption was least and drops in the heat of adsorption of H2S most. This indicates that the adsorption of H2S on coal is more stable than those of CH4 and N2. As the water content of coal increased, its adsorption capacity for the present three gases decreased linearly, and the capacity for H2S (1.77 mmol/g) changed the most. The reduction of free volume linearly and preferential occupation of adsorption sites by water molecules are the main reasons for the highest change in the adsorbed amount of H2S gas.