Molecular simulation of adsorption thermodynamic properties of CH4 and CO2 at different temperature and moisture content conditions

In order to further clarify the adsorption thermodynamic characteristics of CH4 and CO2 in coal, the giant canonical ensemble Monte Carlo method was used to simulate the adsorption behavior of CH4 and CO2 in coal at different temperatures and different moisture content. The results show that the adsorption capacity of CH4 and CO2 in coal molecules decreases with the increasing temperature and moisture content. By comparing the adsorption amounts of the two components, it is found that both high temperature and the presence of water molecules are not conducive to displace CH4 by CO2; the average adsorption heat of CH4 is negatively correlated with temperature and water content, and average adsorption heat of CO2 has a negative correlation with temperature and a positive correlation with water content. Water molecules are more inclined to react with CO2; the overall adsorption potential of CH4 and CO2 is negatively correlated with temperature and moisture content. When the pressure is low, the adsorption potential of CO2 increases slightly with the increasing of temperature; the adsorption entropy of CH4 and CO2 increases with the increasing of temperature and decreases with the increasing of moisture content. The influence of water on CO2 is stronger than CH4. When two components are injected, the existence of water molecules makes the whole system more stable, which is not conducive to CH4 output.