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.