Molecular modeling of CO₂ affecting competitive adsorption within anthracite coal

This study aimed to investigate the adsorption properties of CO₂, CH₄, and N₂ on anthracite. A molecular structural model of anthracite (C₂₀₈H₁₆₂O₁₂N₄) was established. Simulations were performed for the adsorption properties of single-component and multi-component gases at various temperatures, pressures, and gas ratios. The grand canonical ensemble Monte Carlo approach based on molecular mechanics and dynamics theories was used to perform the simulations. The results showed that the isotherms for the adsorption of single-component CO₂, CH₄, and N₂ followed the Langmuir formula, and the CO₂ adsorption isotherm growth gradient was negatively correlated with pressure but positively correlated with temperature. When the CO₂ injection in the gas mixture was increased from 1 to 3% for the multi-component gas adsorption, the proportion of CO₂ adsorption rose from 1/3 to 2/3, indicating that CO₂ has a competing-adsorption advantage. The CO₂ adsorption decreased faster with increasing temperature, indicating that the sensitivity of CO₂ to temperature is stronger than that of CH₄ and N₂. The adsorbent potential energies of CO₂, CH₄, and N₂ diminished with rising temperature in the following order: CO₂ < CH₄ < N₂.