CO2 Sequestration Potential Competitive with H2O and N2 in Abandoned Coal Mines Based on Molecular Modeling

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To facilitate the local recycling of coal mine waste gas and investigate multi-component gas adsorption under high pressure conditions, this study develops a coal nanopore model using molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) methods and simulates the adsorption behavior of coal mine waste gas components (CO2, H2O, N2) under varying pressure levels and gas molar ratios at 353.15 K. We evaluated the adsorption capacity and selectivity for both single-component and multi-component gases, quantifying adsorption interactions through adsorption heat, interaction energy, and energy distribution. The simulation results revealed that the contribution of the three gases to the total adsorption amount followed the order: H2O > CO2 > N2. The selective adsorption coefficient of a gas exhibits an inverse correlation with its molar volume ratio. Isothermal heat adsorption of gases in coal was positive, decreasing sharply with increasing pressure before leveling off. Electrostatic interactions dominated CO2 and H2O adsorption, while van der Waals forces governed N2 adsorption. As the gas mixture complexity increased, the overlap of energy distribution curves pronounced, highlighting competitive adsorption behavior. These findings offer a theoretical foundation for optimizing coal mine waste gas treatment and CO2 sequestration technologies.