Molecular simulation study on competitive adsorption mechanism of gas power generation tail gas in coal micropore structure

To study the effect of coal micropore structure on the adsorption behavior of gas-fired power tail gas, low-temperature N2 adsorption, low-pressure CO2 adsorption, and molecular simulation were combined to analyze the competitive adsorption characteristics of tail-gas components in the micropores of Hongqingliang bituminous coal and the pore-size effect. The results show that the single-component adsorption capacity follows CO2 > O2 > N2, with the average CO2 adsorption being 2.12 mmol/g, about 1.5 and 1.7 times that of O2 and N2, respectively, and the same order for adsorption heat. In multicomponent competitive adsorption, CO2 still dominates; although O2 reduces CO2 adsorption by about 2.02%, the synergistic effect among tail-gas components increases the total adsorption by 5.74% compared with the N2–CO2 system, by 21.43% compared with the pure N2 system, and by 33.13% compared with a low-CO2 atmosphere. Pore-size analysis indicates that CO2 shows the strongest competitive advantage and selectivity in ultra-micropores, and this advantage gradually decreases with increasing pore size. These findings highlight the key role of ultra-micropore structure in enhancing adsorption competitiveness and energy differences, providing a theoretical basis for tail-gas resource utilization and CO2 sequestration.