东曲矿8号煤CO_(2)和CH_(4)竞争吸附特性分子模拟研究

Molecular simulation study on competitive adsorption characteristics of CO_(2) and CH_(4) for 8^(#) coal in Dongqu Mine

深入了解煤层中CO_(2)和CH_(4)竞争吸附的微观机制是实现CO_(2)驱替甲烷开采(CO_(2)-ECBM)的关键,基于东曲矿8号煤的大分子结构模型开展了CO_(2)和CH_(4)的单组分与双组分竞争吸附研究。结果表明:单组分吸附中CO_(2)的吸附量显著大于CH_(4)的吸附量,双组分竞争吸附中的总吸附量随着CO_(2)的摩尔分数的增大而增大;不同摩尔比条件下的双组分吸附中CO_(2)对CH_(4)的选择性吸附系数始终大于1,且CO_(2)摩尔分数越大,选择性吸附系数越小;相互作用能随着吸附量的增大而显著增大,CO_(2)吸附体系中较大的静电能促进了煤大分子对CO_(2)吸附,因此,不同摩尔比体系的相互作用能随着CO_(2)摩尔分数的增加而显著增加;单组分吸附中CO_(2)的吸附势大于CH_(4)的吸附势,双组分竞争吸附中CO_(2)的吸附势随着CO_(2)摩尔比的增加而增加,而CH_(4)的吸附势随着CO_(2)摩尔比的增加而降低,该结果与吸附选择性分析的结果一致。

A deep understanding of the micro mechanism of competitive adsorption of CO_(2) and CH_(4) in coal seams is crucial for achieving CO_(2) displacing methane extraction(CO_(2)-ECBM).Based on the macromolecular structure model of Dongqu Mine No.8 coal,a study was conducted on the competitive adsorption of single and dual components of CO_(2) and CH_(4).The results indicate that the adsorption capacity of CO_(2) in single component adsorption is significantly greater than that of CH_(4),and the total adsorption capacity in dual component competitive adsorption increases with the increase of CO_(2) mole fraction;the selective adsorption coefficient of CO_(2) for CH_(4) in dual component adsorption under different molar ratios is always greater than 1,and the larger the molar fraction of CO_(2),the smaller the selective adsorption coefficient;the interaction energy significantly increases with the increase of adsorption capacity.The larger electrostatic energy in the CO_(2) adsorption system promotes the adsorption of CO_(2) by coal macromolecules.Therefore,the interaction energy of different molar ratio systems increases significantly with the increase of CO_(2) mole fraction;the adsorption potential of CO_(2) in single component adsorption is greater than that of CH_(4),while the adsorption potential of CO_(2) in dual component competitive adsorption increases with the increase of CO_(2) molar ratio,while the adsorption potential of CH_(4) decreases with the increase of CO_(2) molar ratio.This result is consistent with the results of adsorption selectivity analysis.