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受限条件下CO2-CH4体系的相平衡性质对化工工艺过程的设计具有非常重要的意义.采用Gibbs系综Monte Carlo模拟,对220K下CO2-CH4体系在主体相和受限狭缝中的相平衡性质进行了系统地研究.通过主体相模拟与实验结果比较,验证了流体分子势能参数的合理性;通过改变狭缝壁面原子的能量参数,研究了受限环境对CO2-CH4体系汽液相平衡性质的影响.与主体相相比,在硬壁狭缝中,CO2-CH4体系的露点压力增加,泡点压力降低,压力-组成相图变窄,且体系更容易达到超临界状态;在吸引狭缝中,随壁面原子能量参数的增大,CO2-CH4体系的压力-组成相图上移,临界点处CH4的摩尔分数减小,相图变窄.在体系汽液相总组成相同情况下,硬壁狭缝内体系的汽液相密度均比主体相中小;随壁面原子能量参数增大,气相密度变大、液相密度在CH4的摩尔分数较小时变大而当CH4的摩尔分数达到一定值后反而减小.在体系汽液相总组成相同时,受限环境下的汽化热比主体相的汽化热小且随壁面吸引势的增强越来越小;在主体相和硬壁狭缝中体系的汽化热随CH4含量的增加单调减小,而当壁面势能参数较大时汽化热随CH4含量增加先增大后减小.
Under the limited conditions, the phase equilibrium property of CO2-CH4 system is very important to the design of chemical process.Using Gibbs ensemble Monte Carlo simulation, the phase of CO2-CH4 system in main phase and confined slit at 220K The equilibrium properties of the CO2-CH4 system have been studied systematically.The comparison between the experimental results of the main phase and the experimental results verifies the rationality of the potential energy parameters of the fluid molecules. By changing the energy parameters of the atomic atoms in the slit wall, In the hard-wall slits, the dew-point pressure of CO2-CH4 system increases, the bubble point pressure decreases, the pressure-phase composition becomes narrower, and the system is easier to reach the supercritical state. In contrast, In the suction slot, the pressure-phase diagram of CO2-CH4 increases with the increase of atomic energy parameters, and the molar fraction of CH4 decreases and the phase diagram becomes narrower at the critical point. The vapor-liquid phase density of hard-wall slits is smaller than that of the main phase. With the increase of atomic energy parameters, the gas-phase density becomes larger and the liquid-phase density becomes larger when the molar fraction of CH4 is smaller. After the score reaches a certain value instead When the total vapor-liquid phase composition is the same, the heat of vaporization in the confined environment is smaller than the vaporization heat of the main phase and is getting smaller and smaller with the increase of the wall attraction potential. The vaporization of the system in the main phase and hard-wall slits The heat decreases monotonously with the increase of CH4 content, but increases with the increase of CH4 content when the wall potential parameter is larger.