【摘要】 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.更多还原

【Abstract】 The phase equilibrium properties for confined CO2-CH4 system are very important for the chemical engineering design.In this work,using Gibbs ensemble Monte Carlo simulations,the phase properties for bulk and confined CO2-CH4 system have been studied systematically at 220 K.The reliability of parameters for the inter-molecular interactions has been tested by comparing the simulation results with the experimental data.For CO2-CH4 system confined in the hard slit-pore,the dew point pressure is increased,the bubble point pressure is decreased and vapor-liquid coexistence area in pressure-composition phase diagram becomes narrower when compare with the corresponding bulk case.The system can more easily reach supercritical state.In the attractive pores,the pressure of CO2-CH4 system is increased,mole fraction of ethane at critical point is decreased and vapor-liquid coexistence area becomes narrower as the interaction strength between fluid and pore-wall becomes stronger.When the composition of system remains constant,the vapor and liquid densities of the system confined in hard-slit pores are smaller than that in the bulk case.The vaporization heat is decreased when compared with the bulk case,and it becomes smaller as the interaction between fluid and the pore-wall is strengthened.更多还原