含临界区流体混合物的统计缔合理论研究

含临界区流体混合物汽液平衡等热力学性质的研究是化工热力学的一个难题。本文用改进的统计缔合流体理论方程(SAFT-CP)^[1,2]结合范德华单流体混合规则(vdWl)计算了含临界点的二元混合物的汽液平衡。与原始的SAFT方程^[3/4]相比,SAFT-CP方程以非球形的硬体项作为参考流体,代替原来的硬球项,考虑了分子成链对色散作用的影响,对于极性流体,考虑了分子的偶极-偶极相互作用而忽略了缔合作用。本文计算的二元体系包括非极性-非极性体系：二氧化碳-丙烷、二氧化碳-丁烷和二氧化碳-戊烷,以及非极性～极性体系：硫化氢-戊烷、甲烷-丙酮和二氧化碳-甲醇。含临界点在内的计算结果与文献实验值符合很好,表明该方程适用于二元混合物含临界区的相平衡计算,具有广阔的应用前景。

A study on SAFT-CP for phase equilibria of fluid mixtures with a component near its critical point

The study on phase equilibria of fluid mixtures near the critical point is still a difficult problem in the area of chemical engineering thermodynamics. In this work, an equation modified from statistical associating fluid theory, called SAFT-CP, is used to calculate the vapor-liquid equilibria of binary mixtures, especially near the critical point, and the van der Wall one fluid mixing rule(vdWl ) is also used in calculation. Compared with the original SAFT equation, the new equation includes hard convex body as a reference fluid , instead of the hard sphere; the change of dispersion interaction because of the chain formation is considered and the dipole-dipole interaction of molecules is also considered while the associating interaction is neglected. Binary mixtures include non-polar-non-polar systems: carbon dioxide-propane, carbon dioxide-butane and carbon dioxide-pentane, and nonpolar-polar systems: sulfur hydrogen-pentane, methane-acetone and carbon dioxide-methanol. The calculation results are in good agreement with literature data including the critical region. The equation of state can be used in the processes with components near their critical points.