VLE calculations by applying a modified perturbed hard sphere EOS

Abstract

An equation of state (EOS), developed by using an improved expression of the coordination number model of square-well fluids, was applied in vapor-liquid equilibrium (VLE) calculations of real fluids and their mixtures. The EOS was written in a perturbed hard sphere form which had three parameters for each pure fluid. In this work, the EOS parameters for pure nonpolar and polar fluids were determined. It is demonstrated that the pure fluid properties were satisfactorily correlated and the EOS parameters showed reasonable physical significance. In the VLE calculations of fluid mixtures, the results were again satisfactory and were superior to those from commonly used cubic-type EOS. It is indicated that this modified perturbed hard sphere (MPHS) EOS yielded significantly better VLE calculation results on asymmetric systems of nonpolar + polar binary mixtures. The scattering of the binary interaction parameters of this MPHS-EOS was less than that from other EOSs. Ternary calculations by directly applying the binary parameters were also successful.