A generalized method for calculation and prediction of vapour-liquid equilibria at high pressures

Abstract

A generalized method for prediction of vapour-liquid equilibria in hydrocarbon mixtures containing some nonhydrocarbon gases at high pressures has been developed following the approach of Chao and Seader (1961) and Lee et al. (1973). The method proposed is based on three equations: (1) a generalized equation of state for vapour phase calculations, (2) a generalized expression for the pure liquid fugacity coefficient suggested by Lee et al. (1973), and (3) an activity coefficient expression based on a surface modification of the regular solution model. The equations used contain only one partially generalized binary parameter, which has been evaluated from experimental K-value data. The method proposed has been tested by computing K-values and pressures in binary and multicomponent systems consisting of 13 hydrocarbons and three nonhydrocarbon gases. The results have shown that the proposed method can be applied over a wide range of conditions with a good degree of accuracy, which is comparable with that of more complicated methods.