Modeling of multiphase liquid equilibria for multicomponent mixtures

A computational procedure to correlate multicomponent, multiphase liquid equilibria in terms of excess Gibbs energy models is described. This includes an efficient hybrid algorithm for solving the multiphase liquid equilibria flash problem which is an extension of the approach proposed by Ammar and Renon to perform vapor-liquid flash calculations. The algorithms presented in this work for the calculation of multiphase liquid equilibria, the thermodynamic stability test based on the tangent plan criterion, as described by Michelsen, and the methods for estimation of interaction parameters of the NRTL, UNIQUAC, and extended UNIQUAC models, were tested on the representation of experimental two- and three-liquid phase equilibrium data of ternary and quaternary mixtures. Agreement between calculated and measured equilibrium data was excellent for most systems studied.