Calculation of complex phase equilibria in the critical region of fluid mixture based on multi-fluid lattice equation of state

Quantitative correlation of critical loci and multiphase behaviors has rece ived considerable attention because the increased industrial importance of processes operating within the high-pressure region such as supercritical f luid extraction. However, in the critical region, classical thermodynamic m odels such as equations of state (EOS) frequently fail to correlate phase e quilibrium properties. Recently, the present authors proposed a new lattice -hole EOS based on the multi-fluid approximation of the nonrandom lattice t heory. The model requires only two molecular parameters reflecting size and interaction energy for a pure fluid and one additional interaction paramet ers for a binary mixture. In this work the reliable applicability of the EO S was demonstrated to various phase equilibria of complex mixtures in the c ritical region. Demonstration of the EOS was made to calculate multiphase b ehaviors such as solid-liquid-vapor (SLV) equilibria and critical loci of b inary complex mixtures at high pressure. For P-T, P-x, and T-p phase diagra ms tested, the model agrees well with experimental data.