Solution Structure of Isoactivity Equations for Liquid–Liquid Equilibrium Calculations Using the Nonrandom Two-Liquid Model

Abstract

Calculation of the liquid-liquid equilibrium (LLE) based on an activity coefficient model is a common and significant problem in chemical thermodynamics. This is usually carried out by either minimizing the Gibbs free energy of the system coupled with the stability test (tangent plane distance criterion) or solving the isoactivity equations. While established, the stability test requires a very robust algorithm. By contrast, it is easy to solve the isoactivity equations; nevertheless, the solution strongly depends on the initial estimate. This study aims to investigate the structure of the solutions of the isoactivity equations for LLE systems in order to provide a calculation strategy that ..