Prediction of Vapour Liquid Equilibria for Binary Azeotropic Systems using Activity Coefficient Models

Distillation operations are inevitable in chemical and petrochemical process industries. Design of distillation equipment requires knowledge of precise vapor-liquid equilibrium data. Due to the complexity and expenses incurred to obtain the VLE data experimentally for those systems for which the data are not available, solution thermodynamics and phase equilibria serve as an important tool in theoretical VLE prediction. In the current investigation five binary azeotropes namely Acetone-water, Acetone-methanol, Ethanol-water, Ethanol-benzene, and Methanol-water are taken for study. The theoretical prediction of VLE for these systems were computed using activity coefficient models namely NRTL, UNIQUAC, UNIFAC and modified form of Florry - Huggins equations (SRS and TCRS). The parameters for the five systems of four models viz. NRTL, UNIQUAC, SRS and TCRS were computed using Newton Raphson technique. UNIFAC model was adopted using Analytical solution of group contribution (ASOG) method. The performance of these models are tested using thermodynamic consistency test and validation from experimental VLE from literature. It was seen that the Acetone - Water system follows TCRS model, Acetone - Methanol and Ethanol - Water and Methanol - Water systems follow UNIFAC model, whereas SRS model suits for the Ethanol - Benzene system with highest accuracies.