Homotopy continuation based prediction of azeotropy in binary and multicomponent mixtures through equations of state

Abstract

A method to compute all the azeotropes in homogeneous binary and multicomponent mixtures for entire two-phase pressure range is described. The method is based on solving the necessary condition of azeotropy for all the possible solutions through homotopy continuation approach. The method is mathematically guaranteed to predict all the possible azeotropes and is in close agreement with experimental data for any equation of state that can adequately represent the phase behavior. Both vapor and liquid phase non-idealities are incorporated using fugacity coefficients from the Peng–Robinson–Stryjek–Vera equation of state with the Wong–Sandler mixing rules. The method is also capable of predicting the value of bifurcation pressure where homogeneous azeotropes will appear or disappear. Polyazeotropy in binary mixtures is a singular case of vapor-liquid equilibrium and can also be computed by solving the necessary condition of azeotropy in binary mixtures for multiple solutions through homotopy continuation based approach. The approach can also systematically search the entire two-phase pressure range for the appearance, disappearance and persistence of azeotropy and polyazeotropy in binary and multicomponent mixtures.