CALCULATION OF VAPOR-LIQUID EQUILIBRIUM OF MIXTURES FROM VAPOR PRESSURE EQUATION OF PURE COMPONENTS.

A new method is developed which calculated vapor-liquid equilibrium of mixtures directly from the vapor pressure equation of pure components, by using the two-fluid corresponding-state principle at atmospheric or reduced pressures. This method is as rigorous in theory as that based on the equation of state, and as simple in computation as the activity coefficient method. This method may be used satisfactorily in calculating vapor-liquid equilibrium when coordinated with the vdW and Wong mixing rules, but for only homogeneous systems. As an improvement, a simple energy-local-composition mixing rule is suggested. Tested in computing the vapor-liquid equilibria of 37 typical nonpolar-nonpolar, polar-polar, and polar-nonpolar binary systems, the proposed method, combined with the suggested rule, has been shown to be more accurate than the one-parameter Wilson equation, but slightly inferior to the two-parameter Wilson equation.