A SIMPLIFIED PERTURBED HARD CHAIN THEORY EQUATION OF STATE FOR PHASE-EQUILIBRIUM CALCULATIONS FOR POLAR FLUID MIXTURES

A simplified perturbed hard chain theory (PHCT) equation of state was proposed for vapor-liquid equilibrium calculations for highly non-ideal mixtures containing one or more polar components. In the proposed expression, Z involves three terms. The Z (repulsion) term is based on the expression of Carnahan-Starling for hard spheres. The Z (attractive non-polar) term follows the expression of Alder et al. but simplified as suggested by Gmehling, Liu and Prausnitz. In the formulation of the third term, the Z (polar) term, the multipolar expressions of Gubbins and Twu were adopted but much simplified. The adjustable parameters were evaluated for a variety of pure fluids, including water, acetone, alcohols, acids, esters and a number of hydrocarbons. Average absolute percent deviations in the calculated vapor pressures and saturated liquid densities for these substances are 0.67 and 1.68, respectively. The calculated vapor-liquid equilibrium values for non-polar-polar and polar-polar mixtures are in good agreement with the experimental values and are comparable with the results obtained from more elaborated versions of the PHCT equation. © 1990.