NON CUBIC EQUATION OF STATE FOR PHASE EQUILIBRIUM CALCULATIONS
Tong Zhangfa Zhao Chuanjun and Lu Huanzhang Department of Chemical Engineering, Beijing Institute of Chemical Technology, Beijing 100029, China
A new non-cubic equation of state is proposed for calculation of the thermodynamic properties of nonpolar and polar fluids and their mixtures, including saturated vapor pressure, saturated liquid volume, saturated vapor volume, heats of vaporization and vapor-liquid equilibria. The new equation is derived from the generalized van der Waals partition function in which the repulsive terms are expressed with the Carnahan and Starling equation for hard spheres, and the attractive terms are made up of the dispersive energy and the chemical association energy. The rules of dependence of parameters α and σ and on temperature are considered broadly so that the new equation yields good agreement with experimental saturated properties of 20 nonpolar and 27 polar fluids in the range of reduced temperatures of 0.5 to 1.0. The new equation with parameters group-contributed generally gives satisfactory predictions on saturated properties. Correlations of vapor-liquid equilibrium data for alcohol-containing systems by using van der Waals one-fluid mixing rules prove that the new equation is superior to the M-PR equation of state.
【CateGory Index】： O642