Modification of Peng-Robinson equation of state for saturated vapour-liquid equilibrium

Abstract

The Peng-Robinson [l] modification of the Redlich-Kwong [2] equation of state has in recent years been widely used in chemical engineering [3] for predicting the vapour-liquid equilibria and volumetric properties. In this work, the temperature-dependent attractive force term of the Peng-Robinson equation is modified by a new proposed reduced temperature term, T*, introduced by Lielmezs et al. [4]. This term is associated with the phenomenological scaling and renormalization group theory by Griffiths [5], Kadanoff [6], Wegner [7] and Wilson and Kogut [8]. This reduced temperature term, T*, is expressed as a function of temperature T, the normal boiling point T the critical point temperature T, and two substance-dependent constilts p and q, derived from saturated vapour-liquid equilibrium data. The proposed modification predicts the saturated liquid-vapour equilibrium states for all types of liquids accurately over the entire liquid range from the triple point up to the critical point. The presented correlation is tested by comparing the RMSS error values against the RMS% error values obtained by using Peng-Robinson [l], Lielmezs et al. [4] and Soave [13] modifications of the Redlich-Kwong equation.