Development of Compound Specific Cohesion Function Relationship for SRK Equation of State

Chemical industries have undergone a paradigm shift in the designing process in the last decade, and most of them now rely on process simulators for designing and optimisation. Simulators are heavily dependent on thermodynamic models for the proper outcome of any simulation problem, in general, and phase equilibrium problem, in particular. Equations of state (EOS) have gained wide popularity due to their simplicity. Cubic equations of state (CEOS) can very accurately predict various thermophysical properties with minimum requirement of data. One of the key factors for obtaining accurate results from CEOS is its temperature dependency of cohesion factor relationship. In the present study, a new compound specific cohesion factor relationship is proposed for the Soave Redlich Kwong (SRK) EOS. The new model was compared with the original SRK EOS and its modified versions for accuracy in estimating vapour pressure for a large number of compounds representing various classes of families. It was found that the new relationship works better for almost all the families considered, especially, improving the vapour pressure prediction in the range of reduced temperature below 0.7.