Comparing Cohesion Factor Models of SRK Equation of State for Predicting Boiling Points and Heat of Vaporisation

Abstract

Use of any process simulator to predict phase equilibrium properties require proper selection of a thermodynamic model. Equations of State have been the choice of process engineers. Equations of state have to be accompanied by a proper cohesion/alpha function for accurate results. Cohesion/alpha function represents the dependency of attractive term of cubic equation of state on temperature. Any model for cohesion factor can be judged by the accuracy with which it predicts vapour pressure. However, accurate predictions of various other properties are also important. In the present work boiling point and heat of vaporisation were predicted. Equation of state approach for predicting these properties requires only critical parameters. Eleven cohesion factor models of SRK Equation of State available in the literature were compared for the predication of boiling point and heat of vaporisation of more than 300 compounds. The compounds were selected to cover wide range of applicability and are comprising of 29 families. It was found that the cohesion factor model following SRK type cohesion factor models performed better compared to others. Even compound specific models were at par with the generalised models. It was also found that some cohesion factor models were suitable for specific class of families.