Industrial & Engineering Chemistry Research, Vol.42, No.7, 1470-1477, 2003
Extension of the cubic-plus-association equation of state to glycol-water cross-associating systems
The application of the cubic-plus-association (CPA) equation of state has been extended to mixtures containing cross-associating compounds such as glycols and water. In this case, combining rules are required in the association term of CPA for the cross-association energy. and volume parameters. Different types of such combining rules have been suggested over the past years for association models such as statistical associating fluid theory. These are tested in this work for CPA in terms of their correlation and prediction capabilities for vapor-liquid equilibria of glycol-water systems. Comparisons with the Soave - Redlich- Kwong equation of state are also provided. It has been found that the arithmetic mean combining rule for the cross-association energy parameter and the geometric mean for the cross-association volume parameter provide overall the best results for cross-associating systems containing glycols and water. Moreover, preliminary results show that the CPA model can be used to predict multicomponent, multiphase equilibria for glycol-water-hydrocarbons based solely on binary interaction parameters.