1 Department of Chemical and Biochemical Engineering, Technical University of Denmark2 Center for Phase Equilibria and Separation Processes, Department of Chemical and Biochemical Engineering, Technical University of Denmark3 Center for Energy Resources Engineering, Center, Technical University of Denmark
The cubic-plus-association (CPA) equation of state (EoS) is applied, using different combining rules, to vapor-liquid equilibria (VLE) and liquid-liquid equilibria (LLE) of alcohol-water systems. It is demonstrated that the Elliott combining rule (ECR) with a common temperature-independent interaction parameter provides very adequate VLE correlations over extended temperature and pressure ranges, yielding also a very satisfactory description of the azeotropic behavior. LLE of heavy alcohol-water systems is best described with the CR-1 combining rule and a single interaction parameter. Satisfactory predictions of multicomponent, multiphase equilibria of water-alcohol-alkane systems at various conditions are achieved using solely one interaction parameter per binary. A study of the dominant binary systems for the prediction of the multicomponent systems demonstrates that both the binary alcohol-water and alcohol-hydrocarbon systems are crucial for the prediction of the partition coefficients of alcohols. Finally, the CPA EoS combined with a model for the solid-complex formation can successfully describe solid-liquid equilibria of glycol/methanol-water systems including the description of the solid-complex phase, which is known to exist at intermediate concentrations.
Industrial and Engineering Chemistry Research, 2005, Vol 44, Issue 10, p. 3823-3833