Thermodynamic modelling of industrially important associating mixtures with a group-contribution equation of state

Abstract

The accurate prediction of phase equilibria of mixtures containing hydrocarbons and associating components such as water, alcohols and glycols is very important from an industrial perspective, since it ensures product quality and process safety, leading to a more effective design. To this purpose, a new model, that combines the Peng-Robinson equation of state coupled with the Universal Mixing Rules (UMR) with the association term based on Wertheim's perturbation theory is developed. The new model, referred as UMR-CPAPRU, is a predictive group contribution equation of state since it utilizes the UNIFAC activity coefficient model. UMR-CPAPRU leads to improved results in binary mixtures with a 5.4% average absolute relative deviation in bubble point pressure as compared to the 8.8% obtained by UMR-PRU, while it yields improved predictions over UMR-PRU for liquid-liquid equilibrium in alkane/water/methanol mixtures and dew points of wet natural gasses.