Modeling the equilibrium of two and three-phase systems including water, alcohol, and hydrocarbons with CPA EOS and its improvement for electrolytic systems by Debye-Huckel equation

Calculation of the phase equilibrium of hydrocarbons in the presence of electrolyte solutions is one of the most important and practical topics in chemical and petroleum engineering. The aim is to obtain an improved thermodynamic model that can predict the phase behavior of hydrocarbons along with electrolyte solution and alcohol with a good approximation. In this work, various equilibrium data published by previous researchers were collected, and then phase behavior of different systems including water, alcohol, and hydrocarbons was modeled using cubic plus association equation of state. Moreover, modified cubic plus association equation of state by Debye-Huckel equation was utilized for the prediction of the phase behavior of different systems containing salt. The results showed, for systems without electrolyte components, the cubic plus association equation of state predicts the phase behavior of these mixtures very well and the absolute average deviation value in these mixtures was between 1 and 10% for different systems. In recent decades, several equations of state have been proposed to predict the behavior of electrolyte mixture but, to the best of our knowledge, they did not consider all four components (hydrocarbon, water, alcohol, and salt) at the same time. In this research, an equation of state was presented to predict the phase behavior of systems that simultaneously contain hydrocarbons, water, alcohol, and salt in a mixture that considers both hydrogen bonds and ion interactions. The electrolytic cubic plus association equation is an equation that considers the effect of hydrogen bonds between different components as well as the effect of forces between existing ions. The results obtained for predicting electrolyte systems using the electrolytic cubic plus association equation showed that this equation can predict the phase behavior of these mixtures satisfactorily. The error value obtained for electrolytic systems and tangible components was between 1 and 12%. •Collecting various equilibrium data of different systems including water, alcohol, hydrocarbons, and salt.•Utilizing modified CPA EOS by Debye-Huckel equation for prediction of phase behavior of different systems containing salt.•Very well prediction of the phase behavior of systems without electrolyte components utilizing the CPA EOS.•Obtaining satisfactory results for predicting phase behavior electrolyte systems using the e-CPA equation.