A comparison of PC-SAFT and PR-Peneloux equations of state in predicting the compressibility factors of lean gas-carbon dioxide mixtures at high pressures

Abstract

Cubic equations of state have been long used as an accurate method of predicting the fluid phase behavior. Whereas these equations yield good predictions of fluid properties, due to their inherent limitations, they may not produce accurate enough values of the gas compressibility factor at high pressures. The PC-SAFT equation of state, on the other hand, calculates the gas compressibility factor using expressions that are more flexible. In this paper, the PC-SAFT and PR-Peneloux equations of state are compared for their ability to simulate the experimental gas compressibility factors of lean gas-carbon dioxide mixtures. To this end, the experimental compressibility factors of five different lean gas-carbon dioxide mixtures were predicted at high pressures. Two sets of simulations were performed. In the first set, the binary interaction coefficients fitted for the PR equation of state were used in both models. In the second set of simulations, the interaction coefficients were reasonably tuned, so that the experimental data were best described by the models. For both sets, the PC-SAFT equation predicted more accurate compressibility factors than the PR-Peneloux equation. In fact, for the tuned PC-SAFT equation, the prediction accuracy was comparable to the accuracy of the experimental data.