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Predicting the phase equilibria of synthetic petroleum fluids with the PPR78 approach



The PPR78 approach is a group contribution-based thermodynamic model which combines at constant packing fraction the Peng–Robinson equation of state and a Van Laar-type gE model. This article demonstrates that, using classical mixing rules (linear on b and quadratic on a), the PPR78 model may also be seen as a group contribution method for the estimation of the temperature-dependent kij of the widely used PR EoS. Our model is endowed of 15 groups and it is possible to predict the kij for any mixture containing alkanes, aromatics, naphthenes, CO2, N2, H2S, and mercaptans. This study exhibits the capability of this approach to predict the phase behavior of synthetic petroleum fluids containing components of different volatilities. The many comparisons between calculated and experimental data on natural gases, crude oils, and gas condensates allow concluding that the PPR78 approach is a successful model for phase equilibria calculations of this kind of mixtures. © 2010 American Institute of Chemical Engineers AIChE J, 2010