Phase behavior of multicomponent alkane mixtures and evaluation of predictive capacity for the PR and RKPR EoS's

Abstract

The RKPR EoS was developed in the past decade as a three-parameter model, with the intention to overcome some of the limitations of classic two-parameter cubic equations of state. More recently, parameter correlations were presented for alkanes and their mixtures, showing excellent capacity to predict the fluid phase behavior of binary mixtures up to the more asymmetric combinations and in wide ranges of temperature and pressure. In this work, different types of phase equilibrium data for multicomponent mixtures are considered, in order to see whether the good performance previously demonstrated for binary systems is also transferable to multicomponent mixtures like the ones typically encountered in synthetic fluids designed in the lab as model reservoir fluids. In the case of ternary systems with good availability of constant temperature and pressure data sets, the type and behavior of these Gibbs triangle diagrams are analyzed with reference to the general or global behavior of the system, based on pure compound saturation and binary critical lines, something we had not found in the literature preceding this work. The results and comparisons presented in this article allow concluding that RKPR2015 can be a useful tool with very good predictive capacity to describe the fluid phase equilibria of hydrocarbon mixtures. Advantages over the Peng-Robinson equation appear more clearly for the more asymmetric fluids, including synthetic gas condensates.