Application of predictive equations of state in calculating natural gas phase envelopes and critical points

The phase equilibria and critical points of natural gas mixtures are calculated from two predictive equations of state. One of the predictive equations of state is introduced in this work. This model takes the advantages of a pressure–volume–temperature relationship that accurately describes the supercritical fugacity of methane and a group contribution method that suitably estimates the binary interaction parameters per pair of natural gas constituents. As a result, this model accurately predicts the vapor–liquid equilibria of natural gas mixtures. It also satisfactorily predicts the critical points of natural gas mixtures. Comparisons with experimental data and the other predictive method are presented.