Phase behavior of the CO2–H2O system at temperatures of 273–623 K and pressures of 0.1–200 MPa using Peng-Robinson-Stryjek-Vera equation of state with a modified Wong-Sandler mixing rule: An extension to the CO2–CH4–H2O system

Abstract

We modified the binary interaction parameter in Wong-Sandler mixing rule for cubic EOS as a two-parameter linear function of composition. We then incorporated the Non-Random-Two-Liquid excess Gibbs energy model into the modified Wong-Sandler mixing rule to correlate the phase boundaries of the CO2–H2O system through the ϕ−ϕ approach by using Peng–Robinson-Stryjek-Vera equation of state. The proposed EOS/Gex model has four adjustable temperature-dependent parameters for polar molecules; and it can be reduced smoothly to the van der Waal one-fluid mixing rule with only one binary interaction parameter for hydrocarbon systems. An excellent result was obtained when compared the modeling results with a large amount of the vapor–liquid equilibria experimental data (more than 1300 experimental data points located in a P-T region of 273–623 K and 0.1–200 MPa) for the CO2–H2O system. The average absolute deviations (AAD%) of modeling results from experimental data (mutual solubilities of CO2 and H2O) are less than 7.5% for both phases. In addition, the proposed model can be easily extended to a multi-component system on condition that the binary interaction parameters of each binary pair in the multi-component system are known. We provided a calculation example for the ternary CO2–CH4–H2O system and found that the modeling result agrees very well with experimental data for this ternary system.