Evaluating the phase equilibria of liquid water + natural gas mixtures using cubic equations of state with asymmetric mixing rules

Based on a previously developed liquid–liquid mixing rule we present a modified and robust mixing rule for accurate prediction of water content of natural gas mixtures and the natural gas solubility in liquid water phase. The non-density dependent mixing rule (NDD) and the new mixing rule are incorporated into the Peng–Robinson (PR), Soave–Redlich–Kwong (SRK), and Nasrifar–Bolland (NB) equations of state to investigate their accuracies in estimating the water content of the gas phase as well as the gas solubility in the aqueous phase. For each binary system water + hydrocarbon, water + carbon dioxide, water + hydrogen sulfide, and water + nitrogen, three binary interaction parameters are required to describe the gas–liquid water equilibria. In this work, experimental data from literature were used to tune the parameters. The results are in good agreement with experimental data, demonstrating the reliability of the new mixing rule and the thermodynamic approach used in this work.