Carbon dioxide-water phase equilibria results from the Wong-Sandler combining rules

A model based upon the Peng-Robinson equation of state with the Wong-Sandler mixture combining rule (W-S MCR) can correlate phase equilibria in CO2 + H2O. The W-S MCR requires two energy parameters for liquid behavior and one interaction parameter for gas behavior, kij. In this paper, we present expressions for the energy parameters which cover a wide temperature range, and we use a new procedure to obtain kij by relating it to experimental cross second virial coefficients, Bij. The three-phase pressures calculated for this system using our proposed model agree with the experimental data within a fraction of 1 bar. The correlated phase behavior of CO2 + H2O appears to be accurate over the ranges 1 – 1000 bar and 298.15–623.15 K. The proposed model also confirms the advantage of using the W-S MCR for phase equilibrium calculations.