ACCURATE PREDICTION OF THE THERMODYNAMIC PROPERTIES OF FLUIDS IN THE SYSTEM H2O-CO2-CH4-N2 UP TO 2000 K AND 100 KBAR FROM A CORRESPONDING STATES/ONE FLUID EQUATION OF STATE

Abstract

Previously, we reported an equation of state (EOS) modeling approach that successfully calculated the PVTX properties of supercritical fluid mixtures. The model is based on a corresponding states assumption applied to a highly accurate EOS for the reference CH4 system. The CH4 EOS was parameterized from 273 to 723 K and 1 to 3000 bar by using experimental PVT data. Molecular dynamics simulated PVT data were used to extend the parameterization in the CH4 system to 2000 K and 20 kbar. Mixing in the H2O-CO2-CH4-N2 system was successfully described by using a simple empirical mixing rule with only two temperature- and pressure-independent parameters for each binary mixture. Results indicated that PVTX properties in higher order systems could be reliably calculated without additional parameters. In this paper, by using experimental PVTX data in the H2O-CO2-CH4-N2 system that were not used in the EOS parameterization, we show that the model predictions are accurate from just above the critical temperature for the least volatile component to 2000 K and from 0 to 100 kbar. We also show that our modeling approach can be extended to reliably calculate supercritical phase equilibria and other thermodynamic properties, such as fugacity and enthalpy, under high-temperature and -pressure conditions.