New article about thermodynamic models for carbon dioxide/water mixtures

Our paper entitled: Thermodynamic models to accurately describe the PVTxy-behavior of water / carbon dioxide mixtures has been accepted for publication in Fluid Phase Equilibria. In the work, we present a comprehensive comparison of thermodynamic models for describing their PVTxy behavior, i.e. densities and phase compositions of mixtures with water and carbon dioxide. The most accurate experimental data in the temperature range 273–478 K and at pressures below were selected after a critical data evaluation. The most reliable phase equilibrium data are used to fit the binary interaction parameters of a wide range of thermodynamic models: cubic equations of state (EoS) with quadratic/Wong–Sandler/Huron–Vidal mixing rules, CPA, PC-SAFT and PCP-SAFT with different association schemes, and corresponding states models with various reference fluids. We tested the predictive ability of the models by comparing to data outside of the region used in the parameter-fit. All of the thermodynamic models were fitted with the same experimental data and compared on the same basis, facilitating a general discussion about their strengths and weaknesses. As a benchmark for the performance of the models, we compare with the performance of two multiparameter EoS: GERG-2008 and EoS-CG. At least three fitting parameters are needed to represent the PVTxy behavior of CO2/H2O mixtures within an accuracy of 10%. By including a fourth parameter, it is possible to significantly improve the accuracy for phase compositions, where the Peng–Robinson cubic EoS with the Huron–Vidal mixing rule and volume shift gives the best results with an average accuracy of 4.5% and 2.8% for phase compositions and densities respectively. In comparison, the most accurate multiparameter EoS, EoS-CG, exhibits an average accuracy of 8.0% and 0.6% for phase compositions and densities respectively. The work presented in the paper is part of an ongoing effort to improve the precision in describing the thermo-physical properties of mixtures important for CO2 capture, transport and storage. The work was performed in in collaboration with Ailo Aasen, Morten Hammer, Geir Skaugen and Jana P. Jakobsen from SINTEF Energy Research and NTNU (Ailo, Jana and me work at both places).

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