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Tuning Cubic Equations of State for Supercritical Water Applications

Authors: Shyh-Ming Chern


Cubic equations of state (EoS), popular due to their simple mathematical form, ease of use, semi-theoretical nature and reasonable accuracy, are normally fitted to vapor-liquid equilibrium P-v-T data. As a result, they often show poor accuracy in the region near and above the critical point. In this study, the performance of the renowned Peng-Robinson (PR) and Patel-Teja (PT) EoS’s around the critical area has been examined against the P-v-T data of water. Both of them display large deviations at critical point. For instance, PR-EoS exhibits discrepancies as high as 47% for the specific volume, 28% for the enthalpy departure and 43% for the entropy departure at critical point. It is shown that incorporating P-v-T data of the supercritical region into the retuning of a cubic EoS can improve its performance at and above the critical point dramatically. Adopting a retuned acentric factor of 0.5491 instead of its genuine value of 0.344 for water in PR-EoS and a new F of 0.8854 instead of its original value of 0.6898 for water in PT-EoS reduces the discrepancies to about one third or less.

Keywords: Equation of state, EoS, supercritical water, SCW.

Digital Object Identifier (DOI):

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[1] M. Watanabe, H. Inomata, M. Osada, T. Sato, T. Adschiri, and K. Arai, "Catalytic Effects of NaOH and ZrO2 for Partial Oxidative Gasification of n-Hexadecane and Lignin in Supercritical Water,” Fuel, vol. 82, no. 5, pp. 545-552, 2003.
[2] Y. L. Kim, S. J. Chung, J. D. Kim, and J. S. Lim, "Uncatalyzed Partial Oxidation of P-xylene in Sub- and Supercritical Water,” Reaction Kinetics and Catalysis Letters, vol. 77, no. 1, pp. 35-42, 2002.
[3] Y. K. Park, J. T. Reaves, C. W. Curtis, and C. B. Roberts, "Conversion of Tire Waste using Subcritical and Supercritical Water Oxidation,” Journal of Elastomers and Plastics, vol. 31, no. 2, pp. 162-179, 1999.
[4] H. Tang, and K. Kitagawa, "Supercritical water gasification of biomass thermodynamic analysis with direct Gibbs free energy minimization,” Chemical Engineering Journal, vol. 106, pp. 261-267, 2005.
[5] D. Y. Peng, and D. B.Robinson, "New Two-Constant Equation of State,” Ind. & Eng. Chem. Fund., vol. 15, no. 1, pp. 59-64, 1976.
[6] N. C. Patel, and A. S. Teja, "A New Cubic Equation of State for Fluids and Fluid Mixtures,” Chem. Eng. Sci., vol. 37, no. 3, pp. 463-473, 1982.
[7] O. Redlich, and J. N. S. Kwong, "An Equation of State. Fugacities of Gaseous Solutions,” Chem. Rev., vol. 44, pp. 233-244, 1949.