Application of the Anderko–Pitzer EoS to the calculation of thermodynamical properties of systems involved in the supercritical water oxidation process

Abstract

Corrosion and salt deposition are the main problems for the industrial development of supercritical water oxidation (SCWO). For solving these problems new reactors designs are being developed. The high costs of the research in SCWO make modeling an essential step in the development of new reactors. For getting reliable simulations of the reactors, it is necessary to possess accurate values of the thermodynamical properties of water and aqueous mixtures in the surroundings of the critical point of water, specially the heat capacities. Anderko–Pitzer (AP) EoS was especially developed for aqueous systems at high temperatures and pressures, and it is able to predict accurately volumetric properties and phase equilibrium. But for using this EoS is necessary to fit a large number of parameters, requiring extensive experimental data and making it time-consuming. In this work, parameters have been correlated in order to use the AP EoS to calculate volumetric properties and phase equilibrium of the system water–air. The properties calculated by AP EoS are compared to those calculated using the Peng–Robinson EoS with the translated volume correction, showing notable discrepancies in the heat capacity calculation. Heat capacity calculated by AP EoS is applied in a previously developed mathematical model made by the High Pressure Process Group (HPPG) of the University of Valladolid (UVa), that describes the behavior of the transpiring wall reactor (TWR) of the UVa. The model is able to reproduce the experimental results obtained with the reactor satisfactorily. Experimental temperature profile data are used to validate the predictions of the model.