MONTE-CARLO SIMULATION OF HIGH-PRESSURE PHASE-EQUILIBRIA IN AQUEOUS SYSTEMS

We have used Gibbs ensemble and histogram-reweighting Monte Carlo tech niques to obtain the phase behavior of water and aqueous mixtures at h igh pressures. These calculations are relevant for the design of high- pressure separation processes, such as supercritical fluid extraction and supercritical water oxidation. In particular, we have obtained the phase behavior of several simple point charge models of water, as wel l as polarizable versions of these models. None of the models studied reproduce the experimentally observed phase behavior and critical para meters of water. The binary mixture water/carbon dioxide at high press ures has also been studied. Good agreement for this mixture has been o btained without use of any adjustable parameters for the mixture inter actions, thus suggesting that the predictive power of molecular-based methods is greater than that of purely phenomenological approaches, ev en when using imperfect pure component intermolecular potential models . (C) 1998 Elsevier Science B.V. All rights reserved.