Thermodynamics Models for Phase Equilibria at High Pressure

Generally Separation techniques are one of the most important steps in the majority of chemical processes. However their performance depends greatly on the operating conditions of pressure, temperature, etc. which are not experimentally always available or easy to measure. Therefore it is important to have thermodynamics models capable to determine these conditions and particularly at phase equilibrium. Many research works have been developed or are under development concerning the modelling of these phase equilibrium, but the majority consider the cases of low or moderate pressures, comparatively to the case of high pressures that is generally unavoidable but complex enough. Therefore this work aims to examine and test different thermodynamic models for certain cases of phase equilibrium. This study is also an opportunity to show the importance of the choice of the most appropriate equation of state equation in association with the most suitable mixing rule, for the given operating conditions. Finally this work can be seen as a basis for considering more deeply processes which use supercritical fluids, particularly supercritical extraction which is widely used nowadays in the industry.