Are safe results obtained when SAFT equations are applied to ordinary chemicals? Part 2: Study of solid-liquid equilibria in binary systems

摘要

In a previous work, some irregular behaviours of the PC-SAFT EoS - and more generally of SAFT-type EoS - were pointed out for pure components at low temperatures. In particular, it was shown that for pure fluids at a fixed temperature and pressure, these equations of state were likely to exhibit up to five molar volumes, thus leading to the simultaneous existence of pseudo liquid-liquid and liquid-vapour phase equilibria at a same temperature. In this work, low-temperature calculations are performed using the PC-SAFT EoS which is combined with a fugacity model for the solid phase in order to predict solid-liquid phase equilibria. It is shown that when varying the binary-interaction parameter of the PC-SAFT equation, non-feasible phase diagrams may be calculated including for instance, the presence of a liquid-liquid azeotrope, of a liquid-liquid-solid-solid four-phase equilibrium or the simultaneous existence of several eutectic points.