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

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.