LIQUID-LIQUID EQUILIBRIA PREDICTION USING THE AREA METHOD

The area method, based on the tangent plane criterion of Gibbs provide s a sufficient condition for determining the global minimum Gibbs ener gy of a system at fixed temperature and pressure. The dimensionless Gi bbs energy of mixing curve is integrated using a two-dimensional searc h technique to completely define the number and compositions of phases present in equilibrium. This work has set out to verify and expand on the possible uses of the area method, initially utilising a semi-empi rical liquid-phase model for liquid-liquid predictions only. Several r epresentative binary and ternary liquid-liquid mixtures have been pred icted using the area method, with some of these results presented here . The liquid-phase excess Gibbs energy modified UNIQUAC equation has b een used for all of the system tested with the interaction parameters fitted using the Nelder-Mead simplex algorithm. Overall, the method is shown to be robust in its ability to predict phase instability as acc urately as the phase model being used allows.