Prediction of azeotropic behavior using equations of state

A shortcut method is developed to determine if an equation of state (EOS) i s capable of predicting azeotropes in binary systems and if the azeotrope m eets the critical gas-liquid equilibrium line. The method suggested allows an a priori prediction of subcritical azeotropes and an exact prediction of the azeotropic point (if any) at critical conditions. In addition, the app roach developed in this work avoids computation of critical Lines and simpl ifies phase equilibrium calculations for mixtures. The technique may be app lied to every EOS (and/or mixing rule model), provided that the PVT relatio n exhibits the van der Waals loop in subcritical ranges. Examples are prese nted using cubic EOS. (C) 1999 Elsevier Science B.V. All rights reserved.