Critical points of multicomponent mixtures

Abstract

The criteria for critical points in multicomponent systems may be expressed in two simultaneous non-linear equations in the intensive variables of the critical phase. One of the two equations establishes the stability limit of the mixture. Computations have been performed in this work to predict the critical points in binary and multicomponent mixtures described by the Soave-Redlich-Kwong equation of state. A new procedure for evaluating the functions which appear in the non-linear equations is presented. The new procedure simplifies and permits the speeding up of the computation of critical points in multicomponent mixtures. For vapor- liquid critical points, an algorithm is proposed in which it is not necessary to provide initial guesses for either the temperature or the volume. The computational scheme presented has been used to predict the critical points of large systems. The technique was also used in the computation of the limit of stability by which liquid-liquid separations can be predicted. It is also capable of locating all the critical points existing in any multicomponent mixture.