CALCULATION OF MULTIPHASE EQUILIBRIA USING THE EQUAL-AREA RULE WITH APPLICATION TO HYDROCARBON WATER MIXTURES/

We have used an efficient, new Gibbs minimization method with an equat ion of state (EOS) model to predict phase equilibria for hydrocarbon/w ater binary mixtures. The method utilizes the observation by Eubank an d Hall (1995) that a plot of the derivative of the Gibbs energy of mix ing against composition exhibits phase loops similar to those associat ed with the Maxwell rule. Equilibrium exists when the positive and neg ative areas are equal above and below a specific value of the derivati ve. Hence, we call the method the Equal Area Rule (EAR). The EAR appli cation procedure automatically performs a stability analysis for the s ystem. EAR also presents exciting possibilities when calculating phase equilibria for multi-component mixtures. Shyu et al. (1995) have appl ied the method to ternary liquid-phase systems using activity coeffici ent models.