A method for multiphase equilibrium calculations

被引:18
作者
Han, GJ [1 ]
Rangaiah, GP [1 ]
机构
[1] Natl Univ Singapore, Dept Chem Engn, Singapore 119260, Singapore
关键词
multiphase equilibrium calculations; equation-solving methods;
D O I
10.1016/S0098-1354(97)00223-8
中图分类号
TP39 [计算机的应用];
学科分类号
081203 ; 0835 ;
摘要
Methods for multiphase equilibrium calculations are generally based on Gibbs free energy minimization or equation-solving. Equation-solving methods, although superior to free energy minimization methods for phase equilibrium calculations without chemical reactions, often involve sequential procedures for a priori phase identification. A simultaneous equation-solving method (tau-method), based on modifying mole fraction summations, is proposed for these calculations. It requires the solution of a minimization problem only once, and provides phases actually present at equilibrium, their quantities and compositions simultaneously; and phase identification in advance is not required. Phase characteristic variable and pseudo phase are introduced, and their significance discussed. tau-method is shown by analysis and numerical results, to be consistent with Nelson's (1987, Comput. Chern. Engng 11, 581-591) criteria for phase existence. The method is tested on typical examples for two-phase (vapor-liquid and liquid-liquid) and three-phase (vapor-liquid-liquid) equilibrium calculations. For each example, several conditions and/or different initializations are used, and the minimization problem is solved by a version of successive linear programming method. The results show that tau-method is successful and reliable for multiphase equilibrium calculations. (C) 1998 Elsevier Science Ltd. All rights reserved.
引用
收藏
页码:897 / 911
页数:15
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