Elemental composition method for computation and analysis of simultaneous chemical and phase equilibrium

An elemental composition method for computation and analysis of simultaneous chemical and phase equilibrium (CPE) of non-ideal mixtures is proposed. The concept of element is defined, the relationship between component composition and elemental composition is derived, and the concept of elemental potential and its physical meaning are further cleared from the view point of thermodynamics. The relationship between chemical potential and elemental potential is derived in the thermodynamic principles, and the computation equations for CPE problem are obtained based on elemental potential. A simple form of necessary and sufficient condition in terms of elemental composition for reactive azeotropes is derived, which takes the same functional form as the condition for azeotropes in non-reactive systems. The element in this note may be atoms, molecules or group radicals. The presented method is applicable to CPE problem of non-ideal mixtures, and the computation can be simplified by the dimension reducing method. The presented method was supplied to compute and analyze CPE problem of several examples and it is found that it is a robust and efficient method.