Thermodynamic analysis of the driving force approach: Non-reactive systems

A thermodynamic analysis of the driving force approach proposed by Gani and Bek-Pedersen (2000) has been performed. Through the thermodynamic analysis, the fundamental relationships between the driving force definition and the energy involved in the vapor-liquid phase equilibrium are revealed. It is clearly demonstrated that the driving force approach is not a heuristic relationship, rather, it may be considered as a powerful thermodynamics-based approach for the design of many non-reactive processes: i.e., distillation, liquid extraction, crystallization, etc. It is shown that the driving force is explicitly related to: the vapor and liquid enthalpies, the heats of vaporization of the different species and the energy associated to the non-idealities. Also, the connection between the maximum driving force and the minimum separation energy is shown through the thermodynamic separation efficiency concept proposed by Robinson and Gilliland (1950). The analysis is highlighted with two representative separation problems involving an ideal and a non-ideal binary mixtures.