Improved Solution Thermodynamics Modeling in Pervaporation

Abstract

The current work features a system-level design of pervaporation processes (typically utilized to break azeotropes) that is solution thermodynamics-based (inclusive of validated excess thermodynamic properties). Unlike the standard pervaporation modeling methodology in the literature, the current method (referred to here as PervapS3) deconstructs the membrane module into its constituent units, and the material and energy flows were mathematically validated. These amendments to the previous methodology (i.e., leaf-wise modeling, mathematical validation, and inclusion of excess thermodynamic properties) revealed significant deviations in key parameter values. For a given large-scale pervaporation process dehydrating aqueous isopropanol, the total membrane area and energy requirement calculated were up to 22% and 19% less than the values calculated using the previous methodology. Moreover, due to the inclusion of excess thermodynamic properties in the PervapS3 method, the minimum separation work and the second law (thermodynamic) efficiency were up to 94% and 78% less. In other words, the previous pervaporation modeling methodology overestimated membrane area, energy requirement, minimum separation work, and second law efficiency. Considering a conventional azeotropic distillation process for comparison with pervaporation, it was observed that the simulation-based distillation models from the literature were inclusive of the system non-idealities. Per the previous method, the non-ideal second law efficiency of azeotropic distillation would be compared against the ideal second law efficiency of pervaporation, overestimating the latter. The non-ideal second law efficiency must be employed to facilitate a fairer and more accurate comparison of disparate separation technologies.