(343c) Hybrid Membrane-Distillation Processes

Kreis, P., Chair of Fluid Separation Processes

Pervaporation (PV) and vapour permeation (VP) are very suitable for the application to hybrid processes, such as the coupling with distillation or reaction since membrane separation is very selective and not limited by the vapour-liquid equilibrium. A very interesting process configuration is the purification of a side-stream of a distillation column which allows for the selective removal of one component out of a ternary non-ideal mixture (acetone, water, isopropanol) in one column. Another application is the purification of the bio-ethanol with a new type of dense membrane. Despite of all advantages hybrid membrane-distillation processes are not yet established in chemical industry due to a rather short lifetime of membranes and the lack of process know-how. The transmembrane mass transfer can be calculated with different modeling approaches (short cut, empirical, semi empirical, rigorous). Also the distillation column is simulated using the models of different complexity (short-cut, equilibrium stage, non-equilibrium stage). Relevant model parameters (e.g. permeances) are determined in lab and pilot scale plants. Detailed theoretical studies with full model complexity of both unit operations show the influence of the decisive structural parameters as well as operational parameters on concentration profiles, membrane area and product compositions. Consequently cost functions are implemented to investigate the economic potential. Compared to conventional processes the hybrid configuration shows promising economic benefits and it is very likely that such hybrid membrane processes will be applied in industrial scale in the near future. The paper presents the details of modelling and experimental validation of both applications of hybrid separations.


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