METHODS TO IMPROVE FLUX DURING ALCOHOL WATER AZEOTROPE SEPARATION BY VAPOR PERMEATION

Pervaporation and vapor permeation both offer interesting alternatives to distillation for the azeotropic dehydration of alcohols. Main reasons are considerable potential energy savings and their modular, flexible system configurations. In this paper various theoretical and practical advantages of vapor permeation compared to pervaporation are discussed. Experimental results of vapor permeation are presented. It is concluded that fluxes during vapor permeation will be principally higher, mainly because the driving force is less affected by concentration polarization and decreasing temperature. This allows the reduction of membrane area to be installed. Because no heat exchangers have to be included to supply the heat of evaporation, module construction for vapor permeation systems is more simple. It is shown that flux and selectivity during vapor permeation can be controlled by pressure, superheating and membrane impregnation. Furthermore impregnation of membranes is proposed as a promising route for tailoring flux and selectivity of vapor permeation membranes to specific applications.