PERVAPORATION PROCESS - MEMBRANE CONDITIONING AND EXPERIMENTAL MASS-TRANSFER ANALYSIS

An experimental study of the pervaporation process, through a chemical engineering analysis, was performed in an isothermic pilot plant using water-ethanol mixtures in contact with hydrophilic GFT membranes. Three membrane sets from different production series were tested and the main operating parameters studied were liquid temperature, permeate pressure and, in particular, the water content of the liquid feed. The original plant and the direct effect of temperature and pressure during pervaporation were previously presented. In this paper, a systematic analysis is discussed taking into account the history of the membrane, especially the membrane conditioning prior to the pervaporation experiments. It was observed that some precautions must be taken when using hydrophilic pervaporation membranes. A running transient state of more than 48 hours must be respected; the permeate side in the module must be kept under vacuum when liquid feed is circulating and in particular, contact of this hydrophilic membrane with pure water has to be avoided if high selectivity is requested. A simple empirical model was elaborated which showed the large effect of feed water content on mass transfer during pervaporation.