Mass transfer modelling for solvent dehydration by pervaporation

A set of equations for design and optimisation of solvent dehydration by pervaporation is developed based on a model of mass transport through membranes that permeate preferentially water. This model assumes a mechanism of sorption-diffusion-desorption and introduces a diffusion coefficient which is dependent on the membrane water concentration and on the feed temperature. The integration of Fick's law with the adequate boundary conditions yields the partial fluxes of water and solvent as a function of parameters pertaining to pervaporation operating conditions and to membrane characteristics. These parameters are obtained by the fitting of the flux equations to experimental data for the partial fluxes versus the feed water concentration relative to the permeation of the mixture water/2-methoxyethanol through GET Pervap 1000 membranes. The laboratory experiments were carried out with mixtures of feed water content ranging from 15 to 0.1% w/w and at feed temperatures of 45, 72 and 80 degrees C. The design equations with fitted parameters are also used to assess the dehydration of 2-methoxyethanol through the determination of the membrane surface area for different feed water contents, from 4 to 15% w/w, and for different specifications of water content in the final product, from 0.1 to 1% w/w. The design equations can also be used in the optimisation of the energy requirements and as a tool for the techno-economical analysis of pervaporation dehydration for solvent recovery. (C) 2000 Elsevier Science B.V. All rights reserved.