Overall mass transfer rates during pervaporation: effect of the convective velocity on the separation

摘要

The polarization layer can strongly affect the separation process by pervaporation. This paper defines the overall mass transfer rates, involving the effect of both the polarization and the membrane layers, in cases of constant diffusion coefficient, variable diffusion coefficient and application of the Flory-Huggins theory. These rate equations enable the user to take into account the exact effect of the polarization layer on the separation. Due to the low value of Pec-let number, during pervaporation process the expressions of mass transfer rates, enrichment, and separation factor of binary mixtures can be essentially simplified. It has been stated that the Peclet number does not affect significantly the overall mass transfer rate, while it affects strongly the enrichment or the separation factor. It has been proved that the k/(k_mH) value dominantly affects the separation efficiency during the pervaporation processes.