Theoretical analysis of concentration polarization in membrane modules for gas separation with feed inside the hollow-fibers

A mathematical model has been developed to investigate the effects of the polarization of concentration in gas separation hollow-fibers modules when the gas feed is made inside the fibers, in co- and counter-current configuration. This model considers the effects of polarization in the boundary layers and porous support of the membranes. This effect was analyzed in terms of the permeation flux, selectivity, operating pressure and feed velocity. The simulations of a binary gas mixture separation (A + B) included the operation parameters and the properties of the membrane. The results demonstrated the importance of the concentration polarization for the analysis of the process and for the design. The permeation rate resulted to be the most important factor affecting the polarization. Indeed, for the system studied and in both configurations, the effects of concentration polarization were noticeable when the A permeance and A/B selectivity where higher than 1000 GPU and 100, respectively (1 GPU = 3.346 × 10−13 k mol m−2 s−1 Pa−1).