Department of Chemical Engineering Separation Processes – 1 Module -1 Membrane Separation Processes Prof. Mohammad Asif Room 2B45, Building 3 Tel:

Gas Permeation Membrane (dense/micro-porous) is perm-selective For gas permeation, spiral wound or hollow-fiber modules are preferred for large scale applications because of their high packing density. For dense membranes, concentration polarization or external mass transfer resistances are generally negligible. Predicted values of diffusivities and solubilities of light gases in glassy and rubbery polymers are reported in the literature. Early applications of GP used nonporous membranes of cellulose acetates and polysulfones, which are still predominant, although polyimides, polyamides, polycarbonates, polyetherimides, sulfonated polysulfones, Teflon, polystyrene, and silicone rubber are also finding applications for temperatures to at least 70 0 C. Feed-side pressure is typically 300 to 500 psia, but can be as high as 1,650 psia. Typical refinery applications involve feed-gas flow rates of 20 million scfd. For high-temperature applications, membranes of glass, carbon, and inorganic oxides are available, but are limited in their selectivity. The appropriate partial-pressure driving force depends on the flow pattern. Cascades are often used to increase degree of separation.