STUDIES ON GAS SEPARATION BY POLYMERIC MEMBRANE

Abstract

The gas transport and separation properties of polymers have been successfully exploited in commercial ventures. Industrial applications employing membrane processes range from production of pure gases to barrier coating for protection against environmental elements. Membrane separations are simple, energy efficient processes, which can be economically competitive with traditional separation technologies. In this study experiments were done for single gas (CO2 or N2) and mixed gas (CO2+N2) permeation for pressure ranging between 1.5 to 5.5 bars. Experimental setup was locally fabricated by Indian Institute of Petroleum, Dehradun and consists of a circular flat type membrane cell using cellulose acetate membranes, both of dense and asymmetric types, which were self prepared by varying thickness and surfactant (Span-80) concentration. Experimental method and formula given in ASTM designation: D-1434-66 (Reapproved 1972) was used to calculate permeation rate and permeability. A solution diffusion model was used to calculate theoretical permeation rate and was compared with experimental permeation rate. Based on this study, it was observed that the permeability of CO2 was in the range of 5 to 14 Barrers, which is similar to the values reported in literature of 1.1 to 15 Barrers (1 Barrer = 100 cm3 (STP) cm/cm2 sec. cm of Hg). In mixture, permeability and permeation rate of CO2 was found to decrease, however, the permeation rate and permeability of N2 increased with increase of film thickness and pressure. This could be due to plasticization of cellulose acetate membrane by CO2. Model values of permeation rates were found to be fairly close to experimental permeation rates. Addition of surfactant (Span-80) in the cellulose acetate casting solution were found to suppress macrovoids in the polymer membranes.