Investigation of capillary size on the separation factor of gaseous separation membrane with DSMC method

Abstract

Due to significant development of membrane applications in separation science, studying on membranes and geometrical effects is of great importance. The geometry and quantity of pores directly affect the separation factor. In an isotopic gaseous separation system, by increasing the product withdrawal rate from the system, the amount of separation will decrease. Generally, as the rate of withdrawal from the system increases, the amount of separation factor will decrease. In this research, using the DSMC method (Direct Simulating Monte Carlo Method), the gaseous separation system and flow through membrane is followed by focusing on effects of pore diameter. In this work, a mixture contains 32SF6 (light component) and 34SF6 (heavy component) is selected for separation. The results indicate when the capillary diameter increases, the product concentration is reduced, which means that the separation factor is reduced. It is shown for capillaries with diameters of greater than the nominal value, the separation will be stopped. As the diameter of the membrane capillaries increases, the withdrawal rate of the gas flow from the system will increase. Therefore, increasing the diameter of the membrane capillaries will increase the withdrawal rate of the system and reduce the separation factor. Also, diffusion velocities are evaluated.