Diffusion and flow of gases through porous media.

Abstract

Diffusivities for the binary system of H2-N2 and permeabilities of N2 were measured for seven types of porous material over the pressure range 0.2--7.0 atm. These measurements were made in both axial and radial directions to investigate the isotropy of pore properties. Diffusivities and permeabilities were related to pore size distribution determined independently by mercury penetration. The method of Wakao and Smith gave satisfactory agreement except for the Nickel Catalyst and Vycor glass. In addition, diffusivities and permeabilities were related to each other satisfactorily. The relative contribution of macropores and micropores to diffusion at various pressures has been studied. The results for two different carbon pellets indicate that the micropores of these materials consist of largely blind pores. In the case of a Molybdema Alumina Catalyst, the entire micropore volume contributes to diffusion. A pore model for Vycor glass has been proposed and controlling pore radius for this material calculated from the measured diffusivities.