Predicting CO2 and CH4 transport in landfill gas using porous inorganic membranes operated in the Darcy regime.

The present work is focusing on the utilization of previously fabricated membrane to study the effect of pressure drop and temperature on permeability. Mass transfer considerations were used under previously optimized conditions. Subsequently, gas permeation study was conducted on ceramic membranes in CO 2 and small molecules present in biogas and it was found that the permeance of CO2 and CH4 decreased in the order of 15 nm > 200 nm > 6,000 nm, according to the decrease in pore size of the membranes. The transport of pure gases through a microporous composite membrane is also discussed. The membrane consists of an alumina support with mean pore diameters of 15,200 and 6,000 nm and a TiO2 washcoat top (separation) layer. The theory of Knudsen diffusion, laminar flow and Darcy flow are used to describe the transport mechanisms. It appears for the composite membrane that Knudsen diffusion occurs in the top layer and combined Knudsen diffusion/laminar flow in the support at pressure levels at 60 kPa and below. As pore sizes reduce further, and finally disappear, the transport process that takes over in a non -porous membrane is solution–diffusion—is a far simpler process than the complex, surface-mediated adsorption–surface diffusion occurring in the finest-scale porous membranes. For all experiments described below, the gauge pressure was kept lower than these critical pressures