Interfacial permeation phenomena of hydrogen purification and carbon dioxide separation in a non-isothermal palladium membrane tube

Abstract

Hydrogen can be purified and carbon dioxide can be separated from their gas mixtures in a palladium (Pd) membrane tube. To figure out the hydrogen permeation characteristics in a non-isothermal Pd membrane tube, a numerical method is developed. The influence of the Reynolds numbers at the retentate and permeate sides, the temperatures of feed gas and sweep gas, and the H2 concentration in the feed gas on the interfacial H2 permeation and H2 recovery are analyzed. The results indicate that the minimum H2 partial pressure difference and permeation rate along the membrane surface develops, as a consequence of competition between the membrane permeance and the H2 partial pressure difference. A dimensionless mass transfer parameter (ξ), which is a non-dimensional driving force ratio between H2 diffusion in the gas phase and H2 permeation across the membrane, is conducted to aid in illustrating the mass transfer characteristics along the membrane surface. The ξ curve is insensitive to the Reynolds numbers, but depends significantly on interfacial temperature and H2 inlet concentration. When the H2 inlet concentration is low, all H2 in the feed gas can be recovered and the minimum distribution no long appears. This also implies that all CO2 is separated.