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

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 H₂concentration in the feed gas on the interfacial H₂permeation and H₂recovery are analyzed. The results indicate that the minimum H₂partial pressure difference and permeation rate along the membrane surface develops, as a consequence of competition between the membrane permeance and the H₂partial pressure difference. A dimensionless mass transfer parameter (ξ), which is a non-dimensional driving force ratio between H₂diffusion in the gas phase and H₂permeation 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 H₂inlet concentration. When the H₂inlet concentration is low, all H₂in the feed gas can be recovered and the minimum distribution no long appears. This also implies that all CO₂is separated.