Flow-field design for improving hydrogen recovery in a palladium membrane tube

The installation of baffles in a membrane tube is an effective way to lessen concentration polarization and improve hydrogen separation efficiency. In order to enhance the performance of hydrogen recovery, the flow-field design in a membrane system, which is composed of an internal tube and a shell, is performed through the computational fluid dynamics. The influences of baffle pattern, baffle location, and the ratio of baffle length to shell radius (L/0.5D₀) on hydrogen recovery are analyzed. The impacts of the Reynolds numbers in the tube and the shell as well as the pressure difference across the tube on hydrogen permeation are also evaluated. The predictions suggest that a single baffle installed on the shell and located at the leading edge of the membrane can effectively improve hydrogen separation. Increasing the ratio of L/0.5D₀ and decreasing the Reynolds number of feed gas intensify hydrogen recovery in a significant way, whereas increasing the Reynolds number of sweep gas merely raises the recovery to a small extent. Installing a baffle in the membrane tube enables the increment of hydrogen recovery up to 10% when compared to that without baffle. Hydrogen in the feed gas can be recovered completely at L/0.5D₀=0.75 when the Reynolds number of the feed gas is as low as 15.