Forced unsteady state operation for hydrogen separation through Pd-Ag membrane after start-up

A steady state hydrogen separation through a Pd-Ag membrane from a gas mixture like synthesis gas may encounter a rapid decrease of hydrogen permeation due to interaction of hydrogen and nitrogen, which blocks the palladium surface. In this study, a dedicated composition modulation for enabling unsteady state operation of the feed gas was proposed to control the process of hydrogen permeation and improve the stability of the Pd-Ag membrane. The investigated parameters were focused on hydrogen recovery and deactivation time as influence of varying the switching time. The application of the unsteady state operation on Pd75-Ag25 membrane obviously showed the influence of the dynamic operation on the performance of H2 permeation, which decreased or increased, depending on the switching times. The unsteady operation with switching times 1 and 5 min resulted in the H2 recovery of 27% and 24%, respectively, without showing any deactivation times. It has also been observed during experiment that the unsteady state operation of the Pd75-Ag25 membrane for hydrogen separation could show better performance compared to steady state operation if proper transient operation procedure could be developed.