Abstract: A high pressure as stream having a hydrogen content of up to about 90 mol percent is passed to a separator containing a permeable membrane capable of selectively permeating hydrogen. The separator is used to achieve a bulk separation of the desired hydrogen from impurities contained in the gas stream. The separated hydrogen is recovered at a reduced pressure and is passed to a pressure swing adsorption system adapted for operation at said reduced pressure. The off-gas from the separator is recovered essentially at the higher pressure of the gas stream. A portion of the off-gas is throttled to a lower pressure, with appropriate power recovery, and is passed to the pressure swing adsorption system as a co-feed gas, thereby contributing to the recovery of purified hydrogen product and to a reduction in the operating costs for the desired hydrogen separation and purification. The remaining off-gas is recovered as a relatively high pressure fuel or feed gas for other purposes.

Abstract: Void space gas is released from an adsorbent bed at a higher adsorption pressure by cocurrent depressurization of the bed. The released gas is passed to another bed of a pressure swing adsorption system to equalize the pressure therebetween, the other bed being initially at a lower pressure. A portion of the product effluent withdrawn from yet another bed of the system is not passed to the bed undergoing repressurization, as in conventional practice, but is passed to an external repressurization storage tank during said pressure equalization step. Upon completion of this step, the product effluent is withdrawn from the repressurization tank and passed to said bed undergoing repressurization.