Pressure swing adsorption process with multiple desorption steps

Abstract

Pressure swing absorption processes are disclosed which employ a standard pressure swing absorption cycle comprising the steps of adsorption, one or more cocurrent depressurization steps for equalization or providing purge gas, a countercurrent depressurization step, a countercurrent purge step, and repressurization steps. The processes of the present invention also include an additional countercurrent desorption step performed in conjunction with the first countercurrent desorption step at above atmospheric pressure and a countercurrent purge step at about the adsorption temperature which can provide increased capacity and recovery as compared to PSA processes that only have one countercurrent depressurization step or otherwise do not have a countercurrent purge step. Preferably the pressure reduction during the second countercurrent depressurization step is accomplished by passing another stream from the process, such as the effluent from the first countercurrent desorption step, as a motive gas through an ejector which is in operative communication with the adsorber bed undergoing the second countercurrent desorption step.