The process of vacuum pressure swing adsorption (VPSA) contains at least two steps: adsorption (under higher pressure) and desorption (under lower pressure), and cyclical repetition of the operation. In order to obtain oxygen product continuously, two adsorption beds are usually adopted in an oxygen producing plant. From the perspective of energy saving, consumption reducing and smooth operation, there are some necessary assistant steps, such as even pressure, oxygen purge, etc.
Generally speaking, each adsorption bed must experience adsorption, forward pressure reduction, evacuation or regeneration after decompression, purging and replacement, even pressure and boost such steps; and they are in a cyclical repetition of operation. At the same time, each of the adsorption bed is at different steps. Under the control of computer, they switch regularly to make several adsorption beds operating coordinately; their paces are staggered in time so that the oxygen separation from air by pressure swing adsorption plant can run smoothly. Thus, produce oxygen continuously.