When the adsorption capacity of an adsorbent is a function of pressure or one component in a gaseous mixture is preferentially adsorbed at high pressures, PSA can be used for gas separation. Essentially, a bed of adsorbent in one unit is initially exposed to the gas mixture at a high pressure. The feed stream is then diverted to another unit, while the initial unit is vented or flushed at a lower pressure. A significant fraction of the adsorbate desorbs, and the bed in this unit is regenerated and reused following re-pressurization.

For each of these systems, more than one bed is required for continuous operations to accommodate regeneration of spent material and servicing. The setup required is similar to that shown in Figure 5.20.12.

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