Adsorption process

Claim 1

In a pressure swing adsorption process wherein a gaseous mixture under elevated pressure is conducted in cyclic alternation through only three adsorbent-filled adsorbers, with selective adsorption of at least one first component and formation of a product depleted in said first component, each adsorber passing through mutually chronologically shifted switching cycles, and each switching cycle comprising an adsorption phase at maximum process pressure, expansion phases conducted first cocurrently and then countercurrently to the adsorption direction, a desorption phase at minimum process pressure, and pressure buildup phases for restoring the adsorption pressure, and wherein pressure equalization takes place between an adsorber in a cocurrent expansion phase and an adsorber in a pressure buildup phase, the improvement which comprises the following sequential phases: after termination of the adsorption phase of (a) a first adsorber, a first cocurrent expansion phase with the thus-obtained expansion gas being utilized for scavenging a second adsorber which is in a desorption phase; (b) a second cocurrent expansion phase with the thus-obtained expansion gas is utilized for pressurizing the second adsorber; (c) a countercurrent expansion phase during which a residual gas is withdrawn from the inlet end of the first adsorber; (d) the desorption phase during which scavenging is carried out with a cocurrent expanion gas from the third adsorber; and (e) two pressure buildup phases of which the first takes place in pressure equalization with the third adsorber which is in the second cocurrent expansion phase, and the second takes place by introduction of product gas by way of the outlet end of the adsorber.