Process for nitrogen enrichment

Claim 1

A process for the separation of a gas mixture comprising the steps of: (a) repeatedly performing a cycle of operations in employing a first vessel containing adsorbent which adsorbs one component of a gas mixture more readily than another or the other component of the gas mixture, the cycle of operations comprising: (i) passing the gaseous mixture under pressure through the vessel whereby said one component is adsorbed and a gas stream relatively lean in the adsorbed component flows out of the bed as a product gas; (ii) regenerating the adsorbent by desorbing gas therefrom and causing a gas stream relatively rich in the desorbed gas to flow out of the vessel; (b) repeatedly performing such a cycle of operations employing a second vessel containing said adsorbent, the cycles being phase relative to one another such that at no time is step (i) or step (ii) in one cycle performed simultaneously with the corresponding step in the other cycle; (c) passing the product gas stream into a reservoir; (d) placing the two beds in flow communication with each other at intervals between successive adsorption steps; (e) halting the process during an interval between successive adsorption steps when the two beds are placed in flow communication, exhausting gas remaining in the vessels from the said vessels countercurrently to the flow of the gas mixture to thereby depressurize the vessels; and (f) purging the depressurized vessels by passing product gas from said reservoir to said vessels.