Double column air separation process with hybrid upper column

Claim 1

Air separation process comprising compressing feed air, separating the feed air into nitrogen-rich and oxygen-rich components by countercurrent vapor-liquid contact in a double column air separation plant having lower pressure and higher pressure columns, removing nitrogen-rich component from the upper portion of the lower pressure column at a pressure not more than 3 psi greater than atmospheric, passing argon containing fluid from an intermediate point of the lower pressure column onto an argon column for separation into argon-rich and oxygen-rich portions, and carrying out the countercurrent vapor-liquid contact in the lower pressure column on vapor-liquid contacting elements consisting essentially of packaging in the section of the lower pressure column below said intermediate point and on vapor-liquid contacting elements which comprise trays in the remainder of the lower pressure column.