Air separation process for the production of oxygen-rich and nitrogen-rich products

Claim 1

In a process for the production of low purity gaseous oxygen by the cryogenic distillation of air using two integrally communicating distillation columns at different pressures having a high pressure distillation column and a low pressure distillation column, wherein feed air is compressed, purified of comtaminants which will freeze at cryogenic temperatures, and cooled., wherein at least a major portion of the compressed, cooled, purified feed air is fed to the high pressure distillation column., wherein a liquid oxygen stream is produced at the bottom of the low pressure distillation column., and wherein, at least a portion of the liquid oxygen stream from the low pressure distillation column is vaporized by heat exchange with at least a portion of the feed air; the improvement for increasing process energy efficiency comprises providing reflux for both the high pressure and low pressure columns by condensing at least a portion of nitrogen overhead produced at the top of the high pressure column, wherein a first portion of the high pressure column nitrogen overhead is condensed in a reboiler/condenser by heat exchange with a crude liquid oxygen stream, which as a result of the heat exchange is partially vaporized at a pressure greater than the low pressure column pressure and the vaporized portion is removed from the reboiler/condenser as a crude oxygen vapor stream, and wherein a second portion is condensed in an intermediate reboiler/condenser located internal to the low pressure column, and providing further refrigeration to the process by work expanding at least a portion of the crude oxygen vapor stream.