Triple column distillation system for oxygen and pressurized nitrogen production

A process for the separation of a compressed feed air stream to produce gaseous oxygen with purity less than 98% and nitrogen with high recoveries comprising:

• (a) using three distillation columns consisting of a low pressure column, a medium pressure column which operates at a pressure higher than the low pressure column and a high pressure column which operates at a pressure higher than the medium pressure column;
• (b) feeding a portion of the compressed feed air stream to the high pressure column for distillation into a high pressure oxygen-enriched liquid bottoms and a high pressure nitrogen overhead;
• (c) feeding at least a portion of the high pressure oxygen-enriched liquid bottoms to the medium-pressure column;
• (d) condensing at least a portion of the high pressure nitrogen overhead by heat exchange against a liquid stream of the medium pressure column and using at least a portion of the condensed high pressure nitrogen to provide reflux to the high pressure column;
• (e) removing a medium-pressure oxygen-enriched liquid from the medium pressure column at a location below the high pressure oxygen-enriched liquid bottoms feed point and feeding the removed, medium-pressure oxygen-enriched liquid to an intermediate point of the low pressure column for distillation;
• (f) producing at least a portion of the oxygen product from the bottom of the low pressure column;
• and
• (g) recovering greater than 35% of the feed air flow to the distillation column system as nitrogen product wherein the nitrogen product is recovered from the high pressure column, the medium pressure column or both the high pressure and medium pressure columns.