System and method for enhanced recovery of liquid oxygen from a nitrogen and argon producing cryogenic air separation unit

A method of separating air in a cryogenic air separation unit to produce one or more nitrogen products, a crude argon product, and a liquid oxygen product comprising the steps of:

• (a) separating an incoming feed air stream in a distillation column system having a higher pressure column and a lower pressure column linked in a heat transfer relationship via a condenser-reboiler to produce an oxygen enriched stream from the base of the lower pressure column and a nitrogen product stream from the overhead of the lower pressure column;
• (b) further separating an argon-oxygen enriched stream taken from the lower pressure column in an argon column arrangement to produce an oxygen enriched bottoms stream and an argon-enriched overhead;
• (c) directing the oxygen enriched bottoms stream into the lower pressure column;
• (d) directing the argon-enriched overhead to a condensing side of an argon condenser;
• (e) directing a first portion of the oxygen enriched stream from the lower pressure column and a stream of liquid nitrogen from an external source to a boiling side of the argon condenser;
• (f) condensing the argon-enriched overhead against the first portion of the oxygen enriched stream from the lower pressure column and the liquid nitrogen from an external source to produce a crude argon stream and an argon reflux stream while boiling the first portion of the oxygen enriched stream and the liquid nitrogen to produce an oxygen enriched waste stream;
• and
• (g) taking a second portion of the oxygen enriched stream from the lower pressure column as a liquid oxygen product;
• wherein the cryogenic air separation unit produces the one or more nitrogen products with a total nitrogen recovery of 98 percent or greater of the nitrogen contained in the incoming feed air stream and produces the crude argon with an argon recovery of 30 percent or greater of the argon contained in the incoming feed air stream.