Air separation method and apparatus

An apparatus for separating air to produce an oxygen product, said apparatus comprising:

• an air separation plant configured to separate the air through cryogenic rectification and having a higher pressure column and a lower pressure column operatively associated with one another in a heat transfer relationship to produce nitrogen-rich reflux for the higher pressure column and the lower pressure column and means for producing the oxygen product from an oxygen-rich liquid column bottoms of the lower pressure column;
• the operative association of the lower pressure column and the higher pressure column including:
• means for partially vaporizing a crude liquid oxygen stream composed of a crude liquid oxygen column bottoms of the higher pressure column against at least partially condensing an argon-enriched vapor produced in the lower pressure column, means for producing a supplemental nitrogen-rich reflux stream and an oxygen-enriched stream having a greater oxygen content than the crude liquid oxygen column bottoms from a two-phase stream produced, at least in part, from the crude liquid oxygen stream after the partial vaporization thereof;
• the argon-enriched vapor at least partially condensed at a location of the lower pressure column where the argon-enriched vapor has a nitrogen concentration between 0.1 and 5.0 mole percent and the resulting condensate will combine with downcoming liquid of the lower pressure column and increase a liquid to vapor ratio in a lowermost section of the lower pressure column;
• and
• the supplemental nitrogen-rich reflux stream and the oxygen-enriched stream producing means connected to the lower pressure column such that the oxygen-enriched stream and at least part of the supplemental nitrogen-rich liquid stream are fed at successively higher locations of the lower pressure column and above the location of the lower pressure column at which the argon-enriched vapor is at least partially condensed.