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Abstract

A cryogenic air separation method and apparatus in which a lower pressure distillation column is configured to receive, at successively higher locations of the lower pressure column and at successively lower temperatures, crude oxygen derived from a crude liquid oxygen stream discharged from a higher pressure column, an intermediate reflux stream and a nitrogen-rich reflux stream. All of the streams are subcooled and depressurized. The subcooling is conducted such that the intermediate reflux stream and the nitrogen-rich liquid stream cocurrently, indirectly exchange heat to a nitrogen-rich vapor stream withdrawn from the lower pressure column and the intermediate reflux stream is subcooled to a temperature between the temperatures over which the nitrogen-rich liquid stream is subcooled. Additionally, the crude liquid oxygen stream and the intermediate reflux stream can, cocurrently, indirectly exchange heat to a pressurized liquid stream used in forming an oxygen product and the nitrogen-rich vapor stream.

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First Claim