Patent ID: 6622520
Filing Date: 2003-09-23
Classification: F25J,Y10S

Abstract:
A method for producing low purity oxygen comprising:(A) passing feed air into a higher pressure column and separating the feed air within the higher pressure column by cryogenic rectification into nitrogen-enriched vapor and oxygen-enriched liquid; (B) passing oxygen-enriched liquid into a lower pressure column, condensing a first portion of the nitrogen-enriched vapor, and passing at least some of the resulting condensed first portion nitrogen-enriched liquid into the higher pressure column; (C) turboexpanding a second portion of the nitrogen-enriched vapor, condensing the turboexpanded second portion of the nitrogen-enriched vapor, and passing the condensed second portion nitrogen-enriched liquid into the lower pressure column; (D) producing by cryogenic rectification within the lower pressure column nitrogen-richer vapor and oxygen-richer liquid, and passing oxygen-richer liquid from the lower pressure column into an auxiliary column; and (E) producing by cryogenic rectification low purity oxygen within the auxiliary column, and recovering low purity oxygen product from the lower portion of the auxiliary column.