Patent ID: 6009723
Filing Date: 2000-01-04
Classification: F25J

Abstract:
In an elevated pressure air separation cryogenic process wherein feed air is compressed, treated to remove water and carbon dioxide, cooled to cryogenic temperature in a main heat exchanger having a cold end and a warm end and fed to a distillation column system having at least two (2) distillation columns for separation into at least a nitrogen-enriched product, a liquid oxygen-enriched product and a gaseous waste stream characterized in that:(a) at least a portion of said liquid oxygen-enriched product is vaporized to produce a gaseous oxygen-enriched product against a condensing, further compressed portion of the feed air stream;(b) at least a portion of said gaseous waste stream is work expanded in an expander, wherein the temperature of the gaseous waste stream entering the expander is at the same temperature as or warmer than the temperature of the warm end of said main heat exchanger;(c) the expanded gaseous waste stream of step (b) is removed from the process without introduction into the main heat exchanger;(d) work produced by the expansion of step (b) is used to provide at least a portion of the work required to further compress the portion of the compressed feed air which is liquefied in heat exchange against the oxygen-enriched portion of step (a); and(e) at least a portion of the required refrigeration for the process is supplied by expanding a process stream that is different than the gaseous waste stream.