Patent ID: 6536234
Filing Date: 2003-03-25
Classification: F25J,Y10S

Abstract:
A cryogenic rectification method for producing at least one of oxygen and nitrogen comprising:(A) compressing feed air, dividing the compressed feed air into two portions, further compressing one of the portions and passing the further compressed portion as a first feed air stream into a higher pressure column of a cryogenic rectification plant which also comprises a lower pressure column and a medium pressure column, and passing the other portion as a second feed air stream into the medium pressure column, said second feed air stream being at a pressure which is less than the pressure of the first feed air stream; (B) producing by cryogenic rectification oxygen-enriched liquid and nitrogen-enriched fluid within the higher pressure column; (C) passing oxygen-enriched liquid into the medium pressure column and producing intermediate vapor and intermediate liquid by cryogenic rectification within the medium pressure column; (D) passing a vapor stream taken from below the top of the higher pressure column in indirect heat exchange with intermediate liquid to produce higher pressure liquid and passing higher pressure liquid into the higher pressure column; (E) passing fluid from the medium pressure column into the lower pressure column and producing nitrogen-richer fluid and oxygen-richer fluid by cryogenic rectification within the lower pressure column; and (F) recovering at least one of the nitrogen-richer fluid and oxygen-richer fluid as product.