Patent ID: 6305191
Filing Date: 2001-10-23
Classification: F25J

Abstract:
A method of separating air by rectification including cooling a first stream of compressed air taken from a first compression stage, at a first pressure, in a main heat exchanger to a temperature suitable for its separation by rectification, introducing the cooled first stream without further compression into the higher pressure column of a double rectification column including, in addition to the higher pressure column, a lower pressure column, in which a bottom liquid oxygen fraction is formed and a condenser-reboiler placing the higher pressure column in indirect heat exchange relationship with the lower pressure column, expanding in an expansion turbine from a second pressure with the performance of external work a second stream of compressed air taken from a second compression stage at the second pressure, introducing the expanded second stream of air into the lower pressure column, and taking an oxygen product from the bottom region of the lower pressure column, wherein the second pressure is less than the first pressure, the cooled first stream is introduced into the higher pressure column at essentially the first pressure, the first compression stage is downstream of the second compression stage, and the expansion turbine is the sole expansion turbine used in the method.