Production of high pressure oxygen

Claim 1

In a process for the separation of oxygen having a pressure of 1.7 to 3.6 bars from air in a two-stage low-temperature rectification column, the steps comprising: (a) subdividing preliminary purified and compressed air having a pressure of 5.8 to 7.8 bars absolute into a minor stream constituting 18-34% of the air and a major stream constituting the remainder of the air; (b) further compressing said minor stream of air from a pressure of 5.8 to 7.8 bars to a pressure of 6.5 to 10 bars absolute wherein said minor stream is compressed incrementally by at least 0.7 bars; (c) at least partially liquefying resultant further compressed air feed in a condenser-evaporator functionally separate and distinct from said two-stage low-temperature rectification column in indirect heat exchange contact with vaporizing liquid oxygen product maintained at about 0.4 to 2.0 bars pressure higher than the pressure in the sump of the low pressure column from which the liquid oxygen is obtained, said oxygen vapor having a pressure of 1.7 to 3.6 bars; (d) passing resultant at least partially liquefied air into the high pressure stage of the rectification column; (e) cooling the major stream of the air feed without further compressing; (f) passing resultant cooled major stream of the air feed into the high pressure stage of the rectification column; (g) withdrawing a gaseous stream acting as a compensating stream from said high pressure stage; (h) partially warming said compensating stream in indirect heat exchange with said major stream of the air feed being cooled in step (e), and also warming said compensating stream in indirect heat exchange with resultant compressed minor stream of the air feed, the partially warming of said compensating stream being conducted in a heat exchanger distinct and independent from said condenser-evaporator of step (c), said compressed minor stream of air feed is first passed through said independent and distinct heat exchanger for warming said compensating stream before said compressed minor stream is passed into said condenser-evaporator of step (c), (i) expanding resultant partially warmed stream in a turbine; and (j) employing resultant mechanical energy directly from the turbine for said further recompressing of said subdivided minor stream of the feed air in a coupled brake blower.