Abstract: A method of fractionation of air which includes the steps of feeding material air compressed by a withdrawing liquefied oxygen from the bottom of a crude argon column, pressurized under its own weight, and gasifying the liquefied oxygen by a reversible heat exchanger to provide an oxygen product while withdrawing an argon-rich gas at the top of the crude argon column by means of a blower so as to maintain the internal pressure of the crude argon column at a reduced pressure.

Abstract: An air separating system, including: at least three impurity adsorbers connected with each other by a number of on-off and follower valves and located in air supply conduits leading from an air cooling tower for water-cooling the feed air to reversing heat exchangers of the system; an expansion turbine for producing chill necessary for the system; turbine output gas conduits for feeding part of output gas of the expansion turbine to one of the impurity adsorbers through the heat exchangers; regenerating gas conduits for feeding to another adsorber the outflow of the turbine output gas from the first adsorber after heating; and a cooling water circuit for circulating cooling water between a water cooling tower for cooling the cooling water against waste nitrogen gas to be discharged from the system through the heat exchangers and the air cooling tower; the feed air from the air cooling tower being supplied to the heat exchangers in operation through at least one of the impurity adsorbers, while discharging par