Air separation

摘要

A stream of precooled and purified air is introduced through an inlet 202 into a double rectification column comprising a higher pressure rectification column 204 and a lower pressure rectification column 206 and is separated therein into an oxygen-rich fraction and a nitrogen-rich fraction. A stream of argon-enriched oxygen vapour flows from an outlet 274 of the lower pressure rectification column 6 into a side column 252 in which argon is separated therefrom. An oxygen-enriched liquid air stream is taken from an outlet 216 at the bottom of the higher pressure rectification column 204. A vaporous oxygen-enriched air stream is introduced into the lower pressure rectification column 206 through an inlet 246 above the outlet 274. At least part of the oxygen-enriched liquid is separated in a further or intermediate pressure rectification column 224 provided with a reboiler 222, thereby forming a vapour depleted of oxygen and a liquid air stream further enriched in oxygen. At least one stream of the further-enriched liquid is vaporised to form the oxygen-enriched vapour that is introduced through the inlet 246 into the lower pressure rectification column 206. A part of the oxygen-depleted vapour is condensed in a condenser 230 and is taken as product or reintroduced into the lower pressure rectification column 206. The partial reboiling in the reboiler 222 is effected by indirect heat exchange with a vapour stream withdrawn from an intermediate region of the side column 252 through an outlet 281. The condenser 230 is cooled by a stream of liquid withdrawn through an outlet 242 of the further rectification column 224.