| 摘要 |
Air is bled from the air compressor 4 of a gas turbine 2 and is cooled in heat exchanger 16 to a temperature suitable for its separation by rectification. The air is separated in a double rectification column 22 comprising a lower pressure rectification column 28, operating at a pressure at its top of at least 2 bar, and a higher pressure rectification column 24. Gaseous oxygen and nitrogen products are withdrawn from the lower pressure rectification column 26 through outlets 39 and 41 respectively and are warmed countercurrently to the air stream in the heat exchanger 16. Two nitrogen side streams at different temperature from one another are withdrawn from the heat exchanger 16. The warmer stream is expanded in an expansion turbine 50, the colder stream in an expansion turbine 48. Both the expanded nitrogen streams are returned to the heat exchanger 16 and warmed therein. Part of the warmed nitrogen product stream is compressed in a compressor 52, is cooled in the heat exchanger 16 and is condensed in a condenser-reboiler 46 to form a liquid nitrogen product. <IMAGE>
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