| 摘要 |
PROBLEM TO BE SOLVED: To improve separation efficiency of upper and lower rectifying columns by extracting a part of gas ascending through the upper rectifying column, raising the temperature of the extracted gas to a normal level in a heat exchanger and boosting the pressure thereof by a compressor, and introducing the gas cooled through heat exchange to the lower rectifying column thereby increasing air supply thereto. SOLUTION: Crude air from a crude air compressor 14 is passed through an air preprocessing facility 15 and an air heat exchanger 16 and then fed to a lower rectifying column 4 after being cooled to a temperature close to liquefaction point. Liquid nitrogen and liquid air extracted from the lower column 4 are fed through ducts 18, 19 to a supercooler 20 and then fed, as circulation liquid, to an upper rectifying column 1 for further rectification. Oxygen gas is extracted from the lower part 8 of the upper column through a duct 21 and used after being raised to normal temperature through an air heat exchanger 16. On the other hand, ascending gas having oxygen purity in the range of 5-90% is extracted partially from the upper column 1 through a duct 2 and boosted by a booster 25 above the lower column pressure. Subsequently, it is cooled through a heat exchanger 24 and circulated back to the lower column 4 through a duct 5.
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