| 摘要 |
Separate air streams 8a and 8b are both compressed, purified and cooled. The stream 8b is introduced into a higher pressure distillation column 16 at about its dew point. The stream 8a is condensed in a condenser 14 and is then split. One portion is fed into the column 16. The remaining portion is sub-cooled in a sub-cooler 21 and then introduced into a lower pressure distillation column 23 at an intermediate level thereof. Nitrogen is withdrawn from the top of the column 16, and is condensed in condenser 45. The resultant condensate is used to provide reflux for both columns 16 and 23. Cooling for the condenser 45 is provided by a liquid stream withdrawn from an intermediate stage of the column 23. Substantially pure liquid oxygen is withdrawn from the bottom of the column 23 and is vaporised by heat exchange in the condenser 14 with the liquefying portion of the incoming air, and is then taken as product.
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