| 摘要 |
An air stream is compressed at 2 and purified at 16 and has a major portion cooled in a heat exchanger 18 prior to its separation in a double rectification column 22, the lower pressure column 26 of which operates at a pressure of 2.5 to 4.5 bar. At least part of the nitrogen product stream 50 from the column 24 passing through the exchanger countercurrently to the air is expanded in a turbine 52 to create refrigeration so as to maintain a temperature diffferential of at least 10K between the expanded nitrogen and air stream being cooled, which reduces the size of the exchanger compared with conventional plant. The minor air portion is employed to generate refrigeration for the air separation by being further compressed at 34 and expanded at 36. The column 22 and heat exchanger are located in an insulated housing. <IMAGE>
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