| 摘要 |
90B140-2 Air Separation Air is compressed in a first compressor 2 and has carbon dioxide and water vapour removed therefrom in a purification apparatus 4. The air is then cooled by passage through main heat exchangers 6 and 8 to a temperature suitable for its separation by rectification. The cooled air is separated in a single rectification column 16. Liquid oxygen is withdrawn from the column 16 by a pump 34 and is passed through the heat exchangers 8 and 6 countercurrently to the air stream and is thereby vaporised, a high pressure gaseous oxygen product thus being formed. Nitrogen vapour is withdrawn from the top of the column 6 through an outlet 20 is warmed by passage through a further heat exchanger 14 and the heat exchanger 8. The nitrogen is then divided. One part is further warmed in the heat exchanger 6, is compressed in a compressor 22, and is returned through the head exchangers 6 and 8 as a heat exchange stream countercurrently to the oxygen product stream. The other part of the nitrogen is expanded in turbine 30 with the performance of external work and is employed to provide cooling for the heat exchanger 14. The heat exchanger 14 is used to sub-cool a liquid nitrogen stream which is introduced into the column 16 through inlet 28 as reflux for the column 16. The compressor 22 operates at a relatively low pressure enabling plate-fin heat exchangers to be employed.
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