| 摘要 |
<p>Compressed air is purified in apparatus 4 and passed through heat exchanger 6 in which it is reduced in temperature ready for rectification in a double column comprising a higher pressure rectification column 10 and a lower pressure rectification column 12 which are linked by a condenser-reboiler 14. The air is separated in the column 10 into oxygen-rich and nitrogen fractions. The oxygen-rich fraction is separated in the lower pressure column 12 into an oxygen and a lower pressure nitrogen product. Liquid nitrogen from the higher pressure column 10 is used as reflux in the lower pressure column 12, and a gaseous nitrogen stream is withdrawn from the column 10 as higher pressure nitrogen product. In order to compensate for the resulting loss of reflux in the column 12, a part of the lower pressure nitrogen product stream is compressed in compressor 38, cooled by passage through heat exchanger 6, and condensed in condenser 40. The resulting condensate provides additional reflux in the column 12. This arrangement makes possible enhanced power recovery from nitrogen produced in an air separation plant providing an oxygen product at an elevated pressure.</p> |
