| 摘要 |
Air which has had water vapour and carbon dioxide removed therefrom is introduced at about its dew point into a higher pressure distillation column 4 through an inlet 8, and is separated into oxygen-rich and nitrogen-rich fractions. A stream of oxygen-enriched liquid is withdrawn from the higher pressure column 4 through an outlet 18 and is introduced into a lower pressure distillation column 6 in which it is separated into oxygen and nitrogen. Nitrogen gas is taken from an outlet 32 at the top of the lower pressure column 6 and is employed in a heat pump cycle in which it is compressed in compressor 34, cooled in heat exchanger 2, condensed in reboiler 26 to provide reboil for the column 6, and returned to the top of the column 6 as reflux. A part of the liquid nitrogen stream leaving the reboiler 26 is diverted from the flow to the top of the column 6 and is pumped into the top of the column 4 as reflux. The operating pressures of the columns 4 and 6 are thus able to be set independently of one another. |
