| 摘要 |
Operating a cryogenic distillation column having a higher pressure stage, a lower pressure stage, and a medium pressure stage, to produce at least one of nitrogen and impure oxygen, comprises: (a) providing from a source of feed air: (i) a first feed air stream having a first pressure; and (ii) a second feed air stream having a second pressure less than the first pressure; (b) introducing the second feed air stream into the medium pressure stage for rectification into a medium pressure oxygen-enriched liquid and a medium pressure nitrogen overhead stream; (c) introducing a first fraction of the first feed air stream into the higher pressure stage for rectification into a higher pressure, oxygen-enriched liquid and a higher pressure nitrogen overhead stream; (d) condensing the higher pressure nitrogen overhead stream against a liquid from the lower pressure stage to form higher pressure nitrogen condensate and returning a portion of the higher pressure nitrogen condensate to the higher pressure stage as reflux; (e) reducing the pressure of at least a portion of at least one of the medium pressure, oxygen-enriched liquid and the higher pressure oxygen-enriched liquid to form a first reduced pressure, oxyen-enriched liquid; (f) condensing the medium pressure nitrogen overhead stream against the first reduced pressure, oxygen-enriched liquid, resulting in an oxygen-enriched vapour stream and a medium pressure nitrogen condensate, and returning a portion of the medium pressure nitrogen condensate to the medium pressure stage as reflux; (g) introducing the remaining portion of at least one of the higher pressure nitrogen condensate and the medium pressure nitrogen condensate to the lower pressure stage as reflux; and (h) introducing the oxygen-enriched vapour stream to the lower pressure stage as feed. |
