Importance

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Abstract

A process for the production of oxygen and nitrogen is applicable when the oxygen product is withdrawn from a distillation column system as a liquid, pumped to an elevated pressure and warmed at least in part by cooling a suitably pressurized stream. At least a portion of the compressed, purified, and cooled air is introduced to a first of at least three distillation columns. The first distillation column contains at least a condenser at its top, produces at least an oxygen-lean stream from or near its top and a first oxygen-enriched liquid from its bottom. A second distillation column, which contains a reboiler in its bottom, has no condenser, receives at least a portion of nitrogen-enriched liquid as a feed to its top, and produces a first nitrogen-rich vapor stream from its top and a second oxygen-enriched liquid from its bottom. A third distillation column, which contains a reboiler in its bottom, has no condenser, receives at least a portion of nitrogen-enriched liquid as a feed to its top, receives at least said second oxygen-enriched liquid as a feed, and produces a second nitrogen-rich vapor from its top and a liquid oxygen-rich stream from its bottom. The liquid oxygen-rich stream from said third distillation column is elevated in pressure and warmed, at least in part, by indirect heat exchange with a pressurized stream having a nitrogen content greater than or equal to that in the feed air, said pressurized stream being cooled without being subjected to distillation. The second distillation column receives as a feed at least one of (a) a portion of said first oxygen-enriched stream from said first distillation column; or (b) a portion of said cooled pressurized stream. The third distillation column receives as a feed at least one of (a) a portion of said first oxygen-enriched stream from said first distillation column; or (b) a portion of said cooled pressurized stream. In the preferred mode of operation, the first distillation column is at the highest pressure, the third distillation column is at the lowest pressure, and the second distillation column is at an intermediate pressure.

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First Claim