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SYSTEM AND METHOD FOR ENHANCED RECOVERY OF ARGON AND OXYGEN FROM A NITROGEN PRODUCING CRYOGENIC AIR SEPARATION UNIT

  • US 20190331417A1
  • Filed: 04/25/2018
  • Published: 10/31/2019
  • Est. Priority Date: 04/25/2018
  • Status: Active Grant
First Claim
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1. An air separation unit comprising:

  • a main air compression system configured for receiving a stream of incoming feed air and producing a compressed air stream;

    an adsorption based pre-purifier unit configured for removing water vapor, carbon dioxide, nitrous oxide, and hydrocarbons from the compressed air stream and producing a compressed and purified air stream, wherein the compressed and purified air stream is split into at least a first part of the compressed and purified air stream and a second part of the compressed and purified air stream;

    a main heat exchange system configured to cool the first part of the compressed and purified air stream to produce a vapor air stream and to partially cool the second part of the compressed and purified air stream;

    a turboexpander arrangement configured to expand the partially cooled second part of the compressed and purified air stream to form an exhaust stream that imparts refrigeration to the air separation unit;

    a distillation column system having a higher pressure column having an operating pressure between 6.0 bar(a) and 10.0 bar(a) and a lower pressure column having an operating pressure between 1.5 bar(a) and 2.8 bar(a) linked in a heat transfer relationship via a condenser reboiler;

    the distillation column system further includes an argon column arrangement operatively coupled with the lower pressure column, the argon column arrangement having at least one argon column and an argon condenser;

    the distillation column system is configured to receive all or a portion of the vapor air stream in the higher pressure column and to receive the exhaust stream in the lower pressure column or higher pressure column and to produce a first oxygen enriched stream from the lower pressure column having a first oxygen concentration greater than or equal to 99.5 percent oxygen, a second oxygen enriched stream from the lower pressure column having a second oxygen concentration greater than 93.0 percent and lower than the first oxygen concentration and a nitrogen overhead stream from the lower pressure column;

    wherein the argon column is configured to receive an argon-oxygen enriched stream from the lower pressure column and to produce a third oxygen enriched bottoms stream that is returned to or released into the lower pressure column and an argon-enriched overhead that is directed to the argon condenser;

    wherein the argon condenser is configured to condense the argon-enriched overhead against the first oxygen enriched stream or second oxygen enriched stream to produce a crude argon stream or a product argon stream, an argon reflux stream and an oxygen enriched waste stream;

    a subcooler arrangement operatively coupled with the distillation column system and configured to subcool a fourth oxygen enriched kettle stream from the higher pressure column and a nitrogen stream from the condenser-reboiler via indirect heat exchange with the nitrogen overhead stream from the lower pressure column; and

    wherein the air separation unit is configured to produce one or more high purity nitrogen products;

    wherein the air separation unit is configured to recover greater than 75 percent argon if the argon is condensed against the first oxygen enriched stream and configured to recover greater than 30 percent argon if the argon is condensed against the second oxygen enriched stream; and

    wherein the air separation unit is configured to produce one or more oxygen products including a high purity pumped oxygen stream from the lower pressure column at a pressure greater than or equal to 3.4 bar(a).

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