SYSTEM AND METHOD FOR ENHANCED RECOVERY OF ARGON AND OXYGEN FROM A NITROGEN PRODUCING CRYOGENIC AIR SEPARATION UNIT
First Claim
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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Accused Products
Abstract
A moderate pressure air separation unit and air separation cycle is disclosed that provides for up to about 96% recovery of argon, an overall nitrogen recovery of 98 percent or greater and limited gaseous oxygen production. The air separation is configured to produce a first high purity oxygen enriched stream and a second lower purity oxygen enriched stream from the lower pressure column, one of which is used as the refrigerant to condense the argon in the argon condenser, with the resulting vaporized oxygen stream used to regenerate the temperature swing adsorption pre-purifier unit. All or a portion of the first high purity oxygen enriched stream is vaporized in the main heat exchanger to produce the gaseous oxygen products.
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Citations
21 Claims
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1. An air separation unit comprising:
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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). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method of separating air to produce one or more high purity nitrogen products in a cryogenic air separation unit with a total nitrogen recovery of 98 percent or greater, the method comprising the steps of:
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compressing a stream of incoming feed air to produce a compressed air stream; purifying the compressed air stream in an adsorption based prepurification unit configured to removing water vapor, carbon dioxide, nitrous oxide, and hydrocarbons from the compressed air stream to producing a compressed and purified air stream splitting 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; cooling the first part of the compressed and purified air stream to a vapor air stream at a temperature suitable for rectification in a cryogenic distillation system and partially cooling the second part of the compressed and purified air stream; expanding the partially cooled second part of the compressed and purified air stream in a turbine to form an exhaust stream; rectifying the liquid air stream and exhaust stream in a cryogenic 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), the higher pressure column and the lower pressure column being linked in a heat transfer relationship via a condenser reboiler, wherein the rectifying step produces 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 percent and lower than the first oxygen concentration, a nitrogen overhead stream from the lower pressure column; and
a condensed nitrogen stream from the condenser-reboiler;rectifying an oxygen-argon stream extracted from the lower pressure column in an argon column arrangement, the argon column arrangement having at least one argon column and an argon condenser and wherein the argon column is configured to produce a third oxygen enriched bottoms stream and an argon-enriched overhead; subcooling a fourth oxygen enriched kettle stream from the higher pressure column and the condensed nitrogen stream from the condenser-reboiler via indirect heat exchange with the nitrogen overhead stream from the lower pressure column; returning the third oxygen enriched bottoms stream from the argon column to the lower pressure column; directing the argon-enriched overhead from the argon column to an argon condenser; condensing the argon-enriched overhead in the argon condenser against the second oxygen enriched stream from the lower pressure column to produce a crude argon stream or a product argon stream, an argon reflux stream and an oxygen enriched waste stream; wherein the method produces one or more high purity nitrogen products; wherein the method recovers greater than 75 percent of the argon in the feed air stream if the argon is condensed against the first oxygen enriched stream and recover greater than 30 percent of the argon in the feed air stream if the argon is condensed against the second oxygen enriched stream; and wherein the method recovers greater than 98 percent of the nitrogen in the feed air stream and produces one or more high purity 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). - View Dependent Claims (20, 21)
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Specification