EP0384688A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Air separation
Assignee: BOC Group Ltd
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Filing: 1990-02-19
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Granted: —
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Expires: 2010-02-19
Abstract
Abstract Compressed air is purified in apparatus 4 and passed through heat exchanger 6 in which it is reduced in temperature ready for rectification in a double column comprising a higher pressure rectification column 10 and a lower pressure rectification column 12 which are linked by a condenser-reboiler 14. The air is separated in the column 10 into oxygen-rich and nitrogen fractions. The oxygen-rich fraction is separated in the lower pressure column 12 into an oxygen and a lower pressure nitrogen product. Liquid nitrogen from the higher pressure column 10 is used as reflux in the lower pressure column 12, and a gaseous nitrogen stream is withdrawn from the column 10 as higher pressure nitrogen product. In order to compensate for the resulting loss of reflux in the column 12, a part of the lower pressure nitrogen product stream is compressed in compressor 38, cooled by passage through heat exchanger 6, and condensed in condenser 40. The resulting condensate provides additional reflux in the column 12. This arrangement makes possible enhanced power recovery from nitrogen produced in an air separation plant providing an oxygen product at an elevated pressure.
Inventors
- 👤 Thomas Rathbone
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 23:44
CPC Classifications
F; F25; F25J; F25J3/00; F25J3/02; F25J3/04; F25J3/04521; F25J3/04593; F25J3/046; F25J3/04248; F25J3/04284; F25J3/0429; F25J3/04303; F25J3/04333; F25J3/04351; F25J3/04406; F25J3/04412; F25J3/04563; F25J3/04575; F25J2200/00; F25J2200/20; F25J2240/00; F25J2240/80; F25J2250/00; F25J2250/30; F25J2250/42; F25J2250/52; Y; Y10; Y10S; Y10S62/00; Y10S62/915; Y10S62/939
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
208 words
A method of separating air comprising: (a) removing carbon dioxide and water vapour from a compressed air feed stream and reducing the temperature of at least part of the thus purified feed stream to a level suitable for its separation by rectification at cryogenic temperatures; (b) introducing the thus cooled air stream into a higher pressure rectification column, providing liquid nitrogen reflux for the higher pressure rectification column, and separating the air therein into oxygen-enriched and nitrogen-enriched fractions; (c) withdrawing a liquid stream of oxygen-enriched fraction from the higher pressure column and passing it into a lower pressure rectification column in which it is separated into oxygen and nitrogen; (d) withdrawing a nitrogen stream and a product oxygen stream from the lower pressure rectification column; (e) withdrawing a liquid stream of nitrogen-enriched fraction from the higher pressure column and employing it as reflux in the lower pressure column; (f) reboiling liquid oxygen in or from the lower pressure column; (g) taking at least part of the said nitrogen stream, compressing it, cooling it, at least partially condensing it, and employing the resulting liquid nitrogen as additional reflux in the lower pressure column; and (h) withdrawing a gaseous product stream of said nitrogen-enriched fraction from the higher pressure column.
Claim 2
Independent Claim
208 words
A method of separating air comprising: (a) removing carbon dioxide and water vapour from a compressed air feed stream and reducing the temperature of at least part of the thus purified feed stream to a level suitable for its separation by rectification at cryogenic temperatures; (b) introducing the thus cooled air stream into a higher pressure rectification column, providing liquid nitrogen reflux for the higher pressure rectification column, and separating the air therein into oxygen-enriched and nitrogen-enriched fractions; (c) withdrawing a liquid stream of oxygen-enriched fraction from the higher pressure column and passing it into a lower pressure rectification column in which it is separated into oxygen and nitrogen; (d) withdrawing a nitrogen stream and a product oxygen stream from the lower pressure rectification column; (e) withdrawing a liquid stream of nitrogen-enriched fraction from the higher pressure column and employing it as reflux in the lower pressure column; (f) reboiling liquid oxygen in or from the lower pressure column; (g) taking at least part of the said nitrogen stream, compressing it, cooling it, at least partially condensing it, and employing the resulting liquid nitrogen as additional reflux in the lower pressure column; and (h) withdrawing a gaseous product stream of said nitrogen-enriched fraction from the higher pressure column.
Claim 3
Dependent Claim
26 words
A method according to Claim 1, in which the compressed air feed stream is at a pressure in the range of 8 to 13 atmospheres absolute.
Claim 4
Dependent Claim
25 words
A method according to Claim 1 or Claim 2, in which the air stream is taken from the air feed stream to a gas turbine.
Claim 5
Independent Claim
35 words
A method according to any one of the preceding claims, in which at least part of the said gaseous product stream of said nitrogen-enriched fraction is further compressed and then has power recovered from it.
Claim 6
Independent Claim
48 words
A method according to any one of the preceding claims, in which the remainder of the nitrogen stream withdrawn from the lower pressure column is employed to purge water and carbon dioxide from apparatus used to remove such water and carbon dioxide from the compressed air feed stream.
Claim 7
Independent Claim
38 words
A method according to any one of the preceding claims, in which at least part of the remainder of the nitrogen stream withdrawn from the lower pressure column is further compressed and then has power recovered from it.
Claim 8
Independent Claim
52 words
A method according to any one of the preceding claims, in which the at least partial condensation of the said part of the nitrogen stream is effected by heat exchange with part of the said oxygen-enriched liquid stream, the oxygen-rich liquid being itself reboiled and then introduced into the lower pressure column.
Claim 9
Independent Claim
44 words
A method according to any one of the preceding claims, in which refrigeration is generated by expanding a minor part of the purified compressed air stream in a turbine, at least part of the resulting expanded air being introduced into the lower pressure column.
Claim 10
Dependent Claim
180 words
Apparatus for separating air, comprising: (a) means for separating carbon dioxide and water vapour from a compressed feed air stream; (b) heat exchange means for reducing the temperature of at least part of the thus purified air stream to be level suitable for separation by cryogenic rectification; (c) a higher pressure rectification column in communication with the lower temperature end of the passage through the heat exchange means for the air stream; the higher pressure rectification column having an inlet for liquid nitrogen reflux, an outlet for a stream of nitrogen-enriched fraction and another outlet for a liquid stream of oxygen-enriched fraction; (d) a lower pressure rectification column having an inlet in communication with the said outlet for the liquid stream of oxygen-enriched fraction and having outlets for separate oxygen and nitrogen streams; (e) means for reboiling liquid oxygen in or from the lower pressure column; (f) a compressor for compressing a stream of warmed nitrogen-enriched fraction; and (g) a condenser for condensing said compressed nitrogen stream and means for combining the resulting liquid nitrogen with the liquid nitrogen reflux.
Claim 11
Dependent Claim
180 words
Apparatus for separating air, comprising: (a) means for separating carbon dioxide and water vapour from a compressed feed air stream; (b) heat exchange means for reducing the temperature of at least part of the thus purified air stream to be level suitable for separation by cryogenic rectification; (c) a higher pressure rectification column in communication with the lower temperature end of the passage through the heat exchange means for the air stream; the higher pressure rectification column having an inlet for liquid nitrogen reflux, an outlet for a stream of nitrogen-enriched fraction and another outlet for a liquid stream of oxygen-enriched fraction; (d) a lower pressure rectification column having an inlet in communication with the said outlet for the liquid stream of oxygen-enriched fraction and having outlets for separate oxygen and nitrogen streams; (e) means for reboiling liquid oxygen in or from the lower pressure column; (f) a compressor for compressing a stream of warmed nitrogen-enriched fraction; and (g) a condenser for condensing said compressed nitrogen stream and means for combining the resulting liquid nitrogen with the liquid nitrogen reflux.
Claim 12
Dependent Claim
33 words
Apparatus according to Claim 9, in which the separating means has an inlet communicating with the outlet of an air compressor adapted to supply air to a combination chamber of a gas turbine.
Claim 13
Dependent Claim
29 words
Apparatus according to Claim 10, in which the combustion chamber is adapted to receive at least part of the said stream of nitrogen-enriched fraction upstream of said combustion chamber.
Claim 14
Dependent Claim
25 words
Apparatus according to Claim 11, including a further compressor for compressing said part of the said stream of nitrogen-enriched fraction upstream of said combustion chamber.
References Cited (Backward Citations)
No citation records indexed.
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