Patent US4968337A successfully refreshed from Google Patents.
US4968337A
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Air separation
Assignee: BOC Group Ltd
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Filing: 1989-09-29
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Granted: 1990-11-06
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Expires: 2009-09-29
Abstract
Abstract An improved process and apparatus for separating air to form oxygen and nitrogen in at least one cryogenic distillation column is disclosed. Nitrogen vapor taken from the colunm is warmed in countercurrent flow to incoming air in a heat exchanger wherein compressed air is being cooled for separation. A portion of the warm nitrogen is compressed, cooled in the heat exchanger and passed through an expansion turbine. The expanded nitrogen is passed through a reboiler associated with the column and further cooled in the heat exchange means. Part of the resulting liquid nitrogen is used to provide reflux for the column and the remainder is taken as product. Preferably, at least a portion of the compressed air stream is expanded in a turbine, passed through the reboiler associated with the column to provide reboil therefor, liquified by heat exchange and introduced to the distillation column through a throttling valve. Further, an argon product can be recovered by withdrawing an argon-rich stream from a distillation column and passing it to a further column for purification. Vapor from the distillation column, or another in a plurality of distillation columns, is used to provide reflux for the further column with the resulting condensed vapor being returned to the column from which it was withdrawn.
Inventors
- 👤 David J. Layland
- 👤 John T. Lavin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 05:58
CPC Classifications
F; F25; F25J; F25J3/00; F25J3/02; F25J3/04; F25J3/04248; F25J3/04284; F25J3/04309; F25J3/04151; F25J3/04187; F25J3/04193; F25J3/042; F25J3/04278; F25J3/0429; F25J3/04296; F25J3/04327; F25J3/04333; F25J3/04351; F25J3/04357; F25J3/04375; F25J3/04393; F25J3/044; F25J3/04642; F25J3/04648; F25J3/04654; F25J3/0466; F25J2200/00; F25J2200/38; F25J2200/50; F25J2205/00; F25J2205/02; F25J2215/00; F25J2215/50; F25J2250/00; F25J2250/20; F25J2270/00; F25J2270/02; F25J2270/60; F25J2270/90; Y; Y10; Y10S; Y10S62/00; Y10S62/923; Y10S62/924
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
141 words
A process of separating air comprising: removing carbon dioxide and water vapor from compressed air; cooling the compressed air in heat exchange means to a temperature suitable for cryogenic distillation; separating the air into nitrogen and oxygen in at least one cryogenic distillation column; warming nitrogen vapor withdrawn from the column countercurrently to the air in the heat exchange means; compressing a portion of the warmed nitrogen; cooling the compressed nitrogen in said heat exchange means, expanding at least a portion of the cooled nitrogen in a turbine; passing the expanded nitrogen through a reboiler associated with said distillation column to provide reflux for the distillation; subjecting nitrogen leaving the reboiler to further cooling in the heat exchange means to liquify it; employing a portion of the resulting liquid nitrogen as reflux in the distillation and withdrawing the remainder as product.
Claim 2
Dependent Claim
141 words
A process of separating air comprising: removing carbon dioxide and water vapor from compressed air; cooling the compressed air in heat exchange means to a temperature suitable for cryogenic distillation; separating the air into nitrogen and oxygen in at least one cryogenic distillation column; warming nitrogen vapor withdrawn from the column countercurrently to the air in the heat exchange means; compressing a portion of the warmed nitrogen; cooling the compressed nitrogen in said heat exchange means, expanding at least a portion of the cooled nitrogen in a turbine; passing the expanded nitrogen through a reboiler associated with said distillation column to provide reflux for the distillation; subjecting nitrogen leaving the reboiler to further cooling in the heat exchange means to liquify it; employing a portion of the resulting liquid nitrogen as reflux in the distillation and withdrawing the remainder as product.
Claim 3
Dependent Claim
21 words
A process in accordance with claim 1, wherein the reboiler is associated with the distillation column for which reflux is provided.
Claim 4
Dependent Claim
32 words
A process in accordance with claim 1, wherein a portion of the nitrogen vapor withdrawn from said distillation column is compressed, after warming, to a pressure in excess of its critical pressure.
Claim 5
Dependent Claim
39 words
A process in accordance with claim 3, wherein the portion of the compressed nitrogen taken for expansion is at a pressure of from about 50 to 75 atmospheres and at a temperature of from about 150 to 170 K.
Claim 6
Dependent Claim
36 words
A process in accordance with claim 1, wherein a portion of the compressed nitrogen is liquefied without being subjected to expansion in said turbine and without being passed through the reboiler associated with said distillation column.
Claim 7
Dependent Claim
29 words
A process in accordance with claim 1, wherein at the completion of expansion in the turbine, the nitrogen has a pressure of from about 12 to 20 atmospheres absolute.
Claim 8
Dependent Claim
24 words
A process in accordance with claim 6, wherein the nitrogen at the completion of expansion in the turbine is in the saturated vapor state.
Claim 9
Dependent Claim
52 words
A process in accordance with claim 1, wherein at least a portion of the nitrogen withdrawn from the reboiler in the liquid state is sub-cooled in the heat exchange means and is then subjected to a plurality of flash separation steps to form liquid nitrogen and a plurality of flash gas streams.
Claim 10
Dependent Claim
17 words
A process in accordance with claim 8, wherein the nitrogen is subjected to three flash separation steps.
Claim 11
Dependent Claim
52 words
A process in accordance with claim 1, wherein refrigeration is provided for the heat exchange means by withdrawing a waste nitrogen vapor stream from the distillation column, increasing the temperature thereof in the heat exchange means, subjecting it to expansion in a turbine, and passing the gas through the heat exchange means.
Claim 12
Dependent Claim
57 words
A process in accordance with claim 1, wherein refrigeration for the heat exchange means between ambient temperature and the temperature of the compressed nitrogen when it is introduced into the turbine is provided by a mixed hydrocarbon refrigerant cycle or by a two-stage refrigeration cycle consisting of a nitrogen working fluid cycle and a fluorocarbon refrigerant cycle.
Claim 13
Dependent Claim
23 words
A process in accordance with claim 1, wherein a gaseous nitrogen product and an oxygen product are also produced in the distillation column.
Claim 14
Dependent Claim
37 words
A process in accordance with claim 1, additionally including the step of withdrawing a stream of argon-enriched fluid from the distillation column and subjecting it to separation in a further distillation column to provide an argon product.
Claim 15
Dependent Claim
79 words
A process in accordance with claim 1, additionally including the steps of expanding at least a portion of said stream of compressed air which has been cooled in the heat exchange means in a turbine, passing the expanded stream through the reboiler for the distillation column to provide a reboil therefor, passing the air stream through the heat exchange means to form a sub-cooled liquid air stream and introducing said stream into the distillation column through a throttling valve.
Claim 16
Dependent Claim
34 words
A process in accordance with claim 14, wherein said air stream is introduced into the distillation column comprises from about 5 to 10 percent of the total air introduced into said column for separation.
Claim 17
Dependent Claim
157 words
Apparatus for separating air comprising at least one compressor for compressing air, means for removing carbon dioxide and water vapor from the compressed air, heat exchange means for reducing the temperature of the air to a temperature suitable for its separation by cryogenic distillation, at least one cryogenic distillation column for separating air into oxygen and nitrogen, an outlet for nitrogen vapor from said distillation column in fluid communication with the inlet of at least one nitrogen compressor via said heat exchange means, at least one expansion turbine having an inlet in fluid communication with the outlet of said nitrogen compressor via said heat exchange means, and an outlet in fluid communication with an inlet to a reboiler associated with said distillation column, said reboiler having an outlet in fluid communication via said heat exchange means with means for providing liquid nitrogen and reflux for said distillation column and also with an outlet for product liquid nitrogen.
Claim 18
Dependent Claim
157 words
Apparatus for separating air comprising at least one compressor for compressing air, means for removing carbon dioxide and water vapor from the compressed air, heat exchange means for reducing the temperature of the air to a temperature suitable for its separation by cryogenic distillation, at least one cryogenic distillation column for separating air into oxygen and nitrogen, an outlet for nitrogen vapor from said distillation column in fluid communication with the inlet of at least one nitrogen compressor via said heat exchange means, at least one expansion turbine having an inlet in fluid communication with the outlet of said nitrogen compressor via said heat exchange means, and an outlet in fluid communication with an inlet to a reboiler associated with said distillation column, said reboiler having an outlet in fluid communication via said heat exchange means with means for providing liquid nitrogen and reflux for said distillation column and also with an outlet for product liquid nitrogen.
Claim 19
Dependent Claim
31 words
Apparatus in accordance with claim 16, additionally including means for subjecting liquid nitrogen leaving the reboiler to a plurality of flash separating steps intermediate of the reboiler and said distillation column.
Claim 20
Dependent Claim
28 words
Apparatus in accordance with claim 17, wherein said means for subjecting the liquid nitrogen to a plurality of flash separation steps include at least three flash separation stages.
Claim 21
Dependent Claim
46 words
Apparatus in accordance with claim 16, including an outlet from said distillation a column for withdrawing a waste nitrogen stream, and means for employing the waste nitrogen stream in a refrigeration cycle to provide refrigeration for the heat exchange means, said means including an expansion turbine.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-11-05 | 1994-05-07 | 1994-11-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-11-05 | 1998-05-07 | 1998-11-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-11-05 | 2002-05-07 | 2002-11-06 | $7700.00 | Window Closed / Lapsed |