US4299607A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for recovering nitrogen in low pressure type air separation apparatus
Assignee: Hitachi Ltd
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Filing: 1980-05-14
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Granted: 1981-11-10
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Expires: 2000-05-14
Abstract
Abstract In a low pressure type air separation apparatus provided with a reversing heat exchanger for removing water vapor and carbon dioxide gas in feed air, a nitrogen gas taken out of a high pressure column in a duplex type rectification tower is led to an expander for generating subcooling for the air separation apparatus, and the effluent nitrogen gas is obtained under a predetermined pressure by controlling a pressure of the effluent gas from the expander. The effluent nitrogen gas is adjusted to a temperature satisfactory for the inlet temperature conditions for the reversing heat exchanger by passing the effluent nitrogen gas through a heat exchanger, and then is passed through the reversing heat exchanger, whereby the effluent gas from the reversing exchanger is obtained as a product nitrogen gas under a predetermined pressure.
Inventors
- 👤 Michimasa Okabe
- 👤 Shozi Koyama
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 14:06
CPC Classifications
F; F25; F25J; F25J3/00; F25J3/02; F25J3/04; F25J3/04406; F25J3/04412; F25J3/04151; F25J3/04187; F25J3/04193; F25J3/04248; F25J3/04284; F25J3/04309; F25J3/04763; F25J3/04769; F25J3/04781; F25J3/04812; F25J3/04818; F25J2205/00; F25J2205/24; F25J2245/00; F25J2245/40; F25J2250/00; F25J2250/30; F25J2250/40; F25J2250/42; Y; Y10; Y10S; Y10S62/00; Y10S62/928
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
159 words
A process for recovering a product nitrogen gas in a low pressure type air separation apparatus provided with a reversing heat exchanger and a duplex type rectification tower having a high pressure column and a low pressure column, which comprises leading a nitrogen gas taken out of said high pressure column of said duplex type rectification tower to an expander for generating subcooling for the air separation apparatus, taking out the nitrogen gas from the outlet of the expander under a pressure higher than the pressure of a nitrogen gas to be taken out of said low pressure column of said duplex type rectification tower, adjusting the temperature of the nitrogen gas from the expander to a necessary inlet temperature for the reversing heat exchanger by passage through a heat exchanger, then passing the temperature adjusted nitrogen gas through the reversing heat exchanger, and taking the nitrogen gas out of the reversing heat exchanger as said product nitrogen gas.
Claim 2
Dependent Claim
159 words
A process for recovering a product nitrogen gas in a low pressure type air separation apparatus provided with a reversing heat exchanger and a duplex type rectification tower having a high pressure column and a low pressure column, which comprises leading a nitrogen gas taken out of said high pressure column of said duplex type rectification tower to an expander for generating subcooling for the air separation apparatus, taking out the nitrogen gas from the outlet of the expander under a pressure higher than the pressure of a nitrogen gas to be taken out of said low pressure column of said duplex type rectification tower, adjusting the temperature of the nitrogen gas from the expander to a necessary inlet temperature for the reversing heat exchanger by passage through a heat exchanger, then passing the temperature adjusted nitrogen gas through the reversing heat exchanger, and taking the nitrogen gas out of the reversing heat exchanger as said product nitrogen gas.
Claim 3
Dependent Claim
74 words
A process according to claim 1, wherein the temperature of the nitrogen gas from the expander is adjusted to the necessary inlet temperature for the reversing heat exchanger by heat exchange with feed air to be supplied to the high pressure column of duplex type rectification tower or liquefied air of the high pressure column passed through said heat exchanger, depending upon the degree of the temperature of the nitrogen gas from the expander.
Claim 4
Dependent Claim
64 words
A process according to claim 2, wherein the temperature of the nitrogen gas from the expander is adjusted to the necessary inlet temperature of the reversing heat exchanger by heat exchange with feed air to be supplied to the high pressure column of duplex type rectification tower when the temperature of the nitrogen gas from the expander is less than the necessary inlet temperature.
Claim 5
Dependent Claim
58 words
A process according to claim 2 or 3, wherein the temperature of the nitrogen gas from the expander is adjusted to the necessary inlet temperature for the reversing heat exchanger by heat exchange with liquefied air of the high pressure column when the temperature of the nitrogen gas from the expander is greater than the necessary inlet temperature.
Claim 6
Dependent Claim
30 words
A process according to claim 1 or 2, wherein the pressure of the nitrogen gas from the expander is adjusted so that the product nitrogen gas has a predetermined pressure.
Claim 7
Dependent Claim
28 words
A process according to claim 1 or 2, wherein the nitrogen gas rate from the expander is adjusted so that the product nitrogen gas has a predetermined rate.
Claim 8
Dependent Claim
22 words
A process according to claim 2, wherein passage of said feed air or said liquefied air through said heat exchanger occurs automatically.
References Cited (Backward Citations)
US3736762A
Cited
US3735599A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-11-09 | 1985-05-11 | 1985-11-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-11-09 | 1989-05-11 | 1989-11-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-11-09 | 1993-05-11 | 1993-11-10 | $7700.00 | Window Closed / Lapsed |