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Publication numberUS2915882 A
Publication typeGrant
Publication dateDec 8, 1959
Filing dateApr 23, 1956
Priority dateMay 31, 1955
Publication numberUS 2915882 A, US 2915882A, US-A-2915882, US2915882 A, US2915882A
InventorsLittlewood Anthony Duncan, Schuftan Paul Maurice
Original AssigneeBritish Oxygen Co Ltd
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Separation of air
US 2915882 A
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Description  (OCR text may contain errors)

Dec. 8, 1959 P. M. SCHUFTAN ET AL 2,915,382

SEPARATION OF AIR Filed April 23, 1956 RESSOR I nventor Attorney 2,915,882 SEPARATION or AIR Paul Maurice Schuftan, Richmond Hill, and Anthony Duncan Littlwood, Wbiidfoid Green, England, as-

ors to The British Oxygen Company Limited, a British company Application April 23, 1956, Serial No. 579,932 Claims priority, application Great Britain May 31, 1955 Claims. (Cl. 62-30) The present invention relates to air separation and more particularly to a process of the type in which air is compressed, cooled, expanded and subjected to rectification to produce a liquid oxygen fraction and a gaseous nitrogen fraction.

The oxygen fraction is frequently required to be delivered in the gaseous phase under pressure and it has been proposed to pump the liquid oxygen fraction under pressure and to vaporize the liquid by heat interchange with the incoming air, the whole of the air to be separated being compressed to a uniform and relatively high pressure.

It is an object of this invention to provide for producing a compressed gaseous oxygen fraction, an air separation process having enhanced thermodynamic efliciency as compared with other processes of this type hitherto proposed.

According to this invention, an air separation process of the type specified comprises establishing a major air stream and a minor air stream, compressing the major air stream only to a relatively low pressure sufficient on expansion with the performance of external work to cover the greater part of the cold requirements of the process, compressing the minor stream to a relatively high pressure, sufficient to recover by heat exchange the cold conent of the separated compressed liquid oxygen fraction, and passing the compressed minor air stream in heat exchange relationship With the compressed liquid oxygen fraction prior to the expansion of the minor air stream.

Preferably the whole of the major stream is expanded with the performance of external work, for example, in a turbine, while the minor stream, after being cooled by heat transfer with the compressed liquid oxygen fraction, is expanded isenthalpically. The two streams after expansion are passed into a double rectification system operating in known manner to produce the required liquid oxygen fraction and a gaseous nitrogen fraction.

The invention will now be more particularly described with reference to the accompanying drawing which shows diagrammatically one method of carrying out the invention.

Air is drawn into the compressor 1 through a pipe 2, compressed therein to about atmospheres absolute pressure, and then passed through a vessel 3 where carbon dioxide is removed by scrubbing, into exchanger 4 where the air is cooled to a temperature of about 253 K. with simultaneous removal of water vapour, the cooling and drying agent being the separated gaseous nitrogen fraction. In the drawing, the whole of the gaseous nitrogen fraction is shown as passing through the exchanger 4, but, if desired, only a part of this fraction may be so treated.

The air leaving the exchanger 4 is then split into two streams. One stream is further compressed to about 80 atmospheres absolute pressure in a compressor 5 and dried in vessel 6 from which it passes through an exchanger 7 in countercurrent flow to the separated liquid V United States Patent 0 2,915,882 Patented Dec. 8, 1959' ice oxygen fraction which cools it to a temperature of about 116 K. This air is further cooled in an exchanger 8' separated gaseous nitrogen fraction, leaving them at a. temperature of about 213 K. and is further cooled to about 118 K. in an exchanger 13 by the separated gas eous nitrogen fraction. This air stream is finally expanded in the turbine 14 to a pressure of 5.5 atmos= pheres absolute and a temperature of about 100 K. and.

is introduced into the scrubber 10 to admix With the first.

air stream.

From the scrubber 10 the liquid and vapour fractions of the cooled and expanded air are introduced into the upper and lower columns 16 and 15 respectively, of at double column system, to efiect separation into a liquid. oxygen fraction and a gaseous nitrogen fraction in known:

manner.

The gaseous nitrogen fraction leaving the top of the upper column 16 is first used to cool the liquid nitrogen: stream leaving the lower column 15 to act as reflux in: the upper column 16, in an exchanger 17 in the manner well known in the art. The effluent gaseous nitrogen fraction then passes through the exchangers 8, 13, 11 or 12 and 4 as hereinbefore described in order to cool the incoming air streams.

If a pure nitrogen fraction is required, this can be obtained from the top of the upper column 16 by withdrawing an impure nitrogen stream from a lower position in the upper column in known manner. The two nitrogen streams are then directed through separate sets of exchangers in a similar manner to that hereinbefore described.

The liquid oxygen fraction withdrawn from the bottom of the upper column 16 is compressed to about 20 atmospheres absolute pressure by means of a liquid pump 18, and the compressed liquid is vaporized and the resulting vapour heated in the exchanger 7 by heat exchange with the stream of air compressed to atmospheres absolute pressure as previously described.

By this means, a gaseous oxygen stream at a desired pressure is obtained in a highly efficient manner.

We claim:

1. Process for the separation of air to produce a compressed gaseous oxygen fraction and a gaseous nitrogen fraction which comprises the steps of compressing the air to a relatively low pressure, cooling the compressed air by heat exchange with at least a part of at least one of the separation products, dividing said cooled air into a major air stream and a minor air stream, expanding the whole of said major air stream with the production of external work, whereby an amount of cold is produced suflicient to satisfy the greater part of the cold requirements ofthe process, compressing said minor air stream to a relatively high pressure, cooling the whole of said compressed minor air stream by heat exchange with a liquid oxygen fraction pumped under pressure, whereby said liquid oxygen fraction is vaporized to produce the required compressed gaseous oxygen fraction, expanding said cooled minor air stream, subjecting said expanded major and minor air streams to rectification to separate therefrom a gaseous nitrogen fraction and a liquid oxygen fraction and pumping said liquid oxygen fraction under pressure to produce the liquid oxygen fraction which is vaporized by heat exchange with the compressed minor air stream.

2. Process for the separation of air to produce a compressed gaseous oxygen fraction and a gaseous nitrogen sufiicient to. satisfy the greater part of the cold requirements of the process, compressing said minor air stream :to a relatively high pressure, cooling the whole of said'mie nor air stream byheat exchangewith a liquid oxygen frac- .tion pumped under pressure, whereby said liquid oxy- -gen fraction is vaporized to produce the required compressed gaseous oxygen fraction,,isenthalpically expanding said cooled minor air stream, subjecting said expanded major and minor air streams to rectification to separate therefrom a gaseous nitrogen fraction and a liquid, oxygen fraction and pumping said liquid oxygen fraction under pressure to produce the liquid oxygen fraction which is vaporized by heat exchange with the compressed minor air stream.

Q3. Process for the separation of air to produce a compressed gaseous oxygen fraction and a gaseous nitrogen fraction which comprises the steps of compressing the air to a relatively low pressure, cooling the compressed air by heat exchange with at least a part of the separated gaseous nitrogen fraction, dividing said cooled air into a major air stream and a minor air stream, expand- 1 ing the whole of said major air stream with the produc tion of external work, whereby an amount of coldris pro-- dluced sufficient to satisfy the greater part of. the cold requirements of the process, compressing said minor air :stream to a relatively high pressure, cooling the whole of said minor air stream by heat exchange with a liquid oxygenfraction pumped under pressure, whereby said liquid oxygen fraction is vaporized to produce the required compressed gaseous oxygen fraction, isenthalpical- 1y expanding said cooled minor air stream, subjecting said expanded major and minor air streams to rectification to separate therefrom a gaseous nitrogen fraction and a liquid oxygen fraction and pumping said liquid oxygen fraction under pressure to produce the liquid oxygen fraction which is vaporized byheat exchange with, the compressed minor air stream.

4. Process for the separation of air to produce a com pressed gaseous oxygen fraction and a gaseous nitrogen fraction which comprises the steps of compressing, the air to a relatively low pressure, cooling the compressed .air by heat exchange with at least a part of the separated gaseous nitrogen fraction dividing said cooled'air into a major air stream and a minor air stream, furthercooling said major air stream by heat exchange with said separated gaseous nitrogen fraction, expanding the .whole of said cooled major air stream with the productionof external work, whereby an amount of cold isrproduced sufiicient to, satisfy the greater part of the cold require-,.

ments of the process, compressing said minor air stream to a relatively high pressure, cooling the whole of said compressed minor air stream by heat exchange with a liquid oxygen fraction pumped. under pressure, wherev by said liquid oxygen fraction is vaporized to produce the required compressed gaseous .oxygen fraction, isenthalpically expanding said cooled minor air stream, subjecting said expanded major and minor air streams to rectification to separate therefrom a gaseous nitrogen fraction and a liquid oxygen fraction and pumping said liquid oxygen fraction under pressure to produce the 7 liquid oxygen fraction which isvaporized by heat exchange with the compressed minor air stream. V

5. Process for the separation of air to produce a compressed gaseous oxygen fraction and-a gaseous nitrogen fraction which comprises the steps of compressing the air to a relatively low pressure, cooling the compressed air 'by heat exchange with at least a part of the separatedgaseous nitrogen fraction dividing sa'id cooled air'into a major air stream and; a minor air stream, further cooling said major air stream by heat exchange with said:

separatedgaseous nitrogen fraction, expanding the whole of said cooled major air stream with the production of external work, whereby an amount of cold is'produced'.

sufiicient to satisfy the greater part of the cold requirements of theprocess, compressing said minor air stream to 3.,I'tilfltlV6lY- high pressure, cooling the whole of said minor air stream by heat exchangewith a liquid oxygen fraction pumped under pressure, whereby said liquid oxygen fraction is vaporized to produce the required compressed gaseous oxygen fraction, further cooling said. compressed minor air stream by heat exchange with said! separated gaseous nitrogen fraction, isenthalpically ex panding said cooled-minor air stream, subjecting said expanded major and minor air streams to rectification to separate therefrom a gaseous nitrogen fraction and a: liquid oxygen fraction and pumping said liquid oxygen fraction under pressure to produce the liquid. oxygen fraction which is vaporized by heat exchange with the compressed minor air stream.

References Cited in the file of this patent UNITED STATES PATENTS 2,209,748 Schlitt July 30, 19.40 2,239,883 Bauflre et'al. Apr. 29, 1941 2,409,458 Van Nuys Oct. 15, 1946 2,411,680 Dennis Nov. 26, 1946 2,685,183 Collins Aug. 3, 1954 2,699,047 Karwat Jan. 11, 1955' 2,712,738 Wucherer July 12, 1955 FOREIGN PATENTS 4 6 9,939 Great Britain Aug. 3, 1937

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2209748 *Aug 3, 1938Jul 30, 1940Air ReductionMethod of separating the constituents of gaseous mixtures
US2239883 *Mar 4, 1936Apr 29, 1941said De Baufre Original application March 4Expansion engine
US2409458 *Apr 27, 1943Oct 15, 1946Air ReductionSeparation of the constituents of gaseous mixtures
US2411680 *Mar 7, 1944Nov 26, 1946Air ReductionSeparation of the constituents of gaseous mixtures
US2685183 *Oct 1, 1953Aug 3, 1954Joy Mfg CoMethod of and means for treating gases
US2699047 *Oct 27, 1950Jan 11, 1955Linde Eismasch AgProcess for cooling and purifying compressed gas mixtures
US2712738 *Jan 2, 1953Jul 12, 1955Linde S Eismaschinen AgMethod for fractionating air by liquefaction and rectification
GB469939A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3100696 *Jun 8, 1959Aug 13, 1963Linde Eismasch AgMethod and apparatus for separating gases
US3143406 *Aug 10, 1961Aug 4, 1964Linde Eismasch AgSystem for conducting heat exchange operations in a gas separation apparatus incorporating periodically reversible regenerators
US3214925 *Aug 10, 1961Nov 2, 1965Linde Eismasch AgSystem for gas separation by rectification at low temperatures
US3261168 *Nov 2, 1962Jul 19, 1966Petrocarbon Dev LtdSeparation of oxygen from air
US3383873 *Nov 3, 1965May 21, 1968Linde AgEngine expansion of liquefied gas at below critical temperature and above critical pressure
US3397138 *Dec 2, 1965Aug 13, 1968Warren Petroleum CorpGas separation employing work expansion of feed and fractionator overhead
US3416323 *Jan 13, 1967Dec 17, 1968Linde AgLow temperature production of highly compressed gaseous and/or liquid oxygen
US3447332 *Jul 13, 1967Jun 3, 1969Genrikh Maxovich BasinAir separation employing separated nitrogen as heat exchange fluid in liquid oxygen pump jacket
US4964901 *May 19, 1989Oct 23, 1990Linde AktiengesellschaftLow-temperature separation of air using high and low pressure air feedstreams
US5082482 *Sep 18, 1990Jan 21, 1992L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges ClaudeProcess and apparatus for the production of gaseous oxygen with a variable flow by air distillation
US5098456 *Jun 27, 1990Mar 24, 1992Union Carbide Industrial Gases Technology CorporationDistillation, condensation, expansion and separation with withdrawal
US5108476 *Jun 27, 1990Apr 28, 1992Union Carbide Industrial Gases Technology CorporationCryogenic air separation system with dual temperature feed turboexpansion
US5114452 *Jun 27, 1990May 19, 1992Union Carbide Industrial Gases Technology CorporationCryogenic air separation system for producing elevated pressure product gas
US5148680 *Jun 27, 1990Sep 22, 1992Union Carbide Industrial Gases Technology CorporationPassing nitrogen-enriched liquid produced by the condensation of nitrogen-enriched vapor against oxygen-rich liquid in indirect heat exchange with feed air to produce nitrogen gas
US5379598 *Aug 23, 1993Jan 10, 1995The Boc Group, Inc.Oxygen
Classifications
U.S. Classification62/646
International ClassificationF25J3/04
Cooperative ClassificationF25J3/04406, F25J3/04296, F25J3/04412, F25J2205/30, F25J3/04218, F25J3/04242, F25J3/0409
European ClassificationF25J3/04C6A2, F25J3/04A6O, F25J3/04F2, F25J3/04B8, F25J3/04B6P, F25J3/04F