GB2061478A - Method and cryogenic plant for producing gaseous oxygen - Google Patents

Method and cryogenic plant for producing gaseous oxygen Download PDF

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Publication number
GB2061478A
GB2061478A GB7936637A GB7936637A GB2061478A GB 2061478 A GB2061478 A GB 2061478A GB 7936637 A GB7936637 A GB 7936637A GB 7936637 A GB7936637 A GB 7936637A GB 2061478 A GB2061478 A GB 2061478A
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Prior art keywords
pressure column
oxygen
pipe
high pressure
heat exchanger
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GB7936637A
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GB2061478B (en
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Air Products and Chemicals Inc
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Air Products and Chemicals Inc
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Priority to EP80303721A priority patent/EP0029656A1/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04078—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression
    • F25J3/04103—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression using solely hydrostatic liquid head
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04078—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression
    • F25J3/0409—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression of oxygen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
    • F25J3/04157—Afterstage cooling and so-called "pre-cooling" of the feed air upstream the air purification unit and main heat exchange line
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
    • F25J3/04187—Cooling of the purified feed air by recuperative heat-exchange; Heat-exchange with product streams
    • F25J3/04193—Division of the main heat exchange line in consecutive sections having different functions
    • F25J3/04206—Division of the main heat exchange line in consecutive sections having different functions including a so-called "auxiliary vaporiser" for vaporising and producing a gaseous product
    • F25J3/04212—Division of the main heat exchange line in consecutive sections having different functions including a so-called "auxiliary vaporiser" for vaporising and producing a gaseous product and simultaneously condensing vapor from a column serving as reflux within the or another column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
    • F25J3/04187—Cooling of the purified feed air by recuperative heat-exchange; Heat-exchange with product streams
    • F25J3/04218—Parallel arrangement of the main heat exchange line in cores having different functions, e.g. in low pressure and high pressure cores
    • F25J3/04224—Cores associated with a liquefaction or refrigeration cycle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04284—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams
    • F25J3/04309—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams of nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04333—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using quasi-closed loop internal vapor compression refrigeration cycles, e.g. of intermediate or oxygen enriched (waste-)streams
    • F25J3/04351—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using quasi-closed loop internal vapor compression refrigeration cycles, e.g. of intermediate or oxygen enriched (waste-)streams of nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04406—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system
    • F25J3/04412—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/02—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/24—Processes or apparatus using other separation and/or other processing means using regenerators, cold accumulators or reversible heat exchangers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/30—Processes or apparatus using other separation and/or other processing means using a washing, e.g. "scrubbing" or bubble column for purification purposes
    • F25J2205/32—Processes or apparatus using other separation and/or other processing means using a washing, e.g. "scrubbing" or bubble column for purification purposes as direct contact cooling tower to produce a cooled gas stream, e.g. direct contact after cooler [DCAC]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/30—Processes or apparatus using other separation and/or other processing means using a washing, e.g. "scrubbing" or bubble column for purification purposes
    • F25J2205/34—Processes or apparatus using other separation and/or other processing means using a washing, e.g. "scrubbing" or bubble column for purification purposes as evaporative cooling tower to produce chilled water, e.g. evaporative water chiller [EWC]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2250/00—Details related to the use of reboiler-condensers
    • F25J2250/30—External or auxiliary boiler-condenser in general, e.g. without a specified fluid or one fluid is not a primary air component or an intermediate fluid
    • F25J2250/42—One fluid being nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2250/00—Details related to the use of reboiler-condensers
    • F25J2250/30—External or auxiliary boiler-condenser in general, e.g. without a specified fluid or one fluid is not a primary air component or an intermediate fluid
    • F25J2250/50—One fluid being oxygen

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Emergency Medicine (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Description

1
GB 2 061 478 A 1
SPECIFICATION
Method and Cryogenic Plant for Producing Gaseous Oxygen
This invention relates to a method for 5 producing gaseous oxygen and a cryogenic plant in which said method can be carried out.
In the past large users of gaseous oxygen, such as steel producers, have required their oxygen to be supplied at little more than atmospheric 10 pressure. Accordingly, there are a large number of cryogenic plants available which will produce gaseous oxygen at about 0.2 bars gauge.
More recently we have received enquiries for cryogenic plant capable of producing gaseous 15 oxygen at from 1 to 4 bars gauge. In order to meet this demand we have proposed
(1) using a compressor to compress the gaseous oxygen product to the required pressure; or
20 (2) raising the pressure of the whole cryogenic plant from the main air compressor to the gaseous oxygen output.
Whilst both alternatives satisfy the need, the first alternative has the disadvantage that oxygen 25 compressors are relatively expensive (typically £ 100,000 to £ 180,000) and require special safety precautions. The second alternative is relatively inexpensive in terms of capital expenditure but has the disadvantage that the 30 power consumed by the main air compressor increases drastically.
It is an object of at least preferred embodiments of the present invention to provide a cryogenic plant which is less expensive to 35 construct than alternative (1) and consumes less power than alternative (2).
According to the present invention there is provided a method of producing gaseous oxygen, which method comprises steps of fractionating 40 dry compressed air in a distillation system having a high pressure column operating at between 4 and 8 bars gauge and a low pressure column operating at between 0.3 and 2 bars gauge, and wherein liquid oxygen is withdrawn from the 45 bottom of said low pressure column, is pressurized and is evaporated against a stream of substantially pure nitrogen which has been removed from the top of said high pressure column and compressed to such a pressure that it 50 is at least partially liquified by the evaporation of said oxygen, and wherein at least part of said liquified nitrogen is expanded and returned to said high pressure column as reflux.
Whilst the method of the present invention 55 was specifically developed for providing gaseous oxygen at between 1 and 4 bars gauge, our preliminary investigation suggests that the method can be used for producing gaseous oxygen at much higher pressures, for example 55 60 bars gauge.
The liquid oxygen may be pressurized by a pump or by static head, for example by raising the height of the low pressure column so that the liquid at ground level is just above the required 65 delivery pressure of the gaseous oxygen. Alternatively a combination of static head and pumping may be used. Cryogenic plant using the static head principle will be somewhat taller than their conventional counterparts and for most 70 applications we anticipate that the bottom of the low pressure column will be at least 15 m above ground level.
Preferably, the high pressure column is operated at between 4.5 and 7 bars gauge. 75 Advantageously, the low pressure column is operated at between 0.5 and 2.0 bars gauge.
In terms of cost, the nitrogen compressor required is considerably less expensive that the alternative oxygen compressor. Furthermore there 80 are fewer potential hazards associated with its use. In terms of power consumption for a cryogenic plant designed to produce gaseous oxygen at 1 to 4 bars gauge, the power consumed by preferred embodiments of the present 85 invention is approximately the same as that which would be consumed by a plant using a product oxygen compressor.
The present invention also provides a cryogenic plant for producing gaseous oxygen 90 which plant comprises a high pressure column and a low pressure column for distilling air, an evaporator, a pipe for conveying, in use, liquid oxygen from the bottom of said low pressure column to said evaporator, means to ensure that, 95 in use, the pressure of liquid oxygen at said evaporator is higher than the pressure of liquid oxygen leaving said low pressure column, a pipe for carrying gaseous oxygen from said evaporator, a compressor, a pipe for conveying gaseous 100 nitrogen from said high pressure column to said compressor, a pipe for conveying compressed gaseous nitrogen to a heat exchanger within said evaporator, an expansion valve, a pipe for conveying liquid nitrogen from said heat 105 exchanger to said expansion valve and a pipe for carrying expanded liquid nitrogen from said expansion valve to the top of said high pressure column.
For a better understanding of the invention and 110 to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying flowsheet of a cryogenic plant in accordance with the present invention.
Referring to the drawing, air is passed through 115 a filter 1 and is compressed to 5 bars gauge by a main air compressor 2. The compressed air leaves the main air compressor 2 through line 3 and after being cooled and scrubbed with water in direct contact after-cooler 4, is passed through 120 line 5 to reversing heat exchanger 6.
As the air passes through the reversing heat exchanger 6 water and carbon dioxide freeze out and the remaining air, together with traces of uncondensed hydrocarbons, is passed through 125 line 7 at —172°C and 4.7 bars gauge to the high pressure column 8 of a double distillation column generally identified by reference numeral 9.
2
GB 2 061 478 A 2
A vapour fraction is withdrawn from the high pressure column 8 through line 48, condensed in superheater 28, and returned through line 11. Crude liquid oxygen is withdrawn from the 5 bottom of the high pressure column 8 through line 10 and after being joined by stream 11 is sub-cooled in sub-cooler 12 which it leaves through line 13. After passing through hydrocarbon adsorbers 20, the liquid is then 10 expanded to approximately 0.5 bars gauge across valve 14 and enters the low pressure column 15 of the double distillation column 9. Substantially pure oxygen collects in the sump 16 of the low pressure column 15 where it cools the reflux 15 condenser 17 associated with the high pressure column 8.
Gaseous nitrogen is removed from the top of the high pressure column 8 through line 22. Part of this nitrogen is condensed in the reboiler 20 condenser 17 and part of the liquid is returned to the high pressure column 8 through line 23 as reflux whilst the remaining liquid is passed through line 18 to sub-cooler 12 which it leaves through line 19. This liquid is then expanded to 25 approximately 0.4 bars gauge at valve 21 and is introduced into the top of the low pressure column 15 as reflux. The balance of the gaseous nitrogen leaving the high pressure column 8 is passed through line 24 to point 25 where the 30 flow is divided into a first stream 26 and a second stream 27. The first stream 26 is passed through superheater 28 which it leaves through line 29 at —175°C. It is then introduced into the cold end of reversing heat exchanger 6. A side drawer 30 is 35 expanded through expander 31 and after joining stream 32 is reintroduced into the cold end of the reversing heat exchanger 6. The balance of stream 29 leaves the reversing heat exchanger at approximately ambient temperature and is used 40 for inter alia purging, reactivating adsorbers 22 and nitrogen product.
Second stream 27, which is at —178°C, is warmed to approximately ambient temperature in heat exchanger 33 and is then compressed to 45 10.3 bars gauge in compressor 34. The resulting warm nitrogen is cooled by water in heat exchanger 35 and is then further cooled in heat exchanger 33 which it leaves through line 36 at —169°C. The vapour is then condensed in heat 50 exchanger 38 and expanded to 4.5 bars gauge at valve 49. The liquid and vapour thus formed are separated in phase separator 37 and the vapour is re-cycled to heat exchanger 33. The liquid from phase separator 37 is reintroduced into the high 55 pressure column 8 of the double distillation column 9.
Liquid oxygen from the sump 16 of the low pressure column 15 is passed through line 40 at approximately 0.5 bars gauge to pump 41 which 60 it leaves through line 42 at 2.1 bars gauge which is a little above the final supply pressure desired. The liquid oxygen is then vaporized in vessel 43 which is warmed by heat exchanger 38. Gaseous oxygen leaves the vessel 43 through pipe 44 and 65 is passed through reversing heat exchanger 6
which it leaves through line 45 as product at 1.8 bars gauge and approximately ambient temperature.
Of the remaining features, impure nitrogen at 70 approximately—193°C leaves the top of the low pressure column 15 through line 46. It is then warmed in sub-cooler 12 which it leaves through line 32. After meeting the nitrogen leaving the expander 31, the mixture is divided into two 75 streams which are each passed through reversing heat exchanger 6. One stream is vented through pipe 50 whilst the other is passed through column 47 where it cools the water used in the direct contact after-cooler 4 by evaporative cooling. 80 Various modifications to the plant described can be made, for example, low pressure product nitrogen from line 29 could be introduced into stream 27 immediately upstream of compressor 34 and withdrawn downstream (or from an 85 intermediate stage) to give high pressure nitrogen product.

Claims (6)

Claims
1. A method of producing gaseous oxygen which method comprises the steps of
90 fractionating dry compressed air in a distillation system having a high pressure column operating at between 4 and 8 bars gauge and a low pressure column operating at between 0.3 and 2 bars gauge, and wherein liquid oxygen is 95 withdrawn from the bottom of said low pressure column, is pressurized and is evaporated against a stream of substantially pure nitrogen which has been removed from the top of said high pressure column and compressed to such a pressure that it 100 is at least partly liquified by the evaporation of said oxygen, and wherein at least part of said liquified nitrogen is expanded and returned to said high pressure column as reflux.
2. A method as claimed in Claim 1, wherein the 105 pressure of said oxygen is raised by a pump.
3. A method according to Claim 1 or 2,
wherein said low pressure column is raised so that its bottom is at least 15 m above ground level.
110
4. A method according to Claim 1, 2 or 3,
wherein said high pressure column is operated at between 4.5 and 7 bars gauge.
5. A method according to any preceding claim, wherein said low pressure column is operated at between 0.5 and 2.0 bars gauge.
40
6. A cryogenic plant for producing gaseous oxygen which plant comprises a high pressure column and a low pressure column for distilling air, an evaporator, a pipe for conveying, in use, liquid oxygen from the bottom of said low 45 pressure column to said evaporator, means to ensure that, in use, the pressure of liquid oxygen at said evaporator is higher than the pressure of liquid oxygen leaving said low pressure column, a pipe for carrying gaseous oxygen from said 50 evaporator, a heat exchanger, a pipe for conveying gaseous nitrogen from said high pressure column to said heat exchanger, a compressor, a pipe for conveying gaseous nitrogen from said heat exchanger to said 55 compressor, a pipe for conveying compressed gaseous nitrogen to said heat exchanger, a pipe for conveying compressed gaseous nitrogen from said heat exchanger to a heat exchanger within said evaporator, an expansion valve, a pipe for 60 conveying liquid nitrogen from said heat exchanger within said evaporator to said expansion valve, and a pipe for carrying expanded liquid nitrogen from said expansion valve to the top of said high pressure column.
Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1981. Published by the Patent Office, 25 Southampton Buildings, London, WC2A 1 AY, from which copies maybe obtained.
5. A method according to any preceding claim, wherein said low pressure column is operated at
115 between 0.5 and 2.0 bars gauge.
6. A cryogenic plant for producing gaseous oxygen which plant comprises a high pressure column and a low pressure column for distilling air, an evaporator, a pipe for conveying, in use,
120 liquid oxygen from the bottom of said low pressure column to said evaporator, means to „ ensure that, in use, the pressure of liquid oxygen at said evaporator is higher than the pressure of liquid oxygen leaving said low pressure column, a 125 pipe for carrying gaseous oxygen from said evaporator, a compressor, a pipe for conveying gaseous nitrogen from said high pressure column to said compressor, a pipe for conveying
3
GB 2 061 478 A 3
compressed gaseous nitrogen to a heat exchanger with said evaporator, an expansion valve, a pipe for conveying liquid nitrogen from said heat exchanger to said expansion valve, and 5 a pipe for carrying expanded liquid nitrogen from said expansion valve to the top of said high pressure column.
New Claims or Amendments to Claims filed on 3 July 1980 10 Superseded Claims 1 to 6.
New or Amended Claims:—
1. A method of producing gaseous oxygen which method comprises the steps of fractionating dry compressed air in a distillation
15 system having a high pressure column operating at between 4 and 8 bars gauge and a low pressure column operating at between 0.3 and 2 bars gauge, and wherein liquid oxygen is withdrawn from the bottom of said low pressure 20 column, is pressurized and is evaporated against a stream of substantially pure nitrogen which has been removed from the top of said high pressure column warmed in a heat exchanger, compressed, cooled in said heat exchanger, at least partly 25 liquified by the evaporation of said oxygen, and, at least in part, expanded and returned to said high pressure column as reflux.
2. A method as claimed in Claim 1, wherein the pressure of said oxygen is raised by a pump.
30 3. A method according to Claim 1 or 2,
wherein said low pressure column is raised so that its bottom is at least 15 m above ground level.
4. A method according to Claim 1,2 or 3,
35 wherein said high pressure column is operated at between 4.5 and 7 bars gauge.
GB7936637A 1979-10-23 1979-10-23 Method and cryogenic plant for producing gaseous oxygen Expired GB2061478B (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB7936637A GB2061478B (en) 1979-10-23 1979-10-23 Method and cryogenic plant for producing gaseous oxygen
EP80303721A EP0029656A1 (en) 1979-10-23 1980-10-22 Method and cryogenic plant for producing gaseous oxygen

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB7936637A GB2061478B (en) 1979-10-23 1979-10-23 Method and cryogenic plant for producing gaseous oxygen

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GB2061478A true GB2061478A (en) 1981-05-13
GB2061478B GB2061478B (en) 1983-06-22

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Cited By (1)

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EP2593739B1 (en) * 2010-07-13 2017-04-12 L'Air Liquide Société Anonyme pour l'Etude et l'Exploitation des Procédés Georges Claude Cooling unit, and apparatus for separating air by means of cryogenic distillation including such a cooling unit

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GB2079428A (en) * 1980-06-17 1982-01-20 Air Prod & Chem A method for producing gaseous oxygen
GB2125949B (en) * 1982-08-24 1985-09-11 Air Prod & Chem Plant for producing gaseous oxygen
DE3428968A1 (en) * 1984-08-06 1986-02-13 Linde Ag, 6200 Wiesbaden METHOD AND DEVICE FOR DISASSEMBLING ROHARGON
DE3565248D1 (en) * 1985-04-18 1988-11-03 Escher Wyss Ag Method and apparatus for preparing high-concentration alkali
US5471843A (en) * 1993-06-18 1995-12-05 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Process and installation for the production of oxygen and/or nitrogen under pressure at variable flow rate
FR2706595B1 (en) * 1993-06-18 1995-08-18 Air Liquide Process and installation for producing oxygen and / or nitrogen under pressure with variable flow rate.
CN102466390A (en) * 2010-11-11 2012-05-23 中国钢铁股份有限公司 Nitrogen yield increasing method for use in air separation unit

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US2663166A (en) * 1943-05-27 1953-12-22 Air Prod Inc Method of and apparatus for pumping liquefied gases
DE1103363B (en) * 1958-09-24 1961-03-30 Linde Eismasch Ag Method and device for generating a balanced cold budget when extracting gas mixtures and / or gas mixture components under higher pressure by rectification
DE1112997B (en) * 1960-08-13 1961-08-24 Linde Eismasch Ag Process and device for gas separation by rectification at low temperature
DE1907525A1 (en) * 1969-02-14 1970-08-20 Vnii Kriogennogo Masinostrojen Process for separating nitrogen and oxygen from the air
DE2535132C3 (en) * 1975-08-06 1981-08-20 Linde Ag, 6200 Wiesbaden Process and device for the production of pressurized oxygen by two-stage low-temperature rectification of air

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2593739B1 (en) * 2010-07-13 2017-04-12 L'Air Liquide Société Anonyme pour l'Etude et l'Exploitation des Procédés Georges Claude Cooling unit, and apparatus for separating air by means of cryogenic distillation including such a cooling unit

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EP0029656A1 (en) 1981-06-03

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