WO2012155318A1 - Process and apparatus for the production of oxygen at high pressure by cryogenic distillation - Google Patents

Process and apparatus for the production of oxygen at high pressure by cryogenic distillation Download PDF

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Publication number
WO2012155318A1
WO2012155318A1 PCT/CN2011/074027 CN2011074027W WO2012155318A1 WO 2012155318 A1 WO2012155318 A1 WO 2012155318A1 CN 2011074027 W CN2011074027 W CN 2011074027W WO 2012155318 A1 WO2012155318 A1 WO 2012155318A1
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Prior art keywords
exchanger
pressure
sent
liquid
column
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
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PCT/CN2011/074027
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French (fr)
Inventor
Francois De Bussy
Frédéric GUYARD
Philippe Merino
Bo Wei ZHAO
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Original Assignee
Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
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Application filed by Air Liquide SA, LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude filed Critical Air Liquide SA
Priority to PCT/CN2011/074027 priority Critical patent/WO2012155318A1/en
Publication of WO2012155318A1 publication Critical patent/WO2012155318A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • F25J3/04012—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of warm gaseous streams; details of intake or interstage cooling
    • F25J3/04018—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of warm gaseous streams; details of intake or interstage cooling of main feed air
    • 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
    • F25J3/04012—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of warm gaseous streams; details of intake or interstage cooling
    • F25J3/04024—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of warm gaseous streams; details of intake or interstage cooling of purified feed air, so-called boosted air
    • 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
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04109—Arrangements of compressors and /or their drivers
    • F25J3/04115—Arrangements of compressors and /or their drivers characterised by the type of prime driver, e.g. hot gas expander
    • F25J3/04121—Steam turbine as the prime mechanical driver
    • 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
    • F25J3/04109—Arrangements of compressors and /or their drivers
    • F25J3/04145—Mechanically coupling of different compressors of the air fractionation process to the same driver(s)
    • 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
    • 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
    • F25J3/0429—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 feed air, e.g. used as waste or product air or expanded into an auxiliary column
    • F25J3/04296—Claude expansion, i.e. expanded into the main or 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
    • 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
    • F25J3/04375—Details relating to the work expansion, e.g. process parameter etc.
    • F25J3/04387—Details relating to the work expansion, e.g. process parameter etc. using liquid or hydraulic turbine expansion
    • 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
    • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
    • F25J2240/02—Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream
    • F25J2240/10—Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream the fluid being air
    • 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
    • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
    • F25J2290/12—Particular process parameters like pressure, temperature, ratios

Definitions

  • the present invention relates to a process and an apparatus for the production of oxygen at high pressure by cryogenic distillation.
  • the process of this invention can be used to produce oxygen at a pressure at least up to 110 bars without the need of using a stream of air at higher pressure.
  • the design and manufacture of brazed aluminium heat exchangers for high pressure applications is particularly demanding.
  • a process for the production of oxygen at a pressure of at least 70 bars abs by cryogenic distillation of air in which i) compressed air is cooled in an exchanger system and sent to a column system wherein it is separated to form a liquid containing at least 80% mol. oxygen and a fluid rich in nitrogen, and
  • the air cooled in the exchanger system is constituted by the air stream at pressure P which is sent to the exchanger in which the liquid vaporizes and which constitutes a first air stream.
  • the ratio P/Pv is less than or equal to 0.9.
  • the ratio P/Pv is less than or equal to 0.87.
  • the ratio P/Pv is greater than 0.4.
  • the exchanger system comprises a first exchanger and a second exchanger and wherein the first exchanger cools an air stream at below 7 bars and above 1 bar against at least one nitrogen stream at a pressure of below 7 bars abs and above 1 bars abs and the liquid vaporizes in the second exchanger in which all the streams, except one or two nitrogen streams from the column system, are at pressures of above 50 bars , even above 60 bars but below 110 bars abs, the air stream at pressure P being cooled in the second exchanger.
  • an air stream is sent to the second exchanger, cooled, expanded in a turbine and sent to at least one column of the column system.
  • the column system comprises a high pressure column and a low pressure column.
  • the air stream at pressure P is cooled in the second heat exchanger, expanded in a valve or a liquid turbine and sent to the column system in liquid form.
  • the total amount of liquid product or products is less than 10% of Q.
  • processes are used in which the ratio between the pressure of the high pressure air and the high pressure oxygen to be vaporised is equal to or less than 1. In this case, it transpires that, surprisingly, the energy penalties are not very great, so long as the oxygen pressure is at least 70 bars abs.
  • the high pressure air can be produced from a booster air compressor fed by air from an adsorbant drying unit.
  • the high pressure air can be obtained from the outlet of a brake compressor, coupled to one or more cryogenic turboexpanders.
  • the brake compressor may have an inlet temperature which is around ambient temperature or much colder, as for example a cold compressor.
  • the heat exchanger used to vaporize the liquid oxygen at a vaporization pressure Pv at or above 70 bars may receive only one other stream which is an air stream at a pressure of less than Pv bars abs.
  • the heat exchanger may not only vaporize liquid oxygen at the pressure Pv but also warm other streams from the column system and/or cool air and/or nitrogen streams at pressures less than Pv.
  • the process may produce liquid (ie at least one final liquid product which is rich in oxygen, nitrogen or argon). However the process should produce a total quantity of liquid product or products which does not exceed 20% of the liquid rich in oxygen removed from the low pressure column, or preferably which does not exceed 10% of the liquid rich in oxygen removed from the low pressure column or even not exceeding 5% of the liquid rich in oxygen removed from the low pressure column.
  • a stream of air 1 is compressed to between 5 and 6 bars in a compressor C01, purified in a purification system 3 to remove water and carbon dioxide and divided in two.
  • One fraction 5 representing 35% of the air is compressed in booster compressor 7 to a pressure lower than 88 bars, for example 70 bars or even as low as 38 bars and is divided in two.
  • One stream 13 is compressed to 76 bars and sent to high pressure exchanger E01-HP where it is cooled.
  • the cooled stream 13 is divided into streams 19 and 21, one of which is sent to the low pressure column K2 and the other of which is sent to high pressure column Kl.
  • the other stream 15 is partially cooled in exchanger E01-HP and expanded in turboexpander ET01, coupled to booster compressor 11, down to the pressure of column Kl.
  • a low pressure air stream is taken from as stream 9 and sent to the low pressure heat exchanger E01-LP, cooled and mixed with the expanded stream 15 before being sent to the high pressure column Kl as stream 17.
  • High pressure column Kl operates at between 5 and 6 bars abs and low pressure column K2 operates at between 1.3 and 2 bars abs.
  • the columns are thermally linked by a vaporizer E02 which is warmed by high pressure column nitrogen and warms the bottom liquid of the low pressure column K2.
  • Liquid oxygen 31 is removed from the bottom of the low pressure column and divided in two. One part forms the liquid product LOX and the rest is pressurized by pump P03 up to 88 bars abs. The pressurized oxygen is vaporized in the high pressure heat exchanger E01-HP to form high pressure oxygen HPGOX at 88 bars abs.
  • Low pressure nitrogen 33 is warmed in subcooler 23 and then divided in two, one part 35 being sent to the high pressure exchanger E01-HP and the rest 37 being sent to the low pressure exchanger E01-LP.
  • the warmed streams are waste nitrogen streams WN.
  • a stream of medium pressure nitrogen 43 is warmed in the low pressure exchanger E01 -LP to form stream MPGAN.
  • the highest pressure of any air stream sent to the high pressure exchanger is that of stream 13, 76 bar abs and the highest pressure for an oxygen stream being that of oxygen stream 41 at 88 bars abs.
  • All the streams sent to the low pressure exchanger EOl-HP are at pressures lower than 7 bars abs.
  • the main compressor C01 and a booster compressor 7 are coupled to a steam turbine.
  • the compressed air is purified in unit 3 and then divided into stream 5 and stream 9.
  • the stream 5 sent to the compressor 7 is divided in two, one part 13 being compressed to 76 bars abs in a compressor C05-2,driven by a steam turbine, and sent to the high pressure heat exchanger EOl-HP.
  • the rest of the air 15 is compressed to a pressure of at most 88 bars, for example 70 bars or even as low as 38 bars, cooled in exchanger EOl-HP to an intermediate temperature thereof and entirely expanded in turboexpander ETOl before being mixed with stream 9 downstream of the exchangers.
  • Stream 13 is cooled in heat exchanger EOl-HP, expanded and divided between columns Kl and K2 as streams 19, 21.
  • the air stream 9 coming from unit 3 is cooled in the low pressure heat exchanger E01-LP to form a stream of cold air.
  • High pressure column Kl operates at between 5 and 6 bars abs and low pressure column K2 operates at between 1.3 and 2 bars abs.
  • Liquid oxygen 31 is removed from the bottom of the low pressure column and divided in two. One part forms the liquid product LOX and the rest is pressurized by pump P03 up to 88 bars abs. The pressurized oxygen is vaporized in the high pressure heat exchanger EOl-HP.
  • Low pressure nitrogen 33 is warmed in subcooler 23 and then divided in two, one part 35 being sent to the high pressure exchanger EOl-HP and the rest 37 being sent to the low pressure exchanger E01-LP.
  • a stream of medium pressure nitrogen 43 is warmed in the high pressure exchanger EOl-HP.
  • the highest pressure of any air stream sent to the high pressure exchanger is that of stream 13, 76 bar abs and the highest pressure for an oxygen stream being that of oxygen stream 41 at 88 bars abs.
  • All the streams 9, 37, 43 sent to the low pressure exchanger EOl-HP are at pressures lower than 7 bars abs.
  • FIG 3 shows the heat exchange diagram for Figure 1 and Figure 4 that of Figure 2.
  • Figure 5 a version of Figure 1 is shown in which the air stream at high pressure 13 is cooled in the heat exchanger at 76 bars abs and then expanded in a liquid turbine 51 driving a generator.
  • the liquid formed is divided between columns Kl and K2 in streams 19 and 21.
  • the flowrate of the oxygen to be vaporized is less than the flowrate of the air at the vaporization pressure, against which the oxygen vaporizes.

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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)

Abstract

In a process for the production of oxygen at a pressure of at least 70 bars abs by cryogenic distillation of air, compressed air (1) is cooled in an exchanger system (E01-LP,E01-HP) and sent to a column system (K1,K2) wherein it is separated to form a liquid (31) containing at least 80% mol. oxygen and a fluid (33) rich in nitrogen and a quantity Q of the said liquid (31) is removed from the column system (K1,K2), pressurized to a vaporization pressure Pv of at least 70 bars abs and vaporized in an exchanger (EOl-HP) of the exchanger system (EOl-LPJiOl-HP) wherein at least one air stream (13,15) is sent to the exchanger (EOl-HP) in which the liquid (31) vaporizes and the highest pressure of any air stream (13,15) sent to the exchanger in which the liquid (31) vaporizes is a pressure P which is less than or equal to Pv and wherein, if any liquid product is produced by the process, the total amount of liquid product or products is less than 20% of Q.

Description

Process and apparatus for the production of oxygen at high pressure by cryogenic distillation
The present invention relates to a process and an apparatus for the production of oxygen at high pressure by cryogenic distillation.
It is known to produce a high pressure oxygen stream by pressurizing a liquid oxygen stream and vaporizing it under pressure by heat exchange with a stream of air at high pressure. The air pressure is generally 2,3 times higher than the pressure of the oxygen, as mentioned in 89 AIChE Symposium Series 294, "Modern Liquid Pump Oxygen Plants: Equipment and Performance", No. 294 by W.F. Castle, BOC Process Plants, p 14. In WO-A- 2010/088121 a pressure range for the air is defined which is significantly higher than the oxygen vaporisation pressure.
All the pressures mentioned in this document are absolute pressures.
It is also known that a certain number of precautions should be taken in designing and manufacturing brazed aluminium heat exchangers to be used at high pressures.
These include:
• Limitation of the size of the exchanger cores (stacking height and width of the parting sheets)
• Choice of fins adapted to high pressures : herringbone type fins or thick fins with a high fpi are suitable
• Thickness of the parting sheets for the heat exchangers
• Increasing the thickness of the brazing material plating to 200 μιη or more
• Possibly asymmetric thickness for the brazing material plating
• Width of side bars and end bars
• Limitation of the header diameters and reinforcement of the regions to which they are fixed
There is a growing need to produce oxygen at pressures of 70 bars or more. The prior art would imply the use of a stream of high pressure air at a pressure of at least 100 bars, to produce oxygen at pressure of 70 bar or more.
The process of this invention can be used to produce oxygen at a pressure at least up to 110 bars without the need of using a stream of air at higher pressure. The design and manufacture of brazed aluminium heat exchangers for high pressure applications is particularly demanding.
According to the present invention, there is provided a process for the production of oxygen at a pressure of at least 70 bars abs by cryogenic distillation of air in which i) compressed air is cooled in an exchanger system and sent to a column system wherein it is separated to form a liquid containing at least 80% mol. oxygen and a fluid rich in nitrogen, and
ii) a quantity Q of the said liquid is removed from the column system, pressurized to a vaporization pressure Pv of at least 70 bars abs and vaporized in an exchanger of the exchanger system
wherein at least one air stream is sent to the exchanger in which the liquid vaporizes and the highest pressure of any air stream sent to the exchanger in which the liquid vaporizes is a pressure P which is less than or equal to Pv and wherein, if any liquid product is produced by the process, the total amount of liquid product or products is less than 20% of Q.
According to further objects of the invention:
less than 40%, or even less than 25%, of the air cooled in the exchanger system is constituted by the air stream at pressure P which is sent to the exchanger in which the liquid vaporizes and which constitutes a first air stream.
- part of the air sent to the exchanger system is at a pressure substantially equal to the pressure of the column of the column system having the highest pressure,
the ratio P/Pv is less than or equal to 0.9.
the ratio P/Pv is less than or equal to 0.87.
the ratio P/Pv is greater than 0.4.
- the exchanger system comprises a first exchanger and a second exchanger and wherein the first exchanger cools an air stream at below 7 bars and above 1 bar against at least one nitrogen stream at a pressure of below 7 bars abs and above 1 bars abs and the liquid vaporizes in the second exchanger in which all the streams, except one or two nitrogen streams from the column system, are at pressures of above 50 bars , even above 60 bars but below 110 bars abs, the air stream at pressure P being cooled in the second exchanger.
an air stream is sent to the second exchanger, cooled, expanded in a turbine and sent to at least one column of the column system. the column system comprises a high pressure column and a low pressure column.
the air from the turbine is sent to the high pressure column,
the air stream at pressure P is cooled in the second heat exchanger, expanded in a valve or a liquid turbine and sent to the column system in liquid form.
the total amount of liquid product or products is less than 10% of Q. According to the present invention, processes are used in which the ratio between the pressure of the high pressure air and the high pressure oxygen to be vaporised is equal to or less than 1. In this case, it transpires that, surprisingly, the energy penalties are not very great, so long as the oxygen pressure is at least 70 bars abs.
These penalties are more than compensated by the simplification of the air compressors and of the brased aluminium heat exchangers.
The high pressure air can be produced from a booster air compressor fed by air from an adsorbant drying unit.
The high pressure air can be obtained from the outlet of a brake compressor, coupled to one or more cryogenic turboexpanders.
The brake compressor may have an inlet temperature which is around ambient temperature or much colder, as for example a cold compressor.
The heat exchanger used to vaporize the liquid oxygen at a vaporization pressure Pv at or above 70 bars may receive only one other stream which is an air stream at a pressure of less than Pv bars abs.
Otherwise the heat exchanger may not only vaporize liquid oxygen at the pressure Pv but also warm other streams from the column system and/or cool air and/or nitrogen streams at pressures less than Pv.
The process may produce liquid (ie at least one final liquid product which is rich in oxygen, nitrogen or argon). However the process should produce a total quantity of liquid product or products which does not exceed 20% of the liquid rich in oxygen removed from the low pressure column, or preferably which does not exceed 10% of the liquid rich in oxygen removed from the low pressure column or even not exceeding 5% of the liquid rich in oxygen removed from the low pressure column.
The invention will be described in greater details with reference to the figures, Figures 1, 2 and 5 illustrating processes according to the invention and Figures 3 and 4 illustrating heat exchange diagrams for Figures 1 and 2 respectively. All the processes use a double column, including a high pressure column Kl operating at around 6 bars and a low pressure column K2 operating at around 1.5 bars. The column are thermally coupled via a two stage bath vaporized E02 in the bottom of the low pressure column.
In Figure 1, a stream of air 1 is compressed to between 5 and 6 bars in a compressor C01, purified in a purification system 3 to remove water and carbon dioxide and divided in two. One fraction 5 representing 35% of the air is compressed in booster compressor 7 to a pressure lower than 88 bars, for example 70 bars or even as low as 38 bars and is divided in two. One stream 13 is compressed to 76 bars and sent to high pressure exchanger E01-HP where it is cooled. The cooled stream 13 is divided into streams 19 and 21, one of which is sent to the low pressure column K2 and the other of which is sent to high pressure column Kl. The other stream 15 is partially cooled in exchanger E01-HP and expanded in turboexpander ET01, coupled to booster compressor 11, down to the pressure of column Kl.
A low pressure air stream is taken from as stream 9 and sent to the low pressure heat exchanger E01-LP, cooled and mixed with the expanded stream 15 before being sent to the high pressure column Kl as stream 17.
High pressure column Kl operates at between 5 and 6 bars abs and low pressure column K2 operates at between 1.3 and 2 bars abs. The columns are thermally linked by a vaporizer E02 which is warmed by high pressure column nitrogen and warms the bottom liquid of the low pressure column K2.
Liquid oxygen 31 is removed from the bottom of the low pressure column and divided in two. One part forms the liquid product LOX and the rest is pressurized by pump P03 up to 88 bars abs. The pressurized oxygen is vaporized in the high pressure heat exchanger E01-HP to form high pressure oxygen HPGOX at 88 bars abs.
Low pressure nitrogen 33 is warmed in subcooler 23 and then divided in two, one part 35 being sent to the high pressure exchanger E01-HP and the rest 37 being sent to the low pressure exchanger E01-LP. The warmed streams are waste nitrogen streams WN. A stream of medium pressure nitrogen 43 is warmed in the low pressure exchanger E01 -LP to form stream MPGAN.
In this way, the highest pressure of any air stream sent to the high pressure exchanger is that of stream 13, 76 bar abs and the highest pressure for an oxygen stream being that of oxygen stream 41 at 88 bars abs. All the streams sent to the low pressure exchanger EOl-HP are at pressures lower than 7 bars abs.
In Figure 2, the main compressor C01 and a booster compressor 7 are coupled to a steam turbine. The compressed air is purified in unit 3 and then divided into stream 5 and stream 9. The stream 5 sent to the compressor 7 is divided in two, one part 13 being compressed to 76 bars abs in a compressor C05-2,driven by a steam turbine, and sent to the high pressure heat exchanger EOl-HP.
The rest of the air 15 is compressed to a pressure of at most 88 bars, for example 70 bars or even as low as 38 bars, cooled in exchanger EOl-HP to an intermediate temperature thereof and entirely expanded in turboexpander ETOl before being mixed with stream 9 downstream of the exchangers.
Stream 13 is cooled in heat exchanger EOl-HP, expanded and divided between columns Kl and K2 as streams 19, 21.
The air stream 9 coming from unit 3 is cooled in the low pressure heat exchanger E01-LP to form a stream of cold air.
High pressure column Kl operates at between 5 and 6 bars abs and low pressure column K2 operates at between 1.3 and 2 bars abs.
Liquid oxygen 31 is removed from the bottom of the low pressure column and divided in two. One part forms the liquid product LOX and the rest is pressurized by pump P03 up to 88 bars abs. The pressurized oxygen is vaporized in the high pressure heat exchanger EOl-HP.
Low pressure nitrogen 33 is warmed in subcooler 23 and then divided in two, one part 35 being sent to the high pressure exchanger EOl-HP and the rest 37 being sent to the low pressure exchanger E01-LP. A stream of medium pressure nitrogen 43 is warmed in the high pressure exchanger EOl-HP.
In this way, the highest pressure of any air stream sent to the high pressure exchanger is that of stream 13, 76 bar abs and the highest pressure for an oxygen stream being that of oxygen stream 41 at 88 bars abs.
All the streams 9, 37, 43 sent to the low pressure exchanger EOl-HP are at pressures lower than 7 bars abs.
Figure 3 shows the heat exchange diagram for Figure 1 and Figure 4 that of Figure 2.
In Figure 5, a version of Figure 1 is shown in which the air stream at high pressure 13 is cooled in the heat exchanger at 76 bars abs and then expanded in a liquid turbine 51 driving a generator. The liquid formed is divided between columns Kl and K2 in streams 19 and 21.
For all of Figures 1,2 and 5, the flowrate of the oxygen to be vaporized is less than the flowrate of the air at the vaporization pressure, against which the oxygen vaporizes.

Claims

Claims
1. Process for the production of oxygen at a pressure of at least 70 bars abs by cryogenic distillation of air in which
i) compressed air is cooled in an exchanger system (E01-LP, EOl-HP) and sent to a column system (K1,K2) wherein it is separated to form a liquid (43) containing at least 80% mol. oxygen and a fluid (33) rich in nitrogen and
ii) a quantity Q of the said liquid is removed from the column system, pressurized to a vaporization pressure Pv of at least 70 bars abs and vaporized in an exchanger
(EOl-HP) of the exchanger system
wherein at least one air stream (13, 15) is sent to the exchanger in which the liquid vaporizes and the highest pressure of any air stream sent to the exchanger in which the liquid vaporizes is a pressure P which is less than or equal to Pv and wherein, if any liquid product is produced by the process, the total amount of liquid product or products is less than 20% of Q.
2. Process according to Claim 1 wherein less than 40% of the air cooled in the exchanger system (E01-LP, EOl-HP) is constituted by the air stream (13) at pressure P which is sent to the exchanger (EOl-HP) in which the liquid vaporizes and which constitutes a first air stream.
3. Process according to Claim 2 wherein part (9) of the air sent to the exchanger system (E01-LP, EOl-HP) is at a pressure substantially equal to the pressure of the column of the column system having the highest pressure.
4. Process according to any preceding claim wherein the ratio P/Pv is less than or equal to 0.9.
5. Process according to Claim 4 wherein the ratio P/Pv is less than or equal to 0.87.
6. Process according to any preceding claim wherein the ratio P/Pv is greater than 0.4.
7. Process according to any preceding claim wherein the exchanger system (E01-LP, EOl-HP) comprises a first exchanger (E01-LP) and a second exchanger (EOl- HP) and wherein the first exchanger cools an air stream at below 7 bars and above 1 bar against at least one nitrogen stream at a pressure of below 7 bars abs and above 1 bars abs and the liquid vaporizes in the second exchanger in which all the streams, except one or two nitrogen streams from the column system, are at pressures of above 50 bars, even above 60 bars but below 110 bars abs, the air stream at pressure P being cooled in the second exchanger.
8. Process according to Claim 7 wherein an air stream is sent to the second exchanger (EOl-HP), cooled, expanded in a turbine (ET01) and sent to at least one column of the column system.
9. Process according to Claim 7 or 8 wherein the column system comprises a high pressure column (Kl) and a low pressure column (K2).
10. Process according to Claim 8 and 9 wherein the air from the turbine (ET01) is sent to the high pressure column (Kl).
11. Process according to Claim 7,8,9 or 10 wherein the air stream at pressure P is cooled in the second heat exchanger (EOl-HP), expanded in a valve or a liquid turbine and sent to the column system (Kl, K2) in liquid form.
12. Process according to any preceding claim wherein the total amount of liquid product or products is less than 10% of Q.
PCT/CN2011/074027 2011-05-13 2011-05-13 Process and apparatus for the production of oxygen at high pressure by cryogenic distillation Ceased WO2012155318A1 (en)

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