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US20130047666A1 - Method and device for obtaining pressurized nitrogen and pressurized oxygen by low-temperature separation of air - Google Patents

Method and device for obtaining pressurized nitrogen and pressurized oxygen by low-temperature separation of air Download PDF

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Publication number
US20130047666A1
US20130047666A1 US13/558,529 US201213558529A US2013047666A1 US 20130047666 A1 US20130047666 A1 US 20130047666A1 US 201213558529 A US201213558529 A US 201213558529A US 2013047666 A1 US2013047666 A1 US 2013047666A1
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column
low
pressure
oxygen
pressure column
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Alexander Alekseev
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Linde GmbH
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Linde GmbH
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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
    • F25J3/04084—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 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
    • F25J3/04006—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
    • F25J3/04248—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
    • F25J3/04436—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 at least a triple pressure main column system
    • F25J3/04454—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 at least a triple pressure main column system a main column system not otherwise provided, e.g. serially coupling of columns or more than three pressure levels
    • 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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/10—Processes or apparatus using separation by rectification in a quadruple, or more, column or pressure system
    • 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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/20—Processes or apparatus using separation by rectification in an elevated pressure multiple column system wherein the lowest pressure column is at a pressure well above the minimum pressure needed to overcome pressure drop to reject the products to atmosphere
    • 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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/50—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the 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
    • F25J2235/00—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
    • F25J2235/52—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams the fluid being oxygen enriched compared to air ("crude 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
    • 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
    • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
    • F25J2240/40—Expansion without extracting work, i.e. isenthalpic throttling, e.g. JT valve, regulating valve or venturi, or isentropic nozzle, e.g. Laval
    • F25J2240/44—Expansion without extracting work, i.e. isenthalpic throttling, e.g. JT valve, regulating valve or venturi, or isentropic nozzle, e.g. Laval the 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
    • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
    • F25J2240/40—Expansion without extracting work, i.e. isenthalpic throttling, e.g. JT valve, regulating valve or venturi, or isentropic nozzle, e.g. Laval
    • F25J2240/46—Expansion without extracting work, i.e. isenthalpic throttling, e.g. JT valve, regulating valve or venturi, or isentropic nozzle, e.g. Laval the fluid being 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
    • F25J2250/00—Details related to the use of reboiler-condensers
    • F25J2250/20—Boiler-condenser with multiple exchanger cores in parallel or with multiple re-boiling or condensing streams

Definitions

  • the invention relates to a method for obtaining pressurized nitrogen and pressurized oxygen by low-temperature separation of air wherein compressed and purified feed air is cooled in a main heat exchanger and introduced into a distillation column system for nitrogen-oxygen separation, the system comprising at least a high-pressure column and a low-pressure column, wherein the low-pressure column is operated at a pressure which is at least 2 bar.
  • At least one nitrogen stream is withdrawn from the upper region of the low-pressure column, warmed in the main heat exchanger and obtained as pressurized nitrogen product.
  • At least one oxygen stream is withdrawn from the lower region of the low-pressure column, warmed in the main heat exchanger and obtained as pressurized oxygen product.
  • an impure nitrogen stream is withdrawn in the gaseous state from a first intermediate point of the low-pressure column, beneath the point at which the nitrogen stream is withdrawn.
  • the distillation column system of the invention can be constructed as a two-column system (for example as a classical Linde double column system), or else as a three-column or multicolumn system.
  • further devices for obtaining high-purity products and/or other air components, in particular noble gases can be comprised, for example for obtaining argon and/or krypton-xenon.
  • Pressurized product (pressurized oxygen product, pressurized nitrogen product) is here taken to mean the end product of an air separation system which is at a pressure which is at least 0.5 bar above atmospheric pressure, and in particular at least 2 bar.
  • “Impure nitrogen” here denotes a fraction which contains at least 80% nitrogen. These and all further percentages are to be understood as molar amounts.
  • the “main heat exchanger” serves for cooling feed air in indirect heat exchange with return streams from the distillation column system for nitrogen-oxygen separation (or from other columns).
  • the main heat exchanger can be formed of one or more parallel- and/or series-connected heat exchanger sections, for example from one or more plate heat exchanger blocks.
  • Condenser-evaporator denotes a heat exchanger in which a first condensing fluid stream comes into indirect heat exchange with a second vaporizing fluid stream.
  • Each condenser-evaporator has a liquefaction chamber and an evaporation chamber which consist of liquefaction passages or evaporation passages.
  • the condensation (liquefaction) of a first fluid stream is carried out, and in the evaporation chamber the evaporation of a second fluid stream is carried out.
  • Evaporation and liquefaction chambers are formed by groups of passages which are in a heat-exchange relationship with one another.
  • the method according to the invention is suitable, in particular, for systems for simultaneous generation of pressurized oxygen and large amounts of pressurized nitrogen; for example, 50 to 70% of the total amount of air is obtained as pressurized nitrogen.
  • a plurality of pressurized nitrogen fractions at different pressures can also be generated if these are required by nitrogen consumers, as occurs, for example, in IGCC systems (“integrated gasification combined cycle”; integrated coal or heavy oil gasification combined gas turbine and steam turbine cycle power plant).
  • the impure nitrogen stream usually designated residual gas (10 to 30% of the total amount of air)
  • residual gas 10 to 30% of the total amount of air
  • the impure nitrogen stream has the elevated pressure at which the low-pressure column is operated.
  • energy of this gas should be utilized in the system.
  • the conventional solution is that the residual gas is heated in a heat exchanger, and thereafter expanded to a correspondingly low pressure in a turbine (residual gas turbine). In this operation the residual gas cools down. The cold residual gas is passed again through the main heat exchanger and cools warmer streams in the process.
  • Such processes are known from EP 384483 B1 (U.S. Pat. No. 5,036,672) or U.S. Pat. No. 3,886,758.
  • distillation column system for nitrogen-oxygen separation which additionally comprises a residual gas column, which operates at a pressure lower than the operating pressure of the low-pressure column.
  • the residual gas column comprises a bottoms evaporator which is designed as a condenser-evaporator. Also, a liquid crude oxygen fraction, in particular from the high-pressure column, is expanded and passed to the residual gas column at a first intermediate point. Also, a gaseous impure nitrogen stream is introduced into the liquefaction chamber of the bottoms evaporator of the residual gas column, where it is at least partly liquefied. And, the at least partly liquefied impure nitrogen stream is expanded and introduced into the upper region of the residual gas column.
  • residual gas column For recovering the pressure energy from the impure nitrogen stream, instead of a residual gas turbine, an additional separation column is used which is denoted residual gas column.
  • the distillation column system for nitrogen-oxygen separation preferably comprises a main condenser which is constructed as a condenser-evaporator.
  • the top of the high-pressure column and the bottom of the low-pressure column are in heat-exchanging connection thereby.
  • a liquid bottoms fraction is withdrawn from the residual gas column and passed to the low-pressure column at a second intermediate point which is situated below the first intermediate point of the low-pressure column (i.e., the point of withdrawal of the impure nitrogen stream). Since the residual gas column is operated at a lower pressure than the low-pressure column, the pressure in the liquid bottoms fraction must be increased before introduction thereof into the low-pressure column, for example by a pump.
  • a gaseous residual stream is taken off from the top of the residual gas column and warmed in the main heat exchanger.
  • the pressurized oxygen product can in principle be obtained at the operating pressure of the low-pressure column (minus conduit losses) or be further compressed (external compression) in an oxygen compressor downstream of the main heat exchanger.
  • internal compression is more expedient, in which an oxygen stream is withdrawn in the liquid state from the lower region of the low-pressure column, subjected in the liquid state to a pressure increase and, in the main heat exchanger, vaporized or —at supercritical pressure—pseudo-vaporized in indirect heat exchange with feed air, wherein a part of the feed air is liquefied or—at supercritical pressure—pseudo-liquefied.
  • At least a part of the (pseudo-)liquefied feed air can in this case be passed to the residual gas column, especially at a second intermediate point which is situated above the first intermediate point at which the crude oxygen fraction from the high-pressure column is introduced.
  • the low-pressure column also preferably does not have a top condenser.
  • As reflux liquid in the upper region of the low-pressure column rather, liquid nitrogen from the high-pressure column is used.
  • liquid nitrogen from the medium-pressure column can be applied as reflux to the low-pressure column.
  • the invention in addition relates to an apparatus for obtaining pressurized nitrogen and pressurized oxygen by low-temperature separation of air comprising: a distillation column system for nitrogen-oxygen separation that comprises at least one high-pressure column and one low-pressure column: a main heat exchanger for cooling compressed and purified feed air; means (e.g., pipes) for introducing cooled feed air into the distillation column system; a control appliance for open-loop control of the operating pressure of the low-pressure column to a value which is at least 2 bar; means (e.g., pipes) for withdrawing a nitrogen stream from the upper region of the low-pressure column; means (e.g., pipes) for introducing the nitrogen stream into the main heat exchanger for warming; means (e.g., pipes) for taking off the warmed nitrogen stream as pressurized nitrogen product; means (e.g., pipes) for withdrawing an oxygen stream from the lower region of the low-pressure column and warming this oxygen stream in the main heat exchanger to obtain a pressurized oxygen product; means (e.
  • FIG. 2 shows a second exemplary embodiment of a method according to the invention, and a corresponding apparatus, in which the distillation column system for nitrogen-oxygen separation is constructed as a three-column system having a residual gas column.
  • atmospheric air is drawn in via line 1 by a main air compressor 2 and compressed to a pressure of approximately 10 bar (for example, 5 to 18 bar, such as 10.5 bar).
  • the compressed feed air 3 is cooled in a precooler 4 and then purified, that is to say in particular is freed from water and carbon dioxide, in a purifier 5 which contains molecular-sieve adsorbers.
  • the second and third substreams 20 , 30 are first passed jointly via line 7 to a first motor-driven booster 9 having an aftercooler 15 and there boosted to an intermediate pressure of approximately 20 bar.
  • the second substream 20 (turbine stream) is further compressed to about 28 bar in a turbine-driven booster 21 having an aftercooler 22 and passed at this pressure via line 23 to the warm end of the main heat exchanger 8 .
  • At an intermediate temperature it is withdrawn via line 24 , work-producingly expanded in an expansion turbine 25 to about high-pressure column pressure and finally introduced via the lines 26 and 12 into the high-pressure column.
  • a generator turbine can also be used and booster 21 and aftercooler 22 dispensed with (which is not shown).
  • the third substream 30 is brought from the intermediate pressure in a second motor-driven booster 31 having an aftercooler 32 to a high pressure of 60 bar, conducted via line 33 to the main heat exchanger 8 and there cooled and (pseudo-) liquefied. Then, the third substream 33 is expanded in an expansion valve 34 to about high-pressure column pressure and introduced via line 35 into the distillation column system for nitrogen-oxygen separation, especially at least in part in liquid form.
  • substream 33 can be introduced via line 35 into the high pressure column at a point which is, for example, 6-12 trays from the bottom, e.g., 10 trays from bottom.
  • the expansion is carried out in a turbine 36 which is coupled to a generator 37 .
  • a part 38 , 39 , of the liquid air can be cooled in a subcooling counterflow heat exchanger 54 and fed to the low-pressure column 51 at a suitable intermediate point (for example, 10-30 trays from top of the low-pressure column such as 12 trays from the top).
  • a nitrogen-rich intermediate fraction 68 , 69 is removed from the high-pressure column 50 , cooled in the subcooling counterflow heat exchanger 54 and fed to the low-pressure column 51 at an intermediate point.
  • the nitrogen-rich intermediate fraction 68 , 69 can be introduced into the low-pressure column at a point which is 10-18 tray from the top, e.g., 12 trays from the top.
  • the oxygen-enriched bottoms fraction 70 from the high-pressure column 50 is likewise cooled in the subcooling counterflow heat exchanger 54 and passed in a first part 71 to the low-pressure column 51 at another intermediate point, for example, 8 to 40 trays from the bottom of low-pressure column 51 , e.g., 10 trays.
  • pressurized nitrogen product is obtained at four different pressures.
  • two nitrogen product streams are taken off directly in the gaseous state from the distillation column system for nitrogen-oxygen separation, and warmed in the main heat exchanger 8 to about ambient temperature, namely gaseous overhead nitrogen 73 , 74 , 75 from the low-pressure column 51 as pressurized nitrogen product at low-pressure column pressure (GAN) and a second part 72 of the overhead nitrogen 55 of the high-pressure column as pressurized nitrogen product at high-pressure column pressure (PGAN 1 ).
  • a pressurized oxygen product could be obtained at about low-pressure column pressure by gaseous withdrawal immediately above the bottom of the low-pressure column 51 and subsequent warming in the main heat exchanger 8 and, if required, further compressed (external compression) in an oxygen compressor.
  • further compressed in an oxygen compressor.
  • the oxygen stream 77 is subjected in the liquid state to a pressure increase in an oxygen pump 78 to an elevated oxygen pressure and, in the main heat exchanger 8 , vaporized or pseudo-vaporized in indirect heat exchange with feed air, wherein a part of the feed air is liquefied or pseudo-liquefied.
  • At least a first part 80 , 81 , of the pumped oxygen 79 is obtained in this case at the elevated oxygen pressure as pressurized oxygen product (HP-GOX).
  • Another part 82 , 84 , of the pumped oxygen 79 can be throttled in an expansion valve 83 to an intermediate pressure between the low-pressure column pressure and the elevated oxygen pressure and obtained at this intermediate pressure as a further gaseous pressurized oxygen product (MP-GOX).
  • a gaseous impure nitrogen stream 85 is withdrawn from the low-pressure column, which is less pure than the overhead nitrogen 73 , but contains at least 80% nitrogen. In the exemplary embodiment, its nitrogen content is 90%. According to the invention, this stream is used for operating a residual gas column 52 that comprises a bottoms evaporator 85 and is operated at a pressure of 1.4 bar at the top.
  • the impure nitrogen stream 85 is introduced into the liquefaction chamber of the bottoms evaporator 86 , there brought into indirect heat exchange with the bottoms liquid of the residual gas column 52 and in this case at least in part condensed.
  • the at least in part liquefied impure nitrogen stream 87 is expanded in a throttle valve 88 to the operating pressure of the residual gas column and introduced into the upper region of the residual gas column 52 , in particular directly at the top of the column.
  • a liquid crude oxygen fraction 89 from the high-pressure column 50 is further enriched. It is formed by a part of the bottoms fraction 70 from which it is branched off downstream of the subcooling counterflow heat exchanger 54 .
  • the liquid crude oxygen fraction 89 is expanded in an expansion valve 90 and fed to the residual gas column 52 at a first intermediate point (for example, 2 to 10 trays from the bottom of the residual gas column 52 ).
  • a substream 90 of the liquid air 38 is fed to the residual gas column.
  • the liquid bottoms fraction 91 of the residual gas column is more greatly enriched in oxygen than the crude oxygen fraction 89 from the high-pressure column 50 and is brought using a pump 92 to the higher pressure of the low-pressure column 51 . It is passed to the low-pressure column via line 93 at a second intermediate point which is situated below the first intermediate point at which the impure nitrogen stream 85 is taken off. The second intermediate point is also situated below the feed-in point of the crude oxygen 71 which is passed directly into the low-pressure column 51 from the high-pressure column 50 .
  • the second intermediate point can be 2-12 tray below the feed-in point of streams 70 , 71 .
  • a nitrogen-rich residual stream 94 , 95 , 96 is taken off in the gaseous state and warmed in the subcooling counterflow heat exchanger 54 and in the main heat exchanger 8 .
  • the warm residual gas 96 can be used, if required, further as regeneration gas for the purification unit 5 and/or in an evaporative cooler of the precooler 4 .
  • FIG. 2 differs from FIG. 1 in that the process additionally uses a medium-pressure column 200 , as is known from three-column systems.
  • the medium-pressure column 200 has a condenser-evaporator in each case as bottoms evaporator 201 and top condenser 202 and is operated at a pressure which is between the operating pressures of low-pressure column and high-pressure column, in the example, at 6 bar.
  • a part 203 of the bottoms fraction 70 of the high-pressure column 50 is passed to the medium-pressure column 200 as feed.
  • a part 204 of the liquid air 38 can be fed into the medium-pressure column 200 .
  • the bottoms liquid 205 of the medium-pressure column 200 is partially vaporized in the top condenser 202 of the medium-pressure column 200 and then fed at a suitable point into the low-pressure column 51 via the lines 206 and 207 .
  • the gaseous overhead nitrogen of the medium-pressure column 200 is, provided that it is not condensed in the top condenser 202 , conducted via line 208 to the main heat exchanger 8 and obtained via line 209 as further pressurized nitrogen product at medium-pressure column pressure (PGAN 2 ).
  • the pumped bottoms fraction 293 from the residual gas column 52 is fed exclusively into the medium-pressure column 200 .
  • this fraction similarly to FIG. 1 (line 93 ) can be fed exclusively or partially into the low-pressure column 51 .
  • the feed into the low-pressure column 51 preferably takes place at the same height as feed-in of the fraction 207 remaining liquid from the evaporation chamber of the top condenser 202 of the medium-pressure column.

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  • Health & Medical Sciences (AREA)
  • Emergency Medicine (AREA)
  • Separation By Low-Temperature Treatments (AREA)
US13/558,529 2011-07-26 2012-07-26 Method and device for obtaining pressurized nitrogen and pressurized oxygen by low-temperature separation of air Abandoned US20130047666A1 (en)

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EP11006132A EP2551619A1 (de) 2011-07-26 2011-07-26 Verfahren und Vorrichtung zur Gewinnung von Druckstickstoff und Drucksauerstoff durch Tieftemperaturzerlegung von Luft
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EA201990580A1 (ru) * 2016-08-30 2019-09-30 8 Риверз Кэпитл, Ллк Способ криогенного разделения воздуха для получения кислорода высокого давления
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