US20220260312A1 - Process and plant for low-temperature fractionation of air - Google Patents

Process and plant for low-temperature fractionation of air Download PDF

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Publication number
US20220260312A1
US20220260312A1 US17/597,000 US202017597000A US2022260312A1 US 20220260312 A1 US20220260312 A1 US 20220260312A1 US 202017597000 A US202017597000 A US 202017597000A US 2022260312 A1 US2022260312 A1 US 2022260312A1
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Prior art keywords
rectification column
condenser evaporator
evaporation
material stream
gas
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US17/597,000
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English (en)
Inventor
Stefan Lochner
Dimitri Golubev
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Linde GmbH
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Linde GmbH
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Assigned to LINDE GMBH reassignment LINDE GMBH ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: LOCHNER, STEFAN, GOLUBEV, Dimitri
Publication of US20220260312A1 publication Critical patent/US20220260312A1/en
Abandoned 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
    • F25J3/04406—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
    • F25J3/04418—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 with thermally overlapping high and low pressure columns
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    • 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
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    • 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
    • F25J3/04048—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of cold gaseous streams, e.g. intermediate or oxygen enriched (waste) streams
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    • F25J3/04054—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of cold gaseous streams, e.g. intermediate or oxygen enriched (waste) streams of air
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    • F25J3/04236—Integration of different exchangers in a single core, so-called integrated cores
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    • F25J2215/50—Oxygen or special cases, e.g. isotope-mixtures or low purity O2
    • F25J2215/56—Ultra high purity oxygen, i.e. generally more than 99,9% O2
    • 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
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/58—Argon
    • 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
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/60—Methane
    • 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
    • F25J2235/50—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams 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
    • 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
    • F25J2240/04—Multiple expansion turbines in parallel
    • 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
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/02—Recycle of a stream in general, e.g. a by-pass stream
    • 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
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/42—Processes or apparatus involving steps for recycling of process streams the recycled stream 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
    • F25J2250/02—Bath type boiler-condenser using thermo-siphon effect, e.g. with natural or forced circulation or pool boiling, i.e. core-in-kettle heat exchanger
    • 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
    • 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
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/02—Internal refrigeration with liquid vaporising loop
    • 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 invention relates to a process for the low-temperature fractionation of air and to a corresponding plant in accordance with the preambles of the independent claims.
  • Air fractionation plants have rectification column systems which, for example, can conventionally be designed as two-column systems, in particular as classical Linde double-column systems, but also as triple-column or multi-column systems.
  • rectification columns for extracting nitrogen and/or oxygen in the liquid and/or gaseous state i.e., rectification columns for nitrogen-oxygen separation
  • rectification columns for extracting further air components in particular the noble gases krypton, xenon, and/or argon
  • the terms “rectification” and “distillation” as well as “column [Säule]” and “column [Kolonne]” or terms composed therefrom are used synonymously.
  • the rectification columns of the mentioned rectification column systems are operated at different pressure levels.
  • Known double-column systems have what is known as a high-pressure column (also referred to as a pressure column, medium-pressure column, or lower column) and what is known as a low-pressure column (also referred to as an upper column).
  • the high-pressure column is typically operated at a pressure level of 4 to 7 bar, in particular approximately 5.3 bar.
  • the low-pressure column is operated at a pressure level of typically 1 to 2 bar, in particular approximately 1.4 bar. In certain cases, even higher pressure levels may be used in either rectification column.
  • the pressures cited here and below are absolute pressures at the top of the respective columns indicated.
  • SPECTRA processes are known from the prior art for providing pressurized nitrogen as the main product. They are explained in more detail below.
  • a so-called oxygen column which can be operated at or above the pressure level of a typical low-pressure column, can be used to obtain pure or high-purity oxygen.
  • This low-pressure column is present in addition to the rectification column used for nitrogen extraction and is fed therefrom.
  • feed air is cooled in a main heat exchanger and introduced into a single column for nitrogen extraction.
  • a nitrogen product stream is taken from the upper region of the single column.
  • a first residual fraction is taken from the lower or central region of the single column, recompressed and subsequently fed back into the single column.
  • An oxygen-containing stream is taken from the single column at an intermediate point and fed to a pure oxygen column.
  • a pure oxygen product stream is taken in the liquid state from the lower region of the pure oxygen column. The pure oxygen product stream is evaporated and heated in the main heat exchanger against feed air and finally obtained as a gaseous product.
  • U.S. Pat. No. 6,279,345 B1 relates to an air fractionation system that can be used for producing ultra-high-purity nitrogen or ultra-high-purity oxygen, wherein oxygen-enriched liquid in a rectification column is evaporated in two steps using a split head condenser, and vapor from the first step is compressed and returned to the rectification column.
  • the object of the present invention is to improve a SPECTRA process with corresponding oxygen extraction, primarily with regard to energy consumption and material yield.
  • the present invention proposes a process for the low-temperature fractionation of air and a corresponding plant with the features of the independent claims.
  • Preferred embodiments form the subject-matter of the dependent claims and of the following description.
  • Liquids and gases may, in the terminology used herein, be rich or poor in one or more components, wherein “rich” can refer to a content of at least 75%, 90%, 95%, 99%, 99.5%, 99.9%, or 99.99%, and “poor” can refer to a content of at most 25%, 10%, 5%, 1%, 0.1%, or 0.01% on a mole, weight, or volume basis.
  • the term “predominantly” can correspond to the definition of “rich.”
  • Liquids and gases may also be enriched in or depleted of one or more components, wherein these terms refer to a content in a starting liquid or a starting gas from which the liquid or gas has been extracted.
  • the liquid or the gas is enriched if it contains at least 1.1 times, 1.5 times, 2 times, 5 times, 10 times, 100 times, or 1000 times the content, and depleted if it contains at most 0.9 times, 0.5 times, 0.1 times, 0.01 times, or 0.001 times the content of a corresponding component, based on the starting liquid or the starting gas. If, for example, reference is made here to “oxygen,” “nitrogen,” or “argon,” this is also understood to mean a liquid or a gas which is rich in oxygen or nitrogen but need not necessarily consist exclusively thereof.
  • pressure level and “temperature level” to characterize pressures and temperatures, which means that corresponding pressures and temperatures in a corresponding plant do not have to be used in the form of exact pressure or temperature values in order to realize the inventive concept.
  • pressures and temperatures typically fall within certain ranges that are, for example, ⁇ 1%, 5%, or 10% around an average.
  • corresponding pressure levels and temperature levels can be in disjointed ranges or in ranges that overlap one another.
  • pressure levels for example, include unavoidable or expected pressure losses.
  • the pressure levels indicated here in bar are absolute pressures.
  • expansion machines are mentioned here, these refer to typically known turboexpanders. These expansion machines can, in particular, also be coupled to compressors. These compressors may in particular be turbocompressors. A corresponding combination of turboexpander and turbocompressor is typically also referred to as a “turbine booster.” In a turbine booster, the turboexpander and the turbocompressor are mechanically coupled, wherein the coupling may take place at the same rotational speed (for example via a common shaft) or at different rotational speeds (for example via suitable gearing). In general, the term “compressor” is used herein.
  • a “cold compressor” refers to a compressor to which a fluid stream is supplied at a temperature level significantly below 0° C., in particular below ⁇ 50, ⁇ 75, or ⁇ 100° C. and up to ⁇ 150 or ⁇ 200° C. A corresponding fluid stream is cooled to a corresponding temperature level in particular by means of a main heat exchanger (see below).
  • a “main air compressor” is characterized in that it compresses all of the air supplied to the air fractionation plant and separated there.
  • further compressors for example booster compressors
  • only a portion of this air that has already been previously compressed in the main air compressor is further compressed.
  • the “main heat exchanger” of an air fractionation plant represents the heat exchanger in which at least the predominant part of the air supplied to the air fractionation plant and separated there is cooled. This takes place at least in part and possibly only in counterflow to material streams that are discharged from the air fractionation plant.
  • material streams or “products” “discharged” from an air fractionation plant are fluids that no longer participate in circuits within the plant but are permanently removed therefrom.
  • a “heat exchanger” for use in the context of the present invention can be designed in a manner customary in the art. It serves for the indirect transfer of heat between at least two fluid streams which are, for example, conducted in counterflow to one another, for example, a warm compressed air stream and one or more cold fluid streams or a cryogenic liquid air product and one or more warm or warmer but possibly also even cryogenic fluid streams.
  • a heat exchanger can be formed from one or more heat exchanger sections connected in parallel and/or serially, e.g., from one or more plate heat exchanger blocks. It is, for example, a plate fin heat exchanger.
  • Such a heat exchanger has “passages” which take the form of fluid channels separated from one another and having heat exchange surfaces, and which are connected together in parallel and separated by other passages to form “passage groups.”
  • the characteristic of a heat exchanger is that at one time heat is exchanged therein between two mobile media, namely at least one fluid stream to be cooled and at least one fluid stream to be heated.
  • a “condenser evaporator” refers to a heat exchanger in which a condensing fluid stream enters into indirect heat exchange with an evaporating fluid stream.
  • Each condenser evaporator has a liquefaction chamber and an evaporation chamber.
  • the liquefaction and evaporation chambers have liquefaction or evaporation passages. Condensation (liquefaction) of the condensing fluid stream is carried out in the liquefaction chamber, and evaporation of the evaporating fluid stream is carried out in the evaporation chamber.
  • the evaporation and liquefaction chambers are formed by groups of passages, which are in a heat-exchanging relationship with one another.
  • the present invention comprises the low-temperature fractionation of air according to the so-called SPECTRA process, as described, inter alia, in EP 2 789 958 A1 and the further patent literature cited therein.
  • this process is a single-column process.
  • first air-fed rectification column
  • second rectification column
  • compressed and pre-purified air is also cooled in the SPECTRA process to a temperature suitable for rectification. It can thereby be partially liquefied.
  • the air is rectified at the typical pressure of a high-pressure column, as explained at the outset, yielding the tops gas enriched in nitrogen in comparison to atmospheric air and a liquid bottoms liquid enriched in oxygen in comparison to atmospheric air.
  • a return flow of the first rectification column used for this purpose is provided in a heat exchanger by condensing tops gas of the first rectification column, more precisely a portion of this tops gas.
  • a condenser evaporator (“first” condenser evaporator), fluid, which is likewise taken from the first rectification column, is used for cooling and thereby evaporated or partially evaporated.
  • Further tops gas may be provided as a nitrogen-rich product.
  • first and second material streams are used in the first condenser evaporator, wherein the first material stream is formed using liquid taken from the first rectification column with a first oxygen content and the second material stream is formed using liquid taken from the first rectification column with a second, higher oxygen content.
  • the liquid used to form the first material stream can be taken from the first rectification column from an intermediate tray or from a liquid retention device.
  • the liquid used to form the second material stream can in particular be at least a portion of the liquid bottoms product of the first rectification column.
  • the first and second material streams are the aforementioned fluid which is used in the first condenser evaporator for cooling and for condensing the corresponding portion of tops gas of the first rectification column.
  • the first material stream can be at least partially compressed by means of a cold compressor and returned to the first rectification column.
  • the second material stream may be at least partially expanded and discharged from the air fractionation plant as a so-called residual gas mixture.
  • one or more compressors can be used which are coupled to one or more expansion machines in which the expansion of the second material stream (or a corresponding portion) is carried out.
  • first or second material stream may also in each case be compressed or expanded in the correspondingly coupled units.
  • An expansion machine that is not coupled to a corresponding compressor can, if present, be braked in particular mechanically and/or by generator. Braking is also possible in the case of an expansion machine that is coupled to a compressor.
  • a compressor that is coupled to one of two expansion machines arranged in parallel can be used. If only one expansion machine is used, the compressor can be coupled thereto.
  • the wording, used below only for reasons of clarity, according to which “a” compressor is coupled to “an” expansion machine, does not preclude the use of a plurality of compressors and/or expansion machines in any mutual coupling.
  • the compressor or compressors described do not have to be driven, in particular not exclusively, by means of the one or more expansion machines mentioned.
  • the compressor or compressors also do not have to take up all of the work released during expansion.
  • a supporting or exclusive drive can also be effected, for example, by using an electric motor, or a brake can be interposed between the expansion machine(s) and the compressor(s).
  • the compressor or compressors are one or more cold compressors, since the compressor or compressors are supplied with the first fluid stream despite its routing through the first condenser evaporator and an optionally subsequent further heating at a low temperature level.
  • a condenser evaporator (“second” condenser evaporator) is typically present in the lower region of the second rectification column and is used to bring bottoms liquid in the second rectification column to boil.
  • This condenser evaporator is conventionally operated with air (feed air) that is compressed (at least) in the main air compressor and cooled in the main heat exchanger, and which is supplied to the first rectification column.
  • this feed air can also be air that is initially present in gaseous form and is liquefied in the second condenser evaporator before it is fed into the first rectification column. It is a portion of the feed air supplied overall to the first rectification column. Further (gaseous) feed air can be fed into the first rectification column without any corresponding liquefaction.
  • the reason for the high specific energy requirement is mainly that in the aforementioned second condenser evaporator in the lower region of the second rectification column, the explained “heating” is realized to a large extent by the aforementioned condensation of the portion of the gaseous feed air.
  • this (liquefied) partial air stream is subsequently (after its evaporation) used for generating cooling capacity or for driving the cold compressor(s) used, in that a corresponding quantity of fluid is taken as the second material stream from the first rectification column, said partial air stream does however not participate further in the rectification process in the first rectification column.
  • the present invention is based on the finding that a process of the type explained above can be modified particularly advantageously in that, instead of a feed air stream in the second condenser evaporator in the lower region of the second rectification column, fluid is used which has been evaporated in the manner explained above as part of the “first” or “second” material stream in the first condenser evaporator. In this way, the air previously used for this purpose can be saved, thereby increasing energy efficiency and yield.
  • the condensed fluid can then be treated as explained below.
  • the invention also opens up particular advantages in that condensation is carried out in the second condenser evaporator at a pressure level at which evaporation of the corresponding fluid in the first condenser evaporator was previously carried out. In this way, recompression can be dispensed with and the condensed gas or the condensate formed can be brought to the required pressure by means of a pump. In contrast to a gas compressor, the operation of a pump is much more reliable and its provision is significantly more cost-effective.
  • the present invention proposes a process for the low-temperature fractionation of air in which an air fractionation plant having a first rectification column and a second rectification column is used.
  • the first rectification column is operated at a first pressure level and the second rectification column is operated at a second pressure level below the first pressure level.
  • Such first and second pressure levels are typical pressure levels, such as are also used in conventional air fractionation plants, in particular in SPECTRA plants with oxygen extraction.
  • the first pressure level may, in particular, be 7 to 14 bar
  • the second pressure level may, in particular, be 1.2 to 5 bar.
  • the second pressure level may generally also be 1 to 4 bar.
  • the first rectification column and the second rectification column can, in particular, be arranged next to one another and are typically not combined with one another in the form of a double column, wherein here a “double column” is understood to mean a separator consisting of two rectification columns and designed as a structural unit, in which column jackets of the two rectification columns are connected, in particular welded, to one another without lines, i.e., directly. However, no fluidic connection needs to be established by this direct connection alone.
  • the first rectification column used in the context of the present invention and the second rectification column used in the context of the present invention have already been described in detail above with reference to the SPECTRA process.
  • the second rectification column can, in particular, be an oxygen column.
  • Atmospheric air which has been compressed and then cooled, is here supplied to the first rectification column. If necessary, corresponding air can be supplied to the first rectification column in the form of a plurality of material streams which can be treated differently and optionally have been previously routed through further apparatuses. In contrast, air is not typically supplied to the second rectification column.
  • the second rectification column is fed from the first rectification column or no material streams that have not already been taken from the first rectification column or formed from such material streams are typically supplied to the second rectification column.
  • tops gas of the first rectification column is obtained as a nitrogen product and discharged from the air fractionation plant
  • bottoms liquid of the second rectification column is obtained as an oxygen product and discharged from the air fractionation plant.
  • further fluids for example tops gas of the second rectification column
  • Fluids otherwise discharged as nitrogen or oxygen products can within the scope of the present invention also be discharged in certain proportions, for example as purge streams or as a further liquid nitrogen product after condensation of tops gas of the first rectification column.
  • first and a second material stream are separately subjected to evaporation below the first pressure level.
  • the evaporation pressures in the first condenser evaporator are in particular 3.5 to 7.5 bara (bar absolute pressure; the values can represent exact or even approximate values) depending on the first pressure level.
  • the fluid that is to be evaporated here which was taken from the first rectification column, is therefore correspondingly expanded.
  • Further tops gas of the first rectification column which is not provided as a gaseous nitrogen product, is condensed in the first condenser evaporator and returned to the first rectification column as a return flow.
  • a proportion of corresponding condensate can also be discharged as the further liquid nitrogen product mentioned, in particular after supercooling against itself.
  • the first material stream evaporated in the first condenser evaporator is formed using liquid taken from the first rectification column with a first oxygen content
  • the second material stream is formed using liquid taken from the first rectification column with a second oxygen content above the first oxygen content.
  • the liquid with the first, lower oxygen content is in particular liquid that is extracted at an intermediate tray or separating tray of the first rectification column or of a corresponding liquid retention device.
  • the liquid with the second, higher oxygen content is in particular bottoms liquid of the first rectification column.
  • gas of the first material stream is partially or completely subjected to recompression to the first pressure level and fed into the first rectification column
  • gas of the second material stream is, after its evaporation or partial evaporation, subjected to expansion in the first condenser evaporator and discharged from the air fractionation plant.
  • the wordings “gas of the first material stream” and “gas of the second material stream” are in particular also to encompass the fact that the entire gas of the first and second material streams is used in the manner explained if a certain portion is not used in other ways, as explained below, in embodiments of the present invention.
  • the wordings “gas of the first material stream” and “gas of the second material stream” are in other words thus intended to denote all or a portion of the corresponding gas but do not preclude that there are further uses within the scope of the invention.
  • the second rectification column is equipped with or at least thermally coupled to the second condenser evaporator, wherein the second condenser evaporator is designed or provided in particular in a bottoms region of the second rectification column and is in particular partially immersed in a liquid bath forming in the bottoms region.
  • the bottoms liquid of the second rectification column is here evaporated in the second condenser evaporator.
  • liquid can also be cooled (supercooled) in the second condenser evaporator, by means of which liquid the second rectification column is fed from the first rectification column.
  • gas of the first or second material stream is subjected to condensation in the second condenser evaporator and, in particular, after a corresponding increase in pressure in the liquid state, is fed at least in part to the liquid taken from the first rectification column with the first or second oxygen content and used in the formation of the first or second material stream, or fed instead into a lower region of the first rectification column.
  • gas of the first or second material stream is mentioned, other gas of the first or second material stream or the respectively unaffected material stream can be used partially or completely in the manner explained (recompressed and returned to the first rectification column or expanded and discharged).
  • the advantage of the interconnection provided within the scope of the present invention is in particular that, in order to obtain identical products, approximately 3% less feed air (or approximately 3% less energy) is required, wherein, for example, a quantity of 29,300 standard cubic meters per hour of pressurized nitrogen (PGAN) and 700 standard cubic meters per hour of high-purity liquid oxygen (UHPLOX) can be provided.
  • GPN pressurized nitrogen
  • UHPLOX high-purity liquid oxygen
  • the two alternatives of the invention are in particular that on the one hand after its evaporation in the first condenser evaporator, a first portion of the first material stream is subjected to recompression to the first pressure level, and that after its evaporation in the first condenser evaporator, a second portion of the first material stream is subjected to condensation in the second condenser evaporator, and that on the other hand after its evaporation in the first condenser evaporator, a first portion of the second material stream is subjected to work-performing expansion, and that after its evaporation in the first condenser evaporator, a second portion of the second material stream is subjected to condensation in the second condenser evaporator.
  • the gas of the first or second material stream which is subjected to condensation in the second condenser evaporator after evaporation or partial evaporation in the first condenser evaporator, is subjected to condensation in the second condenser evaporator at a pressure level at which it was previously subjected to evaporation or partial evaporation in the first condenser evaporator.
  • the gas of the first or second material stream which after evaporation or partial evaporation in the first condenser evaporator is subjected to condensation in the second condenser evaporator, is transferred into the second condenser evaporator in particular using a gas line that without a compressor couples the first condenser evaporator and the second condenser evaporator.
  • a coupling realized directly and without pressure-influencing devices can be provided in this case.
  • At least a portion of a condensate formed during condensation in the first condenser evaporator is by use of a pump subjected to an increase in pressure in the liquid state.
  • the pressure increase in the liquid state is in particular carried out to the first pressure level.
  • At least a portion of the condensate formed during condensation in the first condenser evaporator and subjected to the increase in pressure in the liquid state can here be fed in the aforementioned first alternative to the liquid with the first or second oxygen content that is taken from the first rectification column and used in the formation of the first or second material stream, or be fed in the other alternative likewise mentioned into a lower region of the first rectification column.
  • gas of the first or second material stream after its evaporation or partial evaporation in the first condenser evaporator can thus be subjected to condensation in the second condenser evaporator, and after a corresponding increase in pressure in the liquid state, can be fed at least partially into a lower region of the first rectification column.
  • a “lower region” can advantageously be a position at which a first material stream evaporated in the first condenser evaporator or its liquid is taken from the first rectification column.
  • the pressurized nitrogen product from the first rectification column could also be used to heat the second condenser evaporator and be subjected to corresponding condensation.
  • a correspondingly contaminant-free pump would have to be used for further conveyance of the liquid formed. Due to the outlay associated therewith, this is extremely disadvantageous in comparison to the solutions proposed according to the invention.
  • one or more compressors can also be provided within the scope of the present invention for the recompression of the gas of the first material stream after its evaporation or partial evaporation in the first condenser evaporator; and for the expansion of the gas of the second material stream after its evaporation or partial evaporation in the first condenser evaporator, one or more expansion machines may be provided which is or are coupled to the one or more compressors. Further details of SPECTRA processes have already been explained in general terms above.
  • a tops gas of the first rectification column and thus a nitrogen product, can be obtained with a content of respectively less than 1 ppb oxygen, carbon monoxide, and/or hydrogen and a content of less than 10 ppm argon on a volume basis.
  • the bottoms liquid of the second rectification column can have a content of less than 10 ppb argon and/or 5 ppm methane on a volume basis and otherwise consist substantially of oxygen.
  • the first rectification column can be operated in such a way that the first pressure level is 7 to 14 bar absolute pressure, in particular 8 to 12 bar, and that the second pressure level is 1.2 to 5 bar, in particular 2 to 4 bar, absolute pressure.
  • all cooled compressed air to be fractionated in the process is fed into the first rectification column in gaseous form.
  • the present invention also extends to an air fractionation plant which has a first rectification column, a second rectification column, a first condenser evaporator, and a second condenser evaporator and is configured to feed the first rectification column with air and operate it at a first pressure level and to feed the second rectification column from the first rectification column and operate it at a second pressure level below the first pressure level.
  • the air fractionation plant is also configured to obtain tops gas of the first rectification column as a nitrogen product and to discharge it from the air fractionation plant and to obtain bottoms liquid of the second rectification column as an oxygen product and to discharge it from the air fractionation plant; in the first condenser evaporator to subject a first and a second material stream below the first pressure level to evaporation and to condense further tops gas of the first rectification column in the first condenser evaporator and to return it to the first rectification column as a return flow; to form the first material stream using liquid taken from the first rectification column with a first oxygen content, and to form the second material stream using liquid taken from the first rectification column with a second oxygen content above the first oxygen content; to partially or completely subject gas of the first material stream, after its evaporation or partial evaporation in the first condenser evaporator, to recompression to the first pressure level and to feed it into the first rectification column, and to subject gas of
  • means are provided which are configured to subject gas of the first or second material stream, after its evaporation or partial evaporation in the first condenser evaporator, to condensation in the second condenser evaporator and to feed at least a portion of it to the liquid taken from the first rectification column with the second oxygen content and used in the formation of the second material stream or to feed it into a lower region of the second rectification column.
  • one or more compressors are provided, and for the expansion of the gas of the second material stream after its evaporation or partial evaporation in the first condenser evaporator, one or more expansion machines mechanically coupled to the one or more compressors are provided.
  • the first condenser evaporator and the second condenser evaporator are arranged and in particular are coupled to one another without a compressor via a gas line in such a way that the gas of the first or second material stream, which after evaporation or partial evaporation in the first condenser evaporator is subjected to condensation in the second condenser evaporator, is subjected to condensation in the second condenser evaporator at a pressure level at which it was previously subjected to evaporation or partial evaporation in the first condenser evaporator.
  • FIG. 1 shows an air fractionation plant according to an embodiment of the invention.
  • FIG. 2 shows an air fractionation plant according to an embodiment of the invention.
  • FIG. 3 shows an air fractionation plant according to an embodiment of the invention.
  • FIG. 1 illustrates an air fractionation plant 100 in the form of a schematic plant diagram.
  • the central component is a distillation column system having a first rectification column 11 , a second rectification column 12 , a first condenser evaporator 111 , and a second condenser evaporator 121 .
  • the first rectification column 11 is operated at a first pressure level
  • the second rectification column 12 is operated at a second pressure level below the first pressure level.
  • a main air compressor 1 of the air fractionation plant 100 By means of a main air compressor 1 of the air fractionation plant 100 , air is sucked in from the atmosphere A via a filter (not separately designated) and compressed. After cooling in an aftercooler (likewise not designated separately) downstream of the main air compressor 1 , the feed air stream a formed in this way is further cooled in a direct contact cooler 2 operated with water W. The feed air stream a is then subjected to cleaning in an adsorber unit 3 .
  • FIG. 2.3A in Haring see above.
  • the feed air stream a is fed into the first rectification column 11 .
  • a portion of the feed air stream a would be fed into the first rectification column 11 , whereas a further portion would be routed through the second condenser evaporator 121 , which is arranged in a lower region of the second rectification column 12 , and evaporated by means of the bottoms liquid of the second rectification column 12 .
  • This further portion would be condensed in the second condenser evaporator 121 and then likewise fed into the first rectification column 11 .
  • this is not the case in the embodiments of the invention.
  • Tops gas of the first rectification column 11 is discharged from the air fractionation plant 300 in the form of a material stream d as a nitrogen product B or sealing gas C.
  • bottoms liquid of the second rectification column 12 is discharged in the form of a material stream e as an oxygen product D. It is also possible, for example, to feed into so-called run tanks for later evaporation for the provision of an internally compressed oxygen product D.
  • a first material stream g and a second material stream h below the first pressure level are subjected to evaporation.
  • Further tops gas of the first rectification column 11 is condensed in the form of a material stream i in the first condenser evaporator 111 and returned to the first rectification column 11 as a return flow.
  • a portion can also be supercooled in a supercooler 5 and provided as liquid nitrogen F.
  • a material stream I heated thereby is treated as explained in more detail below.
  • a further discharge in the form of a purge stream m or P may also be provided.
  • the first material stream g is formed using liquid taken from the first rectification column 11 with a first oxygen content
  • the second material stream h is formed using liquid (in particular bottoms liquid) taken from the first rectification column 11 with a second oxygen content above the first oxygen content.
  • gas of the first material stream g is subjected in a compressor 6 to recompression to the first pressure level and fed into the first rectification column 11 .
  • a portion indicated by a dashed line can also be returned to compression in the compressor 6 .
  • a portion of the material stream g can also be discharged into the atmosphere A in the form of a material stream n.
  • gas of the second material stream h is subjected to parallel further expansion in expansion machines 7 and 8 , combined with tops gas, which is taken in the form of a material stream o from the second rectification column 12 , and, after heating in the main heat exchanger 4 , used as regeneration gas in the adsorber unit 3 or discharged to the atmosphere A and thus discharged from the air fractionation plant 300 .
  • the expansion machine 7 is coupled to the compressor 6 , and the expansion machine 8 is coupled to a generator G.
  • a different number of corresponding machines or a different type of coupling may also be used.
  • An (oil) brake (not separately designated) may also be provided.
  • the second rectification column 12 is fed with a side stream p of the first rectification column 11 , which is passed through the second condenser evaporator 121 and fed into the second rectification column in an upper region.
  • gas of the second material stream h after its evaporation or partial evaporation in the first condenser evaporator 111 is conducted as a partial stream b through the condenser evaporator 121 and subjected to condensation.
  • a correspondingly formed liquid, further designated by b has its pressure increased by means of a pump 9 and is subsequently recombined with the second material stream h prior to its evaporation.
  • the liquid formed in the condenser evaporator 121 by condensation of gas of the second material stream h in the form of the material stream b also has its pressure increased by means of the pump 9 but is then fed into the first rectification column 11 in a lower region.
  • a partial stream of the first material stream g can also be used accordingly, as illustrated in FIG. 3 with a material stream c.
  • the air fractionation plant 300 according to FIG. 3 can otherwise be substantially identical or comparable.
  • the liquid formed in the second condenser evaporator 121 by condensation of gas of the first material stream g has its pressure increased by means of the pump 9 and is then recombined with the first material stream g before evaporation in the first condenser evaporator 111 .

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  • Separation By Low-Temperature Treatments (AREA)
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US17/597,000 2019-11-26 2020-11-24 Process and plant for low-temperature fractionation of air Abandoned US20220260312A1 (en)

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DE102008064117A1 (de) * 2008-12-19 2009-05-28 Linde Ag Verfahren und Vorrichtung zur Tieftemperaturzerlegung von Luft
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EP2789958A1 (de) 2013-04-10 2014-10-15 Linde Aktiengesellschaft Verfahren zur Tieftemperaturzerlegung von Luft und Luftzerlegungsanlage
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IL288739A (en) 2022-02-01
EP4065910A1 (de) 2022-10-05

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