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WO2024242704A1 - Système et procédé de pré-purification d'un flux de gaz d'alimentation - Google Patents

Système et procédé de pré-purification d'un flux de gaz d'alimentation Download PDF

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Publication number
WO2024242704A1
WO2024242704A1 PCT/US2023/067276 US2023067276W WO2024242704A1 WO 2024242704 A1 WO2024242704 A1 WO 2024242704A1 US 2023067276 W US2023067276 W US 2023067276W WO 2024242704 A1 WO2024242704 A1 WO 2024242704A1
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WO
WIPO (PCT)
Prior art keywords
hopcalite
layer
catalyst layer
hydrogen
stream
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PCT/US2023/067276
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English (en)
Inventor
Ralph J. MANCINI
Cem E. Celik
Matthias Grahl
Arthur C. SELOVER
Sesha Hari VEMURI
Helko Schneider
Thomas A. MCNAMARA
Original Assignee
Praxair Technology, Inc.
Linde Gmbh
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Application filed by Praxair Technology, Inc., Linde Gmbh filed Critical Praxair Technology, Inc.
Priority to PCT/US2023/067276 priority Critical patent/WO2024242704A1/fr
Publication of WO2024242704A1 publication Critical patent/WO2024242704A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/864—Removing carbon monoxide or hydrocarbons
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/10—Inorganic adsorbents
    • B01D2253/104—Alumina
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/10—Inorganic adsorbents
    • B01D2253/106—Silica or silicates
    • B01D2253/108—Zeolites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/207—Transition metals
    • B01D2255/2073—Manganese
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/207—Transition metals
    • B01D2255/20761—Copper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/10—Single element gases other than halogens
    • B01D2257/108—Hydrogen
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/50—Carbon oxides
    • B01D2257/502—Carbon monoxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/50—Carbon oxides
    • B01D2257/504—Carbon dioxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/80—Water
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/06—Polluted air
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/62—Carbon oxides

Definitions

  • the present invention relates to a system and method for removing impurities from a feed gas stream, and more particularly, to a method and apparatus for removing water, carbon dioxide, hydrogen, and carbon monoxide from a feed gas stream prior to its introduction into a cryogenic distillation system. More specifically, the present invention relates to a system and method for pre-purification of a feed air stream in a cryogenic air separation unit.
  • Background (0002) Adsorption is well established technology for the purification of gases and for the treatment of fluid waste streams. Purification and separation of atmospheric air comprises one of the main areas in which adsorption methods are widely used.
  • a pre-purification unit (PPU) situated upstream of the cryogenic distillation system is typically used that includes an upfront adsorbent layer to remove water, carbon dioxide as well as hydrocarbons and other contaminants including oxides of nitrogen.
  • PPU may also optionally include one or more catalysts targeted to remove one or more contaminants followed by a final adsorbent layer downstream of the optional catalysts to remove the contaminants produced by the catalysis process.
  • the air stream exiting the bed of molecular sieve and/or activated alumina is substantially free of carbon dioxide, water, hydrocarbons, and nitrous oxide.
  • the content of water in the compressed and pre-purified air feed stream must be less than 0.1 ppm (part per million) while the content of carbon dioxide in the compressed and pre-purified air feed stream must be less than 1.0 ppm.
  • the compressed and pre- purified air should be substantially free of heavy hydrocarbons and nitrous oxides.
  • hopcalite and ‘hopcalite material’ are not used as a tradename but rather is used generically to refer to a material that comprises a mixture of copper oxide and manganese oxide. (0009) For example, U.S.
  • Patent No.6,048,509 discloses a method and process utilizing a modified precious metal catalyst (platinum or palladium) and at least one member selected from the group consisting of iron, cobalt, nickel, manganese, copper, chromium, tin, lead and cerium on alumina) for oxidation of carbon monoxide to carbon dioxide, followed by water removal in an adsorbent layer and carbon dioxide removal in a second adsorbent layer.
  • An option for further hydrogen removal is provided with a second noble metal containing catalyst layer followed by water removal in subsequent adsorbent layers. (00010) Another example is highlighted in U.S.
  • Patent No.5,906,675 that removes carbon monoxide by means of a carbon monoxide oxidation catalyst layer (34a,34b,34c) such as single layer of hopcalite or other metal oxides and also removes hydrogen impurities using a hydrogen oxidation catalyst layer (36a, 36b,36c) containing a noble metal based catalyst.
  • This Jain reference goes on to teach that the carbon monoxide oxidation catalyst layer can be disposed upstream or downstream of the hydrogen oxidation catalyst.
  • Jain teaches that the carbon monoxide oxidation catalyst and the hydrogen oxidation catalyst can be combined as a single mixed layer (see Column 5, lines 1-17).
  • Patent No.5,906,675 to Jain goes on to teach that a final carbon dioxide adsorbent layer is disposed downstream of the carbon monoxide oxidation catalyst and hydrogen oxidation catalyst layer(s) (See column 5, lines 17-33).
  • Another Jain reference namely European Patent No. EP0904823 also discloses a similar arrangement of a carbon dioxide adsorbing layer disposed downstream of carbon monoxide oxidation catalyst and hydrogen oxidation catalyst layer(s) to clean up any remaining carbon dioxide.
  • European Patent No. EP0904823 there is also a first adsorbent layer to adsorb water and carbon dioxide upstream of the carbon monoxide oxidation catalyst and hydrogen oxidation catalyst layer(s).
  • the present invention may broadly be characterized as a system (e.g. pre- purification unit) and method of purifying a feed stream to reduce the hydrogen and carbon monoxide impurities present in the feed stream that represents clear improvements in costs and/or performance over the prior art pre-purification systems and methods.
  • a system e.g. pre- purification unit
  • method of purifying a feed stream to reduce the hydrogen and carbon monoxide impurities present in the feed stream that represents clear improvements in costs and/or performance over the prior art pre-purification systems and methods.
  • palladium and other noble metal based catalysts or rom such pre-purification systems represents tremendous value.
  • using specific layering arrangements within the pre-purification unit and associated methods wherein carbon dioxide is removed using one or more intermediate layers disposed between layers of carbon monoxide oxidation catalysts and hydrogen oxidation catalysts, the hydrogen removal performance of the pre-purification unit is greatly enhanced.
  • the present method of purifying a feed stream to reduce the hydrogen and carbon monoxide impurities comprising the steps of: (a) passing the gas stream through a first hopcalite catalyst layer and produce a first intermediate effluent, wherein the first hopcalite catalyst layer includes a first hopcalite material that comprises a mixture of copper oxide and manganese oxide; (b) passing the first intermediate effluent through an adsorbent layer disposed downstream of the first hopcalite catalyst layer, the adsorbent layer configured to remove at least carbon dioxide from the first intermediate effluent and produce a second intermediate effluent; and (c) passing the second intermediate effluent through a second hopcalite catalyst layer disposed downstream of the adsorbent layer to yield an intermediate purified stream substantially free of carbon dioxide, the second hopcalite catalyst layer includes a second hopcalite material that comprises a mixture of copper oxide and manganese oxide.
  • a differentiating feature of the above-described split layer arrangement is that the volume and/or average particle size of the first hopcalite material in the first hopcalite catalyst layer is different than the volume and/or average particle size of the second hopcalite material in the second hopcalite catalyst layer.
  • the present invention may alternatively be characterized as a system or pre-purification unit for purifying a feed stream to reduce the hydrogen and carbon monoxide impurities present in the feed stream, the system or pre-purification unit comprising: (i) a pre-purification vessel having an inlet configured to receive a stream of feed air and an outlet configured to release a purified stream substantially free of water, carbon dioxide, carbon monoxide and hydrogen; (ii) one or more initial adsorbent layers configured to receive the stream of feed air and produce a dry feed air stream substantially free of water, carbon dioxide; hydrocarbons, and nitrous oxide (N2O), (iii) a first hopcalite catalyst layer disposed downstream of the one or more initial adsorbent layers configured to remove carbon monoxide and hydrogen from the stream of feed air and produce a first intermediate effluent substantially free of carbon monoxide, wherein the first hopcalite catalyst layer includes a first hopcalite material that comprises a mixture of copper oxide and manganese oxide; (iv
  • the key differentiating feature of the above-described split layer arrangement is that the volume and/or average particle size of the first hopcalite material in the first hopcalite catalyst layer is different than the volume and/or average particle size of the second hopcalite material in the second hopcalite catalyst layer. (00019)
  • the volume of the second hopcalite material in the second hopcalite catalyst layer is more than the volume of the first hopcalite material in the first hopcalite catalyst layer and in some embodiments twice or thrice the volume of the first hopcalite material in the first hopcalite catalyst layer.
  • the average particle size of the first hopcalite material in the first hopcalite catalyst layer is different than and preferably smaller than the average particle size of the second hopcalite material in the second hopcalite catalyst layer.
  • the resulting purified stream purified stream is substantially free of water, carbon dioxide, carbon monoxide and hydrogen throughout the entire cycle time typically used with pre-purification units of air separation plants. More importantly, the above-described pre-purification unit and associated methods do not use any noble metal catalysts, and specifically no palladium catalysts resulting in significant capital cost savings compared to pre-purification units that employ such palladium catalysts or other noble metal catalysts to remove hydrogen.
  • the above-described methods of purification and pre-purification unit may also include additional process steps and/or one or more additional layers of manganese oxide and copper oxide containing catalysts as well as one or more additional adsorbent layers disposed between the catalyst layers to remove any water and carbon dioxide exiting the catalyst layers.
  • Fig.1 depicts a partial, cross-section view of a section of a pre-purification unit or pre-purification vessel suitable for use in pre-purification of a feed air stream in a cryogenic air separation unit
  • Fig.2 depicts a partial, cross-section view of a section of an alternate embodiment of a pre-purification unit or pre-purification vessel also suitable for use in pre-purification of a feed air stream in a cryogenic air separation unit
  • Fig.3 depicts a partial, cross-section view of a section of yet another embodiment of a pre-purification unit or pre-purification vessel also suitable for use in pre-purification of a feed air stream in a cryogenic air
  • the present system and method for pre-purification embodies a process for removing gaseous impurities from a feed gas stream and is targeted for applications where the purified stream is subsequently introduced into a cryogenic distillation column such as cryogenic air separation.
  • the disclosed pre-purification process comprises an adsorption and catalyst based process for removing water, hydrogen, carbon monoxide and carbon dioxide as well as other impurities from the feed stream gas.
  • the process comprises passing a feed stream gas containing these impurities through a multi-layer pre-purification vessel that is characterized as comprising at least three purification sections arranged in an adjacent manner such that the gas stream to be purified flows sequentially from the first purification section to the second purification section, and then to the third purification section all disposed within the pre-purification vessel. It is understood that the arrangement of the three purification sections and the individual layers of materials within each section may be oriented such that the flow is in an axial orientation of the pre-purification vessel or may be oriented such that the flow is in a radial direction within the pre-purification vessel.
  • pre-purification units may include two or more pre-purification vessels in which at least one of the pre-purification vessels is used for pre-purification service removing impurities from the feed gas stream while at least one other pre-purification vessel is being regenerated, preferably with a purge or regeneration gas stream.
  • the beds switch between pre-purification service and regeneration service periodically.
  • the first purification section of the pre-purifier vessel is configured to remove impurities such as water, carbon dioxide, and optionally other impurities such as heavy hydrocarbons and oxides of nitrogen.
  • the first purification section of the pre- purifier vessel may be comprised of a molecular sieve or one or more layers of adsorbents such as activated alumina, silica gel or an X type zeolite such as NaX zeolite.
  • the individual layers layer may also be a composite of these materials.
  • a hydrocarbon adsorbent is often selected from the group consisting of types A and X zeolites and silica gel.
  • an adsorbent layer may include A, X, or Y type zeolites.
  • the second purification section of the pre-purifier vessel is configured to remove carbon monoxide and hydrogen from the gas stream exiting the first purification section, with the carbon monoxide preferably removed via catalysis and adsorption while the hydrogen generally may be removed by chemisorption, adsorption and catalysis.
  • the degree to which hydrogen is removed by catalysis or via adsorption and/or chemisorption depends on the materials used within individual layers of the second purification section.
  • the third purification section of the pre-purifier unit is configured to further remove any water and carbon dioxide that exit the second purification section to produce a pre-purified gas stream substantially free of water, carbon dioxide, carbon monoxide, hydrogen, and other impurities.
  • the third purification section may be comprised of one or more layers of adsorbents such as activated alumina, silica gel or an X type zeolite such as NaX zeolite. Individual layers layer may also be a composite of such materials.
  • substantially free of hydrogen is a relative term that depends on the hydrogen content in the feed gas. For air pre-purification in a cryogenic air separation unit, substantially free of hydrogen would typically mean less than about 500 ppb hydrogen or less than 20% of the hydrogen content in the feed gas, whichever concentration is lower.
  • substantially free of carbon monoxide is also a relative term that depends on the carbon monoxide content in the feed gas and for air pre-purification applications typically would mean less than about 50 ppb carbon monoxide or less than 10% of the carbon monoxide content in the feed air, whichever concentration is lower.
  • Substantially free of carbon dioxide and substantially free of water in air pre-purification applications for cryogenic air separation units are generally understood to mean a concentration of 10 ppm or less.
  • the pre-purification vessel is configured to operate at the usual gas flows applicable for air separation units and well-known pressures employed for pre- purification of air in air separation units, generally in the range of between about 0.2 bar(a) and about 25.0 bar(a) during regeneration and/or purification steps.
  • a pre-purification unit 10 comprised of a vessel 15 configured to receive a feed gas stream at inlet 20 and deliver a purified gas stream at outlet 60.
  • a vessel 15 configured to receive a feed gas stream at inlet 20 and deliver a purified gas stream at outlet 60.
  • seven (7) layers of materials used to purify the feed gas stream are broadly characterized herein as defining three purification sections, as described below.
  • the first purification section 30 of the pre-purifier unit 10 is configured to remove impurities such as water, carbon dioxide, and optionally other impurities such as heavy hydrocarbons and oxides of nitrogen.
  • the first purification section 30 of the pre- purifier unit 10 includes three layers of adsorbents such as activated alumina, silica gel or an X type zeolite such as NaX zeolite or combinations thereof, including adsorbent layers 32, 34, and 36.
  • the second purification section 40 includes a first catalyst layer of hopcalite 41 that includes a first hopcalite material that comprises a mixture of copper oxide and manganese oxide.
  • This first hopcalite catalyst layer is sized and configured to remove most of the carbon monoxide and some of the hydrogen from the dry feed stream exiting adsorbent layer 36 and entering the second purification section 40.
  • the second purification section 40 of the pre-purifier unit 10 further comprises a second layer 43 or intermediate adsorbent layer disposed downstream of the first layer 41 configured to remove water and carbon dioxide from the gas stream exiting the first layer 41.
  • This second layer 43 is preferably a zeolite layer.
  • the second hopcalite catalyst layer includes a second hopcalite material that also comprises a mixture of copper oxide and manganese oxide. (00043)
  • the total volume, packing density, or mass of the first hopcalite material in the first hopcalite catalyst layer is different than the total volume, packing density, or mass of the second hopcalite material in the second hopcalite catalyst layer.
  • the volume of the second hopcalite material in the second hopcalite catalyst layer is more than the volume of the first hopcalite material in the first hopcalite catalyst layer and in some embodiments up to two or three times the volume of the first hopcalite material in the first hopcalite catalyst layer.
  • the volume of the respective layers is calculated by taking a cross section area of the hopcalite layer within the vessel multiplied by the thickness of the hopcalite layer.
  • the first hopcalite layer may have a layer thickness of between 0.01 meters and 0.15 meters to remove most or all of the carbon monoxide from the feed air stream while the second hopcalite layer may have a layer thickness of 0.3 meters or larger and configured to remove most of the hydrogen and any remaining carbon monoxide exiting the intermediate adsorbent layer.
  • the cross section areas of the layers will be the same and that the different thickness of the respective layers will differentiate the respective volumes.
  • the volume of the second hopcalite material will generally be two to three times the volume of the first hopcalite material.
  • the average particle size of the first hopcalite material in the first hopcalite layer is different from, and preferably smaller than the average particle size of the second hopcalite material in second hopcalite layer.
  • the differences between the first hopcalite material in the first hopcalite catalyst layer and the second hopcalite material in the second hopcalite catalyst layer may include both volume differences as well as average particle size differences.
  • Carulite ® Four alternative granular hopcalite materials also available under the tradename Carulite ® from Carus Corporation include an average particle size of 1.60 mm using a 10 x 16 mesh granular sieve with openings of about 2.0 mm and about 1.2 mm; an average particle size of 1.90 mm using a 8 x 14 mesh granular sieve with openings of about 2.4 mm and about 1.4 mm; an average particle size of 2.50 mm using a 6 x 12 mesh granular sieve with openings of about 3.35 mm and about 1.7 mm; and an average particle size of 3.6 mm using a 4 x 8 mesh granular sieve with openings of about 4.8 mm and about 2.4 mm.
  • the average particle size of the hopcalite material retained on a mesh granular sieve is calculated as the geometric mean of the diameter openings in the two adjacent mesh sieves detailed above. (00046)
  • the difference in volumes between the first hopcalite layer and the second hopcalite layer as well as the difference in average particle size between the first hopcalite material in the first hopcalite layer and the second hopcalite material in the second hopcalite layer are tailored to the purification functions of the first hopcalite layer and the second hopcalite layer.
  • the third purification section 50 of the pre-purifier unit 10 is configured to further remove any water and carbon dioxide that exit the second purification section 40 to produce a pre-purified gas stream substantially free of water, carbon dioxide, carbon monoxide hydrogen, and other impurities.
  • the purified gas stream exits the pre-purifier unit 10 via outlet 60.
  • the third purification section 50 is shown as one layer 52 of adsorbent such as activated alumina, silica gel or an X type zeolite, or mixtures thereof.
  • adsorbent such as activated alumina, silica gel or an X type zeolite, or mixtures thereof.
  • a plurality of flat separation screens 70 are preferably installed flush to the vessel wall between the various hopcalite catalyst layers 41, 45 and the adjacent adsorbent layers 36, 43, 52.
  • the separation screens are preferably made of Monel due to presence of high oxygen content in the regeneration gas.
  • there is a pre-purification unit 100 comprised of a vessel 115 configured to receive a feed gas stream at inlet 120 and deliver a purified gas stream at outlet 160.
  • the first purification section 130 of the pre-purifier unit 100 is configured to remove impurities such as water, carbon dioxide, and optionally other impurities such as hydrocarbons and oxides of nitrogen in multiple layers 132, 134, and 136 of adsorbent materials, such as activated alumina, silica gel or an X type zeolite such as NaX zeolite or combinations thereof.
  • the second purification section 140 includes a first hopcalite catalyst layer 141 configured to remove at least some of the carbon monoxide and some of the hydrogen from the dry feed stream exiting adsorbent layer 136 and entering the second purification section 140.
  • the second purification section 140 of the pre-purifier unit 100 further comprises an adsorbent layer 143 disposed downstream of the first hopcalite layer 141 configured to remove water and carbon dioxide from the gas stream exiting the first hopcalite layer 141.
  • This adsorbent layer 143 is preferably a zeolite layer.
  • Another hopcalite catalyst layer 145 is disposed downstream of the adsorbent layer 143 and is configured to further remove hydrogen and carbon monoxide from gas stream exiting the second layer 143.
  • Another adsorbent layer 147 configured to remove water and carbon dioxide from the gas stream exiting the second hopcalite layer 145 is disposed downstream of the second hopcalite layer 145.
  • a third hopcalite layer 149 configured to remove substantially all of the remaining hydrogen is disposed downstream of the adsorbent layer 147. Similar to the embodiment of Fig.1, a plurality of Monel separation screens 170 are preferably installed between the various hopcalite catalyst layers 141, 145, 149 and the adjacent adsorbent layers 136, 143, 147, 152.
  • the third purification section 150 of the pre-purifier unit 100 is shown as one layer 152 of adsorbent such as activated alumina, silica gel or an X type zeolite, or mixtures thereof and is configured to further remove any water and carbon dioxide that exit the second purification section 140 to produce a pre-purified gas stream substantially free of water, carbon dioxide, carbon monoxide hydrogen, and other impurities.
  • adsorbent such as activated alumina, silica gel or an X type zeolite, or mixtures thereof
  • an advantageous feature in the three layer hopcalite arrangement is that the volume and/or average particle size of the hopcalite materials in each hopcalite catalyst layer may be different than the volume and/or average particle size of the hopcalite materials in the other hopcalite catalyst layers.
  • the second purification sections 40, 140 of the pre-purifier units 10, 100 may be broadly characterized as having two or more separate layers of hopcalite with the successive layers of the hopcalite separated by a zeolite adsorbent layer that removes water and carbon dioxide produced in the hopcalite layers.
  • Fig.3 there is shown yet another embodiment of the present system and method for pre-purification of a feed gas stream that includes a vessel 215 configured to receive a feed gas stream at inlet 220 and deliver a purified gas stream at outlet 260.
  • the first purification section 230 includes a layer of alumina 233 and a layer of zeolite based molecular sieve 235 while the third purification section 250 of the pre-purifier unit 200 is configured with a capping layer 252 of zeolite based molecular sieve to remove impurities such as water, carbon dioxide exiting the second purification section 240.
  • the various layers of adsorbent materials in the first and third purification sections may be activated alumina, silica gel or an X type zeolites or combinations thereof to remove impurities such as water, carbon dioxide, and optionally other impurities in the gas streams flowing through such layers.
  • the second purification section 240 of the pre-purifier unit 200 includes a hopcalite layer 241 configured to remove most of the carbon monoxide and some of the hydrogen from the dry gas stream exiting adsorbent layer 236 and entering the second purification section 240 followed by an adsorbent layer 243 disposed downstream of the hopcalite layer 241 configured to remove water and carbon dioxide from the gas stream exiting the hopcalite layer 241.
  • This adsorbent layer 243 is preferably a zeolite based molecular sieve.
  • the embodiment shown in Fig.3 includes a layer of noble metal catalyst such as 0.5wt%Pd/Al 2 O 3 instead of additional hopcalite catalyst layers.
  • adsorbent layer 243 that has been cleansed of carbon dioxide and water is partially oxidized to water and/or adsorbed by this catalyst layer 244 while any residual carbon monoxide escaping the upstream hopcalite layer may also be oxidized in this layer.
  • Much of the water produced in the partial oxidation of hydrogen may be adsorbed in the Al 2 O 3 catalyst support while some of the water and carbon dioxide produced will continue to the third purification section 250.
  • a plurality of Monel separation screens 270 are preferably installed between the various hopcalite catalyst layers 241 or catalyst layer 244 and the adjacent adsorbent layers 236, 243, 252.
  • air pre-purification systems use two or more pre-purification units or vessels so as to allow continuous production of purified air.
  • one or more of the pre-purification units is purifying the feed air
  • one or more other pre-purification units are being regenerated, preferably using a process widely known as thermal regeneration.
  • the thermal regeneration process acts to desorbs the water and carbon dioxide from various layers in the pre-purifier units while also restoring the hydrogen adsorption capacity of the hopcalite catalyst layers and other catalyst layers.
  • Thermal regeneration is preferably done using a multi-step process that often involves the following four steps: (i) depressurizing the vessel to lower pressures suitable for regeneration; (ii) heating the layers within the vessel to desorb the water and carbon dioxide from various layers and restore the hydrogen adsorption capacity of the hopcalite catalyst layers and/or other catalyst layers; (iii) cooling the layers within the vessel back to temperatures suitable for the purification process; and (iv) repressurizing the vessel back to the higher operating pressures required for the purification process. While thermal regeneration is preferred, it is contemplated that the present system and methods could be used with pressure swing adsorption based pre-purifiers or even hybrid type pre-purifiers.
  • Thermal regeneration is preferably conducted at lower pressures such as 1.0 to 1.5 bar(a) compared to the purification process and must be conducted at temperatures of at least 180 °C, and more preferably at temperatures of about 190° C, or more, subject to appropriate safety requirements.
  • the heating step in the thermal regeneration process is typically conducted by heating a purge gas to produce a stream of hot purge gas which is fed to vessel via outlet 60, 160, 260 and which traverses the layers of the pre-purifier unit 10, 100, 200 in reverse order compared to the above-described purification process.
  • the purge gas may be taken as a portion of the product gas or from waste gas from the distillation columns of the cryogenic air separation unit.
  • the catalyst layers and adsorbent layers are regenerated.
  • the effluent purge gas exiting the pre-purification unit 10, 100, 200 via the inlet 20, 120, 220 is typically vented.
  • the pre-purification unit is then cooled using a cool purge gas generally at a temperature from about 10° C up to 50° C that flows through the pre-purification unit in the same direction as the hot purge gas. After cooling, the vessel is repressurized to the higher operating pressures required by the purification process.
  • the regeneration steps are conducted as described for a predetermined period of time, typically referred to as the cycle time after which the service or functions of the pre-purification units are switched so that vessels previously regenerating come "on line' and initiates the purification process while vessels previously purifying the feed air go "off-line' and initiate the regeneration process.
  • Typical pre-purification cycle times for high-purity or ultra-high purity nitrogen producing air separation plants is between about 240 minutes and 480 minutes. In this manner, each pre-purification unit alternates between purification service and regeneration service to maintain continuous production of purified air substantially free of carbon dioxide, water, carbon monoxide, hydrogen and other impurities.
  • the pre-purifier vessels depicted in Figs 1-3. are preferably dense loaded.
  • Dense loading provides the most consistent and uniform packing of adsorbents and catalysts with minimal leveling of the layers required. Furthermore, dense packing minimizes adsorbent settling. Such dense packing for pre-purifiers designed for carbon monoxide and hydrogen removal is optional and may be utilized for all layers in the bed to ensure integrity and uniform depth. Because of relatively thin layers in second purification section for removal of carbon monoxide and hydrogen, including multiple layers of hopcalite and adsorbent layers, as well as any noble metal based catalyst that may be used, it is important to minimize the shifting and/or settling of the layers in order to maintain a uniform depth of the layers over the life of the pre-purifier unit.
  • Example 1 (00061) The embodiment of Fig.1 has been evaluated using computer based simulations and models to demonstrate the expected performance of the pre-purification unit and Table 1 shows modeling data for the gas streams entering the pre-purifier and exiting each individual layer of material in the pre-purifier unit.
  • the flow rate through the pre-purifier is modeled at about 99000 Nm 3 /h for a cycle time of between 2 to 6 hours.
  • the following discussion focuses on the second purification section of the pre-purifier unit in an effort to demonstrate performance and cost benefits of this arrangement compared to prior art pre-purification systems.
  • the initial hopcalite layer or first catalyst layer is about 18 cm in length and configured to remove most of the carbon monoxide via an oxidation with the copper and magnesium oxides in the catalyst layer to produce carbon dioxide most of which may be adsorbed in the hopcalite layer and some of which exits the first catalyst layer.
  • a first portion of the hydrogen in the gas stream traversing the first catalyst layer is oxidized to produce water while a second portion of the hydrogen in the gas stream traversing the first catalyst layer is adsorbed in the first catalyst layer while a third portion of the hydrogen impurities in the gas stream traversing the first catalyst layer passes through the first catalyst layer.
  • Table 1 shows a distinct increase in water impurities and carbon dioxide in the gas stream exiting the first catalyst layer (i.e. not absorbed in the first catalyst layer), presumably from oxidation of the hydrogen and carbon monoxide, respectively.
  • the hydrogen reduction from about 1000 ppb to 100 ppb is a net reduction of about 90% while the carbon monoxide shows a net reduction of about 99.9% from about 1000 ppb to about 1.0 ppb.
  • the hydrogen impurities are being removed in this first hopcalite layer at an average rate of 5.0% per cm of hopcalite.
  • the second layer in the second section of the pre-purifier unit is a zeolite based adsorbent about 20 cm in length that removes the water impurities from about 1.0 ppm to about 0.01 ppm and also removes carbon dioxide from about 1.0 ppm to less than about 0.01 ppm.
  • the third layer in the second section of the pre-purifier unit is a second hopcalite layer about 10 cm in length that receives the gas stream cleansed of water and carbon dioxide exiting the second layer and is configured to further remove the hydrogen from about 100 ppm to about 5 ppm for a reduction of about 95% of the remaining hydrogen and removes any remaining carbon monoxide to levels below 0.1 ppb resulting in a gas substantially free of carbon monoxide.
  • the hydrogen impurities are being removed at an average rate of 9.5% per cm of hopcalite compared to an average rate of hydrogen removal of 5.0% per cm of hopcalite in the first layer of hopcalite catalyst.
  • Example 2 (00065) The embodiment of Fig.2 has also been evaluated using computer based simulations and models to also demonstrate the expected performance of the depicted multi-layer hopcalite based pre-purification unit and Table 2 shows modeling data for the gas streams entering the pre-purifier shown and described with reference to Fig.2.
  • the materials are the same as in the previous example and the flow rate of the air through the pre-purifier is also modeled at 99000 Nm 3 /h for a cycle time of between 2 hours and 6 hours.
  • Impurities (at Exit of Layer) PU Layer Material Length CO( b) H 2 ( b) H 2 O( m) CO 2 ( m) (00066)
  • the initial hopcalite layer or first catalyst layer in the second purification section identified as layer 4 in Table 2
  • a first portion of the hydrogen in the gas stream traversing the first catalyst layer is oxidized to produce water while a second portion of the hydrogen in the gas stream traversing the first catalyst layer is adsorbed while a third portion of the hydrogen impurities in the gas stream traversing the first catalyst layer passes through the first catalyst layer.
  • the hydrogen and carbon monoxide profiles depicted in Table 2 shows a distinct increase in water impurities and carbon dioxide in the gas stream exiting the first catalyst layer (i.e. impurities not absorbed in the first catalyst layer), presumably produced from oxidation of hydrogen and carbon monoxide, respectively.
  • the hydrogen reduction from about 1000 ppb to 321 ppb is a net reduction of only about 68% while the carbon monoxide shows a net reduction of about 99.9% from 1000 ppb to about 1.0 ppb.
  • the second layer in the second section of the pre-purifier unit identified as layer 5 is a zeolite based adsorbent about 20 cm in length that removes the water impurities from about 0.7 ppm to about 0.01 ppm and removes carbon dioxide from about 1.0 ppm to less than 0.01 ppm.
  • the third layer in the second section of the pre-purifier unit identified as layer 6 is another hopcalite layer about 10 cm in length that receives the gas stream cleansed of water and carbon dioxide exiting the second layer and is configured to further remove the hydrogen from about 321 ppm to about 60 ppm for a reduction of about 81% of the remaining hydrogen and removes any remaining carbon monoxide to levels below 0.1 ppb resulting in a gas substantially free of carbon monoxide.
  • the removal of hydrogen and substantially all of the carbon monoxide yields an exit gas with about 0.3 ppm water and up to about 0.1 ppm of carbon dioxide, with much of the produced water and carbon monoxide being adsorbed in the third layer (i.e. second hopcalite layer).
  • the fourth layer in the second section of the pre-purifier unit identified as layer 7 is another zeolite based adsorbent that again removes the water impurities from about 0.3 ppm back down to about 0.01 ppm level and removes carbon dioxide from about 0.1 ppm to less than 0.01 ppm levels.
  • This fourth layer of zeolite based adsorbent is only about 10 cm in length, thus helping reduce cost of materials.
  • the fifth layer in the second section of the pre-purifier unit is identified as layer 7 and is yet another hopcalite layer of only about 8.0 cm in length that receives the gas stream exiting the fourth layer and is configured to further remove most of the remaining hydrogen impurities from about 60 ppb level to about 5 ppb level for a reduction of about 92% of the remaining hydrogen to yield an effluent gas that is substantially free of both hydrogen and carbon monoxide.
  • layer 7 is yet another hopcalite layer of only about 8.0 cm in length that receives the gas stream exiting the fourth layer and is configured to further remove most of the remaining hydrogen impurities from about 60 ppb level to about 5 ppb level for a reduction of about 92% of the remaining hydrogen to yield an effluent gas that is substantially free of both hydrogen and carbon monoxide.
  • the first hopcalite layer is 10 cm in length and removes 68% of the hydrogen in the stream traversing that first hopcalite layer whereas the second hopcalite layer is also 10 cm in length yet removes 81% of the hydrogen in the stream traversing that second hopcalite layer.
  • the third hopcalite layer is only about 8 cm in length yet removes about 92% of the hydrogen in the stream traversing that third hopcalite layer. In this manner, hydrogen removal is performed in a cascading manner where the efficiency of hydrogen removal improves in successive hopcalite layers.
  • hopcalite based pre-purifier design with this cascading hydrogen removal, one can improve hydrogen removal by designing the first hopcalite layer to remove between 50% and less than 90% of the hydrogen in the feed stream, and in some embodiments remove between 50% and less than 75% of the hydrogen in the feed stream.
  • the last hopcalite layer is preferably configured to remove more than 90% of the hydrogen entering the last hopcalite layer.
  • Intermediate hopcalite layers, if used, are preferably designed or configured to remove relatively more hydrogen than the preceding hopcalite layer, measured as a percentage of hydrogen in the gas stream entering the hopcalite layer.
  • Fig.4 shows a graph of data obtained from a plurality of laboratory tests showing the hydrogen removal characteristics of a hopcalite catalyst, specifically a 22.86 cm long bed of Carulite ® .
  • the laboratory tests passed air at a temperature of 20° C (i.e. curve 301) or 40° C (i.e. curves 302 and 303), a pressure of about 9.6 bar(a), and a flow rate of 13.3 slpm.
  • the feed air stream had 3 ppm of hydrogen and either 10 ppm of carbon monoxide (i.e.
  • curves 301 and 302) or 1 ppm of carbon monoxide i.e. curve 303.
  • Curve 301 represents test conditions with the air stream at 20° C, the hydrogen level at the inlet of 3ppm and the carbon monoxide level at the inlet of 10 ppm and shows a hydrogen ratio of about 0.7 after 100 minutes and about 0.85 after 350 minutes.
  • Increasing the temperature to 40° C, while keeping the 3 ppm hydrogen level at the inlet and 10 ppm carbon monoxide level at the inlet improves the hydrogen removal performance as shown in curve 302.
  • curve 302 shows a hydrogen ratio of about 0.4 after 100 minutes and about 0.7 after 350 minutes.
  • Curve 303 shows even better hydrogen removal performance with the feed air temperature at 40° C but reducing the carbon monoxide concentration in the feed air to 1 ppm while keeping the 3 ppm hydrogen impurity level at the inlet.
  • curve 303 shows a hydrogen ratio of about 0.3 after 100 minutes and about 0.5 after 350 minutes.
  • Fig.5 shows a graph of data obtained from a plurality of laboratory tests showing the hydrogen removal characteristics of a 22.86 cm long bed of a palladium based catalyst such as 0.5wt%Pd/Al 2 O 3.
  • Test Bed #1610 having a 6 inch bed of 4x8 hopcalite catalyst 611(Carulite from Carus Corporation) 611 and having approximately 27 grams of catalyst was compared to a split bed arrangement 620 having a first 3 inch bed of 4x8 hopcalite catalyst (Carulite from Carus Corporation) 622 followed by a 3 inch bed of 8x12 APG-III Molecular Sieve 624 and a second 3 inch bed of 4x8 hopcalite catalyst (Carulite from Carus Corporation) 626 with the split bed arrangement 620 also having a total of ⁇ 27 grams of hopcalite catalyst (TestBed #2).
  • Feed conditions to TestBed # 1 and TestBed #2 comprised synthetic air streams 611, 621 at about 10 bara and 25°C and with 3 ppm of hydrogen and 10 ppm of carbon monoxide added as contaminants.
  • the flow rate of the synthetic air streams 611, 621 was varied to simulate two different residence times in the hopcalite catalyst beds.
  • a first flow rate of 5.8 standard liters per minute (slpm) the residence time through the full 6 inches of Carulite was a total of 3.0 seconds or 1.5 seconds in each of the 3 inch layers of Carulite in the split layer arrangement.
  • the hydrogen break-through in the single 6 inch layer of hopcalite was almost 200 ppb (curves 701, 702) while the hydrogen break-through in the split layer arrangement was less than 70 ppb (curves 711, 712).
  • the hydrogen break-through in the single 6 inch layer of hopcalite was over 500 ppb (curves 701, 702) while the hydrogen break-through in a split layer arrangement was about 200 ppb (curves 711, 712).
  • the carbon dioxide break-through in the single 6 inch layer of hopcalite was almost 1 ppm (curve 801) while the carbon dioxide break-through in the split layer arrangement was steady at about 0.3 ppm (curve 811).
  • the carbon dioxide break-through in the single 6 inch layer of hopcalite was over 2 ppm (see curve 801) while the carbon dioxide break-through in the split layer arrangement was steady at about 0.3 ppm (see curve 811).
  • the ‘split bed’ arrangement shows up to 25% better hydrogen capture performance at any given moment of time compared to than the single layer hopcalite arrangement, again, depending on feed stream contaminants as well as other operating conditions and variables. (00085)
  • the vastly superior results provides clear technical benefits in situations where the residence time through the hopcalite catalyst is longer (e.g.3.0 seconds) or shorter (e.g.1.4 seconds).
  • the pre-purification unit (PPU) designer can reduce the amount of hopcalite material used to achieve the same level of hydrogen removal at traditional PPU cycle times compared to a single hopcalite layer arrangement, resulting in lower material costs.
  • a third benefit of the ‘split layer’ arrangement is the elimination or reduction of the palladium catalyst layer which saves significant costs, as the cost of many noble metal catalyst materials, including palladium catalyst materials continue to rapidly increase. In many air separation plants, achieving the required hydrogen removal targets while eliminating the use of palladium based catalyst materials saves significant capital costs, in many cases upwards of $1,000,000 or more per air separation plant.

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Abstract

L'invention concerne un système et un procédé de pré-purification d'un flux de gaz d'alimentation qui est particulièrement approprié pour la pré-purification d'un flux d'air d'alimentation dans une unité de séparation d'air cryogénique. Les systèmes et les procédés de pré-purification divulgués sont conçus pour éliminer sensiblement la totalité de l'hydrogène, du monoxyde de carbone, de l'eau, et des impuretés de dioxyde de carbone à partir d'un flux d'air d'alimentation et est particulièrement approprié pour une utilisation dans une installation d'azote de pureté élevée ou de pureté ultra-élevée. Les systèmes et les procédés de pré-purification utilisent de préférence deux couches séparées ou plus de catalyseur de hopcalite (41, 45) avec les couches successives de l'hopcalite séparées par une couche d'adsorbant de zéolite (43) qui élimine l'eau et le dioxyde de carbone produit dans les couches de hopcalite. Les couches séparées (41, 45) du catalyseur de hopcalite présentent de préférence des volumes différents et/ou des tailles de particules moyennes différentes des matériaux à base de hopcalite.
PCT/US2023/067276 2023-05-22 2023-05-22 Système et procédé de pré-purification d'un flux de gaz d'alimentation WO2024242704A1 (fr)

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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0904823A2 (fr) 1997-09-30 1999-03-31 The Boc Group, Inc. Méthode pour la purification de gaz
US5906675A (en) 1997-09-30 1999-05-25 The Boc Group, Inc. Air purification process
US6048509A (en) 1997-05-23 2000-04-11 Nippon Sanso Corporation Gas purifying process and gas purifying apparatus
US6093379A (en) 1998-12-04 2000-07-25 Air Products And Chemicals, Inc. Purification of gases
US20030064014A1 (en) 2001-08-03 2003-04-03 Ravi Kumar Purification of gases by pressure swing adsorption
US8940263B2 (en) 2013-04-10 2015-01-27 Air Products And Chemicals, Inc. Removal of hydrogen and carbon monoxide impurities from gas streams
US20220054976A1 (en) * 2020-08-19 2022-02-24 Ralph J. Mancini Method and system for pre-purification of a feed gas stream
EP3991826A1 (fr) * 2020-10-29 2022-05-04 Air Products And Chemicals, Inc. Élimination d'impuretés d'hydrogène dans des flux gazeux

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6048509A (en) 1997-05-23 2000-04-11 Nippon Sanso Corporation Gas purifying process and gas purifying apparatus
EP0904823A2 (fr) 1997-09-30 1999-03-31 The Boc Group, Inc. Méthode pour la purification de gaz
US5906675A (en) 1997-09-30 1999-05-25 The Boc Group, Inc. Air purification process
US6093379A (en) 1998-12-04 2000-07-25 Air Products And Chemicals, Inc. Purification of gases
US20030064014A1 (en) 2001-08-03 2003-04-03 Ravi Kumar Purification of gases by pressure swing adsorption
US8940263B2 (en) 2013-04-10 2015-01-27 Air Products And Chemicals, Inc. Removal of hydrogen and carbon monoxide impurities from gas streams
US20220054976A1 (en) * 2020-08-19 2022-02-24 Ralph J. Mancini Method and system for pre-purification of a feed gas stream
EP3991826A1 (fr) * 2020-10-29 2022-05-04 Air Products And Chemicals, Inc. Élimination d'impuretés d'hydrogène dans des flux gazeux

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