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WO2025120157A1 - Installation de réduction directe et procédé associé - Google Patents

Installation de réduction directe et procédé associé Download PDF

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Publication number
WO2025120157A1
WO2025120157A1 PCT/EP2024/085076 EP2024085076W WO2025120157A1 WO 2025120157 A1 WO2025120157 A1 WO 2025120157A1 EP 2024085076 W EP2024085076 W EP 2024085076W WO 2025120157 A1 WO2025120157 A1 WO 2025120157A1
Authority
WO
WIPO (PCT)
Prior art keywords
treatment
carbon dioxide
gas
reactor
exhaust gas
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/EP2024/085076
Other languages
English (en)
Inventor
Andrea Tavano
Marco LAPASIN
Stefano MAGGIOLINO
Jorge Eugenio MARTINEZ MIRAMONTES
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Danieli and C Officine Meccaniche SpA
HYL Technologies de SA de CV
Original Assignee
Danieli and C Officine Meccaniche SpA
HYL Technologies de SA de CV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Danieli and C Officine Meccaniche SpA, HYL Technologies de SA de CV filed Critical Danieli and C Officine Meccaniche SpA
Publication of WO2025120157A1 publication Critical patent/WO2025120157A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B13/00—Making spongy iron or liquid steel, by direct processes
    • C21B13/0073—Selection or treatment of the reducing gases
    • 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
    • B01D53/02—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 by adsorption, e.g. preparative gas chromatography
    • B01D53/04—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 by adsorption, e.g. preparative gas chromatography with stationary adsorbents
    • B01D53/047—Pressure swing adsorption
    • 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
    • B01D53/14—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 by absorption
    • B01D53/1456—Removing acid components
    • B01D53/1475—Removing carbon dioxide
    • 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
    • B01D2258/00—Sources of waste gases
    • B01D2258/02—Other waste gases
    • B01D2258/025—Other waste gases from metallurgy plants
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
    • C21B2100/20—Increasing the gas reduction potential of recycled exhaust gases
    • C21B2100/22—Increasing the gas reduction potential of recycled exhaust gases by reforming
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
    • C21B2100/20—Increasing the gas reduction potential of recycled exhaust gases
    • C21B2100/26—Increasing the gas reduction potential of recycled exhaust gases by adding additional fuel in recirculation pipes
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
    • C21B2100/20—Increasing the gas reduction potential of recycled exhaust gases
    • C21B2100/28—Increasing the gas reduction potential of recycled exhaust gases by separation
    • C21B2100/282—Increasing the gas reduction potential of recycled exhaust gases by separation of carbon dioxide
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
    • C21B2100/40—Gas purification of exhaust gases to be recirculated or used in other metallurgical processes
    • C21B2100/44—Removing particles, e.g. by scrubbing, dedusting
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
    • C21B2100/60—Process control or energy utilisation in the manufacture of iron or steel
    • C21B2100/66—Heat exchange
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/10—Reduction of greenhouse gas [GHG] emissions
    • Y02P10/122—Reduction of greenhouse gas [GHG] emissions by capturing or storing CO2
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/10—Reduction of greenhouse gas [GHG] emissions
    • Y02P10/134—Reduction of greenhouse gas [GHG] emissions by avoiding CO2, e.g. using hydrogen

Definitions

  • the present invention relates to a direct reduction plant of the zero-reformer type, or alternatively of the type with a reformer outside the reactor, and to the process thereof, adapted, in particular, to produce metallic iron by direct reduction of iron oxides using reducing gas.
  • the systems for the production of direct reduced iron (DRI) ore of the known type comprise a reactor, into which iron oxide in the form of pellets and/or lumps is charged, and a line for treating and supplying reducing gas, comprising hydrogen and/or carbon monoxide and adapted to reduce said iron oxide in the reactor.
  • the reducing gas is injected into a reaction chamber, or reactor, at high temperature.
  • the reactor can be of the fixed bed type, the moving bed type, the fluidized bed type, or of the rotary or kiln type.
  • the reducing gas is typically introduced into the central part of the reactor, made to rise in counterflow through the iron oxide, and then extracted, reprocessed, and recycled in a reduction circuit.
  • the exhaust gas coming out of the reactor is dedusted, deprived of reaction products (H2O and CO2), and then compressed; it is then mixed with a make-up gas (natural gas, COG, gas obtained in a reformer, Corex Gas, syngas, hydrogen, etc.).
  • a make-up gas natural gas, COG, gas obtained in a reformer, Corex Gas, syngas, hydrogen, etc.
  • the flow of gas defined by the mixture of the new make-up gas and the exhaust gas recycled after appropriate treatment, is sent to a heating unit, which brings it to the temperature required by the reduction process, normally higher than 850 °C.
  • the heated flow of reducing gas, into which oxygen can be injected to increase the temperature thereof further, is sent to the reactor, in which the iron oxides to be reduced are introduced from above in the form of pellets and/or lumps and flow downwardly there-through, while the DRI (reduction product) is extracted at the opposite end of said reactor and sent, by means of a pneumatic conveying system or by gravity or by means of belts, to a blast furnace or an electric arc furnace or an oxygen converter or any device capable of melting the produced DRI.
  • oxygen is removed from iron ore by means of chemical reactions with hydrogen and carbon monoxide to obtain DRI with a high level of metallization (ratio of metallic iron to total iron contained in the DRI).
  • the overall reduction reactions involved in the process are well-known and are shown below:
  • Hydrogen and carbon monoxide react with the oxygen of the iron oxide and are transformed into water and carbon dioxide according to the reactions (1 ) and (2).
  • unreacted H 2 and CO are also present in the exhaust gas coming out of the reactor.
  • the exhaust gas is treated as described above to recover these reductants.
  • the known direct reduction plants have a large number of devices along the gas circulation circuit. Furthermore, because of the high flow of gas to be processed and the pressures involved, some of these devices are large in size and thus energy-intensive. Adequate instruments are also needed for control and safety.
  • Figure 1 diagrammatically shows a direct reduction plant in which a recovery and treatment line 10, arranged downstream of the reactor 1 , recovers and treats the exhaust gas coming out of the reactor, and communicates downstream with a treatment and feeding line 11 , arranged upstream of reactor 1 , which treats the process gas, obtained by mixing the make-up gas with the exhaust gas treated in the recovery and treatment line 10, to feed the reduction area 2 of the reactor 1 with said process gas.
  • a recovery and treatment line 10 arranged downstream of the reactor 1 , recovers and treats the exhaust gas coming out of the reactor, and communicates downstream with a treatment and feeding line 11 , arranged upstream of reactor 1 , which treats the process gas, obtained by mixing the make-up gas with the exhaust gas treated in the recovery and treatment line 10, to feed the reduction area 2 of the reactor 1 with said process gas.
  • the recovery and treatment line 10 comprises in succession in the end stretch thereof, proximal to said treatment and feeding line 11 , a compressor 42, a cooling device 43 to cool the gas flow heated by compression, and a carbon dioxide removal device 50.
  • the treatment and feeding line 11 comprises, in the initial stretch thereof, proximal to the carbon dioxide removal device 50, a humidifier 51 required to increase the water content of the process gas, thereby preventing carbon deposition inside both the heating unit 18 of the process gas and the conduits defining the path of the hot process gas to the reactor 1 .
  • US8940076B2 A further example of direct reduction plant is disclosed in US8940076B2 (see, for example, Figure 2 of US8940076B2) where, into addition to the carbon dioxide absorption removal system 38/40, along the recovery and treatment line there are provided two compressors 34, 54 and a further adsorption unit 140 of the PSA (pressure swing adsorption) type for separation of the gases of large molecules, whereas in the treatment and feeding line it is necessary to provide a humidifier 66 to humidify the process gas.
  • PSA pressure swing adsorption
  • the cleaned and cooled resulting spent gas stream 32 is divided, with a small first portion 33 containing CO, CO2, H2, and methane, being purged from the system as tail gas (which may be used as fuel in the gas heater 72).
  • the other major portion 35 of the cool gas stream 32 is subsequently pressurized by compressor 34 before being fed, as stream 36, to an absorber column 38 of the CO2 chemical absorption removal system, for example using an amine solvent.
  • the upgraded reducing gas effluent 44 is subsequently divided into two streams.
  • a first stream 58 is directed to humidifier 66 and is recycled to the reduction zone 12 of reactor 10, while a second stream 46 is further split into two portions.
  • a first portion 48 is treated in the physical adsorption unit 140 of the PSA type for separation of the gases of large molecules, mostly carbon monoxide and methane from the lighter molecules contained in said gas stream e.g. hydrogen, nitrogen and water.
  • a hydrogen rich stream 74 is produced and subsequently fed as fuel to burners of heater 72.
  • a small second portion 50 of stream 46 is purged from the system as tail gas regulated by valve 51 and is burned in the process gas heater 72.
  • stream 48 The remaining portion of stream 48, after being dehydrogenated, is removed from the PSA unit 140 as stream 52 mainly composed of CO and CH4 and is subsequently compressed by compressor 54 before being added directly to the upgraded recycled gas stream 58 coming from absorber column 38.
  • Compressed stream 56 after being combined with upgraded reducing gas 58 as stream 60 and further combined with the make-up stream of natural gas 64, is fed to humidifier 66 where its water content is adjusted so that the amount of water present ranges between 3% and 10% by volume of stream 70.
  • CO2 emissions are generated by the selective removal of CO2 from the recycled exhaust gas from the reactor, after the iron oxide reduction reactions, in addition to the emissions released through the flue of the heating unit 18 of the reducing gas.
  • the process described above which is supplied with natural gas to facilitate the methane reforming reactions inside the reduction reactor, still ensures a good H2/CO ratio in the composition of the reducing gas which is introduced into the reactor.
  • a direct reduction plant for a direct reduction of iron oxides which comprises a gas circulation circuit comprising:
  • a recovery and treatment line arranged downstream of the reactor, to recover and treat exhaust gas exiting the reactor;
  • a treatment and feeding line arranged upstream of the reactor, to treat a process gas, obtained by mixing the make-up gas with the exhaust gas treated in the recovery and treatment line, and to feed the reduction area of the reactor with said process gas;
  • the recovery and treatment line communicates, downstream of the reactor, with said treatment and feeding line;
  • the treatment and feeding line comprises a heating unit, upstream of the reactor, to heat the process gas to a temperature suitable for introduction into the reactor;
  • the recovery and treatment line comprises only one compressor; wherein the recovery and treatment line, in the end stretch thereof proximal to said treatment and feeding line, comprises
  • said only one compressor arranged between said carbon dioxide removal device and said heating unit, to compress the exhaust gas free of carbon dioxide towards said treatment and feeding line, preferably directly towards the heating unit.
  • process gas indicates the gas mixture obtained by mixing the make-up gas, containing gaseous hydrogen and/or gaseous hydrocarbons, with the exhaust gas treated in the recovery and treatment line.
  • a direct reduction process for a direct reduction of iron oxides is provided, which can be carried out by means of the aforesaid plant, and which comprises the following steps when fully operational: a) recovering and treating the exhaust gas coming out of the reactor by means of the recovery and treatment line; b) feeding process gas into a reduction area of the reactor by means of the treatment and feeding line, said process gas being obtained by mixing the makeup gas, coming from the external source, with the exhaust gas treated in the recovery and treatment line; wherein, before the exhaust gas is introduced into the treatment and feeding line, there are provided in succession a removal of carbon dioxide from said exhaust gas by means of the carbon dioxide removal device and a compression of the exhaust gas free of carbon dioxide, by means of the only one compressor, towards said treatment and feeding line.
  • the catalytic reforming of the process gas is carried out in situ inside the reactor, so that the process gas undergoes no additional catalytic reaction beyond the catalytic reactions which take place in the reactor, or inside an external reductant generation unit.
  • Figure 1 is a diagram of an embodiment of a direct reduction plant according to the prior art
  • Figure 2 is a diagram of an embodiment of a direction reduction plant according to the invention.
  • FIG. 2 An example of a direct reduction plant, which is the object of the present invention, is shown in Figure 2 and comprises a gas circulation circuit provided with:
  • a recovery and treatment line 10 arranged downstream of the reactor 1 , to recover and treat the exhaust gas coming out of the reactor 1 ;
  • a treatment and feeding line 11 arranged upstream of the reactor 1 , to treat a process gas, obtained by mixing the make-up gas with the exhaust gas treated in the recovery and treatment line 10, and to feed the reduction area 2 of the reactor 1 with said process gas.
  • the recovery and treatment line 10 communicates downstream with the treatment and feeding line 11 , this latter comprising a heating unit 18, upstream of the reactor 1 , to heat the process gas to a temperature suitable for introduction into the reactor 1 .
  • this plant is configured to carry out a process of the zero-reformer type, in which the catalytic reforming of the process gas is carried out in situ inside the reactor 1 , so that the process gas undergoes no additional catalytic reaction beyond the catalytic reactions which take place inside the reactor 1.
  • the plant can be configured to carry out a process in which the catalytic reforming of the process gas is carried out inside an external reductant generation unit.
  • the recovery and treatment line 10 comprises in its end stretch, proximal to said treatment and feeding line 11 , a carbon dioxide removal device 50 to remove carbon dioxide from the exhaust gas, said removal device being arranged upstream of a compressor 42, associated to the carbon dioxide removal device 50, preferably directly connected to said carbon dioxide removal device 50, to compress the exhaust gas towards said treatment and feeding line 11 .
  • the whole recovery and treatment line 10 comprises only one compressor 42 and, in said end stretch thereof proximal to said treatment and feeding line 11 , comprises
  • said only one compressor 42 arranged between said carbon dioxide removal device 50 and the heating unit 18, to compress the exhaust gas, free of carbon dioxide, towards the treatment and feeding line 11 , preferably directly towards the heating unit 18.
  • the portion of the treatment and feeding line 11 arranged between the only one compressor 42 and the heating unit 18, has no additional components along the extension thereof.
  • neither humidifier nor further heat exchange devices are provided in the treatment and feeding line 11.
  • Providing the only one carbon dioxide removal device 50 upstream of the only one compressor 42 has the advantage of not needing a post-cooling device, which is instead provided between the compressor and the carbon dioxide removal device in the plants of the prior art in order to make efficient the carbon dioxide removal process, because the temperature of the exhaust gas immediately upstream of the only one compressor 42 is already quite low, e.g., about 40-60°C, allowing the most proper working conditions for the carbon dioxide removal device 50.
  • This configuration without any post-cooling device after the compressor 42, allows also achieving an energy saving since the temperature increase given by the compression effect (typically bringing the temperature to 110-130°C) has not to be abated down like in the prior art plants, but the gas can go directly to the heating unit or Process Gas Heater 18 that will have to provide a lower temperature gradient thanks to the higher temperature of the inlet gas. This aspect turns directly into a fuel or electricity saving inside the heating unit 18.
  • the compressor 42 can be reduced in size because the gas flow it must treat is less diluted, having removed upstream its portion of carbon dioxide (typically in the range of 8-12%), leading to a reduction in electricity consumption of up to 10%.
  • the compressor 42 is arranged immediately upstream of the treatment and feeding line 11 , for example immediately upstream the connection between the external source 20 and the treatment and feeding line 11 , or between the external source 20 and the recovery and treatment line 10, or between the external source 20 and the junction connecting said recovery and treatment line 10 to said treatment and feeding line 11 ( Figure 2).
  • An oxygen injection device 30 can be provided downstream of said heating unit 18 to inject oxygen into the process gas flow.
  • the carbon dioxide removal device 50 is of the capture type with amine solvents to remove hydrogen sulfide, in addition to carbon dioxide.
  • the carbon dioxide removal device 50 which involves the capture of carbon dioxide by means of chemical absorption with amine-based solvents, can comprise in succession at least one absorption column, a recovery heat exchanger, and a regeneration column.
  • a reboiler and a gas-liquid separator can cooperate with said regeneration column.
  • a washing column 8 Downstream of the carbon dioxide removal device 50, in particular downstream of the absorption column, a washing column 8 can be provided, in which the gas from which carbon dioxide was removed is washed, preferably by contact with demineralized water, in order to remove and recycle any leakage of amine solution back into the system.
  • the washing column 8 is arranged between said carbon dioxide removal device 50 and said only one compressor 42.
  • a further advantage of the washing column 8 is that there is no chloride deposition in the compressor 42, avoiding phenomena such as stress corrosion cracking which instead remains a problem in the configuration of the prior art.
  • the carbon dioxide removal device 50 is of the pressure-cycle adsorption type on zeolite beds (PSA or VPSA Systems).
  • the recovery and treatment line 10 comprises, downstream of reactor 1 , at least one heat exchange device 3, preferably only one heat exchange device 3, so that the heat is transferred from the exhaust gas to a heat transfer fluid.
  • the at least one heat exchange device 3 is proximal to the reactor 1 , such as immediately downstream of the reactor.
  • a pipe 75 capable of transporting the heat transfer fluid exiting from said at least one heat exchange device, can advantageously connect the heat exchange device 3 to the carbon dioxide removal device 50, in order to provide energy for carbon dioxide absorption by means of amine solution, and/or connect the heat exchange device 3 to the feeding line 11 whereby the heat and composition of the heat transfer fluid (typically steam) can be transferred directly to the process gas, increasing the efficiency of the plant by virtue of the increased temperature of the process gas which is directed towards the heating unit 18, thereby decreasing the energy consumption, and providing the most preferred humidity content to the stream inside feeding line 11 for the correct operation of reactor 1 .
  • the heat transfer fluid typically steam
  • pipe 75 connects the at least one heat exchange device 3 to the treatment and feeding line 11 in a zone preceding the heating unit 18, considering the flow direction of the process gas, so that the heat and mass transfer fluid is added directly to the process gas flow in the treatment and feeding line 11 .
  • pipe 75 connects the at least one heat exchange device 3 to the treatment and feeding line 11 in a zone between the only one compressor 42 and the heating unit 18.
  • a direct connection between the pipe 75 and the treatment and feeding line 11 possibly, but not necessarily, by means injection nozzles or lances.
  • the heat transfer fluid in the pipe 75 is dry steam. Therefore, when pipe 75 connects the first heat exchange device 3 to the carbon dioxide removal device 50, this steam is the energy carrier for the absorption by means of amine solution.
  • the process gas obtained by mixing the make-up gas with the exhaust gas treated in the recovery and treatment line 10, can be humidified by adding said dry vapor directly to the process gas flow, thus eliminating the need to provide a special humidifier along the treatment and feeding line 11.
  • This humidification operation makes it possible to adjust the water content of the process gas in case of high content of heavy gaseous hydrocarbons in said process gas.
  • the heating unit 18 is arranged downstream of the connection between the pipe 75 and said treatment and feeding line 11 .
  • a pipe 34 advantageously connects a stretch of the recovery and treatment line 10, comprised between the carbon dioxide removal device 50 and the compressor 42, to burners of the heating unit 18, in order to send part of the exhaust gas free of carbon dioxide and hydrogen sulfide as fuel gas for said burners.
  • An adjusting device e.g., a pressure control valve, is preferably provided along the pipe 34.
  • tail gas already free of carbon dioxide and hydrogen sulfide
  • the heating unit 18 is supplied by the combustion in part of a fuel coming directly from the external source 20 and in part of said exhaust gas, free of carbon dioxide and hydrogen sulfide, coming from the pipe 34.
  • the technical features of the first variant and the second variant can be combined together into a third variant of the plant of the invention.
  • At least one knockout drum 7 can be provided in the recovery and treatment line 10, upstream of the carbon dioxide removal device 50, to remove liquid particles from the exhaust gas which can contaminate the solution circulating in the device 50.
  • the knockout drum allows liquid particles to be removed from the gas by the use of a vane demister.
  • the gas enters the drum and passes through the vane demister.
  • the sudden changes in direction push the liquid particles against metal sheet walls.
  • the droplets, joining into larger droplets precipitate by gravity to the part below where they are collected and drained.
  • the recovery and treatment line 10 comprises, or consists of, in sequence
  • At least one washing and cooling unit 4 to remove dust from the exhaust gas, obtaining a dedusted gas, i.e. , cleaned from the dust content drawn out from the reactor;
  • a cooling unit 6 e.g., a hairpin cooler or a non-contact exchanger or a water/gas direct contact cooling column, to cool the dedusted gas;
  • a further advantage is that downstream of the carbon dioxide removal device 50 the gas from which the carbon dioxide has been removed is preferably washed with demineralized water in the washing column 8, whereby when the gas flow is then compressed by means of the compressor 42 and the temperature takes the water to evaporation there is no chloride deposition in the compressor, avoiding phenomena such as stress corrosion cracking which instead remains a problem in the configuration of the prior art, where the compressor 42 is located upstream of the removal device 50 and downstream of the cooling unit 6 that, also having to cool the gas, inevitably makes use of large quantities of industrial water.
  • a further advantage is that arranging the carbon dioxide removal device 50 upstream of the single compressor 42 and downstream of the cooling unit 6 makes it possible to eliminate the post-cooler 43, which is present in the configuration of the prior art ( Figure 1) and whose purpose is solely to cool the gas in order to make the performance of the absorption column more efficient.
  • the two main columns i.e., the absorption column (Absorber), which removes carbon dioxide from the gas, and the regeneration column (Stripper), which removes carbon dioxide from the amine solution, operate at two distinct pressures.
  • the regeneration column works at the lowest possible pressure, generally 0.3- 0.5barg, and the absorption column works at the pressure of the direct reduction process, which is about 6barg if the carbon dioxide removal device 50 is arranged upstream of the compressor 42, or 10barg if arranged downstream of the compressor 42.
  • An amine solution absorption column is also provided with a demineralized water make-up pump adapted to inject said demineralized water into the washing column downstream of the absorption column to restore losses, which occur during plant operation.
  • the make-up pump will also benefit from a lower head because the carbon dioxide removal device 50 is arranged upstream of the compressor 42.
  • the external source 20 is connected to said treatment and feeding line 11 or to said recovery and treatment line 10.
  • the external source 20 is connected to a stretch of the circuit between the compressor 42 of the recovery and treatment line 10 and the heating unit 18 of the treatment and feeding line 11 , preferably between the compressor 42 and the connection of the pipe 75 to the treatment and feeding line 11.
  • the first choice in reducing gas for the external source 20 is Natural Gas.
  • the external source 20 can provide a stream, containing hydrogen and carbon monoxide, generated in an external unit (Reformed Gas or Synthetic Gas) by hydrocarbon reaction.
  • an external unit Reformed Gas or Synthetic Gas
  • the external source 20 of make-up reducing gas can be a commercially pure gaseous hydrogen source (at least 99% by volume) or a gas source with a gaseous hydrogen content of at least 65% by volume, preferably from 70 to 98% by volume.
  • the rest of the composition can comprise carbon monoxide, water, carbon dioxide, methane, and nitrogen.
  • a make-up gas composition containing gaseous hydrogen can be as follows in volume percentage: gaseous hydrogen in the range of 92-96%; carbon monoxide in the range of 1 .5-2.5%; water 0.2-0.6%; carbon dioxide 0.0-0.4%; methane 0.3-0.9%; nitrogen 2.0-4.0%.
  • the external source 20 of make-up reducing gas is a source of a gas containing gaseous hydrocarbons with a gaseous hydrocarbon content of at least 25% by volume, such as coke oven gas, Corex Gas, hydrogenated gases released from other industrial activities, and so on.
  • a gas injection device adapted to inject gas containing gaseous hydrocarbons, such as natural gas or coke oven gas, into a lower area of the reactor 1 arranged below the reduction area 2, or directly into a transition zone of the reactor 1 between the reduction area 2 and a reactor discharge area, can also be provided.
  • This process comprises the following steps at full capacity: a) recovering and treating the exhaust gas coming out of reactor 1 by means of the recovery and treatment line 10; b) feeding process gas into a reduction area 2 of the reactor 1 by means of the treatment and feeding line 11 , said process gas being obtained by mixing the make-up gas, coming from the external source 20, with the exhaust gas treated in the recovery and treatment line 10; wherein, before the exhaust gas is introduced into the treatment and feeding line 11 , there are provided in succession a removal of carbon dioxide from said exhaust gas, by means of the carbon dioxide removal device 50, and a compression of the exhaust gas free of carbon dioxide, by means of the only one compressor 42 of the recovery and treatment line 10, towards said treatment and feeding line 11 .
  • the removal of carbon dioxide from the exhaust gas is carried out by means of capture with amine solvents to remove, e.g., by chemical absorption, both carbon dioxide and hydrogen sulfide.
  • heat is transferred from the exhaust gas coming out of the reactor 1 to a heat transfer fluid, by means of the at least one first heat exchange device 3 provided in the recovery and treatment line 10 downstream of the reactor 1 .
  • the heated heat transfer fluid is transferred at least partially, by means of the pipe 75, from said at least one first heat exchange device 3 to the treatment and feeding line 11 , and possibly from said at least one first heat exchange device 3 to the carbon dioxide removal device 50, with the purpose of providing energy for carbon dioxide absorption by amine solution. More in detail, the heated heat transfer fluid is transferred in a zone of the treatment and feeding line 11 preceding the heating unit 18, preferably between the only one compressor 42 and the heating unit 18, by means of a direct addition of said heat transfer fluid to the process gas flow.
  • said heated heat transfer fluid is dry steam which is added directly to the process gas flow in the treatment and feeding line 11 to humidify said process gas without the need for a dedicated vessel for this purpose as in the configuration of the prior art.
  • part of the exhaust gas free of carbon dioxide is sent as fuel gas to the burners of the heating unit 18 by means of the pipe 34 which connects the stretch of the recovery and treatment line 10, comprised between the carbon dioxide removal device 50 and the compressor 42, to said burners.
  • first process variant and second process variant can be combined into a third process variant.
  • the exhaust gas free of carbon dioxide can be washed, preferably by contact with demineralized water, by means of the washing column 8, possibly arranged between the carbon dioxide removal device 50 and the only one compressor 42, in order to remove and recycle any leakage of amine solution.
  • the elimination of liquid particles from the exhaust gas is provided by means of at least one knockout drum 7, e.g., a single knockout drum 7, immediately upstream of the carbon dioxide removal device 50.
  • the amount of gas leaving said at least one knockout drum 7 is greater than the amount of gas entering the compressor 42, which is, therefore, less charged with respect to the configuration of the prior art.
  • the catalytic reforming of the process gas can be carried out in situ inside the reactor 1 , so that the process gas undergoes no additional catalytic reaction beyond the catalytic reactions which take place in the reactor 1 , or inside an external reductant generation unit, i.e. an external catalytic reforming unit.

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Abstract

L'invention concerne une installation de réduction directe pour une réduction directe d'oxydes de fer comprenant un circuit de circulation de gaz comprenant : - un réacteur (1) ayant une zone de réduction (2) conçue pour être chargée avec lesdits oxydes de fer ; - une source externe (20) de gaz d'appoint ; - une conduite de récupération et de traitement (10), agencée en aval du réacteur (1), pour récupérer et traiter le gaz d'échappement qui sort du réacteur (1) ; - une conduite de traitement et d'alimentation (11), agencée en amont du réacteur (1), pour traiter un gaz de traitement, obtenue par mélange du gaz d'appoint avec le gaz d'échappement traité dans la conduite de récupération et de traitement (10), et pour alimenter la zone de réduction (2) du réacteur (1) avec ledit gaz de traitement ; la conduite de récupération et de traitement (10) communiquant en aval avec ladite conduite de traitement et d'alimentation (11) ; dans son tronçon d'extrémité, à proximité de ladite conduite de traitement et d'alimentation (11), la conduite de récupération et de traitement (10) comprenant un dispositif d'élimination de dioxyde de carbone (50) pour éliminer le dioxyde de carbone du gaz d'échappement, agencé en amont d'un compresseur (42) pour comprimer le gaz d'échappement vers ladite conduite de traitement et d'alimentation (11).
PCT/EP2024/085076 2023-12-06 2024-12-06 Installation de réduction directe et procédé associé Pending WO2025120157A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT102023000026085A IT202300026085A1 (it) 2023-12-06 2023-12-06 Impianto di riduzione diretta e relativo processo
IT102023000026085 2023-12-06

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WO2025120157A1 true WO2025120157A1 (fr) 2025-06-12

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8940076B2 (en) 2009-07-31 2015-01-27 Hyl Technologies, S.A. De C.V. Method for producing direct reduced iron with limited CO2 emissions
US20220372587A1 (en) * 2021-05-24 2022-11-24 Nucor Corporation Direct reduced iron system and method using synthetic combustion air
US20230243004A1 (en) * 2020-06-26 2023-08-03 Danieli & C. Officine Meccaniche S.P.A. A direct reduction system and relative process

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8940076B2 (en) 2009-07-31 2015-01-27 Hyl Technologies, S.A. De C.V. Method for producing direct reduced iron with limited CO2 emissions
US20230243004A1 (en) * 2020-06-26 2023-08-03 Danieli & C. Officine Meccaniche S.P.A. A direct reduction system and relative process
US20220372587A1 (en) * 2021-05-24 2022-11-24 Nucor Corporation Direct reduced iron system and method using synthetic combustion air

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