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
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B13/00—Making spongy iron or liquid steel, by direct processes
  • C21B13/0033—In fluidised bed furnaces or apparatus containing a dispersion of the material
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B13/00—Making spongy iron or liquid steel, by direct processes
  • C21B13/14—Multi-stage processes processes carried out in different vessels or furnaces
  • C21B13/143—Injection of partially reduced ore into a molten bath
• • 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
  • C21B2100/80—Interaction of exhaust gases produced during the manufacture of iron or steel with other processes

Definitions

• the invention relates to a method for operating a direct reduction reactor in an integrated steelworks, comprising at least one direct reduction reactor for directly reducing ferrous oxides to directly reduced ferrous materials and generating reactor gas, and at least one EAF for at least partially melting directly reduced ferrous materials to crude steel and generating EAF gas, wherein at least a portion of the reactor gas discharged from the direct reduction reactor is recirculated, heated in at least one reduction gas heater or in at least one reformer, and returned to the direct reduction reactor as reduction gas.
• the EP 0 258 208 B1 reveals an approach in which the directly reduced iron carrier is fed to a converter and any excess thereof can be fed to an electric arc furnace.
• the object of the present invention is to further develop a generic process in such a way that the energetically and materially valuable process gases present in an existing integrated steelworks can be used in an economically optimized manner.
• directly reduced iron carriers and a reactor gas are produced from oxide iron carriers, such as iron ore, by means of a reducing gas which may contain hydrogen or proportions of carbon monoxide and hydrogen and/or methane, and optionally aliphatic compounds such as methanol/ethanol.
• the reactor gas may contain unreacted components of carbon monoxide and/or Contains hydrogen and/or methane, and may also contain amounts of carbon dioxide and/or water vapor.
• the directly reduced iron carriers are at least partially melted into crude steel in the at least one EAF (Electric Iron Filling Facility), and an EAF gas is produced as a byproduct, which may contain reactive components such as hydrogen and/or carbon monoxide.
• EAF Electronic Iron Filling Facility
• Other iron-containing materials such as steel scrap, can also be added to the EAF in concentrations of up to 50%, particularly up to 40%, 30%, preferably up to 20%, or 10% of the crude steel to be produced, especially to limit any interfering elements/impurities potentially present in the scrap.
• Crude steel can also be produced without scrap.
• the crude steel to be produced in the EAF can be melted with at least 50%, preferably at least 75%, or preferably up to 100% directly reduced iron carriers.
• Carbon carriers can also be added as needed, particularly in quantities required to achieve a specific carbon content in the crude steel, especially to produce a foamed slag.
• the EAF Electro Arc Furnace
• the EAF is preferably an electric melting furnace with direct arc action, which forms arcs between the electrode and the charge/liquid phase.
• EAFac alternating current electric arc melting furnace
• EAFdc direct current electric arc melting furnace
• LF ladle furnace
• the EAF is typically operated under oxidation conditions.
• At least some of the discharged EAF gas can be added to the reducing gas before it enters the reducing gas heater or the reformer.
• at least some of the discharged EAF gas can be added to the reducing gas after it leaves the reducing gas heater or the reformer.
• at least some of the discharged EAF gas can be fed directly into the direct reduction reactor, so that mixing with the reducing gas only occurs within the direct reduction reactor.
• the exhausted EAF gas contains hydrogen and/or carbon monoxide, which are ideally suited for direct reduction. This allows for the use of fresh gas, i.e., the external supply of methane (natural gas) and/or hydrogen.
• fresh gas i.e., the external supply of methane (natural gas) and/or hydrogen.
• either the proportion of carbon monoxide predominates meaning that at least 25 vol%, in particular at least 30 vol%, preferably at least 35 vol%, more preferably at least 40 vol%, particularly preferably at least 45 vol%, and more preferably at least 55 vol% of carbon monoxide is present
• the proportion of hydrogen predominates meaning that at least 20 vol%, in particular at least 25 vol%, preferably at least 30 vol%, and more preferably at least 35 vol% can be present.
• the hydrogen content can be further adjusted, for example, by introducing steam.
• the EAF gas discharged from the EAF can be dehumidified before being added to the reducing gas prior to entering the reducing gas heater or the reformer.
• the discharged EAF gas is passed through a unit, such as a condenser, and cooled accordingly, causing the water vapor in the EAF gas to condense and thus be separated from it.
• a unit such as a condenser
• the EAF gas is effectively dehumidified. This improves the quality of the EAF gas.
• Another embodiment can provide that the CO2 content contained in the dehumidified EAF gas is separated and subsequently added to the reduction gas (dehumidified and optionally freed of carbon dioxide) as essentially carbon dioxide-free EAF gas before it enters the reduction gas heater or the reformer.
• the dehumidified EAF gas is passed through a unit in which compounds or mixtures of carbon and oxygen, such as carbon dioxide ( CO2 ), are removed.
• CO2 separation in the form of amine scrubbing, carbonate scrubbing, membrane separation technology, such as selective membranes, or PSA (Pressure Swing Absorption).
• the EAF gas which is added to the reduction gas after leaving the reduction gas heater or reformer and/or is introduced directly into the direct reduction reactor, has a temperature of at least 700 °C.
• the EAF gas can be added to or mixed with the reducing gas after it leaves the reducing gas heater or reformer, which can have a temperature between 700 and 1100 °C.
• the reducing gas can be additionally "boosted.”
• the EAF gas can have a temperature of, in particular, at least 800 °C, preferably at least 900 °C, preferably at least 1000 °C, and most preferably at least 1100 °C.
• the temperature can be a maximum of 2000 °C, in particular a maximum of 1800 °C, and preferably a maximum of 1600 °C.
• the temperature of the EAF gas can also be further increased by suitable means, in particular by electrically driven means, for example, by at least 30 K.
• the direct reduction reactor can be divided into two or three sections: a pre-reduction section, a final reduction section, and optionally a carburizing section.
• the iron oxides pass through these sections in the aforementioned order, while the reducing gas, introduced into the final reduction section, flows in the opposite direction.
• the direct reduction reactor is preferably a shaft furnace
• the pre-reduction section is located in the upper part of the furnace, where the iron oxides are introduced and pre-reduced. They then pass (by gravity) into the final reduction section, located in the middle part of the furnace, where the iron oxides are essentially fully reduced. Finally, they pass (by gravity) into the carburizing section in the lower part of the furnace, where a carbon-containing gas is typically introduced to carburize the directly reduced iron oxides.
• gas exchange between the carburizing area and the final reduction area is generally avoided in the lower section.
• EAF gas at a temperature of at least 700 °C can be introduced directly into the pre-reduction section of the direct reduction reactor.
• the EAF gas can be introduced directly into the final reduction section of the direct reduction reactor at a temperature of at least 700 °C. This allows, in particular, a high metallization of the directly reduced iron carriers to be achieved and preferably reduces the input of primary energy (fossil, biogenic, or green/renewable hydrogen) into the system.
• the EAF gas at a temperature of at least 700 °C, can be introduced directly into the carburizing section of the direct reduction reactor. Due to the high temperature, there is a high reactivity with the directly reduced iron supports, and carbon from, for example, the carbon monoxide content of the EAF gas can form on the iron supports in the form of Fe3C , or carbon can be deposited on and within the directly reduced iron supports.
• gas transfer from the carburizing section to the final reduction section, and thus mixing with the reducing gas supplied to the final reduction section, can be permitted.
• the reactor gas discharged from the direct reduction reactor contains unreacted components, in particular compounds or mixtures of carbon and oxygen (CO, CO 2 ), methane (CH 4 ), hydrogen (H 2 ) and/or water vapor (H 2 O), as well as process-related unavoidable impurities.
• unreacted components in particular compounds or mixtures of carbon and oxygen (CO, CO 2 ), methane (CH 4 ), hydrogen (H 2 ) and/or water vapor (H 2 O), as well as process-related unavoidable impurities.
• the reactor gas discharged from the direct reduction reactor is dehumidified.
• the discharged reactor gas is passed through a unit, for example a condenser, and cooled accordingly, so that the water vapor contained in the reactor gas condenses and is thus separated from the reactor gas.
• a unit for example a condenser
• the condensate "dehumidifies" the reactor gas. This can improve the quality of the reactor gas.
• CO2 carbon dioxide
• CO2 carbon dioxide
• This separation can be achieved, for example, through CO2 separation using amine scrubbing, carbonate scrubbing, membrane separation technology (such as selective membranes), or pressure swing absorption (PSA).
• PSA pressure swing absorption
• the carbon dioxide separated from the dehumidified reactor gas can be stored in a suitable environment, used in carbon capture and storage (CCS), or utilized in a carbon capture and utilization (CCU) process.
• carbon dioxide can also be used as a potential recarburization gas or component of a potential recarburization gas in the recarburization section of the direct reduction reactor.
• a direct reduction plant based on the well-known Midrex process which includes at least one reformer instead of a reduction gas heater, in which conventional natural gas is converted as fresh gas to a reduction gas comprising carbon monoxide and hydrogen
• the carbon dioxide could be converted with natural gas in at least one reformer to carbon monoxide and hydrogen in order to be added back to the direct reduction reactor as a reduction gas. Since the reactor gas is also heated in the reformer, it can also be advantageous to introduce the EAF gas containing CO and/or H2 into the reformer.
• the reducing gas introduced into the direct reduction reactor for the direct reduction of the oxide iron carriers to directly reduced iron carriers is heated to a temperature between 700 and 1100 °C in at least one reducing gas heater or in the reformer before being fed into the final reduction section of the direct reduction reactor.
• a portion of the dehumidified reactor gas can be used as fuel gas or as an additive gas to a fuel gas, thus at least as a component of the fuel gas, to fire the reducing gas heater or the reformer.
• up to 20%, in particular up to 16%, preferably up to 13%, preferably up to 10%, of the dehumidified reactor gas can be used, at least in part, as fuel gas. This allows, for example, process-related impurities in the quasi-closed system to be kept to a minimum, and an undesirable increase in impurities in the system can be counteracted by partially diverting the gas as fuel gas.
• the portion of the reactor gas that is at least partially removed as fuel gas through dehumidification, optional carbon dioxide removal, and optional partial diversion must be replaced by the EAF gas, and if this cannot be sufficiently supplied, by additional fresh gas.
• the fresh gas can be methane, for example natural gas or biomethane, etc., or hydrogen or a mixture thereof.
• fresh gas can be supplied variably depending on the availability of EAF gas. Since the EAF cannot be operated continuously, EAF gas would only be available temporarily. Therefore, depending on the design and operating mode of a direct reduction plant, fresh gas can be supplied if, for example, excess EAF gas cannot be stored (intermediately) to ensure essentially continuous operation of the direct reduction reactor.
• the operating mode can also be adapted to the availability of EAF gas so that as little fresh gas as possible needs to be supplied.
• FIG. 1 An example of a method according to the invention is shown in a schematic representation of an integrated steelworks for operating a direct reduction reactor.
• the integrated steelworks (1) includes at least one direct reduction reactor (2) for the direct reduction of oxide iron carriers (io) to directly reduced iron carriers (ri) and at least one EAF (3) for at least partially melting down directly reduced iron carriers to crude steel and generating an EAF gas (EG).
• a direct reduction reactor (2) for the direct reduction of oxide iron carriers (io) to directly reduced iron carriers (ri)
• EAF (3) for at least partially melting down directly reduced iron carriers to crude steel and generating an EAF gas (EG).
• Oxide iron carriers (io) are introduced into a direct reduction reactor (2), which can be designed, for example, as a shaft furnace and is thus appropriately loaded at the top.
• a direct reduction reactor (2) At the bottom of the direct reduction reactor (2), the directly reduced iron carriers (ri) are removed and fed into an EAF (3) for at least partial remelting of the directly reduced iron carriers (ri), particularly with the addition of further additives, such as steel scrap and/or carbon carriers.
• an EAF gas (EG) is generated in the EAF (3), which preferably contains carbon monoxide and/or hydrogen.
• the method for operating an EAF (3) with an oxidizing as well as, for example, a reducing atmosphere is known to those skilled in the art.
• carbon monoxide can be produced by the addition of carbon and oxygen (especially for the formation of the foamy slag).
• hydrogen can be produced from volatile components, particularly from carbon (charcoal addition), from the dissociation of steam at high temperatures, from reactions of water vapor with carbon (charcoal addition), or from water-gas shift reactions.
• the crude steel produced can be fed into secondary metallurgy in the integrated steelworks (1) as quickly as possible, not shown, to process the desired steel and subsequently cast into semi-finished products, such as flat or long products.
• the direct reduction reactor (2) In addition to iron oxide carriers (io), the direct reduction reactor (2) must also be supplied with a reducing gas (RG) to drive the oxygen out of the iron oxide carriers (io).
• This gas can consist of carbon-containing compounds and/or hydrocarbon-containing compounds and/or hydrogen or mixtures thereof and flows through the direct reduction reactor (2) in a countercurrent flow, particularly from bottom to top.
• the reducing gas (RG) Before being supplied, the reducing gas (RG) is heated to the required operating temperature, for example between 700 and 1100 °C, in a reducing gas heater (5).
• the reducing gas can also be generated and heated in a reformer before being supplied.
• the extracted reactor gas (TG) is dehumidified by passing it, for example, through a condenser and cooling it accordingly, so that the water vapor (H 2 O) contained in the reactor gas (TG) condenses and can thus be separated from the reactor gas (TG).
• a portion of the dehumidified reactor gas (TG) can be used, at least in part, as fuel gas (BG) to fire at least one reducing gas heater (5) or at least one reformer.
• the fuel gas (BG) diverted from the dehumidified reactor gas (TG) can be supplemented with another fuel gas if required.
• Air and/or oxygen ( O2 ) serves as the oxidizer for the combustion process in the reducing gas heater (5) or in the reformer. If additional heat is required to achieve the operating temperature of the reducing gas (RG), it can also be supplied electrically, if necessary (not shown here).
• the reactor gas (TG) circulated in the cycle (I) can be further freed from carbon dioxide (CO2) after dehumidification by passing the dehumidified reactor gas (TG) through a suitable CO2 separation system.
• CO2 carbon dioxide
• Unused reducing gas, along with any gaseous reaction products, is discharged from the direct reduction reactor (2) as reactor gas (TG).
• the discharged reactor gas (TG) may contain hydrogen ( H2 ), a compound or mixture of carbon and oxygen (CO, CO2 ), and/or at least one hydrogen-containing compound ( H2O ), as well as unavoidable impurities.
• the discharged reactor gas (TG) is recirculated (I) back into the direct reduction reactor (2), with fresh gas (FG) being added not only to improve the reduction potential but also to compensate for the amount removed by dehumidification, optional partial diversion of fuel gas (BG), and optional carbon dioxide capture.
• the EAF gas (EG) discharged from the EAF (3) is added to the reducing gas (RG) before it enters the reducing gas heater (5) and then the reformer, the EAF gas (EG) can be dehumidified, for example, by passing it through a condenser and cooling it accordingly, so that the water vapor ( H2O ) contained in the EAF gas (EG) condenses and can thus be separated from the EAF gas (EG).
• the dehumidified EAF gas (EG) can then be freed of carbon dioxide.
• EAF gas (EG) discharged from the EAF (3) can be added to the reduction gas (RG) after leaving the reduction gas heater (5) or the reformer.
• at least some of the EAF gas (EG) discharged from the EAF (3) can be introduced directly into the direct reduction reactor (2).
• the EAF gas (EG) that is added to the reduction gas (RG) after leaving the reduction gas heater (5) or the reformer and/or introduced directly into the direct reduction reactor (2) has a temperature of at least 700 °C.
• EAF gas EAF gas
• Fresh gas (FG) can therefore be supplied variably as needed, depending on the availability of EAF gas (EG).

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
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• Organic Chemistry (AREA)
• Dispersion Chemistry (AREA)
• Hydrogen, Water And Hydrids (AREA)

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Citations (8)

• 2024
  • 2024-07-26 EP EP24191131.2A patent/EP4685246A1/fr active Pending

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