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WO2025202431A1 - Procédé de production d'une masse fondue de fer métallique - Google Patents

Procédé de production d'une masse fondue de fer métallique

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Publication number
WO2025202431A1
WO2025202431A1 PCT/EP2025/058513 EP2025058513W WO2025202431A1 WO 2025202431 A1 WO2025202431 A1 WO 2025202431A1 EP 2025058513 W EP2025058513 W EP 2025058513W WO 2025202431 A1 WO2025202431 A1 WO 2025202431A1
Authority
WO
WIPO (PCT)
Prior art keywords
iron
furnace
melt
slag
bearing material
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/EP2025/058513
Other languages
English (en)
Inventor
Pande Nishant Prasad
Jenny WIKSTRÖM
Shabbir Taherbhai LAKDAWALA
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.)
Luossavaara Kiirunavaara AB LKAB
Original Assignee
Luossavaara Kiirunavaara AB LKAB
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 Luossavaara Kiirunavaara AB LKAB filed Critical Luossavaara Kiirunavaara AB LKAB
Publication of WO2025202431A1 publication Critical patent/WO2025202431A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

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
    • C21B13/14—Multi-stage processes processes carried out in different vessels or furnaces
    • 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
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/52—Manufacture of steel in electric furnaces
    • C21C5/5241—Manufacture of steel in electric furnaces in an inductively heated furnace
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/56—Manufacture of steel by other methods
    • C21C5/562—Manufacture of steel by other methods starting from scrap

Definitions

  • the present invention relates to a method for producing metallic iron melt.
  • Direct reduced iron (DRI)-based processes are gaining popularity for reduction of iron ore.
  • the temperature inside a DR shaft is generally below 1000 °C, leaving gangue-oxides inside the iron ore unreduced.
  • the produced DRI essentially comprises metallic iron and some iron oxide, FeO, with some entrapments of unreduced gangue-oxides.
  • the DRI Unlike molten hot metal produced by blast furnace, the DRI remains in solid form and requires subsequent melting. A subsequent stage of melting and refining can be performed in e.g. an electric arc furnace (EAF).
  • EAF electric arc furnace
  • a typical EAF has relatively inferior refining capabilities compared to a traditional basic oxygen furnace (BOF).
  • W02023204063A1 and W02023204069A1 show a direct reduction step in which iron ore is brought into contact with a reducing agent under heating to obtain DRI. Thereafter the DRI is melted in an induction-melting furnace to obtain molten iron and to remove gangue contained in the DRI. The slag produced is discharged to the outside of the melting furnace.
  • the melting step may include blowing oxygen gas into the molten iron during a portion or all of the melting step, and addition of a slag composition modifier. This is done to completely melt the slag with high fluidity for a smooth melting operation.
  • Such a method may increase the slag volume and the dissolved oxygen content in the Fe-melt, necessitating extensive de-oxidation treatment of the melt at a secondary metallurgy unit.
  • the metallization degree represents the extent to which iron bearing material (usually in the form of direct reduced iron or DRI) has been converted into metallic iron. It represents the proportion of metallic iron (Fe) in the total iron content of the material and indicates how much of the iron has been reduced from its original oxide form to metallic iron.
  • the metallization degree is at least 95 %, i.e. 95 % of the iron exists as metallic iron, while the remaining 5% is still in the oxide form.
  • the metallization degree is at least 97%.
  • DRI produced through existing routes using natural gas or a mixture of natural gas and hydrogen typically contains carbon within the range of 1-4 wt.%, making such a DRI unsuitable for the proposed process.
  • carbon-free iron-bearing material may still contain trace amounts of carbon as a contaminant, but in very low concentrations (e.g., ppm-levels), due to various intermediate handling and transportation stages.
  • a low carbon content is crucial for ensuring the quality of the Fe-melt. Higher carbon content negatively affects Fe-melt quality, thereby compromising the effectiveness of the proposed process.
  • the iron bearing material may also comprise smaller amounts of one or more additional elements such as Si, V, Cr, Ti, Mn, P, S, and/or Al in the gangue, mainly as oxide mineral forms. Such materials are then provided in the produced slag phase and may be extracted therefrom.
  • the gangue content of the iron bearing material should be at most 5 wt.%.
  • the gangue oxides form a slag melt or crust, encapsulating unreduced FeO-content present in the iron bearing material.
  • the metallic iron melt phase may comprise at least 99 wt.% or at least 99.9 wt.% iron. Such a metallic iron melt phase can be used to make clean or even ultra-clean steel grades (after minor adjustments in a secondary metallurgy unit (for e.g. in a Ladle Furnace)).
  • the temperature range of 1600-1700°C is based on considerations regarding the balance between achieving complete melting of the iron melt while preventing complete melting of the slag phase comprising the gangue oxides.
  • This semi-solid or heterogeneous state of the slag is essential for maintaining the integrity of the iron melt and preventing the undesirable partitioning of gangue elements between the metal and the slag.
  • An iron bearing material having a metallization degree of at least 95% and at most 5 wt.% gangue content is important for ensuring the effectiveness of the above-described method. These limits are set based on several key aspects of the process:
  • Performing the same method as described above but without a controlled atmosphere in the furnace and using an iron bearing material that has a lower metallization degree, and/or a higher carbon content and/or a higher gangue content, i.e. a low-grade iron bearing material, may result in increased slag volume production, a higher degree of oxygen dissolution in the metallic iron melt, and, hence, a less clean metallic iron melt.
  • P phosphorus
  • the extent of phosphorus reversion is determined by the thermodynamic equilibrium conditions between the slag and metal. The equilibrium is established when both the slag and metal are at the same temperature and fully molten. Under these conditions, phosphorus can readily transfer from the slag into the melt, increasing its concentration in the final steel.
  • the described method mitigates the issue by ensuring that the slag remains semi-molten and heterogeneous through extensive heat dissipation from the melt's top surface. This disrupts the thermodynamic equilibrium between the metal and slag, preventing phosphorus from migrating into the iron melt. Consequently, phosphorus levels in the iron melt produced with this method are low (around 55 ppm) compared to methods where the slag phase is fully molten. Fully molten slag requires additional phosphorus control measures, primarily through modifications in slag chemistry.
  • any such oxygen-blowing treatment (which is typical in primary steelmaking stage in an electric arc furnace (EAF)/ basic oxygen furnace (BOF)) is not necessary.
  • EAF electric arc furnace
  • BOF basic oxygen furnace
  • the addition of reagents or slag modifiers during melting may be limited, considering that the slag need not be completely molten. This would facilitate the production of a slag phase enriched in gangue oxides, containing valuable components such as vanadium, titanium, and chromium oxides.
  • the above-described method minimizes entry of tramp elements from gangue oxides into the molten metallic melt.
  • Melting duration can vary depending on furnace specifications, including power and efficiency, as well as design factors influencing heat losses. In one example, it is at least 1 hour.
  • the provided iron bearing material may have a metallization degree of at least 96 %, at least 97 %, at least 98 %, or at least 99 %.
  • the provided iron bearing material may have a carbon content of at most 0.05 wt.%, or at most 0.01 wt.%.
  • the furnace may be heated to a temperature of 1600-1680 °C, or 1620-1650 °C.
  • the provided iron bearing material may have a gangue content of less than 4.5 wt.%, or less than 4 wt.%, or less than 3.5 wt.%, or less than 3 wt.%, or less than 2.5 wt.%, or less than 2 wt.%, or less than 1.5 wt.%, or less than 1 wt.%, or less than 0.5 wt.%.
  • the controlled atmosphere in the furnace may be a reducing atmosphere.
  • a (slightly) reducing atmosphere prevents re-oxidation of the Fe-melt with oxygen in atmospheric air.
  • gases used in slightly reducing atmospheres include gas mixtures such as H2-H2O, CO-CO2.
  • the reducing atmosphere is highly dependent on thermodynamic factors such as temperature and pressure conditions in the furnace.
  • the controlled atmosphere in the furnace may have an absolute pressure of 100 Pa to atmospheric pressure.
  • the controlled atmosphere in the furnace may be a low vacuum, i.e. 3 kPa to 100 kPa, or a medium vacuum of 100 Pa-3 kPa.
  • the controlled atmosphere in the furnace is an atmospheric pressure (101.3 kPa).
  • the controlled atmosphere in the furnace may be an inert atmosphere.
  • the inert atmosphere may comprise argon, nitrogen or carbon dioxide.
  • the method described above may not comprise addition of oxygen gas or slag modifiers into the furnace.
  • the method may further comprise recovering transition elements from the formed slag phase.
  • Such a step could give value-added transition element oxides enriched in the slag phase.
  • the valuable transition element oxides such as V2O5, TiCh, and C ⁇ Ch.
  • the method may comprise a step of providing the iron bearing material using a gas mixture comprising 90-100 vol.% hydrogen, 0-10 vol.% nitrogen, 0-10 vol.% H2O through a Direct Reduction (DR) process.
  • a gas mixture comprising 90-100 vol.% hydrogen, 0-10 vol.% nitrogen, 0-10 vol.% H2O through a Direct Reduction (DR) process.
  • DR Direct Reduction
  • the balance of the gas constituents may be ⁇ 0.1 vol.%. These could be minor concentrations of gaseous species bearing element combinations such as H-O, N-O, N-H, H-N-O, etc.
  • the Direct Reduction (DR) process may be performed in a shaft furnace, in a multi hearth furnace, or in a rotary kiln furnace.
  • DRI produced using natural gas typically exhibits metallization levels below 95%.
  • trial results from producing DRI using a gas mixture comprising 90-100 vol.% hydrogen (other components in the gas mixture being 0-10 vol.% nitrogen, 0-10 vol.% H2O, balance ⁇ 0.1 vol%) as the reducing gas demonstrate a remarkable increase in metallization, consistently achieving levels above 99%.
  • the resulting DRI would primarily consist of pure Fe (carbon-free), with minor amounts of FeO and unreduced gangue oxides.
  • the method may further comprise a step of providing the iron bearing material using 100% ammonia gas in a Direct Reduction (DR) process.
  • DR Direct Reduction
  • the iron bearing material may in addition or alternatively comprise steel scrap.
  • the furnace used may be an induction furnace.
  • temperatures of 1600-1700°C can be achieved without any localized over-temperature. This is primarily attributed to the direct induction of eddy currents within the solid feed, leading to swift melting. Unlike conventional EAF and fuel-fired furnaces, the lack of excessively high localized temperatures in the induction furnace coupled with absence of carbon prevents the reduction of gangue oxides present in the DRI. As a result, melting of carbon-free DRI in an induction furnace would produce a relatively pure iron melt during the melting process, as impurities from gangue oxides will not join the metallic melt.
  • the furnace used may be an electrical-resistance furnace.
  • the inert atmosphere typically maintained with argon (Ar) gas, serves two critical functions: it ensures an inert environment for melting and facilitates extensive heat dissipation from the melt's top surface. This is achieved by introducing fresh argon gas directly over the melt surface.
  • Ar argon
  • the method may further comprise to prepare the formed steel melt for refining in a secondary metallurgy unit.
  • Such treatments in the secondary normally comprise degassing, deoxidation and alloying treatments.
  • the metallic iron melt produced with the above-described method is suitable for producing high-quality steel products without the need for extensive refining processes.
  • a requisite level of carbon alloying is necessary.
  • a significant advantage offered by the above-described method is the ability to add carbon to the melt at a stage where further refining may not be necessary. This feature is unprecedented. No prior process has provided such an advantage.
  • the significance lies in the fact that the presence of carbon in the metallic iron melt during the refining in conventional processes continually facilitates reversion of tramp elements from the slag phase back into the melt.
  • Intense oxygen blowing is then carried out to mitigate this impurity element reversion to and remove carbon from the metallic melt.
  • this results in extensive iron reoxidation, an increase in slag volume, and significant consumption of resources.
  • the melt becomes nearly saturated with dissolved oxygen content, leading to complications during subsequent alloying stages. If adequate deoxidation of the melt is not conducted prior to alloying, valuable alloying elements are lost in the LF (Ladle Furnace) slag formed during secondary metallurgy treatment.
  • the above-described method addresses several challenges inherent in conventional steelmaking processes, including the challenge of sufficient refining when starting with a high-carbon iron melt (e.g., hot metal from blast furnace), the challenge of controlling iron losses during refining, and the challenge of controlling alloying element losses to the slag during secondary metallurgy alloying treatment.
  • a high-carbon iron melt e.g., hot metal from blast furnace
  • the iron bearing material is provided in the furnace in a cold state.
  • cold state is here meant at a temperature of 65°C or less.
  • the iron bearing material may be provided in the furnace in a hot state.
  • hot state is here meant at a temperature of 300°C or more.
  • Iron bearing material may be introduced into the furnace in the form of hot DRI, cold DRI, or a combination thereof.
  • a metallic iron melt phase comprising at least 99.9 wt.% iron.
  • the process of molten melt processing during conventional steelmaking can be broadly categorized into three main steps: 1) the conversion of hot metal into crude steel during the primary steelmaking phase, 2) the conversion of crude steel into killed steel through deoxidation treatment in a secondary metallurgy unit, and 3) the conversion of killed steel melt into finished steel melt via alloying treatment in the secondary metallurgy unit.
  • the iron melt produced through this new process will exhibit advantageous and significant differences compared to both crude steel melt and killed steel melt.
  • the melt from the proposed new process will guarantee an iron content exceeding 99.9 wt%, unlike crude steel, which typically contains iron content below 99.9 wt%. Additionally, the iron melt will match or surpass killed steel melt in terms of dissolved oxygen content.
  • Determination of the steel melt composition for its total iron content may be performed using Optical Emission spectroscopy, with measurements conducted on quenched metallic stub samples.
  • the dissolved oxygen content in the melt may be measured using melt probes operating on the principle of activity measurement in a galvanic cell utilizing solid electrolytes.
  • the provided metallic iron melt phase comprising at least 99.9 wt.% iron may have a dissolved oxygen content that is lower than the common levels of around 500 ppm found in crude steel, and around 50 ppm in semi-killed steel melts.
  • Fig. 1 shows a process and set-up of producing metallic iron melt.
  • Fig. 2 shows extent of Fe-loss during melting of carbon-free DRI in an induction furnace based on mass-balance calculations.
  • Fig. 3 shows correlation between slag rate and Fe-content (or grade) of iron ore for the process shown in Fig. 1.
  • the correlation is obtained through mass-balance, considering that the carbon-free DRI produced using this iron ore has a metallization of 99 wt.%.
  • Figs 4a and 4b show characteristics of slag obtained by melting carbon-free DRI produced from iron ore pellets in an induction furnace.
  • the pellets have Fe-total ⁇ 67.7%, and the ratio of CaO/SiO2 ⁇ 1.35. These plots are obtained through mass-balance calculations.
  • Fig. 1 shows a process and set-up of producing metallic iron melt.
  • Iron ore pellets 1 are introduced into a DR (Direct reduction) system 2 and an iron bearing material, (for instance DRI, or direct reduced iron), 4 is produced using e.g. 100% H2 gas 3.
  • Hot DRI 4a e.g. using a Hot Link Bin
  • cold DRI 5b that has been cold down e.g. in a DRI cooler 5
  • the iron bearing material 4a, 5b introduced into the furnace 6 has a metallization degree of at least 95%, a carbon content of at most 0.1 wt.%, and a gangue content of 5wt.% or less.
  • the furnace 6 may for e.g.
  • a DRI process could be performed using a gas mixture comprising 90-100 vol.% hydrogen (other components in the gas mixture being 0-10 vol.% nitrogen, 0-10 vol.% H2O, balance ⁇ 0.1 vol.%), using 100% ammonia gas, or using a mixture of ammonia gas and hydrogen.
  • a laboratory-scale DRI-melting experiment was conducted. Approximately 500 g of carbon- free DRI of metallization >97% produced from iron ore pellets was melted in a Tammann- furnace (electric resistance type laboratory-scale furnace) in an MgO-crucible. The furnace was heated to 1650°C, held at this temperature for 1 h, and subsequently cooled down to room temperature. Simultaneously, a purging flow of argon was maintained above the melting stock within the furnace throughout the course of the experiment. The solidified melt sample was later examined for chemical composition in an Optical Emission Spectrometer meant for analyzing metallic samples.
  • Table 1 below presents a detailed chemical composition of the metallic melt produced from this test.
  • Table 1 Chemical composition of the metallic melt obtained by melting highly metallized DRI (metallization > 97%) from pellets in a laboratory-scale Tammann furnace at 1650PC (compared with typical concentrations in crude steel after basic oxygen furnace (BOF) treatment (reference- R.J. Fruehan, Making, Shaping and Treating of Steel, Steel making and refining volume, AISE Steel Foundation, ed. 1998, United States Steel. Co. (1998)).
  • BOF basic oxygen furnace
  • the iron bearing melt has very low concentrations of all tramp elements - C, Si, V, Cr, Ti, Mn, Mg, P, S, Al and N.
  • oxygen is introduced into the metallic melt to reoxidize impurity/tramp elements, allowing them to separate into a slag phase.
  • This slag usually contains 15-30% FeO and is generated at a rate of approximately 100-150 kg/ton-crude steel across various operational steelmaking routes.
  • the estimated range stands at 20-25 kg Fe-loss per ton of melted Fe.
  • the resulting Fe-loss is significantly lower than that encountered in the conventional routes of steelmaking, provided, the carbon-free DRI is highly metallized (typically exceeding 97.5%).
  • the estimated Fe-loss during induction melting of the DRI amounts to around lOkg/t-melted-Fe if its metallization is 99%.
  • the electrically non-conductive oxides including gangue-oxides and FeO in DRI
  • induction furnace heating lacks chemical energy due to melt oxidation.
  • the slag generation rate is estimated to be below 100 kg/t- melted-Fe, provided that the iron ore's Fe-content exceeds 66%.
  • Fig. 4a demonstrates the relationship of slag rate for the above-describe method, with respect to (w.r.t) the degree of metallization for the carbon-free DRI produced from the pellets.
  • Fig. 4b depicts FeO-content (%) variations in the slag w.r.t DRI-metallization. (In the used pellets, the CaO/SiCh ratio is maintained closely at around 1.35). Additionally,
  • Table 2 lists the detailed slag-compositions with varying metallization of the DRI produced from ironore pellets derived from a high grade iron ore.
  • Table 2 Calculated compositions of slag obtained by melting carbon-free DRI (of different degree of metallization) produced from iron ore pellets in an induction furnace. Slag composition

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)

Abstract

L'invention concerne un procédé de production d'une masse fondue de fer métallique, comprenant les étapes consistant : dans un fourneau, à fournir un matériau ferrifère ayant un degré de métallisation d'au moins 95 % en poids, une teneur en carbone d'au plus 0,1 % en poids, et une teneur en gangue inférieure à 3 4 5 % en poids ou moins, et à chauffer ledit matériau ferrifère dans ledit fourneau à une température comprise entre 1 600 et 17 000 °C dans une atmosphère contrôlée, ce qui permet de former une phase de masse fondue de fer métallique et une phase de laitier.
PCT/EP2025/058513 2024-03-28 2025-03-27 Procédé de production d'une masse fondue de fer métallique Pending WO2025202431A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP24167300.3 2024-03-28
EP24167300.3A EP4624596A1 (fr) 2024-03-28 2024-03-28 Procédé de production de fonte de fer métallique

Publications (1)

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WO2025202431A1 true WO2025202431A1 (fr) 2025-10-02

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Application Number Title Priority Date Filing Date
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EP (1) EP4624596A1 (fr)
WO (1) WO2025202431A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023204069A1 (fr) 2022-04-22 2023-10-26 Ｊｆｅスチール株式会社 Procédé de fusion de fer à réduction directe, fer solide et procédé de production de fer solide, et matériau de génie civil et de construction, et procédé de production de matériau de génie civil et de construction
WO2023204063A1 (fr) 2022-04-22 2023-10-26 Ｊｆｅスチール株式会社 Procédé de fusion de fer à réduction directe, fer solide et procédé de fabrication de fer solide, matériau pour génie civil et construction, procédé de production de matériau pour génie civil et construction, et système de fusion de fer à réduction directe
US20240026476A1 (en) * 2022-07-22 2024-01-25 Hertha Metals, Inc. Method and apparatus for metals, alloys, mattes, or enriched and cleaned slags production from predominantly oxide feeds

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023204069A1 (fr) 2022-04-22 2023-10-26 Ｊｆｅスチール株式会社 Procédé de fusion de fer à réduction directe, fer solide et procédé de production de fer solide, et matériau de génie civil et de construction, et procédé de production de matériau de génie civil et de construction
WO2023204063A1 (fr) 2022-04-22 2023-10-26 Ｊｆｅスチール株式会社 Procédé de fusion de fer à réduction directe, fer solide et procédé de fabrication de fer solide, matériau pour génie civil et construction, procédé de production de matériau pour génie civil et construction, et système de fusion de fer à réduction directe
US20240026476A1 (en) * 2022-07-22 2024-01-25 Hertha Metals, Inc. Method and apparatus for metals, alloys, mattes, or enriched and cleaned slags production from predominantly oxide feeds

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
LI BIN ET AL: "The Preparation of High-Purity Iron (99.987%) Employing a Process of Direct Reduction-Melting Separation-Slag Refining", vol. 13, no. 8, 14 April 2020 (2020-04-14), CH, pages 1839, XP093193338, ISSN: 1996-1944, Retrieved from the Internet <URL:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7215521/pdf/materials-13-01839.pdf> [retrieved on 20240807], DOI: 10.3390/ma13081839 *

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