US20260022430A1 - A method for producing molten pig iron into an electrical smelting unit - Google Patents

A method for producing molten pig iron into an electrical smelting unit

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Publication number
US20260022430A1
US20260022430A1 US18/997,165 US202218997165A US2026022430A1 US 20260022430 A1 US20260022430 A1 US 20260022430A1 US 202218997165 A US202218997165 A US 202218997165A US 2026022430 A1 US2026022430 A1 US 2026022430A1
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US
United States
Prior art keywords
product
steel
iron
pig iron
ironmaking
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
US18/997,165
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English (en)
Inventor
Jean-Christophe HUBER
Mathieu Sanchez
Simon Pierre DEPLECHIN
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.)
ArcelorMittal SA
Original Assignee
ArcelorMittal SA
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 ArcelorMittal SA filed Critical ArcelorMittal SA
Publication of US20260022430A1 publication Critical patent/US20260022430A1/en
Pending legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B11/00—Making pig-iron other than in blast furnaces
    • C21B11/10—Making pig-iron other than in blast furnaces in electric 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
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B13/00—Making spongy iron or liquid steel, by direct processes
    • C21B13/0086—Conditioning, transformation of reduced iron ores
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B13/00—Making spongy iron or liquid steel, by direct processes
    • C21B13/12—Making spongy iron or liquid steel, by direct processes in electric 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
    • C21B13/14—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
    • C21B3/00—General features in the manufacture of pig-iron
    • C21B3/04—Recovery of by-products, e.g. slag
    • 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
    • C21C5/28—Manufacture of steel in the converter
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B2200/00—Recycling of non-gaseous waste material

Definitions

  • the present invention is related to a method of manufacturing pig iron, also called hot metal and to a method of producing steel out of such pig iron.
  • BF-BOF route consists in producing hot metal in a blast furnace, by use of a reducing agent, mainly coke, to reduce iron oxides and then transform hot metal into steel into a converter process or Basic Oxygen furnace (BOF).
  • a reducing agent mainly coke
  • BOF Basic Oxygen furnace
  • the second main route involves so-called “direct reduction methods”.
  • direct reduction methods are methods according to the brands MIDREX®, FINMET®, ENERGIRON®/HYL, COREX®, FINEX® etc., in which sponge iron is produced in the form of HDRI (hot direct reduced iron), CDRI (cold direct reduced iron), or HBI (hot briquetted iron) from the direct reduction of iron oxide carriers.
  • Sponge iron in the form of HDRI, CDRI, and HBI undergoes further processing in electric furnaces to produce steel.
  • An aim of the present invention is to remedy the drawbacks of the pig iron and steelmaking manufacturing routes by providing a new route efficiently minimizing the environmental impact of such manufacturing without incurring heavy investments.
  • the present invention provides a method for producing molten pig iron into an electrical smelting unit, comprising the steps of:
  • the present invention also provides a method for manufacturing steel method wherein pig iron manufactured according to the above is transferred from said smelting furnace to a converter wherein the carbon content of said pig iron is then lowered to a value below 2.1 percent in weight by oxygen blowing, so as to obtain liquid steel.
  • FIG. 1 illustrates schematically a pig iron and steelmaking process according to the smelting/BOF route
  • FIG. 2 illustrates schematically a smelting furnace.
  • FIG. 1 illustrates schematically a steel production route according to the DRI route, from the reduction of iron to the casting of the steel into semi-products such as slabs, billets, blooms, or strips.
  • Iron ore 10 is first reduced in a direct reduction plant 11 .
  • This direct reduction plant 11 may be designed to implement any kind of direct reduction technology such as MIDREX® technology or Energiron®.
  • the direct reduction process may for example be a traditional natural-gas or a biogas-based process.
  • the DRI product used in the method according to the present invention is manufactured using a reducing gas based on biogas coming from combustion of biomass.
  • the carbon content of the DRI product can be set to a maximum of 3% in weight and usually to a range of 2 to 3% in weight.
  • the DRI product used in the method according to the present invention is manufactured through a so called H 2 -DRI process where the reducing gas comprises more than 50% and preferably more than 60, 70, 80 or 90% in volume of hydrogen or is even entirely made of hydrogen.
  • the H 2 -DRI product will contain a far lower level of carbon than the natural gas or biogas DRI, so typically below 1% in weight or even lower.
  • the hydrogen used in the DRI reducing gas comes from the electrolysis of water, which is preferably powered in part or all by CO 2 neutral electricity.
  • CO 2 neutral electricity includes notably electricity from renewable source which is defined as energy that is collected from renewable resources, which are naturally replenished on a human timescale, including sources like sunlight, wind, rain, tides, waves, and geothermal heat.
  • the use of electricity coming from nuclear sources can be used as it is not emitting CO 2 to be produced.
  • DRI Direct Reduced Iron
  • the DRI product can be transferred to the smelting furnace in various forms.
  • the directly reduced iron product (DRI product) is fed to the smelting furnace in a hot form as HDRI product (so-called Hot DRI), or in a cold form as CDRI product (so-called Cold DRI), or in hot briquette form as HBI product (so-called Hot Briquetted Iron) and/or in particulate form, preferably with an average particle diameter of at most 10.0 mm, more preferably with an average particle diameter of at most 5.0 mm.
  • the direct reduction plant 11 It is preferably charged directly at the exit of the direct reduction plant 11 as a hot product with a temperature from 500° C. to 700° C. This allows reducing the amount of energy needed to melt it.
  • hot charging is not possible, for example if the direct reduction plant 11 and the smelting furnace 13 are not on same location, or if the smelting furnace 13 is stopped for maintenance and thus DRI product must be stored, then the DRI product may be charged cold, or a preheating step may be performed.
  • the smelting furnace 13 uses electric energy provided by several electrodes to melt the DRI product 12 and produce a pig iron 14 .
  • part or all of the electricity needed comes from CO 2 neutral electricity. Further detailed description of the smelting furnace will be given later, based on FIG. 2 .
  • the pig iron 14 can be optionally sent to a desulphurization station to perform a desulphurization step.
  • This desulphurization step may be performed in a dedicated vessel or preferentially directly in the pig iron ladle to avoid molten metal transfer and associated heat losses.
  • This desulphurization step is needed for production of steel grades requiring a low Sulphur content, which is, for example set at a maximum of 0.03 weight percent of Sulphur.
  • Desulfurization in oxidizing conditions is not effective and is thus preferentially performed either on pig iron before oxygen refining, or in steel ladle after steel deoxidizing. For very low sulfur contents, for example below 0.004 weight percent of sulfur, deoxidizing and desulphurization are combined for overall higher performance. Low sulfur grades thus benefit from performing pig iron desulfurization before the conversion step.
  • Desulphurization of the pig iron 14 can be done by adding reagents, notably based on calcium or magnesium compounds, such as sodium carbonate, lime, calcium carbide, and/or magnesium into the pig iron 14 . It may be done for example by injection of those reagents in the pig iron ladle.
  • the desulphurized pig iron 16 has preferentially a content of Sulphur lower than 0.03% in weight and preferably lower than 0.004% in weight.
  • Liquid steel 19 thus formed can then be transferred, whenever needed, to one or more secondary metallurgy tools 20 A, 20 B such as Ladle furnaces, RH (Ruhrstahl-Heareus) vacuum vessel, Vacuum Tank degasser, alloying and stirring stations, et cetera to be treated to reach the required steel composition according to the steel grades to be produced.
  • Liquid steel with the required composition 21 can then be transferred to a casting plant 122 where it can be turned into solid products, such as slabs, billets, blooms, or strips.
  • the smelting furnace 13 is composed of a vessel 20 able to contain hot metal.
  • the vessel 20 may have a circular or a rectangular shape, for example.
  • This vessel 20 is closed by a roof provided with some apertures to receive electrodes 22 to be inserted into the vessel 20 and with other apertures to allow charging of the raw materials into the vessel 20 .
  • the vessel 20 is also provided with at least one tap hole 25 to allow tapping of manufactured pig iron.
  • tap holes 25 are located in the lower part of the vessel 20 . They may be located in the lateral walls of the vessel or in its bottom wall.
  • the electrodes 22 provide the required electric energy to melt the charged raw materials and form pig iron. They are preferably Sbderberg-type electrodes.
  • a pig iron 14 layer which is the densest and is thus located at the bottom of the vessel 20 and a slag layer 23 located above the pig iron 14 .
  • the slag layer 23 can be partially covered by piles of raw materials 24 waiting to be melted.
  • the smelting furnace 13 may be a SAF (Submerged-Arc Furnace) wherein the electrodes 22 are immersed into the slag layer 23 or an OSBF (open-slag bath furnace) wherein the electrodes 22 are located above the slag layer 23 . It is preferentially an OSBF as illustrated in the figures.
  • At least one steel or ironmaking by-product-based material containing more than 10% in weight of slag forming agents are also charged in the smelting furnace 13 .
  • These slag forming agents may be chosen among at least one of CaO, lime, alumina, magnesia, aluminosilicate. They are preferentially CaO or Alumina which allows to get a slag composition suitable for usage in cement industry.
  • the by-products used to form the by-product-based material may be chosen among at least one of sintering dust or sludges, steelmaking dust or sludges, smelting dust or sludges, electric arc furnace slag, basic oxygen furnace slag, secondary metallurgy slag or mill scale. It may also be a mixture of those different by-products.
  • Sintering or steelmaking dust/sludges or smelting dust/sludges are sludges resulting from the dedusting of exhaust gases from the considered furnaces, such as Basic Oxygen Furnace, Electric Arc furnaces, sintering plants and smelting furnaces. They will be in form of sludge or dust depending on the treatment applied to the exhaust gas, either a dry treatment, such as use of fabric filters or a wet treatment such as water spraying. Electric arc furnace slag and basic oxygen slag or secondary metallurgy slags are slag formed during the liquid steel production.
  • Mill scale is the flaky surface of hot rolled steel, consisting of the mixed iron oxides iron(II) oxide (FeO), iron(III) oxide (Fe2O3), and iron(II,III) oxide (Fe3O4, magnetite). Mill scale is formed on the outer surfaces of steel plates, sheets or profiles when they are being produced by rolling steel semi-products in rolling mills.
  • Typical compositions of some by-products are indicated in table 1 below. All percentages are expressed in weight percent.
  • the content encompasses content of metallic iron (Fe) or any oxides (FeO, Fe2O3, Fe3O4).
  • the by-product contains also at least 20% in weight of iron, part of this iron being under an oxidised form.
  • iron recovery rate is very high in smelting operation, more than 90%, which is much higher than in current recycling practices. For example, recycling in current steelmaking vessels may lead to a partial or low iron reduction thus increasing slag mass and oxidation rate which imply extra cost in energy for heating and melting without recovering iron.
  • the by-products are fed to the smelting furnace in form of briquettes or pellets.
  • they may first be subjected to preparation steps, including, but not limited to crushing and sieving of the chosen by-products followed by the mixing of the sieved by products so as to obtain the requited material composition, namely a 10% in weight of slag forming agents and optionally at least 20% in weight of iron. This allows to increase versatility in the sources and the combination of the different mentioned materials to form mixed briquettes or pellets.
  • a carbon-containing material is also added to the smelting furnace. Reaction of carbon with oxygen in the converter creates carbon monoxide gas, which provides intense and efficient stirring of the molten metal and thus improves the removal of impurities from the steel. This reaction is also exothermic and therefore provides additional energy for scrap melting. The more scrap is used, the smaller the environmental footprint of the process.
  • the carbon content of the pig iron 14 produced through the DRI route will generally be lower than 3% in weight.
  • the pig iron should preferentially have a carbon content as close as possible to 4.5% in weight, which is the level of saturation.
  • the pig iron carbon content is set in the range of 4.0 to 4.5% in weight through the addition of carbon containing material.
  • the carbon containing material may come from different sources. It may be chosen, for example, among coke, anthracite, silicon carbide, calcium carbide, or a mixture of any of those sources, but can also advantageously come from renewable sources like biomass for part or all the carbon loads. In particular, biochar can be used. Adding calcium carbide is particularly advantageous as the calcium atoms can provide a desulphurizing effect.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Geology (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
  • Manufacture Of Iron (AREA)
  • Carbon Steel Or Casting Steel Manufacturing (AREA)
US18/997,165 2022-07-29 2022-07-29 A method for producing molten pig iron into an electrical smelting unit Pending US20260022430A1 (en)

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Application Number Priority Date Filing Date Title
PCT/IB2022/057048 WO2024023569A1 (en) 2022-07-29 2022-07-29 A method for producing molten pig iron into an electrical smelting unit

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US (1) US20260022430A1 (enExample)
EP (1) EP4562190A1 (enExample)
JP (1) JP2025524841A (enExample)
KR (1) KR20250024059A (enExample)
CN (1) CN119630814A (enExample)
AU (1) AU2022471177A1 (enExample)
CA (1) CA3258205A1 (enExample)
MA (1) MA71592A (enExample)
MX (1) MX2025001159A (enExample)
WO (1) WO2024023569A1 (enExample)
ZA (1) ZA202408838B (enExample)

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WO2025219738A1 (en) * 2024-04-15 2025-10-23 Arcelormittal A steelmaking method

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AT406272B (de) * 1997-11-10 2000-03-27 Voest Alpine Ind Anlagen Verfahren zur herstellung von direkt reduziertem eisen, flüssigem roheisen und stahl sowie anlage zur durchführung des verfahrens
WO2014190391A1 (en) * 2013-08-19 2014-12-04 Gomez Rodolfo Antonio M A process for producing and reducing an iron oxide briquette
JP6237664B2 (ja) * 2015-02-09 2017-11-29 Ｊｆｅスチール株式会社 アーク炉の操業方法及び溶鋼の製造方法
LU101960B1 (en) * 2020-07-28 2022-01-28 Wurth Paul Sa Method for operating a metallurgic plant for producing iron products

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EP4562190A1 (en) 2025-06-04
JP2025524841A (ja) 2025-08-01
WO2024023569A1 (en) 2024-02-01
KR20250024059A (ko) 2025-02-18
ZA202408838B (en) 2025-12-17
CA3258205A1 (en) 2024-02-01
MX2025001159A (es) 2025-03-07
AU2022471177A1 (en) 2024-12-12
MA71592A (fr) 2025-05-30
CN119630814A (zh) 2025-03-14

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