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WO2025194266A1 - Processus et four électrique de fusion pour produire un métal chaud à partir de fer préréduit - Google Patents

Processus et four électrique de fusion pour produire un métal chaud à partir de fer préréduit

Info

Publication number
WO2025194266A1
WO2025194266A1 PCT/CA2025/050386 CA2025050386W WO2025194266A1 WO 2025194266 A1 WO2025194266 A1 WO 2025194266A1 CA 2025050386 W CA2025050386 W CA 2025050386W WO 2025194266 A1 WO2025194266 A1 WO 2025194266A1
Authority
WO
WIPO (PCT)
Prior art keywords
feed
esf
furnace
peripheral region
dri
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/CA2025/050386
Other languages
English (en)
Inventor
Jacques Pilote
Terrence Koehler
Isabelle NOLET
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.)
Hatch Ltd
Original Assignee
Hatch Ltd
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 Hatch Ltd filed Critical Hatch Ltd
Publication of WO2025194266A1 publication Critical patent/WO2025194266A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B3/00—Hearth-type furnaces, e.g. of reverberatory type; Electric arc furnaces ; Tank furnaces
    • F27B3/08—Hearth-type furnaces, e.g. of reverberatory type; Electric arc furnaces ; Tank furnaces heated electrically, with or without any other source of heat
    • 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
    • C21B3/00—General features in the manufacture of pig-iron
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B3/00—Hearth-type furnaces, e.g. of reverberatory type; Electric arc furnaces ; Tank furnaces
    • F27B3/08—Hearth-type furnaces, e.g. of reverberatory type; Electric arc furnaces ; Tank furnaces heated electrically, with or without any other source of heat
    • F27B3/085—Arc furnaces
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B3/00—Hearth-type furnaces, e.g. of reverberatory type; Electric arc furnaces ; Tank furnaces
    • F27B3/10—Details, accessories or equipment, e.g. dust-collectors, specially adapted for hearth-type furnaces
    • F27B3/18—Arrangements of devices for charging

Definitions

  • the present invention relates to iron-making and steel-making processes and more specifically to processes for producing hot metal from a feed comprising direct reduced iron using an electric smelting furnace.
  • Blast furnaces have historically been used in the process to produce steel.
  • the blast furnace produces liquid pig iron (hot metal) from iron ore.
  • the pig iron is then processed in a downstream steel-making vessel, typically a basic oxygen furnace (BOF), to produce steel.
  • BEF basic oxygen furnace
  • Iron ore is charged to blast furnaces along with carbonaceous material such as coke (a derivative of coal) to reduce the iron ore to a metallic form and fluxes to facilitate the formation of a suitable slag phase to allow for separation of undesired elements (for example non-iron oxides including silica, alumina, lime, magnesia, titania) typically referred to as gangue from the iron product.
  • DRI direct reduced iron
  • sponge iron is a solid-state product that is produced by reducing iron ore or other iron bearing material. Carbon monoxide and hydrogen from coal or natural gas may be used as carbonaceous materials for DRI production. Gangue material in the iron ore or other iron bearing feed material remains with the DRI product and must be removed in the downstream smelting unit.
  • EAFs electric arc furnaces
  • EAFs are batch furnaces used for converting predominantly scrap charge into molten steel.
  • EAFs transform electric energy to thermal energy by forming an arc between the furnace electrodes and feed material within. This thermal energy forms a significant portion of the energy necessary to melt the feed allowing the separation of a slag phase from the molten steel of a specific grade.
  • the molten steel is formed within the EAF, itself.
  • EAFs are a mature steelmaking furnace whose main raw material is scrap metal containing iron. They have been in common operation for well over 40 years. For some EAFs, all of the charged feed is scrap metal containing iron. An EAF can, however, also receive some other iron-containing materials in lower quantities, including DRI, hot briquetted iron (HBI), hot metal (HM) (molten pig iron typically received from a blast furnace), and ingots of solidified pig iron. Worldwide, scrap metal containing iron makes up more than 75% of the metal-containing feed that is provided to EAFs.
  • HBI hot briquetted iron
  • HM hot metal
  • scrap metal containing iron makes up more than 75% of the metal-containing feed that is provided to EAFs.
  • Figure 1A shows a cross-section of an operating electric smelting furnace in accordance with an embodiment of this invention.
  • Figure 1B shows a cross-section of another embodiment of the operating electric smelting furnace in accordance with this invention.
  • Figure 1C shows a cross-section of a further embodiment of the operating electric smelting furnace in accordance with this invention.
  • Figure 2A shows a configuration of a DRI-ESF illustrating the location of the various regions where feed is melted within the vessel according to an embodiment of the invention.
  • Figure 2B shows a configuration of a DRI-ESF illustrating the location of the various regions where feed is melted within the vessel according to an embodiment of the invention.
  • the inventors have discovered that a number of challenges arise when attempting to use a high-capacity electric smelting furnace, which may conventionally be used for non-ferrous smelting, to smelt feed comprising DRI.
  • One of the main challenges is maintaining and controlling the operating conditions of such a furnace, including because of the unique characteristics of DRI, and the specification requirements for the resulting slag and molten pig iron, as compared to other non-ferrous feeds and their resulting products.
  • DRI as a feed material for an electric smelting furnace (ESF or DRI- ESF) to produce iron and slag that is similar to that produced by a blast furnace presents challenges that are not typically encountered when feeding an ESF with typical non-ferrous materials.
  • a reason for this is the nature of the DRI feed material and the specification requirements for the slag and iron.
  • DRI is highly reduced: it may contain up to 96% of the contained iron as metallics and is an electrically conductive material.
  • DRI may comprise much lower gangue relative to typical feeds, and there is often a desire for a high degree of carburization of the produced liquid metal (i.e. % C in Hot Metal).
  • the high electrical conductivity of the DRI feed material means that DRI feed material that bridges between the electrodes of the furnace will create a short-circuit path, which is highly different from the targeted electrical circuit which flows across the slag bath and through the metal bath. Operating between these two electrical circuits will cause severe furnace control instability.
  • conventional ESF non-ferrous feed materials have high gangue assay which make them impractical to tightly control slag chemistry such that the slag is of assumed low value.
  • slag produced by iron-ore blast furnaces is commonly used in high value-in-use applications, such as use as an additive in creation of portland cement or a high value aggregate material.
  • DRI- ESF DRI- ESF with specific slag chemistry of low variability which is suitable for downstream value- in-use applications.
  • This is challenging, however, due to variability in melting conditions in the ESF and variability in raw material specifications.
  • the DRI-ESF seeking to replace the blast furnace can also produce a slag capable of being used for such unrelated downstream applications, but this requires tight control over the slag chemistry and therefore tight control over the operation of the DRI-ESF.
  • the present invention is for a process, system, and method for producing hot metal in an ESF using DRI to help address the foregoing challenges.
  • the process, system, and method comprise controlling the ESF.
  • the control may be obtained through the provision of feed to the ESF.
  • Such control has the flexibility to both help minimize changes to melting behavior in the furnace and to help respond to deviations in product (metal and/or slag) from target with rapid chemistry adjustment in the DRI-ESF during operation.
  • Such adjustments may help increase or decrease the feed melting rate, distribution of carbon between reduction and carburizing reactions and/or partition of minor elements between the slag, metal and furnace off-gas.
  • the DRI-ESF is provided with a first feed comprising DRI.
  • the first feed is provided to a peripheral region of the DRI-ESF.
  • the DRI-ESF is also provided with a second feed.
  • the second feed is provided to a nonperipheral region of the DRI-ESF.
  • the second feed may or may not comprise DRI.
  • the first feed may or may not have the same or similar composition as the second feed.
  • the first and second feeds may have different proportion of DRI from 0% to 100% in mass ratios
  • the DRI-ESF smelts the first feed and the second feed using electrical energy applied to an electrode.
  • the DRI-ESF forms a molten bath comprising a molten slag residing above the molten hot metal.
  • the provision of each of the first feed and the second feed to the DRI- ESF may be independently controlled to help control the operation of the DRI-ESF.
  • the present invention relates to an electric smelting furnace (ESF) for producing hot metal, where the ESF comprises a first feed port positioned to provide a first feed comprising direct reduced iron (DRI) to a peripheral region of the ESF and a second feed port positioned to provide a second feed to a non-peripheral region of the ESF.
  • the ESF further comprises electrodes extending into the ESF for providing electrical energy for heating the ESF, and a feed system for controlling provision of the first feed to the peripheral region and of the second feed to the non-peripheral region to control the operation of the ESF.
  • the DRI-ESF feed material may comprise primary feed mix and an additive mix.
  • the first feed being provided to the peripheral region of the DRI-ESF may comprise the primary feed mix
  • the second feed being provided to the non-peripheral region of the DRI-ESF may comprise the additive mix.
  • the primary feed mix (PFM) comprises DRI as a majority component.
  • the PFM may also contain flux such as lime, dolime, bauxite and/or other slag modifying materials, solid carbonaceous materials such as coal, charcoal, biomass or coke and iron-bearing scrap material.
  • the iron-bearing scrap-material may be of similar size as the DRI.
  • the Additive mix may comprise flux, carbonaceous materials, pelletized dusts and sludges from off-gas treatment, oxidized iron-containing revert materials such as mill scale, iron-bearing scrap material of variable size or iron ore pellets.
  • the AM may also comprise DRI.
  • the AM may comprise DRI in a minority amount.
  • the AM DRI could potentially be off-specification material based on size, assay or temperature.
  • a system, process, and method of providing PFM and AM to a DRI-ESF is disclosed.
  • the PFM and AM are provided to the DRI-ESF to help control the operation of the DRI-ESF.
  • FIG. 1A and 1B each show a cross-section of an operating DRI-ESF 200 in accordance with embodiments of this invention.
  • the DRI-ESF 200 comprises a hearth with walls 200a and floor 200b, an electrode 202, and a molten bath.
  • the molten bath comprises a molten slag layer 204, a molten metal layer 206 beneath the molten slag layer 204.
  • the DRI-ESF also comprises a peripheral structure 208 comprising a feedbank.
  • the DRI-ESF is provided with a first feed A and a second feed B.
  • the first feed A and second feed B are provided to different locations within the furnace 200.
  • the first feed A help provide the peripheral structure 208.
  • the first feed A may be a PFM.
  • the second feed B may be an AM.
  • the first feed A may be provided into the furnace 200 through a feed port 210 in the roof of the furnace 200.
  • the second feed B may be provided into the furnace 200 through a second feed port 212 in the roof of the furnace 200.
  • the DRI-ESF is also provided with a third feed C.
  • the third feed C may be the same as or different than the first feed A and the second feed B.
  • the third feed may be PFM or AM.
  • the third feed B may be provided into the furnace 200 through a third feed port 214 in the roof of the furnace 200.
  • Each of the first feed port 210, second feed port 212, and third feed port 214 may be individually or collectively referred to herein as a feed port or feed ports, respectively.
  • the first feed port is positioned above the peripheral region of the ESF to direct the first feed (comprising DRI) to the peripheral region of the ESF and to the periphery structure
  • the second feed port is positioned above the non- peripheral region of the ESF to direct second feed to the non-peripheral region of the ESF.
  • the feed ports may be positioned in different positions and have components coupled thereto in order to direct the first feed (comprising DRI) to the peripheral region of the ESF and second feed to the non-peripheral region of the ESF.
  • FIGS 2A and 2B show a top view of a representation of a circular and rectangular DRI-ESF, respectively, in accordance with an embodiment of the invention.
  • the DRI-ESF comprises a peripheral and non-peripheral region.
  • the non-peripheral region comprises a semi-central region and a central region.
  • a first feed comprising DRI is provided to the peripheral region of the DRI-ESF.
  • the first feed may be PFM.
  • the PFM may in addition be provided to the non-peripheral region of the furnace (such as the semi-central or central region of the furnace) to help control the furnace throughput and the properties (e.g. assay and temperature) of the produced metal, slag and off-gas.
  • a second feed is provided to the central region of the furnace.
  • the second feed may be PFM or AM.
  • the second feed (such as AM) may in addition be provided to the semi-central and/or peripheral regions of the furnace to help control furnace throughput, and properties of the produced metal, slag and off-gas.
  • Controlling the provision of PFM and AM comprises controlling the ratio of PFM and AM, and/or controlling the distribution to the various regions of the furnace.
  • controlling the provision of the first feed to the peripheral region may be independent of controlling the second feed to the non-peripheral region. Additionally, or alternatively, provision of the first feed to the peripheral region may also be coordinated with providing the second feed to the non-peripheral region in order to help control the furnace throughput and the properties of the produced metal, slag and off-gas.
  • each of the furnace regions may be provided with a first feed I second feed (such as PFM I AM) comprising the same or a different composition, or the PFM I AM composition may be varied for each of the furnace regions.
  • the central region may be provided with a PFM that is significantly lower in carbonaceous material than the PFM that is provided to the periphery of the furnace.
  • the central region may be provided with an AM that comprises a significantly higher proportion of oxidized revert or iron ore than the AM provided to the other regions.
  • Control of each of the PFM and AM feed streams to each of the regions provides levers through which the operations of the DRI-ESF may be regulated to produce on specification hot metal, slag and off-gas at select throughput.
  • the feed(s) may comprise materials other than DRI.
  • the DRI may be smelted with such other materials to help obtain a high yield of iron to the metal phase (i.e.
  • the operations of the DRI-ESF may be controlled by manipulating the ratio of the first feed and the second feed being provided to the DRI-ESF, controlling the ratio of PFM to AM being provided to the DRI-ESF, controlling which region (peripheral and nonperipheral, with non-peripheral comprising semi-central and central region) the PFM and AM is added to, and controlling the specific blends of PFM and AM feeding each of the regions of the ESF.
  • the operations of the DRI-ESF that may be controlled in accordance with an embodiment of the invention, including the foregoing, comprising: the assay/chemistry of the products within the furnace (including hot metal, slag or off-gas), the material throughput of the furnace, the temperatures of the products leaving the furnace, the furnace heat losses, the yield of iron to hot metal, the reactions occurring (including the rate at which they are occurring) in the ESF, the distribution of minor elements between the product phases (including silicon, phosphorus, sulphur, zinc, magnesium, chrome, lead, etc.), the area covered with solid feed, wear rates of refractory in the furnace, and the electrical resistance between electrodes or electrode pairs in the ESF I the conductivity of the slag in the ESF.
  • a first feed is provided to the periphery (and optionally semi-centre) of the ESF to form and maintain peripheral structure(s) (also referred to as feedbanks).
  • Part of a feedbank may be a visible heap above the molten bath with the other portion of the feedbank immersed in the bath.
  • the first feed may be provided to the periphery through openings in the roof of the DRI-ESF that are directly apex of the feedbank.
  • Providing feedbanks along the periphery of the DRI-ESF in accordance with an embodiment of this invention may help to protect the furnace refractory layer from damage from molten slag and/or molten metal within the furnace and lower heat losses through the furnace sidewalls.
  • feedbanks to protect the DRI-ESF wall refractory may permit a wider range of slag chemistries (some of which may be harmful to the refractory) by inhibiting slags with chemistry that is harmful to the refractory from coming into contact with the refractory.
  • Such feedbanks may also provide a material feed buffer in the event of an ESF process excursion away from the targeted furnace operating window.
  • the top part of the bank covering the surface of the bath helps to reduce convective and/or radiative heat losses from the bath thereby improving furnace energy efficiency and protecting the furnace sidewall and roof. Feed material in the peripheral feedbanks is less preferentially melted than material fed to the non-periphery and thus the inventory (i.e.
  • the feed rates are selected to be different at different sections along the furnace periphery and non-periphery.
  • the section feed rates may be selected to help avoid blocking one or more tapholes with a feedbank to allow tapping through active tapholes, or cooling a resting idled taphole by restoring a thick bank.
  • the feedbanks can extend into the metal bath and assist by protecting the lining at the tidal zone
  • the provision (including composition) of feed is controlled to the peripheral regions and non-peripheral regions of the ESF to help improve carburization of the hot metal.
  • a first feed e.g. PFM
  • PFM a first feed
  • the first amount of periphery feed comes to rest in the feedbank.
  • the additional carbon within the peripheral feedbank helps leave a carbon rich bottom of the feedbank that can penetrate into the molten iron bath due to pressure from the weight of the feedbank above the molten bath.
  • this high carbon bottom may form a competent structure while in the feedback due to sintering with other high melting point materials within the feedbank.
  • This carbon rich bottom may then as a result of the weight above be pushed past the slag so as to penetrate the metal bath where it can finally melt to drive desirable carburization reactions within the molten metal.
  • the carbon in the first feed may be from a carbonaceous material and I or a DRI containing carbon.
  • a second amount of periphery feed comprising of PFM, potentially with a different amount of carbon than the average, may be provided to the semicentral region.
  • the second amount of periphery feed may be provided to help inhibit excessive sloughing of peripheral feedbank material towards the electrode and segregation of the carbon contained within.
  • At least some DRI must be provided to the periphery of the furnace in accordance with the invention since providing all of the DRI to the open bath in the centre region would likely result in a covered bath and loss of at least a partially open bath. In an embodiment, it is important for the DRI-ESF to have a partially open bath.
  • an electric smelting furnace may operate in the modes of shielded arc; brush arc, partially open bath; immersed electrode, open bath; brush arc, covered bath; and submerged arc.
  • a fully covered bath is detrimental to the operation of the DRI-ESF in accordance with the invention since feed between the electrodes can result in a short circuit path and loss of sufficient bath resistance to allow for required power input.
  • At least some DRI may be charged to the open bath region in the centre or semi-centre to increase furnace production of hot metal.
  • the open bath region is adjacent to the electrodes and is therefore the hottest part of the bath which will melt the DRI the fastest and result in increased hot metal productivity.
  • providing AM materials and/or PFM to the open bath region from time-to-time may allow for adjusting quickly the slag and/or metal composition. This may help recover from any unwanted furnace excursions/upsets.
  • a second feed comprising a greater amount or proportion of DRI may be provided to an open bath area of the ESF-DRI to increase the hot metal throughput of the ESF-DRI.
  • the DRI By providing the DRI to the open bath, the DRI is smelted more quickly (by entering the molten bath directly and at a location that is typically higher in temperature) than if it were provided to the feedbanks which are typically located around the periphery of the ESF.
  • feed (such as AM or PFM material) devoid or mostly devoid of carbon may be provided to the central region of the furnace to help achieve a high DRI consumption rate to help achieve a select metal production rate.
  • the central region of the ESF-DRI should comprise the open bath.
  • the centre feed rate may be controlled to help inhibit formation of feedbanks and help provide and/or maintain an open bath proximate to the centre of the furnace to prevent a short-circuit path from forming between the electrodes via feed.
  • Additional AM with iron values (such as steel scrap) may be added to the centre of the furnace to increase the production rate.
  • the PFM is fed predominately to the periphery and semi-centre of the ESF
  • the AM is predominately fed to the central area of the ESF where the bath is open and where the energy delivery dynamic is greatest.
  • PFM material may come to rest in the charge banks around the periphery of the furnace or it may slide down the electrode facing slope of the charge bank to the open bath area. Material coming to reside in the charge banks takes significantly longer to melt in the furnace than material which reaches the open bath, and the PFM charging strategy can result in layers of materials of different compositions or melting properties. As such, with only peripheral feeding of PFM, control of slag properties, which are critical for high throughput operation of the ESF, such as electrical conductivity, liquidus, chemical composition, etc. could be quite challenging.
  • AM material which may or may not contain DRI is provided to the non-peripheral area of the furnace where the bath is open. Unlike the material provided to the peripheral, which can come to rest in charge banks at some random proportion, this material melts in a highly predictable way and hence can be used to help quickly resolve issues with slag properties such as electrical conductivity, liquidus or composition being outside the optimal envelope.
  • the invention provides for a means of effectively controlling transients in slag chemistry which may be deleterious to high throughput ESF operation. Furthermore, this may help assist with controlling the ESF during power reductions, idling and power increase conditions where the melting rate differentials between the material melted at the interface between slag and charge bank and in the open bath change significantly.
  • furnace upset conditions in slag and/or hot metal chemistry may be overcome by providing a greater amount or greater rate of feed to the open bath relative to the amount/rate being provided to the periphery. Feeding PFM to the ESF open bath can allow for increased carbon content in peripheral feed, help prevent bank sintering, help in carburization of hot metal, and help reduction of contaminants such as silicon or phosphorous in the hot metal.
  • Another upset type is disturbance of the electrical path.
  • the open bath closes over with feed material, it may negatively disturb electric operation of the furnace. Electricity is intended to flow from electrodes connected to one phase, through a short arc, the liquid slag and metal bath, to electrodes connected to other phases. The arc and molten slag provides resistance which generates heat. If solid DRI closes over the open bath, this can cause short circuiting between the electrodes (electricity flows instead through the conductive solid DRI because it contains high amounts of metal) which in-turn negatively affects furnace heating by greatly lowering the resistance. Independent control of the provision of feed to the peripheral, semi-central and central region can help mitigate this issue.
  • controlling the feedrates of the feed to those regions can help control the location and size of feed banks in the furnace to achieve select bath chemistry which in-turn help achieve and maintain a partially open bath.
  • the partially open bath may be maintained even at high feedrates in balance with the delivered power through controlling the provision of the feed to the regions. Should the partially open bath be compromised due to process upsets, in an embodiment, the control of the feed to the three regions (and by adjusting locally the feed/power ratio) can help achieve the necessary furnace conditions to re-establish the partially open bath without having to resort to operating the furnace at lower throughputs for a sustained period of time.
  • the feed may be provided to the DRI-ESF to achieve the feedbanks a select distance from the electrodes, based on the slag inventory, to help avoid creating a least resistance electrical circuit path through the peripheral feed banks rather than through the slag located under the electrode.
  • the feed may be provided to the DRI-ESF such that the slag bath surrounding the electrode is free of DRI feedbanks to help avoid creating a similar least resistance electrical path between the electrodes.
  • the central region and/or the semi-central region of the ESF is an open bath.
  • the feeding system may allow for the distribution of the feed to the areas of the furnace that have an open bath, and the areas of the furnace that do not have an open bath, to help maintain the physical integrity of the electrical circuit.
  • the localization of the power delivery across the layer of the slag to support the smelting reaction is controlled by the combination of the slag resistance (temperature, slag basicity, level of reduction) and characteristics of the power delivery system (flexible circuit resistance at different furnace powers).
  • the balance between the power resistance and the slag bath resistivity determines the ratio P a rc/Pbath and the fine distribution on the vertical axis of the power delivery in the furnace.
  • the control of the electrical resistance of the power system (by generating lower current and higher voltage) delivers a higher Parc/Pbath ratio, which also affects intensity of the slag flow current generated by magnetic forces from the power delivery system.
  • the furnace flexibility of the central charging system targeting the open-bath zone around the electrode is important to the overall system.
  • the feeding system delivers calibrated addition of the main feed to help balance power and smelting energy required, and at the same time, the feeding system delivers other feeds to help maintain the slag resistance (fluxes) and additional carbonaceous material to help control the amount of reduction and enhance the carburization of the newly molten metal in the most active part of the furnace.
  • the system may deliver a flexible composition of individual constituents.
  • the system, process, and method provides feed to a peripheral structure and an open bath, and achieves a stable power delivery circuit with a flexible characteristic to support the location at which the smelting reaction occurs in the furnace.
  • a DRI-ESF which only receives feed materials at its periphery may be very slow to recover from such upset conditions due to the amount of time it would take for feed having the necessary chemistry to eventually reach the molten bath, to modify the slag or metal temperature or to re-establish the optimal degree of bath opening from an electrical path perspective. In such situations, without the present invention, the entire furnace throughput may need to be reduced until the necessary furnace operating condition profile is reestablished.
  • controlling the DRI-ESF may comprise increasing the PFM feed rate to the open bath to result in the feed melting faster (as compared to the rate of melting at the feedbanks) and therefore increase the furnace throughput while not leading to a significant increase in slag temperature and allowing for hot metal temperatures that do not constrain the downstream steel making processes.
  • Providing feed to the open bath and the feedbank increase furnace hot metal throughput not only due to the open bath melting the feed faster than a feedbank from the initial time the feed is provided, but also due to having a greater surface area of the furnace to which to provide feed.
  • Such control may also include the provision of different levels of carbonaceous material in the PFM predominately destined for the charge banks versus that predominately destined for the open bath area.
  • the downstream steel shop and its BOFs require the molten iron to be provided at a sufficient temperature to minimize cycle times, however overheated molten iron in the ESFs can lead to deterioration of the furnace refractories particularly in the region which is in contact alternately with slag and molten iron due to iron removal from the ESF.
  • Increasing the central feed (which when maintaining the required power to feed ratio will decrease the peripheral feed rate) of PFM can decrease slag tapping temperature, but substantially increase tapped molten iron temperature by driving the differential temperature between slag and iron down. Conversely, reducing the central feed ratio is expected to significantly increase the slag to molten iron temperature differential leading to a cooler molten iron bath and a hotter slag bath. This principle may also be repeated at different locations in the application in different ways. [0041] In an embodiment, feeding proportionally less of the PFM and/or AM material to an area of the furnace (either the ratio to the central, semi-central or peripheral regions or the bias to feed ports in the same region) to control the size and location of the open bath region of the furnace.
  • This control is performed to obtain the optimal degree of bath openness (optimal partially open bath) subject to constraints of electrical stability, heat losses to furnace roof and walls, molten iron and slag temperatures, carbon and minor elemental deportations to the metal, impurity distributions to slag, metal and fume and other furnace control parameters.
  • the area of open bath is decreasing in size (i.e. progressing towards a covered bath)
  • the feed being provided to central and/or semi-central region may be reduced or stopped entirely, or some or all the amount of the feed stream originally being provided to the open bath may be diverted so as to be provided instead to the periphery, including so that the total collective rate of feed being provided to the ESF as a whole does not change.
  • central feed may assist with controlling the most active part of the bath in the vicinity of electrodes (also referred to herein as the power delivery zone). Maintaining stable electrical conditions within the power delivery zone involves ensuring that highly conductive floating crusts of partially melted DRI or other conductive materials do not create a short-circuit between ESF electrodes.
  • the surface temperature of the feedbank can increase and favour more retention within the feedbank by increasing the angle of repose (AoR) or through partial sintering. This may, in turn, impact the feedbank, without encroaching into the power delivery zone between electrodes, causing them to sink deeper into the slag bath and impact furnace production.
  • AoR angle of repose
  • the semi-central feed ports can be located in a region of the furnace where they can form feedbanks with widest base that does not encroach on the power delivery zone, and can form a barrier that prevents significant sloughing of feed material down the electrode-facing surface of the peripheral feedbank. Sloughing is expected to impact segregation of the less dense reductant in the feedbank and could change the amount of carbon available at the bottom of the feedbank to participate in direct carburization of the molten iron bath. This principle may also be repeated at different locations in the application in different ways.
  • Hybrid feeding may further improve the foregoing embodiment by adjusting the ratio of carbonaceous material in the PFM material charged to the periphery of the furnace. If the charge feedbank is dense enough for the bottom of the feedbank to penetrate into the metal bath, then increasing the carbon content in this feed feedbank by mixing a different PFM recipe of DRI, flux, and carbonaceous material (before it enters the feedbank or open bath of the ESF) for material to be charged to the peripheral or semi-central areas versus that charged to the open bath region could further help control the degree of carburization. Altering the feed composition proportion and the exact delivery location to the open bath area of the furnace may help to limit undesirable reactions, such as minor element deportation into the metal or driving fuming reactions of volatile materials.
  • the ratio of feed to the central region is reduced to increase the slag bath temperature within the furnace for the goal of increasing the temperature at the point where melting and smelting reactions are occurring within the bath.
  • the increasing of the temperature of melting can promote the melting of iron with carbon contents towards the saturation limit through varying the ratio of feed provided to the central and/or semi-central regions. Varying the feed provided to the periphery further can be used with certain types of DRI to control the carbon deportation to the molten iron bath independently, or in conjunction with, the embodiments discussed above.
  • an increase in the ratio of feed provided to the peripheral region (relative to other regions) and/or a bias of feed to one or more feed ports in the peripheral region is provided to help protect the furnace refractory from excessive wear or to provide temporary protection to a damaged section of wall refractory by reducing direct contact with slag for a period of time to lower the wall heat flux and allow for residual slag to freeze in this area and provide protection.
  • Feed addition to the periphery of the furnace may be further adjusted to select particular size, height and/or density of the charge bank to promote penetration of the feed into the molten slag and metal, or the buoyancy of these structures, based on the desired conditions in the furnace.
  • the feedbanks have an angle of repose that may influence the shape of the feedbanks and overall stability of the peripheral structures.
  • select height of the feedbanks and the density of the banks may be the driving forces for the penetration depth of the feedbanks into the bath, the bath comprising slag and iron.
  • the feedbank penetration can be shallow and only protect the slag zone of the refractory or can dive into the metal and protect the lower slag/metal interface, also called the tidal zone.
  • the feed may be provided to each of the periphery and non-peripheral region in such a manner so as to achieve a select height, weight, and/or density to form competent feedbanks with a high angle of repose to help cause the feedbanks to sink to the level of the metal bath, providing protection where it is needed.
  • This may include increasing the amount of fines and/or fluxes provided to the PFM fed to the periphery to promote greater sintering within the feedbanks and hence a higher angle of repose and a feedbank which sinks more deeply.
  • an increase or decrease in the quantity of AM provided to the open bath area of the furnace to provide control over the slag bath chemistry is a critical parameter and owing to the melting behavior of the peripheral charge feedbanks it is possible that slag chemistry can become off-specification leading to upset conditions within the ESF or loss of value for the slag product.
  • Feeding flux materials containing silica, magnesia, lime and/or alumina as AM to the central region i.e. the open bath area
  • AM containing these materials can be added to the central region open bath area of the furnace, helping quickly resolve this issue.
  • material containing iron oxide can be mixed with the AM feed and this resulting feed provided to the central region of the furnace to increase the amount of iron reduction consuming the excess carbon floating in the open bath.
  • the ESF may be fed with DRI created using hydrogen (H2) or natural gas (NG).
  • H2 hydrogen
  • NG natural gas
  • the amount or rate of provision of periphery feed and open bath feed may differ depending upon whether the feed DRI was created using H2 or NG.
  • H2 more I a high rate of the feed may be provided to the periphery of the ESF than the open bath.
  • DRI created using NG more I a high rate of the feed may be provided to the open bath of the ESF than the periphery.
  • a greater amount of carbon may need to be included in the feed material.
  • the carbon may float free of the rest of the feed and collect and float on top of the slag at the electrodes. This is undesirable since the carbon does not reach to molten iron beneath the slag layer, and may instead turn into a carbon-containing gas or burn off.
  • the carbon in the feedbanks will become sintered with the other material in the feedbanks thereby preventing it from floating free.
  • the sintered feedbank carbon will then be forced - under the pressure of the feedbank material on top - to beneath the slag layer to the molten metal layer where it will be fully melted and chemically reacted with the molten iron.
  • provision of the feed to the central open bath area may be controlled as a first driver for adjusting the operating conditions of the DRI ESF (prior to changing overall feedrate and or power levels), with the provision of the feed to the periphery.
  • the periphery is slower to react but allows for adjustment over a larger number individual points (given the larger cross sectional area of the periphery) being controlled as a secondary driver for adjusting the operating conditions of the DRI ESF.
  • the greater number of periphery addition points provides advantage as the conditions at the furnace walls are local.
  • the ESF may have greater energy efficiency, higher average smelting rate and more rapidly respond to help maintain steady conditions in the ESF. Making adjustments along the many points of the periphery may allow for more control of local conditions at the furnace sidewalls and control stability of the feedbanks, preventing them from encroaching of the power delivery region of the furnace where they can disrupt the process by providing a short circuit path.
  • the feed is provided to the ESF to provide for an optimal feedbank.
  • the feedbank may be a select thickness so that it sufficiently protects the refractory in both the slag and tidal zone.
  • the feedbank may be a select size so that it does not collapse.
  • the feedbank may be a select height to protect the upper sidewall of the ESF from radiation lowering furnace heat losses.
  • the feedbank may be adjusted in height and density to allow the bottom of the feedbank to penetrate to a different depth the slag and metal bath which can affect the hot metal chemistry (for example carburization).
  • the DRI-ESF is configured to control and measure the feed material properties and distribution within the furnace to help control the size and position of the open bath within the furnace as well as the height, thickness, location, density, particle morphology, composition, mineralization and/or temperature of the furnace feed feedbanks, if any, in a non-open bath.
  • the DRI-ESF may control and measure the feed material properties and distribution within the furnace with a feed system coupled to the feed ports.
  • the feed system may comprise a primary feed system for providing the first feed to the peripheral region and a secondary feed system for providing the second feed to the non-peripheral region.
  • the primary and secondary feed systems may operate independently of one another to control the operation of the ESF.
  • the primary and second feed systems may be coupled together to operate in a concerted manner, to control the operation of the ESF.
  • Control of the feed rates of PFM to each feed port (with either one or more feed ports in each of the peripheral, semi-centre and central regions) in the primary feed system may be controlled by a loss-in-weight through elements such as screw conveyors, rotary valves or slide gates (or combination of such elements - providing both feed control and isolation of the upstream feed bin from the atmosphere within the furnace) which operate to deliver feed either on a batch or continuous basis.
  • the control elements feed PFM from one or more bins with each bin being capable of receiving the same, or a differing, recipe of DRI, iron bearing materials, fluxes and reductants to enable the ESF control strategies described in the embodiments above.
  • feedbanks and open bath are detected by bespoke instruments for direct measurements such as radars, sounding rods and indirect measurements such as thermocouples or other temperature measuring devices inserted into the furnace freeboard, refractory lining, cooling elements or monitoring the differential temperature and flows in the cooling element water circuits.
  • Feedback from the instruments are used to set the control element setpoints to maintain optimal percentage of open bath, feedbank heights, thickness and locations within the furnace to achieve the key goals of the ESF including throughput, energy efficiency, electrical stability, metal chemistry, target slag and metal temperature, help minimize undesirable parasitic reactions such as volatile element fuming and excessive silicon reduction.
  • Control of the feedrates of AM to each feed ports (with one or more present in the central region and potentially others present in the semi-centre or peripheral region) in the secondary feed system is controlled by measurement of the material by a loss-in- weight, weigh feeder or similar instruments and control through final elements such as screw conveyors, rotary valves, double dump valves, vibratory feeders, volumetric feeders or slide gate valves.
  • control elements feed AM from one or more bins, hoppers, skips, bag unloaders or other such material storage equipment being capable, each being able to receive the same I different recipes of iron bearing material including sized scrap, oxide pellets, reverts, refractory scrap, fines, fluxes and reductants to enable the ESF control strategies described in the embodiments above.
  • the feedrates of the various AM materials and the location of their introduction to the ESF can be controlled by feedback from the chemical analysis of off-gas, slag and/or molten iron exhausted or removed by tapping from the furnace to control key goals of the ESF including throughput, energy efficiency, sufficient electrical resistance in the slag bath, metal chemistry, slag chemistry, minimizing undesirable parasitic reactions such as volatile element fuming and excessive silicon reduction.
  • the PFM and AM may be fed using independent feed systems, such as the primary feed system and the secondary feed system, which can be operated in a coordinated or concerted manner to achieve any or a combination of the ESF key goals. This principle may also be repeated at different locations in the application in different ways. While the primary and secondary feed systems are described as feeding the PFM and AM from separate bins or hoppers, in an embodiment, the first and second feed may be provided from the same bin or hopper to the corresponding peripheral region and nonperipheral region of the furnace. In such an embodiment, the first feed and the second feed may have the same, or a similar, composition.
  • Feeding material to the periphery of the furnace may help with establishing and maintaining feedbanks, while feeding material to the open bath area may help with changing the chemistry of the open bath quickly, including by reinstating an upset furnace.
  • materials such as flux may be provided to the open bath to adjust the basicity (B4) and to achieve the select basicity, where B4 is known to be the ratio of (CaO +MgO)/ (AI2O3 +SiO 2 ).
  • B4 may be controlled in order to control the intrinsic resistivity of the slag in the ESF to achieve a select balance of arc to resistive heating at a fixed electrode resistance (impedance).
  • Slag chemistry for example may be further adjusted by providing feed to the open bath to reinstate the targeted viscosity of the slag which may assist in controlling foaming and tapping behaviours.
  • Feeding material into the hotter areas of the open bath may also cause desired reactions to occur, for example to quickly obtain the desired hot metal chemistry and/or impurity distribution.
  • Feed materials may also be provided to the open bath to improve carburization, for example, material added to a hotter zone of the melt reduces or avoids the loss of carbon as a gas as compared to if the materials were instead provided to a feedbank. Feeding material to the open bath area may also significantly increase the smelting I melting rate of the furnace, and thus improving the ESF throughput, or production capacity.
  • the process may also comprise monitoring the DRI-ESF environment to determine whether the feed provided to the open bath and the periphery is controlling and maintaining the desired open bath area and/or desired slag properties.
  • monitoring the furnace environment may comprise monitoring the height, size and/or location of existing and developing feedbanks, and/or the open bath area defined by the solid feed. The height or size of the feedbank may be monitored, for example using a radar or other suitable sensing methods.
  • the furnace environment may also include the conductivity or resistivity of the bath materials including the conductivity or resistivity of the slag. The conductivity or resistivity of the bath materials may be monitored by taking samples and analyzing those samples in a lab. The ESF feed to the periphery and open bath may then be adjusted on the lab results. The adjustments may be made in real time or near real time.
  • a plurality of feeds may be provided to a DRI-ESF.
  • a primary feed may be provided to the periphery of the furnace, for example near the walls of the furnace, and a secondary feed may be provided to an open bath of the furnace, for example near the middle of the furnace at or about the electrodes.
  • the secondary feed and the primary feed may be the same as, or differ from, one another.
  • a greater amount of primary feed by volume or weight
  • the primary feed and the secondary feed may be the same as, or differ from, one another by one or more of feed blend, feed composition, feed temperature, feed rate, feed amount provided at any one time into the ESF.
  • Feed physical properties include morphology, density, mineralogy, particle size.
  • the components making up the feed is referred to herein as the feed blend.
  • the primary feed may be introduced into the furnace at the same rate and/or in the same amount, as the secondary feed, or the two feeds may be provided to the furnace at different rates and/or different amounts and/or different times.
  • the primary feed may be added first, followed by the secondary feed, or vice versa, or the two feeds may be added to the furnace simultaneously.
  • Each of the feeds may be provided to the furnace independently of the other feed.
  • a feed may be provided to the furnace continuously or intermittently.
  • the feed streams introduced into the DRI-ESF may be controlled such as to achieve a desired furnace environment. Controlling the provision of the feed may result in controlling one or more of the chemistry, reactions, and temperature of the ESF.
  • controlling the primary feed and the secondary feed may comprise controlling the blend, composition, temperature, rate, and/or amount of each feed.
  • Control of the blend of each feed may comprise controlling the ratio of different streams such as DRI, reductants, fluxes, etc., while control or selection of the composition of each feed may comprise controlling the chemical composition of each of the streams in the blend.
  • the blend of each feed may be controlled or selected to comprise any one or more of, silicon bearing materials, iron bearing material such as DRI, for example as pellets, fines, or briquettes; reductants such as anthracite, coke, coal, biochar, biomass, etc.; fluxes for example, including lime, dolime, silica, bauxite, etc.; Fe-bearing wastes for example, mill scales, various slags, various fines, skulls; scrap; solid wastes such as refractory debris; and other custom additives, or any other additives.
  • silicon bearing materials iron bearing material such as DRI, for example as pellets, fines, or briquettes
  • reductants such as anthracite, coke, coal, biochar, biomass, etc.
  • fluxes for example, including lime, dolime, silica, bauxite, etc.
  • Fe-bearing wastes for example, mill scales, various slags, various fines, skulls
  • each feed blend may be controlled, for example by controlling the chemical composition of each type of material included in the blend such as controlling the content of Fe containing materials including Fe (metallized), FeO, Fe2O3, Fe3O4, Fe3C, C, Silicon containing materials including SiO2, calcium containing materials including CaO, magnesium containing materials including MgO, aluminum containing materials including AI2O3, sulphur containing materials including S (total), phosphorus containing materials including P (total), sodium containing materials including Na (total), potassium containing materials including K (total), zinc containing materials including Zn (total), titanium containing materials including TiO2, manganese containing materials including MnO, vanadium containing materials including V2O5, chromium containing materials including Cr2O3, Pb containing materials, Ni containing materials, Cu containing materials, Co containing materials, Sn containing materials, H2O (bound), H2O (free), volatiles, etc.
  • Fe containing materials including Fe (metallized), FeO, Fe2O3, Fe3O
  • composition may also be controlled by selecting or controlling certain non-chemical properties such as morphology, density, mineralogy, particle size distribution, etc.
  • the disclosed processes, systems, and methods may comprise having a fully open bath such that there are no feedbanks or periphery structures within the furnace.
  • the periphery, the semi-centre, and the centre of the furnace may all operate in an open bath configuration (see Figure 1C, for example).
  • the first feed may still be provided to the peripheral region of the DRI-ESF, while the second feed may be provided to the non-peripheral region of the DRI-ESF to help control the operation of the DRI-ESF as discussed above.
  • the first feed and the second feed may be provided to the DRI-ESF to help control the operation of the DRI-ESF without utilizing I establishing feedbanks.
  • providing feed to the peripheral region and non-peripheral region may still provide some control over the operation of the DRI-ESF in part because of the difference in the rate of melting in the different regions. Feed may melt faster in the non-peripheral region because the feed in that region would be closer to the electrodes (and thus a higher heat) than feed provided to the peripheral region.
  • the difference in the feed melting rate of the different regions may be utilized to help control the operation of the furnace.
  • feed may be provided to the non-peripheral region to more quickly change the chemistry of the molten material within the bath.
  • feed may be provided to the open bath of the peripheral region to prevent against solid feed forming atop of the layer of slag (due to excessive cooling of the bath as may occur if too much feed is provided to the non-peripheral region).
  • the provision of the first feed and/or the second feed may be controlled by one or more of selecting the feed blend, selecting the feed composition, selecting the feed temperature, selecting an amount of the feed that is provided to the ESF, and selecting a rate at which the feed is provided to the DRI-ESF. Controlling the provision of the first feed and/or the second feed may be in response to a condition of the DRI-ESF being one or more of slag resistivity, metal composition, distribution of impurities, carbon content of the metal, slag composition, and slag temperature.

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  • Organic Chemistry (AREA)
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Abstract

L'invention concerne un processus, un procédé et un four électrique pour produire un métal chaud avec de l'énergie électrique à l'aide de fer préréduit. Le processus et le procédé comprennent la fourniture d'une charge d'alimentation à une région périphérique et à une région non périphérique du four pour commander le fonctionnement du four. La charge d'alimentation peut être fournie et régulée vers chacune de ces régions indépendamment pour commander le fonctionnement du four. Le four peut comprendre un bain liquide partiellement ouvert comprenant une couche de laitier en fusion et une couche de métal en fusion sous la couche de laitier en fusion, et une structure périphérique comprenant du fer préréduit (DRI). La structure périphérique peut s'étendre vers le bas dans le bain liquide.
PCT/CA2025/050386 2024-03-20 2025-03-20 Processus et four électrique de fusion pour produire un métal chaud à partir de fer préréduit Pending WO2025194266A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3443930A (en) * 1966-08-27 1969-05-13 Canada Steel Co Peripheral charging of sponge iron
US3463629A (en) * 1965-09-03 1969-08-26 Gerald Gordon Hatch Manufacturing steel and alloys of iron
WO2023054345A1 (fr) * 2021-09-30 2023-04-06 日本製鉄株式会社 Procédé de production de fer fondu
KR20240028628A (ko) * 2022-08-25 2024-03-05 주식회사 포스코 전기로 설비 및 전기로 조업 방법

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3463629A (en) * 1965-09-03 1969-08-26 Gerald Gordon Hatch Manufacturing steel and alloys of iron
US3443930A (en) * 1966-08-27 1969-05-13 Canada Steel Co Peripheral charging of sponge iron
WO2023054345A1 (fr) * 2021-09-30 2023-04-06 日本製鉄株式会社 Procédé de production de fer fondu
KR20240028628A (ko) * 2022-08-25 2024-03-05 주식회사 포스코 전기로 설비 및 전기로 조업 방법

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