Iron melt from sinter

Abstract

The invention relates to a method for producing an iron melt (80) from iron-oxide-containing material (30), wherein a reduction gas (90) containing at least hydrogen is fed to a reduction reactor (20), containing the iron-oxide-containing material (30), for prereduction. The iron-oxide-containing material (30) comprises at least 35 mass% sinter, and the reduction gas (90) comprises at least 60 vol.% hydrogen H2. Solid, prereduced product obtained in the prereduction step is fed from the reduction reactor (20) into a melting device (40) and is subjected there to a treatment comprising at least the following steps: - introducing energy to generate a melt, said energy being introduced substantially in the form of electricity, and - reducing at least some of the iron oxides contained in the solid prereduced product. The treatment can also include setting a carbon content in the melt. A reduction reactor (20) for prereduction is embodied as a reduction shaft which has a feed region (A) for feeding in the iron-oxide-containing material (30); - a removal region (B) for removing the solid prereduced product obtained in the prereduction step; and - an introduction region (C) for introducing reduction gas (90), wherein the reduction shaft is conical below the introduction region (C), with a wall angle to the vertical of less than 20°, and tapers from the introduction region to the removal region (B). A system for carrying out the method according to the invention comprises: - a reduction reactor (20) for direct reduction of iron-oxide-containing material; - a melting device (60); and - a feed device (50) for feeding solid product obtained by the direct reduction process into the melting device (60).

Description

[0001] Description

[0002] Title of the invention

[0003] Iron melt from sinter

[0004] field of technology

[0005] The application relates to methods and devices for producing an iron melt from iron oxide-containing material which comprises sinter, wherein a reducing gas containing at least hydrogen is used for pre-reduction of the iron oxide-containing material and the product of the pre-reduction is melted.

[0006] State of the art

[0007] It is known to reduce materials containing metal oxides, such as iron oxide, such as lump ores, oxide briquettes, or pellets, using reducing gas. For example, direct reduction with reducing gas in a reduction unit, such as a reduction shaft. In conventional pre-reduction or direct reduction processes currently used on a large industrial scale, the reducing gas is based primarily on carbon—for example, carbon monoxide (CO) and / or methane (CH4)—from natural gas, in addition to hydrogen. Therefore, large quantities of carbon dioxide (CO2) are produced, which is undesirable for environmental reasons, among other things.

[0008] It is also known to reduce iron oxide-containing material, such as sinter, to liquid pig iron via the blast furnace route. This reduction is primarily carried out using carbon-containing gas based on coal or coke, which leads to large emissions of carbon dioxide (CO2) in this production route. Sinter is produced from iron ore-based sinter feed in sintering plants, which are usually located close to blast furnaces. Sintering plants in the iron production industry supply blast furnaces with a material called blast furnace sinter or ironmaking sinter. The manufacturing process for the sinter product in a sintering plant in the iron production industry is well known; see, for example, specialist books such as "Agglomeration of Iron Ores", by D.F. Ball, J. Dartnell, J. Davison, A. Grieve, R.Wild, 1973 edition, 388 pages, page 34, or "Handbook of Agglomeration Technology," Gerald Heinze, 2000 edition, 261 pages, page 102, Wiley-VCH Verlag GmbH, Weinheim, or "Ullmann's Encyclopedia of Industrial Chemistry," 28,029 pages, chapter "Iron," page 15ff, 2006, Wiley-VCH Verlag GmbH, Weinheim. It is based on creating bonds between grains in a mixture of feedstocks containing at least fine iron ores, additives such as crushed lime, dolomite, and quicklime, and fuels such as coke breeze through oxidative roasting combined with surface melting of grains, thereby producing a solid agglomerate as a product.

[0009] To reduce CO2 emissions during the reduction of metal oxide-containing materials, it is known to use hydrogen (H2) as a reducing gas. Hydrogen can be used as the sole reducing gas or in combination with other gases, such as carbon from natural gas or coal or coke. The greater the proportion of hydrogen (H2), which is CO2-neutral with respect to reduction reactions, in the reducing gas, the less CO2 is emitted. Depending on the availability of natural gas or other gases and hydrogen, the ratio of their contribution to the reducing gas can be varied by mixing different amounts.

[0010] The more hydrogen is available, the more climate-problematic contributions based on carbon from natural gas or other gases can be avoided.

[0011] It is advantageous to operate existing plants and processes, in which the reducing gas is based predominantly on carbon and partially on hydrogen from natural gas or other gases, even with increased proportions of hydrogen in the reducing gas. This allows for flexible responses to the availability of natural gas or other gases and hydrogen, and allows the utilization of existing plant investments. At least until sufficient quantities of hydrogen are available for the use of completely hydrogen-based reducing gases, reducing gas will still have to rely on carbon and hydrogen from natural gas or other gases.

[0012] It is also advantageous if, when dispensing with the operation of blast furnaces and switching to other direct or smelting reduction processes in integrated steelworks, existing plants can be used even after the conversion to the reduction process – so that existing investments can continue to be used even after the conversion. Summary of the invention

[0013] Technical task

[0014] It is the object of the present invention to provide methods and devices which allow, away from the blast furnace route, to carry out a pre-reduction starting from a sinter-containing iron oxide-containing material with a hydrogen-rich reducing gas and to provide pig iron-like material.

[0015] Technical solution

[0016] The task is solved by a

[0017] A process for producing an iron melt, preferably with a carbon content of 1-5 mass%, from iron oxide-containing material, wherein a reducing gas containing at least hydrogen, optionally also carbon carriers, is fed to a reduction reactor containing the iron oxide-containing material for pre-reduction, characterized in that the iron oxide-containing material comprises at least 35 mass% sinter, and the reducing gas comprises at least 60 volume% hydrogen H2, and solid pre-reduced product obtained during the pre-reduction is fed from the reduction reactor, optionally via a bunker device, into a melting device, where it is subjected to a treatment comprising at least the following steps:

[0018] - energy supply for producing a melt, whereby the energy supply is essentially electricity,

[0019] - Reduction of at least a portion of the iron oxides contained in the solid pre-reduced product, wherein the treatment optionally also comprises adjustment of the carbon content in the melt.

[0020] The process is blast furnace-free, dispensing with the core component of the conventional blast furnace route—that is, no blast furnace is involved in the reduction of the iron oxide-containing material. The process is operated without a blast furnace. The process therefore takes place outside the conventional blast furnace route. The reduction reactor for pre-reduction is not a blast furnace. Pre-reduction is understood to mean a reduction at the end of which iron oxide is still present in the resulting solid product. The reduction reactor for pre-reduction is a reduction shaft—the reduction using reducing gas takes place in the reduction shaft containing a fixed bed of iron oxide-containing material. Iron oxide-containing material is fed into the top of the reduction shaft and flows through it following gravity, where the reduction reactions take place.

[0021] The reducing gas contains at least 60 vol% hydrogen as a reducing component. It can also consist of hydrogen. Optionally, the reducing gas also contains one or more gaseous carbon carriers as additional reducing components. Carbon carriers are provided, for example, by natural gas; these include carbon monoxide (CO) introduced by or generated from natural gas, or methane (CH4).

[0022] This could be green, blue, grey, turquoise or pink hydrogen, for example. These “colours” refer to the colouring in connection with the underlying production method. Green hydrogen, for example, is produced by electrolysis of water using electricity from renewable energies, or by gasification or fermentation of biomass, or steam reforming of biogas - what all green hydrogen production methods have in common is that it is CO2-free. With blue hydrogen, the CO2 produced during production is stored so that it does not escape into the atmosphere; for example, if it was produced by sequestering the resulting carbon dioxide. With turquoise hydrogen, e is produced by capturing the resulting carbon. With pink hydrogen, hydrogen is produced using nuclear power.Grey hydrogen is produced from fossil fuels - for example from natural gas using steam reforming - with the resulting CO2 being released predominantly into the atmosphere.

[0023] Other colors of hydrogen are also possible.

[0024] A mixture of one or more of these “colors” of hydrogen is also possible.

[0025] If carbon carriers are present as additional reducing components, the following applies: the ratio of hydrogen to carbon carriers in the reducing gas can be varied, for example, by combining different amounts during the preparation of the reducing gas. For example, the ratio can be varied so that the proportion of hydrogen in the reducing gas increases.

[0026] The reducing gas is the gas introduced into the reduction reactor with its composition and temperature at the time of introduction. Before this composition and temperature are achieved, a precursor of the reducing gas is present, on the basis of which the reducing gas is prepared. Preparation may include, for example, the addition of additional components, heating, or reforming. Preparation may also involve chemical reactions occurring in the precursor without external intervention, which, for example, change the chemical composition or temperature. Changes to the preparation may alter the proportion of hydrogen in the reducing gas.

[0027] The molten iron produced according to the invention preferably has a carbon content of 1.0 mass% - 5 mass%. It consists predominantly of iron - it is a liquid, pig iron-like product; the term liquid, pig iron-like product is used in this application synonymously with the term molten iron for the molten iron produced according to the invention. The liquid, pig iron-like product, preferably with a carbon content of 1.0 mass% - 5 mass%, is "similar" to pig iron from a blast furnace from the perspective of a steelmaking process - for example LD / BOF - meaning it can be processed largely in the same way as pig iron from a blast furnace, i.e., with the exception of the blast furnace, following the blast furnace route of steelmaking.The higher the carbon content, the more cooling scrap can be used in subsequent processing into steel; a higher amount of cooling scrap reduces CO2 emissions per unit of steel produced from a liquid, pig iron-like product produced according to the invention.

[0028] Particularly preferably, the carbon content of the liquid, pig iron-like product is at least 2.0 mass%, most preferably at least 2.5 mass%. Particularly preferably, the carbon content of the liquid, pig iron-like product is up to 4.7 mass%, most preferably up to 4.5 mass%.

[0029] According to a preferred embodiment, the solid pre-reduced product obtained during the pre-reduction is added to the melting device via a bunker device. This facilitates dosing of the solid pre-reduced product into the melting device. The energy supply is provided essentially, preferably entirely, by electricity, i.e., electrical energy. Essentially, in this context, means at least 75%, preferably at least 80%. With such an energy supply from electricity, no CO2 is produced, which has a positive effect on the process's carbon footprint.

[0030] According to an advantageous embodiment, the carbon content in the melt is adjusted by means of added carbon carriers.

[0031] These can be solid carbon carriers, liquid carbon carriers, and / or gaseous carbon carriers. The carbon carriers can include, for example, coal dust, coke breeze, graphite dust, or natural gas. The carbon carriers can also come partially or entirely from carbon-neutral sources, for example, from biomass such as charcoal; this improves the carbon footprint of the process. The carbon carriers can be introduced, for example, via lances or underbath nozzles.

[0032] However, it is also possible that the carbon content is not adjusted during treatment because the solid pre-reduced product already contains sufficient carbon.

[0033] According to an advantageous embodiment, the carbon content in the melt is adjusted by adding oxygen. If the carbon content exceeds the desired value for the iron melt, an oxidative reduction of the carbon content can be achieved by adding oxygen. For example, carbon in the melt can react to form CO and escape from the melt in gaseous form.

[0034] According to an advantageous embodiment, the reduction of at least a portion of the iron oxides contained in the solid pre-reduced product is carried out by means of added carbon carriers.

[0035] These can be solid carbon carriers and / or liquid carbon carriers and / or gaseous carbon carriers. The carbon carriers can include, for example, coal dust, coke breeze, graphite dust, or natural gas. The carbon carriers can also originate partially or entirely from carbon-neutral sources, for example, from biomass such as charcoal; this improves the CO2 balance of the process. Advantageous effects of the invention

[0036] The use of hydrogen in the reducing gas allows pre- or direct reduction to be carried out while reducing or avoiding carbon dioxide (CO2) emissions. The higher the hydrogen content in the reducing gas compared to carbon carriers, which produce carbon dioxide (CO2) during pre- or direct reduction, the more carbon dioxide (CO2) emissions can be avoided. This makes ecological sense.

[0037] The use of sinter allows existing investments in sinter plants made for the conventional blast furnace route to be used for a process that does not require blast furnaces. This makes economic and ecological sense.

[0038] The iron oxide-containing material comprises at least 35 mass% sinter. With regard to the definition of sinter, also called blast furnace sinter or iron production sinter, and its production in the iron production industry, reference is made to the above explanations in the introduction to this application. In the context of this application, the term sinter is used primarily, but the terms blast furnace sinter or iron production sinter could also be used. The starting materials for the production of sinter include, for example, fine iron ores or mixtures of fine iron ores with a grain size of, for example, 0.001 - 10 mm, aggregates in the form of, for example, crushed lime, dolomite, quicklime, and optionally also returned materials from the steel production process such as blast furnace dust, mill scale, sinter dust, BOF dust, and as fuels, for example, coke breeze with a grain size of, for example, 0.01 - 10 mm, preferably 0.01 - 10 mm.1-5 mm, particularly preferably 1-3 mm, anthracite, graphite, and biochar are used. The product, the sinter, is a solid, porous, and easily reducible agglomerate with a grain size of, for example, 0.1-75 mm, preferably 3-50 mm, particularly preferably 5-35 mm.

[0039] The use of sinter as a component of the fixed bed feed in a reduction shaft is generally known - see, for example, "Reducing process of sinter in COREX shaft furnace and influence of sinter proportion on reduction properties in composite burden" by Shi Ben-jing et al. in J. Cent. South Univ. (2021) 28: 690 - 698, DOI 10.1007 / s11771-021-4638-5. However, due to decomposition, it is not recommended to allow the sinter content of the feed to rise above 25 - 30 mass%.

[0040] In contrast, the process according to the invention is carried out with a sinter content in the iron oxide-containing material of the feed of at least 35 mass%, preferably at least 50 mass%, particularly preferably more than 50 mass%, and most particularly preferably at least 60 mass%. As the inventors of the present application have discovered, the proposed process with a high hydrogen content in the reducing gas enables stable process control even in the previously discouraged range and allows for significantly better utilization of existing sintering plant infrastructure.

[0041] The rest of the feed can be, for example, iron oxide-containing material from the group

[0042] - Lump ore,

[0043] - oxide briquettes,

[0044] - pellets.

[0045] The use of a primarily electric melting unit allows the production of equivalent steel products with the existing downstream processes, which are not possible with the EAF.

[0046] It is preferred that the pre-reduction be carried out to a metallization of at least 70%, preferably at least 80%, and most preferably at least 85%. The higher the metallization, the lower the need for post-reduction in downstream treatment steps of the solid pre-reduced product obtained during the pre-reduction. The term post-reduction refers to the reduction of at least a portion of the iron oxides still present in the solid pre-reduced product. A reduced need for post-reduction is particularly advantageous if the post-reduction leads to carbon dioxide (CO2) emissions—for example, in the case of post-reduction using carbon from fossil sources.

[0047] However, CO2 emissions can also be reduced if subsequent reduction is carried out using carbon, if the carbon for subsequent reduction comes from biomass.

[0048] The metallization - also called degree of metallization MG - which is given in % results from the ratio of metallic iron Fe met to total iron Fe tot present in a sample according to MG [%] = Fe met / Fe tot * 100.

[0049] Fe met: metallic iron in a sample (mass percentage m%) Fe tot: total iron contained in the sample (mass percentage m%)

[0050] Since the solid product of the pre-reduction—that is, the solid pre-reduced product—still contains iron oxide, its metallization, or its degree of metallization (MG), is below 100%. If the temperature of the iron oxide-containing material fed into the reduction reactor is below the temperature of the reducing gas, it is heated by the reducing gas in the reduction reactor.

[0051] It is preferred to carry out the process at a heating rate of at least 5°C per minute, preferably at least 10°C per minute, and particularly preferably at least 12°C per minute, in the reduction reactor. This minimizes problems arising from exposure to critical temperature ranges for the transition from hematite to magnetite and subsequently to wustite—and thus for compressive strength and bulk pressure.

[0052] The maximum achievable heating rate depends on the physical conditions during heating. The upper limit of the heating rate is 50°C per minute, preferably less than 30°C per minute.

[0053] The temperature of the reducing gas is preferably above 750°C, particularly preferably above 800°C, most preferably above 850°C. The temperature of the reducing gas is preferably below 1050°C, particularly preferably below 1020°C, most preferably below 1000°C.

[0054] For example, if iron oxide-containing material with a temperature of 20°C is fed into the reduction reactor, it should be heated by the reducing gas to a temperature 600°C higher within 60 minutes.

[0055] The particle size of the sinter according to ISO 4701, Third Edition 2008 10 01, is preferably in the range 5 mm - 40 mm, particularly preferably in the range 8 mm - 32 mm, and most preferably in the range 10 mm - 25 mm, whereby the limits of the specified ranges are included with a screening efficiency of up to 5%. Screening efficiency is also referred to as screening efficiency or screening quality.

[0056] It is preferred that the grain stability of the sinter be determined by an RDI test conducted on a sinter sample according to ISO 4696-1, Third Edition 2015-09-01, showing that the proportion of particles smaller than 3.15 mm is less than or equal to 30%. Grain stability is determined using the RDI test according to ISO 4696-1, Third Edition 2015-09-01; RDI stands for reduction degradation index. This type of grain stability can prevent poor gas flow and unstable process control during pre-reduction due to grain disintegration.

[0057] It is preferred if the sinter has a basicity B2 greater than 1. The basicity B2 is preferably up to 2.5, particularly preferably up to 2.2.

[0058] The basicity B2 is given by the ratio of the weight percentages of calcium oxide CaO and silicon dioxide SiO2 in a sample.

[0059] Basicity B2 = CaO / SiO2 (each weight percentage in a sample). This makes the solid pre-reduced product obtained during pre-reduction suitable for use in downstream treatment steps with corresponding basicity requirements; no measures to adjust basicity are required during the downstream treatment steps or during the transfer of the solid pre-reduced product from the reduction reactor to the melting device.

[0060] The slag produced in the melting plant preferably has a basicity B2 which lies in a range of values ​​from 0.9 to 1.2, including the two limit values.

[0061] Slag is produced in the melting device. The slag produced in the melting device preferably has a basicity B4, which lies in a range of 0.8 - 1.2, including the two limit values.

[0062] The basicity B4 is given by the ratio of the sum of the weight percentages of calcium oxide CaO and magnesium oxide MgO to the sum of the weight percentages of silicon dioxide SiO2 and aluminum oxide AI2O3 in a sample.

[0063] Basicity B4 = (CaO + MgO) / (SiO2+AI2O3) (each weight percentage in a sample).

[0064] Preferably, the iron oxide-containing material is introduced into the reduction reactor in an input area largely uniformly over the cross-sectional area of ​​the input area.

[0065] The aim is to achieve an even distribution, but operational-related deviations will still occur during the course of operations, which are largely taken into account by the wording.

[0066] Uniformly across the cross-sectional area is to be understood as the opposite of point-wise at one location or in a limited sub-area of ​​the cross-sectional area; input should therefore not be point-wise at one location or in a limited sub-area of ​​the cross-sectional area, so that an accumulation of material occurs at this location or this limited sub-area, but the input should be largely uniform across the entire cross-sectional area, so that the material level is largely constant everywhere across the cross-sectional area.

[0067] The relevant cross-sectional area is the cross-sectional area perpendicular to the direction of movement of the iron oxide-containing material as it passes through the reduction reactor from an input area for the input of the iron oxide-containing material to a removal area for the removal of the solid pre-reduced product obtained during the pre-reduction.

[0068] A largely uniform feed leads to a largely uniform gassing of the fixed bed and thus a largely uniform reduction in the fixed bed. This helps to avoid local differences in the degree of metallization and in the stability of the particles in the fixed bed. This contributes to the iron oxide-containing material migrating through the reduction reactor largely evenly. The aim is to achieve a uniform migration; however, deviations will still occur during operation due to operational reasons, which are largely uniformly accounted for by the formulation. Local material blockages are thus largely avoided; the aim is to avoid local material blockages entirely; however, local material blockages can still occur during operation due to operational reasons, which are largely avoided and accounted for by the formulation.

[0069] Preferably, the feed is carried out in such a way that segregation of the iron oxide-containing material based on the size and density of its particles is largely avoided and a uniform gas distribution across the cross-section is ensured. The goal is to completely avoid this; however, segregation will still occur during operation due to operational conditions, which is largely evenly addressed by the formulation.

[0070] This can be achieved, for example, by means of a gimbal-mounted distribution chute as shown in WQ2006056350A1, for example as shown in WO2017055419A1.

[0071] The solid pre-reduced product obtained during pre-reduction is removed from the reduction reactor in a removal zone. Preferably, removal occurs across the cross-sectional area of ​​the removal zone, for example, via multiple discharge screws that largely cover the cross-sectional area of ​​the removal zone. "Across the cross-sectional area" is to be understood as the opposite of "point-like" removal at one location or in a limited sub-area of ​​the cross-sectional area. Therefore, removal should not occur at one location or in a limited sub-area of ​​the cross-sectional area, resulting in an increased reduction in the amount of material at this location or in this limited sub-area. Rather, removal should occur largely evenly across the entire cross-sectional area, so that the material level remains largely constant throughout the cross-sectional area.

[0072] Withdrawal across the cross-sectional area of ​​the withdrawal zone contributes to the iron oxide-containing material flowing through the reduction reactor in a largely uniform manner. Local material blockages are thus largely avoided. Largely uniform flow leads to largely uniform gassing of the fixed bed and thus largely uniform reduction in the fixed bed. This contributes to reducing or avoiding local differences in the degree of metallization and in the stability of the particles in the fixed bed. The relevant cross-sectional area is the cross-sectional area perpendicular to the direction of movement of the iron oxide-containing material from an input zone for the input of the iron oxide-containing material to a withdrawal zone for the withdrawal of the solid pre-reduced product obtained during the pre-reduction.

[0073] The reducing gas is introduced into the reduction reactor through an inlet area. Preferably, the reducing gas is introduced into the reduction reactor largely uniformly across the cross-sectional area of ​​the inlet area.

[0074] "Evenly distributed across the cross-sectional area" is the opposite of "distributed at a specific location or in a limited portion of the cross-sectional area." "Largely uniform" in this context means that reducing gas is introduced not only at specific locations or in a limited portion, for example, at the edge of the reduction reactor, but also away from the edge toward the center or in the center of the reduction reactor. This can be achieved, for example, by gas distribution pipes extending into the interior of the reduction reactor or traversing the interior—in the case of a round cross-sectional area, for example, diametrically or as a secant.

[0075] The relevant cross-sectional area is the cross-sectional area perpendicular to the direction of movement of the iron oxide-containing material from an input area for the input of the iron oxide-containing material to a removal area for the removal of the solid product of the direct reduction process.

[0076] A largely uniform introduction across the cross-sectional area leads to largely uniform gas distribution throughout the fixed bed and thus largely uniform reduction within the fixed bed. This helps avoid local variations in the degree of metallization and particle stability of the fixed bed. This contributes to the iron oxide-containing material migrating through the reduction reactor largely evenly. Local material blockages are thus largely avoided.

[0077] The introduction can be realized, for example, as shown in WO2013156548A1.

[0078] According to a preferred embodiment, the solid pre-reduced product obtained during the pre-reduction is fed from the reduction reactor into the melting device via a bunker device, with the bunker device acting as a pressure lock. Thus, a change in the pressure of the atmosphere surrounding the solid product is carried out. This takes place in the bunker device, which can be operated as a pressure lock. This prevents reducing gas from flowing from the reduction reactor into the melting device, or gas from the melting device into the reduction reactor.

[0079] A further subject matter of the present application is a process for producing steel, wherein the production of steel is carried out on the basis of an iron melt produced according to the invention.

[0080] According to an advantageous embodiment, the LD / BOF process is used in the production of steel.

[0081] This is preferably done with a scrap content of at least 10 mass%, preferably at least 15 mass%, particularly preferably at least 20 mass%.

[0082] A further subject matter of the present application is a reduction reactor for pre-reduction of the iron oxide-containing material, which is designed as a reduction shaft, characterized in that the reduction shaft has an input area for input of the iron oxide-containing material; a removal area for removal of the solid pre-reduced product obtained during the pre-reduction, and an inlet area for introducing reducing gas, wherein the reduction shaft is conical below the inlet area with a wall angle to the vertical of less than 20°, preferably less than 10°, wherein it narrows from the inlet area to the removal area.

[0083] With a vertical arrangement of the reduction shaft's longitudinal axis, the input zone is located in the upper section of the reduction shaft, and the output zone is located in the lower section. The discharge zone is located between the input zone and the output zone. Below the discharge zone, the reduction shaft is conical, narrowing toward the output zone; thus, the diameter decreases toward the output zone.

[0084] The conical design with a small wall angle counteracts bridging and thus uneven flow through the reduction shaft. A largely uniform flow is desired, which in the context of bulk materials is also referred to as mass flow. Local material blockages are thus largely avoided. Largely uniform flow leads to largely uniform gassing of the packed bed and thus largely uniform reduction in the packed bed. This helps to avoid local differences in the degree of metallization and in the stability of the particles in the packed bed. It has been shown that the conical design with a small wall angle of the reduction shaft below the inlet area counteracts the occurrence of problems with uniform removal of the solid product.Thus, even with the sintering portion of the iron oxide-containing material and the hydrogen portion of the reducing gas according to the process of the invention, it is possible to achieve a stable process control.

[0085] A process according to the invention can be carried out using such a reduction reactor.

[0086] Preferably, the reduction shaft above the inlet area is largely conical, with a wall angle of less than 3° to the vertical, preferably at least 1° to the vertical; it widens towards the inlet area. In this context, "largely conical" means that, in addition to conical sections, there may also be cylindrical sections. This design counteracts bridging and shaft hangers, thus preventing uneven flow through the reduction shaft. With a vertical arrangement of the longitudinal axis of the reduction shaft, the inlet area is located in the upper area of ​​the reduction shaft, and the removal area in the lower area of ​​the reduction shaft. The inlet area is located between the inlet and removal areas.

[0087] Preferably, the reduction reactor comprises an input device for inputting iron oxide-containing material, which is suitable for largely uniform input over the cross-sectional area of ​​the reduction shaft in the input region.

[0088] For example, the input device includes a gimbal distributor as shown in WQ2006056350A1.

[0089] The relevant cross-sectional area is the cross-sectional area perpendicular to the direction of movement of the iron oxide-containing material as it travels through the reduction shaft from the input area for the input of the iron oxide-containing material to the discharge area for the discharge of the solid product of the direct reduction process. This is also perpendicular to the longitudinal axis of the reduction shaft.

[0090] The input device is preferably suitable for input while largely avoiding segregation of the iron oxide-containing material according to the size and / or density of its particles. The input device preferably comprises a control and / or regulating device which is designed for flexible control and / or regulation of the input. A control device can, for example, automatically use measurement data from thermocouples suitable for determining the gas temperature above the bed in the reduction shaft, and measurement data from thermocouples suitable for determining the gas temperature in the bed in the reduction shaft for control. For example, the operator can specify a distribution profile which is then implemented in a controlled and / or regulated manner.

[0091] Preferably, a discharge device is present in the discharge area, which is suitable for discharging material across the cross-sectional area of ​​the reduction shaft in the discharge area. For example, the discharge device comprises several discharge screws that largely cover the cross-sectional area of ​​the discharge area. The relevant cross-sectional area is the cross-sectional area perpendicular to the direction of movement of the iron oxide-containing material from an input area for the input of the iron oxide-containing material to a discharge area for the discharge of the solid product of the direct reduction process. This is also perpendicular to the longitudinal axis of the reduction shaft.

[0092] Preferably, an introduction device is provided in the introduction area which is suitable for introduction largely uniformly over the cross-sectional area of ​​the reduction shaft in the introduction area.

[0093] For example, the inlet device comprises several inlet pipes that largely cover the cross-sectional area of ​​the extraction area.

[0094] The relevant cross-sectional area is the cross-sectional area perpendicular to the direction of movement of the iron oxide-containing material from an input area for the input of the iron oxide-containing material to a removal area for the removal of the solid product of the direct reduction process. This is also perpendicular to the longitudinal axis of the reduction shaft. The present application further relates to a plant for carrying out the inventive method for producing an iron melt, characterized in that it comprises a reduction reactor for the direct reduction of iron oxide-containing material according to one of claims 12 to 13, a melting device, and a feeding device for feeding solid product of the direct reduction process into the melting device.

[0095] The melting device includes devices for supplying electrical energy.

[0096] According to a preferred embodiment, the adding device comprises a bunker device.

[0097] According to a preferred embodiment, the addition device comprises a bunker device acting as a pressure lock.

[0098] According to a preferred embodiment, the plant for carrying out the method according to the invention also comprises a device for adjusting the carbon content; for example, a device for adding carbon-containing material to the melting device, or a device for adding oxygen to the melting device. A device for adjusting the carbon content thus acts, for example, by adding carbon-containing material to the melting device and / or reducing carbon-containing material present in the melting device—for example, in the solid product fed into the melting device and / or in the molten iron. The reduction can be achieved, for example, by reaction with oxygen; resulting gases can be extracted from the molten iron or the melting device.

[0099] A device for adding additives to the melting device may also be present. Additives are added, for example, to achieve a desired basicity of the slag produced in the melting device. A further subject matter of the present application is a signal processing device with a machine-readable program code, characterized in that it has control and / or regulating commands for carrying out a method according to the invention. A further subject matter is a signal processing device for carrying out a method according to one of claims 1 to 11.

[0100] A further subject matter of the present application is a machine-readable program code for a signal processing device, characterized in that the program code comprises control and / or regulating commands that cause the signal processing device to carry out a method according to the invention. A further subject matter is a computer program product comprising commands for a signal processing device that, upon execution of the program for the signal processing device, cause the signal processing device to carry out the method according to one of claims 1 to 11.

[0101] A further subject matter of the present application is a storage medium having a machine-readable program code according to the invention stored thereon. A further subject matter is a storage medium having a computer program stored thereon for carrying out a method according to one of claims 1 to 11.

[0102] Short description of the drawings

[0103] The present invention is described below by way of example with reference to several schematic figures.

[0104] Figure 1 shows schematically a system according to the invention.

[0105] Figure 2 shows schematically a reduction reactor according to the invention for pre-reduction.

[0106] Description of the embodiments

[0107] Examples Figure 1 shows a schematic representation of a plant 10 comprising a reduction reactor 20 for the direct reduction of iron oxide-containing material 30, a melting device 40 and an addition device 50 for feeding solid product produced in the reduction reactor 20 into the melting device 40. Optional and therefore shown in dashed lines is a bunker device 60 comprising the addition device 50 and acting as a pressure lock. Also optional and therefore shown schematically in dashed lines is a device for adjusting the carbon content 70 - which can be, for example, a device for adding carbon-containing material to the melting device 40, or a device for adding oxygen to the melting device 40.

[0108] To produce the iron melt 80 from the iron oxide-containing material 30, which comprises, for example, more than 50 mass % sinter, a reducing gas 90 containing more than 60 volume % hydrogen H2 is fed to the reduction reactor 20 containing the iron oxide-containing material 30 for pre-reduction. The particle size of the sinter is, for example, in the range 8 mm - 32 mm. Its basicity B2 is preferably greater than 1.

[0109] If the temperature of the iron oxide-containing material 30 fed into the reduction reactor 20 is below the temperature of the reducing gas 90, it is heated in the reduction reactor 20 by the reducing gas 90; a heating rate of, for example, 10°C per minute is favorable.

[0110] The solid pre-reduced product obtained during the pre-reduction in the reduction reactor 10 still contains iron oxides. It is preferably metallized to at least 70%. It is fed from the reduction reactor 20, optionally via the optional bunker device 60, to the melting device 40. There, the iron melt, preferably with a carbon content of 1-5 mass%, is produced from it. The treatment for producing the iron melt 80 comprises at least the supply of energy to generate a melt and the reduction of at least a portion of the iron oxides contained in the solid pre-reduced product. Optionally, it also comprises adjusting the carbon content in the melt using the optional carbon content adjustment device 70.

[0111] The energy supply comes mainly from electricity.

[0112] During treatment in the melting device 40, a slag 100 is produced, the basicity B2 of which is preferably between 0.9 and 1.2. For reasons of clarity, an optional addition device for adding additives to the melting device 40 is not shown.

[0113] Figure 2 shows a schematic enlarged view of the reduction reactor 20 for the pre-reduction of the iron oxide-containing material 30. It is designed as a reduction shaft, having an input area A for the input of the iron oxide-containing material 30, a removal area B for the removal of the solid pre-reduced product obtained during the pre-reduction, and an introduction area C for the introduction of reducing gas 90. The reduction shaft 20 is conical below the introduction area C. Its wall angle to the vertical is less than 20°, and it narrows from the introduction area C to the removal area B.

[0114] In the illustrated embodiment, the reduction shaft above the inlet area is conical with a wall angle of between 1° and 3° to the vertical - not exaggerated to scale here.

[0115] List of citations

[0116] Patent literature

[0117] W02006056350A1

[0118] WO2017055419A1

[0119] WO2013156548A1

[0120] Non-patent literature

[0121] “Reducing process of sinter in COREX shaft furnace and influence of sinter proportion on reduction properties in composite load,” Shi Ben-jing et al. in J. cents. South University

[0122] (2021) 28: 690 - 698, DOI 10.1007 / s11771-021-4638-5

[0123] ISO4701 Third edition 2008 10 01

[0124] ISO 4696-1 Third edition 2015-09-01

[0125] “Agglomeration of Iron Ores”, DF Ball, J. Dartnell, J. Davison, A. Grieve, R. Wild, 1973 edition, 388 pages, page 34

[0126] “Handbook of Agglomeration Technology”, Gerald Heinze, 2000 edition, 261 pages, page 102, Wiley-VCH Verlag GmbH, Weinheim

[0127] “Ullmann's Encyclopedia of Industrial Chemistry”, 28029 pages, chapter “Iron” page 15ff, 2006 Wiley-VCH Verlag GmbH, Weinheim.

[0128] List of reference symbols

[0129] 10 Appendix

[0130] 20 Reduction reactor

[0131] 30 iron oxide-containing material

[0132] 40 melting device

[0133] 50 Adding device

[0134] 60 bunker device

[0135] 70 Device for adjusting the carbon content

[0136] 80 Iron smelter

[0137] 90 Reducing gas

[0138] 100 slag

[0139] A input area

[0140] B Withdrawal area

[0141] C Introduction area

Claims

Claims 1. A method for producing an iron melt (80), preferably with a carbon content of 1 - 5 mass%, from iron oxide-containing material (30), wherein a reducing gas (90) containing at least hydrogen, optionally also carbon carrier, is fed to a reduction reactor (20) containing the iron oxide-containing material (30) for pre-reduction, characterized in that the iron oxide-containing material (30) comprises at least 35 mass% sinter, and the reducing gas (90) comprises at least 60 volume% hydrogen H2, and solid pre-reduced product obtained in the pre-reduction from the reduction reactor (20), optionally via a bunker device (60), into a melting device (40), and is there subjected to a treatment comprising at least the following steps: - energy supply for producing a melt, whereby the energy supply is essentially electricity, - Reduction of at least a portion of the iron oxides contained in the solid pre-reduced product, wherein the treatment optionally also comprises adjustment of the carbon content in the melt.

2. Method according to claim 1, characterized in that the pre-reduction is carried out at least up to a metallization of 70%, preferably at least 80%, most preferably at least 85%.

3. The method according to claim 1 or 2, characterized in that it is carried out at a heating rate of at least 5°C per minute, preferably at least 10°C per minute, particularly preferably at least 12°C per minute, in the reduction reactor (20).

4. Method according to one of the preceding claims, characterized in that the particle size of the sinter is in the range 5 mm - 40 mm, particularly preferably in the range 8 mm - 32 mm, very particularly preferably in the range 10 mm - 25 mm, wherein the limits of the range specifications are included with a sieving efficiency according to ISO4701 version from 2008 of up to 5%.

5. Method according to one of the preceding claims, characterized in that for the grain stability of the sinter, the result of an RDI test carried out on a sample of the sinter according to ISO 4696-1 Third edition 2015-09-01 shows that the proportion of particles whose particle size is less than 3.15 mm is less than or equal to 30%.

6. Process according to one of the preceding claims, characterized in that the sinter has a basicity B2 greater than 1.

7. Method according to one of the preceding claims, wherein the iron oxide-containing material (30) is introduced into the reduction reactor (20) in an input region, characterized in that it is introduced largely uniformly over the cross-sectional area of ​​the input region.

8. Method according to one of the preceding claims, wherein the solid pre-reduced product obtained in the pre-reduction is removed from the reduction reactor (20) in a removal area, characterized in that it is removed flatly over the cross-sectional area of ​​the removal area.

9. Method according to one of the preceding claims, wherein the reducing gas (90) is introduced into the reduction reactor (20) in an introduction region, characterized in that it is introduced largely uniformly over the cross-sectional area of ​​the introduction region.

10. Method according to one of the preceding claims, characterized in that the solid pre-reduced product obtained in the pre-reduction is added from the reduction reactor (20) via a bunker device (60) into the melting device (40), wherein the bunker device (60) acts as a pressure lock.

11. A method for producing steel, wherein the production of steel is carried out on the basis of an iron melt (80) produced according to one of claims 1-10.

12. Reduction reactor (20) for the pre-reduction of iron oxide-containing material comprising at least 35 mass% sinter, which is designed as a reduction shaft, characterized in that the reduction shaft has an input region (A) for the input of the iron oxide-containing material (30); a removal region (B) for removing the solid pre-reduced product obtained during the pre-reduction, and an inlet region (C) for the introduction of reducing gas (90), wherein the reduction shaft is conical below the inlet region (C) with a wall angle to the vertical of less than 20°, preferably less than 10°, wherein it narrows from the inlet region to the removal region (B).

13. Reduction reactor (20) according to claim 12, characterized in that the reduction shaft above the introduction region (C) is largely conical, with a wall angle of less than 3° to the vertical, preferably at least 1° to the vertical, and it widens towards the introduction region (C).

14. Plant for carrying out the method according to the invention for producing an iron melt (80), characterized in that it comprises a reduction reactor (20) for the direct reduction of iron oxide-containing material (30) according to one of claims 12 to 13, a melting device (60), an addition device (50) for introducing solid product of the direct reduction method into the melting device (60).

15. Plant according to claim 14, characterized in that it comprises a device for adjusting the carbon content (70).

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