Iron source manufacturing method

Abstract

To provide a method for producing an iron source capable of sufficiently removing phosphorus even when phosphorus existing in iron ore is bonded to iron.SOLUTION: A method for producing an iron source comprises: a preparation step of preparing a composition for roasting containing iron ore having 0.05 mass% or more of phosphorus, where the total amount of Al2O3 and SiO2 is 5.0 mass% or more when the elements contained in the composition for roasting are converted into oxides; a roasting step of obtaining a roasted product by roasting the composition for roasting; a reduction step of obtaining a reduced product containing a reduced iron phase and a slag phase by reducing the roasted product in an atmosphere containing at least one of CO gas and hydrogen gas; a grinding step of obtaining a pulverized product containing a reduced iron phase-containing product in which at least a part of the slag phase constituting the reduced product is separated by pulverizing the reduced product; and a sorting and recovering step of sorting and recovering the reduced iron phase-containing product from the pulverized product.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing an iron source, and more particularly to a method for producing an iron source having a reduced phosphorus content compared to raw iron ore. [Background technology]

[0002] In recent years, with the depletion of high-quality iron sources, it has become increasingly difficult to obtain iron ore with few impurities such as gangue as a raw material for steel products, and the impurity content of iron ore is expected to increase in the future. Patent Document 1, for example, describes a pre-treatment method for converting low-grade iron ore containing a large amount of gangue into high-grade iron ore for direct ironmaking, in which iron ore charged into a reduction furnace is reduced with reducing gas generated from a hydrocarbon-containing fuel to directly obtain a raw material for ironmaking without going through a pig iron production process. The method includes the steps of: introducing high-temperature furnace gas discharged from the reduction furnace into a reduction roasting furnace and reducing and roasting hematite ore supplied from a storage yard with reducing components remaining in the furnace gas to produce magnetite ore; crushing the magnetite ore to a particle size suitable for magnetic separation and magnetically separating it using a magnetic separator; and agglomerating and firing the magnetite concentrate obtained by magnetic separation to form pellets, which are then fed to the reduction furnace.

[0003] Phosphorus is one of the components that reduces the quality of iron ore. In the existing blast furnace-converter process, almost all of the phosphorus in iron ore is transferred to the molten iron in the blast furnace, and is generally removed in the subsequent molten iron pretreatment and converter processes. However, as the amount of phosphorus in the raw iron ore increases, the cost of phosphorus removal in these processes increases and productivity decreases. Therefore, there is a need to develop a technology to remove phosphorus from iron ore used in steelmaking.

[0004] For example, Patent Document 2 describes a method for removing phosphorus from iron ore by wet processing. Specifically, the method describes a phosphorus-containing iron ore treatment process in which high-phosphorus iron ore is crushed to 0.5 mm or less, water is added to the crushed ore to a pulp concentration of approximately 35%, H2SO4 or HCl is added as a solvent, and the resulting mixture is reacted at a pH of 2.0 or less to decompose and dissolve the contained phosphorus minerals (mainly apatite). Magnetic separation is then performed to collect magnetized materials such as magnetite, and non-magnetic materials such as SiO2 or Al2O3 are separated and separated as slime. Furthermore, the phosphorus dissolved in the solution is neutralized by adding slaked lime or quicklime at a pH of 5.0 to 10.0, and separated and recovered as calcium phosphate. However, the method described in Patent Document 2 has the drawback of being difficult to ensure productivity due to its wet processing.

[0005] Meanwhile, methods for removing phosphorus from iron ore using dry processes have also been proposed. For example, Non-Patent Document 1 proposes a process for separating phosphorus from iron ore by concentrating it in a dicalcium silicate (C2S) phase. Specifically, the basicity of the iron ore and the blending ratio of the carbonaceous material are adjusted, particularly with regard to the basicity, by adding an amount of CaO based on the SiO2 contained in the fine ore so that the basicity (C / S) becomes 2.0, and then heating at a high temperature. This results in the coexistence of a dicalcium silicate phase (2CaO-SiO2, C2S) as a solid phase in the molten slag, and P is concentrated as a solid solution (C2S-C3P solid solution) with a calcium phosphate phase (3CaO-P2O5, C3P). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 53-103915 [Patent Document 2] Japanese Patent Application Publication No. 60-261501 [Non-patent literature]

[0007] [Non-Patent Document 1] Nobuhiro Maruoka et al., "Enrichment of phosphorus in iron ore into the dicalcium silicate phase by partial reduction treatment," Iron and Steel, Vol. 107 (2021), No. 6, pp. 527-533 Summary of the Invention [Problem to be solved by the invention]

[0008] The method of Patent Document 1 is effective when phosphorus is bound to elements other than iron, but has the problem that it cannot remove phosphorus when bound to iron. Furthermore, the method of Non-Patent Document 1 has the problem that it is difficult to adjust the oxygen partial pressure due to the use of carbonaceous materials, etc., which makes it easy for phosphorus to be mixed into the iron phase, making it difficult to remove phosphorus. In addition, the use of carbonaceous materials causes problems such as the inclusion of sulfur and the emission of greenhouse gases.

[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to realize a method for producing an iron source to be used in iron production or the like, which can sufficiently remove phosphorus even when the phosphorus present in iron ore is bound to iron. [Means for solving the problem]

[0010] Aspect 1 of the present invention is A roasting composition comprising iron ore containing 0.05% by mass or more of phosphorus, a preparation step of preparing a composition for roasting, in which the total amount of Al2O3 and SiO2 is 5.0 mass% or more when elements contained in the composition for roasting are converted into oxides; a roasting step of roasting the composition for roasting to obtain a roasted product; a reduction step of reducing the roasted product in an atmosphere containing at least one of CO gas and hydrogen gas to obtain a reduced product containing a reduced iron phase and a slag phase; a pulverization step of pulverizing the reduced material to obtain a pulverized material containing a reduced iron phase from which at least a portion of the slag phase constituting the reduced material has been separated; a sorting and recovery step of sorting and recovering the reduced iron phase-containing material from the pulverized material; A method for producing an iron source, comprising:

[0011] Aspect 2 of the present invention is The method for producing an iron source according to aspect 1, wherein the roasting composition comprises the iron ore.

[0012] Aspect 3 of the present invention is The roasting composition includes the iron ore and a flux.

[0013] A fourth aspect of the present invention is Aspect 4. The method for producing an iron source according to aspect 3, wherein the flux comprises one or more of Al2O3 and SiO2.

[0014] A fifth aspect of the present invention is Aspect 5 is a method for producing an iron source according to any one of aspects 1 to 4, wherein magnetic separation is performed as a method for separating and recovering the iron in the separating and recovering step.

[0015] A sixth aspect of the present invention is Aspects 6. The method for producing an iron source according to any one of Aspects 1 to 5, wherein the composition for roasting has a basicity CaO / SiO2 of less than 1.0. [Effects of the Invention]

[0016] According to the present disclosure, it is possible to provide a method for producing an iron source to be used in iron production or the like, which can sufficiently remove phosphorus even when phosphorus present in iron ore is bound to iron. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is an image diagram that schematically shows each step of the manufacturing method according to this embodiment. [Figure 2] FIG. 2 is an image diagram that schematically shows each of the other steps of the manufacturing method according to this embodiment. [Figure 3] FIG. 3 is a graph showing the phosphorus removal rate of various roasting compositions in the examples. [Figure 4] FIG. 4 is another graph showing the phosphorus removal rate of various roasting compositions in the examples. [Figure 5]FIG. 5 is a scanning electron microscope image of the sample of the example before pulverization. [Figure 6] FIG. 6 is a diagram showing EDX analysis values ​​at analysis points 1 and 2 in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] The method for producing an iron source according to this embodiment includes the steps of: A roasting composition comprising iron ore containing 0.05% by mass or more of phosphorus, a preparation step of preparing a composition for roasting, in which the total amount of Al2O3 and SiO2 is 5.0 mass% or more when elements contained in the composition for roasting are converted into oxides; a roasting step of roasting the composition for roasting to obtain a roasted product; a reduction step of reducing the roasted product in an atmosphere containing at least one of CO gas and hydrogen gas to obtain a reduced product containing a reduced iron phase and a slag phase; a pulverization step of pulverizing the reduced material to obtain a pulverized material containing a reduced iron phase from which at least a portion of the slag phase constituting the reduced material has been separated; and a sorting and recovery step of sorting and recovering the material containing the reduced iron phase from the pulverized material.

[0019] According to this embodiment, the production method involves a roasting step in which a roasting composition containing iron ore with a certain amount of phosphorus and a certain amount of alumina (Al2O3) and silica (SiO2) in total is roasted, and a reduction step in which the roasted product obtained by the roasting is reduced in an atmosphere containing at least one of CO gas and hydrogen gas. As a result, phosphorus bound to iron in the iron ore is transferred to a slag phase (components other than iron, impurities) formed by roasting the composition (oxidizing roasting) and bound to the slag. The reduction step then allows the reduction of iron oxide while keeping the phosphorus bound to the slag, achieving chemical separation of the phosphorus and the iron phase. Subsequent crushing and sorting yields a reduced iron phase-containing material as an iron source. In this embodiment, as shown by the EDX analysis results in the examples described below, it is believed that phosphorus can be sufficiently removed from the iron ore by binding the phosphorus to the slag and capturing the phosphorus as a composite oxide of phosphorus oxide, alumina, and silica.

[0020] The roasting composition containing a certain amount of alumina (Al2O3) and silica (SiO2) in total, together with the iron ore, can be formed from the iron ore itself or from the iron ore and a flux. When the roasting composition is formed from the iron ore, the iron ore itself contains a certain amount of alumina (Al2O3) and silica (SiO2) in total. FIG. 1 is a schematic diagram illustrating each step of a production method according to this embodiment when the roasting composition is formed from the iron ore. FIG. 2 is a schematic diagram illustrating each step of a production method according to this embodiment when the roasting composition contains iron ore and a flux. The following description of each step may be based on FIGS. 1 and 2, but these are merely schematic diagrams and do not limit this embodiment. For example, there may be cases where phosphorus does not completely migrate to the slag phase side by roasting, or where the slag phase and the reduced iron phase do not completely separate from each other by pulverization, with part of the slag phase remaining bound to the reduced iron phase. However, such situations are naturally acceptable, and the production method according to this embodiment may also include these situations.

[0021] [Preparation process] A roasting composition is prepared, which includes iron ore containing 0.05% by mass or more of phosphorus, and in which the total amount of Al2O3 and SiO2 is 5.0% by mass or more when the elements contained in the roasting composition are converted into oxides. The total amount of Al2O3 and SiO2 is preferably 8% by mass or more, more preferably 10% by mass or more, and the upper limit of the total amount of Al2O3 and SiO2 is approximately 40% by mass, preferably 30% by mass, and more preferably 20% by mass.

[0022] The total amount of Al2O3 and SiO2 is not particularly limited as long as it falls within the above range. The Al2O3 content of the roasting composition is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, even more preferably 1.5% by mass or more, still more preferably 2.0% by mass or more, and most preferably 3.0% by mass or more. From the viewpoint of productivity, the Al2O3 content is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less.

[0023] The SiO content of the roasting composition is preferably 1.0% by mass or more, more preferably 1.5% by mass or more, even more preferably 2.0% by mass or more, still more preferably 2.5% by mass or more, and most preferably 5.0% by mass or more. From the viewpoint of productivity, the SiO content is preferably 40% by mass or less, more preferably 30% by mass or less, and more preferably 20% by mass or less.

[0024] Oxides such as Al2O3 and SiO2 are produced as impurities during the mining of iron ore, but have no practical uses and are treated as industrial waste. In other words, these oxides, such as Al2O3 and SiO2, are produced in large quantities and do not require any additional costs or energy beyond that required for the mining of iron ore. Therefore, when the iron source according to the present embodiment is produced near a mining site, for example, a transportation step can be omitted. Furthermore, the oxides, such as Al2O3, do not generate CO2 due to thermal decomposition when heated. Therefore, if phosphorus can be removed from iron ore using Al2O3 or the like, this method would be advantageous in terms of both cost and environmental impact compared to the phosphorus removal method using limestone, which will be described later.

[0025] The roasting composition includes iron ore containing 0.05% by mass or more of phosphorus. According to this embodiment, phosphorus can be sufficiently reduced even when the amount of phosphorus in the iron ore is as high as 0.10% by mass or more, or even 0.15% by mass or more. The iron ore may be crushed, classified, or otherwise processed to achieve uniform size before roasting or before mixing with the flux. The iron ore may contain one or more of alumina (Al2O3) and silica (SiO2) in the above amounts, in addition to the above amount of phosphorus. In this specification, "iron ore" refers to iron ore containing impurities such as SiO2 along with Fe oxides such as Fe2O3 and Fe3O4. Meanwhile, "iron oxide" in this specification refers only to Fe oxide phases such as Fe2O3 and Fe3O4.

[0026] When iron ore itself contains a certain amount of alumina (Al2O3) and silica (SiO2), the iron ore 11 alone can be used as the roasting composition, as shown in Figure 1A. Even without the addition of CaO-based oxides, which are known to bind phosphorus easily, the presence of impurity phase 12B, primarily composed of silicon and aluminum oxides, in addition to the iron oxide-containing phase 12A in the iron ore, can achieve phosphorus removal effects equivalent to or even greater than those achieved by adding CaO-based oxides as a flux. This is thought to be because the resulting Al2O3-SiO2-P2O5 slag has a phosphorus-immobilizing effect similar to the 2CaO·SiO2-3CaO·P2O5 solid solution formed when CaO-based oxides are used as a flux.

[0027] Alternatively, the roasting composition may contain iron ore 21 and flux 22, as shown in FIG. 2A. When the roasting composition contains iron ore 21 and flux 22, the Al2O3 content specified above is the sum of the Al2O3 content in the iron ore and the Al2O3 content in the flux. The flux preferably contains one or more of alumina (Al2O3) and silica (SiO2), more preferably a flux with reduced Ca compound content. That is, even if a flux containing silicon or aluminum is used instead of a CaO-based oxide, which is known to easily bind with phosphorus, a phosphorus removal effect equivalent to or greater than that achieved when a CaO-based oxide is used can be achieved. This is thought to be due to the phosphorus-immobilizing effect of the resulting Al2O3-SiO2-P2O5-based slag, as described above. As shown in the examples below, the phosphorus removal rate can be further increased by using a flux containing silicon or aluminum. Therefore, from the viewpoint of increasing the phosphorus removal rate, when a flux is used, the flux preferably contains one or more of alumina (Al2O3) and silica (SiO2), and more preferably contains both alumina (Al2O3) and silica (SiO2).

[0028] According to this embodiment, the addition of CaO, which has been conventionally used, can be reduced. While limestone (main component: CaCO3) is generally inexpensive as a CaO source, it is considered to avoid using limestone to further reduce production costs. Furthermore, the energy required for mining / transporting and heating limestone, as well as the thermal decomposition of limestone (CaCO3 → CaO + CO2), all lead to increased CO2 emissions. Therefore, if a phosphorus removal technology that does not involve the addition of CaO could be realized, it would be possible to achieve a cheaper, more environmentally friendly process that reduces CO2 emissions. Furthermore, if iron ore dephosphorization could be achieved without the essential requirement of CaO, the process options could be expanded. From this perspective, it is preferable that the flux does not contain one or more elements selected from the group consisting of CaO, CaCO3, and Ca(OH)2, or that the content of these elements is minimized. For example, it is preferable that the flux has a basicity of less than 1.0 when the Ca compounds are converted to CaO. The flux size may be any size commonly used in industry.

[0029] The roasting composition of this embodiment may contain compounds other than the above-mentioned Al2O3, SiO2, and CaO, such as oxides, carbonates, hydroxides, hydrates, fluorides, and chlorides, as impurities or fluxes contained in iron ore. However, like the CaO, the content of these compounds is preferably minimized. In particular, carbonates are not preferred because, like the CaCO3, they are thought to decompose upon heating and generate CO2. Furthermore, like the CaO production, from the viewpoint of reducing the costs required for flux preparation, such as mining and transportation, it is also preferable to minimize the content of these compounds, like the CaO. The total content of the above compounds and Ca compounds, such as CaO, CaCO3, and Ca(OH)2, contained in the roasting composition is preferably less than 1% by mass.

[0030] When a flux is used together with the iron ore, the iron ore and the flux can be mixed by an industrially used method. If necessary, a medium such as water may be further added to the iron ore and the flux to form a granule.

[0031] [Roasting process] In the roasting step, the roasting composition is roasted to obtain a roasted product as shown in FIG. 1B or FIG. 2B. In the roasting step indicated by arrow a from A to B in FIG. 1, iron ore 11 containing phosphorus bound to iron is roasted alone (oxidizing roasting). This melts impurities, such as SiO2 and Al2O3, typically present in iron ore at a few percent. As shown in FIG. 1B, this melting melts into a roasted slag phase 14 (an impurity phase mainly composed of components other than iron), such as an Al2O3-SiO2-P2O5-based slag phase, and an iron oxide-containing phase 13. In other words, even without adding a CaO-based oxide flux, which is known to easily bind with phosphorus, the roasted slag phase 14 and the iron oxide-containing phase 13 can be separated as described above, resulting in the removal of phosphorus from the iron ore.

[0032] Alternatively, in the roasting process indicated by arrow a from A to B in Figure 2, iron ore 21 containing phosphorus bound to iron is roasted together with flux 22 (oxidizing roasting). As shown in B in Figure 2, phosphorus migrates 25, specifically, phosphorus in iron ore 21 migrates to and bonds with roasted slag phase 24 formed by the roasting of the flux. It is believed that an Al2O3-SiO2-P2O5-based slag phase can be formed as the roasted slag phase 14, 24. Therefore, phosphorus can be sufficiently removed without adding CaO-based oxides as a flux, which are known to easily bind with phosphorus.

[0033] To achieve the effects shown in FIG. 1 or 2, the roasting temperature is preferably 1150°C or higher, at which at least a portion of the roasting composition can melt. The temperature may further be 1200°C or higher. The upper limit of the roasting temperature is not particularly limited from the viewpoint of transferring phosphorus from the iron ore to the slag phase. For example, from the viewpoint of preventing deterioration of equipment, the upper limit of the temperature may be set to about 1500°C. The roasting temperature refers to the temperature in the region where the roasting composition is packed, and in the examples described below, this temperature was controlled by the ambient temperature of the furnace used.

[0034] In this embodiment, the roasting atmosphere refers to an atmosphere in which the reduction rate of iron oxide due to roasting (hereinafter referred to as the "iron reduction rate") is 10% or less. In this embodiment, the reduction of iron oxide is suppressed during the roasting stage, the roasting process is separated from the reduction process, and the iron oxide is reduced in the reduction process. This separates phosphorus from the iron phase contained in or derived from the iron ore (hereinafter simply referred to as the "iron phase") and prevents the incorporation of phosphorus into the iron phase. The reduction rate is preferably 8% or less, more preferably 5% or less, and may even be 0%. The aforementioned methods for achieving the reduction rate include controlling the atmosphere and temperature.

[0035] The atmosphere may be an oxygen-containing atmosphere. For example, the atmosphere may be air. In the roasting step, for example, a carbonaceous material may be used as a heat source. When this carbonaceous material is used, the atmosphere may be slightly more reducing than air, and such an atmosphere is also acceptable. As equipment for roasting, for example, an electric resistance furnace (externally heated), a burner-type heating furnace, a Dwight Lloyd sintering machine, a pot-type sintering machine, etc. may be used.

[0036] [Reduction process] In the reduction step, the roasted product is reduced in an atmosphere containing at least one of CO gas and hydrogen gas to obtain the reduced product shown in C of FIG. 1 or C of FIG. 2, i.e., a reduced product containing reduced iron phases 16, 26 and slag phases 17, 27. The reduction step, indicated by arrow b from B to C in FIG. 1 or 2, provides a reduced product composed of reduced iron phases 16, 26 obtained by reducing iron oxide-containing phases 13, 23, and reduced slag phases 17, 27 in which phosphorus remains fixed (the slag phases after the roasted slag phases 14, 24 have undergone this reduction step). The reasons why phosphorus can be easily chemically separated by separating the roasting step and the reduction step and performing reduction in the above atmosphere in the reduction step in this embodiment are described in detail below.

[0037] When the oxygen partial pressure drops during reduction, oxygen dissociates from P2O5 in the slag, generating phosphorus. This phosphorus easily binds with Fe, making it difficult to remove from the iron ore. Therefore, it is necessary to suppress fluctuations in the oxygen partial pressure during reduction. However, the method of Non-Patent Document 1 is thought to be prone to fluctuations in the oxygen partial pressure during reduction. This is because the method of Non-Patent Document 1 uses a carbonaceous material, which can locally decrease the oxygen partial pressure around the carbonaceous material during reduction, and heating the carbonaceous material can produce CO gas and CO2 gas, resulting in unpredictable oxygen consumption. On the other hand, this embodiment uses a gaseous reducing agent, such as CO gas or hydrogen gas, for reduction. This suppresses fluctuations in the oxygen partial pressure during reduction, preventing phosphorus from binding with iron due to a reduced oxygen partial pressure, and is thought to result in maintaining the phosphorus in a chemically separated state.

[0038] The gas constituting the atmosphere in the reduction step needs only to contain at least one of CO gas and hydrogen gas, and the remaining gas components are not particularly limited. Since the purpose is reduction, it is preferable that the remaining gas components are gases that do not have an oxidizing effect. Examples of the remaining gas components include CO2 gas and N2 gas. In the examples described below, a mixed gas of CO gas and hydrogen gas is used as the reducing gas, but the reducing gas may be hydrogen gas only, for example, 10% hydrogen gas with the remainder being N2 gas. According to this embodiment, when hydrogen is used as the reducing gas, it contributes to a reduction in greenhouse gases compared to when a carbonaceous material is used as a reducing agent as in Non-Patent Document 1.

[0039] By carrying out reduction under the above conditions, the migration of SiO2 and Al2O3 to the reduced slag phases 17, 27 proceeds, and the reduction of the iron oxide-containing phases 13, 23 proceeds with most of the phosphorus fixed in the reduced slag phases 17, 27, resulting in reduced iron phases 16, 26 mainly composed of, for example, M.Fe (metallic iron) or Fe3O4. In other words, the above oxidizing roasting and reduction processes produce a reduction product in which the phosphorus fixed in the reduced slag phases 17, 27 and the reduced iron phases 16, 26 are sufficiently chemically separated.

[0040] In this embodiment, the reduced iron phase may contain not only M.Fe (metallic iron) but also FeO and FeO obtained by reducing FeO. The reduced iron phase may also contain impurities such as oxides of elements other than iron.

[0041] The atmospheric temperature in the reduction step can be, for example, in the range of 600°C or higher and 900°C or lower. The atmospheric temperature in the reduction step refers to the atmospheric temperature in a furnace used for reduction. Preferably, the atmospheric temperature in the reduction step is 850°C or lower. From the viewpoint of promoting reduction, the lower limit of the atmospheric temperature in the reduction step is preferably 650°C or higher.

[0042] The reduction time can be appropriately determined depending on the amount of material to be processed. After the reduction at the above-mentioned ambient temperature is completed, the cooling to room temperature can be performed in a non-oxidizing atmosphere, and is not limited to a reducing gas atmosphere. For example, an inert gas atmosphere such as N2 gas or Ar can be used.

[0043] [Crushing process] In the pulverization process, the reduced material is pulverized to obtain a pulverized material containing a reduced iron phase, from which at least a portion of the slag phase constituting the reduced material has been separated. The pulverization process, indicated by arrow c from C to D in Figure 1 or Figure 2, separates the reduced slag phases 17 and 27 from the reduced iron phases 16 and 26 due to the impact of the pulverization, as shown in Figure 1D or Figure 2D. This pulverization and the subsequent sorting and recovery process described below physically separate the phosphorus. The reduced material is composed of substances with different pulverization characteristics, such as metals and oxides, and an interface between different phases may form. While the reduced material remains bonded to the slag phase (as shown in Figure 1C) after reduction, pulverization facilitates efficient separation at the interface between the reduced slag phase and the reduced iron phase 26. After separation, the reduced iron phase 26 can be easily recovered in the subsequent sorting and recovery process. 1 and 2 are conceptual diagrams, and in addition to the case where the reduced slag phases 17, 27 and the reduced iron phases 16, 26 are completely separated as shown in Figures 1 and 2, there may also be cases where some of the reduced slag phases 17, 27 remain in the reduced iron phases 16, 26. In this embodiment, the reduced iron phases 16, 26 that are completely separated from the reduced slag phases 17, 27 and the reduced iron phases 16, 26 where some of the reduced slag phases 17, 27 remain are collectively referred to as "reduced iron phase-containing material." The pulverization is performed using pulverization equipment such as a cage mill, ball mill, rotary mill, or jet mill.

[0044] [Sorting and collection process] In the sorting and recovery step, a material containing a reduced iron phase is sorted and recovered from the pulverized material. The sorting and recovery step, indicated by the arrow d from D to E in FIG. 1 or FIG. 2, yields a material containing a reduced iron phase (only reduced iron phases 16 and 26 are shown in FIG. 1 or FIG. 2E, for example). Because metallic iron is magnetic, magnetic separation can be used as a method for sorting and recovery. The iron phase becomes magnetic due to the previous reduction step, making magnetic separation possible. Magnetic separation is known to have higher separation efficiency than gravity separation and other methods. Note that if the reduction step is insufficient and the reduced iron phase is primarily composed of Fe3O4, the formation of a phase boundary may not be sufficient to promote pulverization. However, because Fe3O4 is magnetic like metallic iron, magnetic separation can still be used. This embodiment also encompasses such a configuration. The material containing a reduced iron phase may also be subjected to additional processing to produce an iron source.

[0045] The magnetic separation method is not particularly limited as long as it allows separation of the reduced iron phase and the reduced slag phase. For example, hand magnetic separation is acceptable, but when large-scale processing is required, a large-scale magnetic separator such as a drum-type magnetic separator or a rotary-type magnetic separator may be used. [Example]

[0046] The present embodiment will be described in more detail below with reference to examples. The present disclosure is not limited to the following examples, and appropriate modifications can be made within the scope of the above-mentioned and below-mentioned aims, and all such modifications are within the technical scope of the present disclosure.

[0047] In the following examples, laboratory tests were conducted to remove phosphorus from iron ore and obtain a reduced iron phase containing material.

[0048] [Preparation process] The iron ore from which phosphorus was removed was iron ore brand OreA and OreB, with chemical compositions shown in Table 1. The iron ore was used after sieving to a size of less than 2 mm. When a flux was used, crushed stone shown in Table 2 was used. As a comparative example, a phosphorus removal process using a common method of adding CaO was performed using limestone shown in Table 2 as a flux. As shown in Table 3, iron ore alone or a combination of iron ore and flux was used as the roasting composition. The SiO2 and Al2O3 contents in the roasting composition were calculated by converting the elements contained in the roasting composition into oxides, i.e., Si, Al, Ca, Fe, P, and Mg into SiO2, Al2O3, CaO, FeO, PO5, and MgO, respectively, and then calculating the proportions (mass%) of SiO2 and Al2O3 in the total oxides.

[0049] [Table 1]

[0050] [Table 2]

[0051] [Roasting process] A resistance-type electric heating furnace was used for roasting. The composition for roasting was placed in a dense MgO container manufactured by Nikkato Corporation, and heated to 1300°C (the ambient temperature inside the furnace) at a heating rate of 10°C / min in an air atmosphere, and then held at 1300°C for 30 minutes. The sample was then cooled to room temperature to obtain a roasted sample. The inventors separately confirmed that the reduction rate after roasting was almost 0%.

[0052] [Reduction process] The roasted sample was crushed by hand or using a cage mill and sieved to obtain a sample for reduction with a size of less than 2 mm. Reduction was carried out using a drum-type rotary heating furnace with an inner diameter of 130 mm and a length of 200 mm. The reducing gas was mixed at room temperature to have a gas composition of 70% by volume of H2, 20% by volume of CO2, 5% by volume of CO2, and 5% by volume of N2, and then introduced into the furnace. The reducing gas was also introduced immediately after the start of the temperature rise. The temperature was raised to 800°C at a rate of 450°C / h, held at 800°C for 60 minutes, and then cooled to room temperature in an N2 atmosphere to obtain a reduced sample. Other conditions for the reduction process were as follows. Note that the above temperatures are the ambient temperatures inside the furnace. Rotation speed of drum type rotary heating furnace: 12 rpm Sample amount for reduction: 500g Reducing gas flow rate: 10NL / min

[0053] [Table 3]

[0054] [Crushing process] The reduced sample was pulverized at 2850 rpm using a cage mill manufactured by Masuno Seisakusho Co., Ltd. 200 g was fed into the cage mill at a time, and the sample after pulverization was fed into the cage mill again, with the entire sample passing through the cage mill a total of three times to obtain a pulverized sample.

[0055] [Sorting and recovery (magnetic separation) process] As a sorting and recovery method, magnetic separation was performed to obtain a material containing reduced iron phase. Magnetic separation was performed by loading the pulverized sample into a dry drum magnetic separator. The magnetic force of the dry drum magnetic separator was 1200 Gauss and the rotation speed was 80 rpm. The amount of pulverized material fed to the dry drum magnetic separator was 50 g per run, and the process was performed twice (N1, N2), and a material containing reduced iron phase was obtained for each run.

[0056] [Calculation of phosphorus removal rate] The chemical composition (total iron and phosphorus) of the reduced iron phase material obtained in each run (N1, N2) was analyzed. The total iron (total iron) content was determined by titration using titanium (III) chloride reduction and potassium dichromate. Phosphorus was determined in accordance with JIS M8216 (absorption spectrophotometry). These results are shown in Table 4 as "chemical composition N1" and "chemical composition N2." The phosphorus removal rate for each run (N1, N2) was then calculated from the chemical composition of each run, and the average value was calculated. The phosphorus removal rate was calculated using the following formula. The obtained phosphorus removal rates (average values) are shown in Table 4.

[0057]

number

[0058] [Table 4]

[0059] Figure 3 shows a graph of the phosphorus removal rate for each roasting condition, created using the results described above. The bar graph patterns in Figure 3 indicate that the treatments were performed under the same conditions, except for the type of iron ore used. Figure 4 also shows a graph illustrating the relationship between the total amount of SiO2 and Al2O3 and the phosphorus removal rate for each roasting condition. It can be seen that the effect of adding no flux is equal to or greater than that achieved with limestone, as in the case of limestone, a conventional technology. This is thought to be because the molten liquid generated from the impurities (SiO2, Al2O3) originally contained in the iron ore solidifies while retaining the phosphorus, forming a slag phase that separates from the iron ore. This slag phase separates from the metallic iron phase during the crushing process, and because the slag phase is nonmagnetic, it is easily separated during the magnetic separation process.

[0060] In addition, when a roasting composition containing iron ore and flux was used for roasting, it was found that a higher phosphorus removal effect was obtained when crushed stone containing SiO2 as the main component was added compared to when limestone was added, which is a known process.

[0061] [Microscopic observation and EDX analysis] The roasted, reduced, and then pulverized sample No. 5 in Table 3 was embedded in resin, the cross section polished, and then observed under a scanning electron microscope. The results are shown in Figure 5. Furthermore, the components at each of the analysis points marked with symbols 1 and 2 in Figure 5 were analyzed using EDX (energy dispersive X-ray spectroscopy). The results are shown in Figure 6. The EDX semi-quantitative analysis values ​​in Figure 6 were calculated from the amount of each element except oxygen, assuming that each element forms an oxide as shown in the legend to Figure 6.

[0062] 5 and 6, it was confirmed that the gray area indicated by reference numeral 1 in Fig. 5 is the phosphorus-concentrated phase, and the white area indicated by reference numeral 2 in Fig. 5 is the iron phase. Furthermore, from the results in Fig. 5 and 6 and Table 4, it is believed that the reason a high phosphorus removal rate could be achieved by performing selective recovery after oxidizing roasting and reduction is that the phosphorus in the iron ore migrates to the impurity phase and is fixed without bonding to iron through the oxidizing roasting and reduction, i.e., the phosphorus is sufficiently separated and removed chemically, and the phosphorus-containing slag phase is separated and removed through the subsequent crushing and selective recovery, allowing the magnetic reduced iron phase to be recovered. [Explanation of symbols]

[0063] 1. Phosphorus-rich phase 2 Iron Phase 11, 21 Iron ore 12A Iron oxide-containing phases in iron ore 12B Impurity phase in iron ore (phase mainly composed of oxides of elements other than iron) 22 Flux 13, 23 Iron oxide-containing phase 14, 24 Roasted slag phase 25 Phosphorus Transfer 16, 26 Reduced iron phase 17, 27 Reduced slag phase a. Roasting b. Reduction c. Crushing d. Selective collection

Claims

1. Iron ore containing 0.05% by mass or more of phosphorus, and Al ２ O ３ and SiO ２ A baking composition comprising: Al when the elements contained in the composition for roasting are converted into oxides ２ O ３ and SiO ２ a preparation step of preparing a composition for baking in which the total amount of a roasting step of roasting the composition for roasting to obtain a roasted product; a reduction step of reducing the roasted product in an atmosphere containing at least one of CO gas and hydrogen gas to obtain a reduced product containing a reduced iron phase and a slag phase; a pulverization step of pulverizing the reduced material to obtain a pulverized material containing a reduced iron phase from which at least a portion of the slag phase constituting the reduced material has been separated; a sorting and recovery step of sorting and recovering the reduced iron phase-containing material from the pulverized material; wherein the atmospheric temperature in the reduction step is 900°C or lower.

2. The method for producing an iron source according to claim 1 , wherein the roasting composition consists of the iron ore.

3. The method for producing an iron source according to claim 1 , wherein the roasting composition comprises the iron ore and a flux.

4. The flux is Al ２ O ３ and SiO ２ The method for producing an iron source according to claim 3, comprising one or more of:

5. The method for producing an iron source according to any one of claims 1 to 4, wherein magnetic separation is performed as a method for separating and recovering the iron in the separating and recovering step.

6. The basicity of the roasting composition CaO / SiO ２ The method for producing an iron source according to any one of claims 1 to 4, wherein is less than 1.0.

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