WO2023162729A1 - Iron source production method - Google Patents

Abstract

A method for producing an iron source, comprising: a preparation step in which a mixture for roasting is prepared by mixing a raw material containing a phosphorus-containing iron ore and a flux; a roasting step in which the mixture for roasting is roasted to obtain a roasted product; a reduction step in which the roasted product is reduced 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 crushing step in which the reduced product is crushed to obtain a crushed product containing a reduced-iron-phase-containing product in which at least some of the slag phase constituting the reduced product has been separated; and a separation and recovery step in which the reduced-iron-phase-containing product is separated and recovered from the crushed product. In the method for producing an iron source, the reduction rate of iron by roasting is 10% or less, and the flux is a defined compound.

Description

Iron source manufacturing method

This disclosure relates to a method for producing an iron source. In particular, the present invention relates to a method for producing an iron source containing less phosphorus than iron ore as a raw material.

In recent years, due to the depletion of high-quality iron sources, it is becoming difficult to obtain iron ore with few impurities such as gangue as a raw material for steel products, and iron ore impurities are expected to increase in the future. As a pretreatment method for reforming low-grade iron ore containing a large amount of gangue into high-grade iron ore for direct ironmaking, for example, Patent Document 1 discloses iron ore that is put into a reduction furnace. In the direct ironmaking method in which stone is reduced with a reducing gas generated from fuel containing hydrocarbons to directly obtain raw materials for ironmaking without going through a pig iron manufacturing process, high-temperature furnace gas discharged from the reducing furnace is treated in a reduction roasting furnace. a step of reducing and roasting the hematite ore supplied from the ore storage site with the reducing components remaining in the furnace gas to make magnetite ore; It describes a method comprising the steps of: magnetically sorting with a sorter; and agglomerating the magnetite concentrate obtained by the magnetic sorting, calcining it into pellets, and supplying it to the reduction furnace.

Phosphorus is a component that lowers the grade of iron ore. In the existing blast furnace-converter furnace process, almost all of the phosphorus in the iron ore is transferred to hot metal in the blast furnace, and is generally removed in the subsequent hot metal pretreatment process and converter process. However, if the amount of phosphorus in iron ore, which is a raw material, increases, the cost of removing phosphorus in these processes increases, and productivity decreases. Therefore, development of a technique for removing phosphorus from iron ore used for ironmaking is desired.

For example, Patent Document 2 discloses a method for removing phosphorus from iron ore by wet treatment. Specifically, iron ore with a high phosphorus content is pulverized to 0.5 mm or less, water is added to make the pulp concentration about 35%, and H ₂ SO ₄ or HCl is added to the solvent and reacted at pH 2.0 or less to contain. Phosphorus minerals (mainly apatite) are decomposed and eluted, then magnetic substances such as magnetite are collected by magnetic separation, and non-magnetic substances such as SiO ₂ or Al ₂ O ₃ are sedimented and separated as slime and eluted into the liquid. A method for treating P-containing iron ore is described in which slaked lime or quicklime is added to neutralize the P in the pH range of 5.0 to 10.0, and the P-containing iron ore is separated and recovered as calcium phosphate. However, the method according to Patent Document 2 has a problem that it is difficult to ensure productivity because it is a wet process.

On the other hand, a dry process has also been proposed to remove phosphorus from iron ore. For example, Non-Patent Document 1 proposes a process for separating P in iron ore by concentrating it in a dicalcium silicate (C ₂ S) phase. Specifically, the basicity of the iron ore and the blending ratio of _the carbonaceous material are adjusted. By adding CaO and heating at a high temperature, a dicalcium silicate phase (2CaO--SiO ₂ , C ₂ S) coexists in the molten slag as a solid phase, and a calcium phosphate phase (3CaO--P ₂ O ₅ , C ₃ P ) as a solid solution (C ₂ S—C ₃ P solid solution).

JP-A-53-103915 JP-A-60-261501

Nobuhiro Maruoka et al., "Concentration of phosphorus in iron ore to dicalcium silicate phase by partial reduction treatment", Tetsu to Hagane, Vol. 107 (2021), No. 6, pp. 527-533

The method of Patent Document 1 is effective when phosphorus is combined with elements other than iron, but there is a problem that it cannot be removed when phosphorus is combined with iron. In addition, in the method of Non-Patent Document 1, it is difficult to adjust the oxygen partial pressure due to the use of carbon material, etc., and therefore phosphorus is likely to be mixed in the iron phase, making it difficult to remove phosphorus. As a result, problems such as sulfur contamination and greenhouse gas emissions are raised.

The present disclosure has been made in view of the above problems, and its purpose is to sufficiently remove phosphorus even when phosphorus present in iron ore is bound to iron. An object of the present invention is to realize a method for producing an iron source to be supplied.

Aspect 1 of the present invention is
a preparation step of mixing iron ore containing phosphorus and raw materials containing flux to prepare a roasting mixture;
a roasting step of roasting the roasting mixture 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-containing material from which at least a portion of the slag phase constituting the reduced material is separated;
a sorting and recovering step of sorting and recovering the reduced iron phase-containing material from the pulverized material,
The reduction rate of iron by roasting is 10% or less,
The flux is selected from the group consisting of alkali metal oxides, carbonates, hydroxides and hydrates, and alkaline earth metal oxides, carbonates, hydroxides and hydrates1 A method for producing an iron source including the above.

Aspect 2 of the present invention is
The method for producing an iron source according to aspect 1, wherein the flux is one or more selected from the group consisting of CaO, _CaCO3 and Ca(OH) ₂ .

Aspect 3 of the present invention is
3. The method for producing an iron source according to aspect 1 or 2, wherein magnetic separation is performed as a method of sorting and recovering in the sorting and recovering step.

Aspect 4 of the present invention is
4. The method for producing an iron source according to any one of aspects 1 to 3, wherein the atmosphere temperature in the reduction step is 850° C. or lower.

Aspect 5 of the present invention is
According to any one of aspects 1 to 4, wherein in the preparation step, the iron ore and the flux are mixed so that the basicity CaO/SiO ₂ of the roasting mixture is in the range of 1.0 to 5.0. is a method for producing an iron source.

Aspect 6 of the present invention is
The method for producing an iron source according to any one of aspects 1 to 5, wherein the reduction rate of iron after the reduction step is 50% or more.

Aspect 7 of the present invention is
7. The method for producing an iron source according to any one of aspects 1 to 6, wherein in the pulverization step, the reduced product is pulverized using a cage mill.

Aspect 8 of the present invention is
The method for producing an iron source according to any one of aspects 1 to 7, wherein the reduction rate of iron after the reduction step is 50% or more.

According to the present disclosure, it is possible to provide a method for producing an iron source for ironmaking or the like, which can sufficiently remove phosphorus even when phosphorus present in iron ore is bound to iron.

FIG. 1 is an image diagram schematically showing the steps of this embodiment. FIG. 2 is a scanning electron microscope image of the sample after pulverization of Example 2. FIG. FIG. 3 is a diagram showing the EDX analysis values of analysis points 1 and 2 in FIG. FIG. 4 is a diagram showing X-ray absorption edge spectra of samples in Examples. FIG. 5 is a graph showing the relationship between each reduction temperature and the phosphorus removal rate in Examples. FIG. 6 is a graph showing the relationship between the iron reduction rate and the phosphorus removal rate after the reduction step in the example.

The method for manufacturing an iron source according to this embodiment includes:
a preparation step of mixing iron ore containing phosphorus and raw materials containing flux to prepare a roasting mixture;
a roasting step of roasting the roasting mixture 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-containing material from which at least a portion of the slag phase constituting the reduced material is separated;
a sorting and recovering step of sorting and recovering the reduced iron phase-containing material from the pulverized material,
The reduction rate of iron by roasting is 10% or less,
The flux is selected from the group consisting of alkali metal oxides, carbonates, hydroxides and hydrates, and alkaline earth metal oxides, carbonates, hydroxides and hydrates1 Including above.

According to the production method of the present embodiment, the roasting step of performing oxidative roasting of the roasting mixture containing flux and iron ore, and the atmosphere containing at least one of CO gas and hydrogen gas are controlled to perform reduction. It is separated from the reduction process. As a result, the phosphorus bound to iron in the iron ore is transferred to the slag phase (components other than iron, impurity phase) formed by the roasting of the flux (oxidizing roasting) to bond with the slag components, and Through the above-mentioned reduction process, iron oxide is reduced while phosphorus is fixed to the slag component, and the phosphorus and iron phases can be chemically separated. It has been found that iron phase inclusions are obtained. In this embodiment, as the evaluation of the chemical bonding state of phosphorus in the examples described later, phosphorus and slag components are bonded, specifically, for example, a composite oxide of phosphorus and calcium oxide (the composite oxide is Ca ₂ P ₂ O ₇ ), it is considered that phosphorus in the iron ore can be sufficiently removed by trapping phosphorus.

Each step of the manufacturing method according to this embodiment will be described in detail below. FIG. 1 is an image diagram schematically showing each step of the manufacturing method according to this embodiment. In the following description of each process, there are cases where the description is based on FIG. 1, but FIG. 1 is only an image diagram and does not limit the present disclosure. For example, when phosphorus is not completely transferred to the slag phase by roasting, or when the slag phase and reduced iron phase are not completely separated by pulverization, and part of the slag phase remains bound to the reduced iron phase. However, such aspects are of course allowed, and the manufacturing method according to the present embodiment can also include these aspects.

[Preparation process]
A torrefaction mixture is prepared by mixing phosphorus-containing iron ore and flux-containing raw materials. By mixing these, a roasting mixture of iron ore 11 and flux 12 is obtained as shown in FIG. 1A.

The flux is selected from the group consisting of alkali metal oxides, carbonates, hydroxides and hydrates, and alkaline earth metal oxides, carbonates, hydroxides and hydrates1 Including above. These alkaline earth metal oxides and the like are compounds that easily combine with phosphorus. The above compounds _of alkali metals _{include Na2O} , _K2O , _Li2CO3 , _Na2CO3 , _{K2CO3 ,} NaOH, KOH and the like. Moreover, CaO (quicklime), _CaCO3 (limestone), Ca(OH) ₂ (slaked lime), etc. are mentioned as said compound of an alkaline-earth metal. Preferably, the flux is one or more selected from the group consisting of CaO, _CaCO3 and Ca(OH) ₂ . CaO, CaCO ₃ and Ca(OH) ₂ are preferred because they easily bond with phosphorus and are easily industrially available. In addition, by using SiO ₂ in iron ore together, the aforementioned composite oxide of phosphorus and calcium oxide can be easily formed, and phosphorus can be easily fixed. CaCO ₃ , which is widely used industrially, is more preferable. The flux is selected from the group consisting of the alkali metal oxides, carbonates, hydroxides and hydrates mentioned above and the alkaline earth metal oxides, carbonates, hydroxides and hydrates It may be a mixture of one or more fluxes and other fluxes. Other fluxes include, for example, soda-based flux, CaF ₂ , CaCl ₂ , Li ₂ CO ₃ -based flux, BaCO ₃ -based flux, and the like. The size of the flux may be any size generally used in industry.

The phosphorus-containing iron ore may contain, for example, 0.05% by mass or more of phosphorus. According to the present 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, furthermore 0.15% by mass or more. The iron ore may be pulverized, classified, or the like before being mixed with the flux to make the size uniform.

It is preferable to mix the iron ore and the flux so that the basicity CaO/SiO ₂ of the roasting mixture is in the range of 1.0 to 5.0. For example, depending on the amount of SiO ₂ contained in the iron ore, the flux is preferably one or more selected from the group consisting of CaO, CaCO ₃ and Ca(OH) ₂ , more preferably one of CaO and CaCO ₃ The above may be mixed so as to be within the above basicity range. Alternatively, depending on the amount of SiO ₂ contained in the iron ore, the flux is preferably one or more selected from the group consisting of CaO, CaCO ₃ and Ca(OH) ₂ , more preferably one of CaO and CaCO ₃ For example, the above and other above-described fluxes may be mixed so that the basicity is within the above range. By setting the basicity of the roasting mixture within the above range, a composite oxide of phosphorus and calcium oxide that is close to Ca ₂ P ₂ O ₇ can be easily formed. CaO/SiO ₂ is more preferably 3.0 or less. When calculating the above basicity CaO/SiO ₂ , Ca-containing compounds other than CaO are calculated by converting them into CaO. This is because Ca-containing compounds other than CaO, such as CaCO ₃ and Ca(OH) ₂ , contained in the flux are decomposed by heating to become CaO.

The above iron ore and flux should be mixed by an industrially used method. If necessary, a medium such as water may be further added to the iron ore and flux to form granules as a roasting mixture.

[Roasting process]
In the roasting step, the roasting mixture is roasted to obtain the roasted product shown in B of FIG. In the roasting process represented by the arrow a from A to B in FIG. In the iron ore 11, the phosphorus in the iron ore 11 migrates to the slag phase (impurity phase mainly composed of components other than iron, hereinafter referred to as the “roasted slag phase”) 14 formed by roasting the flux, and the roasted slag It is believed to bond with phase 14 . In order to exhibit the function and effect, it is preferable to set the roasting temperature to 1150° C. or higher at which at least a part of the mixture can be melted. Said temperature may even 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, the upper limit of the temperature may be set to about 1500° C. from the viewpoint of suppressing deterioration of equipment. The roasting temperature refers to the temperature in the packed layer of the mixture of iron ore and flux, and this temperature was controlled by the atmospheric temperature of the furnace used in the examples described later.

The roasting atmosphere in the present embodiment refers to an atmosphere in which the reduction rate of iron oxide due to roasting (referred to as the "iron reduction rate" in this specification) is 10% or less. In the present embodiment, the reduction of iron oxide is suppressed in the roasting stage, the roasting process and the reduction process are separated, and iron oxide is reduced in the reduction process, so that It is possible to separate phosphorus from the original iron phase (hereinafter simply referred to as "iron phase") and prevent phosphorus from being mixed into the iron phase. The reduction rate is preferably 8% or less, more preferably 5% or less, and may be 0%. Means for achieving the above reduction rate include the above-described atmosphere control, temperature control, and the like.

The atmosphere includes an oxygen-containing atmosphere. For example, it can be an air atmosphere. In the roasting step, it is possible to use, for example, a carbonaceous material as a heat source, and when this carbonaceous material is used, the atmosphere may be somewhat reducing than the atmospheric atmosphere, but such an atmosphere is also acceptable. As equipment for roasting, for example, an electric resistance furnace (external heating), a burner-type heating furnace, a Dwight Lloyd type sintering machine, a pot-type sintering machine, or the like can be used.

[Reduction step]
In the reduction step, the roasted product is reduced in an atmosphere containing at least one of CO gas and hydrogen gas to obtain a reduced product shown in C of FIG. 1, that is, a reduced product containing a reduced iron phase and a slag phase. Through the reduction step represented by the arrow b from B to C in FIG. A reduced product is obtained in which the roasted slag phase 14 is formed with the slag phase after undergoing this reduction step. The reason why phosphorus can be easily separated chemically by separating the roasting process and the reduction process in the present embodiment and performing reduction in the above atmosphere in the reduction process will be described in detail below.

When the oxygen partial pressure is lowered during reduction, the oxygen in P ₂ O ₅ in the slag is dissociated to generate phosphorus, which easily combines with Fe, making it difficult to remove phosphorus from the iron ore. Therefore, it is necessary to suppress fluctuations in the oxygen partial pressure during reduction. However, in the method of Non-Patent Document 1, the oxygen partial pressure during reduction is likely to fluctuate. The method of Non-Patent Document 1 uses a carbonaceous material, but if such a carbonaceous material is used, the oxygen partial pressure may locally decrease around the carbonaceous material during reduction, and the carbonaceous material may be heated. This is because unpredictable consumption of oxygen such as CO gas and CO ₂ gas occurs. On the other hand, according to the present embodiment, since a gaseous reducing agent such as CO gas or hydrogen gas is used for reduction, it is possible to suppress fluctuations in the oxygen partial pressure during reduction, and the reduction in the oxygen partial pressure makes it possible to separate phosphorus from iron. It is believed that the binding can be prevented so that the phosphorus can be kept chemically separated.

The gas that constitutes the atmosphere in the reduction step should contain at least one of CO gas and hydrogen gas, and the remaining gas components are not particularly limited. Since the purpose is reduction, the remaining gas components are preferably gases having no oxidizing action. The remaining gas components include, for example, CO ₂ gas, N ₂ gas, and the like. In the embodiments described later, CO gas alone or a mixed gas of CO gas and hydrogen gas is used as the reducing gas, but the reducing gas may be only hydrogen gas. It may be _N2 gas. According to this embodiment, the use of hydrogen as the reducing gas contributes to the reduction of greenhouse gases compared to the case of using carbon material as the reducing agent as in Non-Patent Document 1.

By performing the reduction under the above conditions, the transfer of SiO ₂ and Al ₂ O ₃ to the reduced slag phase 17 proceeds, and most of the phosphorus is fixed in the reduced slag phase 17, and the iron oxide-containing phase 13 is reduced. Reduction progresses, for example, M. A reduced iron phase 16 mainly composed of Fe (metallic iron) or Fe ₃ O ₄ is obtained. That is, by the above-described oxidizing roasting and reduction steps, the phosphorus fixed in the reduced slag phase 17 and the reduced iron phase 16 that are chemically sufficiently separated can be obtained.

In the present embodiment, the reduced iron phase includes M.I. It can contain not only Fe (metallic iron), but also FeO, in addition to the above Fe ₃ O ₄ obtained by reduction of Fe ₂ O ₃ . The reduced iron phase may also contain impurities such as oxides of elements other than iron.

The atmospheric temperature in the reduction process can be, for example, in the range of 600°C or higher and 900°C or lower. The ambient temperature in the reduction step refers to the ambient temperature in the furnace for reduction. Preferably, the ambient temperature in the reduction step is 850° C. or lower. As will be explained later in the Examples, when the ambient temperature is 900° C., signs of Fe—P phase formation were observed. From this, it is considered that if the temperature during reduction is too high, the phosphorus that migrates to the slag phase (impurity phase) in the roasting process and is fixed may bond with the iron phase again. The lower limit of the atmospheric temperature in the reduction step is preferably 650° C. or higher from the viewpoint of promoting the reduction.

The reduction time can be appropriately determined according to the throughput. After completion of the reduction at the ambient temperature, the cooling to room temperature may be performed in a non-oxidizing atmosphere, and is not limited to a reducing gas atmosphere. For example, an atmosphere of N ₂ gas or other inert gas such as Ar may be used.

The reduction rate of iron oxide after reduction in the reduction step (referred to in this specification as "iron reduction rate") is preferably 50% or more. By increasing the reduction rate of iron by reduction, the ratio of the reduced iron phase with different crushing characteristics from the phosphorus-containing reduced slag phase increases, and the reduced iron phase and the reduced slag phase, that is, the interface between the metal and the oxide, increases. It is considered that a large amount of reduced product is obtained. In the pulverization step of the reduced product, as will be described in detail later, cracks are more likely to occur at the metal-oxide interface than at the interface between the oxide phases such as the iron oxide phase and the reduced slag phase. phase and reduced slag phase can be efficiently separated. The reduction rate is more preferably 70% or higher, still more preferably 80% or higher, still more preferably 90% or higher, and most preferably 100%. The reduction rate is determined by the method described in Examples below.

[Pulverization process]
In the pulverization step, the reduced material is pulverized to obtain a pulverized material containing a reduced iron phase-containing material in which at least a portion of the slag phase constituting the reduced material is separated. By the pulverization process represented by the arrow c from C to D in FIG. 1, the reduced slag phase 17 and the reduced iron phase 16 are separated by the impact of the pulverization, as shown in D of FIG. Phosphorus is physically separated by this pulverization and the following sorting and recovery. The reductant is composed of substances with different grinding properties, such as metals and oxides, and heterophase interfaces can be formed. In the state of reduction, the reduced iron phase and the slag phase remain bonded as shown in C in FIG. Thereafter, the reduced iron phase 16 can be easily collected in the following sorting and collecting step. As described above, FIG. 1 is an image diagram, and in addition to the complete separation of the reduced slag phase 17 and the reduced iron phase 16 as shown in FIG. It can also include cases. In the present embodiment, the reduced iron phase 16 completely separated from the reduced slag phase 17 and the reduced iron phase 16 in which a part of the reduced slag phase 17 remains are collectively referred to as "reduced iron phase inclusions". Pulverization is performed using pulverization equipment such as a cage mill, ball mill, rotary mill and jet mill. Among these pulverizing facilities, it is preferable to use a cage mill to pulverize the reduced product. In pulverization by an impact-type cage mill, the force that causes cracks at the interface between the reduced iron phase and the slag phase is thought to act more efficiently than, for example, in pulverization by a grinding-type ball mill.

[Sort collection process]
In the sorting and recovering step, the reduced iron phase-containing material is sorted and recovered from the pulverized material. A reduced iron phase-containing material (in E of FIG. 1, only the reduced iron phase 16 is shown as an example) is obtained by the sorting and recovery step represented by the arrow d from D to E in FIG. Since metallic iron has magnetism, magnetic separation (magnetic separation) can be used as a method for sorting and recovering. Magnetic separation becomes possible because the iron phase becomes magnetized by the reduction in the previous stage. Magnetic separation is known to have higher separation efficiency than gravity separation. For example, when the reduction in the reduction step is not sufficiently performed and the reduced iron phase is mainly Fe ₃ O ₄ , the effect of promoting pulverization due to the formation of the interface between different phases is not sufficient, but Fe ₃ O ₄ is also combined with metallic iron. Since it also has magnetism, magnetic selection can be used, and such aspects can also be included in the present embodiment. Alternatively, the reduced iron phase-containing material may be subjected to further steps to obtain an iron source.

The method of magnetic separation is not particularly limited as long as it is possible to separate the reduced iron phase and the reduced slag phase. You may use a large-sized magnetic separator, such as.

Hereinafter, the present disclosure will be described more specifically with examples. The present disclosure is not limited by the following examples, and can be implemented with appropriate modifications within the scope that can match the spirit described above and below, and they are all within the technical scope of the present disclosure. subsumed in

In the following examples, laboratory tests were conducted to remove phosphorus from iron ore and obtain reduced iron phase inclusions.

[Preparation process]
Iron ores of brands A and B having the chemical components shown in Table 1 were used as iron ores to be removed from phosphorus. Both brands are Australian. Using the iron ore of the above grade A or B, No. Seven lab tests, numbered 1-7, were performed. No. In 1 to 5, the iron ore was sieved to less than 2 mm under the sieve and used. No. In 6 and 7, the iron ore was sieved to less than 0.5 mm below the sieves. Also, as a flux, No. In 1 to 5, a CaCO ₃ reagent (less than 45 μm under sieve) manufactured by Fuji Film Wako Pure Chemical Industries, Ltd. was used. On the other hand, No. In 6 and 7, industrial limestone (2 mm or more above the sieve and less than 4 mm below the sieve) was used as the flux. The above iron ore and flux were mixed so that the CaO/SiO ₂ ratio of the roasting mixture was 2.0 to obtain a roasting mixture.

[Roasting process]
A resistance electric heating furnace was used for roasting. The above roasting mixture is placed in a dense MgO container manufactured by Nikkato Co., Ltd., heated to 1300 ° C. (atmospheric temperature in the furnace) at a heating rate of 10 ° C./min in an air atmosphere, and then heated to 1300 ° C. for 30 minutes. held for a minute. Then, it was cooled to room temperature to obtain a roasted sample.

(Analysis of chemical components)
The chemical composition of the roasted samples was analyzed as follows. T. The amount of Fe (total iron) was measured by titanium (III) chloride reduction potassium dichromate titration method, and the amount of FeO was measured by potassium dichromate titration method. The amount of Fe (metallic iron) was determined by the bromine-methanol decomposition-EDTA titration method. Also, phosphorus was quantified according to JIS M8216 (absorption photometry). Note that FeO, M.I. When Fe was below the detection limit of 0.10% by mass, it was defined as 0.10%.

In addition, the iron reduction rate was obtained from the following formula. These results are shown in Table 2.

　In the above formula, (FeO%), (T.Fe%), and (M.Fe%) are FeO, T.E after each step (after roasting in Table 2, after reduction in Table 3 below). Fe, M. Each mass % of Fe is shown.

[Reduction step]
The roasted sample was previously crushed manually or by using a cage mill and sieved to obtain a sample for reduction with a sieve undersize of less than 2 mm. The reduction was carried out using a drum type rotary heating furnace with an inner diameter of 130 mm and a length of 200 mm. Reduction conditions were as shown in Table 3. The reducing gas was introduced into the furnace after mixing according to the gas composition shown in Table 3 at room temperature. Moreover, the reducing gas was introduced immediately after the start of the temperature rise. The temperature was increased to the temperature shown in Table 3 at a temperature increase rate of 450°C/h. After maintaining the temperature shown in Table 3 for the time shown in Table 3, the sample was cooled to room temperature in an _N2 atmosphere to obtain a reduced sample. Other conditions in the reduction step were as follows. The above temperature is the ambient temperature in the furnace.
・Rotation speed of drum type rotary heating furnace: 12 rpm
・Amount of sample for reduction: 500g
・Flow rate of reducing gas: 10 NL/min

The analysis of the chemical components of the reduced sample was carried out in the same manner as the analysis of the chemical components of the roasted sample. The results are also shown in Table 3.

[Pulverization process]
A cage mill manufactured by Masuno Seisakusho Co., Ltd. or a ball mill manufactured by Yoshida Seisakusho Co., Ltd. was used to pulverize the reduced sample. When using a cage mill, the number of revolutions was 2850 rpm. In addition, the amount supplied to the cage mill at one time was 200 g, and the sample after pulverization by the cage mill was supplied to the cage mill again, and the entire amount of the sample was processed so that it passed through the cage mill three times in total to obtain a pulverized sample. In the case of using a ball mill, steel balls were filled as grinding balls, and the powder was ground by driving at a rotation speed of 68 rpm for 60 seconds. The amount of sample supplied was 140 g.

[Sorting and collecting (magnetic separation) process]
As a method for sorting and collecting, magnetic separation was performed to obtain a reduced iron phase-containing material. Magnetic separation was carried out by inserting the pulverized sample into a dry drum magnetic separator. The rotational speed of the dry drum magnetic separator was set to 80 rpm. The amount of pulverized material supplied to the dry drum magnetic separator was set to 50 g/time, and the process was carried out twice. Then, the magnetization rate was measured and the chemical components (T. Fe and P) were analyzed for each time (N1, N2). The magnetization ratio was obtained from the following formula. Also, the chemical components were obtained in the same manner as the chemical component analysis of the roasted sample. Table 4 shows the results.

Furthermore, the phosphorus removal rate and iron recovery rate were obtained from the following formulas. The average value of two magnetic separations was used to calculate the phosphorus removal rate and iron recovery rate. Table 5 shows the results.

From the results of the laboratory test of phosphorus removal from iron ore carried out by the above method, 15% or more of phosphorus was removed by sorting and recovering after going through the roasting process and the reduction process according to the production method of this embodiment. rate was achieved.

[Microscopic observation and EDX analysis]
The sample pulverized after roasting and reduction in Example 2 was embedded in resin, cross-sectionally polished, and then observed with a scanning electron microscope. The results are shown in FIG. Further, the components at the analysis points indicated by reference numerals 1 and 2 in FIG. 2 were analyzed by EDX (energy dispersive X-ray spectroscopy). The results are shown in FIG. The EDX semi-quantitative analysis values in FIG. 3 were calculated from the amount of each element other than oxygen, assuming that each element forms an oxide shown in the legend of FIG.

　From Figures 2 and 3 above, it was confirmed that the gray portion indicated by reference numeral 1 in Figure 2 above is the phosphorus enriched phase, and the white area indicated by reference number 2 in Figure 2 above is the iron phase. 2 and 3 and the results in Table 5 above, the reason why a high phosphorus removal rate was achieved by performing sorting and recovery after oxidizing roasting and reduction is that the oxidizing roasting and reduction are: Phosphorus in the iron ore moves to the impurity phase and is fixed without bonding with iron, that is, the phosphorus is sufficiently separated and removed chemically, and the slag phase containing phosphorus is separated and removed by subsequent pulverization and sorting recovery. It is considered that the magnetic reduced iron phase was collected by the heat treatment.

[Evaluation of chemical bonding state of phosphorus using XAFS]
Using synchrotron radiation, each sample before and after roasting and each sample after reduction at each temperature of 600 ° C., 700 ° C., 800 ° C., and 900 ° C. in the laboratory test conducted using brand B iron ore X-ray absorption edge analysis (XAFS, X-ray Absorption Fine Structure) was performed to evaluate the chemical bonding state of phosphorus. The equipment and method shown below were used for the XAFS measurement. The evaluation results are shown in FIG. In FIG. 4, the same analysis was performed for each of the compounds Fe ₃ P, Fe ₂ P, and Ca ₂ P ₂ O ₇ as evaluation targets.
・Facility: Ritsumeikan University SR Center ・Beamline: BL-13
・Absorption edge: P K-edge, Si K-edge, Al K-edge at room temperature
・Measurement method: Measurement by fluorescence method

The spectral shoulder near 2145-2150 eV indicated by arrow Q in FIG. 4 indicates that phosphorus forms iron phosphate in iron ore before roasting. According to the present embodiment, by roasting the iron ore in the presence of flux, the absorption of the band indicated by the arrow Q disappears, and the bond close to Ca ₂ P ₂ O ₇ indicated by the solid line peak In other words, phosphorus is fixed to Ca.

[Reduction temperature]
In FIG. 4, energy absorption near 2145 to 2150 eV was not observed in the samples reduced at a temperature of 800° C. or lower, but in the samples reduced at 900° C., the Fe—P-based compound indicated by the arrow R At the same position as the peak of , energy absorption was observed as indicated by arrow Z in FIG. From this, it can be seen that the reduction temperature is preferably lower than 900° C. in order to suppress the binding of phosphorus to iron during reduction.

Also, based on the data in Tables 3 and 5, a graph showing the relationship between the temperature during reduction and the phosphorus removal rate is shown in FIG. From this FIG. 5, if the temperature during reduction is too high, the phosphorus removal rate tends to decrease, and from the viewpoint of achieving a higher phosphorus removal rate, for example, about 20% or more, the reduction It can be seen that it is preferable to set the temperature at 850° C. or lower.

Furthermore, based on the data in Tables 3 and 5, FIG. 6 shows a graph that summarizes the relationship between the iron reduction rate after the reduction process and the phosphorus removal rate. From this FIG. 6, if the iron reduction rate after the reduction step is preferably 50% or more, the phosphorus removal rate can be increased, and it is possible to achieve a higher phosphorus removal rate of about 20% or more. I understand. This is because, as mentioned above, the rate of reduction is increased by reduction, and the ratio of the reduced iron phase, which has different pulverization characteristics from the reduced slag phase containing phosphorus, increases, resulting in a reduced product with many metal-oxide interfaces. This is probably because the reduced iron phase and the reduced slag phase were efficiently separated from each other because cracks were likely to occur at the interface during pulverization. In addition, No. In No. 3, the reduction rate is high, but the temperature during reduction is high as described above, and the phosphorus removal rate is No. 3. It was lower than 2nd class.

In addition, in FIG. 6, when the phosphorus removal rate was compared between samples showing similar reduction rates, No. 1, which has a reduction rate of about 90%, was found. 2 and No. From the comparison with No. 6 and 7, No. It can be seen that the phosphorus removal rate of sample No. 2 is high. This is because, in the pulverization process, preferably by pulverizing the reduced product with a cage mill, the force that causes cracks at the interface between the reduced iron phase and the slag phase acts efficiently, and the slag phase containing phosphorus can be sufficiently separated. According to

This application is a Japanese patent application filed on February 28, 2022, a priority claim based on Japanese Patent Application No. 2022-030105, and a Japanese patent application filed on August 25, 2022. It is accompanied by a priority claim based on a patent application, Japanese Patent Application No. 2022-134387. Japanese Patent Application No. 2022-030105 and Japanese Patent Application No. 2022-134387 are incorporated herein by reference.

1 Phosphorus-enriched phase 2 Iron phase 11 Iron ore 12 Flux 13 Iron oxide-containing phase 14 Roasted slag phase 15 Phosphorus migration 16 Reduced iron phase 17 Reduced slag phase a Roasting b Reduction c Pulverization d Sorting and recovery

Claims (8)

a preparation step of mixing iron ore containing phosphorus and raw materials containing flux to prepare a roasting mixture;
a roasting step of roasting the roasting mixture 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-containing material from which at least a portion of the slag phase constituting the reduced material is separated;
a sorting and recovering step of sorting and recovering the reduced iron phase-containing material from the pulverized material,
The reduction rate of iron by roasting is 10% or less,
The flux is selected from the group consisting of alkali metal oxides, carbonates, hydroxides and hydrates, and alkaline earth metal oxides, carbonates, hydroxides and hydrates1 A method for producing an iron source, comprising the above. The method for producing an iron source according to claim 1, wherein the flux is one or more selected from the group consisting of CaO, _CaCO3 and Ca(OH) ₂ . The method for manufacturing an iron source according to claim 1 or 2, wherein in the sorting and recovering step, magnetic sorting is performed as a sorting and recovering method. The method for producing an iron source according to claim 1 or 2, wherein the atmosphere temperature in the reduction step is 850°C or lower. The iron according to claim 1 or 2, wherein in the preparation step, the iron ore and flux are mixed so that the basicity CaO/SiO ₂ of the roasting mixture is in the range of 1.0 to 5.0. source manufacturing method. The method for producing an iron source according to claim 1 or 2, wherein the reduction rate of iron after the reduction step is 50% or more. The method for producing an iron source according to claim 1 or 2, wherein in the pulverization step, the reduced product is pulverized using a cage mill. The method for producing an iron source according to claim 4, wherein the reduction rate of iron after the reduction step is 50% or more.

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