METHOD FOR PRODUCING AN AGGLOMERATED RAW MATERIAL

Description

[001] The present invention relates to a method for producing an agglomerated feedstock, which involves agglomerating a feedstock containing powdered iron oxide. Background of the technique

[002] When a raw material containing powdered iron oxide is used in a pig iron production process, which involves gas reduction of a raw material using a blast furnace, shaft furnace or similar, it is necessary to agglomerate the powdered iron oxide-containing raw material to ensure gas permeability in the furnace. As a technique for agglomerating a powdered raw material, Non-Patent Literature 1 describes a production method involving the agglomeration of a powdered raw material, in powder or granular form, whose melting point or decomposition temperature and sintering temperature are close to each other. In the production method, silicon nitride is used as the powdered raw material, and the powdered raw material is agglomerated by a hot press that compresses the powdered raw material while heating it. The heating of the powdered raw material by the hot press is carried out by heating a mold filled with the powdered raw material.Non-Patented Literature 1 states that the mold can be heated by a resistance heating method, an induction heating method, or something similar. The heating temperature of silicon nitride as a powdered raw material is set at 1800°C, which is close to 1900°C, which is the melting point of silicon nitride or the temperature at which silicon nitride begins to decompose. Furthermore, the pressure applied to the silicon nitride in the hot press is fixed at 10 atmospheres. The literature states... Petition 870260024766, dated 03 / 17 / 2026, page 7 / 74 2 / 22 that this hot pressing method can sinter silicon nitride without melting it. List of citations Non-Patented Literature

[003] NPL-1: Pressure Application Technology for Sintering of Ceramics, Journal of High Pressure Institute of Japan, 1992, vol 30, no. 2, pgs. 60-68 Summary of the invention Technical problem

[004] As described above, in the method described in the Literature Unpatented Literature 1 describes how silicon nitride powder, as a feedstock, is heated to its melting point or decomposition temperature while being pressed. Because the heating temperature is high, the method described in Unpatented Literature 1 can consume a significant amount of energy when agglomerating the silicon nitride. Furthermore, when agglomerating a feedstock for use in a blast furnace or shaft furnace, it is preferable to perform the agglomeration at a lower temperature than conventional methods, and as low as possible.

[005] The present invention was created to solve the above problem. Therefore, the objective of the present invention is to provide a method for producing agglomerated raw material that can agglomerate a raw material at a lower temperature than conventional methods, thereby reducing energy consumption. Solution to the problem

[006] The present invention to solve the above problem can be presented as follows: [1] A method for producing an agglomerated feedstock, including pressing and heating a feedstock containing iron oxide with a particle size smaller than Petition 870260024766, dated 03 / 17 / 2026, page 8 / 74 3 / 22 a predefined particle size, thus agglomerating the raw material, wherein the raw material contains iron oxide in an amount greater than 50% by mass and the raw material is heated by electric heating. [2] The method for producing an agglomerated feedstock described in item [1], wherein the feedstock contains 10% by mass or more of a metal that deforms plastically. [3] The method for producing an agglomerated feedstock described in item [2], wherein the feedstock is agglomerated by heating to 700°C or more while being pressed at 20 MPa or more. [4] The method for producing an agglomerated feedstock described in item [2] or [3], wherein the metal has an electrical conductivity of 11 χ 106S / m or more. [5] A method for producing an agglomerated feedstock, including pressing and heating a feedstock containing iron oxide with a particle size smaller than a predefined particle size, thereby agglomerating the feedstock, wherein the feedstock contains iron oxide in an amount greater than 50% by mass, and wherein a pressing pressure and a heating temperature satisfy the following inequality (1): P > 40 - (T - 900) / 10 (1) where P is the pressure (MPa) and T is the temperature (°C). [6] The method for producing an agglomerated raw material described in item [5], wherein, when the heating of the raw material is electrical heating, the pressure and temperature satisfy the following inequality (2) instead of inequality (1): P > 40 - (T - 700) / 10 (2) where P is the pressure (MPa) and T is the temperature (°C). Petition 870260024766, dated 03 / 17 / 2026, p. 9 / 74 4 / 22 [7] The method for producing an agglomerated feedstock described in item [5], wherein the feedstock contains 10% by mass or more of a plastically deformable metal and has an electrical conductivity of 11 χ 106S / m or more, and wherein when the feedstock is heated electrically, the pressure and temperature satisfy the following inequality (3) instead of inequality (1): P > 40 - (T - 500) / 10 (3) where P is the pressure (MPa) and T is the temperature (°C). Advantageous effects of the invention

[007] According to the present invention, a raw material containing iron oxide can be agglomerated at a lower temperature than in conventional methods, thus allowing an overall reduction in energy consumption. Brief description of the drawings

[008] [FIGURE 1] FIGURE 1 is a diagram that schematically shows an example of a double cylinder type pressure device to which a method of producing agglomerated raw material according to an embodiment of the present invention can be applied.

[009] [FIGURE 2] FIGURE 2 is a diagram showing a mold used in the experiment. Examples Description of modalities

[0010] A method for producing agglomerated raw material, according to an embodiment of the present invention, is a production method that involves agglomerating a raw material containing more than 50% by mass of iron oxide with a particle size smaller than a predefined particle size (hereinafter referred to as raw material). It is also a production method Petition 870260024766, dated 03 / 17 / 2026, page 10 / 74 5 / 22 which, by agglomerating the raw material, allows it to be used as a raw material in a pig iron production process using, for example, a blast furnace or a shaft furnace. The predefined particle size is a suitable size for a raw material to be used in a pig iron production process using a blast furnace or a shaft furnace. In particular, the predefined particle size may be equal to or greater than 5 mm and less than 50 mm. Thus, in the present embodiments, the raw material containing iron oxide with a particle size smaller than a predefined particle size is a raw material containing iron ore with a particle size smaller than 5 mm or return ore with a particle size smaller than 5 mm produced in a sintered ore production process.The raw material may contain a metal oxide, such as silicon dioxide, calcium oxide, or aluminum oxide, and a non-ferrous material, in addition to iron oxide as the main component. The total amount of metal oxide other than iron oxide, non-ferrous material, etc., preferably does not exceed 20% by mass of the raw material. In the present embodiments, the particle size is determined by a sieve; for example, iron ore with a particle size of less than 5 mm refers to iron ore that is sieved through a 5 mm mesh sieve.

[0011] In the agglomerated raw material production method of the present embodiments, the raw material is agglomerated by heating it to a target temperature and pressing it to a target pressure. Thus, the raw material is agglomerated by increasing the temperature of the raw material to the target temperature and by increasing the pressure applied to the raw material to the target pressure. The pressure and temperature of the raw material can be increased to their target values ​​substantially simultaneously. Alternatively, the raw material can be agglomerated by increasing the temperature of the raw material to the target temperature. Petition 870260024766, dated 03 / 17 / 2026, p. 11 / 74 6 / 22 target temperature when the target pressure of the raw material has been reached, or the raw material can be agglomerated by increasing the pressure of the raw material to the target pressure when the target temperature of the raw material has been reached. The target pressure and temperature are a pressure and a temperature at which the raw material can be agglomerated and which can be determined experimentally. For example, the pressure can be determined by measuring the pressure in a container filled with the raw material using a conventionally known pressure sensor or it can be calculated based on a load applied to the container to apply pressure to the raw material. The temperature can be determined by measuring the temperature in the container filled with the raw material using a temperature sensor installed on the inner wall of the container.

[0012] The raw material can be pressed by any conventionally known pressing method, for example, a double cylinder method. Figure 1 is a diagram schematically showing an example of a double cylinder type pressing device to which a method of producing agglomerated raw material according to an embodiment of the present invention can be applied. As shown in FIGURE 1, the double cylinder type pressing device includes a pair of cylinders 1 arranged with a predetermined gap (not shown) between them and with a plurality of molds (not shown), each corresponding to the shape of half of a molded product, formed on their peripheral surfaces. A raw material 2 is filled into the molds of the cylinders 1, and the raw material 2 is pressed as the cylinders 1 rotate and the molds of the cylinders 1 approach each other.Alternatively, raw material 2 can be pressed using, instead of a double cylinder type pressing device, a tablet compression method that involves filling raw material 2 into a tablet. Petition 870260024766, dated 03 / 17 / 2026, page 12 / 74 7 / 22 step formed by a mold and a punch, and compression molding of the raw material 2 pushing the punch into the space.

[0013] Raw material 2 can be heated using an electric furnace; however, it is preferable to heat raw material 2 primarily by means of electrical heating. Electrical heating is a method that involves applying an electric current to a raw material to heat it. In the double-cylinder type pressure device shown in FIGURE 1, an anode 5 and a cathode 6 of a power supply device 4 are connected to one and the other, respectively, of the cylinders 1. The double-cylinder type pressure device shown in Figure 1 is therefore configured to be able to electrically heat raw material 2 while pressing it.

[0014] Induction heating is a method that involves placing raw material 2 in a magnetic field, generated by applying an alternating current to a conducting wire, to induce an electric current in raw material 2, thus heating it. Therefore, induction heating also heats raw material 2 by allowing electricity to flow through raw material 2. Electrical heating according to the present embodiments therefore includes not only direct electrical heating but also induction heating. In the double-cylinder type pressure device shown in FIGURE 1, a magnetic field is generated around it to induce an electric current in raw material 2, thus heating raw material 2.The phrase "heating raw material 2 primarily by electric heating" means that when raw material 2 is heated using electric heating and other heating methods combined, the amount of heat generated in raw material 2 by electric heating is at least 50% of the total heat generated in raw material 2. The other heating method(s) include, for example... Petition 870260024766, dated 03 / 17 / 2026, page 13 / 74 8 / 22 For example, heating in an electric furnace and heating the raw material with the heat generated by the combustion of a certain fuel.

[0015] As described above, according to the agglomerated raw material production method of the present embodiments, raw material 2 is heated while its particles are being pressed or compressed against each other. Thus, the heating of raw material 2 can be carried out with the contact areas of the particles increased compared to the heating of unpressed raw material 2. This promotes bonding between the particles of raw material 2, enabling the agglomeration of raw material 2 at a lower temperature than in the agglomeration of unpressed raw material 2, even though raw material 2 contains 50% or more by mass of iron oxide, which is difficult to agglomerate.

[0016] In the production method of agglomerated raw material of the present embodiments, it is preferable to add a granular or powdered metal, which deforms plastically and has a higher electrical conductivity than iron, to raw material 2 to facilitate the agglomeration of raw material 2. The additive metal to be added to raw material 2 is, for example, copper, iron, or niobium. When the raw material 2 to which this metal has been added is pressed and heated in the manner described above, the additive metal is pressed by the raw material 2 and deforms plastically. The particles of raw material 2 are brought into close contact with each other by means of the plastically deformed additive metal, which causes the particles to become strongly bonded. Thus, the additive metal acts as a binder.Therefore, compared to the case where raw material 2 does not contain additive metal, the particles of raw material 2 can be joined at a lower temperature to obtain an agglomerated raw material 3. Petition 870260024766, dated 03 / 17 / 2026, page 14 / 74 9 / 22

[0017] As the amount of additive metal in feedstock 2 increases, the amount of iron oxide to be reduced decreases. Since agglomerated feedstock 3 is used as feedstock in a pig iron production process that performs gas reduction of the feedstock, a decrease in the amount of iron oxide contained in agglomerated feedstock 3 is undesirable. Therefore, it is preferable to use feedstock 2 containing more than 50% by mass of iron oxide and to use the additive metal in the smallest possible quantity. Furthermore, while the additive metal plastically deforms and binds the particles of feedstock 2, it fills the gaps between the particles of feedstock 2. Therefore, if the amount of additive metal is too large, the gas permeability of agglomerated feedstock 3 will be low, leading to low reducibility of the feedstock. Therefore, the amount of additive metal is preferably as small as possible.For the reasons stated above, the amount of additive metal may be at least 10% by mass and less than 50% by mass, preferably not less than 10% by mass and not more than 30% by mass.

[0018] When raw material 2 is electrically heated while being pressed, electricity flows along the surface of the iron oxide. The electricity flows to the contact portions of the particles of raw material 2, and therefore the contact portions are heated and their temperatures are raised, which causes the particles of raw material 2 to be joined and agglomerated. Due to the pressure applied to raw material 2, its particles are brought closer to each other with narrow spaces between them. Raw material 2 is directly heated electrically, with air present in the spaces. Specifically, the potential difference between the electrodes is increased. Iron oxide, which is an insulator, and the air described above exist between the electrodes. It is possible that the potential difference Petition 870260024766, dated 03 / 17 / 2026, p. 15 / 74 10 / 22 break the air insulation, allowing electricity to flow along the surface of the raw material 2. In the case of induction heating, it is possible that a magnetic field, generated by applying an alternating current to a conducting wire, generates an electric current, so that electricity flows along the surface of the raw material 2.

[0019] When raw material 2 contains the additive metal described above, electricity flows to the additive metal, and a large amount of heat (Joule heat) is generated by the metal. Thus, compared to the case where raw material 2 does not contain additive metal, a greater amount of heat (Joule heat) is generated in the contact portions of the particles of raw material 2, and the particles are joined and agglomerated. Since the heat is generated primarily by the additive metal, the particles of raw material 2 can be joined and agglomerated without heating the entire raw material 2 to a target temperature. In other words, the particles of raw material 2 can be joined and agglomerated at a lower average temperature than the entire raw material 2 containing the additive metal. Thus, by electrically heating raw material 2, the particles of raw material 2 can be joined and agglomerated without heating the entire raw material 2.This can reduce the energy consumption required to agglomerate the raw material 2. In addition, reducing the heating temperature can facilitate the heating of the raw material and can reduce the heat resistance of a mold required for agglomerating the raw material.

[0020] An agglomerating agent, such as coke powder, is conventionally used in the production of an agglomerated ore that is to be used as feedstock in a blast furnace or shaft furnace; the ore is agglomerated by combustion of the agglomerating agent. On the other hand, in the method of producing feedstock Petition 870260024766, dated 03 / 17 / 2026, page 16 / 74 11 / 22 agglomerated by the present embodiments, an agglomerated ore can be produced by heating using an electric furnace or by electric heating. The present production method has the advantage of being able to reduce the CO2 generation associated with the combustion of an agglomerating agent.

[0021] The method of producing agglomerated raw materials of the present embodiments will be described in more detail with reference to experimental examples in which the agglomerated raw materials were produced on a laboratory scale. (Experimental Example 1)

[0022] Return ore with a particle size of less than 5 mm was used as raw material. The composition of the return ore components was as follows: Fe2O3 74.8% by mass, FeO 7.0% by mass, SiO2 5.0% by mass, CaO 10.0% by mass, AhO3 1.5% by mass, and the remainder as incidental impurities. The T. Fe was 57.7% by mass. Figure 2 is a diagram showing a mold used in Experimental Example 1. Mold 7 shown in FIGURE 2 has a cylindrical shape. The raw material was placed in mold 7, and cylindrical punches 8 were inserted into mold 7 through openings formed at both axial ends of mold 7 to seal the raw material. Since mold 7 and punches 8 must be heated to approximately 1100°C, they are made of a heat-resistant material. Punches 8 must conduct electricity during their electrical heating; therefore, they are made of a conductive material.

[0023] Next, the raw material was pressed to a target pressure and held at that pressure. In Experimental Example 1, the raw material was pressed by pressing the punches 8 using the Autograph (registered trademark). The pressure applied to the raw material was calculated based on the compressive load applied by the Autograph. Petition 870260024766, dated 03 / 17 / 2026, page 17 / 74 12 / 22 (registered trademark) and in the cross-sectional area of ​​mold 7. In Experimental Example 1, the raw material was pressed by pressing the punches 8 under a compressive load corresponding to the target pressure.

[0024] After that, mold 7 containing the raw material was heated to a predetermined target temperature. In Experimental Example 1, the temperature of mold 7 was raised to the target temperature at a heating rate of 200°C / min in an electric furnace. After the target temperature was reached, the pressure and temperature conditions were maintained for about 5 minutes. To determine if the target temperature was reached, the temperature of the inner surface of mold 7 was measured using an undisclosed thermometer provided on the inner surface and the measured temperature was compared with the target temperature.

[0025] After 5 minutes, the raw material was removed from mold 7, and the raw material was evaluated for agglomeration. In particular, the agglomerated raw material, which had been removed from mold 7, was dropped from a height of 1.0 m, and whether or not it broke was visually determined. When the agglomerated raw material, which had been removed from mold 7, was broken or chipped due to the impact of the fall, the raw material was considered non-agglomerated. The heating temperature and pressure of the raw material and the results of the agglomeration evaluation are shown in Table 1 below. In Table 1 and subsequent tables, O indicates that the raw material was agglomerated and X indicates that the raw material was not agglomerated. Petition 870260024766, dated 03 / 17 / 2026, p. 18 / 74 13 / 22 [Table 1] Temperature (°C) Pressure (MPa) Agglomeration Example of the invention 1 1100 20 o Comparative example 1 1000 20 X Comparative example 2 900 20 X Comparative example 3 700 20 X Example of the invention 2 900 40 o Comparative example 4 700 40 X

[0026] As shown in Table 1, in the Experimental Example 1, the raw material was agglomerated under conditions of a pressure of 20 MPa and a heating temperature of 1100°C. On the other hand, even at a pressure of 20 MPa, the raw material was not agglomerated when the heating temperature was lower than 1100°C. When the pressure was 40 MPa, the raw material was agglomerated even at a heating temperature of 900°C, which is lower than 1100°C. The following inequality (1) can be derived from the results of Examples of the invention 1 and 2 in Table 1. Thus, the data indicate that there is a correlation between the pressure and the heating temperature at which the raw material is agglomerated; the raw material is agglomerated when the pressure and temperature applied to the raw material satisfy the following inequality (1). P > 40 - (T - 900) / 10 (1)

[0027] In inequality (1), P is the pressure (MPa) at which the raw material is pressed and T is the temperature (°C) at which the raw material is heated. When a predetermined pressure is applied to the raw material, the lowest temperature to obtain agglomeration of the raw material can be determined by determining the minimum value. Petition 870260024766, dated 03 / 17 / 2026, page 19 / 74 14 / 22 of T that satisfies inequality (1). Similarly, when the raw material is heated to a predetermined temperature, the lowest pressure to obtain agglomeration of the raw material can be determined by the minimum value of P that satisfies inequality (1). (Experimental Example 2)

[0028] In Experimental Example 2, metallic iron was added to the raw material of Experimental Example 1. Metallic iron refers to unoxidized iron, and in Experimental Example 2, metallic iron with a particle size of about 150 μm or less and a purity of 90% by mass was added to the raw material. After thoroughly stirring and mixing the raw material and metallic iron, they were placed in mold 7. The heating temperature and pressure of the raw material, the amount of metallic iron, and the results of the agglomeration assessment in Experimental Example 2 are shown in Table 2 below. The heating and pressing of the raw material were carried out according to the same procedure as in Experimental Example 1. [Table 2] Temperature (°C) Pressure (MPa) Amount of metallic iron (% by mass) (included in the total) Agglomeration Example of the invention 3 1100 20 10 o Example of the invention 4 1000 20 10 o Example of the invention 5 1000 20 20 o Example Comp.5 900 20 10 X

[0029] As shown in Table 2, in the Example of the invention of Experimental Example 2, the raw material was agglomerated under conditions of 20 MPa pressure and a heating temperature of 1,000°C. The result indicates that, by adding 10% by mass of iron Petition 870260024766, dated 03 / 17 / 2026, page 20 / 74 15 / 22 metallic to the raw material, the heating temperature to obtain agglomeration of the raw material can be reduced by 100°C compared to that of Example 1 of Experimental Example 1. Furthermore, in Example 5, in which the amount of metallic iron was increased to 20% by mass, the raw material was agglomerated under pressure conditions of 20 MPa and a heating temperature of 1,000°C. This indicates that metallic iron can be added to the raw material in an amount of 10% by mass or more.

[0030] These results are considered to be due to the fact that the metallic iron was pressed and plastically deformed by pressing and heating the raw material, and the plastically deformed metallic iron acted as a binder, so that the particles of the raw material were joined and agglomerated by means of the metallic iron. Thus, the reduction in temperature to obtain the agglomeration of the raw material is considered to be due to the fact that the metallic iron acted as a binder. (Experimental Example 3)

[0031] In Experimental Example 3, the agglomeration of the raw material was carried out using the same procedure as in Experimental Example 1, except that the raw material was filled into mold 7 under a nitrogen atmosphere and the temperature of the raw material was raised at a rate of 200°C per minute to the target temperature by means of electrical heating instead of heating by an electric furnace. In Experimental Example 3, an anode 5 and a cathode 6 were connected to punches 8 inserted into openings at both ends of mold 7, and 3 kWh of pulsed energy were applied from a power supply device 4 under a nitrogen atmosphere to electrically heat the raw material. The heating temperature and pressure of the raw material 2 and the results of the agglomeration assessment in Experimental Example 3 are shown in Table 3 below. Petition 870260024766, dated 03 / 17 / 2026, page 21 / 74 16 / 22 [Table 3] Temperature (°C) Pressure (MPa) Heating method Agglomeration Example of the invention 6 1100 20 Electric heating Example of the invention 7 900 20 Electric heating Example of the invention 8 700 40 Electric heating Example of ref. 1 700 20 Electric heating X Example of ref. 2 500 20 Electric heating X

[0032] As shown in Table 3, in the invention example of Experimental Example 3, the raw material was agglomerated under conditions of a pressure of 20 MPa and a heating temperature of 900°C. The result indicates that, by heating the raw material by means of electric heating, the heating temperature to obtain agglomeration of the raw material can be reduced by 200°C compared to that of invention example 1 of Experimental Example 1. Similarly, in invention example 8 of Experimental Example 3, raw material 2 was agglomerated under conditions of a pressure of 40 MPa and a heating temperature of 700°C. This indicates that the heating temperature to obtain agglomeration of the raw material can be reduced by 200°C compared to that of invention example 2 of Experimental Example 1.

[0033] When the raw material is heated electrically, the air insulation in the spaces between the particles of raw material 2 is broken due to the potential difference between electrodes 5 and 6, and electricity flows along the surface of the raw material. The Joule heat generated by the flow of electricity selectively heats the surface of the raw material. Although the average temperature of the entire raw material is low, the particles of the raw material are joined together on their surfaces, whose temperatures are locally high. This Petition 870260024766, dated 03 / 17 / 2026, page 22 / 74 17 / 22 may explain the reduction in crowding temperature.

[0034] The following inequality (2) can be derived from the results of Examples of the invention 7 and 8 shown in Table 3. Thus, the data indicate that, in the case of electric heating of raw material 2, the raw material is agglomerated when the pressure and temperature applied to the raw material satisfy the following inequality (2). P > 40 - (T - 700) / 10 (2)

[0035] In inequality (2), P is the pressure (MPa) at which the raw material is pressed, and T is the temperature (°C) at which the raw material is heated. The lowest temperature to obtain agglomeration of the raw material can be determined by the minimum value of T that satisfies inequality (2). (Experimental Example 4)

[0036] In Experimental Example 4, the agglomeration of the raw material was carried out using the same procedure as in Experimental Example 3, except that metallic iron, metallic copper, or metallic niobium were added to the raw material. The heating temperature and pressure of the raw material, the amount of metallic iron, and the results of the agglomeration evaluation in Experimental Example 4 are shown in Table 4 below. [Table 4] Temperature (°C) Pressure (MPa) Heating method Type and quantity of metal (% by mass) included in the total Agglomeration Example of the invention 9 700 20 Electric heating Metallic iron 10 o Example of the invention 10 700 20 Electric heating Metallic iron 20 o Petition 870260024766, dated 03 / 17 / 2026, page 23 / 74 18 / 22 Temperature (°C) Pressure (MPa) Heating method Type and quantity of metal (% by mass) included in the total Agglomeration Example of the invention 11 700 20 Electric heating Metallic copper 10 o Reference example 3 700 20 Electric heating Metallic niobium 10 x

[0037] As shown in Table 4, in Inventive Example 9 of Experimental Example 4, the raw material was agglomerated under conditions of a pressure of 20 MPa and a heating temperature of 700°C. The result indicates that by adding 10% by mass of metallic iron to the raw material and electrically heating the raw material, the heating temperature to obtain agglomeration of the raw material can be reduced by 400°C compared to that of Inventive Example 1 of Experimental Example 1. Furthermore, in Inventive Example 10, in which the amount of metallic iron was 20% by mass, the raw material was agglomerated under conditions of a pressure of 20 MPa and a heating temperature of 700°C. This indicates that metallic iron can be added to the raw material in an amount of 10% by mass or more, also in the case of electrical heating of the raw material.

[0038] In Inventive Example 11, in which 10% by mass of metallic copper was added to the raw material, the raw material was agglomerated under conditions of a pressure of 20 MPa and a heating temperature of 700°C. On the other hand, in the Reference Example 3, in which 10% by mass of copper was added to the raw material, the raw material was agglomerated under conditions of a pressure of 20 MPa and a heating temperature of 700°C. As can be seen in equation (4), the amount of heat generated by electrical heating is greater for a metal with relatively high electrical conductivity than for a metal with relatively low electrical conductivity when the same voltage is applied to the reference metals. Petition 870260024766, dated 03 / 17 / 2026, p. 24 / 74 19 / 22 of metallic niobium were added to the raw material, the raw material was not agglomerated under conditions of 20 MPa pressure and 700°C heating temperature.

[0039] The amount of heat generated by electric heating can be calculated using the following equation (4). Q = V2 / R (4)

[0040] In equation (4), Q is the amount of heat (J) generated, V is a voltage (V) and R is an electrical resistance (Ω).

[0041] As can be seen in equation (4), the amount of heat generated by electrical heating is greater for a metal with relatively high electrical conductivity than for a metal with relatively low electrical conductivity when the same voltage is applied to the metals. Considering that the electrical conductivity of iron is 11 χ 106S / m, the electrical conductivity of copper is 64 χ 106S / m and the electrical conductivity of niobium is 7 χ 106S / m, it can be said that the electrical conductivity of a metal for use as an additive metal is preferably at least 11 χ 106S / m, which is the electrical conductivity of iron. The binding effect of a metal is obtained independently of its electrical conductivity. Therefore, even when 10% by mass of metallic niobium is added to the raw material, the raw material can be agglomerated under conditions of a pressure of 20 MPa and a heating temperature of 900°C.

[0042] The following inequality (3) can be derived from the results of Examples of the invention 9 to 11 shown in Table 4. Thus, the data indicate that, in the case where the raw material contains 10% by mass or more of a plastically deformable metal and has an electrical conductivity of 11 χ 106 S / m or more, and the raw material is heated by electrical heating, the raw material is agglomerated when the pressure and temperature applied to Petition 870260024766, dated 03 / 17 / 2026, p. 25 / 74 20 / 22 raw material, satisfy the following inequality (3). P > 40 - (T - 500) / 10 (3) (Experimental Example 5)

[0043] In Experimental Example 5, the agglomeration of a raw material was carried out using the same procedure as in Experimental Example 3 or Experimental Example 4, except that the raw material used had a different component composition from that of the raw material used in Experimental Examples 1 to 4. The heating temperature and pressure of the raw material, the amount of metallic iron, and the results of the agglomeration evaluation in Experimental Example 5 are shown in Table 5 below. The raw material used in Experimental Example 5 had an average particle size not exceeding 1.0 mm and had the following component composition: Fe2O3 81.3% by mass, FeO 11.6% by mass, SiO2 4.2% by mass, CaO 0.4% by mass, Al2O3 0.2% by mass, the remainder being incidental impurities. The T. Fe was 65.9% by mass. The raw material used in Experimental Example 5 was iron ore powder that contained almost no calcium oxide.

[0044] Iron ore powder that did not contain metallic iron or raw material that contained metallic iron was prepared and filled into mold 7 under a nitrogen atmosphere and heated by electric heating at a rate of 200°C per minute to the target temperature. The heating temperature and pressure of the raw material, the amount of metallic iron, and the results of the agglomeration assessment in Experimental Example 5 are shown in Table 5 below. Petition 870260024766, dated 03 / 17 / 2026, page 26 / 74 21 / 22 [Table 5] Temperature (°C) Pressure (MPa) Heating method Amount of metallic iron (% by mass) included in the total Agglomeration Example of the invention 12 900 20 Electric heating 0 o Example of ref. 1 700 20 Electric heating 0 X Example of the invention 13 700 20 Electric heating 10 o

[0045] As shown in Table 5, in Invention Examples 12 and 13, the iron ore was agglomerated even though it contained almost no calcium oxide, which acts as a binder in the granulation of iron ore powder. The results confirmed that, just like raw material containing calcium oxide, even raw material not containing calcium oxide can be agglomerated by hot pressing. The results of Invention Example 13 also confirmed that, just like raw material containing calcium oxide, even raw material not containing calcium oxide can be agglomerated under conditions of 20 MPa pressure and 700°C heating temperature by adding 10% by mass of metallic iron to the raw material.

[0046] As described above, according to the agglomerated raw material production method of the present embodiments, a raw material containing iron oxide can be agglomerated at a lower temperature than conventional methods. This can reduce the energy consumption required to agglomerate the raw material. Furthermore, with the use of electric furnace heating or electric heating, a raw material can be heated without the addition of an agglomerating agent, such as coke powder, to the raw material and the combustion of the agglomerating agent. This can reduce the Petition 870260024766, dated 03 / 17 / 2026, page 27 / 74 22 / 22 is the amount of carbon dioxide generated in the production of an agglomerated raw material. List of reference signs for a double cylinder type pressure device: raw material containing iron oxide, sintered raw material, power supply device, anode, cathode, mold, punch.

Claims

1. A method for producing an agglomerated raw material, characterized in that it comprises pressing and heating a raw material containing iron oxide with a particle size smaller than a predefined particle size, thus agglomerating the raw material, wherein the raw material contains iron oxide in an amount greater than 50% by mass, wherein the raw material is heated by electrical heating, and wherein: a pressure during pressing and a temperature during heating satisfy the following inequality (2): P > 40 - (T - 700) / 10 (2) where P is the pressure (MPa) and T is the temperature (°C); or the raw material contains 10% by mass or more of a metal that deforms plastically and has an electrical conductivity of 11 χ 106S / m or more, and a pressure during pressing and a temperature during heating satisfy the following inequality (3): P > 40 - (T - 500) / 10 (3) where P is the pressure (MPa) and T is the temperature (°C).

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