Agglomerated raw material production method

Abstract

The invention relates to a method for producing agglomerated raw materials that can agglomerate raw materials at lower temperatures than conventional methods, thus allowing for a reduction in total energy consumption. The method for producing agglomerated raw materials consists of a pressing and heating step of iron oxide-containing raw materials with a particle size smaller than a predetermined particle size, thereby agglomerizing the raw materials. The raw materials contain iron oxide in an amount greater than 50% by mass. The raw materials are heated by electric heating.

Description

Manufacturing method of agglomerated raw material

[0001] The present invention relates to a method for producing agglomerated raw material, in which raw material containing powdery iron oxide is agglomerated.

[0002] In a pig iron production process in which raw materials containing powdered iron oxide are reduced using a blast furnace, shaft furnace, or the like, it is necessary to agglomerate the raw materials containing powdered iron oxide to ensure gas permeability within the furnace. As a technique for agglomerating raw material powder, Non-Patent Document 1 describes a manufacturing method for agglomerating powdered or granular raw material powder whose melting point or decomposition temperature and sintering temperature are close to each other. In this manufacturing method, silicon nitride is used as the raw material powder, and the raw material powder is agglomerated by hot pressing, in which the raw material powder is heated and pressurized. The raw material powder is heated by hot pressing by heating a mold into which the raw material powder is filled. Non-Patent Document 1 also describes that the mold can be heated by resistance heating, induction heating, or the like. Furthermore, the heating temperature of the silicon nitride raw material powder is set to 1800°C, which is close to the melting point of silicon nitride or 1900°C, the temperature at which silicon nitride begins to decompose. Furthermore, the pressure condition for silicon nitride in the hot press is set to 10 atmospheres. It is said that this allows the silicon nitride to be sintered without melting.

[0003] Yoneya Katsutoshi, "Sintering of Ceramics and Pressure Technology", Pressure Technology, 1992, Vol. 30, No. 2, pp. 60-68

[0004] In the method described in Non-Patent Document 1, as described above, silicon nitride, which is raw material powder, is heated under pressure to the melting point or decomposition temperature of silicon nitride. Because the heating temperature is high, the method described in Non-Patent Document 1 may consume a large amount of energy when agglomerating silicon nitride. Even when agglomerating raw materials to be used in a blast furnace or shaft furnace, it is preferable to agglomerate them at temperatures as low as possible compared to conventional methods.

[0005] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for manufacturing agglomerated raw materials that can agglomerate raw materials at a temperature lower than conventional methods, thereby reducing energy consumption.

[0006] The gist of the present invention for solving the above problems is as follows: [1] A method for manufacturing agglomerated raw materials by pressurizing and heating raw materials containing iron oxide having a particle size smaller than a predetermined size, the raw materials containing more than 50 mass% iron oxide, and heating the raw materials by electrical heating.

[0007] [2] The method for producing agglomerated raw materials according to [1], wherein the raw materials contain 10 mass % or more of a metal that undergoes plastic deformation.

[0008] [3] The method for producing agglomerated raw materials according to [2], wherein the raw materials are agglomerated by heating them to 700°C or higher while pressurizing them to 20 MPa or higher.

[0009] [4] The electrical conductivity of the metal is 11 x 10 ６ The method for producing agglomerated raw material according to [2] or [3], wherein the agglomerated raw material has a particle size of 0.5 μm or more.

[0010] [5] A method for producing agglomerated raw materials, which includes pressurizing and heating raw materials containing iron oxide having a particle size smaller than a predetermined size to form agglomerates, wherein the raw materials contain more than 50 mass% iron oxide, and the pressurizing pressure and the heating temperature satisfy the following formula (1): P≧40−(T−900) / 10 (1), where P is the pressure (MPa) and T is the temperature (°C).

[0011] [6] The method for producing agglomerated raw materials according to [5], wherein, when the raw materials are heated by electrical current heating, the pressure and the temperature satisfy the following formula (2) instead of formula (1): P≧40−(T−700) / 10 (2), where P is the pressure (MPa) and T is the temperature (°C).

[0012] [7] The raw material has an electrical conductivity of 11 x 10 ６The method for producing agglomerated raw material according to [5], wherein, when the raw material has a viscosity of 1000 MPa or more, contains 10 mass % or more of a metal that undergoes plastic deformation, and the raw material is heated by electrical current heating, the pressure and the temperature satisfy the following formula (3) instead of formula (1): P≧40−(T−500) / 10 (3) In formula (3), P is the pressure (MPa) and T is the temperature (°C).

[0013] According to the present invention, raw materials containing iron oxide can be agglomerated at a lower temperature than conventional methods, thereby reducing the overall amount of energy consumption.

[0014] 1 is a diagram schematically illustrating an example of a double-roll type pressure device to which the method for producing agglomerated raw materials according to an embodiment of the present invention can be applied.

[0015] The method for producing agglomerated raw materials according to an embodiment of the present invention is a method for agglomerating raw materials (hereinafter referred to as "raw materials") containing more than 50% by mass of iron oxide having a particle size smaller than a predetermined size. The method also agglomerates raw materials so that the raw materials can be used as raw materials in a pig iron production process using a blast furnace or a shaft furnace, for example. The predetermined particle size is the size used for raw materials in a pig iron production process using a blast furnace or a shaft furnace, and specifically, may be a particle size of 5 mm or more and less than 50 mm. Therefore, in this embodiment, the raw materials containing iron oxide having a particle size smaller than the predetermined particle size refer to raw materials including iron ore having a particle size smaller than 5 mm and return ore having a particle size smaller than 5 mm produced in a sintered ore production process. The raw materials may contain, in addition to the iron oxide as the main component, metal oxides such as silicon dioxide, calcium oxide, and aluminum oxide, and non-ferrous materials. The total amount of metal oxides and non-ferrous materials other than iron oxide is preferably 20% by mass or less of the raw materials. In this embodiment, the particle size is determined by a sieve. For example, iron ore having a particle size of less than 5 mm means iron ore that falls below the sieve size on a sieve with 5 mm openings.

[0016] In the method for producing agglomerated raw materials according to this embodiment, the raw materials are agglomerated by heating them to a target temperature while being pressurized to a target pressure. Specifically, the raw materials are agglomerated by increasing the pressure applied to the raw materials to the target pressure and increasing the temperature of the raw materials to the target temperature. The pressure and temperature of the raw materials may be increased to their target values ​​almost simultaneously. Alternatively, the raw materials may be agglomerated by increasing the temperature of the raw materials to the target temperature while the pressure has reached the target pressure, or by increasing the pressure of the raw materials to the target pressure while the temperature of the raw materials has reached the target temperature. The target pressure and target temperature are pressure and temperature at which the raw materials can be agglomerated, and can be determined experimentally. The pressure may be measured, for example, by measuring the pressure inside a container filled with the raw materials using a conventional pressure sensor, or may be calculated based on the load applied to the container to apply pressure to the raw materials. The temperature may be measured by measuring the temperature inside a container filled with the raw materials using a temperature sensor attached to the inner wall of the container.

[0017] The method for applying pressure to the raw materials may be a conventionally known pressurizing method. Specifically, for example, a double-roll system can be used. FIG. 1 is a schematic diagram illustrating an example of a double-roll system pressurizing device to which the agglomerated raw material manufacturing method according to the embodiment of the present invention can be applied. As shown in FIG. 1 , the double-roll system pressurizing device includes a pair of rolls 1 arranged with a predetermined clearance (not shown) therebetween, and having a plurality of molds (not shown) formed on the circumferential surfaces corresponding to the shapes of the molded product divided in half. The raw material 2 is filled into the molds of each roll 1, and the rolls 1 rotate, bringing the molds of each roll 1 closer to each other, thereby compressing the raw material 2. Alternatively, instead of using a double-roll system pressurizing device, the raw material 2 may be compressed using a tableting method in which the raw material 2 is filled into a space formed by a mold and a punch, and the punch is pressed into the space to compress the raw material 2.

[0018] The raw material 2 may be heated using an electric furnace, but it is preferable to heat the raw material 2 primarily by electrical heating. Electrical heating is a method of heating the raw material by passing electricity through it. In the double-roll pressure device shown in FIG. 1 , an anode 5 and a cathode 6 of a power supply 4 are connected to each of the rolls 1. This allows the raw material 2 to be electrically heated while being pressed by the double-roll pressure device shown in FIG. 1 .

[0019] Induction heating is a method of heating raw materials 2 by applying an alternating current to a conductor, thereby generating a magnetic field and generating a current in the raw materials 2. In this way, induction heating also involves passing electricity through the raw materials 2, so the term "resistance heating" in this embodiment includes both direct resistance heating and induction heating. In the double-roll pressurizing device shown in FIG. 1 , a magnetic field is generated around the device to generate a current in the raw materials 2, which then heats the raw materials. Furthermore, "mainly performed by resistance heating" means that when the raw materials 2 are heated using both resistance heating and other heating methods, the heat generated by the resistance heating accounts for 50% or more of the total heat generated by the raw materials 2. The aforementioned "heating method other than resistance heating" includes, for example, heating in an electric furnace or heating the raw materials using heat generated by burning a specific fuel.

[0020] As described above, according to the manufacturing method of agglomerated raw materials of this embodiment, the raw materials 2 are heated in a state where they are pressed or compressed against each other under pressure, and therefore, they can be heated in a state where the contact surface between particles is increased compared to when they are not pressurized. This promotes bonding of the raw materials 2, and even when the raw materials 2 contain 50 mass % or more of iron oxide, which is difficult to agglomerate, they can be agglomerated at a lower temperature than when they are not pressurized.

[0021] Furthermore, in the method for producing agglomerated raw materials according to this embodiment, it is preferable to add a granular or powdery metal that undergoes plastic deformation and has an electrical conductivity higher than that of iron to the raw materials 2 in order to facilitate agglomeration of the raw materials 2. Examples of the additive metal added to the raw materials 2 include copper, iron, and niobium. When the raw materials 2 to which these metals have been added are pressurized and heated as described above, the additive metal is pressed by the raw materials 2 and plastically deformed. The raw materials 2 are tightly adhered to each other via the plastically deformed additive metal, thereby strongly bonding the raw materials 2 together. In other words, since the additive metal functions as a binder, the raw materials 2 can be bonded together to obtain an agglomerated raw material 3 at a lower temperature than when the raw materials 2 do not contain the additive metal.

[0022] Increasing the amount of additive metal added to the raw materials 2 reduces the amount of iron oxide to be reduced. Because the agglomerated raw materials 3 are used as raw materials in a pig iron production process that involves gas reduction of the raw materials, a reduction in the amount of iron oxide contained in the agglomerated raw materials 3 is undesirable. Therefore, it is preferable to use raw materials 2 containing more than 50% by mass of iron oxide and to add as little additive metal as possible. Furthermore, the additive metal plastically deforms to bond the raw materials 2 together, while filling the gaps between the raw materials 2. Therefore, if the amount of additive metal added is too large, the permeability of the agglomerated raw materials 3 may decrease, potentially reducing the reducibility of the raw materials. Therefore, it is preferable to add as little additive metal as possible. For these reasons, the amount of additive metal added may be 10% by mass or more but less than 50% by mass, and preferably 10% by mass or more but less than 30% by mass.

[0023] When raw materials 2 are heated by applying an electric current while they are under pressure, electricity flows along the surface of the iron oxide. Then, as electricity flows through the contact points where the raw materials 2 come into contact with each other, the contact points are heated and the temperature is increased, causing the raw materials 2 to bond and become agglomerates. Because pressure is applied to the raw materials 2, the raw materials 2 are brought close to each other, narrowing the gaps between them. Air is present in these gaps, and in this state, the raw materials 2 are heated by direct application of an electric current. Specifically, the potential difference between the electrodes is increased. Because iron oxide, which is an insulator, and the above-mentioned air are present between the electrodes, it is thought that the potential difference breaks down the insulation of the air, causing electricity to flow along the surface of the raw materials 2. In the case of induction heating, an electric current is generated by a magnetic field generated by applying an alternating current to a conductor, and therefore it is thought that electricity flows along the surface of the raw materials 2.

[0024] Furthermore, when the above-mentioned metal is added to the raw materials 2, electricity flows through the added metal, increasing the amount of heat generated (Joule heat) in the metal. As a result, the amount of heat generated (Joule heat) at the contact points between the raw materials 2 is higher than when the added metal is not added to the raw materials 2, and the raw materials 2 are bonded together and agglomerated. Furthermore, since the heat-generating portion is mainly the added metal, the raw materials 2 can be bonded together and agglomerated without heating the entire raw materials 2 to the target temperature. In other words, if the temperature of the entire raw materials 2 including the added metal is made uniform, the raw materials 2 can be bonded together and agglomerated at an even lower temperature. By electrically heating in this manner, the raw materials 2 can be bonded together and agglomerated without heating the entire raw materials 2, thereby reducing the amount of energy consumed to agglomerate the raw materials 2. Furthermore, since the heating temperature can be lowered, the raw materials are easily heated and the heat resistance required for the form for agglomerating the raw materials can be reduced.

[0025] Conventionally, agglomerates such as coke powder are used to produce agglomerated ore, which is used as a raw material for blast furnaces and shaft furnaces, and the raw materials are agglomerated by burning the agglomerates. In contrast, in the method for producing agglomerated raw materials according to this embodiment, agglomerated ore can be produced by heating using an electric furnace or by electrical heating. By carrying out this production method, CO ２ This also has the effect of suppressing the occurrence of

[0026] The method for producing agglomerated raw materials according to this embodiment will be specifically described below using experimental examples in which agglomerated raw materials were produced on a laboratory scale. (Experimental Example 1) Return ores with a particle size of less than 5 mm were used as raw materials. The component composition of the return ores was Fe, ２ O ３ The total content of the powder was 74.8% by mass, FeO: 7.0% by mass, SiO2: 5.0% by mass, CaO: 10.0% by mass, and Al2O3: 1.5% by mass, with the remainder being unavoidable impurities. The total iron content was 57.7% by mass. Figure 2 shows the mold used in Experimental Example 1. The mold 7 shown in Figure 2 is cylindrical. The raw material was filled into the mold 7, and cylindrical punches 8 were inserted through openings on both sides of the mold in the axial direction to seal the raw material. The mold 7 and punch 8 were made of heat-resistant materials because they were heated to approximately 1100°C. Furthermore, the punch 8 was made of a conductive material because it needed to conduct electricity when heated electrically.

[0027] Next, the raw material was pressurized up to the target pressure and the pressurized state was maintained. In Experimental Example 1, the raw material was pressurized by pressing the punch 8 using an Autograph (registered trademark). The pressure applied to the raw material was calculated based on the compression load measured by the Autograph (registered trademark) and the cross-sectional area of ​​the mold 7. In Experimental Example 1, the raw material was pressurized by pressing the punch 8 with a compression load corresponding to the target pressure.

[0028] Thereafter, the mold 7 was heated to a predetermined target temperature. In Experimental Example 1, the temperature was increased to the target temperature at a rate of 200°C / min using an electric furnace. After the target temperature was reached, the pressurized and heated state was maintained for approximately 5 minutes. Whether the target temperature was reached was determined by providing a thermometer (not shown) on the inner surface of the mold 7, measuring the inner surface temperature of the mold 7 using the thermometer, and comparing the measured temperature with the target temperature.

[0029] After 5 minutes, the raw materials were removed from the mold 7 and evaluated for agglomeration. The evaluation of agglomeration was performed by dropping the agglomerated raw materials removed from the mold 7 from a height of 1.0 m and visually determining whether or not they broke. If the agglomerated raw materials removed from the mold 7 broke or chipped due to the impact of the drop, it was determined that the raw materials were not agglomerated. The evaluation results of the heating temperature, pressure, and agglomeration of the raw materials are shown in Table 1 below. In the table below, "◯" indicates that the raw materials were agglomerated, and "×" indicates that the raw materials were not agglomerated.

[0030]

[0031] As shown in Table 1, in Experimental Example 1, the raw materials were agglomerated under conditions of a pressure of 20 MPa and a heating temperature of 1100°C. On the other hand, even when the pressure was 20 MPa, the raw materials did not agglomerate under conditions below 1100°C. Furthermore, when the pressure was 40 MPa, the raw materials were agglomerated even at a heating temperature of 900°C, which is lower than 1100°C. From the results of Invention Examples 1 and 2 in Table 1, the following formula (1) can be derived. That is, there is a correlation between the pressure and heating temperature at which the raw materials are agglomerated, and it can be seen that the raw materials are agglomerated when the pressure and temperature applied to the raw materials satisfy the following formula (1): P≧40−(T−900) / 10 (1) In formula (1), P is the pressure (MPa) applied to the raw materials, and T is the temperature (°C) to which the raw materials are heated. When a predetermined pressure is applied to the raw materials, the minimum temperature at which the raw materials can be agglomerated can be determined by determining the minimum value of T that satisfies formula (1). Similarly, when the raw materials are heated to a predetermined temperature, the minimum pressure at which the raw materials can be agglomerated can be found by finding the minimum value of P that satisfies the above (1).

[0032] (Experimental Example 2) In Experimental Example 2, metallic iron was added to the raw materials in Experimental Example 1. Metallic iron means unoxidized iron, and in Experimental Example 2, metallic iron with a particle size of approximately 150 μm or less and a purity of 90% by mass was added to the raw materials. The raw materials and metallic iron were thoroughly mixed by stirring, and then filled into the mold 7. The heating temperature and pressure of the raw materials, the amount of metallic iron added, and the evaluation results of agglomeration in Experimental Example 2 are shown in Table 2 below. The raw materials were heated and pressurized using the same procedures as in Experimental Example 1.

[0033]

[0034] As shown in Table 2, in Example 4 of Experimental Example 2, the raw materials were agglomerated under conditions of a pressure of 20 MPa and a heating temperature of 1,000°C. These results show that by adding 10% by mass of metallic iron to the raw materials, the heating temperature at which the raw materials were agglomerated could be reduced by 100°C compared to Example 1 of Experimental Example 1. In addition, in Example 5, in which the amount of metallic iron added was increased to 20% by mass, the raw materials were agglomerated under conditions of a pressure of 20 MPa and a heating temperature of 1,000°C. These results show that the amount of metallic iron added to the raw materials should be 10% by mass or more.

[0035] These results are thought to be due to the fact that the metallic iron is pressed and plastically deformed by the application of pressure and heat to the raw materials, and the plastically deformed metallic iron functions as a binder, bonding the raw materials together via the metallic iron, resulting in agglomeration. In other words, it is thought that the metallic iron's function as a binder lowers the temperature at which the raw materials become agglomerated.

[0036] (Experimental Example 3) In Experimental Example 3, the raw materials were filled into a mold 7 in a nitrogen atmosphere, and the raw materials were agglomerated using the same procedure as in Experimental Example 1, except that the temperature of the raw materials was increased by 200°C per minute by electrical heating instead of using an electric furnace until the target temperature was reached. In Experimental Example 3, anodes 5 and cathodes 6 were connected to punches 8 inserted into openings on both sides of the mold 7 in a nitrogen atmosphere, and 3 kWh of power was applied in pulses from the power supply 4 to electrically heat the raw materials. The evaluation results of the heating temperature, pressure, and agglomeration of raw materials 2 in Experimental Example 3 are shown in 3 below.

[0037]

[0038] As shown in Table 3, in Example 7 of Experimental Example 3, the raw materials were agglomerated under conditions of a pressure of 20 MPa and a heating temperature of 900°C. This result shows that by electrically heating the raw materials, the heating temperature at which the raw materials are agglomerated can be reduced by 200°C compared to Example 1 of Experimental Example 1. Similarly, in Example 8 of Experimental Example 3, Raw Materials 2 were agglomerated under conditions of a pressure of 40 MPa and a heating temperature of 700°C, and it is clear that the heating temperature at which the raw materials are agglomerated can be reduced by 200°C compared to Example 2 of Experimental Example 1.

[0039] When the raw materials are electrically heated, the potential difference between the electrodes 5 and 6 causes insulation breakdown in the air in the gaps between the raw materials 2, causing electricity to flow along the raw material surfaces. The Joule heat generated by the flow of electricity selectively heats the raw material surfaces, and although the average temperature of the raw materials as a whole is low, the raw materials are bonded together at the locally heated surfaces, which is thought to be why the agglomeration temperature is lowered.

[0040] From the results of Examples 7 and 8 shown in Table 3, the following formula (2) can be derived. That is, when raw material 2 is electrically heated, it is found that the raw material will be agglomerated if the pressure and temperature applied to the raw material satisfy the following formula (2): P≧40−(T−700) / 10 (2) In the above formula (2), P is the pressure (MPa) to which the raw material is pressurized, and T is the temperature (°C) to which the raw material is heated. By finding the minimum value of T that satisfies the above formula (2), the lowest temperature at which the raw material can be agglomerated can be found.

[0041] In Experimental Example 4, the raw materials were agglomerated in the same manner as in Experimental Example 3, except that metallic iron, metallic copper, or metallic niobium was added to the raw materials. The heating temperature and pressure of the raw materials, the amount of metallic iron added, and the evaluation results of the agglomeration in Experimental Example 4 are shown in 4 below.

[0042]

[0043] As shown in Table 4, in Example 9 of Experimental Example 4, the raw materials were agglomerated under conditions of a pressure of 20 MPa and a heating temperature of 700°C. These results show that by adding 10% by mass of metallic iron to the raw materials and heating them electrically, the heating temperature at which the raw materials are agglomerated can be reduced by 400°C compared to Example 1 of Experimental Example 1. Furthermore, in Example 10, in which the metallic iron content was increased to 20% by mass, the raw materials were agglomerated under conditions of a pressure of 20 MPa and a heating temperature of 700°C. These results show that even when heating by electrical current, it is sufficient to add metallic iron to the raw materials in an amount of 10% by mass or more.

[0044] In Example 11, when 10 mass % of metallic copper was added to the raw materials, the raw materials were agglomerated under conditions of a pressure of 20 MPa and a heating temperature of 700°C. On the other hand, in Reference Example 3, when 10 mass % of metallic niobium was added to the raw materials, the raw materials were not agglomerated under conditions of a pressure of 20 MPa and a heating temperature of 700°C.

[0045] The heat generation amount due to electrical heating is calculated using the following formula (4): Q = V ２ / R (4) In the above formula (4), Q is the amount of heat generated (J), V is the voltage (V), and R is the electrical resistance (Ω).

[0046] From the above equation (4), it can be seen that when the voltage is constant, the heat generated by resistance heating of a metal with a high electrical conductivity is greater than that of a metal with a low electrical conductivity. The electrical conductivity of iron is 11 x 10 ６ S / m, and the electrical conductivity of copper is 64 x 10 ６ S / m, and the electrical conductivity of niobium is 7 x 10 ６ Considering that the electrical conductivity of the metal used as the additive is 11 x 10 S / m, the electrical conductivity of iron is ６ It can be said that the binder effect of a metal can be obtained regardless of the electrical conductivity of the metal, and therefore even when 10 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.

[0047] From the results of Examples 9 to 11 shown in Table 4, the following formula (3) can be derived.６ It can be seen that when the material contains 10 mass % or more of a metal that is plastically deformable and has a viscosity of S / m or more, is electrically heated, and the pressure and temperature applied to the material satisfy the following formula (3), the material will be agglomerated: P≧40−(T−500) / 10 (3)

[0048] (Experimental Example 5) In Experimental Example 5, raw materials with a different composition from the raw materials used in Experimental Examples 1 to 4 were used, and the raw materials were agglomerated in the same manner as Experimental Examples 1 and 2. The heating temperature, pressure, amount of metallic iron added, and evaluation results of agglomeration in Experimental Example 5 are shown in Table 5 below. The raw materials used in Experimental Example 5 had an average particle size of 1.0 mm or less and a composition of Fe ２ O ３ The total iron content was 65.9 mass%. In Experimental Example 5, iron ore powder containing almost no calcium oxide was used as the raw material.

[0049] Iron ore powder containing no metallic iron or raw material containing metallic iron was prepared, filled into a mold under a nitrogen atmosphere, and heated in an electric furnace at a rate of 200°C per minute to the target temperature. The heating temperature, pressure, amount of metallic iron added, and evaluation results of agglomeration for Experimental Example 5 are shown in Table 5 below.

[0050]

[0051] As shown in Table 5, in Examples 12 and 13, iron ore was agglomerated despite the fact that it contained almost no calcium oxide, which functions as a binder, when the iron ore powder was granulated. These results confirmed that raw materials not containing calcium oxide can be agglomerated by hot pressing, just like raw materials containing calcium oxide. Furthermore, in Example 13, it was confirmed that even raw materials not containing calcium oxide can be agglomerated under conditions of a pressure of 20 MPa and a heating temperature of 700°C, just like raw materials containing calcium oxide, by adding 10 mass% metallic iron to the raw materials.

[0052] As described above, according to the method for producing agglomerated raw materials of this embodiment, raw materials containing iron oxide can be agglomerated at a lower temperature than conventional methods. This reduces the amount of energy consumed for agglomerating the raw materials. Furthermore, by using heating in an electric furnace or electrical heating, a coagulating agent such as coke powder can be mixed with the raw materials and heated without burning the coagulating agent. This reduces the amount of carbon dioxide generated during the production of agglomerated raw materials.

[0053] 1 Roll of double-roll type pressure device 2 Raw material containing iron oxide 3 Agglomerated raw material 4 Power supply device 5 Anode 6 Cathode 7 Formwork 8 Punch

Claims

1. A method for manufacturing an agglomerated raw material by pressurizing and heating a raw material containing iron oxide with a particle size less than a preset particle size to form agglomerates, wherein the raw material contains more than 50% by mass of iron oxide and the raw material is heated by electric heating.

2. The method for manufacturing an agglomerated raw material according to claim 1, wherein the raw material contains 10% by mass or more of a metal that undergoes plastic deformation.

3. The method for manufacturing an agglomerated raw material according to claim 2, wherein the raw material is heated to 700 °C or higher while being pressurized to 20 MPa or higher to form agglomerates.

4. The electrical conductivity of the metal is 11 × 10 ６ S / m or more. The method for producing the agglomerated raw material according to claim 2 or claim 3.

5. A method for manufacturing an agglomerated raw material by pressurizing and heating a raw material containing iron oxide with a particle size less than a preset particle size to form agglomerates, wherein the raw material contains more than 50% by mass of iron oxide, and the pressure of the pressurization and the temperature of the heating satisfy the following formula (1). P ≧ 40 - (T - 900) / 10... (1) In formula (1), P is the pressure (MPa) and T is the temperature (°C).

6. When the heating of the raw material is electric heating, the pressure and the temperature satisfy the following formula (2) instead of formula (1). The method for manufacturing an agglomerated raw material according to claim 5. P ≧ 40 - (T - 700) / 10... (2) In formula (2), P is the pressure (MPa) and T is the temperature (°C).

7. The raw material has an electrical conductivity of 11 × 10 ６ S / m or more and contains 10% by mass or more of a metal that plastically deforms. When the heating of the raw material is electric heating, instead of the formula (1), the pressure and the temperature satisfy the following formula (3). The method for producing the agglomerated raw material according to claim 5. P ≧ 40 - (T - 500) / 10... (3) In the formula (3), P is the pressure (MPa) and T is the temperature (°C).

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