Method and system for producing reduced iron

Abstract

Disclosed is a technique for producing carbon-containing reduced iron by increasing the carbon concentration of metallic iron after a reduction process and cooling the metallic iron in a direct reduction process. The production method of carbon-containing reduced iron according to the present disclosure has a reduction process of bringing a reducing gas into contact with an iron oxide raw material to obtain metallic iron and a cooling process of cooling the metallic iron. The cooling process has a first process of bringing methane gas into contact with the metallic iron after the reduction process to carbonize the metallic iron, a second process of bringing CO gas into contact with the metallic iron after the first process to carbonize the metallic iron, and a third process of bringing methane gas or an inactive gas into contact with the metallic iron after the second process.

Description

Technical Field

[0001] This application discloses a method and system for manufacturing reduced iron. Background Technology

[0002] In the steel industry, as an alternative to the blast furnace process, direct reduction processes using reducing gases are being investigated to reduce CO2 emissions. For example, processes using vertical shaft furnaces have been studied as direct reduction processes (e.g., Patent Documents 1 and 2). In the direct reduction process, reducing gas is brought into contact with iron oxide feedstock to obtain reduced iron (Direct Reduced Iron (DRI)). Additionally, cooling gas is sometimes brought into contact with the reduced iron to cool it and increase its carbon concentration. By increasing the carbon concentration of the reduced iron, the melting temperature in the subsequent melting and smelting process is lowered, and the strength of the steel is ensured.

[0003] Existing technical documents Patent documents Patent Document 1: International Publication No. 2021 / 195160 Patent Document 2: Japanese Patent Application Publication No. 61-073805 Summary of the Invention

[0004] The problem that the invention aims to solve

[0005] As product forms of reduced iron, three types can be cited: Cold DRI (CDRI, room temperature direct reduced iron), Hot Briquetted Iron (HBI, hot-pressed iron), and Hot DRI (HDRI, hot direct reduced iron). When manufacturing CDRI via a direct reduction process, a technique is required to increase the carbon concentration of metallic iron while simultaneously cooling it after reducing the iron oxide raw material to obtain metallic iron. In existing technologies, there is room for improvement regarding the simultaneous cooling of the metallic iron while increasing its carbon concentration during the direct reduction process for manufacturing reduced iron.

[0006] means for solving problems

[0007] As a means to solve the above-mentioned problems, this application discloses the following several solutions.

[0008] <Option 1> A method for manufacturing reduced iron, which is a method for manufacturing carbon-containing reduced iron, comprising: The reduction process involves contacting reducing gas with iron oxide raw materials to obtain metallic iron; and The cooling process cools the iron metal. The cooling process includes: In the first step, after the reduction step, methane gas is brought into contact with the metallic iron to carbonize the metallic iron. In the second step, after the first step, CO gas is brought into contact with the metallic iron to carbonize it; and The third step involves bringing methane gas or an inactive gas into contact with the metallic iron after the second step.

[0009] <Option 2> A method for manufacturing reduced iron, which is the method for manufacturing reduced iron according to Scheme 1, wherein, The reduction process and the cooling process are carried out in a vertical furnace.

[0010] <Option 3> A method for manufacturing reduced iron, which is the method for manufacturing reduced iron according to Scheme 1, wherein, The reduction process is carried out in a vertical furnace. The cooling process is carried out in a cooling device located on the downstream side of the vertical furnace.

[0011] <Option 4> A method for manufacturing reduced iron, which is the method for manufacturing reduced iron according to Scheme 1, wherein, The reduction process and the first process are carried out in a vertical furnace. The second and third processes are carried out in a cooling device located downstream of the vertical furnace.

[0012] <Option 5> A method for manufacturing reduced iron, which is the method for manufacturing reduced iron according to scheme 3 or 4, wherein, The process includes a moving step, which moves the ferrous metal from the vertical furnace to the cooling device.

[0013] <Option 6> A method for manufacturing reduced iron, wherein the method for manufacturing reduced iron is any one of Schemes 1 to 5, wherein, The reducing gas contains hydrogen.

[0014] <Option 7> A method for manufacturing reduced iron, which is a method for manufacturing reduced iron according to any one of Schemes 1 to 6, wherein: The dehydration process dehydrates the exhaust gas from the reduction process to obtain recycled gas; and The heating process involves heating the circulating gas and hydrogen to obtain the reducing gas containing the circulating gas and hydrogen.

[0015] <Option 8> A method for manufacturing reduced iron, wherein the method for manufacturing reduced iron is any one of Schemes 1 to 7, wherein, The reaction gas between the metallic iron and the methane gas in the first step is discharged from the system downstream of the reduction step.

[0016] <Option 9> A method for manufacturing reduced iron, wherein the method for manufacturing reduced iron is any one of Schemes 1 to 8, wherein, In the first step, the reaction gas between the metallic iron and the methane gas is added to the reducing gas.

[0017] <Option 10> A method for manufacturing reduced iron, wherein the method for manufacturing reduced iron is any one of schemes 1 to 9, wherein, The reaction gas between the metallic iron and the CO gas in the second step is discharged from the system downstream of the first step.

[0018] <Option 11> A method for manufacturing reduced iron, wherein the method for manufacturing reduced iron is any one of Schemes 1 to 10, wherein, The methane gas or inactive gas that comes into contact with the metallic iron in the third step is discharged from the system downstream of the second step.

[0019] <Option 12> A system for manufacturing reduced iron, which is a system for manufacturing reduced iron containing carbon, comprising: The reduction section brings reducing gas into contact with iron oxide raw materials to obtain metallic iron; and The cooling section cools the iron metal. The cooling section has: Part 1 involves contacting methane gas with the metallic iron obtained in the reduction section to carbonize the metallic iron. Part 2, downstream of Part 1, involves contacting CO gas with the metallic iron to carbonize it; and In the third part, downstream of the second part, methane gas or an inactive gas is brought into contact with the metallic iron.

[0020] <Option 13> A system for manufacturing reduced iron, which is the system for manufacturing reduced iron of embodiment 12, wherein, The reduction section and the cooling section are located in a vertical furnace.

[0021] <Option 14> A system for manufacturing reduced iron, which is the system for manufacturing reduced iron of embodiment 12, wherein, The reduction section is located in a vertical furnace. The cooling section is located in the cooling device on the downstream side of the vertical furnace.

[0022] <Option 15> A system for manufacturing reduced iron, which is the system for manufacturing reduced iron of embodiment 12, wherein, The reduction section and the first part are located in a vertical furnace. The second and third parts are located in a cooling device situated downstream of the vertical furnace.

[0023] <Option 16> A system for manufacturing reduced iron, which is the system for manufacturing reduced iron described in embodiment 14 or 15, wherein, It is equipped with a moving device to move the ferrous metal from the vertical furnace to the cooling device.

[0024] <Option 17> A system for producing reduced iron, which is the system for producing reduced iron according to any one of claims 12 to 16, wherein the reducing gas comprises hydrogen.

[0025] <Option 18> A system for manufacturing reduced iron, which is a system for manufacturing reduced iron according to any one of claims 12 to 17, wherein it comprises: The dehydration device dehydrates the exhaust gas from the reduction section to obtain recirculated gas; and A heating device is used to heat the circulating gas and hydrogen to obtain the reducing gas containing the circulating gas and hydrogen.

[0026] <Option 19> A system for manufacturing reduced iron, which is the system for manufacturing reduced iron according to any one of schemes 12 to 18, wherein, Downstream of the reduction section is a first cooling gas outlet that discharges the reaction gas of the metallic iron and the methane gas in the first section to the outside of the system.

[0027] <Option 20> A system for manufacturing reduced iron, which is the system for manufacturing reduced iron according to any one of schemes 12 to 19, wherein, The reduction section is connected to the first part so that the reaction gas of the metallic iron and the methane gas in the first part is added to the reducing gas.

[0028] <Option 21> A system for manufacturing reduced iron, which is the system for manufacturing reduced iron according to any one of claims 12 to 20, wherein, Downstream of the first part is a second cooling gas outlet that discharges the reaction gas of the metallic iron and the CO gas in the second part to the outside of the system.

[0029] <Option 22> A system for manufacturing reduced iron, which is the system for manufacturing reduced iron according to any one of claims 12 to 21, wherein, Downstream of the second section is a third cooling gas outlet that discharges the methane gas or inactive gas in contact with the metallic iron in the third section to the outside of the system.

[0030] Invention Effects

[0031] According to the method and system for manufacturing reduced iron disclosed herein, in a direct reduction process, it is possible to cool the metallic iron while increasing its carbon concentration. According to the method and system for manufacturing reduced iron disclosed herein, for example, it is possible to manufacture CDRIs with increased carbon concentration. Attached Figure Description

[0032] Figure 1 This is a schematic diagram illustrating an example of a method and system for manufacturing reduced iron.

[0033] Figure 2 This is a schematic diagram illustrating an example of a method and system for manufacturing reduced iron.

[0034] Figure 3 This is a schematic diagram illustrating an example of a method and system for manufacturing reduced iron.

[0035] Figure 4 This is a schematic diagram illustrating an example of a method and system for manufacturing reduced iron.

[0036] Figure 5 This is a schematic diagram illustrating an example of a method and system for manufacturing reduced iron.

[0037] Figure 6 This is a schematic diagram illustrating an example of a method and system for manufacturing reduced iron.

[0038] Figure 7 This is a schematic diagram illustrating an example of a method and system for manufacturing reduced iron.

[0039] Figure 8 These are schematic diagrams used to explain the types and locations of gases introduced into the cooling section of the vertical furnace for Cases 1 through 4 respectively.

[0040] Figure 9 This is a schematic diagram illustrating the types and locations of gases introduced into the vertical furnace and cooling tower, respectively, for the purposes of Example 1.

[0041] Figure 10 This is a schematic diagram illustrating the types and locations of gases introduced into the vertical furnace and cooling tower, respectively, for the purposes of Example 2. Detailed Implementation

[0042] The following describes one embodiment of the reduced iron manufacturing method and system of this disclosure. However, the reduced iron manufacturing method and system of this disclosure are not limited to the following embodiment. It should be noted that in this application, "iron oxide raw material" refers to a raw material containing iron oxide before the reduction process. "Metallic iron" refers to the intermediate product from the reduction process to the end of the cooling process; for convenience, substances whose carbon concentration has been increased through carbonization, etc., are called "metallic iron." "Reduced iron" refers to the product obtained after the cooling process. Furthermore, in this application, "downstream side" refers to the downstream side in the reduced iron manufacturing process. That is, in the case of manufacturing carbon-containing reduced iron from iron oxide raw material via metallic iron, the iron oxide raw material side is the upstream side, and the carbon-containing reduced iron side is the downstream side.

[0043] 1. Methods for manufacturing reduced iron

[0044] like Figures 1-7 As shown, one embodiment of a method for manufacturing carbon-containing reduced iron includes: In reduction process S1, reducing gas is brought into contact with iron oxide raw material 10 to obtain metallic iron 20; and Cooling process S2, cooling the metallic iron 20.

[0045] Here, the cooling process S2 has the following features: In step S21, after reduction step S1, methane gas is brought into contact with metallic iron 20 to carbonize the metallic iron 20. In step S22, after step S21, CO gas is brought into contact with metallic iron 20 to carbonize the metallic iron 20; and In step S23, after step S22, methane gas or an inactive gas is brought into contact with metallic iron 20.

[0046] 1.1 Reduction Process

[0047] In reduction step S1, the reducing gas comes into contact with the iron oxide raw material 10. This results in a reduction reaction, yielding metallic iron 20. Figures 1-7 As shown, the reduction process S1 can be carried out, for example, within the vertical shaft furnace 100. Alternatively, the reduction process S1 can be carried out in a reduction apparatus other than the vertical shaft furnace 100 (e.g., a flow bed, a rotary kiln). In particular, when the reduction process S1 is carried out within the vertical shaft furnace 100, high efficiency can be expected.

[0048] 1.1.1 Iron oxide raw materials

[0049] Iron oxide raw material 10 contains iron oxide. Iron oxide raw material 10 may be, for example, one or more selected from iron ore pellets, iron ore, and sinter. In addition to iron oxide, iron oxide raw material 10 may also contain, for example, one or both of silica and alumina. Iron oxide raw material 10 may have a particle size distribution or a uniform particle size. The average particle size of iron oxide raw material 10 may be, for example, 5.0 mm or more and 30.0 mm or less, or 10.0 mm or more and 15.0 mm or less. It should be noted that "particle size of raw material" refers to the sieve diameter of raw material, and "average particle size of raw material" refers to the weighted average of the particle sizes of raw material. Specifically, the average particle size of raw material is determined as follows: The particle size distribution based on mass is obtained through a dry sieving test as described in JIS Z 8815:1995, and the average of the maximum and minimum particle sizes of each sieve is taken as the representative particle size, and a mass-weighted average is performed to determine the average particle size of the raw material. Iron oxide raw material 10 can be formed into pellets, powder, blocks, or other shapes.

[0050] When the reduction process S1 is performed in the vertical shaft furnace 100, the aforementioned iron oxide raw material 10 is supplied and filled into the vertical shaft furnace 100 through the raw material supply port 100a, forming a filling layer. The filling rate of the filling layer is not particularly limited and can be the same as in conventional reduced iron manufacturing methods using a vertical shaft furnace. The filling layer moves downwards inside the vertical shaft furnace 100. That is, inside the vertical shaft furnace 100, with the iron oxide raw material 10 substantially full, it gradually moves downwards due to falling, etc. Considering a single raw material particle in the filling layer, the particle can move continuously downwards at a certain speed, or it can move intermittently by repeatedly falling and stopping. Considering a single raw material particle in the filling layer, the average downward movement speed of that particle is not particularly limited. For example, the average movement speed can be adjusted according to the supply amount (supply rate) of the aforementioned raw material. When moving the filling layer downwards, a burden feeder or similar device can be used to prevent material suspension.

[0051] 1.1.2 Reducing Gas

[0052] The type of reducing gas is not particularly limited as long as it can reduce the iron oxide raw material 10. Especially when the reducing gas includes hydrogen, more significant effects can be expected from the technology disclosed herein. Hydrogen can be, for example, a gas obtained through water electrolysis, a gas obtained by separating (e.g., membrane separation) syngas (gas obtained by oxidizing coal or biomass with steam, air, or oxygen), a gas obtained by separating natural gas from gases modified using steam, carbon dioxide, etc., or a gas obtained by separating carbon dioxide (gas obtained by heating coal or biomass under anaerobic conditions). In addition to hydrogen, the reducing gas can also include gases other than hydrogen. Examples of gases other than hydrogen include CO gas, inert gases, CO2 gas, and water vapor. Examples of inert gases include nitrogen and argon. When the reducing gas contains hydrogen, the hydrogen concentration of the reducing gas can be, for example, 40% by volume or more and 100% by volume or less, 50% by volume or more and 100% by volume or less, 60% by volume or more and 100% by volume or less, 70% by volume or more and 100% by volume or less, or 80% by volume or more and 100% by volume or less. The supply temperature of the reducing gas (the temperature before it comes into contact with the iron oxide raw material 10) can be any temperature at which the reduction reaction with the iron oxide occurs, for example, 700°C or more. The temperature of the reducing gas is preferably 800°C or more and 1100°C or less.

[0053] When the reduction process S1 is carried out in the vertical shaft furnace 100, the reducing gas can be supplied from the side wall of the vertical shaft furnace 100 to the interior of the furnace. There is no particular limitation on the method of supplying the reducing gas. For example, a pipe or the like can be connected to the reducing gas supply port 110a provided on the side wall of the vertical shaft furnace 100, and the reducing gas can be supplied from the outside to the interior of the furnace through the pipe or the like.

[0054] 1.1.3 Metallic Iron

[0055] In reduction step S1, at least a portion of the iron oxide contained in the iron oxide raw material 10 is reduced, thereby obtaining a solid reactant containing metallic iron 20. In addition to metallic iron 20, the solid reactant may also contain unreduced residual iron oxide, silicon dioxide, aluminum oxide, etc. The temperature of the freshly reduced metallic iron 20 can be, for example, 700°C or higher. There is no particular upper limit to the temperature of the freshly reduced metallic iron 20, as long as it is a temperature suitable for carrying out the cooling step S2 described later. The temperature of the freshly reduced metallic iron 20 can be, for example, 1100°C or lower.

[0056] When the reduction process S1 is carried out in the vertical shaft furnace 100, the solid reactant containing metallic iron 20 can be recovered from the outlet 100b located at the lower part of the vertical shaft furnace 100 (below the supply position of the reducing gas).

[0057] 1.1.4 Vertical shaft furnace

[0058] When the reduction process S1 is performed in the vertical shaft furnace 100, the shape of the furnace body of the vertical shaft furnace 100 can be the same as that of a known vertical shaft furnace. For example, the furnace body of the vertical shaft furnace 100 can have a furnace top, a furnace bottom, and a cylindrical section (cylindrical section) forming the sidewall between the furnace top and the furnace bottom. In this case, the cylindrical section can have a main body and a reduced diameter section provided below the main body, where the inner diameter of the furnace can also decrease from top to bottom. The vertical shaft furnace 100 can also be equipped with a material distributor or the like to prevent the material from suspending when the raw material packing layer moves downward inside. In addition, the vertical shaft furnace 100 can also have supply ports 121a, 122a, 123a for supplying various cooling gases and discharge ports 121b, 122b, 123b for discharging various cooling gases at a position below the reducing gas supply port 110a. The various cooling gas supply ports can be provided on the sidewall of the furnace or at a position inside the sidewall of the furnace. Various cooling gas outlets can also be located on the side wall of the furnace. In addition, the vertical furnace 100 can have a raw material supply port 100a at the top or upper part of the furnace, or an outlet 100b for recovering metallic iron or reduced iron at the lower part or bottom of the furnace.

[0059] 1.2 Cooling Process

[0060] The temperature of the metallic iron 20 immediately after the reduction step S1 is, for example, approximately 700°C to 900°C. In the cooling step S2, the metallic iron 20 is cooled by contacting it with gas, and the metallic iron 20 is carbonized. That is, reduced iron 30 containing carbon is obtained. In this way, by carbonizing the metallic iron 20 to obtain reduced iron 30 containing carbon, the melting temperature in the next melting and smelting step is lowered, and the strength as steel is ensured.

[0061] In the cooling step S2, following (1) carbonization and cooling of metallic iron 20 with methane gas, carbonization of metallic iron 20 based on (2) CO gas is carried out, followed by (3) cooling of metallic iron 20 with methane gas or an inactive gas. According to the inventors' understanding, the carbonization reaction using methane gas is easily carried out in a high-temperature region above 700°C and is an endothermic reaction. On the other hand, the carbonization reaction using CO gas is most easily carried out between 400°C and 600°C and is an exothermic reaction. In the cooling step S2, methane gas is first brought into contact with the high-temperature metallic iron 20 obtained through the reduction step S1, thereby proceeding appropriately and efficiently as an endothermic reaction for carbonization. In addition, apart from the physical endothermic reaction caused by contact with methane gas, which has a high specific heat, the temperature of metallic iron 20 is easily reduced to a temperature suitable for the carbonization reaction using CO gas due to the endothermic reaction during carbonization. By contacting CO gas with the cooled metallic iron 20, the exothermic reaction, which is a carbon precipitation reaction, proceeds appropriately and efficiently, allowing the carbon concentration in the final reduced iron 30 to increase significantly. At this point, the temperature of the metallic iron 20 can either decrease or increase. For example, when the CO gas temperature is low, the temperature decrease caused by contact with CO gas predominates compared to the temperature increase caused by the exothermic reaction, resulting in a decrease in the temperature of the metallic iron 20. Then, by contacting the metallic iron 20 with methane gas or an inert gas, the temperature of the metallic iron 20 can be lowered to a temperature where it is difficult to re-oxidize, resulting in reduced iron 30 containing carbon (e.g., CDRI containing carbon). As described above, in the cooling step S2, by sequentially performing (1) carbonization using methane gas and (2) carbonization using CO gas, the carbon concentration in the reduced iron 30 increases compared to the case where each gas is contacted individually. Because the carbon concentration increases sufficiently in (1) and (2), cooling with methane gas or an inert gas in (3) does not require accompanying carbon precipitation. However, (3) cooling of methane gas or inactive gas can also be accompanied by carbon precipitation.

[0062] When the reduction process S1 is carried out inside a vertical shaft furnace, the cooling process S2 can be carried out either inside or outside the furnace. That is, as... Figure 1 As shown, the reduction process S1 and the cooling process S2 can also be carried out within the vertical furnace 100. Alternatively, as... Figure 2 As shown, the reduction process S1 can also be performed inside the vertical furnace 100, and the cooling process S2 can be performed in the cooling device 200 located downstream of the vertical furnace 100. Alternatively, as... Figure 3As shown, the first step S21, which involves reduction S1 and cooling S2, can be performed within the vertical shaft furnace 100, while the second step S22 and the third step S23, which involve cooling S2, can be performed in a cooling device 200 located downstream of the vertical shaft furnace 100. From the viewpoint of reducing equipment costs, it is preferable to perform the reduction step S1 and cooling step S2 within the vertical shaft furnace 100. On the other hand, when part or all of the cooling step S2 is performed in the cooling device 200, it is possible to prevent exhaust gases from the cooling device 200 from entering the vertical shaft furnace 100. For example, if the first step S21 of reduction S1 and cooling S2 is performed within the vertical shaft furnace 100, and the second step S22 and the third step S23 of cooling S2 are performed in a cooling device 200 located downstream of the vertical shaft furnace 100, it is possible to prevent exhaust gases (including CO gas and CO2 gas) from the second step S22 from entering the first step S21. As a result, the carbon precipitation reaction in the first step S21 can be performed more efficiently. Furthermore, the recycling (hydrogen recovery) of the exhaust gas from the reduction step S21 becomes easier. Consequently, CO2 can also be efficiently recovered from the second step S22. For example... Figure 2 and Figure 3 As shown, when part or all of the cooling process is carried out in the cooling device 200 located downstream of the shaft furnace 100, the method for producing reduced iron may include a moving process that moves metallic iron 20 from the shaft furnace 100 to the cooling device 200. Specifically, metallic iron 20 recovered from the discharge port 100b of the shaft furnace 100 can move to the metallic iron supply port 200a of the cooling device 200. When part or all of the cooling process S2 is carried out in the cooling device 200 located downstream of the shaft furnace 100, a cooling tower can be cited as a specific example of the cooling device 200. There is no particular limitation on the supply rate of metallic iron 20 to the cooling device 200. The metallic iron 20 supplied to the cooling device 200 may form a filling layer within the cooling device 200 or may float in the airflow. In particular, when the metallic iron 20 supplied to the cooling device 200 forms a filling layer within the cooling device 200, a higher effect can be expected.

[0063] The cooling process S2 includes a first process S21, a second process S22, and a third process S23. Furthermore, in this embodiment, as long as the temperature of the reduced iron 30 at the end of the cooling process S2 is lower than the temperature of the metallic iron 20 at the beginning of the cooling process S2, the temperature of the metallic iron 20 may also rise during the cooling process S2. For example, in the second process S22, an exothermic reaction may occur between the metallic iron 20 and CO gas, causing the temperature of the metallic iron 20 to rise.

[0064] 1.2.1 First Process

[0065] Step S21 corresponds to (1) above. That is, in step S21, after the reduction step S1 described above, methane gas comes into contact with metallic iron 20, and metallic iron 20 is carbonized. Metallic iron 20 is partially carbonized. When the reduction step S1 is carried out in a vertical shaft furnace, step S21 can be carried out in the vertical shaft furnace or outside the vertical shaft furnace (for example, in a cooling device installed downstream of the vertical shaft furnace). In step S21, the temperature of metallic iron 20 when in contact with methane gas is not particularly limited as long as it is sufficient to carry out the carbon precipitation reaction using methane gas. In step S21, for example, by contacting methane gas with metallic iron 20 at a temperature of 700°C or higher, the carbon precipitation reaction using methane gas can be carried out more appropriately, and metallic iron 20 can be cooled appropriately. In step S21, there is no particular upper limit to the temperature of metallic iron 20 when in contact with methane gas. The temperature of metallic iron 20 when in contact with methane gas can be, for example, 1100°C or lower. From the viewpoint that the carbon precipitation reaction utilizing methane gas can be carried out particularly significantly, the temperature of the metallic iron 20 in contact with methane gas in the first step S21 can be 710°C or higher and 1100°C or lower, 730°C or higher and 1100°C or lower, 750°C or higher and 1100°C or lower, 770°C or higher and 1100°C or lower, 790°C or higher and 1100°C or lower, 810°C or higher and 1100°C or lower, or 700°C or higher and 1070°C or lower. The temperatures are: above 700℃ and below 1040℃, above 700℃ and below 1000℃, above 700℃ and below 970℃, above 700℃ and below 940℃, above 700℃ and below 900℃, above 710℃ and below 1070℃, above 730℃ and below 1040℃, above 750℃ and below 1000℃, above 770℃ and below 970℃, above 790℃ and below 940℃, or above 810℃ and below 900℃. It should be noted that the "temperature of metallic iron 20" in step S21 refers to the average temperature along the radial direction of the vertical furnace or cooling tower. When the reduction process S1 and the first process S21 are performed using the same apparatus (e.g., a shaft furnace), the position (height position) P1 for measuring the "temperature of metallic iron 20" in the first process S21 is downstream (below) the position (height position) P2 where the reducing gas is blown in the reduction process S1 and within 1 m of that position P2. Alternatively, when the reduction process S1 and the first process S21 are performed in different apparatuses (e.g., the reduction process S1 is performed in a shaft furnace, and the first process S21 is performed in a cooling device located downstream of the shaft furnace), the position P1 for measuring the "temperature of metallic iron 20" in the first process S21 is set to be within 1 m downstream (below) from the metallic iron supply port of the apparatus performing the first process S21.The average temperature of the metallic iron 20 in the radial direction can be specified, for example, by setting a rod-shaped member in the radial direction of a shaft furnace or cooling tower, and installing multiple thermocouples on this member to measure multiple temperatures in the radial direction. That is, when the first process S21 is performed in a shaft furnace, the average temperature of the metallic iron 20 in the radial direction is specified by multiple thermocouples installed along the radial direction of the shaft furnace. Similarly, when the first process S21 is performed in a cooling tower, the average temperature of the metallic iron 20 in the radial direction is specified by multiple thermocouples installed along the radial direction of the cooling tower. Here, for example, assuming that the measured temperature between locations is linearly distributed in the radial direction, the temperature distribution T(r) in the radial direction can be represented by a combination of linear functions of r. In this case, the average temperature T... ave When measuring temperature at point N, the radius of measurement point i (i=1~N) is set as r. i , is defined by the following formula. It should be noted that, with respect to r0, r N+1 This corresponds to the center of the furnace (r0=0) and the furnace wall (r N+1 The temperature at the location (=R) is obtained by extrapolation. Using this method, even if a temperature distribution occurs along the radial direction, the average temperature along the radial direction can be determined by averaging multiple measured temperatures. The number of thermocouples is not particularly limited; for example, five or more are preferred. In the first step S21, the temperature of the methane gas in contact with the metallic iron 20 is not particularly limited. The temperature of the methane gas can, for example, be above 25°C and below 600°C.

[0066] [Mathematical Expression 1]

[0067] In step S21, the carbonization of metallic iron 20 can be carried out solely through the carbon evolution reaction of methane gas, or other gases can be brought into contact with metallic iron 20 along with methane gas. In other words, the gas in contact with metallic iron 20 in step S21 only needs to contain methane gas. Besides methane gas, the gas in contact with metallic iron 20 in step S21 can also contain hydrogen, nitrogen, CO gas, CO2 gas, water vapor, etc. For example, natural gas can be used as the gas in contact with metallic iron 20 in step S21. It should be noted that, as described above, in step S21, the temperature of metallic iron 20 is lowered by utilizing the carbon evolution reaction of methane gas (an endothermic reaction). In step S21, as long as this endothermic reaction utilizing methane gas predominates, a gas with an exothermic reaction (e.g., CO gas) can also be included in a portion of the gas in contact with metallic iron 20. However, when the gas in contact with the metallic iron 20 in the first step S21 contains CO gas, the volume proportion of CO gas is less than the volume proportion of methane gas. Furthermore, when the gas in contact with the metallic iron 20 in the first step S21 is composed of multiple gases, for example, methane gas has the largest volume proportion among all gases. The gas in contact with the metallic iron 20 in the first step S21 may contain, for example, 50% or more, 60% or more, or 70% or more of methane gas.

[0068] The reaction gas between metallic iron 20 and methane gas in step S21 can contain both methane and hydrogen gas. This reaction gas can be discharged from the system as exhaust gas and used as fuel, or it can be used as part of the reducing gas described above. For example, as... Figures 1-6 As shown, the reaction gas between metallic iron 20 and methane gas in step S21 can be discharged from the system downstream of reduction step S1. Alternatively, as... Figure 7 As shown, the reaction gas between metallic iron 20 and methane gas in the first step S21 can also be added to the aforementioned reducing gas. In other words, the reaction gas between metallic iron 20 and methane gas in the first step S21 can also be supplied to the reduction step S1. In particular, by adding the reaction gas in the first step S21 to the aforementioned reducing gas, efficient operation can be achieved while reducing the amount of reducing gas used.

[0069] 1.2.2 Second Process

[0070] Step S22 corresponds to (2) above. That is, in step S22, after step S21, CO gas comes into contact with metallic iron 20, and metallic iron 20 is carbonized. Metallic iron 20 is partially carbonized. In the case of reduction step S1 being carried out in a vertical shaft furnace, step S22 can be carried out in the vertical shaft furnace or outside the vertical shaft furnace (for example, in a cooling device installed downstream of the vertical shaft furnace). In addition, if step S21 is carried out outside the vertical shaft furnace, step S22 must also be carried out outside the vertical shaft furnace. In step S21, the temperature of metallic iron 20 when it comes into contact with CO gas is not particularly limited as long as the carbon precipitation reaction using CO gas can be carried out. In step S22, for example, by contacting CO gas with metallic iron 20 at a temperature of 400°C or higher and 600°C or lower, the above-mentioned carbon precipitation reaction using CO gas can be carried out more appropriately. From the viewpoint that the carbon precipitation reaction utilizing CO gas can be carried out particularly significantly, the temperature of the metallic iron 20 in contact with CO gas in the second step S22 can be 410°C or higher and 600°C or lower, 420°C or higher and 600°C or lower, 430°C or higher and 600°C or lower, 440°C or higher and 600°C or lower, 450°C or higher and 600°C or lower, 400°C or higher and 590°C or lower, 400°C or higher and 580°C or lower, 400°C or higher and 570°C or lower, 400°C or higher and 560°C or lower, 400°C or higher and 550°C or lower, 410°C or higher and 590°C or lower, 420°C or higher and 580°C or lower, 430°C or higher and 570°C or lower, 440°C or higher and 560°C or lower, or 450°C or higher and 550°C or lower. It should be noted that the "temperature of metallic iron 20" in the second step S22, like in the first step S21, refers to the average temperature in the radial direction of the shaft furnace or cooling tower. That is, when the second step S22 is performed in a shaft furnace, the average temperature of metallic iron 20 in a specific radial direction is measured using multiple thermocouples installed along the radial direction of the shaft furnace. Similarly, when the second step S22 is performed in a cooling tower, the average temperature of metallic iron 20 in a specific radial direction is measured using multiple thermocouples installed along the radial direction of the cooling tower. When the first step S21 and the second step S22 are performed in the same apparatus (e.g., a shaft furnace), the position (height position) P3 for measuring the "temperature of metallic iron 20" in the second step S22 is set downstream (below) of the position (height position) P4 where methane gas is blown in the first step S21, and within 1 m of that position (height position). Alternatively, if the first step S21 and the second step S22 are carried out in different devices (for example, the first step S21 is carried out in a shaft furnace, and the second step S22 is carried out in a cooling device located downstream of the shaft furnace), the position P3 for measuring the "temperature of metallic iron 20" in the second step S22 is set to a position within 1m downstream (downward) from the metallic iron supply port of the device carrying out the second step S22.In step S22, the temperature of the CO gas in contact with the metallic iron 20 is not particularly limited. The temperature of the CO gas can be, for example, above 25°C and below 400°C. When the temperature of the CO gas is within this range, the temperature decrease caused by contact with the CO gas is more dominant than the temperature increase caused by the exothermic reaction, and the temperature of the metallic iron 20 decreases in step S22.

[0071] In step S22, the carbonization of metallic iron 20 can be carried out solely through the carbon evolution reaction of CO gas, or other gases can be brought into contact with metallic iron 20 along with CO gas. In other words, the gas in contact with metallic iron 20 in step S22 only needs to contain CO gas. Besides CO gas, the gas in contact with metallic iron 20 in step S22 can also contain nitrogen, hydrogen, CO2 gas, etc. For example, the gas in contact with metallic iron 20 in step S22 can be converter gas (LDG). It should be noted that if the gas in contact with metallic iron 20 in step S22 contains methane gas, the volume proportion of methane gas is less than the volume proportion of CO gas. Furthermore, if the gas in contact with metallic iron 20 in step S22 consists of multiple gases, for example, CO gas has the largest volume proportion among all gases. For example, the gas in contact with metallic iron 20 in step S22 may contain 50% or more, 60% or more, or 70% or more of CO gas.

[0072] The reaction gas between metallic iron 20 and CO gas in step S22 can contain both CO gas and CO2 gas. This reaction gas can be discharged from the system and used as fuel, or it can be used as part of the cooling gas in step S21 described above. Specifically, as... Figures 1-7 As shown, the reaction gas of metallic iron 20 and CO gas in the second step S22 is discharged from the system downstream of the first step S21, thereby enabling a more appropriate endothermic reaction using methane gas and achieving efficient operation.

[0073] 1.2.3 Third Process

[0074] Step S23 corresponds to step (3) above. That is, in step S23, after step S22, methane gas or an inert gas comes into contact with metallic iron 20. If step S1 is carried out in a shaft furnace, step S23 can be carried out in the shaft furnace or outside the shaft furnace (for example, a cooling device installed on the downstream side of the shaft furnace). In addition, if step S22 is carried out outside the shaft furnace, step S23 must also be carried out outside the shaft furnace. As mentioned above, the carbon precipitation reaction in step S22 is an exothermic reaction, so the temperature of metallic iron 20 immediately after step S22 is unlikely to be a suitable temperature for CDRI. In other words, metallic iron 20 immediately after step S22 is in a state where it is easy to re-oxidize. By carrying out step S23 after step S22, the temperature of metallic iron 20 can be reduced to a suitable temperature for CDRI. In step S23, the temperature of metallic iron 20 when in contact with methane gas or an inert gas is not particularly limited. In step S23, for example, the temperature of the metallic iron 20 (below 400°C) can be lowered to a temperature suitable for CDRI by contacting methane gas or an inactive gas with the iron. It should be noted that the "temperature of the metallic iron 20" in step S23, like in steps S21 and S22, refers to the average temperature along the radial direction of the shaft furnace or cooling tower. That is, when step S23 is performed in a shaft furnace, the average temperature of the metallic iron 20 in a specific radial direction is measured using multiple thermocouples arranged along the radial direction of the shaft furnace. Similarly, when step S23 is performed in a cooling tower, the average temperature of the metallic iron 20 in a specific radial direction is measured using multiple thermocouples arranged along the radial direction of the cooling tower. When performing steps S22 and S23 using the same apparatus (e.g., a shaft furnace), the position (height position) P5 for measuring the "temperature of metallic iron 20" in step S23 is set downstream (below) of the position (height position) P6 where CO gas is blown in step S22, and within 1 m of that position (height position). Alternatively, when steps S22 and S23 are performed in different apparatuses (e.g., step S22 is performed in a shaft furnace, and step S23 is performed in a cooling device located downstream of the shaft furnace), the position P5 for measuring the "temperature of metallic iron 20" in step S23 is set within 1 m downstream (below) from the metallic iron supply port of the apparatus performing step S23. In step S23, the temperature of the methane gas or inert gas in contact with the metallic iron 20 is not particularly limited. The temperature of the methane gas or inert gas can be, for example, above 25°C and below 100°C.

[0075] In step S23, cooling of the metallic iron 20 with methane gas or an inert gas is sufficient; alternatively, other gases may be introduced into contact with the metallic iron 20 along with the methane gas or inert gas. In other words, in step S22, the gas in contact with the metallic iron 20 only needs to contain methane gas or an inert gas. In step S23, the gas in contact with the metallic iron 20 may contain hydrogen, water vapor, etc., in addition to methane gas or an inert gas. When the gas in contact with the metallic iron 20 in step S23 contains methane gas, although it depends on the temperature of the metallic iron 20, it may sometimes further carbonize the metallic iron 20. Examples of inert gases in step S23 include nitrogen gas, which does not substantially react with the metallic iron 20. When the gas in contact with the metallic iron 20 in step S23 consists of multiple gases, for example, the volume proportion of methane gas or the inert gas may be the largest among the various gases. In step S23, the gas that comes into contact with the metallic iron 20 contains, for example, 50% or more, 60% or more, or 70% or more of methane gas, or 50% or more, 60% or more, or 70% or more of inactive gas, or a total of 50% or more, 60% or more, or 70% or more of methane gas and inactive gas.

[0076] When methane gas is used in step S23, the exhaust gas from step S23 can contain both methane and hydrogen. This exhaust gas can be discharged from the system and used as fuel, used as part of the reducing gas described above, used as part of the gas in step S21 described above, or used as part of the gas in step S22 described above. On the other hand, when an inert gas is used in step S23, the exhaust gas from step S23 can contain the inert gas. This exhaust gas can be discharged from the system or reused as an inert gas in step S23. For example, as... Figures 1-7 As shown, the methane gas or inactive gas that comes into contact with metallic iron 20 in the third step S23 can be discharged from the system downstream of the second step S22.

[0077] 1.3 Reduced iron

[0078] After the reduction process S1 and cooling process S2 described above, carbon-containing reduced iron 30 (e.g., CDRI with increased carbon concentration) is produced. In addition to carbon and iron, the carbon-containing reduced iron 30 may also contain unreduced residual iron oxide, silica, alumina, etc. The carbon content of the reduced iron 30 may, for example, exceed 0% by mass and be less than 5% by mass. The temperature of the reduced iron 30 immediately after the third process S23 (the temperature of the reduced iron 30 at the outlet of the third process S23) may, for example, be less than 150°C or less than 80°C. When the reduction process S1 and cooling process S2 are performed in the shaft furnace 100, the reduced iron 30 may, for example, be recovered from the discharge port 100b provided at the lower part of the shaft furnace 100. When part or all of the cooling process S2 is performed in the cooling device 200, the reduced iron 30 may, for example, be recovered from the discharge port 200b provided at the lower part of the cooling device 200.

[0079] 1.4 Dehydration and Heating Processes

[0080] In addition to the reduction step S1 and cooling step S2 described above, the method for manufacturing reduced iron in this embodiment may include other steps. For example, one embodiment of the method for manufacturing reduced iron may include a dehydration step S3, in which the exhaust gas from the reduction step S1 is dehydrated to obtain a circulating gas. Alternatively, one embodiment of the method for manufacturing reduced iron may include a heating step S4, in which the exhaust gas from the reduction step S1 is heated, or the circulating gas obtained by dehydrating the exhaust gas is heated. Furthermore, the heating step S4 may be a step in which the exhaust gas from the reduction step S1, or the circulating gas obtained by dehydrating the exhaust gas, and hydrogen are heated to obtain a reducing gas containing one or both of the exhaust gas and the circulating gas, and hydrogen. Alternatively, the dehydration step S3 and the heating step S4 described above may be combined. For example, as... Figure 4 As shown, one embodiment of the method for manufacturing reduced iron may include: a dehydration step S3 in which the exhaust gas from the reduction step S1 is dehydrated to obtain a circulating gas; and a heating step S4 in which the circulating gas and hydrogen are heated to obtain a reducing gas containing the circulating gas and hydrogen.

[0081] 1.4.1 Dehydration process

[0082] In the dehydration step S3, the exhaust gas from the reduction step S1 is dehydrated to obtain recycled gas. Dehydration can be performed using a known dehydration apparatus 130. In the reduction step S1, water is generated through the reaction of the reducing gas with the iron oxide raw material 10. However, in the reduction step S1, the reducing gas is not necessarily 100% utilized. That is, the reducing gas and water remain together in the exhaust gas from the reduction step S1. By dehydrating this exhaust gas, recycled gas containing the reducing gas can be obtained.

[0083] 1.4.2 Heating Process

[0084] Although the recycle gas obtained through the dehydration step S3 contains reducing gas, its quantity is insufficient. Furthermore, the temperature of the recycle gas obtained through the dehydration step S3 is low, making direct use in the reduction step S1 inefficient. Therefore, in the heating step S4, for example, the recycle gas and hydrogen are heated to obtain a reducing gas containing both recycle gas and hydrogen. In other words, a reducing gas is obtained by heating and mixing hydrogen, which serves as a supplementary gas, with the recycle gas. In the heating step S4, the recycle gas and hydrogen can be mixed after heating, or heated after mixing. The hydrogen can be obtained through water electrolysis, membrane separation from syngas (gas obtained by steam modification and partial combustion of coal or biomass), etc. The heating step S3 can be performed using a known heating device 140.

[0085] 1.5 Hydrogen Separation Process

[0086] like Figure 5 As shown, one embodiment of the method for manufacturing reduced iron may include a hydrogen separation step to separate hydrogen contained in the exhaust gas of the first step S21. This allows, for example, the separation of hydrogen and methane gas contained in the exhaust gas of the first step S21. The hydrogen separated from the exhaust gas can, for example, be used as part of the aforementioned reducing gas. Additionally, the methane gas separated from the exhaust gas can, for example, be used as part of the methane gas in the first step S21. The hydrogen separation step can be implemented using a known hydrogen separation apparatus 400. The configuration of the hydrogen separation apparatus 400 is not particularly limited.

[0087] 1.6 CO2 gas separation process

[0088] like Figure 6 As shown, one embodiment of the method for manufacturing reduced iron may include a CO2 gas separation step, which separates CO2 gas contained in the exhaust gas of the second step S22. This allows, for example, the separation of CO2 gas and CO gas contained in the exhaust gas of the second step S22. The CO gas separated from the exhaust gas can, for example, be used as CO gas in the aforementioned second step S22. Furthermore, the CO2 gas separated from the exhaust gas can be discharged outside the system and recovered by a CO2 recovery device or the like. The CO2 gas separation step can be implemented using a known CO2 gas separation device 500. The configuration of the CO2 gas separation device 500 is not particularly limited.

[0089] 1.7 Other matters

[0090] As described above, in one embodiment of the reduced iron manufacturing method, the reduction step S1 and the cooling step S2 can also be performed within the shaft furnace 100. In this case, for example, the first step S21 is performed at a lower position than the reduction step S1 within the shaft furnace 100. In this case, such as Figure 7 As shown, in step S21, the reaction gas between metallic iron 20 and methane gas can rise directly inside the furnace and be added to the reducing gas in reduction step S1 for reduction. Additionally, as... Figures 1-7 As shown, the reaction gas between metallic iron 20 and CO gas in step S22 can also be discharged from the system downstream of step S21. With these configurations, CO and CO2 gases discharged from step S22 are removed from reduction step S1. That is, CO and CO2 gases are not mixed into the exhaust gas of reduction step S1, and the exhaust gas of reduction step S1 easily becomes only reducing gas (e.g., hydrogen) and water vapor. By performing a dehydration step S3 on such exhaust gas, it can be reused as reducing gas. It should be noted that methane gas remains in the reaction gas between metallic iron 20 and methane gas in step S21, but this methane gas can be decomposed in the reduction zone. Furthermore, this methane gas is diluted by merging with other gases in the reduction zone. That is, the exhaust gas of reduction step S1 contains almost no methane gas, and even if it does, it is only about 1% by volume. Therefore, there is almost no effect from the concentration of carbon-containing gases accompanying the circulation. In other words, it can be handled simply by partially discharging the reduced gas from the system, without the need for special CO2 removal processes during the recycling of the discharged gas.

[0091] In the manufacturing method disclosed herein, combinations are also possible. Figures 1-7 As shown. For example, in Figures 1-3 In the manufacturing method shown, the following can be performed: Figure 4 The dehydration process S4 and the heating process S5 shown can also be performed. Figure 5 The hydrogen separation process shown can also be carried out. Figure 6 The CO2 gas separation process shown is as follows: Figure 7 As shown, the reaction gas between metallic iron 20 and methane gas in the first step S21 can rise directly in the furnace and be added to the reducing gas in the reduction step S1, or they can be combined.

[0092] 2. Reduced iron manufacturing system

[0093] The technology disclosed herein also has the aspect of being a manufacturing system for carbon-containing reduced iron.

[0094] That is, such as Figures 1-7 As shown, one embodiment of a carbon-containing reduced iron manufacturing system includes: The reduction section 110 contacts the reducing gas with the iron oxide raw material 10 to obtain metallic iron 20; and The cooling section 120 cools the metal iron 20.

[0095] Here, the cooling section 120 has: Part 121, methane gas is brought into contact with metallic iron 20 obtained in reduction section 110, causing metallic iron 20 to carbonize; Part 2, 122, downstream of Part 1, 121, brings CO gas into contact with metallic iron 20 to carbide the metallic iron 20; and Part 3, 123, downstream of Part 2, 122, brings methane gas or an inactive gas into contact with metallic iron 20.

[0096] In this embodiment, the reduction process S1 is performed in the reduction unit 110, and the cooling process S2 is performed in the cooling unit 120. The reduction unit 110 and the cooling unit 120 are configured to be capable of performing the reduction process S1 and the cooling process S2, respectively. Figures 1-5 As shown, the reduction unit 110 may have a reducing gas supply port 110a for supplying reducing gas and an outlet port 110b for discharging the gas after the reduction reaction. Additionally, the first section 121 may have a first cooling gas supply port 121a for supplying cooling gas containing methane gas and a first cooling gas outlet 121b for discharging the reaction gas between metallic iron 20 and methane gas in the first section 121. Furthermore, the second section 122 may have a second cooling gas supply port 122a for supplying cooling gas containing CO gas and a second cooling gas outlet 122b for discharging the reaction gas between metallic iron 20 and CO gas in the second section 122. Moreover, the third section 123 may have a third cooling gas supply port 123a for supplying cooling gas containing methane gas or an inert gas and a third cooling gas outlet 123b for discharging the methane gas or inert gas that has come into contact with metallic iron 20 in the third section 123. The reduction unit 110 and the cooling unit 120 may be integrated or separate units. For example, such as Figure 1 As shown, the reduction section 110 and the cooling section 120 can also be provided in the vertical furnace 100. Alternatively, as... Figure 2 As shown, alternatively, the reduction section 110 can be located in the vertical furnace 100, and the cooling section 120 can be located in the cooling device 200 located downstream of the vertical furnace 100. Alternatively, as... Figure 3 As shown, alternatively, the reduction section 110 and the first part 121 of the cooling section can be disposed in the vertical furnace 100, and the second part 122 and the third part 123 of the cooling section can be disposed in the cooling device 200 on the downstream side of the vertical furnace 100. Figure 2 and 3As shown, when a cooling device 200 is installed downstream of the shaft furnace 100, the reduced iron manufacturing system may also include a moving device 300 for moving metallic iron 20 from the shaft furnace 100 to the cooling device 200. Specific examples of the moving device 300 include conveyors, trolleys, etc. From the viewpoint of reducing equipment costs, it is preferable that the reduction section 110 and the cooling section 120 are located in the shaft furnace 100. When a cooling device 200 is provided in the reduced iron manufacturing system, a cooling tower can be cited as a specific example of the cooling device 200.

[0097] Reducing gas can be supplied to the reduction section 110 via the reducing gas supply port 110a. Additionally, methane gas can be supplied to the first section 121 of the cooling section 120 via the first cooling gas supply port 121a. Furthermore, CO gas can be supplied to the second section 122 via the second cooling gas supply port 122a. Moreover, methane gas or an inactive gas can be supplied to the third section 123 via the third cooling gas supply port 123a. There are no particular limitations on the gas supply system; for example, the gas source and the supply port can be connected by piping. The type of reducing gas is as described above. The reducing gas may, for example, contain hydrogen. The type of gas supplied to the cooling section 120 is as described above.

[0098] In addition to the reduction section 110 and cooling section 120 described above, the reduced iron manufacturing system of this embodiment may also have other configurations. For example, one embodiment of the reduced iron manufacturing system may include a dehydration device 130 for dehydrating the exhaust gas from the reduction section 110 to obtain circulating gas. Alternatively, one embodiment of the reduced iron manufacturing system may include a heating device 140 for heating the exhaust gas from the reduction section 110, or for heating the circulating gas obtained by dehydrating the exhaust gas. Furthermore, the heating device 140 may be an apparatus that heats the exhaust gas from the reduction section 110 or the circulating gas obtained by dehydrating the exhaust gas, and hydrogen to produce a reducing gas containing one or both of the exhaust gas and the circulating gas, and hydrogen. Alternatively, the dehydration device 130 and the heating device 140 described above may be combined. For example, as... Figure 4 As shown, one embodiment of the manufacturing system may also include: a dehydration device 130 for dehydrating the exhaust gas from the reduction unit 110 to obtain a circulating gas, and a heating device 140 for heating the circulating gas and hydrogen to obtain a reducing gas containing the circulating gas and hydrogen. The dehydration device 130 and the heating device 140 are used to perform the dehydration step S3 and the heating step S4 described above, respectively. Details are as described above.

[0099] The exhaust system from the reduction section 110 and the cooling section 120 is also as described above. For example, such as... Figures 1-6As shown, in one embodiment, the manufacturing system may also have a first cooling gas outlet 121b downstream of the reduction section 110, which discharges the reaction gas of metallic iron 20 and methane gas in the first section 121 to the outside of the system. Alternatively, as... Figure 7 As shown, in one embodiment of the manufacturing system, the reduction unit 110 can be connected to the first part 121 by adding the reaction gas of metallic iron 20 and methane gas (equivalent to the reaction gas in the first step S21 described above) to the reducing gas. Alternatively, in another embodiment of the manufacturing system, a second cooling gas outlet 122b can be provided downstream of the first part 121 to discharge the reaction gas of metallic iron and CO gas (equivalent to the reaction gas in the second step S22 described above). Furthermore, in another embodiment of the manufacturing system, a third cooling gas outlet 123b can be provided downstream of the second part 122 to discharge the methane gas or inactive gas in contact with metallic iron 20 in the third part 123 to the outside of the system.

[0100] The temperatures of the metallic iron 20 in each of the reduction section 110 and the cooling section 120 are also as described above. For example, in one embodiment of the manufacturing system, the temperature of the metallic iron 20 in contact with methane gas in part 121 may be 700°C or higher and 900°C or lower. Alternatively, in another embodiment of the manufacturing system, the temperature of the metallic iron 20 in contact with CO gas in part 222 may be 400°C or higher and 600°C or lower. Furthermore, in another embodiment of the manufacturing system, the temperature of the metallic iron 20 in contact with methane gas or an inactive gas in part 323 may be less than 400°C.

[0101] Furthermore, in the manufacturing system disclosed herein, when a vertical shaft furnace 100 is used as the reduction section 110, the pressure at the top of the furnace is not particularly limited, but can be within the range of 0 MPa or more and 0.8 MPa or less. The pressure can be measured, for example, using a pressure gauge installed at the top of the furnace.

[0102] Furthermore, in the manufacturing system disclosed herein, when a cooling tower is used as the cooling unit 120, the pressure at the top of the cooling tower is not particularly limited and can be within the range of 0 MPa or more and 0.8 MPa or less. The pressure can be measured, for example, using a pressure gauge installed at the top of the cooling tower.

[0103] In the manufacturing system disclosed herein, combinations are also possible. Figures 1-7 As shown. For example, in Figure 1 The manufacturing system shown can also be combined Figure 3 The dehydration device 130 and the heating device 140 are shown as shown.

[0104] 3. Effects

[0105] As described above, according to the manufacturing method and manufacturing system of this embodiment, based on obtaining metallic iron 20 by reducing iron oxide raw material 10, (1) carbonization and cooling of metallic iron 20 using methane gas are performed, followed by (2) carbonization of metallic iron 20 using CO gas, and then (3) cooling of metallic iron 20 using methane gas or an inactive gas, thereby enabling efficient manufacturing of reduced iron 30 containing carbon (e.g., CDRI with increased carbon concentration).

[0106] Example Hereinafter, embodiments are shown and the invention is further described, but the invention is not limited to the following embodiments. Various conditions can be adopted without departing from the spirit of the invention. In the following embodiments, conditions for increasing the carbonization of reduced iron by numerical simulation were investigated. The numerical simulation in this embodiment was conducted using a vertical shaft furnace mathematical model developed from the blast furnace mathematical model described in Non-Patent Document 1 below, with the reactions described as (7), (9), and (10) added in Non-Patent Document 2 below.

[0107] Non-patent literature 1: Nishioka et al., “Development of mathematical model for blast furnace”, Nippon Steel & Sumitomo Metal Technical Report No. 410 (2018) Non-patent literature 2: Hamzeh Hamadeh et al., "Detailed Modeling of the Direct Reduction of Iron Ore in a Shaft Furnace", Materials 2018, 11(10), 1865 (https: / / doi.org / 10.3390 / ma11101865)

[0108] 1. Research on the use of vertical shaft furnaces for reduction and cooling processes.

[0109] 1.1 Simulation Method

[0110] Numerical simulations assuming operation in a vertical shaft furnace were performed. First, H2 at 950°C was blown into the iron oxide pellets fed into the furnace to initiate a reduction reaction. The temperature of the metallic iron immediately after the reduction reaction was 858°C. Then, for Case 2 and Case 4 (examples), CH4 at 25°C was blown into the metallic iron to cool it while simultaneously causing carbon precipitation. Next, CO gas at 25°C was blown in from below the CH4 inlet to allow carbon precipitation of CO. Then, for Case 1, Case 2, Case 3, and Case 4, CH4 was blown in from below to lower the temperature to the target temperature for CDRI.

[0111] 1.2 Calculation Conditions

[0112] exist Figure 8 The types and locations of gases introduced into the cooling section of the vertical furnace are shown for Cases 1-4. Additionally, Figure 8 The structure shown is the structure of the left half of the furnace when the internal structure in a cross-section passing through and along the central axis of the vertical furnace is divided into a right half and a left half by the central axis of the vertical furnace. Regarding Case 2 and Case 4, Figure 8 The reduction zone corresponds to reduction step S1, the transfer zone corresponds to step S21 of cooling step S2, the upper part of the cooling zone corresponds to step S22 of cooling step S2, and the lower part of the cooling zone corresponds to step S23 of cooling step S2. In Case 2 and Case 4, the exhaust gas from step S21 is directly introduced into reduction step S1. Furthermore, the exhaust gas from step S22 is extracted from the downstream side of step S21 and discharged from the system. Additionally, the exhaust gas from step S23 is directly used as the cooling gas for step S22.

[0113] Details regarding Cases 1-4 are as follows.

[0114] Case 1 (Comparative Example): Without performing steps S21 and S22, the third step S23 is performed at 1400 Nm. 3 CH4 is blown in at a flow rate of / min, thereby reducing the temperature of the reduced iron exiting from step S23 to the target temperature for CDRI. The pressure at the top of the vertical furnace is set to 0.04MPa (gauge pressure).

[0115] Case 2 (Example): In the first step S21, at 300 Nm 3 CH4 is blown in at a flow rate of / min, and in the second process S22, it is blown in at a flow rate of 700Nm. 3 CO is blown in at a flow rate of / min, and in the third process S23, it is 1500Nm 3 CH4 is blown in at a flow rate of / min, thereby reducing the temperature of the reduced iron exiting from step S23 to the target temperature for CDRI. The pressure at the top of the vertical furnace is set to 0.04MPa (gauge pressure).

[0116] Case 3 (Comparative Example): The same as Case 1 except that the pressure at the top of the vertical furnace is changed to 0.7 MPa (gauge pressure).

[0117] Case 4 (Example): In the first step S21, at 300 Nm 3 CH4 is blown in at a flow rate of / min, and in the second process S22, it is blown in at 500Nm. 3 CO is blown in at a flow rate of / min, and in the third process S23, it is 1850Nm 3CH4 is blown in at a flow rate of / min, thereby reducing the temperature of the reduced iron exiting from step S23 to the target temperature for CDRI. The pressure at the top of the vertical furnace is set to 0.7MPa (gauge pressure).

[0118] 1.3 Calculation Results 1

[0119] The calculation results for Case 1 and Case 2 are shown in Table 1 below.

[0120]

[0121] The results in Table 1 show the following: It should be noted that in Cases 1 and 2, the reduction rate of the reduced iron in the product was 93-94%, ensuring a high reduction rate.

[0122] In Case 1 (Comparative Example), the reduced iron was discharged in a cooled state, but insufficient carbonization was achieved.

[0123] In Case 2 (Example), the amount of carbonized iron discharged is high (carbon concentration), and the discharge temperature can also be reduced to a practically low temperature.

[0124] The calculation results for Case 3 and Case 4 are shown in Table 2 below.

[0125]

[0126] The results in Table 2 show the following: Furthermore, in Cases 3 and 4, the reduction rate of reduced iron in the product was 93-94%, ensuring a high reduction rate.

[0127] In Case 3 (Comparative Example), the reduced iron was discharged in a cooled state, but insufficient carbonization was achieved.

[0128] In Case 4 (Example), the amount of carbonized iron discharged is high (carbon concentration), and the discharge temperature can also be reduced to a practically low temperature.

[0129] 1.4 Calculation Results 2

[0130] In Case 2, the amount of CH4 blown in Step 1 S21 was changed to achieve a temperature of approximately 400-600°C for the metallic iron after Step 1 S21 (Case 5-11), and the amount of carbide in the discharged reduced iron was investigated. Regarding Case 5-11, the flow rate of CH4 blown in Step 1 S21 is as follows. The calculation conditions and results are shown in Table 3.

[0131]

[0132] As shown in Table 3, it can be seen that when the temperature of the metallic iron after the first process is above 400°C and below 600°C, preferably above 450°C and below 550°C, the carbon concentration of the final reduced iron becomes particularly high. It should be noted that for any of Cases 5 to 11, the reduction rate in the product reduced iron is 92% to 94%, ensuring a high reduction rate.

[0133] 1.5 Calculation Results 3

[0134] In Case 2, the amount of CH4 blown in step S21 is changed to maintain the temperature of the metallic iron after step S21 at approximately 400-600°C, and nitrogen (flow rate: 1700 Nm³) is used instead of CH4 in step S23. 3 The same calculation was performed under the condition of ( / min) (Case 12~15). The calculation conditions and results are shown in Table 4.

[0135]

[0136] As shown in Table 4, even when inert gases such as nitrogen are used in step 3 (S23), the carbon concentration of the final reduced iron is almost not reduced. It should be noted that for any of Cases 12-15, the reduction rate in the product reduced iron is 92-94%, ensuring a high reduction rate.

[0137] 2. A study on the use of a vertical shaft furnace for the reduction process and a cooling tower for the cooling process.

[0138] 2.1 Simulation Condition 1

[0139] 2.1.1 Comparative Example 1

[0140] The simulation conditions for Comparative Example 1 were the same as those for Case 1 above. First, H2 at 950°C was blown into the iron oxide pellets fed into the shaft furnace to carry out a reduction reaction. The temperature of the metallic iron immediately after the reduction reaction was 858°C. Then, CH4 at 25°C was blown into the metallic iron to cool it while carbon was being deposited, yielding reduced iron as the product. The shaft furnace top pressure was set to 0.04 MPa (gauge pressure). The CH4 supply rate, the temperature of the reduced iron product, and the carbon concentration are shown in Table 5 below.

[0141] 2.1.2 Example 1

[0142] Numerical simulations were performed assuming the combined operation of the vertical shaft furnace and cooling tower. Figure 9 This indicates the type and location of the gas introduced into the vertical shaft furnace and cooling tower, respectively. Additionally, Figure 9The structure shown is the left half of the furnace structure, divided into right and left halves by the central axis of the shaft furnace and cooling tower. First, 950°C H2 is blown into the iron oxide pellets fed into the shaft furnace for reduction. The temperature of the ferrous iron immediately after the reduction reaction is 858°C. Then, 25°C CH4 is blown into the ferrous iron to cool it while carbon is being released. The temperature of the ferrous iron at the outlet side of the shaft furnace is 533.6°C. The amount of CH4 supplied to the shaft furnace is shown in Table 5 below. Next, the ferrous iron recovered from the outlet side of the shaft furnace is fed into the top of the cooling tower. 25°C CO is blown into the downstream side of the top to release carbon, and 25°C CH4 is blown into the further downstream side to cool the ferrous iron, yielding reduced iron as the product. The pressure at the top of the shaft furnace and the top of the cooling tower are set to 0.04 MPa (gauge pressure). The supply of CO and CH4 in the cooling tower, the temperature of the reduced iron product, and the carbon concentration are shown in Table 5 below.

[0143] 2.1.3 Example 2

[0144] like Figure 10 As shown, 100% of the cooling exhaust gas from the CO supply point and the CH4 supply point in the cooling tower will be extracted using CH4 cooling exhaust gas. Otherwise, the simulation will be performed in the same manner as in Example 1. The supply amounts of CO and CH4 in the cooling tower, the temperature of the reduced iron product, and the carbon concentration are shown in Table 1 below.

[0145] 2.2 Calculation Results

[0146] Table 5 below shows the calculation results for Comparative Example 1, Example 1, and Example 2. It should be noted that the reduction rate of the reduced iron in Comparative Example 1, Example 1, and Example 2 is all above 93%.

[0147]

[0148] The following can be seen from the results shown in Table 5.

[0149] As in Comparative Example 1, simply reducing the iron oxide feedstock and cooling the metallic iron using methane gas in a shaft furnace cannot sufficiently increase the carbon concentration of the reduced iron product. In contrast, as in Examples 1 and 2, reducing the iron oxide feedstock and cooling the metallic iron are performed in a shaft furnace. Then, in a cooling tower separate from the shaft furnace, the metallic iron is carbonized using CO gas. Furthermore, the metallic iron is cooled using methane gas downstream of the cooling unit, thereby increasing the carbon concentration of the reduced iron product. That is, it is possible to efficiently produce reduced iron containing carbon (e.g., CDRI with increased carbon concentration). In particular, as in Example 2, by extracting CH4-based cooling exhaust gas between the CO supply point and the CH4 supply point in the cooling tower, the carbon concentration of the reduced iron product is further increased. Additionally, as in Examples 1 and 2, by providing separate shaft furnaces and cooling towers, it is possible to prevent exhaust gas from the cooling tower from entering the shaft furnace.

[0150] 2.3 Simulation Condition 2

[0151] Comparative Example 2 was conducted under the same conditions as Case 3 above, except that the pressure at the top of the vertical furnace was set to 0.7 MPa (gauge pressure). Example 3 was conducted under the same conditions as Example 1, except that the pressure at the top of the vertical furnace was set to 0.7 MPa (gauge pressure). Example 4 was conducted under the same conditions as Example 1, except that the pressure at the top of the vertical furnace and the pressure at the top of the cooling tower were both set to 0.7 MPa (gauge pressure).

[0152] 2.4 Calculation Results

[0153] Table 6 below shows the calculation results for Comparative Example 2, Example 3, and Example 4. It should be noted that the reduction rate of the reduced iron in Comparative Example 2, Example 3, and Example 4 is all above 93%.

[0154]

[0155] The following can be seen from the results shown in Table 6.

[0156] As in Comparative Example 2, simply reducing the iron oxide feedstock and cooling the metallic iron using methane gas in a shaft furnace cannot sufficiently increase the carbon concentration of the reduced iron product. In contrast, as in Examples 3 and 4, reducing the iron oxide feedstock and cooling the metallic iron are performed in a shaft furnace. Then, in a cooling tower separate from the shaft furnace, the metallic iron is carbonized using CO gas. Furthermore, the metallic iron is cooled using methane gas downstream of the cooling unit, thereby increasing the carbon concentration of the reduced iron product. That is, it is possible to efficiently produce reduced iron containing carbon (e.g., CDRI with increased carbon concentration). Additionally, as in Examples 3 and 4, by providing separate shaft furnaces and cooling towers, it is possible to prevent exhaust gas from the cooling tower from entering the shaft furnace.

[0157] It should be noted that the same calculations were performed for the case where nitrogen was used instead of CH4 in the cooling tower, and the results showed the same trend as those shown in Table 5. That is, even when inactive gases such as nitrogen are used in the cooling tower, the reduction in carbon concentration of the final reduced iron is less.

[0158] 3. Conclusion

[0159] The results above show that carbon-containing reduced iron can be efficiently manufactured through the following reduction and cooling processes.

[0160] In the reduction process, reducing gas is brought into contact with iron oxide raw material to obtain metallic iron. In the cooling process, the metallic iron is cooled. Here, the cooling process includes: a first step, after the reduction process, contacting methane gas with the metallic iron to carbonize the metallic iron; a second step, after the first step, contacting CO gas with the metallic iron to carbonize the metallic iron; and a third step, after the second step, contacting methane gas or an inert gas with the metallic iron.

[0161] Explanation of reference numerals in the attached figures 10. Iron oxide raw materials 20 Metallic Iron 30 Reduced iron containing carbon 100 vertical shaft furnace 100a Raw material supply port 100b discharge outlet 110 Restoration Department 110a Reducing Gas Supply Port 110b Reducing gas outlet 120 Cooling Section 121 Part 1 121a First Cooling Gas Supply Port 121b First Cooling Gas Exhaust Port 122 Part 2 122a Second Cooling Gas Supply Port 122b Second Cooling Gas Exhaust Port 123 Part 3 123a Third Cooling Gas Supply Port 123b Third Cooling Gas Exhaust Port 200 Cooling device

Claims

1. A method for manufacturing reduced iron, which is a method for manufacturing carbon-containing reduced iron, comprising: The reduction process involves contacting reducing gas with iron oxide raw materials to obtain metallic iron; and The cooling process cools the iron metal. The cooling process includes: In the first step, after the reduction step, methane gas is brought into contact with the metallic iron to carbonize the metallic iron; In the second step, after the first step, CO gas is brought into contact with the metallic iron to carbonize it; and The third step involves bringing methane gas or an inactive gas into contact with the metallic iron after the second step.

2. A method for manufacturing reduced iron, which is the method for manufacturing reduced iron according to claim 1, wherein, The reduction process and the cooling process are carried out in a vertical furnace.

3. A method for manufacturing reduced iron, which is the method for manufacturing reduced iron according to claim 1, wherein, The reduction process is carried out in a vertical furnace. The cooling process is carried out in a cooling device located on the downstream side of the vertical furnace.

4. A method for manufacturing reduced iron, which is the method for manufacturing reduced iron according to claim 1, wherein, The reduction process and the first process are carried out in a vertical furnace. The second and third processes are carried out in a cooling device located downstream of the vertical furnace.

5. A method for manufacturing reduced iron, which is the method for manufacturing reduced iron according to claim 3 or 4, wherein, The process includes a moving step, which moves the ferrous metal from the vertical furnace to the cooling device.

6. A method for manufacturing reduced iron, comprising the method for manufacturing reduced iron according to any one of claims 1 to 5, wherein, The reducing gas contains hydrogen.

7. A method for manufacturing reduced iron, comprising the method for manufacturing reduced iron according to any one of claims 1 to 6, wherein, have: The dehydration process dehydrates the exhaust gas from the reduction process to obtain recycled gas; and The heating process involves heating the circulating gas and hydrogen to obtain the reducing gas containing the circulating gas and hydrogen.

8. A method for manufacturing reduced iron, comprising the method for manufacturing reduced iron according to any one of claims 1 to 7, wherein, The reaction gas between the metallic iron and the methane gas in the first step is discharged from the system downstream of the reduction step.

9. A method for manufacturing reduced iron, comprising the method for manufacturing reduced iron according to any one of claims 1 to 8, wherein, In the first step, the reaction gas between the metallic iron and the methane gas is added to the reducing gas.

10. A method for manufacturing reduced iron, comprising the method for manufacturing reduced iron according to any one of claims 1 to 9, wherein, The reaction gas between the metallic iron and the CO gas in the second step is discharged from the system downstream of the first step.

11. A method for manufacturing reduced iron, comprising the method for manufacturing reduced iron according to any one of claims 1 to 10, wherein, The methane gas or inactive gas that comes into contact with the metallic iron in the third step is discharged from the system downstream of the second step.

12. A system for manufacturing reduced iron, which is a system for manufacturing reduced iron containing carbon, comprising: The reduction section brings reducing gas into contact with iron oxide raw materials to obtain metallic iron; and The cooling section cools the iron metal. The cooling section has: In Part 1, methane gas is brought into contact with the metallic iron obtained in the reduction section to carbonize the metallic iron. Part 2, downstream of Part 1, involves contacting CO gas with the metallic iron to carbonize it; and In the third part, downstream of the second part, methane gas or an inactive gas is brought into contact with the metallic iron.

13. A system for manufacturing reduced iron, which is the system for manufacturing reduced iron according to claim 12, wherein, The reduction section and the cooling section are located in a vertical furnace.

14. A system for manufacturing reduced iron, which is the system for manufacturing reduced iron according to claim 12, wherein, The reduction section is located in a vertical furnace. The cooling section is located in the cooling device on the downstream side of the vertical furnace.

15. A system for manufacturing reduced iron, which is the system for manufacturing reduced iron according to claim 12, wherein, The reduction section and the first part are located in a vertical furnace. The second and third parts are located in a cooling device situated downstream of the vertical furnace.

16. A system for manufacturing reduced iron, which is the system for manufacturing reduced iron according to claim 14 or 15, wherein, It is equipped with a moving device to move the ferrous metal from the vertical furnace to the cooling device.

17. A system for manufacturing reduced iron, which is the system for manufacturing reduced iron according to any one of claims 12 to 16, wherein, The reducing gas contains hydrogen.

18. A system for manufacturing reduced iron, which is the system for manufacturing reduced iron according to any one of claims 12 to 17, wherein, have: The dehydration device dehydrates the exhaust gas from the reduction section to obtain recirculated gas; and A heating device is used to heat the circulating gas and hydrogen to obtain the reducing gas containing the circulating gas and hydrogen.

19. A system for manufacturing reduced iron, which is the system for manufacturing reduced iron according to any one of claims 12 to 18, wherein, Downstream of the reduction section is a first cooling gas outlet that discharges the reaction gas of the metallic iron and the methane gas in the first section to the outside of the system.

20. A system for manufacturing reduced iron, which is the system for manufacturing reduced iron according to any one of claims 12-19, wherein, The reduction section is connected to the first part so that the reaction gas of the metallic iron and the methane gas in the first part is added to the reducing gas.

21. A system for manufacturing reduced iron, which is the system for manufacturing reduced iron according to any one of claims 12 to 20, wherein, Downstream of the first part is a second cooling gas outlet that discharges the reaction gas of the metallic iron and the CO gas in the second part to the outside of the system.

22. A system for manufacturing reduced iron, which is the system for manufacturing reduced iron according to any one of claims 12-21, wherein, Downstream of the second section is a third cooling gas outlet that discharges the methane gas or inactive gas in contact with the metallic iron in the third section to the outside of the system.

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