Blast furnace operation method

Abstract

To improve the reduction efficiency of a reducing material ratio by reduced iron.SOLUTION: In a blast furnace operation method, coke is charged into a blast furnace 10 to form a coke layer 20 in which a central 10A of the blast furnace 10 becomes a hill-shaped portion 22, a first mixture obtained by mixing reduced iron with ores in advance is charged into a first region L1 and a second region L2 on the coke layer 20 so as not to cover a peak 22A of the hill-shaped portion 22 to form a first mixture layer 30P of an ore layer 30, and a second mixture obtained by mixing reduced iron with ores in advance and having a mass ratio of the reduced iron to the ores higher than that of the first mixture is charged into the second region L2 on the first mixture layer 30P to form a second mixture layer 30Q of the ore layer 30.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for operating a blast furnace. [Background technology]

[0002] In a blast furnace operation method in which coke layers and ore layers are alternately deposited in the blast furnace, there is a blast furnace operation method in which reduced iron is charged into the blast furnace from the furnace top in addition to ores in order to reduce the reducing agent ratio (RAR) of the coke, etc. (see, for example, Patent Documents 1 to 7). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-315308 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-271104 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-064705 [Patent Document 4] Japanese Patent Application Laid-Open No. 2002-327205 [Patent Document 5] Japanese Patent Application Laid-Open No. 2017-088950 [Patent Document 6] Japanese Patent Application Publication No. 2019-183270 [Patent Document 7] Japanese Patent Publication No. 2022-042774 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, in the center of a blast furnace, the mass ratio of the ore layer to the coke layer (O / C) is set low in order to ensure good ventilation.

[0005] On the other hand, reduced iron generally has a larger particle size than ores and tends to flow toward the center of the blast furnace when charged into the furnace from the top. Therefore, when ores and reduced iron are charged into the blast furnace from the furnace top, the reduced iron flows toward the center of the blast furnace, and the mass ratio of reduced iron in the ore layer (reduced iron / (reduced iron + ores)) tends to become very high in the center. The area near the center of the blast furnace (center) has a low O / C ratio, meaning that the amount of oxygen that must be removed by reduction is small. Therefore, if a large amount of reduced iron exists near the center of the blast furnace (center), the efficiency of reducing the reducing agent rate by the reduced iron may decrease.

[0006] In consideration of the above, an object of the present invention is to increase the efficiency of reducing the reducing agent rate by reduced iron. [Means for solving the problem]

[0007] A first aspect of the blast furnace operation method is a blast furnace operation method in which coke layers and ore layers are alternately deposited in a blast furnace, wherein the ore layer has, in a longitudinal cross section along the radial direction of the blast furnace, a first region in which the inclination angle of the surface of the ore layer is 20 degrees or more upward from a center side of the blast furnace toward a furnace wall side of the blast furnace, and a second region located closer to the furnace wall than the first region. In the blast furnace operation method, coke is charged onto the ore layer to form a mound-shaped coke layer at the center of the blast furnace, a first mixture in which ore and reduced iron are pre-mixed is charged into the first region and the second region on the coke layer so as not to cover the peak of the mound, forming a first mixture layer of the ore layer, and a second mixture in which reduced iron is pre-mixed with ore and has a higher mass ratio of reduced iron to ore than the first mixture is charged into the second region on the first mixture layer to form a second mixture layer of the ore layer.

[0008] According to the above aspect, coke layers and ore layers are alternately deposited in a blast furnace. The ore layer has a first region and a second region in a longitudinal cross section along the radial direction of the blast furnace. In the first region, the inclination angle of the surface of the ore layer is 20 degrees or more upward from the center side of the blast furnace toward the furnace wall side of the blast furnace. In addition, the second region is located closer to the furnace wall than the first region.

[0009] In such a blast furnace operation method, coke is charged onto the ore layer to form a mountain-shaped coke layer in the center of the blast furnace.

[0010] Next, a first mixture, in which reduced iron is premixed with ore, is charged into the first and second zones above the coke layer so as not to cover the peak of the mound, thereby forming a first mixture layer in the ore layer.

[0011] Here, in the center of the blast furnace, the mass ratio of the ore layer to the coke layer (O / C) is set low to ensure good ventilation, etc. However, the particle size of reduced iron is generally larger than that of the ore.

[0012] Therefore, when the first mixture is charged into the first region where the inclination angle of the ore layer surface is 20 degrees or more, the reduced iron in the first mixture tends to flow toward the center of the blast furnace. As a result, the mass ratio of the ore layer to the coke layer (O / C) increases in the center of the blast furnace, and the reduced iron may be unevenly distributed in the center.

[0013] In contrast, in this embodiment, a heap of coke is formed in the center of the blast furnace. By charging the first mixture into the first and second regions above the coke layer so as not to cover the peak of the heap, the heap prevents the reduced iron in the first mixture from flowing toward the center of the blast furnace. Therefore, the mass ratio of the ore layer to the coke layer (O / C) is prevented from increasing in the center of the blast furnace.

[0014] Next, reduced iron is pre-mixed with the ores, and a second mixture having a higher mass ratio of reduced iron to the ores than the first mixture is charged into a second region above the first mixture layer to form a second mixture layer in the ore layer.

[0015] Here, in order to maximize the efficiency of reducing the reducing agent rate by reduced iron, it is desirable that the mass ratio of reduced iron in the ore layer (reduced iron / (reduced iron + ores)) be uniform on the furnace wall side rather than the center of the blast furnace.

[0016] However, as described above, the reduced iron in the first mixture charged into the first region of the ore layer tends to flow toward the center of the blast furnace.

[0017] In contrast, in the present embodiment, the second mixture is charged into the second region above the first mixture layer, which is located closer to the furnace wall than the second region in a vertical cross section along the radial direction of the blast furnace, thereby preventing the reduced iron in the second mixture from flowing toward the first region.

[0018] The second mixture has a higher mass ratio of reduced iron to ores than the first mixture. By forming a second mixture layer in a second region above the first mixture layer using this second mixture, the mass ratio of reduced iron in the ore layer (reduced iron / (reduced iron + ores)) becomes higher on the furnace wall side of the ore layer.

[0019] As a result, in this embodiment, the difference in the mass ratio of reduced iron (reduced iron / (reduced iron + ores)) in the ore layer is reduced between the center side and the furnace wall side of the ore layer, which further suppresses the decrease in the efficiency of reducing the reducing agent rate by reduced iron.

[0020] A blast furnace operation method according to a second aspect is the blast furnace operation method according to the first aspect, in which coke is charged onto the ore layer to form the coke layer in such a way that the central portion becomes the mountain-shaped portion and the furnace wall side of the mountain-shaped portion becomes a valley-shaped portion.

[0021] According to the above aspect, coke is charged onto the ore layer to form a coke layer having a mountain-shaped portion at the center and a valley-shaped portion on the furnace wall side of the mountain-shaped portion.

[0022] This allows the first mixture to be deposited in the valleys of the coke layer when the first mixture is charged onto the coke layer, further preventing the peaks of the mounds from being covered by the reduced iron in the first mixture.

[0023] Therefore, it is possible to further suppress a decrease in the efficiency of reducing the reducing agent rate by the reduced iron in the center of the blast furnace.

[0024] A blast furnace operation method according to a third aspect is the blast furnace operation method according to the first or second aspect, in which, when the radius of the blast furnace is 1, the first mixture is charged closer to the furnace wall than 0.2 of the radius of the blast furnace, and the first mixture layer is formed on the coke layer.

[0025] According to the above embodiment, when the radius of the blast furnace is 1, the first mixture is charged closer to the furnace wall than 0.2 of the radius of the blast furnace, and a first mixture layer of the ore layer is formed on the coke layer. This prevents the top of the mound from being covered with reduced iron in the first mixture when the first mixture is charged on the coke layer.

[0026] Therefore, the mass ratio of the ore layer to the coke layer (O / C) is prevented from increasing in the center of the blast furnace.

[0027] A blast furnace operation method according to a fourth aspect is the blast furnace operation method according to any one of the first to third aspects, wherein, when the radius of the blast furnace is 1, the second mixture is charged closer to the furnace wall than 0.5 of the radius of the blast furnace, and the second mixture layer is formed on the first mixture layer.

[0028] According to the above embodiment, when the radius of the blast furnace is 1, the second mixture is charged closer to the furnace wall than 0.5 of the radius of the blast furnace, and the second mixture layer is formed on the first mixture layer of the ore layer. This prevents the reduced iron in the second mixture from flowing toward the first region when the second mixture is charged on the first mixture layer.

[0029] Therefore, the difference in the mass ratio of reduced iron (reduced iron / (reduced iron+ores)) in the ore layer is reduced on the central side and the furnace wall side of the ore layer.

[0030] A blast furnace operation method according to a fifth aspect is the blast furnace operation method according to the fourth aspect, wherein the second mixture is charged closer to the furnace wall than 0.6 of the radius of the blast furnace, and the second mixture layer is formed on the first mixture layer.

[0031] According to the above embodiment, when the radius of the blast furnace is 1, the second mixture is charged closer to the furnace wall than 0.6 of the radius of the blast furnace, and the second mixture layer is formed on the first mixture layer of the ore layer. This further suppresses the flow of reduced iron in the second mixture toward the first region when the second mixture is charged on the first mixture layer.

[0032] Therefore, the difference in the mass ratio of reduced iron (reduced iron / (reduced iron+ores)) in the ore layer is further reduced on the central side and furnace wall side of the ore layer.

[0033] A blast furnace operation method according to a sixth aspect is the blast furnace operation method according to any one of the first to fifth aspects, wherein the first mixture is charged onto the coke layer in multiple batches to form the first mixture layer.

[0034] According to the above aspect, the first mixture is charged onto the coke layer in a plurality of batches to form a first mixture layer of the ore layer.

[0035] By charging the first mixture onto the coke layer in multiple batches, for example, different additives can be added to the first mixture in the first batch and the second first mixture in the second batch, thereby improving the flexibility in adjusting the first mixture layer.

[0036] Furthermore, for example, the mass ratio of reduced iron to ores can be changed between the first mixture and the second mixture. [Effects of the Invention]

[0037] As described above, according to the present invention, the efficiency of reducing the reducing agent rate by reduced iron can be increased. [Brief explanation of the drawings]

[0038] [Figure 1] 1 is a vertical cross-sectional view taken along the radial direction of a blast furnace, illustrating a blast furnace according to an embodiment. FIG. [Figure 2] FIG. 2 is an enlarged cross-sectional view showing the coke layer and the ore layer shown in FIG. 1. [Figure 3] FIG. 1 is a hardware configuration diagram of a blast furnace operation control device according to an embodiment. [Figure 4] FIG. 2 is a functional block diagram of a blast furnace operation control device according to one embodiment. [Figure 5] FIG. 3 is an enlarged cross-sectional view corresponding to FIG. 2, showing a coke layer and an ore layer deposited in a blast furnace by a modified example of a blast furnace operating method according to an embodiment. [Figure 6] 3 is an enlarged cross-sectional view corresponding to FIG. 2, showing a coke layer and an ore layer deposited in a blast furnace by a blast furnace operating method according to a comparative example. FIG. [Figure 7] 3 is an enlarged cross-sectional view corresponding to FIG. 2, showing a coke layer and an ore layer deposited in a blast furnace by a blast furnace operating method according to a comparative example. FIG. [Figure 8] 1 is a graph showing the relationship between the dimensionless radius of the blast furnace and the dimensionless mixing ratio of reduced iron in an ore layer deposited in the blast furnace by the blast furnace operating methods according to Comparative Examples 1 and 2. [Figure 9]1 is a graph showing the relationship between the dimensionless radius of the blast furnace and the dimensionless mixing ratio of reduced iron in an ore layer deposited in the blast furnace by the blast furnace operating method according to Example 1. [Figure 10] 1 is a bar graph showing the relationship between Comparative Examples 1 and 2 and Example 1 and RAR. [Figure 11] 10 is a graph showing the relationship between the dimensionless radius of the blast furnace and the dimensionless mixing ratio of reduced iron in an ore layer deposited in the blast furnace by the blast furnace operating method according to Comparative Example 3. [Figure 12] 10 is a graph showing the relationship between the dimensionless radius of the blast furnace and the dimensionless mixing ratio of reduced iron in an ore layer deposited in the blast furnace by the blast furnace operating method according to Comparative Example 4. [Figure 13] 10 is a graph showing the relationship between the dimensionless radius of the blast furnace and the dimensionless mixing ratio of reduced iron in an ore layer deposited in the blast furnace by the blast furnace operating method according to Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0039] An embodiment of the technology disclosed in the present application will be described below.

[0040] (blast furnace) 1 shows a bell-less type blast furnace 10 according to this embodiment. Ores and coke as blast furnace raw materials are charged into the blast furnace 10 from the furnace top 12 by a furnace top charger 40, which will be described later. As a result, coke layers 20 and ore layers 30, which serve as deposits (charge materials), are alternately deposited in the blast furnace 10. Note that reduced iron is mixed with the ores as blast furnace raw materials, as will be described later.

[0041] Hot air, auxiliary fuel, and the like are blown into the blast furnace 10 through tuyere holes (not shown) located at the bottom of the blast furnace 10. This causes the auxiliary fuel and coke to combust, generating rising high-temperature gas (reducing gas). The reducing gas heats and reduces the ores in the ore layer 30 formed in the blast furnace 10 as they descend. The melted ores descending are then discharged as pig iron from a taphole located in the side wall of the furnace bottom.

[0042] The arrow R shown in FIG. 1 indicates the radial direction of the blast furnace 10.

[0043] (Furnace top charging machine) The furnace top charging machine 40 charges ore, coke, and the like as blast furnace raw materials into the blast furnace 10 from the furnace top 12, and deposits coke layers 20 and ore layers 30 alternately in the blast furnace 10. A conveying device 42 is connected to the furnace top charging machine 40. The furnace top charging machine 40 also includes a switching chute 44, a pair of furnace top hoppers 46, a collecting hopper 48, and a rotating chute 50.

[0044] The transport device 42 is, for example, a belt conveyor, and transports ores, coke, and the like as blast furnace raw materials from a raw material tank (not shown) to a switching chute 44. The switching chute 44 can switch the supply destination of the blast furnace raw materials between a pair of furnace top hoppers 46.

[0045] The ores or coke stored in the pair of furnace top hoppers 46 are supplied to a rotating chute 50 via a collecting hopper 48. The rotating chute 50 charges the ores or coke into the blast furnace 10 in layers while rotating around the center (central axis) Z of the blast furnace 10.

[0046] The inclination angle (tilting angle) of the rotating chute 50 with respect to the center (central axis) Z of the blast furnace 10 can be changed. The inclination angle of the rotating chute 50 is managed, for example, by a notch table (not shown).

[0047] Charging a predetermined amount of ore, coke, etc. into the blast furnace 10 from the furnace top 12 using the revolving chute 50 to form a set of coke layer 20 and ore layer 30 (two layers in total) throughout the blast furnace 10 is referred to as one charge. The coke layer 20 and the ore layer 30 can each be charged into the blast furnace 10 in multiple batches, and one charging operation of the coke layer 20 or the ore layer 30 is referred to as one dump. The revolving chute 50 rotates multiple times during one dump.

[0048] (Deposition shape of coke layer and ore layer) Next, the deposition shapes of the coke layer 20 and the ore layer 30 deposited in the blast furnace 10 will be described.

[0049] (Coke layer) 2 shows a coke layer 20 and an ore layer 30 deposited in a blast furnace 10. The coke layer 20 is formed in a layered form over the entire radial length (direction of arrow R) of the blast furnace 10. The coke layer 20 has mountain-shaped portions 22, valley-shaped portions 24, and hill-shaped portions 26.

[0050] The mountain-shaped portion 22 is formed in the center 10A of the blast furnace 10 and around the center 10A. The mountain-shaped portion 22 is formed in a mountain shape (convex shape) that is convex upward. The mountain-shaped portion 22 has a peak 22A and a slope 22B.

[0051] The peak 22A is substantially flat and exposed from the ore layer 30. The peak 22 is formed so that the peak 22A is located at the center 10A of the blast furnace 10. A valley 24 is formed on the furnace wall 14 side of the peak 22.

[0052] In this embodiment, the central portion 10A of the blast furnace 10 means, for example, a region from the center Z of the blast furnace 10 to a radius of 0.2 when the radius of the blast furnace 10 is made dimensionless by setting the radius of the blast furnace 10 to 1. In the following, the radius of the blast furnace 10 made dimensionless as described above will be referred to as the dimensionless radius.

[0053] The valley-shaped portion 24 is formed in a valley shape (concave shape) recessed downward. The valley-shaped portion 24 has a valley bottom 24A and slopes 22B, 24B on both sides of the valley bottom 24A. The valley-shaped portion 24 is adjacent to the mountain-shaped portion 22, and shares the slope 22B on the side of the center 10A of the blast furnace 10 with the mountain-shaped portion 22. The slope 24B of the valley-shaped portion 24 on the side of the furnace wall 14 is gentler than the slope 22B on the side of the center 10A of the blast furnace 10. A hill-shaped portion 26 is formed on the furnace wall 14 side of the valley-shaped portion 24.

[0054] The hill-like portion 26 is formed in a generally flat hill shape overall. This hill-like portion 26 includes at least one of a gentle slope and a generally flat surface, and is formed from the valley-like portion 24 to the furnace wall 14. On the coke layer 20 configured in this manner, an ore layer 30 is deposited in layers.

[0055] In this embodiment, the mountain-shaped portions 22 are formed, for example, in a region from the center Z (dimensionless radius 0.0) of the blast furnace 10 to a dimensionless radius of 0.3. The valley-shaped portions 24 are formed, for example, in a region from 0.3 to 0.7 of the dimensionless radius of the blast furnace 10. Furthermore, the hill-shaped portions 26 are formed, for example, in a region from 0.7 to 1.0 of the dimensionless radius of the blast furnace 10.

[0056] The radial ranges of the peak-shaped portions 22, the valley-shaped portions 24, and the hill-shaped portions 26 of the blast furnace 10 can be changed as appropriate. The coke layer 20 only needs to have at least the peak-shaped portions 22, and the valley-shaped portions 24 and the hill-shaped portions 26 can be omitted as appropriate.

[0057] (Ore layer) The ore layer 30 is formed in a layer shape from the outer end of the center 10A of the blast furnace 10 to the furnace wall 14. In other words, the ore layer 30 is formed in a layer shape in an area other than the center 10A of the blast furnace 10. The ore layer 30 has a valley-shaped portion 32 and a hill-shaped portion 34.

[0058] The valley-shaped portion 32 is formed in a valley shape (concave shape) that is recessed downward. The valley-shaped portion 32 also has a slope 32A. The slope 32A is inclined upward from the center 10A side of the blast furnace 10 toward the furnace wall 14 side. A hill-shaped portion 34 is formed on the furnace wall 14 side of this valley-shaped portion 32.

[0059] The hill-shaped portion 34 is formed in a generally flat hill shape overall. The hill-shaped portion 34 includes at least one of a gentle slope and a generally flat surface, and is formed from the valley-shaped portion 32 to the furnace wall 14.

[0060] In this embodiment, the valley-shaped portions 32 are formed, for example, in a region of 0.2 to 0.6 of the dimensionless radius of the blast furnace 10. The hill-shaped portions 34 are formed, for example, in a region of 0.6 to 1.0 of the dimensionless radius of the blast furnace 10. The radial ranges of the valley-shaped portions 32 and the hill-shaped portions 26 of the blast furnace 10 can be changed as appropriate.

[0061] (first area) The ore layer 30 has a first region L1 and a second region L2. In the first region L1, in a longitudinal cross section along the radial direction of the blast furnace 10, the inclination angle θ of the surface 30S of the ore layer 30 relative to the horizontal plane is 20 degrees (20°) or more upward from the center 10A toward the furnace wall 14.

[0062] The inclination angle θ of the surface 30S of the ore layer 30 in the first region L1 means the inclination angle of the surface 30S of the ore layer 30 in a completed state.

[0063] The first region L1 is formed in a region of 0.2 to 0.6 of the dimensionless radius of the blast furnace 10, and forms a part of the slope 32A of the valley-shaped portion 32. The first region L1 is formed at least in a region of 0.2 to 0.5 of the dimensionless radius of the blast furnace 10.

[0064] (Second area) The second region L2 is located closer to the furnace wall 14 than the first region L1. The second region L2 is formed in a region of 0.6 to 1.0 of the dimensionless radius of the blast furnace 10, and forms a hill-shaped portion 34.

[0065] (Ore layer) Next, the configuration of the ore layer 30 will be described.

[0066] The ore layer 30 has a two-layer structure consisting of a first mixture layer 30P and a second mixture layer 30Q. The first mixture layer 30P is formed from a first mixture in which reduced iron is premixed with ores. The second mixture layer 30Q is formed from a second mixture in which reduced iron is premixed with ores. The second mixture has a higher mixing ratio (mass ratio) of reduced iron to ores (= mass of reduced iron / mass of ores) than the first mixture.

[0067] The phrase "preliminarily mixing reduced iron with ores" means mixing reduced iron with the ores before storing the ores in the top hopper 46, and a first mixture or a second mixture in which reduced iron is mixed with the ores is stored in the top hopper 46. The ores include at least one of sintered ore, lump ore, pellets, and carbon-containing agglomerated ore.

[0068] The reduced iron may be, for example, a pillow-shaped reduced iron. The approximate mass of each piece of reduced iron is, for example, 150 g or more. The approximate mass of each piece of reduced iron of 150 g or more here means that the reduced iron accounts for 70% or more of the total amount of reduced iron mixed with the ores, and each piece of reduced iron has a mass of 150 g or more. The shape of the reduced iron is not limited to a pillow-shaped shape and can be changed as appropriate.

[0069] The first mixture layer 30P is formed by charging the first mixture into the first region L1 and the second region L2 on the coke layer 20. In other words, the first mixture layer 30P is formed by charging the first mixture into regions on the coke layer 20 that will become the first region L1 and the second region L2 of the ore layer 30.

[0070] The first mixture layer 30P is formed in a region including the first region L1 and the second region L2 of the ore layer 30. Specifically, the first mixture layer 30P is formed from the outer end of the center portion 10A of the blast furnace 10 to the furnace wall 14, and constitutes the entire valley portion 32 and the lower layer of the hill portion 34. The first mixture layer 30P is formed in a region from 0.2 to 1.0 of the dimensionless radius of the blast furnace 10, for example.

[0071] Here, in a longitudinal cross section along the radial direction of the blast furnace 10, the inclination angle of the surface 30PS of the first mixture layer 30P in the second region L2 is less than 20 degrees (20°) upward from the center 10A toward the furnace wall 14 side.

[0072] The second region L2 is formed at least in a region of 0.7 to 1.0 of the dimensionless radius of the blast furnace 10. The inclination angle of the surface 30PS of the first mixture layer 30P in the second region L2 is preferably less than 15 degrees (15°), more preferably less than 10 degrees (10°). Here, the inclination angle of the surface 30PS of the first mixture layer 30P is defined as positive when it inclines upward from the center 10A side of the blast furnace 10 toward the furnace wall 14 side, and as negative when it inclines downward from the center 10A side of the blast furnace 10 toward the furnace wall 14 side. In this case, for example, the inclination angle of the surface 30PS of the first mixture layer 30P being less than 15 degrees includes not only positive inclination angles less than 15 degrees but also all of the above-mentioned negative inclination angles.

[0073] The second mixture layer 30Q is formed by charging the second mixture into the second region L2 on the first mixture layer 30P. In other words, the second mixture layer 30Q is formed by charging the second mixture into a region that will become the second region L2 of the ore layer 30 on the first mixture layer 30P.

[0074] The second mixture layer 30Q is formed in a second region L2 on the first mixture layer 30P, and constitutes the upper layer of the hill-shaped portion 34. The second mixture layer 30Q is formed, for example, in a region from 0.6 to 1.0 of the dimensionless radius of the blast furnace 10.

[0075] The first mixture layer 30P is formed in at least the first region L1 and the second region L2, and the second mixture layer 30Q is formed in the second region L2.

[0076] (Outline of blast furnace operation control device) The blast furnace operation control device 60 (see FIG. 4) controls the overall operation of the blast furnace 10. In addition, the blast furnace operation control device 60 controls the furnace top charger 40 so that the pile shapes of the coke layer 20 and the ore layer 30 in each charge become predetermined pile shapes.

[0077] (Hardware configuration of blast furnace operation control device) Next, the hardware configuration of the blast furnace operation control device 60 will be described.

[0078] The blast furnace operation control device 60 is realized, for example, by a computer 70 shown in Fig. 3. The computer 70 includes a CPU (Central Processing Unit) 72, a memory 74 as a temporary storage area, and a non-volatile storage unit 76. The computer 70 also includes an input / output device 78. The CPU 72, the memory 74, the storage unit 76, and the input / output device 78 are connected to one another via a bus 79. The CPU 72 is an example of a control unit.

[0079] The storage unit 76 is realized by, for example, a hard disk drive (HDD), a solid state drive (SSD), a flash memory, etc. A blast furnace operation control program for causing the computer 70 to function as the blast furnace operation control device 60 is stored in advance in the storage unit 76 as a recording medium.

[0080] The CPU 72 reads the blast furnace operation control program from the storage unit 76, expands it in the memory 74, and sequentially executes each step of the blast furnace operation control program. As a result, the computer 70 that executes the blast furnace operation control program functions as the blast furnace operation control device 60.

[0081] (Functions of blast furnace operation control device) Next, the function of the blast furnace operation control device 60 will be described.

[0082] 4, the blast furnace operation control device 60 uses the above hardware resources to realize various functions when executing the above-mentioned blast furnace operation control program. Specifically, the blast furnace operation control device 60 functionally includes a surface shape measurement unit 52 and a tilt angle calculation unit 54.

[0083] (Surface shape measurement section) The surface shape measuring unit 52 operates, for example, a profilometer (not shown) installed in the blast furnace 10 to measure the surface shape of the surface 30PS of the first mixture layer 30P and the surface shape of the surface 30S of the ore layer 30. The profilometer may be, for example, a microwave type, a millimeter wave type, or an optical type.

[0084] The shape of the surface 30PS of the first mixture layer 30P and the shape of the surface 30S of the ore layer 30 refer to the shape of the surface 30PS of the first mixture layer 30P and the shape of the surface 30S of the ore layer 30 in a vertical cross section along the radial direction of the blast furnace 10. The shape of the surface 30PS of the first mixture layer 30P and the shape of the surface 30S of the ore layer 30 may be measured at a specific vertical cross section in the circumferential direction of the blast furnace 10, or may be measured at different vertical cross sections in the circumferential direction of the blast furnace 10.

[0085] (Tilt angle calculation section) The inclination angle calculation unit 54 calculates the inclination angle θ of the surface 30S of the ore layer 30 based on the shape of the surface 30S measured by the surface shape measurement unit 52.

[0086] Specifically, the inclination angle calculation unit 54 approximates the surface 30S of the ore layer 30 measured by the surface shape measurement unit 52 in a vertical cross section along the radial direction of the blast furnace 10 to a straight line (hereinafter referred to as the "approximate straight line") V using the least squares method or the like, and calculates the inclination angle θ of the approximate straight line V with respect to the horizontal plane.

[0087] In this embodiment, the surface 30S of the ore layer 30 from 0.2 to 0.6 of the dimensionless radius of the blast furnace 10 is approximated to an approximation line V by the least squares method or the like, and the inclination angle θ of the approximation line V with respect to the horizontal plane is calculated. Since this inclination angle θ is 20 degrees or more, at least the region from 0.2 to 0.6 of the dimensionless radius of the blast furnace 10 is set as the first region L1.

[0088] In addition, in a longitudinal cross section along the radial direction of the blast furnace 10, for example, the surface 30S of the ore layer 30 from 0.2 to 0.5 of the dimensionless radius of the blast furnace 10 is approximated to an approximate straight line by the least squares method or the like, and the inclination angle θ of the approximate straight line with respect to the horizontal plane is calculated. When this inclination angle θ is 20 degrees or more, at least the region from 0.2 to 0.5 of the dimensionless radius of the blast furnace 10 becomes the first region L1. In this way, the calculation method of the inclination angle θ can be changed as appropriate.

[0089] The inclination angle θ of the surface 30S of the ore layer 30 may be, for example, an average value of the inclination angles of the surface 30S of the ore layer 30 calculated from a plurality of vertical cross sections different in the circumferential direction of the blast furnace 10. The inclination angle θ of the surface 30S of the ore layer 30 may be, for example, an average value of a plurality of inclination angles calculated from the surface shapes of the ore layer 30 formed in different charges.

[0090] Furthermore, the inclination angle calculation unit 54 calculates the inclination angle of the surface 30PS based on the shape of the surface 30PS of the first mixture layer 30P measured by the surface shape measurement unit 52.

[0091] Specifically, in a vertical cross section along the radial direction of the blast furnace 10, for example, the surface 30PS of the first mixture layer 30P from 0.6 to 1.0 of the dimensionless radius of the blast furnace 10 is approximated to an approximate straight line by the least squares method or the like, and the inclination angle of the approximate straight line with respect to the horizontal plane is calculated. When this inclination angle is less than 20 degrees, at least the region from 0.6 to 1.0 of the dimensionless radius of the blast furnace 10 becomes the second region L2.

[0092] Furthermore, the inclination angle of the surface 30PS of the first mixture layer 30P may be, for example, an average value of the inclination angles of the surface 30PS of the first mixture layer 30P calculated from a plurality of vertical cross sections different in the circumferential direction of the blast furnace 10. Furthermore, the inclination angle θ of the surface 30PS of the first mixture layer 30P may be, for example, an average value of a plurality of inclination angles calculated from the surface shapes of the first mixture layer 30P formed in different charges.

[0093] (effect) Next, the effects of this embodiment will be described.

[0094] In the center 10A of the blast furnace 10, the mass ratio (O / C) of the ore layer 30 to the coke layer 20 is set low in order to ensure good ventilation, etc. However, the particle size of reduced iron is generally larger than the particle size of the ore.

[0095] Therefore, when the first mixture is charged into the first region L1 where the inclination angle of the surface of the ore layer 30 is 20 degrees or more, the reduced iron in the first mixture tends to flow toward the center 10A of the blast furnace 10. As a result, as shown in Fig. 6, the mass ratio of reduced iron in the ore layer 30 (reduced iron / (reduced iron + ores)) may become high at the center 10A of the blast furnace 10.

[0096] 2 , a convex portion 22 of the coke layer 20 is formed in the center 10A of the blast furnace 10. The first mixture is charged into the first region L1 and the second region L2 on the coke layer 20 so as not to cover the peaks 22A of the convex portions 22. This prevents the reduced iron in the first mixture from flowing toward the center 10A of the blast furnace 10 by the convex portions 22.

[0097] Next, reduced iron is pre-mixed with the ores, and a second mixture having a higher mass ratio of reduced iron to the ores than the first mixture is charged into a second region L2 above the first mixture layer 30P to form a second mixture layer 30Q of the ore layer 30.

[0098] Here, in order to maximize the efficiency of reducing the reducing agent ratio by the reduced iron, it is desirable that the mass ratio of reduced iron in the ore layer 30 (reduced iron / (reduced iron + ores)) be uniform on the furnace wall 14 side of the center 10A of the blast furnace 10.

[0099] However, as described above, the reduced iron in the first mixture charged into the first region L1 of the ore layer 30 tends to flow toward the center portion 10A of the blast furnace 10.

[0100] In contrast to this, in the present embodiment, the second mixture is charged into the second region L2 on the first mixture layer 30P where the inclination angle θ of the surface 30PS is less than 20 degrees in a vertical cross section along the radial direction of the blast furnace 10, thereby preventing the reduced iron in the second mixture from flowing toward the first region L1.

[0101] The second mixture has a higher mass ratio of reduced iron to ores than the first mixture. By forming the second mixture layer 30Q in the second region L2 on the first mixture layer 30P using this second mixture, the mass ratio of reduced iron in the ore layer 30 (reduced iron / (reduced iron + ores)) becomes higher on the furnace wall 14 side of the ore layer 30.

[0102] As a result, in this embodiment, the difference in the mass ratio of reduced iron (reduced iron / (reduced iron+ores)) in the ore layer 30 is reduced between the center 10A side and the furnace wall 14 side of the ore layer 30. Therefore, it is possible to further suppress a decrease in the efficiency of reducing the reducing agent rate by reduced iron.

[0103] In this embodiment, coke is charged onto the ore layer 30 to form a coke layer 20 in which the central portion 10A becomes a mountain-shaped portion 22 and the mountain-shaped portion 22 on the furnace wall 14 side becomes a valley-shaped portion 24. As a result, when the first mixture is charged onto the coke layer 20, the first mixture is deposited in the valley-shaped portion 24 of the coke layer 20. This further prevents the peaks 22A of the mountain-shaped portions 22 from being covered with reduced iron in the first mixture.

[0104] Therefore, in the center portion 10A of the blast furnace 10, the decrease in the efficiency of reducing the reducing agent rate by the reduced iron can be further suppressed.

[0105] In this embodiment, the first mixture is charged closer to the furnace wall 14 than the center 10A of the blast furnace 10, and a first mixture layer 30P of the ore layer 30 is formed on the coke layer 20. In other words, in this embodiment, the first mixture is charged closer to the furnace wall 14 than 0.2 of the dimensionless radius of the blast furnace 10, and a first mixture layer 30P of the ore layer 30 is formed on the coke layer 20. This prevents the peaks 22A of the mounds 22 from being covered with reduced iron in the first mixture when the first mixture is charged on the coke layer 20.

[0106] Furthermore, in this embodiment, the second mixture is charged closer to the furnace wall 14 than 0.6 of the dimensionless radius of the blast furnace 10, and a second mixture layer 30Q is formed on the first mixture layer 30P of the ore layer 30. This further suppresses the flow of reduced iron in the second mixture toward the first region L1 when the second mixture is charged in the second region L2 above the first mixture layer 30P.

[0107] Therefore, the difference in the mass ratio of reduced iron (reduced iron / (reduced iron+ores)) in the ore layer 30 between the center 10A side and the furnace wall 14 side of the ore layer 30 is further reduced.

[0108] (Variation) Next, a modification of the above embodiment will be described.

[0109] In the above embodiment, the second mixture is charged closer to the furnace wall 14 than 0.6 of the dimensionless radius of the blast furnace 10, and the second mixture layer 30Q is formed on the first mixture layer 30P of the ore layer 30. However, the charging position of the second mixture can be changed as appropriate depending on the deposition shape of the first mixture layer 30P. For example, it is also possible to charge the second mixture closer to the furnace wall 14 than 0.5 of the dimensionless radius of the blast furnace 10, and form the second mixture layer 30Q on the first mixture layer 30P of the ore layer 30.

[0110] In the above embodiment, the first mixture is charged into the blast furnace 10 in a single dump (charging operation), thereby forming the first mixture layer 30P of the ore layer 30 on the coke layer 20. However, the first mixture may be charged into the blast furnace 10 in multiple steps (multiple dumps) rather than in a single operation, thereby forming the first mixture layer 30P of the ore layer 30 on the coke layer 20.

[0111] 5, for example, the first mixture is charged into the blast furnace 10 in two separate steps (two dumps), thereby forming a first mixture layer 30P of the ore layer 30 on the coke layer 20. More specifically, a first layer 30P1 of the first mixture layer 30P is formed on the coke layer 20 by the first dumping of the first mixture, and a second layer 30P2 is formed on the first layer 30P1 of the first mixture layer 30P by the second dumping of the first mixture.

[0112] By charging the first mixture onto the coke layer 20 in multiple batches in this manner, different additives can be added to the first mixture in the first batch and the second first mixture in the second batch, respectively, thereby improving the degree of freedom in adjusting the first mixture layer 30P.

[0113] Furthermore, for example, the mass ratio of reduced iron to ores can be different between the first mixture and the second mixture. In this case, the mixing ratio (mass ratio) of reduced iron to ores is set to be higher in the second mixture than in the first mixture. Note that the first mixture can also be charged onto the coke layer 20 in three or more separate batches.

[0114] In the above embodiment, the blast furnace 10 is of a bell-less type. However, the blast furnace 10 may be of a bell type.

[0115] (comparative analysis) Next, the comparative analysis will be described.

[0116] In this comparative analysis, the blast furnace operation methods according to the comparative example and the example were used to calculate the furnace volume of 5,000 m 3The behavior of reduced iron when an ore layer is piled up in a bell-less blast furnace of the 1980s class was analyzed (simulated) using DEM (Discrete Element Method).

[0117] (Analysis conditions) The analysis conditions are as follows: The inclination angle of the surface of the first area of the ore layer θ: 30 degrees The inclination angle of the surface of the second area of the ore layer θ: 5 degrees Average particle size of ore: 23 mm Shape of reduced iron: Pillow type Approximate mass of each reduced iron: 600g Mass ratio of reduced iron in the ore layer (reduced iron / (reduced iron + ores)): 0.1 (10%)

[0118] (Comparative Example 1) FIG. 6 shows a coke layer 100 and an ore layer 110 deposited in a blast furnace 10 by a blast furnace operating method according to a first comparative example.

[0119] In the coke layer 100 of Comparative Example 1, no mounds 22 (see FIG. 2) are present in the center 10A of the blast furnace 10, and the center 10A is a flat surface. The ore layer 110 of Comparative Example 1 has a single-layer structure and is formed from a mixture of ores and reduced iron.

[0120] The mixture of Comparative Example 1 was a mixture of 112.5 t of ore and 12.5 t of reduced iron, and this mixture was charged into the blast furnace 10 in a region of 0.0 to 1.0 of the dimensionless radius.

[0121] (Comparative Example 2) FIG. 7 shows a coke layer 20 and an ore layer 110 deposited in a blast furnace 10 by a blast furnace operating method according to Comparative Example 2.

[0122] The coke layer 20 of Comparative Example 2 has the same configuration as the coke layer 20 of the above embodiment. On the other hand, the ore layer 110 of Comparative Example 2 has a single-layer structure and is formed from a mixture of ores and reduced iron.

[0123] The mixture of Comparative Example 2 was the same as that of Comparative Example 1, and was charged into the blast furnace 10 in a region of 0.2 to 1.0 of the dimensionless radius.

[0124] (Analysis results for Comparative Examples 1 and 2) 8 shows graphs Y1 and Y2 illustrating the relationship between the dimensionless radius of the blast furnace 10 and the dimensionless mixing ratio of reduced iron for Comparative Examples 1 and 2. Note that the dimensionless mixing ratio of reduced iron is, for example, the dimensionless mixing ratio of reduced iron in the ore layer 110 after being charged into the blast furnace 10, where the mixing ratio of reduced iron in the mixture before being charged into the blast furnace 10 (0.1) is set to 1.

[0125] In Comparative Example 1, as shown in Fig. 6, when the mixture was charged onto the coke layer 100, the reduced iron in the mixture flowed together with the coke to the center 10A of the blast furnace 10, and a mound 110A containing a mixture of reduced iron and coke was formed in the center 10A. Furthermore, as the reduced iron flowed in, the peak of the mound 110A was also covered with reduced iron. Therefore, in Comparative Example 1, as shown in graph Y1 in Fig. 8, the dimensionless mixing ratio of reduced iron increased from 0.4 of the dimensionless radius of the blast furnace 10 toward the center 10A.

[0126] In contrast, in Comparative Example 2, as shown in Fig. 7, a mountain-shaped portion 22 of the coke layer 20 is formed in the center 10A of the blast furnace 10. As a result, in Comparative Example 2, when a mixture is charged onto the coke layer 20, the mountain-shaped portion 22 of the coke layer 20 prevents the mixture from flowing into the center 10A of the blast furnace 10. Therefore, in Comparative Example 2, as shown in graph Y2 in Fig. 8, the dimensionless mixing ratio of reduced iron is low on the center 10A side of the blast furnace 10.

[0127] On the other hand, in Comparative Example 2, the ore layer 110 has a single-layer structure. As a result, when a mixture is charged onto the coke layer 20, the mixture on the furnace wall 14 side of the blast furnace 10 flows toward the mound 22 side of the coke layer 20. Therefore, as shown in graph Y2, the dimensionless mixing ratio of reduced iron increases as the dimensionless radius of the blast furnace 10 changes from 0.8 to 0.4.

[0128] Example 1 Example 1 corresponds to the embodiment shown in Fig. 2. The coke layer 20 and the ore layer 30 of Example 1 have the same configuration as those of the above embodiment.

[0129] The first mixture is a mixture of 80.0 t of ore and 7.5 t of reduced iron, with a mixing ratio of 0.094 (=7.5 t / 80.0 t). This first mixture is charged into the blast furnace 10 in a region of 0.2 to 1.0 of the dimensionless radius. The second mixture is a mixture of 32.5 t of ore and 5.0 t of reduced iron, with a mixing ratio of 0.154 (=5.0 t / 32.5 t). This second mixture is charged into the blast furnace 10 in a region of 0.6 to 1.0 of the dimensionless radius.

[0130] (Analysis results of Example 1) 9 shows a graph X1 illustrating the relationship between the dimensionless radius of the blast furnace 10 and the dimensionless mixing ratio of reduced iron for Example 1. Note that the graph XP shown in Fig. 9 corresponds to the first mixture layer 30P, and the graph XQ corresponds to the second mixture layer 30Q. In addition, the graph X1 shows the sum of the graphs XP and XQ.

[0131] In Example 1, as shown in Fig. 2, a heap 22 of the coke layer 20 is formed in the center 10A of the blast furnace 10. As a result, in Example 1, when the first mixture is charged onto the coke layer 20, the heap 22 of the coke layer 20 prevents the reduced iron in the first mixture from flowing to the center 10A of the blast furnace 10. Therefore, in Example 1, as shown in graph X1 in Fig. 9, the dimensionless mixing ratio of the reduced iron is low on the center 10A side of the blast furnace 10.

[0132] In Example 1, the ore layer 30 has a two-layer structure of a first mixture layer 30P and a second mixture layer 30Q, and the mixing ratio of the second mixture is higher than that of the first mixture. Therefore, as shown in graph X1 in Fig. 9, the dimensionless mixing ratio of reduced iron increases as the dimensionless radius of the blast furnace 10 approaches from 0.6 to 1.0. This reduces the difference in the mass ratio of reduced iron (reduced iron / (reduced iron + ores)) within the ore layer 30 between the center 10A side and the furnace wall 14 side of the ore layer 30.

[0133] In addition, graph X1 shows two peaks for the dimensionless mixing ratio of reduced iron, but these peak values are similar. This further reduces the difference in the mass ratio of reduced iron (reduced iron / (reduced iron + ores)) in the ore layer 30 between the center 10A side of the ore layer 30 and the furnace wall 14 side.

[0134] Moreover, Fig. 10 shows the relationship between the RAR (reducing agent ratio) and Comparative Examples 1 and 2 and Example 1. As shown in Fig. 10, Example 1 has a lower RAR than Comparative Examples 1 and 2. This shows that Example 1 can increase the efficiency of reducing the RAR.

[0135] (Comparative Example 3) Next, Comparative Example 3 is similar to Example 1, but differs from Example 1 in that the mixing ratio of the second mixture forming the second mixture layer 30Q is lower than the mixing ratio of the first mixture forming the first mixture layer 30P of the ore layer 30.

[0136] Specifically, the first mixture is a mixture of 77.5 t of ore and 10.0 t of reduced iron, with a mixing ratio of 0.129 (=10.0 t / 77.5 t). The second mixture is a mixture of 35.0 t of ore and 2.5 t of reduced iron, with a mixing ratio of 0.071 (=2.5 t / 35.0 t). The mixing ratio of the second mixture, 0.071, is lower than the mixing ratio of the first mixture, 0.129.

[0137] (Analysis results of Comparative Example 3) 11 shows a graph Y3 illustrating the relationship between the dimensionless radius of the blast furnace 10 and the dimensionless mixing ratio of reduced iron for Comparative Example 3. Note that the graph YP shown in Fig. 11 corresponds to the first mixture layer 30P, and the graph YQ corresponds to the second mixture layer 30Q. Furthermore, the graph Y3 shows the sum of the graphs YP and YQ.

[0138] In Comparative Example 3, as shown in graph Y3, the dimensionless mixing ratio of reduced iron is low on the furnace wall 14 side of the blast furnace 10. This shows that the RAR reduction rate is lower in Comparative Example 3 than in Example 1.

[0139] Comparative Example 4 5, the first mixture layer 30P of the ore layer 30 is composed of a first layer 30P1 and a second layer 30P2. This comparative example 4 differs from the example 2 described later in that the mixing ratio of the second mixture forming the second mixture layer 30Q is lower than the mixing ratio of the first mixture forming the first mixture layer 30P of the ore layer 30.

[0140] The first mixture in the first layer 30P1 is a mixture of 39.0 t of ore and 3.3 t of reduced iron. The first mixture in the second layer 30P2 is a mixture of 54.5 t of ore and 9.0 t of reduced iron. The mixing ratio of this first mixture is 0.132 (= (3.3 t + 9.0 t) / (39.0 t + 54.5 t)). The first mixture is charged into a region of the dimensionless radius of the blast furnace 10 that is 0.2 to 1.0.

[0141] The second mixture in the second mixture layer 30Q is a mixture of 37.0 t of ore and 2.2 t of reduced iron. The mixing ratio of this second mixture is 0.059 (= 2.2 t / 37.0 t), which is lower than the mixing ratio of the first mixture (0.132). The second mixture is charged into the blast furnace 10 in a region of 0.6 to 1.0 of the dimensionless radius.

[0142] (Analysis results of Comparative Example 4) 12 shows a graph Y4 illustrating the relationship between the dimensionless radius of the blast furnace 10 and the dimensionless mixing ratio of reduced iron for Comparative Example 4. Note that the graph YP1 shown in FIG. 12 corresponds to the first layer 30P1 of the first mixture layer 30P, and the graph YP2 corresponds to the second layer 30P2 of the first mixture layer 30P. Furthermore, the graph YQ corresponds to the second mixture layer 30Q. Furthermore, the graph Y4 shows the sum of the graphs YP1, YP2, and YQ.

[0143] In Comparative Example 4, as shown in graph Y4, the dimensionless mixing ratio of reduced iron is low on the furnace wall 14 side of the blast furnace 10. This shows that the RAR reduction rate is lower in Comparative Example 4 than in Example 2, which will be described later.

[0144] Example 2 Example 2 corresponds to the modified example shown in FIG. 5, and the first mixture layer 30P of the ore layer 30 is composed of a first layer 30P1 and a second layer 30P2.

[0145] The first mixture in the first layer 30P1 is a mixture of 44.7 t of ore and 2.9 t of reduced iron. The first mixture in the second layer 30P2 is a mixture of 63.5 t of ore and 7.8 t of reduced iron. The mixing ratio of this first mixture is 0.099 (= (2.9 t + 7.8 t) / (44.7 t + 63.5 t)). The first mixture is charged into a region of the dimensionless radius of the blast furnace 10 that is 0.2 to 1.0.

[0146] The second mixture in the second mixture layer 30Q is a mixture of 22.3 t of ore and 3.8 t of reduced iron. The mixing ratio of this second mixture is 0.170 (= 3.8 t / 22.3 t), which is higher than the mixing ratio of the first mixture (0.099). The second mixture is charged into a region of the dimensionless radius of the blast furnace 10 between 0.6 and 1.0.

[0147] (Analysis results of Example 2) 13 shows a graph X2 illustrating the relationship between the dimensionless radius of the blast furnace 10 and the dimensionless mixing ratio of reduced iron for Example 2. Note that the graph XP1 shown in FIG. 13 corresponds to the first layer 30P1 of the first mixture layer 30P, and the graph XP2 corresponds to the second layer 30P2 of the first mixture layer 30P. Furthermore, the graph XQ corresponds to the second mixture layer 30Q. Furthermore, the graph X2 represents the sum of the graphs XP1, XP2, and XQ.

[0148] In Example 2, as shown in graph X2, the dimensionless mixing ratio of reduced iron is lower on the side of the center 10A of the blast furnace 10. Also, in Example 2, as shown in graph X2, the dimensionless mixing ratio of reduced iron increases as the dimensionless radius of the blast furnace 10 approaches from 0.8 to 1.0. This reduces the difference in the mass ratio of reduced iron (reduced iron / (reduced iron + ores)) in the ore layer 30 between the side of the center 10A of the ore layer 30 and the side of the furnace wall 14.

[0149] Furthermore, in the graph X2, two peaks appear for the dimensionless mixing ratio of reduced iron, but these peak values are similar. As a result, the difference in the mass ratio of reduced iron (reduced iron / (reduced iron + ores)) in the ore layer 30 is further reduced between the center 10A side of the ore layer 30 and the furnace wall 14 side. This shows that the RAR reduction efficiency can be improved in Example 2.

[0150] (Other variations) In the above embodiment, the control unit (processor) includes a general-purpose processor (e.g., CPU: Central Processing Unit, etc.) or a dedicated processor (e.g., GPU: Graphics Processing Unit, ASIC: Application Specific Integrated Circuit, FPGA: Field Programmable Gate Array, programmable logic device, etc.).

[0151] Although one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment, and one embodiment and various modified examples may be used in appropriate combination, and it goes without saying that the present invention can be implemented in various forms as long as it does not deviate from the gist of the present invention. [Explanation of symbols]

[0152] 10 blast furnace 10A center 14 Furnace wall 20 Coke layer 22 Mountain part 22A Summit 30 Ore Layer 30S surface 30P first mixture layer 30Q second mixture layer 32 Valley 60 Blast furnace operation control device 72 CPU (control unit) L1 First area L2 second area Arrow R: Radial direction of the blast furnace Z center θ The inclination angle of the ore layer surface

Claims

1. A blast furnace operation method for alternately depositing coke layers and ore layers in a blast furnace, wherein the ore layer has, in a longitudinal cross section along the radial direction of the blast furnace, a first region in which the inclination angle of the surface of the ore layer is 20 degrees or more upward from the center side of the blast furnace toward the furnace wall side of the blast furnace, and a second region located closer to the furnace wall than the first region, Coke is charged onto the ore layer to form the coke layer in a mountain-shaped portion at the center of the blast furnace; a first mixture obtained by preliminarily mixing ore with reduced iron is charged into the first region and the second region on the coke layer so as not to cover the peak of the mound-shaped portion, thereby forming a first mixture layer in the ore layer; ore is mixed with reduced iron in advance, and a second mixture having a mass ratio of reduced iron to ore higher than that of the first mixture is charged into the second region on the first mixture layer to form a second mixture layer on the ore layer. Blast furnace operation methods.

2. charging coke onto the ore layer to form the coke layer, with the central portion forming the mountain-shaped portion and the furnace wall side of the mountain-shaped portion forming a valley-shaped portion; The method for operating a blast furnace according to claim 1.

3. When the radius of the blast furnace is 1, The first mixture is charged closer to the furnace wall than 0.2 of the radius of the blast furnace, and the first mixture layer is formed on the coke layer. The method for operating a blast furnace according to claim 1.

4. When the radius of the blast furnace is 1, The second mixture is charged closer to the furnace wall than 0.5 of the radius of the blast furnace, and the second mixture layer is formed on the first mixture layer. The method for operating a blast furnace according to claim 1.

5. The second mixture is charged closer to the furnace wall than 0.6 of the radius of the blast furnace, and the second mixture layer is formed on the first mixture layer. The method for operating a blast furnace according to claim 4.

6. The first mixture is charged onto the coke layer in multiple batches to form the first mixture layer. The blast furnace operation method according to any one of claims 1 to 5.

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