Method for charging raw material into blast furnace

Abstract

To provide a method for charging a raw material into a blast furnace, by which reduced iron can be charged into a portion having a large reduction load in a radial direction of the furnace without providing a dedicated hopper at the top of the furnace.SOLUTION: In a method of mixing ore raw material and reduced iron and charging the mixture into a bell-less type blast furnace, when the ore raw material is charged into one of the furnace top bunkers by a charging conveyor, reduced iron is cut out onto the ore raw material conveyed by the charging conveyor, whereby the reduced iron is stacked on the ore raw material in a length range within 50% of the loading length of the ore raw material on a head side in the conveying direction, and the ore raw material and the reduced iron are charged into the furnace top bunker in this state. When the raw material in the furnace top bunker is charged into the furnace by a revolving chute, the raw material is charged while revolving and tilting the chute to move the raw material charging position from a furnace intermediate part to a furnace wall part side.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a raw material charging method for obtaining a desired charging distribution in a bell-less blast furnace.

Background Art

[0002] In recent years, global warming due to the increase in CO2 emissions has become a problem, and suppression of CO2 emissions is also an important issue in the iron and steel industry. Most of the CO2 emitted from steelworks is emitted from blast furnaces. Reduction of CO2 emissions in blast furnaces is possible by reducing the reducing agents (coke, pulverized coal, natural gas, etc.) used in blast furnaces. Coke serves as a heat source for melting ore raw materials, a reducing agent for ore raw materials, a carburizing agent for lowering the melting point by carburizing molten iron, and a spacer for ensuring air permeability in the blast furnace. By maintaining air permeability with this coke, the settlement of the charged material is stabilized, and stable operation of the blast furnace is achieved. Here, from the viewpoint of reducing CO2 emissions, it is desirable that the ratio of coke charged into the blast furnace is low. However, if the ratio of coke is lowered, the roles played by the above-mentioned coke also decrease, so it is necessary to improve the reduction efficiency of the ore layer and improve air permeability at the same time.

[0003] The use of reduced iron has been studied as a countermeasure to this problem, and various proposals have been made regarding its charging form and the like. Among them, Patent Document 1 shows a method of charging reduced iron or iron scrap held in a sub-hopper at the top of the furnace and ore held in the main hopper together with a swivel chute to a part where the gas utilization rate of the exhaust gas is high, indicating that the reduction load of the ore is high. According to the method of Patent Document 1, since reduced iron or iron scrap can be charged limited to a part where the reduction load is large in the blast furnace radius direction, the reduction state of the ore in the furnace can be effectively stabilized, and the gas flow can also be stabilized.

Prior Art Documents

Patent Documents

[0004] Patent Document 1 Japanese Patent Application Laid-Open No. 2019-183270 Summary of the Invention Problems to be Solved by the Invention

[0005] However, in the method of Patent Document 1, since it is necessary to provide a dedicated sub-hopper for holding reduced iron or iron scrap at the furnace top, there is a problem that the equipment cost increases. Also, there is a problem that the charging time becomes long by charging reduced iron or iron scrap from the dedicated hopper. On the other hand, in response to such problems, a charging method of separately setting batches for charging reduced iron or iron scrap can be considered, but in this method, the charging time becomes long due to an increase in the number of charging batches, and the productivity decreases. Therefore, an object of the present invention is to solve the problems of the prior art as described above, and without providing a dedicated hopper such as reduced iron at the furnace top, and without increasing the number of charging batches, to charge metal iron raw materials such as reduced iron to a part where the reduction load is large in the radial direction of the blast furnace. It is to provide a raw material charging method that can be performed. Means for Solving the Problems

[0006] Hereinafter, the case of using reduced iron as the metal iron raw material will be described as an example. In order to solve the above problems, it is necessary to charge reduced iron cut out onto the charging conveyor from the raw material hopper and ore raw materials cut out separately onto the charging conveyor into one furnace top bunker, and then charge them into the furnace through a swivel chute. However, even if reduced iron is charged into one top bunker first and then the ore raw materials are charged and held in the bunker, and only the reduced iron is preferentially discharged from this top bunker and attempted to be charged to a predetermined position in the furnace, it has been found that there is a problem that the reduced iron cannot be charged to the predetermined position due to the funnel flow in the top bunker. Also, if only the reduced iron is diverted to the charging conveyor, there is also a problem that the wear of the charging conveyor becomes severe due to the direct contact between the burrs of the reduced iron compact and the belt conveyor.

[0007] Therefore, in order to solve the above problems, the present inventors have intensively studied the relationship between elements such as (i) the method of cutting out reduced iron on the charging conveyor, (ii) the tilting method of the swivel chute, (iii) the use of the segregation control plate in the top bunker, (iv) the method of mixing reduced iron in the two-batch charging of ore raw materials, etc. (and their combinations) and the charge distribution (distribution of reduced iron). As a result, by optimizing and combining the above (i) and (ii), and preferably further optimizing and combining the above (iii) and / or (iv), when charging the ore raw materials and reduced iron held in one top bunker into the furnace, it has been found that the reduced iron can be accurately charged to the desired position (the part with a large reduction load).

[0008] The present invention has been made based on such findings, and the gist thereof is as follows. [1] In a bell-less blast furnace having a raw material charging device in which a plurality of top bunkers are arranged in parallel and raw materials are charged into the furnace by a swivel chute, a method of mixing an ore raw material (a) containing at least one of sintered ore, pellets, and lump ore and a metallic iron raw material (b) containing reduced iron and / or granular iron and charging them into the blast furnace, When the ore raw material (a) is conveyed to the furnace top by the charging conveyor and charged into one of the top bunkers, the metallic iron raw material (b) is cut out onto the ore raw material (a) conveyed by the charging conveyor, so that the metallic iron raw material (b) is laminated onto the ore raw material (a) within the length range of 50% or less on the leading side in the conveying direction among the loaded lengths of the ore raw material (a) loaded on the charging conveyor. Then, the ore raw material (a) and the metallic iron raw material (b) are charged into the top bunker in this state. When charging the raw materials in the top bunker into the furnace by the swivel chute, while rotating the swivel chute and tilting it to move the raw material charging position from the middle part of the furnace to the furnace wall side, the raw materials are charged. This is a method for charging raw materials into a blast furnace.

[0009] [2] In the raw material charging method of [1] above, when the ore raw material (a) is conveyed to the furnace top by the charging conveyor and charged into one of the top bunkers, the metallic iron raw material (b) is laminated onto the ore raw material (a) within the length range of 25% or less on the leading side in the conveying direction among the loaded lengths of the ore raw material (a) loaded on the charging conveyor. This is a method for charging raw materials into a blast furnace. [3] In the raw material charging method of [1] or [2] above, When charging the ore raw material (a) for one charge into the furnace in two batches, The metallic iron raw material (b) is mixed with the ore raw material (a) for the second batch and charged into the furnace. This is a method for charging raw materials into a blast furnace. [4] In the raw material charging method of [3] above, the ore raw material (a) for the first batch is charged into the furnace without mixing the metallic iron raw material (b). This is a method for charging raw materials into a blast furnace.

[0010] [5] In any of the raw material charging methods of [1] to [4] above, A segregation control plate is installed in the top bunker. When charging the ore raw material (a) and the metallic iron raw material (b) conveyed by the charging conveyor into the top bunker, the raw material receiving surface of the segregation control plate faces outward in the furnace radius direction and is inclined downward with respect to the outside direction of the furnace. The raw materials falling from above are made to fall downward via the raw material receiving surface of the segregation control plate and are deposited in the bunker. A method for charging raw materials into a blast furnace, characterized in that. [6] In the raw material charging method of [5] above, the average particle size [d M of the metallic iron raw material (b) and the average particle size [d O of the ore raw material (a) are such that [d M > [d O . A method for charging raw materials into a blast furnace, characterized in that. [7] In the raw material charging method according to any one of [1] to [6] above, when the ore raw material (a) is conveyed to the top of the furnace by the charging conveyor and charged into one of the top bunkers, among the loaded lengths of the ore raw material (a) loaded on the charging conveyor, the metallic iron raw material (b) is not laminated on the ore raw material (a) in a length range within at least the leading side 1% in the conveying direction. A method for charging raw materials into a blast furnace, characterized in that. [8] A method for producing hot metal, characterized by having a step of mixing an ore raw material (a) containing at least one of sintered ore, pellets and lump ore and a metallic iron raw material (b) containing reduced iron or / and granular iron and charging them into a blast furnace by the raw material charging method according to any one of [1] to [7] above.

Effect of the Invention

[0011] According to the raw material charging method of the present invention, without providing a dedicated hopper for reduced iron or the like at the top of the furnace and without increasing the number of charging batches, the metallic iron raw material such as reduced iron can be accurately charged to a site (position) with a large reduction load in the blast furnace radius direction. Therefore, in blast furnace operation, productivity can be improved and equipment costs can be reduced. Further, in the method of the present invention, by using the segregation control plate in the top bunker under predetermined conditions, the metallic iron raw material can be charged particularly accurately to a desired site (position). In the method of the present invention, the ore raw materials for one charge are charged into the furnace in two batches, and by mixing the metallic iron raw material with the ore raw materials of the second batch, the metallic iron raw material can be charged into a particularly suitable part (position). Moreover, according to the method for producing hot metal of the present invention, by charging the raw materials by the above raw material charging method, hot metal can be produced with high productivity while keeping the equipment cost low.

Brief Description of the Drawings

[0012]

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Embodiments for Carrying Out the Invention

[0013] In a blast furnace, ore raw materials such as sintered ore and coke (lump coke) are alternately charged from the top of the furnace to form a charged layer (packed layer) having a layered structure. The amount of one layer of the ore raw material layer and the coke layer is called the ore raw material and coke for one charge, respectively. These ore raw materials and coke for one charge are not necessarily charged into the furnace in one charge each time, and it is also practiced to divide the ore raw materials and coke for one charge into a plurality of times and charge them into the furnace. The divided ore raw materials and coke are called the ore raw materials and coke for one batch, respectively. The raw material charging method of the present invention is applied to an unbell-type blast furnace having a raw material charging device in which a plurality of top bunkers are arranged in parallel and raw materials are charged into the furnace by a revolving chute. In an unbell-type blast furnace, lump coke and ore raw materials cut out from a raw material hopper are charged into separate top bunkers, and they are alternately charged into the furnace through a revolving chute. In the raw material charging in such a blast furnace, in the present invention, ore raw material a and metallic iron raw material b (such as reduced iron) are mixed and charged into the furnace. And, at the time of charging the raw materials, the metallic iron raw material b is selectively charged to a portion (position) where the reduction load is large in the furnace radius direction.

[0014] The ore raw material a in the present invention is a general term for sintered ore, pellets, lump ore, etc. widely used as an iron source for a blast furnace, and the ore raw material a used in the present invention contains at least one of sintered ore, pellets, and lump ore. Further, the metallic iron raw material b in the present invention refers to a raw material having a metallic iron content of 80 mass% or more, and the metallic iron raw material b used in the present invention contains reduced iron and / or granular iron. In addition, although auxiliary raw materials (for example, limestone, silica, serpentine, etc.) mainly for adjusting the components of slag may be mixed in the ore raw material a, the present invention includes such cases. Here, as the reduced iron, it is common to use a molded body of reduced iron. Among them, a reduced iron molded body called HBI (Hot Briquette Iron) is a typical example, but it is not limited to this. This HBI is obtained by hot compression molding (shaping) the reduced iron obtained by reducing ores (lump ore, pellets, etc.) with a reducing gas. In addition, as reduced iron other than HBI, for example, lumpy reduced iron obtained by partially reducing ores such as sintered ore, pellets, and lump ore with a reducing gas; a reduced iron molded body obtained by molding iron-based dust generated in a blast furnace, converter, electric furnace, etc. may also be used. Granular iron is a granular iron material obtained by cooling and solidifying molten iron in a state where it is dispersed into droplets. Generally, it is obtained by dropping the dispersed droplets of molten iron into cooling water for cooling. Usually, its average particle size is about several mm to several tens of mm.

[0015] Figs. 1 and 2 are explanatory diagrams schematically showing an embodiment of the method of the present invention. Among them, Fig. 1 shows the situation from cutting out the raw materials on the charging conveyor to transporting them to the top of the blast furnace, and Fig. 2 shows the situation of transporting the raw materials to the top of the blast furnace by the charging conveyor and charging them into the furnace by the raw material charging device. In the figure, 1 is the furnace body of the blast furnace, 2 is the raw material charging device provided at the top of the furnace, and 3 is the charging conveyor that transports the raw materials to the top of the furnace and supplies them to the raw material charging device 2. The raw material charging device 2 is composed of a plurality of furnace top bunkers 4 arranged in parallel, a swivel chute 5 for charging the raw materials discharged from each furnace top bunker 4 into the furnace, a collecting hopper 6 for supplying the raw materials discharged from each furnace top bunker 4 to the swivel chute 5, and the like. The plurality of furnace top bunkers 4 are arranged in parallel around the furnace central axis x. Therefore, usually, when there are 2 furnace top bunkers 4, they are arranged symmetrically about the furnace central axis x, and when there are 3 or more, they are arranged at intervals (for example, at equal intervals) in the circumferential direction about the furnace central axis x.

[0016] Each top bunker 4 (bunker body) is composed of a cylindrical portion 41 on the upper side and a funnel-shaped portion 42 on the lower side, and a raw material discharge port 40 is provided at its lower end (the lower end of the funnel-shaped portion 42). Here, the raw material discharge port 40 is provided at a position eccentric to the furnace center axis x side (closer to the furnace center axis x) in the furnace radial direction B (provided closer to the furnace center axis x), preferably as close to the furnace center axis x as possible. If the raw material discharge port 40 is provided on the bunker center axis x B When provided above, the side surface shape of the top bunker 4 in the furnace radial direction becomes symmetric. In that case, since the diameter of the collective hopper 6 that receives raw materials from the plurality of top bunkers 4 becomes large, the raw materials tend to flow eccentrically with respect to the central axis of the swivel chute 5, and as a result, the charging center position by the swivel chute 5 is likely to shift. In this embodiment, the wall portion (shell portion) 421 on the side opposite to the furnace center axis x (furnace wall side) of the funnel-shaped portion 42 has an inclination as a funnel-shaped portion, while the wall portion (shell portion) 420 on the furnace center axis x side has a vertical or steeper inclination (an inclination closer to vertical) than the wall portion 421. Thereby, the raw material discharge port 40 is provided at a position eccentric to the furnace center axis x side in the furnace radial direction.

[0017] A flow rate adjustment gate (not shown) is provided at the raw material discharge port 40 at the lower end of each top bunker 4. The raw materials whose flow rate is adjusted by this flow rate adjustment gate and discharged from the raw material discharge port 40 are guided to the swivel chute 5 via the collective hopper 6 and the top ring 7. This swivel chute 5 rotates around the base end portion (upper end portion) located on the furnace center axis x, and while tilting in the furnace diameter direction with the base end portion (upper end portion) as the pivot portion, charges the raw materials into the furnace. 9a is an ore raw material hopper, 10 is a reserving hopper, and 9b is a metallic iron raw material hopper that holds metallic iron raw materials b such as reduced iron. Also, 11 is an ore conveyor, which is a conveyor that conveys the ore raw materials a cut out from the ore raw material hopper 9a to the reserving hopper 10. The raw materials cut out from the above-mentioned raw material hopper are conveyed to the furnace top by the charging conveyor 3 and charged into any one of the top bunkers 4. At this time, as shown by the broken line in Fig. 2 (and Fig. 4 described later), the raw materials fall obliquely downward in a direction away from the furnace center line x through the receiving chute 12 and accumulate in the top bunker 4.

[0018] In the embodiments of Figs. 1 and 2, the ore raw material a is held in the reserving hopper 10 (and the ore raw material hopper 9a), and the metallic iron raw material b is held in the metallic iron raw material hopper 9b. The raw materials held in these hoppers are appropriately cut out onto the charging conveyor 3. In the method of the present invention, when cutting out the ore raw material a onto the charging conveyor 3, conveying it to the furnace top by the charging conveyor 3 and charging it into one of the top bunkers 4, the metallic iron raw material b is cut out and laminated on the ore raw material a conveyed by this charging conveyor 3. At this time, the metallic iron raw material b is laminated on the ore raw material a within the length range w of 50% or less on the leading side in the conveying direction among the loading length L of the ore raw material a loaded on the charging conveyor 3. That is, as shown in Fig. 2, the loading length L of the ore raw material a and the length range w for laminating the metallic iron raw material b are set such that w ≤ 0.5L. Then, the ore raw material a and the metallic iron raw material b are charged into the top bunker 4 in that state.

[0019] Among the loading length L of the ore raw material a loaded on the charging conveyor 3, by laminating the metallic iron raw material b on the ore raw material a within the length range w within 50% on the leading side in the conveying direction, the metallic iron raw material b can be deposited on the lower side of the top bunker 4. For this reason, even considering the funnel flow as shown in FIG. 5, the metallic iron raw material b can be preferentially discharged from the top bunker 4, and the discharge ratio of the metallic iron raw material b at the initial stage of raw material discharge from the top bunker 4 can be increased. Further, as will be described later, when the lamination position of the metallic iron raw material b is set as close as possible to the leading side in the conveying direction within the loading length L of the ore raw material a, the discharge ratio of the metallic iron raw material b at the initial stage of raw material discharge from the top bunker 4 becomes higher. For this reason, it is more preferable to laminate the metallic iron raw material b on the ore raw material a within the length range w within 25% on the leading side in the conveying direction (that is, w≤0.25L in FIG. 2) of the loading length L of the ore raw material a loaded on the charging conveyor 3. Here, the lamination position (range) of the metallic iron raw material b can be arbitrarily selected as long as it is within the length range within 50% on the leading side in the conveying direction, preferably within the length range within 25% on the leading side, of the loading length L of the ore raw material a. Therefore, as the length range within 50% on the leading side in the conveying direction, for example, a length range such as 20 - 40% or 10 - 30% from the leading side in the conveying direction can be selected. Further, as the length range within 25% on the leading side in the conveying direction, for example, a length range such as 10 - 25% or 5 - 20% from the leading side in the conveying direction can be selected.

[0020] Also, the formed product of reduced iron such as HBI among the metallic iron raw material b is obtained by forming reduced iron with a double forming roll or the like, but sharp burrs are formed at the portion corresponding to the gap portion between the forming rolls. If this portion comes into direct contact with the conveyor belt of the charging conveyor 3, it will cause damage to the conveyor belt. Therefore, it is preferable that the metallic iron raw material b is not directly loaded on the charging conveyor 3 even partially, and is loaded (laminated) only on the ore raw material a. Here, when the metallic iron raw material b is laminated up to the foremost part in the conveying direction among the loading lengths L of the ore raw materials a loaded on the loading conveyor 3, there is a risk that a part of the metallic iron raw material b may collapse and be directly loaded on the loading conveyor 3. Therefore, It is preferable not to laminate the metallic iron raw material b on the ore raw materials a in a length range (area) within at least the first 1% on the head side in the conveying direction among the loading lengths L of the ore raw materials a loaded on the loading conveyor 3.

[0021] Therefore, when loading the metallic iron raw material b into the top bunker 4 for charging into the furnace, the following conditions are followed. (i) The metallic iron raw material b is loaded (laminated) only on the ore raw materials a conveyed by the loading conveyor 3 and is not directly loaded on the loading conveyor 3. (ii) The metallic iron raw material b is laminated on the ore raw materials a in a length range w within 50% on the head side in the conveying direction, preferably within 25% on the head side, among the loading lengths L of the ore raw materials a loaded on the loading conveyor 3. (iii) Preferably, the metallic iron raw material b is not laminated on the ore raw materials a in a length range within at least the first 1% on the head side in the conveying direction among the loading lengths L of the ore raw materials a loaded on the loading conveyor 3.

[0022] Furthermore, in the method of the present invention, when loading the raw materials (ore raw materials a and metallic iron raw material b) loaded into the top bunker 4 as described above into the furnace by the swivel chute 5, while rotating the swivel chute 5, the swivel chute 5 is tilted and the raw material loading position is sequentially moved from the middle part of the furnace to the furnace wall part side while loading the raw materials. That is, while rotating the swivel chute 5, the raw materials are loaded while sequentially shifting (tilting) the direction of the chute from the middle part of the furnace to the furnace wall part side. FIG. 3 schematically shows the raw material loading situation through this swivel chute 5. As shown in the figure, the raw material loading by the swivel chute 5 starts from the loading into the middle part of the furnace, and while rotating the swivel chute 5, the raw materials are loaded while sequentially tilting from the direction of loading into the middle part of the furnace (two-dot chain line) to the direction of loading to the furnace wall part (peripheral part of the furnace wall) side (solid line).

[0023] Here, the metallic iron raw material b is preferably deposited in the middle part of the blast furnace for the following reasons. In a blast furnace, ores are reduced by the reducing gas rising from the lower part of the furnace. Usually, the layer thickness of the ore raw material layer in the blast furnace increases in the middle part of the furnace, and accordingly, the consumption of the reducing gas increases, so the reducing gas concentration decreases, and the reduction rate in the middle part of the furnace decreases. Such a decrease in the reduction rate in the middle part of the furnace leads to a decrease in the reduction rate of the entire ore raw material layer. Since the ore raw material melts at the lower part of the blast furnace in such a state with a low reduction rate and is finally reduced by a direct reduction reaction involving a large endotherm, it causes an increase in the required amount of fuel in the blast furnace, that is, the required amount of coke. On the other hand, by charging the metallic iron raw material b as a raw material in which reduction has already proceeded into the middle part of the furnace, it becomes possible to compensate for the insufficient reduction in the middle part of the furnace.

[0024] As described above, in the method of the present invention, the metallic iron raw material b is preferentially discharged at the initial stage of raw material discharge from the top bunker 4, and the raw materials are deposited in the top bunker 4 so that the discharge ratio of the metallic iron raw material b becomes high. Therefore, by starting the raw material charging by the swivel chute 5 from the charging into the middle part of the furnace and performing the raw material charging while sequentially shifting (tilting) the direction of the chute from the middle part of the furnace to the furnace wall part side, it becomes possible to deposit the metallic iron raw material b in the middle part of the furnace at a high mixing ratio. Here, in the present invention, the middle part of the furnace is a region between the peripheral part around the furnace center and the furnace wall part (peripheral part of the furnace wall) in the furnace radial direction, and generally refers to a region with a dimensionless radius (r / R0, the same hereinafter) of 0.30 to 0.80. Also, generally, the peripheral part around the furnace center refers to a region with a dimensionless radius of less than 0.20 to 0.30, and the furnace wall part refers to a region with a dimensionless radius exceeding 0.80 to 1.00. Here, the dimensionless radius (r / R0) indicates the position inside the furnace in the furnace radial direction, and is a value obtained by dividing the distance r from the furnace center at that position by the furnace radius R0. In the present invention, the position where the raw material charging is started may be appropriately determined within the above-mentioned middle part of the furnace. However, generally, the position where the raw material charging is started in the middle part of the furnace (the center of raw material drop from the swivel chute on the raw material deposition surface inside the furnace) is preferably in the range of a dimensionless radius of 0.30 to 0.70, and more preferably in the range of 0.40 to 0.60.

[0025] In the method of the present invention, there is no special restriction on the charging amount (mixing ratio) of the metallic iron raw material b, and the reduction material ratio can be reduced as the charging amount of the metallic iron raw material b is increased. However, as the charging amount of the metallic iron raw material b increases, the heat flux ratio decreases. Generally, the operation of the blast furnace is preferably carried out with a heat flux ratio of 0.9 or less. In a normal blast furnace (with an ore charging amount of about 1600 kg / t), this range is achieved at 400 kg / t or more, and since the temperature rise delay of the raw materials occurs, the effect of reducing the reduction material ratio is diminished. Therefore, it is preferable to suppress the charging amount (mixing ratio) of the metallic iron raw material b to 25 mass% or less of the ore raw material a.

[0026] Next, a more preferable embodiment of the method of the present invention will be described. In the method of the present invention, a segregation control plate 8 is installed in the top bunker 4, and the charging form of the metallic iron raw material b can be made more appropriate by this segregation control plate 8. That is, the metallic iron raw material b having a larger particle size than the ore raw material a can be segregated to the lower part in the top bunker 4 by this segregation control plate 8, and at the initial stage of raw material discharge from the top bunker 4, the metallic iron raw material b can be preferentially discharged at a higher ratio. HBI, which is a typical metallic iron raw material b, generally has a considerably larger particle size than ore, so when using HBI as the metallic iron raw material b, it is advantageous in that regard. In any case, when segregating the metallic iron raw material b to the lower part in the top bunker 4 using the segregation control plate 8, as will be described later, the average particle size [d O of the ore raw material a and the average particle size [d M of the metallic iron raw material b are preferably set such that [d O <[d M .

[0027] FIG. 4 schematically shows an embodiment in the method of the present invention where a segregation control plate 8 is installed in the top bunker 4 and the metallic iron raw material b is segregated to the lower part in the top bunker 4 by this segregation control plate 8. The front surface of the segregation control plate 8 constitutes a raw material receiving surface 80 for receiving the raw materials falling from above. The segregation control plate 8 is disposed in the upper space of the top bunker 4 and is supported so as to be tiltable up and down about a pivot support portion 81. The orientation of this segregation control plate 8 is set such that its raw material receiving surface 80 faces the outside of the furnace in the furnace radial direction and is inclined downward with respect to the outside of the furnace. When loading the ore raw material a and the metallic iron raw material b from the charging conveyor 3 into the top bunker 4 of the furnace, the raw materials falling from above are made to fall downward via the raw material receiving surface 80 of the segregation control plate 8 (that is, after being received by the raw material receiving surface 80 once) and are deposited in the bunker.

[0028] The raw materials charged from the charging conveyor 3 into the top bunker 4 through the receiving chute 12 fall obliquely downward in a direction away from the furnace central axis x. Then, by receiving this raw material once on the raw material receiving surface 80 of the segregation control plate 8 and then making it fall (changing the falling direction), the raw material falls to a position away from the furnace central axis x and then rolls toward the furnace central axis x side to form a slope. At this time, the larger the particle size of the raw material, the easier it is to flow downward into the slope and the easier it is to segregate to the lower side of the bunker (above the raw material discharge port 40). Also, the smaller the particle size of the raw material, the easier it is to accumulate at a position away from the furnace central axis x, and the larger the particle size of the raw material, the more likely it is to accumulate (segregate) closer to the furnace central axis x. Here, Fig. 5 shows the raw material discharge behavior of the top bunker 4 provided in parallel at the top of the bell-less blast furnace. In Fig. 5, the numbers in the top bunker 4 represent the discharge ratio (mass%) of the raw materials at each position. The raw materials at each position are discharged in ascending order of the numbers, and the numbers indicate the cumulative discharge ratio at the time when the raw materials at each position are discharged. As is clear from this Fig. 5, the discharge behavior is funnel flow, and the order in which the raw materials loaded into the top bunker 4 are discharged differs depending on the position. However, the raw materials deposited at the lower position of the bunker and slightly closer to the furnace central axis x (the lower region at the "22" position in Fig. 5) are preferentially discharged from the top bunker (almost the first to be discharged) compared to the raw materials at other positions.

[0029] Therefore, generally, the particle size of the metallic iron raw material b (especially in the case of HBI) is larger than that of the ore raw material a. Thus, by using the segregation control plate 8 as described above, it is possible to deposit the metallic iron raw material b at a position where the discharge ratio of the metallic iron raw material b at the initial stage of raw material discharge becomes higher. For this reason, although it is affected by the funnel flow in the top bunker 4, by preferentially discharging the metallic iron raw material b from the top bunker 4 at the initial stage of raw material discharge, the discharge ratio of the metallic iron raw material b at the initial stage of raw material discharge can be increased. Since the segregation control plate 8 only needs to receive the raw materials falling from above and guide them to fall in a direction away from the furnace central axis x, the inclination angle of the segregation control plate 8 (raw material receiving surface 80) may be set at an appropriate angle that enables this. However, if the inclination angle θ of the raw material receiving surface 80 with respect to the horizontal plane is too small, the raw materials cannot slide down well. On the other hand, if the inclination angle θ is too large, it becomes difficult to guide the raw materials in a direction away from the furnace central axis x. Therefore, the inclination angle θ is preferably about 7 to 47°, more preferably about 7 to 37°. As described above, by using the segregation control plate 8, the discharge ratio of the metallic iron raw material b from the top bunker 4 at the initial stage of raw material discharge can be increased, and accordingly, it becomes possible to more reliably deposit the metallic iron raw material b at a desired part (position) in the middle part of the furnace. Also, by using the segregation control plate 8, the ore raw material a is likely to deposit coarse particles in the middle part of the furnace and fine particles are likely to deposit on the furnace wall part. As a result, for example, when coke is mixed with the ore raw material a as a reduction promoting material, the particle size difference between the coke and the ore raw material a in the middle part of the furnace is reduced, so that the segregation of the coke to the center part of the furnace can be suppressed.

[0030] As described above, when using the segregation control plate 8, in order to obtain the segregation effect in the top bunker 4 as described above, the average particle size [d O of the ore raw material a and the average particle size [d M of the metallic iron raw material b are preferably [d O <[d M . As described above, generally, the particle size of HBI, which is a typical metallic iron raw material b, is considerably larger than that of the ore. Also, in order to obtain a sufficient segregation effect, [d O×1.5 ≦ [d M is preferably at such a level. On the other hand, if [d M is too large, there is a risk that the discharge from the bunker may be physically inhibited. Therefore, [d O ×7 ≧ [d M is preferably at such a level. Here, the average particle size [d O of the ore raw material a is the harmonic mean diameter in the case of any raw material such as sintered ore, pellets, and lump ore, and the average particle size = 1 / Σ(Wi / di) (where Wi: the weight ratio of particles with particle size di, di: the median diameter of each sieve mesh). When the ore raw material a consists of two or more raw materials (for example, two or more raw materials among sintered ore, pellets, and lump ore), after obtaining the average particle size for each, the average particle size weighted by the weight ratio is obtained.

[0031] The average particle size [d M of the metallic iron raw material b is obtained as follows in the case of HBI. Measure the size of the HBI sampled from the lot of HBI to be used. When approximating the size as a rectangular parallelepiped with length a, width b, and thickness c, calculate the particle size dr (equivalent diameter of an equal-volume sphere) from the following formula. Perform this for 20 randomly sampled HBIs, and take the average value as the average particle size [d M of the metallic iron raw material b.

Number

[0032] When the metallic iron raw material b is reduced iron other than HBI, or granular iron ore, etc., the average particle size [d M is determined in the same manner as the average particle size [d O of the ore raw material a described above. Also, when the metallic iron raw material b consists of two or more raw materials (for example, two or more types of reduced iron, or reduced iron and granular iron ore), after determining the average particle size for each, the average particle size weighted by the weight ratio is determined. Incidentally, the segregation phenomenon of the metallic iron raw material b in the top bunker 4 described earlier (the segregation phenomenon when using the segregation control plate 8) is also affected by the density difference between the metallic iron raw material b and the ore raw material a in the raw material layer. That is, an appropriate density difference (metallic iron raw material b > ore raw material a) works favorably for the segregation of the metallic iron raw material b, but if the density difference is too large, the metallic iron raw material b may sink into the ore raw material a, so there is a risk that the segregation of the metallic iron raw material b will be inhibited. However, even when the metallic iron raw material b is HBI, usually its density (apparent density) is 1.5 times or less that of the ore raw material a (for example, sintered ore: 3600 kg / m 3 vs. HBI: 5500 kg / m 3 ), so there is almost no risk that the segregation of the metallic iron raw material b will be inhibited due to the density difference.

[0033] The metallic iron raw material b is preferably deposited on the upper part of the ore raw material layer in the middle part of the blast furnace for the following reasons. In a blast furnace, since the ores are reduced by the reducing gas rising from the lower part of the furnace, the ores located at the upper part of the ore raw material layer are reduced by the gas whose reducing power has decreased while passing through the ore raw material layer, and the reduction rate decreases. The reduction rate decrease of the ore raw materials at such a specific site leads to a decrease in the reduction rate of the entire ore raw material layer. On the other hand, by mixing (depositing) the metallic iron raw material b as a raw material in which reduction has already progressed on the upper part of the ore raw material layer in the middle part of the furnace, it becomes possible to compensate for the insufficient reduction at the upper part of the ore raw material layer. In the method of the present invention, in order to deposit the metallic iron raw material b on the upper part of the ore raw material layer in the middle part of the blast furnace, it is preferable to divide the ore raw material a for one charge into two parts and charge each into a different furnace top bunker 4, and then charge them into the furnace sequentially via the swing chute 5. That is, the ore raw material a for one charge is charged into the furnace in two batches. In that case, if the metallic iron raw material b is mixed with the ore raw material a of the second batch and charged into the furnace by the method described above, it becomes possible to deposit the metallic iron raw material b on the upper part of the ore raw material layer in the middle part of the blast furnace. Fig. 6 schematically shows the shape (cross section) of the deposit in the furnace when the raw materials are charged by such a method. In this case, it is more preferable not to mix the metallic iron raw material b with the ore raw material a of the first batch because it becomes possible to compensate for the insufficient reduction at the upper part of the ore raw material layer. Also, for the ore raw material a of the first batch, the raw material charging is performed by moving the raw material charging position from around the center part of the furnace to the furnace wall side.

[0034] The inventors of the present invention conducted the following experiments using a scale model of a blast furnace charging device in order to verify the laminating conditions of the metallic iron raw material b on the ore raw material a conveyed by the charging conveyor 3. Figure 7 schematically shows a 1 / 17.8 model experimental apparatus of an actual blast furnace used in this experiment. This simulation experimental apparatus is composed of a blast furnace body 21, a bell-less type raw material charging device 22, a charging conveyor 23, raw material hoppers 29 (raw material hopper 29a for ore raw materials, raw material hopper 29b for metallic iron raw materials), etc., in order to reproduce the change over time of the raw material discharge of the actual machine. Further, the raw material charging device 22 is composed of a top bunker 24, a swivel chute 25, a collecting hopper 26, a top ring 27, etc., and a flow rate adjusting gate is provided at the raw material discharge port 240 of the top bunker 24. Two top bunkers 24 are arranged symmetrically with respect to the furnace central axis x0. Although not shown, a segregation control plate as shown in FIG. 4 is installed in the top bunker 24, and the inclination angle θ of its raw material receiving surface is set to 27°.

[0035] Sintered ore was used as the ore raw material a, and hot briquetted iron (HBI) was used as the metallic iron raw material b. Other experimental conditions and raw material conditions were determined according to the similarity law with the actual blast furnace. When the raw materials cut out from the raw material hopper 29 are conveyed to the top of the furnace by the charging conveyor 23 and charged into the top bunker 24, the ore raw materials are divided into two and charged into separate top bunkers 24, and charged into the furnace body 21 in two batches. At that time, the hot briquetted iron was mixed only in the second batch and not in the first batch. In both the first batch and the second batch, the raw materials cut out from the top bunker 24 were charged into the furnace body 21 through the swivel chute 25. In the second batch in which the hot briquetted iron was mixed, while the swivel chute 25 was swiveled, it was tilted to move the raw material charging position from the middle part of the furnace to the furnace wall side while charging the raw materials (tilting pattern = reverse tilt). The start position of the raw material charging in the second batch by the swivel chute 25 was set at each position with a dimensionless radius of 0.50 and the end position with a dimensionless radius of 0.95 (the center position of the raw material drop from the swivel chute on the raw material accumulation surface in the furnace).

[0036] In this experiment, for the raw materials in the second batch, when cutting out and stacking the hot briquetted iron on top of the ore raw materials on the charging conveyor 23, the cutting length of the hot briquetted iron to be stacked was made into the three forms shown in (a) to (c) of FIG. 8, and charged into the top bunker 24 respectively. The details of each condition are as follows. Form (a): Reduced iron was laminated on the ore raw materials over the entire length of the loading length of the ore raw materials loaded on the charging conveyor 23. Form (b): Reduced iron was laminated on the ore raw materials within the length range of the first 50% in the conveying direction of the loading length of the ore raw materials loaded on the charging conveyor 23. Form (c): Reduced iron was laminated on the ore raw materials within the length range of the first 25% in the conveying direction of the loading length of the ore raw materials loaded on the charging conveyor 23.

[0037] After the charging of the raw materials from the top bunker 24 into the blast furnace was completed, the charge was sampled in the furnace radius direction, and the mixing ratio of the reduced iron was measured. The results are shown in Fig. 9. The horizontal axis of Fig. 9 is the dimensionless radius of the blast furnace, and the vertical axis represents the mixing ratio on a weight basis of the reduced iron. According to Fig. 9, in the second batch with the reduced iron mixed, since the raw materials are charged with reverse tilting from the middle part of the furnace toward the furnace wall side, no mixing of the reduced iron is observed at the furnace center in any of Forms (a) to (c). On the other hand, when the length range for laminating the reduced iron is changed, the shorter the length range for lamination and the more it gathers on the leading side (Form (a) → Form (b) → Form (c)), the higher the mixing ratio of the reduced iron at the middle part of the furnace becomes. This is presumably because the closer the lamination position of the reduced iron is to the leading side of the ore raw materials, the higher the mixing rate of the reduced iron at the initial stage of discharge when discharging from the top bunker. Also, in terms of the high mixing ratio of the reduced iron in the middle part of the furnace with a high reduction load, it can be said that Form (c) in which the reduced iron is laminated within the length range of the first 25% of the loading length of the ore raw materials is particularly preferable.

[0038] Also, the change over time in the particle size distribution of the ore raw materials when discharged from the top bunker 24 was examined. As a result, it was found that even if the lamination length of the reduced iron with respect to the ore raw materials on the charging conveyor 23 is changed, the influence on the change over time in the particle size distribution of the ore raw materials when discharged from the top bunker 24 is small. As described above, by mixing the ore raw material a and the metallic iron raw material b according to the method of the present invention, it becomes possible to control the mixing ratio of the metallic iron raw material b at the time of tapping the top bunker. Thereby, the metallic iron raw material b can be selectively charged into the middle part of the furnace (preferably, the upper part of the ore raw material layer in the middle part of the furnace) where the reduction load is large. Further, the hot metal production method of the present invention includes a step of mixing an ore raw material a containing at least one of sintered ore, pellet, and lump ore and a metallic iron raw material b containing reduced iron and / or granular hot metal, and charging the mixture into a blast furnace, by the raw material charging method of the present invention described above.

Example

[0039] In order to confirm the effects of the present invention in an actual machine, an operation test was conducted in a large bell-less blast furnace (internal volume: 5500 m 3 ) having an equipment configuration as shown in FIGS. 1 and 2. The raw material charging device 2 installed at the top of the blast furnace is provided with three top bunkers 4 arranged in parallel, and these three top bunkers 4 are arranged at equal intervals in the circumferential direction around the furnace center axis x of the blast furnace. In the top bunker 4, a segregation control plate 8 as shown in FIG. 4 is installed, and the inclination angle θ of the raw material receiving surface 80 is set to 27°. Sintered ore was used as the ore raw material, and reduced iron (HBI) was used as the metallic iron raw material. The average particle size [d O of the ore raw material was 12 mm, the average particle size [d M of the reduced iron was 72 mm, and [d M / [d O =6.0. The mixing ratio of the reduced iron was 4 mass% of the ore raw material.

[0040] The ore raw materials cut out from the raw material hopper 9a and passing through the reserving hopper 10 were conveyed to the top of the furnace by the charging conveyor 3 and charged into the top bunker 4. In this embodiment, the ore raw materials for one charge were divided into two portions and charged into separate top bunkers 4, and charged into the blast furnace in two batches. At that time, reduced iron was cut out from the raw material hopper 9b and laminated on the ore raw materials of the second batch conveyed by the charging conveyor 3, and mixed with the ore raw materials and charged into one of the top bunkers 4. On the other hand, no reduced iron was mixed into the ore raw materials of the first batch. For both the first batch and the second batch, the raw materials cut out from the top bunker 4 were charged into the furnace through the swivel chute 5. In the second batch with reduced iron mixed, while the swivel chute 5 was swiveled and tilted, the raw materials were charged while moving the raw material charging position from the middle part of the furnace to the furnace wall side (tilting pattern = reverse tilting). The starting position of the raw material charging of the second batch by the swivel chute 5 was set at each position with a dimensionless radius of 0.50, and the ending position was set at a dimensionless radius of 0.95 (the center position of raw material falling from the swivel chute on the raw material accumulation surface in the furnace).

[0041] In Invention Example 1, when charging the ore raw materials of the second batch into the top bunker 4, reduced iron was laminated on the ore raw materials loaded on the charging conveyor 3 as follows. Among the loaded length of the ore raw materials loaded on the charging conveyor 3, 60 kg / t of reduced iron was cut out and laminated on the ore raw materials in the length range of 50% on the leading side in the conveying direction (excluding the length range of 4% on the foremost side) (form (b) in FIG. 8). In Invention Example 2, when charging the ore raw materials of the second batch into the top bunker 4, reduced iron was laminated on the ore raw materials loaded on the charging conveyor 3 as follows. Among the loaded length of the ore raw materials loaded on the charging conveyor 3, 60 kg / t of reduced iron was cut out and laminated on the ore raw materials in the length range of 25% on the leading side in the conveying direction (excluding the length range of 4% on the foremost side) (form (c) in FIG. 8). In the comparative example, when charging the ore raw materials of the second batch into the top bunker 4, reduced iron was laminated on the ore raw materials loaded on the charging conveyor 3 as follows. Reduced iron of 60 kg / t was cut out and laminated on the ore raw materials over the entire length of the loaded length of the ore raw materials loaded on the charging conveyor 3 (excluding the length ranges of the 4% at the frontmost side and the 4% at the rearmost side) (form (a) in Fig. 8).

[0042] Table 1 shows the operating conditions of the inventive examples and the comparative example, and the measurement results of the ventilation resistance index, gas utilization rate, and hot metal temperature. According to this, in Inventive Examples 1 and 2, since reduced iron could be arranged (charged) at a high mixing rate above the ore raw material layer in the middle part of the furnace, the improvement of the reducing power shortage and the stability of the gas flow distribution resulted in a reduction in the ventilation resistance index and a decrease in the reducing agent ratio compared with the comparative example. Among them, Inventive Example 2, in which reduced iron was laminated in the length range on the more frontmost side of the loaded length of the ore raw materials conveyed by the charging conveyor 3, has a great effect. As described above, in the raw material charging method of the present invention, since the radial distribution of the reduced iron mixed in the ore raw materials is optimized, it was confirmed that it is effective for the stable operation of the blast furnace and further effective for the operation with a lower reducing agent ratio.

[0043]

Table 1

Explanation of symbols

[0044] 1 Furnace body 2 Raw material charging device 3 Charging conveyor 4 Top bunker 5 Swivel chute 6 Aggregate hopper 7 Top ring 8 Segregation control plate 9a Ore raw material hopper 9b Metallic iron raw material hopper 10 Reservoir hopper 11 Ore conveyor 12 Receiving chute 21 Furnace body 22 Raw material charging device 23 Charging conveyor 24 Top bunker 25 Swivel chute 26 Aggregate hopper 27 Top ring 29a, 29b Raw material hoppers 40 Raw material discharge port 41 Cylindrical part 42 Funnel-shaped part 80 Raw material receiving surface 81 Pivot support part 240 Raw material discharge port 420, 421 Wall parts a Ore raw materials b Metallic iron raw materials x, x0 Furnace central axis x B Bunker central axis

Claims

1. In a bell-less blast furnace having a raw material charging device in which a plurality of top bunkers are arranged in parallel and raw materials are charged into the furnace through a swivel chute, a method of mixing ore raw materials (a) containing at least one of sintered ore, pellets, and lump ore and metallic iron raw materials (b) containing reduced iron or / and granular pig iron and charging the mixture into the blast furnace, when the ore raw materials (a) are conveyed to the top of the furnace by a charging conveyor and charged into one of the top bunkers, by cutting out the metallic iron raw materials (b) on top of the ore raw materials (a) conveyed by the charging conveyor, the metallic iron raw materials (b) are laminated on the ore raw materials (a) within a length range of 50% or less from the leading side in the conveying direction among the loaded length of the ore raw materials (a) loaded on the charging conveyor, and in that state, the ore raw materials (a) and the metallic iron raw materials (b) are charged into the top bunker, when charging the raw materials in the top bunker into the furnace by the swivel chute, while rotating the swivel chute and tilting it to move the raw material charging position from the middle part of the furnace to the furnace wall side, charging the raw materials, which is a method for charging raw materials into a blast furnace.

2. When the ore raw materials (a) are conveyed to the top of the furnace by the charging conveyor and charged into one of the top bunkers, the metallic iron raw materials (b) are laminated on the ore raw materials (a) within a length range of 25% or less from the leading side in the conveying direction among the loaded length of the ore raw materials (a) loaded on the charging conveyor, which is a method for charging raw materials into a blast furnace according to Claim 1.

3. When charging the ore raw materials (a) for one charge into the furnace in two batches, mixing the metallic iron raw materials (b) with the ore raw materials (a) for the second batch and charging them into the furnace, which is a method for charging raw materials into a blast furnace according to Claim 1 or 2.

4. Charging the ore raw materials (a) for the first batch into the furnace without mixing the metallic iron raw materials (b), which is a method for charging raw materials into a blast furnace according to Claim 3.

5. A segregation control plate is installed in the top bunker, when charging the ore raw materials (a) and the metallic iron raw materials (b) conveyed by the charging conveyor into the top bunker, with the raw material receiving surface of the segregation control plate facing the outside of the furnace in the furnace radius direction and inclined downward with respect to the outside of the furnace, dropping the raw materials falling from above through the raw material receiving surface of the segregation control plate and depositing them in the bunker, which is a method for charging raw materials into a blast furnace according to Claim 1 or 2.

6. Average particle size [d of the metallic iron raw material (b) Ｍ and the average particle size [d of the ore raw material (a) Ｏ are such that [d Ｍ > [d Ｏ , and the method for charging raw materials into a blast furnace according to claim 5 is characterized by this.

7. When the ore raw material (a) is conveyed to the furnace top by the charging conveyor and charged into one of the furnace top bunkers, among the loaded lengths of the ore raw material (a) loaded on the charging conveyor, the metal iron raw material (b) is not laminated on the ore raw material (a) within a length range of at least 1% on the leading side in the conveying direction. The method for charging raw materials into a blast furnace according to claim 1 or 2, characterized in that.

8. A method for producing hot metal, comprising a step of mixing an ore raw material (a) containing at least one of sintered ore, pellets, and lump ore and a metal iron raw material (b) containing reduced iron or / and granular pig iron and charging the mixture into a blast furnace by the raw material charging method according to claim 1 or 2.

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