Method for understanding changes in blast furnace raw materials over time

Abstract

The present invention aims to provide a method for accurately measuring information regarding the charging weight and particle size of blast furnace raw materials in a bellless blast furnace. [Solution] A method for understanding changes in blast furnace raw materials over time by analyzing blast furnace raw materials charged into a bellless blast furnace, comprising: a sampling step in which a swirling chute is rotated while the blast furnace is shut down, and the blast furnace raw materials falling from the swirling chute toward the furnace deposit surface are collected at a predetermined position in the circumferential direction of the furnace and transported out of the furnace; and a time-series change understanding step in which the blast furnace raw materials transported out in the sampling step are analyzed to obtain raw material information including information on particle size and charging weight for each type of blast furnace raw material, thereby understanding changes in the blast furnace raw materials over time.

Description

Technical Field

[0001] The present invention relates to a method for grasping the change over time of blast furnace raw materials.

Background Art

[0002] In blast furnace operation, generally, from the top of the furnace, sintered ore, pellets, lump ore, etc. (hereinafter, also collectively referred to as "iron raw materials") as iron sources, and coke as a reducing agent and fuel are alternately charged in layers. The iron raw materials and coke charged from the top of the furnace (hereinafter, also collectively referred to as "blast furnace raw materials") are alternately stacked to form ore layers and coke layers. The blast furnace raw materials may contain auxiliary raw materials such as peridotite and silica.

[0003] In order to achieve stable operation of the blast furnace, it is necessary to keep the air permeability in the furnace good. Therefore, it is important to make the void distribution of the deposited layer in the furnace approach the appropriate value. The void distribution of the deposited layer in the furnace is greatly affected by the weight ratio distribution in the furnace diameter direction of the iron raw materials and coke in the deposited layer in the furnace (hereinafter, referred to as the deposited O / C distribution), and the particle size distribution of the blast furnace raw materials in the deposited layer in the furnace in the furnace diameter direction and the height direction (hereinafter, referred to as the deposited blast furnace raw material particle size distribution). In a bell-less blast furnace, by rotating while controlling the tilt angle and the number of rotations of the rotary chute and adjusting the charging position, the deposited O / C distribution and the deposited blast furnace raw material particle size distribution can be adjusted.

[0004] By measuring the deposited shape of the deposited layer in the furnace with a profiler, the deposited O / C distribution in the furnace can be confirmed, but the deposited blast furnace raw material particle size distribution cannot be measured. Furthermore, there is often a difference between the deposited O / C distribution confirmed by the profile meter and the target deposited O / C distribution aimed at bringing the void distribution of the in-furnace deposited layer closer to the appropriate value. After diligent investigation into the reasons for this, the inventors concluded that particle size segregation occurs when the blast furnace material is transported and stored in the top bunker before charging, and the particle size distribution changes over time as the blast furnace material is charged from the top bunker into the blast furnace. As a result, the particle size distribution of the deposited blast furnace material differs depending on the charging timing and charging location, and consequently, the deposited O / C distribution deviates from the target. Therefore, the inventors considered it necessary to measure information regarding the charging weight and particle size of the blast furnace raw materials before the charged blast furnace raw materials accumulate in the furnace (i.e., at the time when the blast furnace raw materials are dropped in).

[0005] Here, as a conventional method for estimating the particle size distribution of blast furnace raw materials to be charged, Patent Document 1 describes a method in which a measuring device such as a television camera is installed in the top bunker of a bellless blast furnace to measure the particle size distribution of the blast furnace raw materials stored in the top bunker, and the particle size distribution of the blast furnace raw materials to be charged is estimated based on this. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 59-155706 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the method described in Patent Document 1 lacked sufficient accuracy because it used images captured by a television camera or the like to estimate the particle size distribution of the blast furnace raw materials being charged. Furthermore, the method described in Patent Document 1 lacked sufficient accuracy from this perspective as well, as it made it difficult to distinguish the raw material composition from the images when iron raw materials containing reduction aids such as small coke lumps were used. If a particle size distribution estimation method with insufficient accuracy is used, it naturally becomes difficult to properly approximate the void distribution of the in-furnace deposit layer.

[0008] In light of these points, there is a need for a means to more directly obtain raw material information, such as information on the charging weight and particle size of each type of blast furnace material toward the furnace deposit surface, in a bellless blast furnace. [Means for solving the problem]

[0009] To solve the above problems, the present invention provides a method for understanding changes in blast furnace raw materials over time, comprising: (1) a sampling step in which a swirling chute is rotated while the blast furnace is shut down, and the blast furnace raw materials falling from the swirling chute toward the furnace deposit surface are collected at a predetermined position in the circumferential direction of the furnace and transported out of the furnace; and a time-series change understanding step in which the blast furnace raw materials transported out in the sampling step are analyzed to obtain raw material information including at least information on particle size and charging weight for each type of blast furnace raw material, thereby understanding changes in the blast furnace raw materials over time.

[0010] (2) The method for determining changes in blast furnace raw materials over time according to (1) above, wherein the raw material information further includes the bulk density of the blast furnace raw materials.

[0011] (3) In the sampling step, the tilt angle of the rotating chute is fixed to a predetermined value. A method for determining changes in blast furnace raw materials over time, as described in (1) or (2) above, characterized by the above. [Effects of the Invention]

[0012] According to the present invention, in a bellless blast furnace, raw material information such as the charging weight and particle size of blast furnace raw materials toward the furnace deposit surface can be obtained more directly. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram of the bellless blast furnace in this embodiment. [Figure 2] This flowchart shows the method for understanding the changes in blast furnace raw materials over time according to this embodiment. [Figure 3] This is the subroutine for the sampling process (S10) shown in Figure 2. [Figure 4] This is a subroutine for the process of understanding changes over time (S20), as shown in Figure 2. [Figure 5] This shows the time evolution of Dn / Dave in the sintered ore in the examples. [Figure 6] This shows the time change in the charging weight ratio of small coke lumps in the example. [Figure 7] This shows the time change in the weight ratio of iron raw materials charged in the example. [Figure 8] This shows the time change in the weight ratio of small coke lumps to iron raw materials, calculated based on Figures 6 and 7. [Modes for carrying out the invention]

[0014] <Outline configuration of a blast furnace> Figure 1 is a schematic diagram of a bellless blast furnace in this embodiment. Referring to Figure 1, in blast furnace 1, the blast furnace raw materials are carried up to the top of the furnace by the charging conveyor 2 and then stored in the top charging device 3. The blast furnace raw materials include iron raw materials, auxiliary materials, and coke. The iron raw materials include lump ore, sintered ore, pellets, and uncalcined carbon-containing lump ore. The auxiliary materials include olivine and silica. The coke may include small lump coke and ferrocoke.

[0015] The top charging device 3 includes fixed hoppers 4a and 4b. Iron raw materials are stored in the fixed hopper 4a, and coke is stored in the fixed hopper 4b. However, the configuration of the top charging device 3 is not limited to this. For example, it may be configured to store iron raw materials and coke in the same fixed hopper. Since it is common technical knowledge that the top charging device 3 includes various forms, detailed description is omitted.

[0016] The revolving chute 5 rotates around the axis RA extending in the vertical direction, and alternately charges the iron raw materials and coke discharged from the top charging device 3 in layers. Hereinafter, the iron raw materials charged in layers may be referred to as ore dumps, and the coke charged in layers may be referred to as coke dumps. Small pieces of coke may be included in the ore dumps. In the actual operation of the blast furnace, by controlling the driving method (forward tilting / reverse tilting), tilting angle, and rotation speed of the revolving chute 5, the blast furnace raw materials are charged to the desired position. Note that forward tilting refers to a driving method in which the revolving chute 5 is driven from the furnace wall side toward the furnace center side, and reverse tilting refers to a driving method in which the revolving chute 5 is driven from the furnace center side toward the furnace wall side.

[0017] <Method for grasping the change over time of blast furnace raw materials according to the present invention> FIG. 2 is a flowchart for explaining the method for grasping the change over time of blast furnace raw materials according to the present invention. The steps described in such a flowchart are carried out during the shutdown of the blast furnace 1. In the sampling step of S10, the revolving chute 5 is rotated, and the blast furnace raw materials falling from the revolving chute 5 toward the in-furnace deposition surface are collected at a predetermined circumferential position of the furnace and carried out of the furnace.

[0018] The recovery process of the blast furnace raw materials is carried out by the sampling conveyor 6 that can enter and exit the furnace of the blast furnace 1. The insertion position of the sampling conveyor 6 is below the revolving chute 5 and above the in-furnace deposition surface. The in-furnace deposition surface refers to the deposition surface of the blast furnace raw materials deposited in the furnace during the operation of the blast furnace. Each time the rotating chute 5 reaches a predetermined position in the circumferential direction of the furnace, the blast furnace raw materials dropped in from the rotating chute 5 are transported out of the furnace via the sampling conveyor 6 and collected in the collection box 7.

[0019] In this embodiment, only one sampling conveyor 6 is inserted, and the blast furnace material falling from the rotating chute 5 toward the furnace deposit surface is collected after each rotation. However, the number of sampling conveyors 6 inserted is not limited to this, and two or more sampling conveyors 6 may be inserted into the furnace. Furthermore, the frequency of blast furnace material collection is not limited to after each rotation, but may be configured to collect the blast furnace material once every multiple rotations.

[0020] In the sampling process S10, it is preferable to rotate the swivel chute 5 while fixing the tilt angle to a predetermined value. This is because the purpose is to sample the blast furnace raw materials being charged into the blast furnace and to understand the changes in the blast furnace raw materials over time, and therefore it is not necessary to change the tilt angle as in actual operation. However, the present invention may also include a mode in which the swivel chute 5 is rotated while changing the tilt angle, as in actual operation. The predetermined value of the inclination angle should be set appropriately according to the position of the sampling conveyor 6 inserted into the furnace. In other words, the inclination angle should be set so that the charged blast furnace material is placed on the sampling conveyor 6.

[0021] The width of the sampling conveyor 6 should be set to an appropriate length (for example, 20 cm to 60 cm, more preferably approximately 30 cm) that is sufficient to recover the blast furnace raw materials being charged. In this embodiment, a conveyor is used as the sampling device, but the form of the sampling device is not limited to this, and various devices capable of recovering blast furnace raw materials at a predetermined position in the circumferential direction of the furnace can be used.

[0022] In the S20 process for understanding changes over time, the blast furnace raw materials recovered in S10 are analyzed to obtain raw material information for each recovery timing in S10 (in this embodiment, each rotation) and to understand the changes in the blast furnace raw materials over time.

[0023] The raw material information obtained in S20 includes information on the particle size and charging weight for each type of blast furnace raw material recovered in S10. Here, "type of blast furnace raw material" may be classified by its role in the blast furnace (iron raw material / auxiliary raw material / coke) or by brand name (e.g., sintered ore / pellets / lump ore / uncalcined carbon-containing agglomerate / olivine / silica / coke / ferrocoke, etc.).

[0024] (Information regarding particle size for each type of blast furnace raw material) In ore dumping, the particle size of each brand of iron raw material may be referred to as "information on particle size for each type of blast furnace raw material," or the particle size of iron raw material (not separated by brand) may be referred to as "information on particle size for each type of blast furnace raw material." For example, if the iron raw material is one of the following: lump ore, sintered ore, pellets, or uncalcined carbon-containing agglomerated ore, the particle size of that iron raw material can be referred to as "information on particle size for each type of blast furnace raw material." Particle size can be expressed using the arithmetic mean particle diameter on a mass basis, but is not limited to this; the harmonic mean particle diameter on a mass basis can also be used (the same applies hereinafter). If two or more of the following are included: lump ore, sintered ore, pellets, and uncalcined carbon-containing lump ore, the particle size obtained for each of the two or more iron raw materials may be used as "information on particle size for each type of blast furnace raw material," or the particle size of the two or more iron raw materials (without being separated by brand) may be used as "information on particle size for each type of blast furnace raw material." If the ore dump contains small coke lumps, the particle size of the small coke lumps may also be included as "information on particle size for each type of blast furnace raw material." In a coke dump, the particle size of coke can be used as "information regarding particle size for each type of blast furnace raw material." If the ore dump contains auxiliary materials, the particle size of each type of auxiliary material may be used as "information on particle size for each type of blast furnace material," or the particle size of the auxiliary materials (not separated by type) may be used as "information on particle size for each type of blast furnace material." For example, if the auxiliary material is one of olivine or silica, the particle size of that auxiliary material can be used as "information on particle size for each type of blast furnace material." Also, if the auxiliary material contains both olivine and silica, the particle size obtained for each of the two types of auxiliary materials may be used as "information on particle size for each type of blast furnace material," or the particle size of the two types of auxiliary materials (not separated by type) may be used as "information on particle size for each type of blast furnace material."

[0025] (Information regarding the charging weight for each type of blast furnace raw material) In ore dumping, the charging weight for each type of iron raw material may be considered "information regarding the charging weight for each type of blast furnace raw material," or the charging weight of all iron raw materials may be considered "information regarding the charging weight for each type of blast furnace raw material." For example, if the iron raw material is one of the following: lump ore, sintered ore, pellets, or uncalcined carbon-containing agglomerate, the charging weight of that iron raw material can be considered "information regarding the charging weight for each type of blast furnace raw material." If two or more of the following are included: lump ore, sintered ore, pellets, or uncalcined carbon-containing agglomerate, the charging weight obtained for each of those two or more types of iron raw material may be considered "information regarding the charging weight for each type of blast furnace raw material," or the charging weight of all of those two or more types of iron raw materials may be considered "information regarding the charging weight for each type of blast furnace raw material." If the ore dump contains small coke lumps, the weight of the iron raw materials (either by brand or as a whole), the weight of the small coke lumps, and their weight ratios may be used as "information regarding the charging weight of each type of blast furnace raw material." In a coke dump, the weight of the coke charged can be used as "information regarding the weight of each type of blast furnace raw material charged." If the ore dump contains auxiliary materials, the charging weight for each type of auxiliary material may be used as "information on the charging weight for each type of blast furnace material," or the charging weight of auxiliary materials (not separated by type) may be used as "information on the charging weight for each type of blast furnace material." For example, if the auxiliary material is one of olivine or silica, the charging weight of that auxiliary material can be used as "information on the charging weight for each type of blast furnace material." Furthermore, if the auxiliary material contains both olivine and silica, the charging weight obtained for each of these two types of auxiliary materials may be used as "information on the charging weight for each type of blast furnace material," or the charging weight of these two types of auxiliary materials (not separated by type) may be used as "information on the charging weight for each type of blast furnace material."

[0026] When acquiring raw material information, it is necessary to sort the blast furnace raw materials collected by the sampling conveyor 6 by type. This sorting process can be carried out based on the color, shape, density, presence or absence of magnetism, etc. of the blast furnace raw materials. Furthermore, the sorting process can be carried out manually or using a predetermined sorting device. The sorting process for the particle size of the blast furnace raw materials can be carried out based on sieves with different mesh sizes.

[0027] Since the purpose of this invention is to charge blast furnace raw materials into the furnace during a blast-free period and obtain information from the raw materials, the "raw material information" to be obtained is not limited to the "information regarding particle size and charging weight" mentioned above. For example, the bulk density of the blast furnace raw materials affects the void distribution of the deposit layer in the furnace, so this can be included in the "raw material information" to be obtained. The bulk density of blast furnace raw materials can be calculated by dividing the weight of the blast furnace raw materials by the volume when the materials are filled. Therefore, for example, the bulk density of blast furnace raw materials can be calculated by placing the blast furnace raw materials collected by the sampling conveyor 6 into a container of known volume and measuring the weight of the contents.

[0028] When blast furnace raw materials are transported by the charging conveyor 2 or charged from the top charging device 3, segregation occurs in the blast furnace raw materials due to differences in particle size and density. As a result, the particle size distribution of the charged blast furnace raw materials changes over time, and the particle size distribution of the deposited blast furnace raw materials differs depending on the charging timing and charging location, which can lead to a discrepancy between the O / C distribution after deposition and the target O / C distribution.

[0029] In contrast to the conventional blast furnace raw material particle size distribution estimation method described in Patent Document 1, the estimation accuracy of the particle size distribution of the blast furnace raw materials being charged and the accuracy of raw material identification were insufficient. Therefore, it was not always easy to bring the void distribution of the in-furnace deposit layer closer to the correct value. This embodiment is a method in which blast furnace raw materials dropped in from the rotating chute 5 are directly collected and analyzed by the sampling conveyor 6. Therefore, accurate raw material information of the blast furnace raw materials can be obtained, and changes in the blast furnace raw materials over time can be understood.

[0030] By understanding the changes in blast furnace raw materials over time, it is possible to more accurately predict the distribution of charges in the radial direction and the void distribution of the in-furnace deposit layer. Based on these predictions, appropriate adjustment actions can be taken. The adjustment action can be determined using the temporal changes in blast furnace raw materials observed in S20, and a deposition shape estimation tool that can estimate the deposition shape inside the furnace according to the amount of blast furnace raw materials charged into the blast furnace. As a deposition shape estimation tool, for example, the tool described in "Iron and Steel, Vol. 73 (1987), No. 1, pp. 91-98" can be used.

[0031] For example, an adjustment action may involve changing at least one of the following: the tilt angle of the rotating chute, the number of rotations, the amount of iron raw material charged into the furnace, the charging order of blast furnace raw materials, or the conveying order by the charging conveyor. These adjustment actions may be performed automatically by a controller consisting of a CPU or the like, or by an operator operating from a control room.

[0032] By operating the blast furnace based on the adjustment actions described above, the void distribution of the in-furnace deposit can be brought closer to the ideal void distribution.

[0033] <Sampling process of blast furnace raw materials charged into the blast furnace> Figure 3 is a subroutine of Figure 2 that shows the contents of the sampling process (S10) in more detail. Referring to Figure 3, first, the sampling conveyor 6 is inserted into a predetermined position in the circumferential direction of the blast furnace 1 in the blast furnace in a non-blast state and rotated (S11). The predetermined position in the circumferential direction of the furnace is not particularly limited, but can be set to an appropriate position that makes it easy to insert the sampling conveyor 6, for example.

[0034] Next, the rotating chute 5 is rotated to charge the blast furnace material discharged from the top charging device 3 towards the furnace deposit surface (S12).

[0035] In S12, each time the rotating chute 5 reaches the insertion position (a predetermined position in the circumferential direction of the furnace) of the sampling conveyor 6, the blast furnace raw materials dropped in from the rotating chute 5 are loaded onto the sampling conveyor 6 and transported out of the furnace (S13).

[0036] The blast furnace material recovery operation in S13 is repeated, and once the recovery of blast furnace material in the final rotation is complete (S14 Yes), the rotating chute 5 is stopped and the charging of blast furnace material into the furnace is completed (S15). After that, the sampling conveyor 6 is stopped and moved to a waiting position outside the furnace (S16).

[0037] <Process for monitoring changes in blast furnace raw materials over time as they are charged into the blast furnace> Figure 4 shows a subroutine from Figure 2 that more specifically details the process for understanding changes over time (S20). In the subroutine in Figure 4, as an example, the particle size of sintered ore obtained in the ore dump and the weight ratio of small coke lumps and iron raw materials are used as "raw material information".

[0038] First, the blast furnace raw materials recovered in S13 of Figure 3 are separated into sintered ore and small coke lumps (S21). This separation process can be carried out by focusing on the color, shape, and density of the sintered ore and small coke lumps. Alternatively, the separation process may be carried out by attracting the sintered ore with a magnet.

[0039] The sintered ore sorted in S21 is sieved, and the particle size of the sintered ore is obtained based on the results (S22). Since sieving is a known technique, a detailed explanation is not required.

[0040] The weight of each of the sintered ore and small coke lumps sorted in S21 is measured to obtain information on the weight ratio of small coke lumps to iron raw materials (small coke lumps / iron raw materials) for each rotation (S23). Note that the weight ratio of small coke lumps to iron raw materials is not limited to the above calculation method; for example, if the iron raw materials include multiple brands, the weight of the small coke lumps may be divided by the total weight of each brand of iron raw material.

[0041] The grain size of the sintered ore obtained in S22 is obtained for each rotation to understand the change in grain size of the sintered ore over time (S24). The weight ratio of small coke lumps and iron raw materials obtained in S23 is plotted for each rotation to understand the change in the weight ratio over time (S24). In the embodiments described later, the change over time is understood using a graph, but the present invention is not limited to this, and may be understood in other forms such as tables.

[0042] (Examples) The present invention will be described in more detail with reference to examples. In this example, 5000m 3During the shutdown of the blast furnace, a sampling conveyor was inserted, and ore dumping (102 tons of iron raw materials (including sintered ore, pellets, and lump ore) and 4 tons of small coke lumps) was performed while a swivel chute, set to a predetermined tilt angle (50°), was rotated to obtain sampling and raw material information. The number of rotations of the swivel chute was set to 24. The sampling method for iron raw materials was explained with reference to Figures 2 and 3 in the above embodiment, so the explanation is omitted here. In addition, the particle size of sintered ore and the weight ratio of small coke lumps to iron raw materials were obtained as raw material information. The "particle size of sintered ore" was defined as Dn / Dave. Dn is the mass-based arithmetic mean particle size of sintered ore contained in the iron raw materials recovered by the sampling conveyor on the nth time, and the average value of Dn over the entire sampling is Dave (=ΣDn / 24). Note that Dave is not limited to the method of obtaining it from the average value of Dn, but may also be obtained from the mass-based arithmetic mean particle size of the entire sampled sintered ore. The "weight ratio of small coke lumps to iron raw materials" was calculated based on the time change in the charging weight ratio of iron raw materials and the time change in the charging weight ratio of small coke lumps.

[0043] Figure 5 shows the time variation of the Dn / Dave ratio of the sintered ore in this embodiment. The 24 plots shown in Figure 5 indicate the timing of the recovery of iron raw material by the sampling conveyor, and this is the same in Figures 6 to 8. The horizontal axis in Figure 5 represents dimensionless time normalized from 0 at the start of charging of iron raw material by the rotating chute to 1 at the completion of charging, and this is the same in Figures 6 to 8.

[0044] Figure 6 shows the time change in the charging weight ratio of small coke lumps in this embodiment. When Wn is the weight of small coke lumps contained in the iron raw material recovered by the sampling conveyor on the nth time, and Wa is the total weight of small coke lumps contained in all iron raw material recovered by the sampling conveyor, the vertical axis of Figure 6 shows Wn / Wa. In Figure 6, information regarding the charging weight of small coke lumps is represented in Wn / Wa.

[0045] Figure 7 shows the time change in the charging weight ratio of iron raw materials in this embodiment. When Sn is the weight of iron raw materials contained in the iron raw materials recovered by the sampling conveyor on the nth time, and Sb is the total weight of iron raw materials contained in all iron raw materials recovered by the sampling conveyor, the vertical axis of Figure 7 represents Sn / Sb. In Figure 7, information regarding the charging weight of iron raw materials is represented in terms of Sn / Sb.

[0046] Figure 8 shows the time change in the weight ratio of small coke lumps to iron raw materials, calculated based on Figures 6 and 7. The vertical axis of Figure 8 represents Wn / Sn, using the Wn and Sn values ​​described above. In Figure 8, information regarding the charging weights of small coke lumps and iron raw materials is expressed in Wn / Sn.

[0047] In this way, by sampling the iron raw material being charged in by gravity, we were able to directly understand the changes in sintered ore over time and the changes in the weight ratio of small coke lumps to iron raw material over time. [Explanation of Symbols]

[0048] 1 Blast furnace 5 Swivel chute 6 Sampling conveyor

Claims

1. A method for analyzing blast furnace raw materials charged into a bellless blast furnace to understand the changes in blast furnace raw materials over time, A sampling process in which a swirl chute is rotated while the blast furnace is shut down, and blast furnace material falling from the swirl chute toward the furnace deposit surface is collected at a predetermined position in the circumferential direction of the furnace and transported out of the furnace, A time-series change understanding step involves analyzing the blast furnace raw materials removed in the sampling step to obtain raw material information including information on particle size and charging weight for at least each type of blast furnace raw material, thereby understanding the changes in the blast furnace raw materials over time. A method for understanding the changes in blast furnace raw materials over time.

2. The aforementioned raw material information further includes the bulk density of the blast furnace raw materials. A method for determining changes in blast furnace raw materials over time, as described in claim 1, characterized in that it is a method for determining changes in blast furnace raw materials over time.

3. In the sampling process, The tilt angle of the aforementioned swivel chute is fixed to a predetermined value. A method for determining changes in blast furnace raw materials over time, as described in claim 1 or 2, characterized by the present invention.

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