Blast furnace operation method

Abstract

To provide a method for quantitatively evaluating a relation between reduction powdering and pressure loss in a furnace and a heat flow ratio.SOLUTION: A blast furnace operation method includes: a reduced powder amount estimation step of acquiring a reduced powder amount at each in-furnace position associated with a heat flow ratio for a plurality of heat flow ratios; a first relationship information acquisition step of acquiring first relationship information that is a relationship between a representative value of the reduced powder amount at each in-furnace position and the heat flow ratio; a second relationship information acquisition step of acquiring second relationship information that is a relationship between an in-furnace pressure loss and the heat flow ratio; and an adjustment step of adjusting the heat flow ratio based on the first relationship information and the second relationship information in order to achieve target conditions of the reduced powder and the pressure loss.SELECTED DRAWING: Figure 12

Description

Technical Field

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

Background Art

[0002] In the blast furnace process, raw materials are charged so that ore layers and coke layers are alternately formed in the furnace, and hot air is blown from the lower part of the furnace to simultaneously carry out a reduction and melting process to efficiently produce hot metal. An advantage of the blast furnace process is high thermal efficiency, and in order to maintain this thermal efficiency, ensuring the air permeability in the blast furnace (hereinafter also referred to as "furnace air permeability") is one of the important operating indicators. The reason why ensuring furnace air permeability is emphasized is that if the furnace air permeability is impaired, heat exchange is not sufficiently carried out, which has an adverse effect on the stable operation of the blast furnace.

[0003] As a factor causing deterioration of furnace air permeability, reduction pulverization of ore is known. Reduction pulverization causes a significant reduction in the particle size of ore, and since the voids between ores in the furnace become smaller, the furnace air permeability deteriorates. If the deterioration of furnace air permeability becomes serious, it causes problems with discharging and hanging up, and significantly impairs the material flow stability and heat conductivity inside the blast furnace. Regarding the mechanism of reduction pulverization, detailed investigations have been conducted to date (for example, see Non-Patent Document 1).

[0004] Conventionally, when there is concern about deterioration of air permeability due to reduction pulverization, measures against deterioration of air permeability have been taken by improving the quality of sintered ore, adjusting the layer thickness ratio of ore layers and coke layers, changing the distribution of charged materials, and the like.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] The deterioration of reduction degradation can be suppressed by reducing the heat flow ratio. The heat flow ratio can be reduced by increasing the blast volume (in other words, increasing the amount of bosch gas), but there is a risk that the pressure loss in the furnace will increase excessively. Conventionally, a method for quantitatively evaluating the relationship between reduction degradation, pressure loss in the furnace, and the heat flow ratio has not been established.

Means for Solving the Problems

[0007] In order to solve the above problems, the operation method of a blast furnace according to the present invention includes: (1) a reduction degradation amount estimation step of obtaining the reduction degradation amount for each furnace position associated with the heat flow ratio for a plurality of heat flow ratios; a first relationship information acquisition step of obtaining first relationship information that is the relationship between the representative value of the reduction degradation amount for each furnace position and the heat flow ratio; a second relationship information acquisition step of obtaining second relationship information that is the relationship between the pressure loss in the furnace and the heat flow ratio; and an adjustment step of adjusting the heat flow ratio based on the first relationship information and the second relationship information in order to achieve the target conditions for reduction degradation and pressure loss.

[0008] (2) The adjustment step is a step of adjusting the heat flow ratio by adjusting the blast conditions of the blast furnace, and the operation method of the blast furnace according to the above (1) is characterized in that.

[0009] (3) The representative value is the maximum value of the reduction degradation amount for each in-furnace position, and the operation method of the blast furnace according to (1) or (2) above is characterized by this.

[0010] (4) When the reduction degradation amount estimation step defines the weight ratio for each particle size interval of the iron raw material before reduction degradation as the pre-pulverization particle size distribution vector and the weight ratio for each particle size interval of the iron raw material after reduction degradation as the post-pulverization particle size distribution vector, based on the change amount of the magnetite amount (magnetite change amount) which is the change amount of the weight ratio of magnetite before and after reduction and the impact energy acting on the iron raw material, the reduction degradation index calculation step of obtaining the reduction degradation index for each in-furnace position, the pulverization matrix creation step of creating, for each in-furnace position, a pulverization matrix representing the degree of change in the weight ratio of the iron raw material due to reduction degradation for each predetermined particle size interval using the reduction degradation index and the Gaudin-Meloy distribution formula, the post-pulverization particle size distribution vector calculation step of obtaining the post-pulverization particle size distribution vector from the product of the pulverization matrix and the pre-pulverization particle size distribution vector matrix for each in-furnace position, and the reduction degradation amount calculation step of obtaining the reduction degradation amount for each in-furnace position based on the calculation result of the post-pulverization particle size distribution vector calculation step, and the operation method of the blast furnace according to (1) or (2) above is characterized by having these steps.

[0011] (5) The reduction degradation index calculation step is a step of obtaining the reduction degradation index by substituting the magnetite change amount and the impact energy for each in-furnace position into the following formula (A), and the operation method of the blast furnace according to (4) above is characterized by this.

Equation

[0012] (6) The matrix of the pulverized matrix created in the pulverized matrix creation step is expressed by the following matrix (B) using DEG ij (where the subscripts i and j are any integers from 1 to r, and r corresponds to the number of particle size intervals), and the operation method of the blast furnace according to (4) or (5) above is characterized in that. [Number] ···· Matrix (B) DEG where the subscripts i and j are the same as each other ij corresponds to the iron raw material that remains without shifting from particle size interval i after reduction pulverization, and DEG where the subscripts i and j are different from each other ij corresponds to the iron raw material that shifts from particle size interval i to particle size interval j after reduction pulverization.

[0013] (7) Each DEG ij (excluding DEG rr ) is obtained based on the Gaudin-Meloy distribution, and DEG rr is 1, and the operation method of the blast furnace according to (6) above is characterized in that.

[0014] (8) The DEG included in the same row ij has the initial particle size in the Gaudin-Meloy distribution set to the same value, and this initial particle size varies depending on the row and becomes smaller as the row number increases, and the operation method of the blast furnace according to (7) above is characterized in that. [Advantages of the Invention]

[0015] According to the present invention, since the relationship between reduction pulverization, in-furnace pressure loss, and heat flow ratio can be quantitatively grasped, by appropriately adjusting the heat flow ratio, the target conditions of reduction pulverization and in-furnace pressure loss can be achieved. [Brief Description of the Drawings]

[0016]

Figure 1

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Figure 13

Mode for Carrying Out the Invention

[0017] (Schematic Configuration of Blast Furnace) Figure 1 is a schematic diagram of a blast furnace. The blast furnace 1 is a bell-less blast furnace including a tuyere 2, an annular pipe 3, a blow pipe 4, a swivel chute 5, and a tapping spout 6. However, the present invention can also be applied to a bell blast furnace.

[0018] The tuyere 2 is an injection port for blowing hot air generated by a hot blast stove (not shown) from the lower part of the blast furnace 1, and a plurality of tuyeres are provided along the furnace circumferential direction of the blast furnace 1.

[0019] The annular pipe 3 is arranged so as to surround the lower part of the blast furnace 1. A plurality of blow pipes 4 are intermittently provided in the circumferential direction on the annular pipe 3. The annular pipe 3 supplies the hot air sent from the hot blast stove to the blow pipes 4.

[0020] Each blow pipe 4 is connected to the annular pipe 3 and is respectively connected to different tuyeres 2. The blow pipe 4 blows the hot air flowing in from the annular pipe 3 into the blast furnace 1 through the tuyere 2.

[0021] The revolving chute 5 charges iron raw materials and coke into the furnace while rotating around an axis extending in the vertical direction. An ore layer 11 and a coke layer 12 are alternately formed in the furnace by the iron raw materials and coke charged from the revolving chute 5. As the iron raw materials, lump ore, sintered ore, pellets, non-fired carbon-containing lump ore, etc. can be used. Further, the iron raw materials may contain a reduction aid such as small lump coke. The coke may be ferro-coke. The coke functions as a reducing agent for reducing the iron raw materials and a fuel for melting the iron raw materials. By controlling the tilt angle and rotation speed of the revolving chute 5, the blast furnace raw materials can be charged to a desired position.

[0022] The taphole 6 is provided at the bottom of the furnace of the blast furnace 1 and taps the hot metal produced by the reduction of the iron raw materials. A plurality of tapholes 6 are provided along the furnace circumferential direction, and the hot metal can be tapped continuously or intermittently.

[0023] The operation method of the blast furnace according to this embodiment includes a reduction pulverization amount estimation step, a first relationship information acquisition step, a second relationship information acquisition step, and an adjustment step. Hereinafter, each step will be described in detail.

[0024] (Regarding the reduction pulverization amount estimation step, the first relationship information acquisition step, and the second relationship information acquisition step) The reduction pulverization amount estimation step is "a step of acquiring the reduction pulverization amount for each furnace position associated with the heat flow ratio for a plurality of heat flow ratios", and is realized, for example, by an analysis process using a blast furnace mathematical model. The blast furnace mathematical model (see, for example, Non-Patent Document 2) is a mathematical model that divides the internal region of the blast furnace into a mesh shape, substitutes preset conditions into arithmetic expressions such as material balance, momentum balance, and energy balance, performs arithmetic processing, estimates state variables, and comprehensively simulates the furnace internal state. Note that the blast furnace mathematical model described below refers to the blast furnace mathematical model of Non-Patent Document 2 unless otherwise specified.

[0025] The simulation by the blast furnace mathematical model is realized by the cooperation of a computer device and software. As the computer device, a general computer device such as an arithmetic device such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), a main storage device such as a RAM (Random Access Memory), an auxiliary storage device such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), or a flash memory, or a server device can be used. Software refers to a program that causes the arithmetic device to execute the arithmetic processing described below.

[0026] First, using the blast furnace mathematical model, the state variables in the reference operation are estimated. The reference operation is preferably the operation during the operation stable period. The operation stable period means a period in which the blast furnace operation is stable without blowing-off immediately before and after, sudden increase in burden, or large change in blowing conditions. The "set conditions" include blowing conditions such as the blowing rate, oxygen enrichment amount, and oxygen enrichment rate, raw material properties (including the amount of magnetite in the iron raw material before reduction, etc.), and the impact energy for each position in the furnace. The impact energy is the stress received by the iron raw material in the furnace and can be calculated, for example, based on a known rigid-plastic model (see Non-Patent Document 3). The set conditions can be stored in the storage unit in advance. The "state variables" include the amount of milled iron ore, molten iron temperature, heat flow ratio, reducing agent ratio (RAR), coke ratio (CR), pulverized coal ratio (PCR), theoretical combustion temperature (Tf) at the tuyere tip, top gas temperature, in-furnace pressure loss, amount of magnetite after reduction at each in-furnace position, gas temperature at each in-furnace position, and amount of reduction degradation at each in-furnace position. The estimated state variables can be stored in the storage unit.

[0027] What is new and important in this analysis process is that the amount of reduction degradation at each in-furnace position is estimated as a state variable. The amount of reduction degradation at each in-furnace position can be estimated by (1) the reduction degradation index calculation step, (2) the degradation matrix creation step, (3) the particle size distribution vector calculation step after degradation, and (4) the reduction degradation amount calculation step. The following will be described separately for each step.

[0028] (1) Reduction degradation index calculation step The arithmetic processing unit calculates the change amount of magnetite at each in-furnace position from the difference between the amount of magnetite in the iron raw material before reduction and the amount of magnetite at each in-furnace position after reduction, and substitutes the calculated change amount of magnetite at each in-furnace position and the impact energy at each in-furnace position stored in the storage unit as a set condition into the following formula (1) to obtain the reduction degradation index n(de, d(△Fe 3 O 4 )) at each in-furnace position.

Equation

[0029] Equation (1) is assumed to be pre-stored in the storage unit. The technical significance of Equation (1) will be explained in detail. Reduction pulverization is affected by the amount of magnetite change (hereinafter also referred to as "△Fe 3 O 4 ") and the impact energy. The amount of magnetite change is the change in the weight ratio of magnetite before and after reduction. That is, the difference between the weight ratio of magnetite contained in the iron raw material before reduction and the weight ratio of magnetite contained in the iron raw material after reduction corresponds to the amount of magnetite change. Note that the weight ratio may be expressed as a percentage or as a ratio with the whole being 1. The impact energy is the stress that the iron raw material receives in the furnace. These amount of magnetite change and impact energy vary depending on the furnace position.

[0030] Equation (1) is obtained by taking the total differential of a multiplication formula obtained by multiplying the reduction pulverization index n 1 corresponding to the impact energy and the reduction pulverization index n 2 corresponding to the amount of magnetite change of the iron raw material.

[0031] (Regarding the reduction pulverization index n 1 ) The reduction pulverization index n 1 can be derived by the following step 1. In step 1, a rotational impact process that applies rotational impact to the iron raw material reduced under predetermined reduction conditions is performed multiple times. In each rotational impact process, by obtaining the one-to-one relationship between the impact energy and the reduction pulverization index, the relationship information of the impact energy and the reduction pulverization index n 1 is obtained. The predetermined reduction conditions may be those that simulate the reduction conditions in the furnace. For example, the gas composition may be "20 vol% CO - 10 vol% H 2 - 70 vol% N 2 ", and a reduction process according to the pattern of FIG. 5 described later may be used. Note that, unlike step 2 described later, the reduction conditions in step 1 are set to one.

[0032] The impact energy applied to the iron raw material in the furnace can be reproduced by the impact energy corresponding to the number of rotations in the drum strength tester used when measuring the RDI of iron ore. Figure 2 is a conceptual diagram of the particle motion in the drum tester. The impact energy is the impact energy when the iron raw material O in the drum 21 freely falls along the falling trajectory FT. The impact energy (in other words, the falling impact energy of the iron raw material) can be obtained from the following formulas (2) to (6).

Number

[0033] The radius r of the drum in the drum tester is design information, and the angular velocity ω is an operating condition, both of which are known values. For example, the angular velocity ω can be set to the angular velocity corresponding to a rotational speed of 30 (rpm). Also, the angle θ is a known value based on past findings and the like.

[0034] Figure 3 is a conceptual diagram of a drum tester showing the rotational state of the drum. The drum 21 is formed in a cylindrical shape, and a pair of lifters 22 are provided on the inner surface of the drum 21 at positions facing each other across the central axis L of the drum 21. These lifters 22 rotate together with the drum 21 and lift the iron raw material O. When the angle θ of the lifter 22 with respect to the X-axis reaches a predetermined value, the iron raw material slides off the lifter 22. When the drum 21 makes one revolution, the number of impacts received by the iron raw material is 2 times. By comparing the area of the lifter 22 with the approximate area of the projection circle of the sintered ore, the weight ratio of the iron raw material lifted by the lifter 22 can be grasped.

[0035] Based on the above information, the impact energy received by the iron raw material can be calculated according to the rotational speed. For example, when 500 g of sintered ore is charged into the drum 21 equipped with the lifter 22 of a predetermined size (length: 200 mm, width: 20 mm), the weight ratio of the sintered ore lifted by the lifter 22 is 33%. In this case, the impact energy e when the drum 21 makes 120 revolutions is estimated to be 0.78 (J / piece).

[0036] As described above, the rotational impact process is carried out multiple times, and the one-to-one information of the impact energy and the reduction degradation index is obtained by the following method each time. The iron raw material subjected to rotational impact is taken out from the drum 21, and the particle size distribution (measured particle size distribution) is measured. Then, by fitting the Gaudin-Meloy distribution formula to this measured particle size distribution, the reduction degradation index is obtained. Thereby, the one-to-one information of the impact energy and the reduction degradation index is obtained. The following formula (7) is the general formula of the Gaudin-Meloy distribution formula.

Equation

[0037] The Gaudin-Meloy distribution formula is a particle size distribution estimation formula derived based on the random probability theory of being crushed into any particle size x, and is a distribution formula suitable for considering the "randomness of cracks generated in the iron raw material". According to the Gaudin-Meloy distribution formula, it can more appropriately represent the particle size distribution of the iron raw material with reduction degradation than the Gaudin-Schumann distribution formula and the Broadbent-Callcott distribution formula.

[0038] After measuring the particle size distribution, the iron raw material is returned to the drum 21, and the drum 21 is rotated again. When the rotation speed reaches a predetermined value, the iron raw material is taken out from the drum 21 again, the measured particle size distribution is obtained, and the reduction degradation index is obtained by performing parameter fitting of the Gaudin-Meloy distribution formula to this measured particle size distribution. Thereby, one-to-one information on the impact energy and the reduction degradation index is further obtained.

[0039] By repeating these steps (applying rotational impact, calculating the impact energy, measuring the measured particle size distribution, calculating the reduction degradation index), one-to-one information on the impact energy and the reduction degradation index is obtained as many times as the number of rotational impact steps, and the relationship between the impact energy and the reduction degradation index n 1 is obtained. The relationship between the impact energy and the reduction degradation index n 1 is defined by the general formula as follows.

Equation

[0040] Figure 4 shows the impact energy and the reduction degradation index n 1It is a graph schematically showing the relationship information, where the horizontal axis is the impact energy (J / particle) and the vertical axis is the reduction pulverization index (-). In the illustrated example, the impact energy applied in each rotary impact process is 0.195 (J / particle), 0.39 (J / particle), 0.78 (J / particle), 1.56 (J / particle), 3.12 (J / particle), 5.85 (J / particle), and the corresponding reduction pulverization index (-) is 0.56 (-), 0.86 (-), 1.09 (-), 1.37 (-), 1.74 (-), 2.21 (-). Based on this information, the relationship between the impact energy and the reduction pulverization index n 1 When organizing the relationship with, the following formula (9) is obtained. [Number] It can be seen that the slope of formula (9) is large at the initial stage of applying the impact energy and becomes approximately linear when it exceeds 2.0 (J / particle). Regarding the reason, the inventor of the present invention thinks as follows. Large-sized iron raw materials with low mechanical strength undergo volume fracture and crack at the initial stage of rotation, causing the reduction pulverization index to rise rapidly. After that, small-sized iron raw materials are subjected to friction and other factors, and surface fracture gradually progresses.

[0041] (Regarding the reduction pulverization index n 2 ) The reduction pulverization index n 2 can be derived by the following step 2. In step 2, the weight ratio of magnetite contained in the iron raw material is obtained in advance, and then a reduction process of reducing the iron raw material under different reduction conditions is carried out. After each reduction process, the weight ratio of magnetite contained in the iron raw material is obtained, and by applying rotary impact to the iron raw material reduced in each reduction process, a one-to-one relationship between the magnetite change amount and the reduction pulverization index is obtained, and the relationship information between the magnetite change amount and the reduction pulverization index n 2 is obtained.

[0042] Figure 5 is a graph schematically showing the reduction pattern applied in the reduction process, where the horizontal axis is time (min) and the vertical axis is temperature (°C). Step S1 is N 2In an atmosphere, it is a heating step of heating the iron raw material from room temperature to the reaction temperature at a heating rate of 10 (°C / min). Step S2 is N 2 In an atmosphere, it is a heat preservation step of maintaining the temperature at the reaction temperature for 30 minutes. Step S3 is a reduction step of reducing for 30 (min) at the reaction temperature ±10 °C in an atmosphere of a reducing gas (a mixed gas of CO and H 2 . Step S4 is a cooling step of switching the atmosphere gas from the reducing gas to N 2 gas and reducing the temperature in the furnace to room temperature in an N 2 atmosphere.

[0043] By changing the time of the reduction process, the reduction temperature in the reduction step S3, and the gas composition of the reducing gas, the reduction conditions can be changed. Here, it is desirable to change the reduction conditions so that the reduction rate of the iron raw material obtained by the reduction test is included in the range of 1.2% or more and 19% or less. The "reduction rate" can be derived from the following formula.

Number

Number

Number

[0044] After carrying out the reduction test, determine the weight ratio of magnetite contained in the iron raw material, and determine the change amount of magnetite before and after reduction.

[0045] After determining the weight ratio of magnetite contained in the iron raw material after reduction, a rotary impact process is carried out to obtain the particle size distribution (measured particle size distribution) of the iron raw material after pulverization. Then, by performing parameter fitting of the Gaudin-Meloy distribution formula to this measured particle size distribution, the reduction pulverization index is obtained. As a result, one-to-one information on the magnetite change amount and the reduction pulverization index is obtained. By repeating this process while changing the reduction conditions, one-to-one information on the magnetite change amount and the reduction pulverization index can be obtained for the number of reduction steps, and the relationship information between the magnetite change amount and the reduction pulverization index n 2 can be obtained. The relationship between the magnetite change amount and the reduction pulverization index n 2 When defined by a general formula, it is as follows.

Equation

[0046] While showing specific examples, the method for obtaining the relationship information between the magnetite change amount and the reduction pulverization index n 2 will be described in more detail. Table 1 shows examples of reduction conditions. Note that the test time in Table 1 means the time from the start of the temperature increase step S1 to the end of the temperature decrease step S4.

Table 1

[0047] For each of these samples 1 to 52, one-to-one information on the magnetite change amount and the reduction pulverization index is obtained by the method described above. By plotting this information on the scatter diagram of Fig. 6 and performing parameter fitting to a quadratic function, the reduction pulverization index n 2The following formula (11) is obtained. Similar to Step 1, the rotational impact step was carried out using a drum strength tester. However, the rotational speed of the drum 21 was fixed at 120 rotations.

Number

[0048] As described above, the reduction pulverization index n corresponding to the impact energy of formula (8) 1 and the reduction pulverization index n corresponding to the change amount of magnetite of formula (10) 2 are multiplied to obtain the following formula (12). However, when multiplying the reduction pulverization index n 1 and the reduction pulverization index n 2 , it is necessary to align the standards, so the reduction pulverization index n 2 is divided by the constant β. The constant β is obtained by comparing the scatter diagrams in FIGS. 4 and 6, and when the reduction conditions are the same and the reduction pulverization indices n 1 and n 2 are the same, the reduction pulverization index n 1 (or n 2 ) can be used.

Number

[0049] Using formulas (9) and (11) with the constants made clear, when constructing a formula corresponding to formula (12), the following formula (13) is obtained.

Number

[0050] Finally, by taking the total differential of formula (12), the reduction pulverization index n (de, d(ΔFe 3 O 4A general formula for obtaining

Number

[0051] More specifically, by taking the total differential of Equation (13), a general formula for obtaining the reduction degradation index n(de, d(ΔFe 3 O 4 )) at each furnace position is obtained. That is, the constants in Equation (1) are set as x 1 = 0.44275, y 1 = -0.615, x 2 = 1.15, y 2 = 0.385, α 1 = 0.0005, α 2 = 0.0191, α 3 = 0.001, β = 1.09, and the resulting equation is the general formula for obtaining the reduction degradation index n(de, d(ΔFe 3 O 4 )) at each furnace position. Since these constants vary depending on the conditions of Step 1 and Step 2, the constants described here are only examples. Note that even if the constants change, the impact on the estimation accuracy of the reduction degradation index n is small.

[0052] Then, by substituting the impact energy and the change in magnetite amount at each furnace position into the equation obtained by taking the total differential of Equation (13) as described above, the reduction degradation index n(de, d(ΔFe 3 O 4 )) at each furnace position can be obtained.

[0053] After obtaining the reduction degradation index n(de, d(ΔFe 3 O 4 )) at each furnace position, proceed to the following pulverization matrix creation step. (2) Pulverization matrix creation step Gaudin-Meloy distribution formula and reduction degradation index n(de, d(ΔFe 3 O 4Using ( )), a pulverization matrix is created that represents the degree of change in the weight ratio of the iron raw material due to reduction pulverization for each particle size interval. Regarding the Gaudin-Meloy distribution, the explanation will not be repeated.

[0054] When the pulverization matrix component constituting the pulverization matrix is defined as DEG(x i ,x j ), the pulverization matrix component DEG(x i ,x j ) can be expressed by the following equation using the Gaudin-Meloy distribution.

Equation

[0055] x j is any arbitrary particle size of interest. M (x) is the cumulative particle size ratio at the particle size x, corresponding to the "Gaudin-Meloy distribution". x i is the initial particle size (mm), and n i is the reduction pulverization index derived in Step 3 above. Note that the reduction pulverization index n i varies depending on the initial particle size x i , so the subscript is appended with "i".

[0056] The pulverization matrix component DEG(x i ,x j ) will be described in detail with reference to FIG. 7. FIG. 7 is a graph for explaining the concept of the pulverization matrix component, where the horizontal axis is the particle size (mm) and the vertical axis is the cumulative undersize ratio. By substituting the initial particle size x i and the reduction pulverization index n i into the Gaudin-Meloy distribution, a distribution curve based on the Gaudin-Meloy distribution can be drawn. By arbitrarily defining the particle size interval of x j ~x j+1 , the pulverization matrix component DEG(x i ,x j ) can be obtained. That is, the initial particle size xi When the iron raw material is reduced and pulverized, the particle size is x j The weight ratio of the iron raw material below is M ( x j) becomes, and the particle size is x j+1 The weight ratio of the iron raw material below is M ( x j+1) becomes. Therefore, the weight ratio of the iron raw material belonging to the particle size range x j ~x j+1 is M ( x j) from M ( x j+1) is calculated by subtracting, and this corresponds to the pulverization matrix component DEG in the particle size range x j ~x j+1 . The pulverization matrix component DEG (x i , x j ) is obtained, and the matrix representation of these is the pulverization matrix. Here, it is desirable to make the particle size range with the smallest particle size (hereinafter also referred to as the minimum particle size range) correspond to the particle size of the reduced and pulverized iron raw material. Since various reports have been made on the particle size of the reduced and pulverized iron raw material in the range of 2 mm or more and 8 mm or less, it may be appropriately set within this range. That is, the minimum particle size range can be 0 to k mm (where k is 2 or more and 8 or less). There is no particular limitation on the particle size range above the minimum particle size range.

[0057] (3) Step of calculating the particle size distribution vector after pulverization Define the weight ratio for each particle size range of the iron raw material before reduction and pulverization as the particle size distribution vector f before pulverization. Define the weight ratio for each particle size range of the iron raw material after reduction and pulverization as the particle size distribution vector g after pulverization. At this time, the particle size distribution vector g after pulverization is the product of the pulverization matrix D and the matrix of the particle size distribution vector f before pulverization, and when expressed by an equation, it is as follows. [Number] ···· Equation (15) DEG ij is the particle size range x related to the i-th column of the matrix j ~xj+1 is the pulverized matrix component. f j is the particle size range x of the iron raw material before reduction pulverization j ~x j+1 is the particle size distribution vector corresponding to it. g j is the particle size range x of the iron raw material after reduction pulverization j ~x j+1 is the particle size distribution vector corresponding to it. Since the particle size distribution vector represents the weight ratio of the iron raw material contained in each particle size range by a matrix, the integrated value of the particle size distribution vectors f 1 ~f r is 100 (mass%), and the integrated value of the particle size distribution vectors g 1 ~g r is also 100 (mass%). In these particle size distribution vectors, the minimum particle size is 0 (mm).

[0058] The technical significance of this determinant will be described in detail. g 1 ~g r and f 1 ~f r The subscripts of are corresponding to the particle size ranges, and the smaller the number, the larger the particle size range. That is, g 1 and f 1 correspond to the largest particle size range. For the convenience of explanation, the particle size ranges corresponding to g 1 ~g r (f 1 ~f r ) are defined as particle size ranges 1 to particle size range r, respectively. For example, focusing on the largest particle size range 1, the balance of the iron raw material belonging to the particle size range 1 due to reduction pulverization is only a decrease. That is, considering only the iron raw material remaining in the particle size range 1 due to reduction pulverization (in other words, there is no need to consider the iron raw material shifted from other particle size ranges). Therefore, since the pulverized matrix component in the first row becomes 0 except for the first column, the pulverized particle size distribution vector g of the particle size range 1 1 (mass%) can be expressed by the following formula (16). g 1 =DEG 11 ×f1 ····Formula (16) That is, "DEG" in Formula (16) 11 can be said to be the pulverization matrix component corresponding to particle size range 1, which represents the degree of change in the weight ratio of the iron raw material due to reduction pulverization.

[0059] Also, focusing on particle size range 2, which is the second largest in particle size, the balance of the iron raw material due to reduction pulverization is the increase shifted from particle size range 1 to particle size range 2 and the decrease shifted from particle size range 2 to particle size ranges 3 to r. Since there is no iron raw material shifted from particle size ranges 3 to r to particle size range 2, the pulverization matrix component in the second row needs to be 0 except for the first and second columns. Therefore, the particle size distribution vector g 2 (mass%) of particle size range 2 can be expressed by the following Formula (17). g 2 =DEG 12 ·f 1 +DEG 22 ·f 2 ····Formula (17) "DEG 12 ·f 1 " corresponds to the iron raw material shifted from particle size range 1 to particle size range 2 due to reduction pulverization, and "DEG 22 ·f 2 " corresponds to the iron raw material remaining in particle size range 2 without shifting to particle size ranges 3 to r. "DEG 12 " and "DEG 22 " in Formula (17) can be said to be the pulverization matrix components corresponding to particle size range 2, which represent the degree of change in the weight ratio of the iron raw material due to reduction pulverization.

[0060] Similarly, the particle size distribution vector g 3 (mass%) of particle size range 3, which is the third largest in particle size, can be expressed by the following Formula (18). g 3 =DEG 13 ·f 1 +DEG 23 ·f 2 +DEG 33 ·f 3 ····Formula (18) "DEG13 ·f 1 」 corresponds to the iron raw material that has shifted from particle size range 1 to particle size range 3 due to reduction degradation, and 「DEG 23 ·f 2 」 corresponds to the iron raw material that has shifted from particle size range 2 to particle size range 3 due to reduction degradation, and 「DEG 33 ·f 3 」 corresponds to the iron raw material that has remained in particle size range 3 without shifting to particle size ranges 4~r. 「DEG 13 」, 「DEG 23 」 and 「DEG 33 」 in formula (18) can be said to be the pulverization matrix components corresponding to particle size range 3, representing the degree of change in the weight ratio of the iron raw material due to reduction degradation. For particle size ranges 4~r, the pulverization matrix components can be obtained in the same way.

[0061] Note that DEGrr is the pulverization matrix component in the smallest particle size range x r ~0 (mm), and since the particle size does not become smaller than the particle size range x r ~0 (mm), DEGrr will always be 1.

[0062] The method for obtaining the pulverization matrix will be described in more detail with reference to FIG. 8. FIG. 8 is a graph corresponding to FIG. 7. However, for the sake of simplicity, the particle size ranges are divided into three sections, and the reduction degradation index n is set to 1. The particle size range 1 is 20~10 (mm), the particle size range 2 is 10~3 (mm), and the particle size range 3 is 3~0 (mm). Furthermore, let the cumulative undersize ratio corresponding to a particle size of 20 (mm) be c, the cumulative undersize ratio corresponding to a particle size of 10 (mm) be b, and the cumulative undersize ratio corresponding to a particle size of 3 (mm) be a.

[0063] Each DEG can be obtained as follows based on the Gaudin-Meloy distribution formula. DEG 11 =c - b DEG 12 =b - a DEG 13 =a - 0 = a In the Gaudin - Meloy distribution formula (7), the initial particle size X 0 and the particle sizes X are substituted with 20 (mm) and 20 (mm), respectively, so that the undersize cumulative ratio c can be obtained. In the Gaudin - Meloy distribution formula (7), the initial particle size X 0 and the particle sizes X are substituted with 20 (mm) and 10 (mm), respectively, so that the undersize cumulative ratio b can be obtained. In the Gaudin - Meloy distribution formula (7), the initial particle size X 0 and the particle sizes X are substituted with 20 (mm) and 3 (mm), respectively, so that the undersize cumulative ratio a can be obtained. As described above, DEG 11 corresponds to the iron raw material remaining in particle size interval 1, and DEG 12 , DEG 13 corresponds to the iron raw material shifted from particle size interval 1. Since both are DEG based on particle size interval 1, the maximum particle size of particle size interval 1, which is 20 (mm), is used as the initial particle size X 0 . Note that other particle sizes included in particle size interval 1 (for example, the average particle size of particle size interval 1) may be used as the initial particle size X 0 .

[0064] DEG 22 =b - a DEG 23 =a - 0 = a In the Gaudin - Meloy distribution formula (7), the initial particle size X 0 and the particle sizes X are substituted with 10 (mm) and 10 (mm), respectively, so that the undersize cumulative ratio b can be obtained. In the Gaudin - Meloy distribution formula (7), the initial particle size X 0 and the particle sizes X are substituted with 10 (mm) and 3 (mm), respectively, so that the undersize cumulative ratio a can be obtained. DEG 11 , DEG 12 , DEG 13 When calculating DEG 0 , the initial particle size X 11 , DEG 12 , DEG 13It is different. As described above, DEG 22 corresponds to the iron raw material remaining in particle size range 2, and DEG 23 corresponds to the iron raw material shifting from particle size range 2. Since both are DEGs based on particle size range 2, 10 (mm), which is the maximum particle size of particle size range 2, is taken as the initial particle size X 0 In addition, other particle sizes included in particle size range 2 (for example, the average particle size of particle size range 2) may be taken as the initial particle size X 0 as well.

[0065] DEG 33 is 1, so there is no need to calculate.

[0066] By the above calculations, each DEG constituting the pulverization matrix D can be obtained. Then, by calculating the matrix product of this pulverization matrix D and the pre-pulverization particle size distribution vector f, the post-pulverization particle size distribution vector g can be obtained. The pre-pulverization particle size distribution vector f can be obtained by preliminarily classifying the iron raw material before reduction pulverization with a sieve. In this embodiment, it is assumed that the pre-pulverization particle size distribution vector f is stored in the storage unit.

[0067] The above-mentioned "reduction pulverization index calculation step", "pulverization matrix creation step", and "post-pulverization particle size distribution vector calculation step" are implemented for each furnace position. By these, the particle size distribution after reduction pulverization (that is, the post-pulverization particle size distribution vector g) can be grasped for each furnace position.

[0068] (4) Reduction pulverization amount calculation step Based on the calculation results of the pulverization particle size distribution vector calculation step, the reduction pulverization amount is determined for each position in the furnace. Here, the reduction pulverization amount refers to the proportion of the powder amount of the iron raw material generated by the reduction pulverization of the iron raw material in the furnace (in other words, the weight proportion of the iron raw material with a low particle size). As described above, regarding the numerical value of "low particle size" regarded as reduction pulverization, various reports have been made in the range of 2 mm or more and 8 mm or less. Therefore, an appropriate particle size can be selected from such a range, and the weight proportion of the iron raw material below the selected particle size can be taken as the reduction pulverization amount. For example, when the pulverization particle size distribution vector is defined by the weight proportion of the iron raw material included in the particle size section 1 of 20 to 10 mm, the weight proportion of the iron raw material included in the particle size section 2 of 10 to 3 mm, and the weight proportion of the iron raw material included in the particle size section 3 of 3 to 0 mm, the weight proportion of the iron raw material in the particle size section 3 can be taken as the "reduction pulverization amount".

[0069] As described above, since the heat flow ratio is calculated as a state variable during the analysis by the blast furnace mathematical model, it is possible to obtain the "reduction pulverization amount for each furnace position associated with the heat flow ratio" regarding the reference operation. Note that the heat flow ratio is defined as the heat capacity of the raw material descending per unit time as B (kJ / kg·m 2 ·h), and the heat capacity of the furnace gas rising per unit time is G (kJ / kg·m 2 ·h), and the numerical value represented by B / G.

[0070] The arithmetic processing unit extracts the maximum value (corresponding to the representative value) from the reduction pulverization amounts for each furnace position in the reference operation, and obtains the "one-to-one information between the heat flow ratio and the maximum value of the reduction pulverization amount" regarding the reference operation. However, the representative value is not limited to the maximum value of the reduction pulverization amount. For example, the furnace positions in the upper X percent (for example, 20%) with a high reduction pulverization amount can be specified, and the average value or median value of the reduction pulverization amounts of these furnace positions can be used as the representative value.

[0071] As described above, since the heat flow ratio and the in-furnace pressure loss are calculated as state variables during the analysis using the blast furnace mathematical model, the arithmetic processing unit can acquire "one-to-one information between the heat flow ratio and the in-furnace pressure loss" regarding the reference operation.

[0072] Next, for another operating condition where the reference operation, the amount of hot metal tapped, the hot metal temperature, and the reducing agent ratio (RAR) are the same, and the heat flow ratio is different, various element calculations are performed using the blast furnace mathematical model. "The same amount of hot metal tapped" includes substantially the same. For example, if the difference in the amount of hot metal tapped from the reference operation is about ±100 (t / d), it can be considered that "the amount of hot metal tapped is the same". Also, "the same hot metal temperature" includes substantially the same. For example, if the difference in the hot metal temperature from the reference operation is about ±2 °C, it can be considered that "the hot metal temperature is the same". "The same reducing agent ratio (RAR)" includes substantially the same. For example, if the difference in the reducing agent ratio (RAR) from the reference operation is about ±2 (t / d), it can be considered that "the reducing agent ratio (RAR) is the same". The same range can be appropriately set by adjusting the parameters of the blast furnace mathematical model.

[0073] Here, in this embodiment, the process of adjusting the heat flow ratio is simulated by changing the blowing parameters (blowing rate, oxygen enrichment amount) from the reference operation. That is, without changing the reducing agent ratio (RAR), the thickness ratio of the ore layer and the coke layer (O / C), the raw material conditions, etc. from the reference operation, the process of changing the heat flow ratio is implemented by adjusting only the blowing parameters (blowing rate, oxygen enrichment amount). The process of searching for these different parameters is performed for a plurality of heat flow ratios. Therefore, for each heat flow ratio, "one-to-one information between the heat flow ratio and the maximum value of the reduction degradation amount" and "one-to-one information between the heat flow ratio and the in-furnace pressure loss" can be obtained.

[0074] As a result, since the one-to-one information between the heat flow ratio and the maximum value of the reduction degradation amount is obtained as many as the number of heat flow ratios searched, "the first relationship information that is the relationship between the maximum value of the reduction degradation amount for each in-furnace position and the heat flow ratio" can be acquired. In addition, since one-to-one information on the heat flow ratio and the in-furnace pressure loss can be obtained in the same number as the number of heat flow ratios explored, "second relationship information that is the relationship between the in-furnace pressure loss and the heat flow ratio" can be acquired. Specific examples of the first relationship information and the second relationship information will be shown in the examples described later.

[0075] (Adjustment step) Based on the first relationship information and the second relationship information, by adjusting the heat flow ratio, reduction degradation and pressure loss are brought within the target conditions. The heat flow ratio can be changed by adjusting the blowing conditions (blowing volume, oxygen enrichment amount). Here, there is a trade-off relationship between the maximum value of the reduction degradation amount and the in-furnace pressure loss. When the heat flow ratio is increased (decreased), the reduction degradation deteriorates (improves) and the in-furnace pressure loss improves (deteriorates). This point will be clarified in the examples described later.

[0076] The target conditions vary depending on factors such as the scale of the blast furnace and are not limited. The heat flow ratio should be appropriately determined from the coke ratio (CR) and production volume in the current blast furnace operation and is not fixed. However, from the perspective of avoiding significant occurrence of reduction degradation, by implementing an adjustment action to reduce the heat flow ratio in anticipation of an increase in the reduction degradability (RDI) of the raw materials, the amount of generated powder can be reduced. On the other hand, when the blowing volume is increased to reduce the heat flow ratio, the in-furnace pressure loss deteriorates accordingly. That is, when set to a low heat flow ratio to reduce reduction degradation, the in-furnace pressure loss increases due to an increase in the gas volume, and when set to a high heat flow ratio to reduce the in-furnace pressure loss, the reduction degradation amount increases. According to the present embodiment, since the relationship between the heat flow ratio and the reduction degradation amount and the relationship between the heat flow ratio and the in-furnace pressure loss can be quantitatively grasped, by using the heat flow ratio as an adjustment means, the maximum value of the reduction degradation amount and the in-furnace pressure loss can be easily brought within the target conditions.

[0077] (Examples) The present invention will be described in detail with reference to examples. It is considered that the reduction degradation is aggravated by the remaining un-reduced magnetite up to the lower part of the shaft with high impact energy. Therefore, as one of the methods to suppress the reduction degradation, it is conceivable to operate at a low heat flow ratio. By operating at a low heat flow ratio, the temperature rise of the iron raw materials charged into the blast furnace proceeds rapidly. It is considered that the amount of reduction degradation will be reduced if most of the magnetite can be reduced to wustite and iron by the time it reaches the lower part of the shaft. Therefore, according to the description of the above embodiment, an operation analysis was performed using a blast furnace mathematical model for the case where the blowing conditions (blowing volume, oxygen enrichment amount) were changed to control the heat flow ratio. Table 2 shows the analysis results. The operations with the heat flow ratio changed with respect to the reference operation were defined as modified operations 1 to 4 respectively. In addition, the weight of the iron raw materials before reduction was set to 1, and the magnetite amount of the iron raw materials before reduction was set to 0.1913 (-). Further, the furnace interior region was divided into a mesh shape, and the change amount of magnetite and the impact energy were obtained for each as the furnace interior position (analysis unit). When the dimensionless radius of the blast furnace was 1 and the dimensionless furnace height was 1, the size of each mesh was 0.1 in the furnace diameter direction and 0.025 in the furnace height direction.

Table 2

[0078] The gas temperature, the change amount of magnetite, and the amount of reduction degradation for each furnace interior position under each operation condition are shown in FIGS. 9, 10, and 11 respectively. Here, the amount of reduction degradation for each furnace interior position was obtained by the following method according to the description of the embodiment. For each furnace interior position, a pulverization matrix was created based on the reduction degradation index n and the Gaudin-Meloy distribution formula. The change amount of magnetite and the impact energy at each furnace interior position were substituted into the fully pulverized formula of formula (13) to obtain the reduction degradation index n for each furnace interior position. The setting of the particle size intervals required for obtaining the pulverization matrix was eight intervals consisting of particle size interval 1: 75 to 50 mm, particle size interval 2: 50 to 25 mm, particle size interval 3: 25 to 20 mm, particle size interval 4: 20 to 15 mm, particle size interval 5: 15 to 10 mm, particle size interval 6: 10 to 5 mm, particle size interval 7: 5 to 3 mm, and particle size interval 8: 3 to 0 mm. When calculating the pulverized matrix, the initial particle size of the Gaudin-Meloy distribution required was taken as the average diameter of each particle size interval. Also, the particle size distribution vector f before pulverization was such that f 1 corresponding to particle size interval 1 was 1.6 (mass %), f 2 corresponding to particle size interval 2 was 23.9 (mass %), f 3 corresponding to particle size interval 3 was 18.1 (mass %), f 4 corresponding to particle size interval 4 was 20 (mass %), f 5 corresponding to particle size interval 5 was 23.5 (mass %), f 6 corresponding to particle size interval 6 was 12.3 (mass %), f 7 corresponding to particle size interval 7 was 0.6 (mass %), f 8 corresponding to particle size interval 8 was 0 (mass %).

[0079] The product of the obtained pulverized matrix and the matrix of the particle size distribution vector f before pulverization was calculated to obtain the particle size distribution vector g after pulverization for each position in the furnace. From among these particle size distribution vectors g, the particle size distribution vectors corresponding to the particle size intervals with a particle diameter of 0 to 3 (mm) or less (that is, the g r corresponding to Equation (15)) were extracted, and the in-furnace distribution (distribution of the amount of reduction pulverization for each position in the furnace) of the particle size distribution vector g r is shown in Fig. 11. From this distribution, the in-furnace position where the amount of reduction pulverization is maximum was grasped, and the maximum value of the amount of reduction pulverization was extracted.

[0080] Referring to Figs. 9 and 10, by setting a low heat flux ratio, the temperature distribution in the furnace shifted toward the furnace top, and accordingly, the in-furnace position with a large amount of magnetite change also shifted toward the furnace top. From this, it can be seen that the amount of generated powder decreases as the heat flux ratio decreases.

[0081] Fig. 12 shows the relationship between the maximum value of the reduction pulverization amount and the heat flux ratio (corresponding to the first relationship information). The relationship between the heat flux ratio and the maximum value of the reduction pulverization amount is arranged in a linear equation, and it can be seen that the maximum value of the reduction pulverization amount decreases as the heat flux ratio decreases. At a low heat flux ratio, it is considered that the reduction pulverization can be suppressed because the reduction of the magnetite phase where significant reduction pulverization occurs ends relatively in the upper part of the furnace. When the heat flow ratio is defined as x and the maximum value of the reduced pulverization amount is defined as y, in this embodiment, these relationships can be defined by the following linear equation. y = 94.9x - 51.1 Note that the correlation coefficient (R 2 ) of such a linear equation was 0.9363.

[0082] Fig. 13 shows the relationship between the in-furnace pressure loss and the heat flow ratio (corresponding to the second relationship information). The relationship between the in-furnace pressure loss and the heat flow ratio is also arranged in a linear equation, and it can be seen that the in-furnace pressure loss increases as the heat flow ratio decreases. When the heat flow ratio is defined as x and the in-furnace pressure loss is defined as y, in this embodiment, these relationships can be defined by the following linear equation. y = -253.7x + 302.9 Note that the correlation coefficient (R 2 ) of such a linear equation was 0.9918. That is, from Figs. 12 and 13, it can be seen that the maximum value of the reduced pulverization amount and the in-furnace pressure loss have a trade-off relationship. When the heat flow ratio is increased (decreased), the reduced pulverization deteriorates (improves) and the in-furnace pressure loss improves (deteriorates). Based on Figs. 12 and 13, the maximum value of the reduced pulverization amount and the in-furnace pressure loss when the heat flow ratio is adjusted can be quantitatively grasped. Therefore, by appropriately adjusting the heat flow ratio, it is possible to prevent the significant occurrence of reduced pulverization and the sharp increase in the in-furnace pressure loss.

Explanation of Signs

[0083] 1 Blast furnace 2 Tuyere 3 Annular pipe 4 Blower pipe 5 Swirling chute 6 Tapping spout

Claims

1. A reduction degradation amount estimation step of obtaining the reduction degradation amount for each in-furnace position associated with a heat flow ratio for a plurality of heat flow ratios, A first relationship information acquisition step of obtaining first relationship information that is the relationship between the representative value of the reduction degradation amount for each in-furnace position and the heat flow ratio, A second relationship information acquisition step of obtaining second relationship information that is the relationship between the in-furnace pressure loss and the heat flow ratio, An adjustment step of adjusting the heat flow ratio based on the first relationship information and the second relationship information in order to achieve the target conditions for reduction degradation and pressure loss, An operating method for a blast furnace, characterized by comprising the above.

2. The adjustment step is a step of adjusting the heat flow ratio by adjusting the blowing parameters of the blast furnace. The operating method for a blast furnace according to Claim 1, characterized by the above.

3. The representative value is the maximum value of the reduction degradation amount for each in-furnace position. The operating method for a blast furnace according to Claim 1 or 2, characterized by the above.

4. The reduction degradation amount estimation step When defining the weight ratio for each particle size range of the iron raw material before reduction degradation as the pre-pulverization particle size distribution vector and the weight ratio for each particle size range of the iron raw material after reduction degradation as the post-pulverization particle size distribution vector, A reduction degradation index calculation step of obtaining the reduction degradation index for each in-furnace position based on the change amount of the magnetite content before and after reduction, which is the change amount of the magnetite, and the impact energy acting on the iron raw material, A pulverization matrix creation step of creating a pulverization matrix representing the degree of change in the weight ratio of the iron raw material due to reduction degradation for each predetermined particle size range for each in-furnace position using the reduction degradation index and the Gaudin-Meloy distribution formula, A post-pulverization particle size distribution vector calculation step of obtaining the post-pulverization particle size distribution vector from the product of the pulverization matrix and the pre-pulverization particle size distribution vector matrix for each in-furnace position, A reduction degradation amount calculation step of obtaining the reduction degradation amount for each in-furnace position based on the calculation result of the post-pulverization particle size distribution vector calculation step, The operating method for a blast furnace according to Claim 1 or 2, characterized by comprising the above.

5. The reduction degradation index calculation step is a step of obtaining the reduction degradation index by substituting the change amount of the magnetite and the impact energy for each in-furnace position into the following formula (A). The operating method for a blast furnace according to Claim 4, characterized by the above. 【Number 1】 ・・・・Formula (A) However, e is the impact energy, de is the infinitesimal change in the impact energy, and △Fe 3 O 4 is the change in magnetite, and d(△Fe 3 O 4 ) is the infinitesimal change in magnetite. Also, x １ , y １ , x ２ , y ２ , α １ , α ２ , α ３ , and β are all constants.

6. The matrix of the pulverized matrix created in the pulverized matrix creation step is DEG ｉｊ (However, the subscripts i and j are any integers from 1 to r, and r corresponds to the number of particle size intervals), and the operation method of the blast furnace according to claim 4, characterized in that it is represented by the following matrix (B). 【Number 2】 ・・・・Matrix (B) The subscripts i and j are the same DEG for each other ｉｊ corresponds to the iron raw material that remains without shifting from the particle size interval i after reduction degradation, and the subscripts i and j are different DEGs for each other ｉｊ corresponds to the iron raw material that shifts from the particle size interval i to the particle size interval j after reduction degradation.

7. Each DEG ｉｊ (however, excluding DEG ｒｒ ) is obtained based on the Gaudin-Meloy distribution DEG ｒｒ is 1 The operating method for a blast furnace according to Claim 6, characterized by the above.

8. DEGs included in the same row ｉｊ have the initial particle size set to the same value in the Gaudin-Meloy distribution, The operating method of a blast furnace according to claim 7, characterized in that this initial particle size varies depending on the row and becomes smaller as the row number increases.

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