Reduction pulverization amount estimation method in blast furnace

Abstract

To estimate a reduction pulverization amount for each furnace position of a blast furnace.SOLUTION: Provided is a reduction pulverization amount estimation method for estimating the reduction pulverization amount of an iron raw material charged into a blast furnace for each predetermined position in the furnace. The weight ratio of the iron raw material before reduction pulverization for each particle size section is defined as a particle size distribution vector before pulverization and the weight ratio of the iron raw material after reduction pulverization for each particle size section is defined as a particle size distribution vector after pulverization, a reduction pulverization index is obtained for each position in the furnace based on the amount of change in magnetite and impact energy acting on the iron raw material, and a pulverization matrix representing the degree of change in the weight ratio of the iron raw material due to reduction pulverization for each predetermined particle size section is prepared for each position in the furnace by using the reduction pulverization index and the Gaudin-Meloy distribution equation. A particle size distribution vector after pulverization is obtained from the product of the matrix of the pulverization matrix and the particle size distribution vector before pulverization for each position in the furnace, and a reduction pulverization amount for each position in the furnace is obtained based on the calculation result of the particle size distribution vector after pulverization calculation step.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present invention relates to a method for estimating the amount of reduction degradation in a blast furnace for each position in the furnace. [Background technology]

[0002] In the blast furnace process, raw materials are charged so that ore layers and coke layers are alternately formed inside the furnace, and hot air is blown from the bottom of the furnace, allowing the reduction and melting processes to proceed simultaneously, efficiently producing molten iron. The advantage of the blast furnace process is its high thermal efficiency, and in order to maintain this thermal efficiency, ensuring permeability inside the blast furnace (hereinafter also referred to as "furnace permeability") is considered one of the important operating indicators. The reason why ensuring permeability inside the furnace is important is that if permeability inside the furnace is impaired, heat exchange will not be sufficient, which will have a negative impact on the stable operation of the blast furnace.

[0003] Reduction and disintegration of ore is known as a factor of deterioration of furnace permeability. Reduction and disintegration causes a significant decrease in the particle size of the ore, which reduces the gaps between the ores in the furnace, thereby worsening the furnace permeability. If the deterioration of the furnace permeability becomes serious, it causes problems with lowering of the load and hanging, and the logistics stability and thermal conductivity inside the blast furnace are significantly impaired. Detailed investigations have been conducted to date on the mechanism of reduction and disintegration (for example, see Non-Patent Document 1).

[0004] In order to achieve stable operation of the blast furnace, it is important to take appropriate action before the reduction disintegration of ore becomes serious and to deal with it in advance. Therefore, a method for predicting the amount of reduction in the ore particle size due to reduction disintegration inside the blast furnace has been developed and reported.

[0005] Non-Patent Document 2 clarifies that the harmonic mean diameter of reduced ore and the reduction rate have a quadratic correlation, and proposes an estimation formula for estimating the harmonic mean diameter of powdered ore. Non-Patent Document 3 proposes a method for predicting the harmonic mean diameter of ore after reduction and disintegration inside a blast furnace, taking into account the specific surface area of ​​sintered ore after reduction and disintegration of the ore, with reference to Tanaka's formula, which is based on the Rittinger formula.

[0006] Patent Document 1 discloses a method of operating a blast furnace in which iron raw material with a high reduction degradation index (RDI) is charged into a region of the blast furnace dimensionless radius of 0.7 or more and 1 or less to increase the coke ratio. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2012-112032 A [Non-patent literature]

[0008] [Non-Patent Document 1] Inazumo et al.: Tetsu-to-Haganen, 68(1982), 2207. [Non-Patent Document 2] Iwanaga: Iron and Steel, 68(1982), 740. [Non-Patent Document 3] Nakajima et al.: Tetsu-to-Haganen, 73(1987), 1964. [Non-Patent Document 4] AM Gaudin and TM Meloy: Trans AIME, 223(1962), 40. [Non-Patent Document 5] Iron and Steel Vol.83(1997)No.2 [Non-Patent Document 6] Tetsu-to-Hagane Vol. 100 (2014) No. 11 Summary of the Invention [Problem to be solved by the invention]

[0009] Both Non-Patent Documents 2 and 3 merely estimated the harmonic mean diameter of the ore, and were unable to estimate the reduction disintegration amount for each position in the furnace. [Means for solving the problem]

[0010] The main factors that cause reduction disintegration are thought to be (1) and (2) below. (1) In the relatively upper, low-temperature part (400°C to 800°C) of the blast furnace lumpy zone, reduction disintegration occurs due to the volume expansion of magnetite that occurs when hematite is reduced to magnetite. (2) Unreduced magnetite remains at the lower part of the shaft where the impact energy is relatively large, causing reduction disintegration. Based on this viewpoint, the present inventor has come up with the following invention.

[0011] The present invention provides (1) a reduction degradation amount estimation method for estimating the reduction degradation amount of iron raw materials charged into a blast furnace for each predetermined furnace position, the reduction degradation amount estimation method including: a reduction degradation index calculation step for calculating a reduction degradation index for each furnace position based on a magnetite change amount, which is a change in the weight ratio of magnetite before and after reduction, and an impact energy acting on the iron raw materials, where the weight ratio for each particle size section of the iron raw materials before reduction degradation is defined as a particle size distribution vector before reduction, and the weight ratio for each particle size section of the iron raw materials after reduction degradation is defined as a particle size distribution vector after reduction; The method includes a powderization matrix creation step of creating, for each position in the furnace, a powderization matrix that represents the degree of change in the weight ratio of the iron raw material due to reduction powderization for each specified particle size range using the -Meloy distribution equation; a post-pulverization particle size distribution vector calculation step of calculating a post-pulverization particle size distribution vector for each position in the furnace from the product of the powderization matrix and the matrix of the particle size distribution vector before reduction; and a reduction powder amount calculation step of calculating the amount of reduction powder for each position in the furnace based on the calculation result of the post-pulverization particle size distribution vector calculation step.

[0012] (2) The method for estimating the reduction degradation amount of a blast furnace according to the above (1), characterized in that the reduction degradation index calculation step is a step of calculating a reduction degradation index by substituting the magnetite change amount and the impact energy for each position in the furnace into the following formula (A).

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[0013] (3) The matrix of the powder matrix created in the powder matrix creation step is DEG ij (wherein the subscripts i and j are integers from 1 to r, and r corresponds to the number of particle size intervals), the method for estimating the reduction disintegration amount in a blast furnace according to the above (1) or (2), characterized in that the amount is expressed by the following matrix (B) using:

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[0014] (4) Each DEG ij (However, DEG rr (excluding DEG) is calculated based on the Gaudin-Meloy distribution formula. rr The method for estimating the amount of reduction degradation in a blast furnace according to the above (3), wherein:

[0015] (5) DEGs in the same row ij The method for estimating the amount of reduction degradation in a blast furnace according to the above (4), characterized in that the initial particle size in the Gaudin-Meloy distribution equation is set to the same value, the initial particle size varies depending on the row, and becomes smaller as the row number increases.

[0016] (6) A method for operating a blast furnace based on an estimation result of the method for estimating the amount of reduction breakdown of a blast furnace described in (1) above, characterized in that, based on the amount of reduction breakdown for each position in the furnace determined in the reduction breakdown amount calculation step, an abnormal region in the furnace where the amount of reduction breakdown is equal to or greater than a predetermined value is identified, and an improvement action is implemented to reduce the amount of reduction breakdown in the abnormal region in the furnace. Effect of the Invention

[0017] According to the present invention, the reduction disintegration amount can be estimated for each position in a blast furnace. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram of a blast furnace. [Diagram 2] FIG. 1 is a conceptual diagram of mass motion in a drum testing machine. [Diagram 3] FIG. 2 is a conceptual diagram of a drum testing machine showing the rotating state of the drum. [Figure 4] 1 is a graph showing a schematic diagram of relationship information between impact energy and reduction disintegration index n1. [Diagram 5] 4 is a graph showing a schematic diagram of a reduction pattern applied in a reduction step. [Figure 6] FIG. 1 is a scatter plot of magnetite change amount and reduction degradation index. [Figure 7] 1 is a graph illustrating the concept of powdered matrix components. [Figure 8] 8 is a graph corresponding to FIG. 7. [Figure 9] FIG. 1 is a diagram showing the in-furnace distribution of magnetite change amount. [Figure 10] FIG. 1 is a diagram showing the distribution of impact energy inside the furnace. [Figure 11] This is a diagram showing the in-furnace distribution of the post-pulverization particle size distribution vector gr. [Figure 12] This is a diagram showing the excessive reduction disintegration region E. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] (Outline of blast furnace structure) Fig. 1 is a schematic diagram of a blast furnace. The blast furnace 1 is a bell-less type blast furnace equipped with a tuyere 2, an annular pipe 3, a blowpipe 4, a rotating chute 5, and a tap hole 6. However, the present invention can also be applied to a bell blast furnace.

[0020] The tuyere 2 is an inlet for blowing hot air generated in a hot stove (not shown) into the lower part of the blast furnace 1, and a plurality of tuyere are provided along the circumferential direction of the blast furnace 1.

[0021] The annular pipe 3 is disposed so as to surround the lower part of the blast furnace 1. A plurality of blowpipes 4 are provided intermittently in the circumferential direction on the annular pipe 3. The annular pipe 3 supplies hot air sent from the hot stove to the blowpipes 4.

[0022] Each blowpipe 4 is connected to the annular pipe 3 and is also connected to a different tuyere 2. The blowpipe 4 blows hot air flowing in from the annular pipe 3 into the blast furnace 1 through the tuyere 2.

[0023] The rotating chute 5 charges the iron raw materials and coke into the furnace while rotating around an axis extending in the vertical direction. The iron raw materials and coke charged from the rotating chute 5 alternately form an ore layer 11 and a coke layer 12 in the furnace. The iron raw materials may be lump ore, sintered ore, pellets, unburned carbon-containing agglomerated ore, etc. The iron raw materials may also contain a reduction assistant 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 as a fuel for melting the iron raw materials. The tilting angle and rotation speed of the rotating chute 5 can be controlled to charge the blast furnace raw materials at a desired position.

[0024] The tap hole 6 is provided at the bottom of the blast furnace 1 and taps the molten iron produced by the reduction of the iron raw material. A plurality of tap holes 6 are provided around the periphery of the furnace, and the molten iron can be tapped continuously or intermittently.

[0025] The method for estimating the amount of reduction degradation in a blast furnace according to the present invention includes (1) a reduction degradation index calculation step, (2) a degradation matrix creation step, (3) a post-degradation particle size distribution vector calculation step, and (4) a reduction degradation amount calculation step. Each step will be explained below.

[0026] (1) Reduction degradation index calculation step Reduction disintegration is affected by the amount of magnetite change (hereinafter also referred to as "△Fe3O4") and impact energy. The amount of magnetite change is the amount of change in the weight ratio of magnetite before and after reduction. In other words, 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. The weight ratio may be expressed as a percentage or as a ratio with the whole being 1. Impact energy refers to the stress experienced by the ferrous materials in the furnace. The amount of magnetite change and the impact energy vary depending on the location in the furnace.

[0027] The reduction degradation index calculation step is a step of deriving the following formula (1) expressed based on the magnetite change amount and the impact energy, and then calculating the reduction degradation index n(de, d(△Fe3O4)) for each position in the furnace based on the formula (1).

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[0028] Equation (1) is derived by carrying out the steps of: step 1 of deriving a reduction degradation index n1 corresponding to the impact energy applied to the iron raw material; step 2 of deriving a reduction degradation index n2 corresponding to the amount of magnetite change in the iron raw material; and step 3 of deriving the above-mentioned equation (1) using the reduction degradation index n1 and the reduction degradation index n2.

[0029] (Regarding step 1) In step 1, a rotational impact process is performed multiple times to apply rotational impact to an iron raw material reduced under specified reduction conditions, and a one-to-one relationship between the impact energy and the reduction degradation index n1 is obtained in each rotational impact process, thereby obtaining relationship information between the impact energy and the reduction degradation index n1. The predetermined reduction conditions may be conditions simulating the reduction conditions in a furnace. For example, the gas composition may be "20% by volume CO-10% by volume H2-70% by volume N2" and the reduction process may be performed according to the pattern shown in Fig. 5, which will be described later. Note that in step 1, unlike step 2, which will be described later, only one reduction condition is set.

[0030] The impact energy applied to the iron raw material in the furnace can be reproduced by the impact energy according to the rotation speed in a drum strength tester used in measuring the RDI of iron ore. 2 is a conceptual diagram of mass motion in a drum testing machine. The impact energy is the impact energy when the ferrous raw material O in the drum 21 falls freely along a fall trajectory FT. The impact energy (in other words, the fall impact energy of the ferrous raw material) can be calculated from the following formulas (2) to (6).

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[0031] The radius r of the drum in the drum testing machine 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 an angular velocity corresponding to a rotation speed of 30 (rpm). The angle θ is also a known value based on past knowledge.

[0032] 3 is a conceptual diagram of a drum testing machine showing the rotating 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 up the ferrous raw material O. When the angle θ of the lifter 22 with respect to the X-axis reaches a predetermined value, the ferrous raw material slides down from the lifter 22. The iron raw material receives two impacts during one rotation of the drum 21. By comparing the area of ​​the lifter 22 with the approximate projected circular area of ​​the sintered ore, the weight ratio of the iron raw material lifted by the lifter 22 can be determined.

[0033] Based on the above information, the impact energy received by the iron raw material can be calculated according to the number of rotations. For example, when 500 g of sintered ore is put into a drum 21 equipped with a lifter 22 of a given 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 is rotated 120 times is estimated to be 0.78 (J / piece).

[0034] As described above, the rotary impact process is carried out multiple times, and each time, one-to-one information on the impact energy and the reduction disintegration index is obtained by the following method. The iron raw material to which the rotational impact has been applied is taken out of the drum 21, and the particle size distribution (actual particle size distribution) is measured. Then, the Gaudin-Meloy distribution equation is parameter-fitted to this measured particle size distribution to obtain the reduction disintegration index. This allows one-to-one information on the impact energy and the reduction disintegration index to be obtained. The following equation (7) is the general formula for the Gaudin-Meloy distribution equation.

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[0035] The Gaudin-Meloy distribution equation is a particle size distribution estimation equation derived based on the random probability theory of crushing to an arbitrary particle size x, and is a distribution equation suitable for considering the "randomness of cracks occurring in iron raw materials". The Gaudin-Meloy distribution equation can more appropriately express the particle size distribution of iron raw materials subjected to reduction disintegration than the Gaudin-Schumann distribution equation or the Broadbent-Callcott distribution equation.

[0036] After the particle size distribution is measured, 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, and the measured particle size distribution is measured. At the same time, the Gaudin-Meloy distribution equation is parameter-fitted to the measured particle size distribution to obtain the reduction degradation index. This further provides one-to-one information on the impact energy and the reduction degradation index.

[0037] By repeating these steps (applying rotational impact, calculating the impact energy, measuring the actual particle size distribution, and calculating the reduction disintegration index), one-to-one information on the impact energy and reduction disintegration index is obtained for the number of rotational impact steps, and the relationship between the impact energy and the reduction disintegration index n1 is obtained. The relationship between the impact energy and the reduction disintegration index n1 is defined by the following general formula.

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[0038] FIG. 4 is a graph showing the relationship between impact energy and reduction disintegration index n1, with the horizontal axis showing impact energy (J / piece) and the vertical axis showing reduction disintegration index (-). In the illustrated example, the impact energies imparted in the respective rotational impact processes were 0.195 (J / piece), 0.39 (J / piece), 0.78 (J / piece), 1.56 (J / piece), 3.12 (J / piece), and 5.85 (J / piece), and the corresponding reduction disintegration indexes (-) were 0.56 (-), 0.86 (-), 1.09 (-), 1.37 (-), 1.74 (-), and 2.21 (-). Based on this information, the relationship between impact energy and reduction disintegration index n1 is summarized as follows: Equation (9) below is obtained.

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[0039] (Regarding step 2) The weight ratio of magnetite contained in the iron raw material is obtained in advance, and then a reduction process is carried out in which the iron raw material is reduced under different reduction conditions. The weight ratio of magnetite contained in the iron raw material is obtained after each reduction process, and a one-to-one relationship between the magnetite change amount and the reduction degradation index n2 is obtained by applying a rotational impact to the iron raw material reduced in each reduction process, thereby obtaining relationship information between the magnetite change amount and the reduction degradation index n2.

[0040] FIG. 5 is a graph showing a schematic diagram of the reduction pattern applied in the reduction step, in which the horizontal axis represents time (min) and the vertical axis represents temperature (° C.). Step S1 is a temperature increasing step in which the iron raw material is heated from room temperature to a reaction temperature at a heating rate of 10 (° C. / min) in an N 2 atmosphere. Step S2 is an incubation step in which the mixture is incubated at the reaction temperature for 30 minutes under a N2 atmosphere. Step S3 is a reduction step in which reduction is performed for 30 (min) at a reaction temperature ±10° C. under a reducing gas (a mixed gas of CO and H 2 ) atmosphere. Step S4 is a temperature-reducing step in which the atmospheric gas is switched from the reducing gas to N2 gas and the temperature inside the furnace is reduced to room temperature in an N2 atmosphere.

[0041] The reduction conditions can be changed by changing the time of the reduction process, the reduction temperature in the reduction step S3, and the gas composition of the reduction gas. 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 in the range of 1.2% to 19%. The "reduction rate" can be derived from the following formula.

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[0042] After the reduction test is carried out, the weight percentage of magnetite contained in the iron raw material is determined, and the amount of magnetite changed before and after reduction is determined.

[0043] After determining the weight ratio of magnetite contained in the reduced iron raw material, a rotational impact process is carried out to determine the particle size distribution (actually measured particle size distribution) of the pulverized iron raw material. Then, the Gaudin-Meloy distribution equation is parameter-fitted to this actually measured particle size distribution to determine the reduction degradation index. This provides one-to-one information on the magnetite change amount and the reduction degradation index. By repeating this process while changing the reduction conditions, one-to-one information on the magnetite change amount and the reduction degradation index can be obtained for the number of reduction processes, and the relationship information between the magnetite change amount and the reduction degradation index n2 can be obtained. The relationship between the magnetite change amount and the reduction degradation index n2 is defined by the following general formula.

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[0044] A method for acquiring the relationship information between the magnetite change amount and the reduction degradation index n2 will be described in more detail with reference to a specific example. Table 1 shows examples of reduction conditions. Note that the test time in Table 1 refers to the time from the start of the temperature increase step S1 to the end of the temperature decrease step S4. [Table 1]

[0045] For each of these samples 1 to 52, the one-to-one information of the magnetite change amount and the reduction disintegration index is obtained by the above-mentioned method. By plotting this information in the scatter diagram of FIG. 6 and performing parameter fitting to a quadratic function, the following formula (11) regarding the reduction disintegration index n2 is obtained. Note that, like in step 1, the rotational impact step was carried out using a drum strength tester. However, the rotation speed of the drum 21 was fixed at 120 rpm.

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[0046] (Regarding step 3) The following formula (12) is obtained by multiplying the reduction degradation index n1 corresponding to the impact energy in formula (8) and the reduction degradation index n2 corresponding to the magnetite change amount in formula (10). However, when multiplying the reduction degradation index n1 and the reduction degradation index n2, the reduction degradation index n2 is divided by a constant β because it is necessary to align the standards. The constant β can be set to the reduction degradation index n1 (or n2) when the reduction conditions are the same and the reduction degradation indexes n1 and n2 are the same, by comparing the scatter diagrams in Figures 4 and 6.

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[0047] By constructing an equation corresponding to equation (12) using equations (9) and (11) with the constants clarified, the following equation (13) is obtained.

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[0048] Finally, by totally differentiating equation (12), a general equation for calculating the reduction degradation index n(de,d(△Fe3O4)) for each position in the furnace in equation (1) is obtained. Equation (1) is shown again.

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[0049] More specifically, by totally differentiating formula (13), a general formula for calculating the reduction degradation index n(de,d(△Fe3O4)) for each position in the furnace is obtained. That is, the formula in which the constants in formula (1) are x1=0.44275, y1=-0.615, x2=1.15, y2=0.385, α1=0.0005, α2=0.0191, α3=0.001, and β=1.09 is the general formula for calculating the reduction degradation index n(de,d(△Fe3O4)) for each position in the furnace. These constants change depending on the conditions of steps 1 and 2, so the constants described here are merely examples.

[0050] Then, by substituting the impact energy and magnetite change amount at each furnace position into the formula (13) obtained by total pulverization, the reduction disintegration index n(de, d(△Fe3O4)) for each furnace position can be obtained. The impact energy at each furnace position can be calculated based on a known rigid-plastic model (see, for example, Non-Patent Document 5). The magnetite change amount at each furnace position can be calculated based on a known blast furnace mathematical model (see, for example, Non-Patent Document 6).

[0051] (2) Powder matrix preparation step Using the Gaudin-Meloy distribution equation and the reduction degradation index n(de,d(△Fe3O4)), a degradation matrix is ​​created that shows the degree of change in the weight ratio of the iron raw material due to reduction degradation for each particle size range. The Gaudin-Meloy distribution equation will not be explained again.

[0052] The powder matrix components that make up the powder matrix are DEG(x i ,x j ), the powder matrix component DEG(x i ,x j ) can be expressed by the following equation using the Gaudin-Meloy distribution equation:

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[0053] x j is the particle size of interest. M(x) is the cumulative particle size ratio at particle size x, and corresponds to the Gaudin-Meloy distribution formula. x i is the initial grain size (mm), and n i is the reduction degradation index derived in step 3 above. Note that the reduction degradation index n i is the initial particle size x i The subscript "i" is added because it changes depending on

[0054] Powdered 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 powdered matrix components, with the horizontal axis representing particle size (mm) and the vertical axis representing the cumulative undersize fraction. The Gaudin-Meloy distribution formula is expressed as follows: initial particle size x i and reduction disintegration index n i By substituting x, we can draw a distribution curve based on the Gaudin-Meloy distribution. j ~x j+1 By arbitrarily setting the particle size range of the powdered matrix component DEG(x i ,x j ) can be obtained. That is, the initial particle size x i When the iron raw material is reduced and pulverized, the particle size becomes x j The weight percentage of the following iron raw materials is M ( x j) Then, the particle size x j+1 The weight percentage of the following iron raw materials is M ( x j+1) Therefore, the grain size interval x j ~x j+1 The weight percentage of iron raw materials belonging to M ( x j) From M ( x j+1) This is the grain size interval x j ~x j+1 This corresponds to the powdered matrix component DEG. Powder matrix component DEG(x i ,x j ) are calculated, and the powder matrix is ​​the matrix representation of these. Here, it is desirable that the particle size section with the smallest particle size (hereinafter also referred to as the minimum particle size section) corresponds to the particle size of the reduced and powdered iron raw material. Since the particle size of the reduced and powdered iron raw material has been reported in various ranges of 2 mm or more and 8 mm or less, it may be appropriately set within this range. In other words, the minimum particle size section can be 0 to kmm (where k is 2 or more and 8 or less). There is no particular restriction on the particle size section above the minimum particle size section.

[0055] (3) Calculation step of particle size distribution vector after powderization The weight ratio of each particle size range of the iron raw material before reduction and disintegration is defined as the particle size distribution vector before disintegration f. The weight ratio of each particle size range of the iron raw material after reduction and disintegration is defined as the particle size distribution vector after disintegration g. In this case, the post-pulverization particle size distribution vector g is the matrix product of the powder matrix D and the pre-pulverization particle size distribution vector f, which can be expressed by the following formula.

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[0056] The technical significance of this determinant will be explained in detail. r and f1~fr The subscripts in correspond to the particle size intervals, and the smaller the number, the larger the particle size interval. In other words, g1 and f1 correspond to the particle size intervals with the largest particle size. For convenience of explanation, g1 to g r (f1~f r ) are defined as particle size interval 1 to particle size interval r, respectively. For example, when focusing on the particle size range 1 with the largest particle size, the balance due to reduction degradation of the iron raw material belonging to particle size range 1 is only a decrease. In other words, it is necessary to consider only the iron raw material remaining in particle size range 1 due to reduction degradation (in other words, it is not necessary to consider the iron raw material shifted from other particle size ranges). Therefore, the powder matrix components in the first row are 0 except for the first column, so the particle size distribution vector g1 (mass%) after degradation for particle size range 1 can be expressed by the following equation (16). g1=DEG 11 ×f1...Equation (16) Therefore, the "DEG 11 " is the powder matrix component corresponding to particle size interval 1, which represents the degree of change in the weight proportion of the iron raw material due to reduction powderization.

[0057] Also, looking at size range 2, which has the second largest particle size, the balance due to reduction disintegration of the iron raw material is the increase in the amount shifting from size range 1 to size range 2 and the decrease in the amount shifting from size range 2 to size ranges 3 to r. Since there is no iron raw material shifting from size ranges 3 to r to size range 2, the disintegration matrix component in the second row must be set to 0 except for the first and second columns. Therefore, the particle size distribution vector g2 (mass%) of particle size interval 2 can be expressed by the following formula (17). g2=DEG 12 f1+DEG 22 ·f2···Formula (17) "DEG 12 "DEG f1" corresponds to the iron raw material that has shifted from grain size range 1 to grain size range 2 due to reduction and disintegration. 22 "·f2" corresponds to the iron raw material that remained in grain size range 2 without shifting to grain size range 3~r. In equation (17), "DEG12 " and "DEG 22 " is the powdered matrix component corresponding to particle size interval 2, which represents the degree of change in the weight proportion of the iron raw material due to reduction powderization.

[0058] Similarly, the particle size distribution vector g3 (mass%) of particle size range 3, which has the third largest particle size, can be expressed by the following equation (18). g3=DEG 13 f1+DEG 23 f2+DEG 33 ·f3···Formula (18) "DEG 13 "DEG f1" corresponds to the iron raw material that has shifted from grain size range 1 to grain size range 3 due to reduction and disintegration. 23 "DEG f2" corresponds to iron raw material that has shifted from grain size range 2 to grain size range 3 due to reduction and disintegration. 33 "·f3" corresponds to the iron raw material that remained in grain size range 3 without shifting to grain size range 4~r. In equation (18), "DEG 13 ", "D.E.G. 23 " and "DEG 33 " is the powdered matrix component corresponding to particle size range 3, which represents the degree of change in the weight proportion of the iron raw material due to reduction powderization. For the particle size ranges 4 to r, the powdered matrix components can be determined in the same manner.

[0059] DEGrr is the minimum granularity interval x r Powdered matrix components in the particle size range x r Since the particle size never becomes smaller than ~0 (mm), DEGrr will always be 1.

[0060] The method of determining the powder matrix will be described in more detail with reference to FIG. 8. FIG. 8 is a graph corresponding to FIG. 7. However, for simplicity of explanation, the particle size intervals are set to three intervals, and the reduction powder index n is set to 1. The particle size interval 1 is set to 20-10 (mm), the particle size interval 2 is set to 10-3 (mm), and the particle size interval 3 is set to 3-0 (mm). Furthermore, the cumulative undersize fraction corresponding to a particle size of 20 (mm) is set to c, the cumulative undersize fraction corresponding to a particle size of 10 (mm) is set to b, and the cumulative undersize fraction corresponding to a particle size of 3 (mm) is set to a.

[0061] Each DEG can be determined based on the Gaudin-Meloy distribution equation as follows. DEG 11 =cb DEG 12 =ba DEG 13 =a-0=a In the Gaudin-Meloy distribution equation of equation (7), the cumulative undersize fraction c can be calculated by substituting 20 (mm) and 20 (mm) as the initial particle size X0 and particle size X. In the Gaudin-Meloy distribution equation of formula (7), the cumulative undersize fraction b can be calculated by substituting 20 (mm) and 10 (mm) as the initial particle size X0 and particle size X. In the Gaudin-Meloy distribution equation of equation (7), the cumulative undersize fraction a can be calculated by substituting 20 (mm) and 3 (mm) as the initial particle size X0 and particle size X. As mentioned above, DEG 11 corresponds to the iron raw material remaining in grain size range 1, and DEG 12 , DEG 13 corresponds to the iron raw material shifted from particle size interval 1, and since both are DEGs based on particle size interval 1, the maximum particle size of 20 (mm) in particle size interval 1 is set as the initial particle size X0. Note that another particle size included in particle size interval 1 (for example, the average particle size in particle size interval 1) may be set as the initial particle size X0.

[0062] DEG 22 =ba DEG 23 =a-0=a In the Gaudin-Meloy distribution equation of equation (7), the cumulative undersize fraction b can be calculated by substituting 10 (mm) and 10 (mm) as the initial particle size X0 and particle size X. In the Gaudin-Meloy distribution equation (7), the cumulative undersize fraction a can be calculated by substituting 10 (mm) and 3 (mm) for the initial particle size X0 and particle size X. 11 , DEG 12 , DEG 13 Since the initial particle size X0 is different from the calculation of DEG 11 , DEG 12 , DEG 13 is different. As mentioned above, DEG 22 corresponds to the iron raw material remaining in grain size range 2, and DEG 23 corresponds to the iron raw material shifted from particle size interval 2, and since both are DEGs based on particle size interval 2, 10 (mm), which is the maximum particle size in particle size interval 2, is set as the initial particle size X0. Note that other particle sizes included in particle size interval 2 (for example, the average particle size in particle size interval 2) may also be set as the initial particle size X0.

[0063] DEG 33 is 1, so there is no need to calculate it.

[0064] By the above calculation, each DEG constituting the milling matrix D can be obtained. Then, by calculating the matrix product of this milling matrix D and the particle size distribution vector f before milling, the particle size distribution vector g after milling can be obtained. The particle size distribution vector f before milling can be obtained by classifying the iron raw material before reduction milling with a sieve in advance.

[0065] The above-mentioned "reduction disintegration index calculation step," "disintegration matrix creation step," and "post-disintegration particle size distribution vector calculation step" are performed for each position in the furnace. By these steps, the particle size distribution after reduction disintegration (i.e., post-disintegration particle size distribution vector g) can be grasped for each position in the furnace.

[0066] (Reduction disintegration amount calculation step) Based on the calculation result of the post-pulverization particle size distribution vector calculation step, the reduction-pulverization amount is calculated for each position in the furnace. Here, the reduction-pulverization amount refers to the powder amount ratio of the iron raw material generated by the reduction-pulverization of the iron raw material in the furnace (in other words, the weight ratio of the low-particle-size iron raw material). As described above, various reports have been made on the value of the "low particle size" regarded as reduction-pulverization in the range of 2 mm to 8 mm. Therefore, an appropriate particle size is selected from this range, and the weight ratio of the iron raw material below the selected particle size is taken as the reduction-pulverization amount. For example, when the post-pulverization particle size distribution vector is defined by the weight ratio of the iron raw material included in the particle size range 1 of 20 to 10 mm, the weight ratio of the iron raw material included in the particle size range 2 of 10 to 3 mm, and the weight ratio of the iron raw material included in the particle size range 3 of 3 to 0 mm, the weight ratio of the iron raw material in the particle size range 3 can be taken as the "reduction-pulverization amount".

[0067] The reduction degradation amount for each furnace position obtained in the reduction degradation amount calculation step can be used to identify the area where reduction degradation becomes serious. For example, the top X% (e.g., 20%) of furnace positions with the highest reduction degradation amount can be regarded as the area where reduction degradation becomes serious. Then, by implementing improvement action to reduce reduction degradation in this area, it is possible to prevent a decrease in furnace air permeability, etc. The improvement action is not particularly limited, but for example, it is possible to charge iron raw materials with a relatively low reduction degradation index (RDI) into the area where reduction degradation becomes serious.

[0068] (Example) The present invention will be specifically described with reference to examples. The furnace region was divided into meshes, and the magnetite change and impact energy were calculated for each mesh as a furnace position (analysis unit). When the dimensionless radius of the blast furnace is 1 and the dimensionless furnace height is 1, the size of each mesh was 0.1 in the furnace diameter direction and 0.025 in the furnace height direction. The magnetite change was calculated based on a blast furnace mathematical model. The impact energy was calculated based on a rigid-plastic model.

[0069] The in-furnace distribution of magnetite change is shown in Fig. 9, and the in-furnace distribution of impact energy is shown in Fig. 10. Note that for the in-furnace distribution of impact energy in Fig. 10, the calculation region was limited from the furnace top to the shaft. The blast furnace operating parameters that served as the basis for the model calculations were set to the average parameters on a stable operating day (see Table 2). [Table 2] Here, RAR is the reducing agent ratio, CR is the coke ratio, and PCR is the pulverized coal ratio.

[0070] A powder matrix was created for each furnace position based on the reduction powder index n and the Gaudin-Meloy distribution equation. The reduction powder index n for each furnace position was calculated by substituting the magnetite change amount and impact energy at each furnace position into the total fine powder equation (13). The particle size intervals required to determine the powdered matrix were eight intervals: particle size interval 1: 75-50 mm, particle size interval 2: 50-25 mm, particle size interval 3: 25-20 mm, particle size interval 4: 20-15 mm, particle size interval 5: 15-10 mm, particle size interval 6: 10-5 mm, particle size interval 7: 5-3 mm, and particle size interval 8: 3-0 mm. The initial particle size of the Gaudin-Meloy distribution equation required to calculate the powder matrix was the average diameter of each particle size interval. In addition, the particle size distribution vector f before powderization was set as follows: f1 corresponding to particle size interval 1 was 1.6 (mass%), f2 corresponding to particle size interval 2 was 23.9 (mass%), f3 corresponding to particle size interval 3 was 18.1 (mass%), f4 corresponding to particle size interval 4 was 20 (mass%), f5 corresponding to particle size interval 5 was 23.5 (mass%), f6 corresponding to particle size interval 6 was 12.3 (mass%), f7 corresponding to particle size interval 7 was 0.6 (mass%), and f8 corresponding to particle size interval 8 was 0 (mass%).

[0071] The product of the obtained pulverization 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. Among these particle size distribution vectors g, the particle size distribution vector corresponding to the particle size range of 0 to 3 (mm) or less (i.e., g in Equation (15)) was selected. r(corresponding to r The distribution inside the furnace is shown in Figure 11.

[0072] With reference to Fig. 9, the amount of magnetite change was high in the temperature range of 600 to 800° C. With reference to Fig. 10, the impact energy was high in the periphery of the furnace. Therefore, as shown in FIG. 11, it is understood that the reduction disintegration amount increases significantly in the temperature range of 600 to 800° C. in the peripheral part of the furnace.

[0073] Particle size distribution vector after powderization g r The top 20% of regions with the highest values ​​of β (hereinafter also referred to as excessive reduction disintegration region E) were identified and shown in FIG. 12. The excessive reduction disintegration region E (corresponding to the "inner furnace abnormal region") appeared at a furnace diameter position of 0.66 to 1.0 of the dimensionless radius of the blast furnace. Therefore, by taking action to improve the permeability at this position, it is possible to efficiently and in advance prevent deterioration of permeability. The improvement action has been described in the embodiment, so the description will not be repeated. In addition, in Patent Document 1, raw materials with high reduction disintegration tendency (RDI) are used in the region of the blast furnace dimensionless radius of 0.7 to 1, and reduction disintegration is reduced by increasing the coke ratio, which is different from the improvement action derived from the examples of the present invention. [Explanation of symbols]

[0074] 1 blast furnace 2 tuyere 3 annular pipe 4 blowpipe 5 swivel chute 6 tap hole

Claims

1. A reduction and degradation amount estimation method for estimating a reduction and degradation amount of iron raw materials charged into a blast furnace at each predetermined position in the furnace, comprising: When the weight ratio of each particle size range of the iron raw material before reduction and disintegration is defined as the particle size distribution vector before disintegration, and the weight ratio of each particle size range of the iron raw material after reduction and disintegration is defined as the particle size distribution vector after disintegration, A reduction degradation index calculation step of calculating a reduction degradation index for each position in the furnace based on a magnetite change amount, which is a change amount of the weight ratio of magnetite before and after reduction, and an impact energy acting on the iron raw material; A powder matrix creation step of creating a powder matrix for each position in the furnace, the powder matrix representing the degree of change in the weight ratio of the iron raw material due to reduction powder for each predetermined particle size range using the reduction powder index and the Gaudin-Meloy distribution equation; A post-pulverization particle size distribution vector calculation step of calculating a post-pulverization particle size distribution vector from the product of the pulverization matrix and the matrix of the pre-pulverization particle size distribution vector for each position in the furnace; A reduction disintegration amount calculation step of calculating a reduction disintegration amount for each position in the furnace based on the calculation result of the post-disintegration particle size distribution vector calculation step; A method for estimating reduction degradation amount in a blast furnace, comprising:

2. The reduction degradation amount estimation method according to claim 1, characterized in that the reduction degradation index calculation step is a step of calculating a reduction degradation index by substituting the magnetite change amount and impact energy for each position in the furnace into the following formula (A). [0010] where e is the impact energy, de is the small change in impact energy, △Fe 3 O 4 is the amount of magnetite change, d(△Fe 3 O 4 ) is the small change in magnetite. Also, x １ , y １ , x ２ , y ２ , α １ , α ２ , α ３ , β are all constants.

3. The matrix of the powder matrix prepared in the powder matrix preparation step is DEG ｉｊ The method for estimating the amount of reduction disintegration in a blast furnace according to claim 1 or 2, characterized in that the amount of reduction disintegration in a blast furnace is expressed by the following matrix (B) using (wherein the subscripts i and j are integers from 1 to r, and r corresponds to the number of particle size intervals). [0025] DEGs with the same subscripts i and j ｉｊ corresponds to the iron raw material remaining after reduction and disintegration without shifting from the grain size range i, and the subscripts i and j are different DEGs ｉｊ corresponds to the iron raw material that shifts from grain size interval i to grain size interval j after reduction disintegration.

4. Each DEG ｉｊ (However, DEG ｒｒ (excluding) is calculated based on the Gaudin-Meloy distribution formula, and DEG ｒｒ is 1, The method for estimating the amount of reduction breakdown in a blast furnace according to claim 3.

5. DEGs in the same row ｉｊ is set to the same value for the initial particle size in the Gaudin-Meloy distribution equation, The method for estimating the amount of reduction degradation in a blast furnace according to claim 4, characterized in that the initial particle size varies depending on the row, and becomes smaller as the row number increases.

6. A method for operating a blast furnace based on an estimation result of the method for estimating the amount of reduction disintegration of a blast furnace according to claim 1, Identifying an abnormal region in the furnace where the amount of reduction degradation is equal to or greater than a predetermined value based on the amount of reduction degradation for each position in the furnace calculated in the reduction degradation amount calculation step; A method for operating a blast furnace, comprising carrying out an improvement action for reducing an amount of reduction degradation in the abnormal region inside the furnace.

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