Method for adjusting particle size distribution of sintered ore and method for estimating the change in reduction rate Rs* at the start of fusion ΔRs*

Abstract

To provide an adjustment method of the particle size distribution of sintered ore in which the reduction material ratio can be decreased.SOLUTION: A method of adjusting the particle size distribution of the charged sintered ore used to form an ore layer involves adjusting the particle size distribution of the charged sintered ore so that a harmonic mean particle size Dp of the charged sintered ore approaches a reference value S. In the method of adjusting the particle size distribution of sintered ore, the reference value S is determined as the harmonic mean particle size Dp at which the reduction rate at the start of fusion Rs* is the maximum value in the Rs*-Dp curve showing the relationship between the reduction rate at the start of fusion Rs* of the sintered ore packed bed for investigation when the pressure loss of the sintered ore packed bed for investigation to determine the reference value S reaches a specific value and the harmonic mean particle size Dp of the sintered ore for investigation used to obtain the reduction rate at the start of fusion Rs*.SELECTED DRAWING: Figure 6c

Description

[Technical Field]

[0001] The present invention relates to a method for adjusting the particle size distribution of sintered ore, and a reduction ratio Rs at the start of fusion of sintered ore before and after adjusting the particle size distribution. * The change in ΔRs * This relates to a method for estimating [Background technology]

[0002] In a blast furnace, iron-containing ore (sinter, pellets, lump ore, etc.) and coke (reducing agent and fuel) are alternately charged from the top of the furnace, and hot air is blown in from tuyeres at the bottom of the furnace, along with auxiliary fuel such as pulverized coal. The ore and coke (hereinafter collectively referred to as "burden") charged from the top of the furnace form alternating ore layers and coke layers, respectively. As the ore and coke are lowered in the blast furnace, they gradually descend toward the bottom, where they are heated by gases rising from the bottom.

[0003] The ore raw materials descend while being heated and reduced in the blast furnace. When they reach the bottom of the furnace, they begin to soften and fuse, forming a cohesive ore layer. In the cohesive ore layer, the gaps between the ore raw materials decrease, reducing gas permeability. As a result, gas passes through the coke layer between the cohesive ore layers and rises toward the furnace top. Therefore, the shape of the cohesive zone has a significant impact on the permeability of the blast furnace. The cohesive zone refers to the area in the blast furnace where the cohesive ore layer exists (including the coke layer between the cohesive ore layers).

[0004] The high-temperature properties of raw ore are one of the important factors that determine the shape of the cohesive zone. Conventionally, the high-temperature properties of raw ore have been evaluated using indicators such as the reduction ratio at the start of fusion (Rs), the temperature at which fusion begins (Ts), the temperature at which dripping begins (Td), or the difference between these (ΔT = Td - Ts) determined by a load-softening test (Non-Patent Document 1).

[0005] Another known index for evaluating the high-temperature properties of raw ore (hereinafter also referred to as "high-temperature property evaluation index") is the S value (the area of ​​the portion where the pressure drop is 200 mmH2O or more in the time-pressure drop curve obtained by heating and reducing sintered ore). In Patent Document 1, sintered ore is divided into two types based on the high-temperature properties (S value), and the sintered ore with poor high-temperature properties is charged as the lower layer, and the sintered ore with good high-temperature properties is charged above it as the upper layer, thereby improving the reducibility of the entire ore layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-309306 [Non-patent literature]

[0007] [Non-Patent Document 1] Iron and Steel, Vol. 83 (1997), pp. 97-102 [Non-patent document 2] Iron and Steel, Vol. 77 (1991), pp. 1561-1568 [Non-patent document 3] Iron and Steel, Vol. 80 (1994), pp. 431-439 [Non-patent document 4] Iron and Steel, Vol. 98 (2012), pp. 431-439 [Non-Patent Document 5] Iron and Steel, Vol. 66 (1980), pp. 1908-1917 [Non-patent document 6] Iron and Steel, Vol. 100 (2014), pp. 270-276 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to provide a method for adjusting the particle size distribution of sintered ore, which can reduce the reducing agent ratio. The present invention also aims to provide a method for adjusting the particle size distribution of sintered ore, which can reduce the reduction ratio Rs at the start of fusion of sintered ore before and after adjusting the particle size distribution. *The change in ΔRs * Another object of the present invention is to provide a method for estimating [Means for solving the problem]

[0009] In order to solve the above problems, the method for adjusting the particle size distribution of sintered ore for charging used to form an ore layer according to the present invention includes: (1) adjusting the particle size distribution of the sintered ore for charging so that the harmonic mean particle size Dp of the sintered ore for charging approaches a reference value S, and determining the reference value S when the pressure loss of the sintered ore packed bed for fusion start Rs of the sintered ore packed bed for fusion start reaches a predetermined value. * and the reduction rate Rs at the start of fusion * The harmonic mean particle size Dp of the sintered ore used for the study was obtained, and Rs * In the -Dp curve, the reduction rate Rs at the start of fusion * The reference value S is defined as the harmonic mean particle diameter Dp at which the value of

[0010] (2) The method for adjusting a particle size distribution according to (1), characterized in that the particle size distribution of the sintered ore to be charged is adjusted so that the initial void ratio ε0 of the sintered ore to be charged packed bed made of the sintered ore to be charged is higher after adjusting the particle size distribution than before adjusting the particle size distribution.

[0011] (3) The reduction rate Rs at the start of fusion * The method for adjusting particle size distribution according to (2), wherein the maximum value of is a local maximum value.

[0012] (4) When the harmonic mean particle diameter Dp of the sintered ore for charging before adjusting the particle size distribution exceeds the reference value S, the harmonic mean particle diameter Dp of the sintered ore for charging after adjusting the particle size distribution a The method for adjusting particle size distribution according to (3), wherein the particle size distribution of the sintered ore to be charged is adjusted so that the reference value S is equal to or greater than the reference value S.

[0013] (5) The method for adjusting the particle size distribution according to (4), characterized in that the particle size distribution of the sintered ore to be charged is adjusted by reducing the proportion of coarse sintered ore exceeding a predetermined particle size.

[0014] (6) When the harmonic mean particle diameter Dp of the sintered ore for charging before adjusting the particle size distribution is less than the reference value S, the harmonic mean particle diameter Dp of the sintered ore for charging after adjusting the particle size distribution a The method for adjusting particle size distribution according to (3), characterized in that the particle size distribution of the sintered ore to be charged is adjusted so that the reference value S is not more than the reference value S.

[0015] (7) The method for adjusting the particle size distribution according to (6), characterized in that the particle size distribution of the sintered ore to be charged is adjusted by reducing the proportion of fine sintered ore having a particle size less than a predetermined value.

[0016] (8) Harmonic mean particle size Dp of the sintered ore for charging after adjusting the particle size distribution a The method for adjusting a particle size distribution according to any one of (3) to (7), characterized in that the particle size distribution of the sintered ore to be charged is adjusted so that the following formula (1) is satisfied:

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[0017] (9) The method for adjusting particle size distribution according to any one of (1) to (8), wherein the reference value S is 12 mm.

[0018] (10) The reduction rate Rs of the sintered ore packed bed at the start of fusion * (9) The method for adjusting a particle size distribution according to any one of (1) to (9), characterized in that the particle size distribution is obtained using one or more of the following in a blast furnace into which the sintered ore is charged: (a) a packing state of a sintered ore packed bed made of the sintered ore; (b) a temperature of the sintered ore packed bed; (c) a composition and flow rate of a reducing gas flowing into the sintered ore packed bed; and (d) a load applied to the sintered ore packed bed.

[0019] (11) The reduction ratio Rs at the start of fusion for the sintered ore for charging, the particle size distribution of which is adjusted by the adjustment method described in (4), * The change in ΔRs * The change amount ΔRs is estimated based on the following equation (2). * Estimation method.

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[0020] (12) The change amount ΔRs according to (11), characterized in that the reference value S is 12, the C1 is −1.2, and the D1 is 150. * Estimation method.

[0021] (13) The reduction ratio Rs at the start of fusion for the sintered ore for charging, the particle size distribution of which is adjusted by the adjustment method described in (6), * The change in ΔRs * The change amount ΔRs is estimated based on the following equation (3). * Estimation method.

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[0022] (14) The change amount ΔRs according to (13), characterized in that the reference value S is 12, the C2 is 1.2, and the D2 is 150. * Estimation method. [Effects of the Invention]

[0023] According to the present invention, it is possible to provide a method for adjusting the particle size distribution of sintered ore, which can reduce the reducing agent ratio. Also, according to the present invention, it is possible to obtain the reduction ratio Rs at the start of fusion of sintered ore before and after adjusting the particle size distribution. * The change in ΔRs * It is possible to provide a method for estimating [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a diagram illustrating an overview of an Rs* estimation model. [Figure 2a] 1 is a graph showing a change in temperature of a sintered ore packed bed. [Figure 2b] 10 is a graph showing a change in a load applied to a sintered ore packed bed. [Figure 2c] 1 is a graph showing a change in the flow rate of a reducing gas flowing through a sintered ore packed bed. [Figure 2d] 1 is a graph showing a change in the composition of a reducing gas flowing through a sintered ore packed bed. [Figure 2e] 1 is a graph showing a change in the composition of a reducing gas flowing through a sintered ore packed bed. [Figure 2f] 1 is a graph showing a change in pressure of a reducing gas flowing through a sintered ore packed bed. [Figure 3] 10 is a flowchart showing a procedure for estimating a reduction rate Rs* at the start of fusion. [Figure 4] FIG. 1 is a diagram illustrating an analysis method using X-ray CT images. [Figure 5a] 1 is a graph showing a change in temperature of a sintered ore packed bed. [Figure 5b] 1 is a graph showing a change in the composition of a reducing gas flowing through a sintered ore packed bed. [Figure 5c] 10 is a graph showing a change in a load applied to a sintered ore packed bed. [Figure 6a] 1 is a graph showing the relationship between fusion start temperature Ts* and harmonic mean particle diameter Dp. [Figure 6b] 1 is a graph showing the relationship between the reduction rate R1200 and the harmonic mean particle diameter Dp. [Figure 6c] 1 is a graph showing the relationship between the reduction rate Rs* at the start of fusion and the harmonic mean particle size Dp. [Figure 7a] 1 is a graph showing the relationship between the sintered +25 mm ratio and the initial porosity ε0, and the relationship between the sintered +25 mm ratio and the harmonic mean particle size Dp. [Figure 7b] 1 is a graph showing the relationship between the reducing agent ratio and the reduction rate Rs* at the start of fusion regarding the sintered ore used when calculating the reducing agent ratio. DETAILED DESCRIPTION OF THE INVENTION

[0025] First, the circumstances leading to the completion of the present invention will be described.

[0026] Conventionally, the fusion start temperature Ts and the reduction ratio at fusion start Rs have been used as indices for evaluating the high-temperature properties of ore raw materials (high-temperature property evaluation indices). The fusion start temperature Ts and the reduction ratio at fusion start Rs are defined as the temperature (temperature of the ore layer) and reduction ratio (reduction ratio of the ore layer) when the pressure drop generated in the ore layer reaches a predetermined value, respectively, and are obtained by reducing the ore raw material using a high-temperature properties test device under the test conditions shown in Non-Patent Document 1. The predetermined value represents the pressure drop when the ore fusion layer is formed.

[0027] On the other hand, in a blast furnace, (a) the packing state of the ore layer (particle size (harmonic mean particle size), porosity, layer thickness, mixed charging of various raw materials, etc.), (b) the temperature of the ore layer, (c) the composition and flow rate of the reducing gas flowing through the ore layer, and (d) the load on the ore layer vary depending on the blast furnace operating conditions. These conditions (hereinafter also referred to as "high-temperature property-related conditions") affect the high-temperature properties of the ore raw material. Therefore, it is preferable that the high-temperature property evaluation index of the ore raw material reflects the influence of one or more of the high-temperature property-related conditions of the blast furnace into which the ore raw material to be evaluated is charged. However, the fusion start temperature Ts and the reduction ratio at the start of fusion Rs obtained by the method described in Non-Patent Document 1 do not easily reflect these influences. For example, in Non-Patent Document 1, the reduction ratio at the start of fusion Rs is measured using sintered ore sized to 10 to 15 mm.

[0028] Based on this knowledge, the present inventors have conducted a study and have found a new high-temperature property evaluation index, the ore layer fusion start temperature (hereinafter referred to as "fusion start temperature Ts * ") and the reduction rate at the start of fusion of the ore layer (hereinafter referred to as "reduction rate at the start of fusion Rs * The fusion starting temperature Ts * is the temperature (temperature of the ore layer) when the pressure drop of the ore layer reaches a predetermined value, and is the temperature obtained using the high-temperature property related conditions. * is the reduction rate of the ore layer when the pressure drop of the ore layer reaches a predetermined value, and is the reduction rate obtained using the high-temperature property-related conditions.

[0029] The fusion start temperature Ts* and reduction rate at the start of fusion Rs * is a high-temperature property evaluation index required for the ore layer, not for the ore raw material. Fusion start temperature Ts * and reduction rate at the start of fusion Rs * The predetermined value used to calculate the temperature Ts is the pressure loss (or its gradient) when the ore fusion layer is formed, and can be, for example, 200 x 9.8 Pa or 50 kPa / m. * and reduction rate at the start of fusion Rs * Details will be given later.

[0030] The inventors have determined that the fusion starting temperature Ts * and reduction rate at the start of fusion Rs * Further investigation was carried out, and attention was focused on the particle size among the above-mentioned (a) packing condition of the ore layer (particle size (harmonic mean particle size), void ratio, layer thickness, mixed charging of various raw materials, etc.). When the particle size of the ore raw material is reduced, the contact area with the reducing gas increases, and the reduction rate of the ore raw material increases. This is because the reduction rate at the start of fusion Rs * On the other hand, as the contact area with the reducing gas increases, the pressure loss of the ore layer increases. Therefore, as the contact area increases, the melting start temperature Ts * The fusion starting temperature Ts * The decrease in the reduction rate Rs * This can be a factor that reduces the particle size. In other words, there is a trade-off between reducibility and permeability with respect to particle size. Based on this finding, the present inventors have attempted to clarify the particle size distribution appropriate for sintered ore, which is one of the ore raw materials, in blast furnace operation from the viewpoint of high-temperature properties.

[0031] Therefore, as will be described later, the present inventors have used an ore layer formed only from sintered ore (hereinafter also referred to as a "sintered ore packed layer") to measure the reduction rate Rs at the start of fusion. * The relationship between the harmonic mean particle diameter Dp of the sintered ore and the reduction ratio Rs at the start of fusion of the ore layer formed using the sintered ore was investigated. As a result, by adjusting the particle size distribution of the sintered ore so that the harmonic mean particle diameter Dp of the sintered ore approaches the standard value S described later, *The inventors have found that the sintered ore for determining the reference value S can be increased and the reducing agent rate can be reduced, and have thus completed the present invention. Hereinafter, the sintered ore for determining the reference value S may be referred to as "sintered ore for study."

[0032] In this specification, the term "ore layer" refers to a layer of particle packed beds formed in a blast furnace that contains raw ore, and the raw ore refers to a raw material containing 50% by mass or more of iron. Specific examples of raw ore include sintered ore, pellets, and lump ore. In this specification, the term "cohesive ore layer" refers to an ore layer in which the raw ore is softened and / or fused, and the term "cohesive zone" refers to a region in a blast furnace where the cohesive ore layer exists (including the coke layer between the cohesive ore layers).

[0033] An embodiment of the present invention will be described below.

[0034] The adjustment method of this embodiment is a method for adjusting the particle size distribution of sintered ore. The sintered ore whose particle size distribution has been adjusted by the adjustment method of this embodiment is used to form an ore layer. Hereinafter, the sintered ore whose particle size distribution has been adjusted and which forms an ore layer may be referred to as "charged sintered ore."

[0035] The ore layer does not necessarily have to be formed only from sintered ore for charging whose particle size distribution has been adjusted by the adjustment method of this embodiment, but may be formed to include, in addition to the sintered ore for charging, other raw materials such as ore raw materials other than sintered ore, coke, ferrocoke, auxiliary materials, etc.

[0036] The adjusting method of this embodiment adjusts the particle size distribution of the sintered ore to be charged so as to satisfy the first condition shown below.

[0037] The first condition is that the harmonic mean particle size Dp of the sintered ore to be charged (i.e., the sintered ore to be charged before the particle size distribution is adjusted), whose particle size distribution is to be adjusted, approaches the reference value S by adjusting the particle size distribution of the sintered ore to be charged.

[0038] In this embodiment, the harmonic mean particle size Dp of the sintered ore to be charged is defined by the following formula (4).

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[0039] Here, the harmonic mean particle diameter Dp approaching the reference value S means that the absolute value of the difference between the harmonic mean particle diameter Dp and the reference value S becomes smaller. If this absolute value becomes smaller, a harmonic mean particle diameter Dp that exceeds the reference value S may become less than the reference value S by adjusting the particle size distribution, or a harmonic mean particle diameter Dp that is less than the reference value S may exceed the reference value S by adjusting the particle size distribution.

[0040] In the adjustment method of this embodiment, the particle size distribution can be adjusted by changing the proportion (mass ratio) of sintered ore for charge within particle size range i. For example, when the harmonic mean particle size Dp of the sintered ore for charge, whose particle size distribution is to be adjusted, exceeds a reference value S, the particle size distribution can be adjusted to satisfy the first condition by reducing the proportion of coarse sintered ore exceeding the predetermined particle size. Note that the aforementioned predetermined particle size is a particle size exceeding the harmonic mean particle size Dp of the sintered ore for charge, whose particle size distribution is to be adjusted, and is, for example, 50 mm. Also, when the harmonic mean particle size Dp of the sintered ore for charge, whose particle size distribution is to be adjusted, is less than the reference value S, the particle size distribution can be adjusted to satisfy the first condition by reducing the proportion of fine sintered ore less than the predetermined particle size. Note that the aforementioned predetermined particle size is a particle size less than the harmonic mean particle size Dp, and is, for example, 5 mm.

[0041] Next, the reference value S to which the harmonic mean particle diameter Dp is to be approximated will be specifically described.

[0042] The reference value S is the reduction rate Rs of the sintered ore packed bed when the pressure drop of the sintered ore packed bed reaches a predetermined value.* (Reduction rate at the start of fusion Rs * ) and the reduction rate at the start of fusion Rs * The curve showing the relationship between the harmonic mean particle size Dp of the sintered ore used for the study (hereinafter referred to as "Rs * In the "-Dp curve", the reduction rate at the start of fusion Rs * is the harmonic mean particle diameter Dp at which the maximum value is reached.

[0043] The standard value S is determined by the test conditions of the load-softening test described later and Rs * It cannot be determined uniquely because it may differ depending on the input conditions of the estimation model, but it can be set to 12 [mm], for example. * The -Dp curve may be obtained as a straight line.

[0044] Rs * To obtain the -Dp curve, measurements from a load-softening test or calculations using a mathematical model are used. For example, the calculation method uses the high-temperature property-related conditions (a) the packing state of the sinter packed bed, (b) the temperature of the sinter packed bed, (c) the composition and flow rate of the reducing gas flowing through the sinter packed bed, and (d) the load applied to the sinter packed bed as input conditions to calculate the reduction rate Rs at the start of fusion of the sinter packed bed. * A model for calculating Rs * More specifically, multiple input conditions that differ only in the harmonic mean particle size Dp of the sintered ore under consideration are used as Rs * Input each of these into the estimation model, and calculate the reduction rate Rs at the start of fusion of the sinter packed bed for each input condition. * Calculate the reduction rate at the start of fusion Rs * and the reduction rate at the start of fusion Rs * It can be obtained by plotting the harmonic mean particle diameter Dp of the sintered ore used in the calculation of

[0045] Regarding the condition (a) for high-temperature properties, the sintered ore to be charged and the sintered ore to be examined do not necessarily have to have the same porosity and other properties, and sintered ore having general properties may be used as the sintered ore to be examined. According to the study by the inventors, even if the sintered ores have different porosity and other properties, the reduction rate Rs at the start of fusion with respect to the change in the harmonic mean particle diameter Dp is * The response of the sintered ore to be charged can be considered to be similar, and sensitivity analysis can be performed without unifying the properties of the charged sintered ore and the sintered ore to be investigated. * The change in ΔRs * To obtain the reduction ratio Rs at the start of fusion for the harmonic mean particle diameter Dp, * The change rates C1 and C2 (described later) and the reduction rate Rs at the start of fusion relative to the initial porosity ε0 * The change rates D1 and D2 (described later) can be determined with sufficient reliability even if the properties of the sintered ore for charging and the sintered ore for investigation are not the same.

[0046] The closer the conditions (void ratio and other properties) of the charging sinter and the sinter under investigation are to each other, the more preferable it is, and it is most preferable that the conditions of (a) are the same. In other words, it is most preferable to use the packed state of the charging sinter packed bed made of (a) charging sinter as the input condition. The closer the conditions of (a) are between the charging sinter and the sinter under investigation, the greater the Rs * Reduction rate Rs at the start of fusion calculated by the estimation model * The reduction ratio Rs at the start of fusion, which better reflects the high-temperature properties of the blast furnace into which the sintered ore for charging, which is the target of particle size distribution adjustment, is charged (hereinafter also referred to as the "target blast furnace"). * can be obtained.

[0047] Below, Rs. * The estimation model will now be described in detail.

[0048] (Rs * (Summary of the estimation model) Rs * In the estimation model, first, one layer of the sintered ore packed bed for study immediately after the sintered ore for study is charged into a blast furnace is divided into a plurality of regions (regions divided by a computational grid (hereinafter also referred to as "computational cells")) arranged in the bed height direction. Next, for each computational cell, the reduction rate of the sintered ore for study, the contraction rate of the sintered ore packed bed for study, and the pressure loss occurring in the sintered ore packed bed for study are estimated. To estimate the reduction rate, contraction rate, and pressure loss, the following input conditions are used: (a) the packing state of the sintered ore packed bed for study, (b) the temperature of the sintered ore packed bed for study, (c) the composition and flow rate of the reducing gas flowing through the sintered ore packed bed for study, and (d) the load acting on the sintered ore packed bed for study.

[0049] As mentioned above, it is most preferable to use the packed state of the sintered ore packed bed for charging as the input condition (a). However, even if only some of the conditions of the input condition (a) are the same as the packed state of the sintered ore packed bed for charging (a), it is possible to reduce the influence of the high-temperature property-related conditions of the target blast furnace on the reduction rate Rs at the start of fusion. * For example, by using the harmonic mean diameter obtained from the particle size distribution of the sintered ore to be charged, which is the target of particle size distribution adjustment, as the harmonic mean diameter in (a) used as the input condition, or by using the void fraction obtained from the particle size distribution of the sintered ore to be charged, as the void fraction in (a) used as the input condition, the influence of the high temperature property related conditions of the target blast furnace can be reflected in the reduction rate at the start of fusion Rs * can be reflected in.

[0050] Based on the reduction rate, contraction rate and pressure loss estimated using these input conditions, the reduction rate Rs at the start of fusion of the sinter packed bed for investigation was calculated. * As a specific estimation method, the reduction rate, contraction rate, and pressure loss are estimated for each calculation cell when a predetermined time t (the calculation period Δt multiplied by the number of estimations) from the reference time has elapsed, and the estimation is repeated until the pressure loss in the sintered ore packed bed for consideration reaches a predetermined value. Then, the average reduction rate of the sintered ore packed bed for consideration when the estimated pressure loss reaches the predetermined value is defined as the reduction rate at the start of fusion Rs *The reference time can be when the sintered ore packed bed is formed in the blast furnace (in other words, immediately after the sintered ore is charged) or when the sintered ore packed bed falls to the temperature range where reduction starts. The temperature where reduction starts can be, for example, 500°C.

[0051] (Input conditions) The input conditions used for estimating the reduction ratio, the contraction ratio, and the pressure loss are conditions used to estimate the reduction ratio, the contraction ratio, and the pressure loss, and are a concept that includes both conditions that are directly input into these estimation formulas and conditions for obtaining the conditions that are input into the estimation formulas.

[0052] Specific input conditions are shown in FIG. 1. First, among the input conditions shown in FIG. 1, (a) the packing state of the sintered ore packed bed will be described. The packing state indicates the initial packing state of the sintered ore contained in the sintered ore packed bed (i.e., the packing state immediately after the sintered ore constituting the sintered ore packed bed is charged into the blast furnace). Specifically, the packing state includes the apparent density of the sintered ore, the harmonic mean particle size of the sintered ore, the shape factor of the sintered ore, the chemical composition of the sintered ore, the softening and shrinkage parameter, the initial blending ratio indicating the volume ratio of the sintered ore (i.e., 100%), the initial void fraction of the sintered ore packed bed, and the initial bed height of the sintered ore packed bed. In this specification, the softening and shrinkage parameter refers to the constant η0, coefficients c1 to c6, coefficients α, β, and constant γ used in the estimation formula described later.

[0053] For each of the conditions in (a) above, the results obtained by forming a sintered ore packed bed for investigation in a test device or the packed state of the sintered ore packed bed for investigation calculated based on a known mathematical model can be used. For example, the initial porosity of the sintered ore packed bed for investigation can be obtained from the particle size distribution (particle size, etc.) by using the formula (22) described later in Non-Patent Document 2.

[0054] Next, among the input conditions shown in Figure 1, (b) the temperature of the sintered ore packed bed, (c) the composition and flow rate of the reducing gas flowing through the sintered ore packed bed, (d) the load on the sintered ore packed bed, and (e) the pressure of the reducing gas will be explained. Here, the temperature of the sintered ore packed bed refers to the temperature of the sintered ore packed bed under consideration (hereinafter also referred to as the "sintered ore packed bed to be estimated") for which the reduction rate, shrinkage rate, and pressure loss are to be estimated. The composition of the reducing gas refers to the composition of the reducing gas flowing through the sintered ore packed bed to be estimated. The flow rate of the reducing gas refers to the flow rate of the reducing gas flowing through the sintered ore packed bed to be estimated. The load on the sintered ore packed bed refers to the load on the sintered ore packed bed to be estimated. The pressure of the reducing gas refers to the pressure of the reducing gas flowing through the sintered ore packed bed to be estimated.

[0055] These input conditions may change as the sintered ore packed bed descends through the blast furnace. Therefore, it is preferable to prepare in advance information that indicates changes in these input conditions as the sintered ore packed bed to be studied descends through the blast furnace. When estimating the reduction degree, the contraction degree, and the pressure loss, values ​​obtained when a predetermined time t has elapsed from the reference time (hereinafter simply referred to as "when the predetermined time t has elapsed") are selected from the information and used as input conditions.

[0056] Specific information includes a temperature rise pattern showing the temperature change of the sintered ore packed bed under consideration over time, a load pattern showing the change in load according to the temperature change of the sintered ore packed bed under consideration, a flow rate pattern showing the change in gas flow rate according to the temperature change of the sintered ore packed bed under consideration, a composition pattern showing the change in reducing gas composition according to the temperature change of the sintered ore packed bed under consideration, and a pressure pattern showing the change in reducing gas pressure according to the elapsed time.

[0057] This information can be obtained from past operational results or publicly known information. As an example, the temperature rise pattern can be the temperature rise pattern shown in Figure 2a, the load pattern can be the load pattern shown in Figure 2b, the flow rate pattern can be the flow rate pattern shown in Figure 2c, the composition pattern can be the composition pattern shown in Figure 2d or Figure 2e, and the pressure pattern can be the pressure pattern shown in Figure 2f.

[0058] 1, the input conditions (b) to (d) may be general blast furnace conditions different from the blast furnace (target blast furnace) into which the sintered ore to be charged, which is the target of particle size distribution adjustment, is charged. However, it is preferable to use the conditions of the target blast furnace. That is, in the adjustment method of this embodiment, the input conditions (b) to (d) are calculated by using one or more of the following conditions: (b) the temperature of the sintered ore packed bed to be charged, (c) the composition and flow rate of the reducing gas flowing into the sintered ore packed bed to be charged, and (d) the load applied to the sintered ore packed bed to be charged. * It is preferable to calculate Rs by using the conditions of the sintered ore packed bed for charging in the target blast furnace in at least one of the above (b) to (d). * Reduction rate Rs at the start of fusion calculated by the estimation model * Therefore, the reduction ratio at the start of fusion Rs, which more accurately evaluates the high-temperature properties of the sintered ore charged in the target blast furnace, is used to adjust the particle size distribution. * can be obtained.

[0059] Next, a method for estimating the reduction ratio, contraction ratio, and pressure loss using the above-mentioned input conditions will be explained with reference to Figure 3. Figure 3 shows the reduction ratio Rs at the start of fusion. * 10 is a flowchart showing a procedure for estimating

[0060] (Calculation grid settings) In the processing of step S101 (computational grid setting step), a computational grid is set to divide one layer of the sinter packed bed to be investigated in the blast furnace into any number of regions aligned in the bed height direction. The regions (computational cells) divided by the computational grid are regions for which the reduction degree, contraction degree, and pressure loss are to be estimated, and the filling state is set as an input condition for each computational cell, and the reduction degree, contraction degree, and pressure loss are output.

[0061] (Reduction behavior of ore) In the processing of step S102 (reduction rate calculation step), the reduction rate of the sintered ore for study contained in the sintered ore for study packed bed after a predetermined time t has elapsed is calculated for each calculation cell.

[0062] The reduction rate in the calculation cell after a predetermined time t has elapsed can be calculated based on the three-interface unreacted core model described in Non-Patent Document 3, for example, and can be estimated using the following equation (5).

[0063]

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[0064] In the above formula (5), the radius r to the s / t interface (s / t) can be calculated by the following formula (6).

[0065]

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[0066] Here, the composition of the reducing gas may change while passing through the sintered ore packed bed. Therefore, reducing gases of different compositions may pass through a region of the sintered ore packed bed located upstream of the flow of the reducing gas and a region of the sintered ore packed bed located downstream of the flow of the reducing gas. Therefore, when estimating the reduction rate for the sintered ore packed bed under consideration, the calculation cell located upstream of the flow of the reducing gas may estimate the change in the composition of the reducing gas together with the reduction rate, and the calculation cell located downstream of the flow of the reducing gas may estimate the reduction rate using the composition of the reducing gas after the change in composition.

[0067] To estimate the reduction rate taking into account changes in the composition of the reducing gas, for example, Non-Patent Document 3 can be used. One-dimensional unsteady reaction rate analysis can be cited as a preferred method for determining the reduction rate taking into account changes in the composition of the reducing gas. One-dimensional unsteady reaction rate analysis is described in Non-Patent Document 4, for example.

[0068] Note that the method for estimating the compositional change of the reducing gas in the sintered ore packed bed to determine the reduction rate of the sintered ore packed bed is not limited to one-dimensional unsteady reaction rate analysis. Other methods for reduction reaction rate analysis, such as two-dimensional or three-dimensional unsteady reaction rate analysis, may also be used. Furthermore, the method for determining the reduction reaction rate of the sintered ore to estimate the reduction rate of each calculation cell is not limited to the three-interface unreacted nucleus model. Other reduction reaction models that can be used include a multi-stage reaction zone model and a grain model. Furthermore, even when one-dimensional unsteady reaction rate analysis or a three-interface unreacted nucleus model is used, the applicable chemical reaction rate equations are not limited to those described above, and any chemical reaction rate equation disclosed in a publicly known document may be used as appropriate.

[0069] (Shrinkage behavior of sintered ore packed bed) In the process of step S103 (shrinkage rate calculation step), the shrinkage rate of the sintered ore packed bed to be examined after a predetermined time t has elapsed is calculated for each calculation cell. The shrinkage rate of each calculation cell after the predetermined time t has elapsed can be expressed as the time integral of the shrinkage rate of each calculation cell. Therefore, by calculating the shrinkage rate from when the sintered ore packed bed to be examined is formed in the blast furnace until the predetermined time t has elapsed, the shrinkage rate of each calculation cell after the predetermined time t has elapsed can be estimated. Note that the sintered ore packed bed does not shrink in the temperature range up to when the reduction of the sintered ore starts, so the shrinkage rate may also be calculated by time integrating the shrinkage rate from when the reduction of the sintered ore starts until the predetermined time t has elapsed.

[0070] The shrinkage behavior of the sintered ore packed bed is governed by different factors in the two temperature regions (region I and region II). Therefore, the estimation formula for the shrinkage rate can be determined separately for each of these temperature regions. When the temperature of the sintered ore packed bed to be examined is within the range of region I, the estimation formula for the shrinkage rate of each calculation cell can be expressed by the formulas (7) to (8) described later. When the temperature of the sintered ore packed bed to be examined is within the range of region II, the estimation formula for the shrinkage rate of each calculation cell can be expressed by the formulas (9) to (13) described later. The boundary temperature separating region I and region II is the temperature at which the shrinkage rate of the sintered ore packed bed to be examined is at its maximum value, and the temperature region lower than the boundary temperature is region I, and the temperature region higher than the boundary temperature is region II.

[0071] In region I, the shrinkage rate of each calculation cell can be calculated using the following formula (7): As shown in formula (7), in region I, the shrinkage rate of the calculation cell is proportional to the load applied to the sintered ore packed bed and inversely proportional to the apparent softening viscosity (shrinkage resistance of the charge).

[0072]

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[0073] The apparent softening viscosity η in the above formula (7) can be calculated by the following formula (8).

[0074]

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[0075] In formula (8), the constant η0 and the coefficient c1 can be calculated in advance based on formula (8) using the apparent softening viscosity η calculated by a load-softening test. The load-softening test simulates the temperature-rise reduction behavior of a sintered ore packed bed in a blast furnace, and the load-softening test described in Non-Patent Document 1 can be used.

[0076] In Region II, the shrinkage rate of each calculation cell can be calculated using the following formula (9). As shown in the following formula (9), in Region II, the shrinkage rate is proportional to the melt generation rate. Furthermore, as shown in the following formula (11), the coefficient β decreases as the volume fraction of metallic iron in the sintered ore packed bed increases. As can be seen from this, in Region II, the main controlling factors that determine the shrinkage rate are the melt generation behavior and the aggregate effect of the generated metallic iron (the effect of metallic iron generated by the reduction of sintered ore inhibiting the shrinkage of the sintered ore packed bed).

[0077]

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[0078] In the above equation (9), the initial volume V 0.SP is the initial volume of each calculation cell before shrinkage. Also, the initial mass of the sintered ore under consideration, M SP is the initial volume V of the i-th calculation cell 0.SP and the volume ratio of the sintered ore under consideration in the i-th calculation cell (1-ε 0i ) and the apparent density.

[0079] The amount of melt generated in the above formula (9) V liq can be calculated by the following formula (10).

[0080]

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[0081] In the above formula (10), the coefficients c2, c3, and c4 can be calculated in advance by thermodynamic equilibrium calculation (for example, by using the thermodynamic equilibrium calculation software Factsage). Specifically, the temperature T and reduction rate R i When the amount of generated V is changed liq If we calculate the thermodynamic equilibrium using i and the amount produced V liq The constants c2, c3, and c4 can be determined so that this relationship matches the above equation (10).

[0082] The coefficient β in the above equation (9) can be calculated by the following equation (11).

[0083]

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[0084] In the above formula (11), the volume fraction X of metallic iron Fe can be calculated by the following formula (12).

[0085]

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[0086] In the above formula (12), the volume V of metallic iron Fe can be calculated by the following formula (13).

[0087]

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[0088] In the above formula (13), the initial proportion of the total iron amount, T.Fe, can be determined in advance.

[0089] The η0 and c1 to c6 used in the above formulas (8), (10), and (11) can be determined depending on the properties of the sintered ore under study, such as the composition and pore structure. These coefficients do not change unless the type of sintered ore under study is changed, and they do not change with changes in the packing state of the sintered ore under study or the conditions related to the reducing gas.

[0090] η0 and c1 to c6 can be selected, for example, from the following ranges. η0=6.0×10 -17 ~3.0×10 3 c1=1.5×10 4 ~9.0×10 4 c2=5.0×10 -8 ~1.5×10 -6 c3=0.0~1.5×10 -4 c4=-1.0×10 -3 ~-6.0×10 -5 c5=-40~0.0 c6=0.1~10

[0091] As described above, the shrinkage rate of each computational cell is expressed as the time integral of the shrinkage rate estimated by the above formula (7) or (9). Therefore, the time integral of the shrinkage rate estimated by the above formula (7) or (9) becomes the shrinkage rate of each computational cell.

[0092] (Increase in pressure drop due to bed contraction) In the process of step S104 (pressure loss calculation step), the pressure loss in the sintered ore packed bed under consideration after a predetermined time t has elapsed is calculated for each calculation cell. The pressure loss calculated in step S104 may be the pressure loss [Pa] occurring in each calculation cell itself, or may be the pressure loss per unit length [Pa / m]. The pressure loss per unit length can be calculated based on the following formula (14) as the Ergun formula.

[0093]

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[0094] In the above equation (14), the effective diameter φd of the sintered ore under investigation after a predetermined time t has elapsed can be calculated from equation (20) described below. The superficial velocity U can be calculated by dividing the flow rate of the reducing gas after the predetermined time t has elapsed by the cross-sectional area of ​​the calculation cell perpendicular to the direction of the reducing gas flow, and for example, the flow rate pattern described above can be used. The viscosity μ and density ρ of the reducing gas can be calculated from known functions defined by the temperature and reducing gas composition after the predetermined time t has elapsed, and for example, the temperature rise pattern and composition pattern described above can be used.

[0095] The porosity ε in the above formula (14) can be calculated by the following formula (15).

[0096]

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[0097] In Equation (15), the coefficient α represents the ratio of the void volume reduction to the total volume reduction during layer shrinkage, and depends on the closed pore volume and thermoplasticity of the sintered ore under consideration. While there are no particular limitations on how the coefficient α is calculated, an example of how it is calculated using an X-ray CT image analysis method is described below.

[0098] Figure 4 shows an overview of the X-ray CT image analysis method. The crucible is filled with sintered ore, and the sintered ore is reduced while a reducing gas is circulating. A horizontal cross-sectional image of the crucible obtained by X-ray CT imaging identifies the region where only the sintered ore is present. A predetermined number of images are extracted from this region at equal intervals in the vertical direction, and the porosity and apparent particle size are calculated using each image. Specifically, the original image obtained by X-ray CT imaging is binarized, and a masking process is used to create an image in which only the sintered ore particles are extracted (image (a) in Figure 4)) and an image in which the inside of the graphite crucible is filled in white (image (b) in Figure 4). For both images, the number of pixels in the black areas, the white areas, and the surrounding pixels are counted, and the porosity of the sintered ore packed bed and the apparent particle size of the sintered ore are calculated using equations (16) to (19). Note that the particle size calculated from the horizontal cross-sectional image is π / 4 times the actual size if the particles are assumed to be spherical, so this can be corrected.

[0099]

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[0100] The above-mentioned image analysis is performed on a plurality of sintered ore packed beds with different shrinkage rates, and the porosity of the sintered ore packed bed and the apparent particle size of the sintered ore for each shrinkage rate are determined (hereinafter referred to as "measured values"). Furthermore, the initial values ​​of the porosity of the sintered ore packed bed and the apparent particle size of the sintered ore for each shrinkage rate (hereinafter referred to as "initial values") are determined using X-ray CT images of the sintered ore before it softens and shrinks. For each measured value of the porosity of the sintered ore packed bed obtained based on the analysis results of the X-ray CT images, the value of α that satisfies the above formula (15) is determined using the initial value of the porosity of the sintered ore packed bed obtained based on the analysis results of the X-ray CT images, and α is approximated by a linear equation of the shrinkage rate Sr.

[0101] In the above-described method, α is a function of the shrinkage rate, but in a simple analysis, it may be a fixed value depending on the brand of sintered ore under consideration. The coefficient α can be selected, for example, from the following range: α=0~1

[0102] Similarly, it is preferable to approximate each measured apparent particle size value obtained based on the analysis results of the X-ray CT image as a function of the shrinkage rate Sr. The apparent particle size approximated as a function of the shrinkage rate Sr can be used as the effective diameter φd of the sintered ore under study in the above formula (14). The effective diameter φd in the above formula (14) can be expressed by the following formula (20). Note that in a simple analysis, it is not necessary to consider the change in apparent particle size due to layer shrinkage. In other words, in a simple analysis, the effective diameter φd of the sintered ore under study in the above formula (14) may be regarded as the initial effective diameter (φd) of the sintered ore under study.

[0103]

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[0104] In the above formula (20), the value of the constant γ that satisfies the above formula (20) can be determined in advance for each measured value of the apparent particle size of the sintered ore packed bed for investigation, which is determined based on the analysis results of the X-ray CT image. When the value of the constant γ is determined in advance, the effective diameter (φd) and the average shrinkage rate Sr in the above formula (20) can be calculated. i The actual measured value of the apparent particle size of the sintered ore packed bed to be investigated, which is obtained based on the analysis results of the X-ray CT image, and the shrinkage rate at the time when the actual measured value was obtained can be used as the initial effective diameter (φd)0 in the above formula (20). The initial value of the apparent particle size can be used as the initial effective diameter (φd)0.

[0105] The method for calculating the pressure drop is not limited to the method using the above Ergun equation (14). For example, other pressure drop estimation equations for packed beds can also be applied, such as the method disclosed in Non-Patent Document 5 in which the coefficient of the inertia term in the Ergun equation is corrected as a function of the contraction rate, or the estimation equation based on the orifice model disclosed in Non-Patent Document 6. The pressure drop (Pa) occurring in each calculation cell can be obtained by multiplying the pressure drop per unit length (Pa / m) calculated based on the above equation (14) by the length of the calculation cell in the bed height direction.

[0106] (Estimation of high temperature properties) In the process of step S105, it is determined whether the pressure loss calculated in step S104 has reached a predetermined value. The predetermined value of the pressure loss is the pressure loss when the ore cohesive layer is formed, or the gradient of the pressure loss, and can be, for example, 200 × 9.8 Pa or 50 kPa / m. The determination in step S105 is made based on whether the pressure loss of the entire sintered ore packed bed to be examined, or the average value of the gradient of the pressure loss of the sintered ore packed bed to be examined, has reached a predetermined value. If the pressure loss has reached the predetermined value, the process of step S106, which will be described later, is performed. If the pressure loss has not reached the predetermined value, the process returns to the process of step S102, and the processes of steps S102 to S104 are repeated. In the repeated processes of steps S102 to S104, the reduction rate, contraction rate, and pressure loss are estimated for each calculation cell when a calculation period Δt has elapsed.

[0107] In step S106 (high temperature property estimation step), the reduction rate Rs * Ask for.

[0108] Rs * indicates the reduction rate of the sintered ore packed bed (ore layer) under consideration when the pressure drop occurring in the sintered ore packed bed (ore layer) rises to a predetermined value. Therefore, the average value of the reduction rates of each calculation cell when the pressure drop calculated in the process of step S104 indicates the predetermined value (i.e., the reduction rates calculated in step S102) is the reduction rate at the start of fusion Rs * The fusion start temperature Ts * is the temperature reached by the sintered ore packed bed when the pressure loss of the sintered ore packed bed rises to a predetermined value, so the average value of the temperature (input condition) of each calculation cell of the sintered ore packed bed when the pressure loss obtained in the processing of step S104 indicates the predetermined value is the fusion start temperature Ts * is calculated as follows.

[0109] The above-mentioned Rs. * The reduction rate Rs of the sintered ore packed bed at the start of fusion was calculated using the estimation model. * The harmonic mean particle size Dp corresponds to the initial particle size d0 of the sintered ore under investigation.

[0110] Rs* As mentioned above, the -Dp curve is * For the estimation model, multiple input conditions with different harmonic mean particle diameters Dp were input and the reduction rate Rs at the start of fusion of the sinter packed bed for investigation was calculated for each input condition. * Calculate the reduction rate at the start of fusion Rs * and the reduction rate at the start of fusion Rs * It can be obtained by plotting the harmonic mean particle diameter Dp used in the calculation on a graph.

[0111] Rs * In the -Dp curve, the reduction rate at the start of fusion Rs * can be approximated by a linear or quadratic expression of the harmonic mean particle diameter Dp. * The Rs-Dp curves are obtained as shown in Fig. 6c, for example, when the initial porosity ε0 is 0.38 or 0.40. * The -Dp curve is shown, and can be expressed by the following formula (21) based on the initial porosity ε0 = 0.40.

[0112]

number

[0113] Rs * The range of the harmonic mean particle diameter Dp for obtaining the -Dp curve, i.e., the reduction ratio Rs at the start of fusion * The range of the harmonic mean particle diameter Dp for calculating or measuring the particle size distribution may be any range that includes the harmonic mean particle diameter Dp of the sintered ore to be charged, which is the target of particle size distribution adjustment, and can be appropriately set within a necessary range based on the range that can be adopted in actual operation. Depending on the range of the harmonic mean particle diameter Dp, as shown in Figure 6c, the reduction ratio at the start of fusion Rs * Rs *-Dp curves may be obtained, but are not limited to, simple increasing or monotonically decreasing Rs * A -Dp curve may be obtained.

[0114] As mentioned above, even if the porosity and other properties are different between the charged sinter and the sinter under investigation, the reduction ratio Rs at the start of fusion with respect to the change in the harmonic mean particle diameter Dp is * The response of Rs can be considered similar. * By using the -Dp curve, the reduction ratio Rs at the start of fusion for the sintered ore to be charged, which is the target for adjusting the particle size distribution, can be calculated. * The change in ΔRs * (Reduction ratio Rs at the start of fusion for sintered ore after particle size distribution adjustment) * and the reduction ratio Rs at the start of fusion for the sintered ore before particle size distribution adjustment * In this specification, the reduction ratio Rs of sintered ore at the start of fusion can be estimated. * is the reduction rate Rs of the sintered ore packed bed at the start of fusion. * Refers to...

[0115] In the adjustment method of this embodiment, the reference value S is Rs * -Reduction rate Rs at the start of fusion in the Dp curve * is the harmonic mean particle diameter Dp at which the maximum value is reached. * -Reduction rate Rs at the start of fusion in the Dp curve * It is sufficient if it is the maximum value of Rs, and it does not necessarily have to be the maximum value. * From the viewpoint of further increasing the maximum value, it is preferable that the maximum value is a local maximum value.

[0116] Here, between the charged sinter and the sinter under investigation, the reduction ratio Rs at the start of fusion with respect to the change in the harmonic mean particle diameter Dp * The response of Rs can be considered to be similar, and the target for adjusting the particle size distribution, the harmonic mean particle size Dp of the sintered ore to be charged, is to be brought closer to Rs. * -Reduction rate Rs at the start of fusion in the Dp curve *is the harmonic mean particle diameter Dp (i.e., the reference value S) at which the particle size distribution is adjusted. Therefore, the closer the harmonic mean particle diameter Dp of the sintered ore to be charged, which is the target of particle size distribution adjustment, is to the reference value S, the higher the reduction ratio Rs at the start of fusion for the sintered ore to be charged, which is the target of particle size distribution adjustment. * If there is no change in the blending ratio of the sintered ore contained in the ore layer, the reduction ratio Rs * As the reduction rate Rs increases, the reduction rate Rs of the ore layer formed using the sintered ore for charging increases. * Therefore, according to the present embodiment in which the particle size distribution of the sintered ore to be charged is adjusted to satisfy the first condition, the reduction rate Rs at the start of fusion for the sintered ore to be charged, which is the target of the particle size distribution adjustment, increases. * As a result, the reduction rate Rs of the ore layer formed using the sinter can be increased. * can rise.

[0117] The reduction rate at the start of fusion of the ore layer, Rs * is the reduction rate Rs of the packed layer (the ore layer consisting of one type of ore) at the start of fusion for each type of ore material that forms the ore layer. * The reduction rate Rs at the start of fusion of the packed bed was calculated. * can be calculated by taking a weighted average according to the blending ratio [mass%] of the ore raw material forming the packed layer in the ore layer. Here, for each type of ore raw material forming the ore layer, the reduction rate Rs * To find the above, use the Rs * Specifically, by using the same or similar conditions as the packed state of the packed bed as each of the conditions in (a) used as input conditions, the reduction rate Rs of each packed bed at the start of fusion can be calculated. * can be obtained.

[0118] In addition, the reduction rate at the start of fusion Rs * As mentioned above, Rs represents the reduction rate when the ore melting layer is formed. *An increase in Rs means that the reduction rate increases when the ore raw material softens (and fuses) to form a fusion layer. In other words, the reduction rate by indirect reduction (exothermic reaction) until the fusion layer is formed increases, and the reduction rate by direct reduction (endothermic reaction) in the lower part of the furnace decreases. Therefore, the reduction rate Rs at the start of fusion of the ore layer * If R increases, the amount of heat absorbed in the lower part of the furnace decreases (the amount of endothermic reaction decreases), and dripping of molten iron is promoted. As a result, the area of ​​the cohesive zone shrinks, and the furnace gas (reducing gas) can easily pass through the ore cohesive layer. Therefore, the reduction rate Rs at the start of fusion for the sintered ore to be charged, which is the target of particle size distribution adjustment, * According to the adjustment method of this embodiment, the reduction rate Rs of the ore layer formed using the sintered ore can be increased. * This increases the reduction efficiency and permeability in the furnace, allowing the reducing agent rate to be reduced, and also reduces the coke rate and increases the productivity.

[0119] The adjusting method of this embodiment described above only requires adjusting the particle size distribution of the sintered ore to be charged so as to satisfy the first condition, and other conditions are not particularly limited.

[0120] In the adjustment method of this embodiment, the reduction rate Rs at the start of fusion for the sintered ore to be charged, which is the target of particle size distribution adjustment, * From the viewpoint of further increasing the particle size distribution, it is preferable to adjust the particle size distribution so as to satisfy the following second condition in addition to the first condition.

[0121] The second condition is that the initial porosity ε0 of the sintered ore packed bed for charging increases by adjusting the particle size distribution compared to when the sintered ore packed bed for charging is formed using the sintered ore whose particle size distribution is to be adjusted. In other words, the second condition is that the initial porosity ε0 of the sintered ore packed bed for charging is higher when the sintered ore packed bed for charging is formed using the sintered ore after particle size distribution adjustment than when the sintered ore packed bed for charging is formed using the sintered ore before particle size distribution adjustment. Note that the initial porosity ε0 refers to the porosity immediately after the sintered ore packed bed is formed (the porosity of the sintered ore packed bed immediately after the sintered ore is charged into the blast furnace).

[0122] Here, a high initial void ratio ε0 does not only mean that the initial void ratio ε0 of the sintered ore packed bed actually formed in a blast furnace or an experimental device simulating a blast furnace (for example, the high-temperature property test device shown in Non-Patent Document 1) is high, but also includes a concept that the initial void ratio ε0 of the sintered ore packed bed predicted from the particle size distribution of the sintered ore is high. The method for predicting the initial void ratio ε0 of the sintered ore packed bed from the particle size distribution of the sintered ore is not particularly limited, but for example, a prediction method based on the following formula (22) described in Non-Patent Document 2 can be used.

[0123]

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[0124] In the adjustment method of this embodiment, to adjust the particle size distribution so as to satisfy the first and second conditions, for example, a method can be used in which a particle size distribution that satisfies the first and second conditions is designed, and the particle size distribution of the sintered ore to be charged, the particle size distribution of which is to be adjusted, is made to match the designed particle size distribution.

[0125] To design a particle size distribution that satisfies the first and second conditions, for example, the above formula (22) can be used. Specifically, first, the initial void fraction ε0 when a sintered ore packed bed is formed using the sintered ore whose particle size distribution is to be adjusted (hereinafter also referred to as the "initial void fraction ε0 before adjustment") is calculated based on the above formula (22). Next, a particle size distribution is tentatively designed so that the harmonic mean particle diameter Dp of the sintered ore whose particle size distribution is to be adjusted approaches the reference value S, and the initial void fraction ε0 when a sintered ore packed bed is formed using the sintered ore whose particle size distribution has been tentatively designed (hereinafter also referred to as the "tentatively designed initial void fraction ε0") is calculated based on the above formula (22). Finally, from among the provisionally designed particle size distributions, a particle size distribution in which the provisionally designed initial porosity ε0 is higher than the pre-adjustment initial porosity ε0 is identified, and the identified particle size distribution (provisionally designed particle size distribution) is determined (designed) as a particle size distribution that satisfies the first condition and the second condition.

[0126] In the design of the particle size distribution described above, the particle size distribution is tentatively designed, but this tentative design is not necessarily required. The initial void fraction ε of the sintered ore packed bed can be increased by reducing the proportion of coarse sintered ore exceeding a predetermined particle size (e.g., 50 mm) or by reducing the proportion of fine sintered ore less than a predetermined particle size (e.g., 5 mm). By identifying a means for increasing the initial void fraction ε in advance and using this means to design a particle size distribution in which the harmonic mean particle size Dp of the sintered ore to be charged approaches the reference value S, the designed particle size distribution will have an increased initial void fraction ε as the harmonic mean particle size Dp approaches the reference value S. In other words, a particle size distribution that satisfies the first and second conditions can be designed without tentatively designing the particle size distribution.

[0127] The method for adjusting the particle size distribution of the sintered ore to be charged so as to satisfy the first and second conditions is not limited to the above-mentioned method, and the particle size distribution of the sintered ore to be charged may be adjusted without designing the particle size distribution. For example, if the particle size distribution is adjusted so that the harmonic mean particle size Dp of the sintered ore to be charged approaches the reference value S using a means that can increase the initial porosity ε0, the adjustment of the particle size distribution satisfies the first and second conditions.

[0128] Reduction rate Rs of the sintered ore packed bed at the start of fusion * increases as the initial void ratio ε0 of the sintered ore packed bed for charging increases. Therefore, according to the present embodiment in which the particle size distribution of the sintered ore for charging is adjusted to satisfy the first and second conditions, the reduction ratio Rs at the start of fusion for the sintered ore for charging, which is the target of adjusting the particle size distribution, is lower than when the particle size distribution is adjusted to satisfy only the first condition. * can be further increased.

[0129] In the adjustment method of this embodiment, Rs * -Reduction rate Rs at the start of fusion in the Dp curve * When the harmonic mean particle diameter Dp at which the value of σ is maximized is defined as the reference value S, it is preferable to adjust the particle size distribution so as to satisfy the following third or fourth condition in addition to the first and second conditions.

[0130] The third condition is that when the harmonic mean particle size Dp of the sintered ore to be charged, which is the target of particle size distribution adjustment, exceeds the reference value S, the harmonic mean particle size Dp of the sintered ore to be charged after adjusting the particle size distribution a The fourth condition is that when the harmonic mean particle diameter Dp of the sintered ore to be charged, which is the target of particle size distribution adjustment, is less than the reference value S, the harmonic mean particle diameter Dp of the sintered ore to be charged after adjusting the particle size distribution must be equal to or greater than the reference value S. a The condition is that the value must be less than the reference value S.

[0131] In the adjustment method of this embodiment, when the particle size distribution is adjusted to satisfy the third and fourth conditions in addition to the first and second conditions, the reduction rate Rs at the start of fusion for the sintered ore to be charged, which is the target of particle size distribution adjustment, is calculated based on the formulas (2) and (3) described below. * The change in ΔRs * (Reduction ratio Rs at the start of fusion for sintered ore after particle size distribution adjustment) * and the reduction ratio Rs at the start of fusion for the sintered ore before particle size distribution adjustment * (difference between the

[0132] When the particle size distribution is adjusted to satisfy the third condition in addition to the first and second conditions, the reduction rate at the start of fusion Rs for the sintered ore to be charged, which is the target of the particle size distribution adjustment, is * The change in ΔRs * (Change in particle size distribution before and after adjustment ΔRs * ) can be estimated using the following equation (2):

[0133]

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[0134] The change rate C1 in the above formula (2) is the reduction rate Rs at the start of fusion in the range where the harmonic mean particle diameter Dp is equal to or greater than the reference value S. * is the value obtained by dividing the change in the harmonic mean particle diameter Dp by the change in the harmonic mean particle diameter Dp. * -Dp curve, the slope of which corresponds to the slope in the range where the harmonic mean particle diameter Dp is equal to or greater than the reference value S. Therefore, the change rate C1 includes the Rs * The slope of the Rs -Dp curve (the slope in the range where the harmonic mean particle diameter Dp is equal to or greater than the reference value S) can be used. * When the slope of the -Dp curve changes, the average value of the slope may be used as the rate of change C1.

[0135] Here, the rate of change C1 is one Rs * The slope of the -Dp curve may be used, but two or more Rs obtained using different initial porosities ε0 * It is preferable to use the average value of the slope of the -Dp curve, and two Rs obtained using two different initial porosities ε0 for the sintered ore to be charged before and after particle size distribution adjustment. * It is more preferable to use the average value of the slope of the -Dp curve. * When the initial porosity ε0 input to the estimation model is different, the obtained Rs * The slopes of the -Dp curves may differ from each other. Therefore, two or more Rs obtained by inputting different initial porosities ε0 as the rate of change C1 are used. * By using the average value of the slope of the -Dp curve, the change ΔRs * can be predicted more accurately.

[0136] The change rate D1 in the above formula (2) is the reduction rate Rs at the start of fusion. * This value is calculated by dividing the change in Rs by the change in the initial porosity ε0. For example, two Rs obtained using different initial porosities ε0 are * -Dp curve. * The -Dp curve shows two Rs obtained using two different initial porosities ε0 for the charged sinter before and after particle size distribution adjustment. *It is preferable to use the -Dp curve. Specifically, two Rs * The difference between the initial porosity ε0 used to obtain the -Dp curve (hereinafter also referred to as the "initial porosity ε0 difference") and the two Rs * -Reduction rate Rs at the start of fusion in the Dp curve * The difference (hereinafter referred to as "Rs * The difference (also called "difference") is calculated and the calculated Rs * It can be calculated by dividing the difference by the difference in initial porosity ε0. Here, Rs * The difference is Rs corresponding to any harmonic mean particle size Dp. * is the difference between two or more Rs corresponding to two or more harmonic particle sizes Dp. * The average value of the difference may be used.

[0137] The rate of change D1 in the above formula (2) is calculated by multiplying the Rs * -You can also find it from the Dp curve, but Rs * -ε0 may be the slope of the curve. Here, Rs * The -ε0 curve is obtained by applying the Rs * Input each into the estimation model and calculate the reduction rate at the start of fusion Rs * and the reduction rate at the start of fusion Rs * This is a curve obtained by plotting the initial porosity ε0 used in the calculation of Rs * When the slope of the -ε0 curve changes, the average value of the slope may be used as the rate of change D1. * The slope of the -ε0 curve may be used, and two or more Rs obtained by inputting different harmonic mean particle diameters Dp may be used. * The average value of the slope of the -ε0 curve may also be used.

[0138] The change rate C1 and the change rate D1 in the above formula (2) are Rs * These values ​​cannot be determined uniquely as they may differ depending on the input conditions of the estimation model and the reference value S, but for example, the reference value S can be set to 12 mm, C1 to -1.2, and D1 to 150.

[0139] On the other hand, when the particle size distribution is adjusted to satisfy the fourth condition in addition to the first and second conditions, the reduction ratio Rs at the start of fusion for the sintered ore to be charged, which is the target of the particle size distribution adjustment, is * The change in ΔRs * (Change in particle size distribution before and after adjustment ΔRs * ) can be calculated using the following formula (3).

[0140]

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[0141] The change rate C2 in the above formula (3) is the reduction rate Rs at the start of fusion when the harmonic mean particle diameter Dp is in the range of not more than the reference value S. * is the value obtained by dividing the change in the harmonic mean particle diameter Dp by the change in the harmonic mean particle diameter Dp. * -Dp curve, the gradient of the harmonic mean particle diameter Dp is in the range of the reference value S or less. Therefore, the change rate C2 is * The slope of the Rs -Dp curve (the slope within the range where the harmonic mean particle diameter Dp is equal to or less than the reference value S) can be used. * If the slope of the -Dp curve changes, the average value of the slope may be used as the rate of change C2.

[0142] The rate of change C2 is one Rs* The slope of the -Dp curve may be used, but the change ΔRs * From the viewpoint of more accurate prediction, two or more Rs obtained using different initial porosities ε0 * It is preferable to use the average value of the slope of the -Dp curve, and two Rs obtained using two different initial porosities ε0 for the sintered ore to be charged before and after particle size distribution adjustment. * It is more preferable to use the average value of the slope of the -Dp curve.

[0143] The rate of change D2 in the above formula (3) is synonymous with the rate of change D1 in the above formula (2), and is calculated in the same way as the rate of change D1. Therefore, a description of the rate of change D2 will be omitted.

[0144] The change rate C2 and the change rate D2 in the above formula (3) are Rs * These values ​​cannot be determined uniquely as they may differ depending on the input conditions of the estimation model and the reference value S, but for example, the reference value S can be set to 12 mm, C2 to 1.2, and D2 to 150.

[0145] As explained above, the change amount ΔRs is calculated using equations (2) and (3). * In an embodiment that takes this into consideration, the third and fourth conditions must be satisfied. However, the change amount ΔRs * If the above is not taken into consideration, it is not necessary to satisfy the third condition or the fourth condition, and a harmonic mean particle diameter Dp exceeding the reference value S may become less than the reference value S by adjusting the particle size distribution, or a harmonic mean particle diameter Dp less than the reference value S may exceed the reference value S by adjusting the particle size distribution. In addition, when a harmonic mean particle diameter Dp exceeding the reference value S becomes less than the reference value S by adjusting the particle size distribution, or a harmonic mean particle diameter Dp less than the reference value S exceeds the reference value S by adjusting the particle size distribution, the amount of change ΔRs can be calculated by using, for example, the quadratic formula of the above-mentioned formula (21). * It is possible to consider

[0146] In the adjustment method of this embodiment, Rs * -Reduction rate Rs at the start of fusion in the Dp curve* When the harmonic mean particle size Dp at which the particle size distribution is maximized is set as the reference value S, in addition to satisfying the first condition, the harmonic mean particle size Dp of the sintered ore to be charged after adjusting the particle size distribution must be a It is preferable to adjust the particle size distribution so as to satisfy the condition (fifth condition) that satisfies the following formula (1).

[0147]

number

[0148] The above-mentioned Rs. * In the -Dp curve, the reduction rate at the start of fusion Rs * The reduction rate at the start of fusion Rs is higher within ±2 [mm] of the harmonic mean particle size Dp, where Dp is the maximum value, compared to when it is outside the range. * tends to show higher values. * -Reduction rate Rs at the start of fusion in the Dp curve * When the harmonic mean particle size Dp at which the particle size distribution is maximized is set as the reference value S, the harmonic mean particle size Dp of the sintered ore to be charged after adjusting the particle size distribution is a When the above formula (1) is satisfied, the reduction rate Rs at the start of fusion for the sintered ore to be charged, which is the target for adjusting the particle size distribution, is * can be further increased, and the reducing agent ratio is likely to be further reduced. [Example]

[0149] Next, the present invention will be described in more detail with reference to examples, although the present invention is not limited to these examples.

[0150] Evaluation 1 (reduction rate at the start of fusion Rs * (Effect of harmonic mean particle size Dp and initial porosity ε0 on Under the analysis conditions shown below, Rs * Analysis was performed using an estimation model, and the reduction rate at the start of fusion Rs *The effects of the harmonic mean particle size Dp and the initial porosity ε0 on the

[0151] In this analysis, the apparent density of the sinter packed bed is set to 3485 kg / m 3 The sinter packed bed was assumed to be formed entirely of sinter with the same particle size, and the particle size (harmonic mean particle size Dp) of the sinter was set to 10, 12, 14, 16, 18, 20, 22, 24, or 26 mm. The initial porosity of the sinter packed bed was set to 0.38 or 0.40, taking into account the particle size distribution (Base Condition I and Base Condition II) of Evaluation 2 described below. The temperature rise, loading pattern, and reducing gas composition were as shown in Figure 5a, the composition pattern (CO / (CO + CO)) shown in Figure 5b, and the loading pattern shown in Figure 5c. The reducing gas flow rate was set to the bosh gas flow rate obtained from past operational performance, and the reducing gas flow velocity was set to 0.82 Nm / s, calculated by dividing the bosh gas flow rate by the cross-sectional area of ​​the blast furnace from which the bosh gas flow rate was obtained. The furnace pressure was assumed to be constant at 2.7 atm (0.27 MPa). The shape factor was determined from the particle size (harmonic mean particle size) of the sintered ore under study based on Non-Patent Document 2. The softening and shrinkage parameters (η0, c1 to c6, α) were selected and set from the ranges described above. The bed height was set to 300 mm.

[0152] One layer of the sinter packed bed for investigation was divided into multiple calculation cells arranged in the bed height direction. The calculation cells were 1 mm in the bed height direction. The calculation period Δt was set to 5 seconds, and the reduction rate, contraction rate, and pressure loss were repeatedly estimated using the above method until the gradient of the pressure loss of the entire sinter packed bed for investigation reached 50 kPa / m. The reduction rates (reduction rate of sinter) of each calculation cell when the pressure loss reached 50 kPa / m were averaged to obtain the reduction rate at the start of fusion Rs * In this analysis, the temperature of each calculation cell when the pressure drop gradient reached 50 kPa / m was also calculated, and these temperatures were averaged to obtain the fusion start temperature Ts * In addition, the reduction rate of each calculation cell when the temperature of the sintered ore packed bed reached 1200°C (reduction rate of the sintered ore) was also calculated, and these reduction rates were averaged to obtain the reduction rate R 1200 was acquired as.

[0153] The analysis results are shown in FIGS. 6a to 6c.

[0154] Figure 6a shows the fusion start temperature Ts * The graph shows the relationship between the initial porosity ε0 and the harmonic mean particle diameter Dp, and shows two curves for initial porosity ε0 of 0.38 and 0.40. As shown in Fig. 6a, when the harmonic mean particle diameter Dp of the sintered ore used for the study is in the range of 22 to 26 mm, the increase in pressure drop due to the decrease in the harmonic mean particle diameter Dp and the suppression of layer shrinkage due to the promotion of reduction are offset, and the fusion start temperature Ts * On the other hand, when the harmonic mean particle diameter Dp is smaller than 22 mm, the influence of the increase in pressure drop becomes large, and the fusion start temperature Ts * In addition, when the initial porosity ε0 decreased by 0.02, Ts * The temperature dropped by 8 to 15 degrees Celsius.

[0155] Figure 6b shows the reduction rate R 1200 6b shows the relationship between the reduction ratio R and the harmonic mean particle diameter Dp, and shows two curves when the initial porosity ε0 is 0.38 or 0.40. 1200 increased almost linearly with the decrease in the harmonic mean particle diameter Dp. On the other hand, even if the initial porosity ε0 decreased by 0.02, the reduction ratio R 1200 was almost unchanged.

[0156] Figure 6c shows the reduction rate at the start of fusion Rs * and the harmonic mean particle diameter Dp, and there are two types of curves (Rs * As shown in Fig. 6c, in the range of harmonic mean particle diameter Dp from 12 to 26 mm, the reduction ratio at the start of fusion Rs decreases with the decrease in harmonic mean particle diameter Dp. *However, it reached a maximum value at a harmonic mean particle diameter Dp of 12 mm and then began to decrease slightly at 10 mm. From these results, it became clear that for sintered ore with a harmonic mean particle diameter Dp of greater than 12 mm, the effect of promoting reduction due to the decrease in harmonic mean particle diameter Dp was large, while for sintered ore with a harmonic mean particle diameter Dp of less than 12 mm, the effect of increasing pressure drop due to the decrease in harmonic mean particle diameter Dp was large. In other words, if the particle size distribution of the sintered ore to be charged is adjusted so that the harmonic mean particle diameter Dp approaches 12 mm, the reduction rate Rs at the start of fusion can be increased. * It has been shown that it can be increased.

[0157] In addition, as shown in Fig. 6c, when the initial porosity ε0 decreases by 0.02, the reduction rate at the start of fusion Rs * From this result, it can be seen that if the particle size distribution of the sintered ore to be charged is adjusted so that the initial porosity ε0 increases, the reduction ratio Rs at the start of fusion can be increased. * It was found that it is possible to increase

[0158] Also, Rs shown in Figure 6c * From the -Dp curve, the reduction rate at the start of fusion Rs * The change in ΔRs * It has been revealed that the change ΔDp in the harmonic mean particle diameter Dp and the change Δε0 in the initial porosity ε0 can be expressed by the following formulas (23) and (24). * indicates the amount of change when the particle size distribution of sintered ore for charging, whose harmonic mean particle size Dp exceeds 12 mm, is adjusted so that the harmonic mean particle size Dpa after particle size distribution adjustment is 12 mm or more, and the amount of change ΔRs in the following formula (24) * indicates the amount of change when the particle size distribution of sintered ore for charging, which has a harmonic mean particle diameter Dp of less than 12 mm, is adjusted so that the harmonic mean particle diameter Dpa after particle size distribution adjustment is 12 mm or less.

[0159]

number

[0160] In the above formula (23), the coefficient -1.2 [% / mm] multiplied by the amount of change ΔDp is the ratio of the two types of Rs in the range where the harmonic mean particle diameter Dp is 12 mm or more. * In the above formula (24), the coefficient +1.2 [% / mm] multiplied by the amount of change ΔDp is the average value of the slope of the -Dp curve. * In addition, in the above equations (23) and (24), the coefficient 150 [% / -] multiplied by the amount of change Δε0 is the average value of the slope of the -Dp curve. * -Rs of Dp curve * The average difference (1.5-4.2%) between the two types of Rs * This value was obtained by dividing by the difference in initial porosity ε0 (0.02) used to obtain the -Dp curve.

[0161] Evaluation 2 (Reduction rate Rs at the start of fusion by adjusting particle size distribution) * (changes in For each of the sintered ore to be charged having particle size distributions under base condition I and base condition II shown in Table 1 below, the initial void fraction ε0 when the sintered ore to be charged packed bed was formed was calculated from the above formula (22), and the harmonic mean particle diameter Dp was calculated from the above formula (4).

[0162] [Table 1]

[0163] For the sintered ore charged under base condition I, the harmonic mean particle diameter Dp was greater than 12 mm. Therefore, by eliminating coarse particles, it was expected that the harmonic mean particle diameter Dp would approach 12 mm and the initial porosity ε0 would increase. Therefore, for the sintered ore charged under base condition I, which excluded coarse particles (coarse particles excluded as shown in Table 1), the initial porosity ε0 and the harmonic mean particle diameter Dp were calculated based on the above equations (22) and (4) when the sintered ore packed bed was formed. As shown in Table 1, by eliminating coarse particles with a particle diameter of more than 40 mm and roughly halving the coarse particles with a particle diameter of more than 25 mm and less than 40 mm, the harmonic mean particle diameter Dp decreased by 1.28 mm and the initial porosity ε0 increased by 0.0045. Furthermore, by substituting the change in harmonic mean particle diameter Dp (-1.28 mm) and the change in initial porosity ε0 (0.0045) into the above equation (23), the reduction ratio at the start of fusion Rs * It was estimated that the rate would increase by 2.20%.

[0164] For the sintered ore charged under base condition II, the harmonic mean particle diameter Dp was below 12 mm. Therefore, by eliminating fine particles, it was expected that the harmonic mean particle diameter Dp would approach 12 mm and the initial porosity ε0 would increase. Therefore, for the sintered ore charged under base condition II, in which fine particles were excluded (fine particles excluded as shown in Table 1), the initial porosity ε0 and the harmonic mean particle diameter Dp were calculated based on the above equations (22) and (4) when the sintered ore charged packed bed was formed. As shown in Table 1, by eliminating fine particles with a particle diameter of 5 mm or less, the harmonic mean particle diameter Dp increased by 0.84 mm and the initial porosity ε0 increased by 0.0043. Furthermore, when the change in harmonic mean particle diameter Dp (0.84 mm) and the change in initial porosity ε0 (0.0043) were substituted into the above equation (24), the reduction ratio at the start of fusion Rs * It was estimated that the rate would increase by 1.65%.

[0165] Evaluation 3 (reduction ratio at the start of fusion relative to reducing agent ratio Rs * (effect of 5000m 3 For large blast furnaces of the same class, the reduction ratio at the start of fusion relative to the reducing agent ratio Rs *The reducing agent ratio (hereinafter referred to as "RAR") refers to the amount of reducing agent [kg / pt] required to produce 1 ton of pig iron.

[0166] Sintered ore with a particle size distribution similar to that of base condition I (a particle size distribution with a harmonic mean particle size Dp exceeding 12 mm) was prepared for charging. This sintered ore was used to form an ore layer, and the target blast furnace was operated for a specified period. The ore layer contained pellets and lump ore in addition to the sintered ore. After a specified period, the particle size distribution of the sintered ore used in the target blast furnace was adjusted by changing the proportion of sintered ore with a particle size exceeding 25 mm (hereinafter referred to as the "sintered ore + 25 mm proportion"). The sintered ore before particle size distribution adjustment was replaced with sintered ore with the adjusted particle size distribution (the same amount as before particle size distribution adjustment) to form an ore layer, and the target blast furnace was operated for another specified period. This procedure was repeated multiple times, and the RAR of the target blast furnace was determined for each specified period.

[0167] For each sintered ore charge (sintered ore with different sintered ore + 25mm ratios) used in the target blast furnace, the initial void fraction ε0 was calculated using Equation (22) and the harmonic mean particle diameter Dp was calculated using Equation (4). Figure 7a shows the relationship between the sintered ore + 25mm ratio and the initial void fraction ε0, as well as the relationship between the sintered ore + 25mm ratio and the harmonic mean particle diameter Dp. As shown in Figure 7a, as the sintered ore + 25mm ratio decreased, the harmonic mean particle diameter Dp decreased and the initial void fraction ε0 increased. From these results, it can be seen that when the harmonic mean particle diameter Dp exceeds 12 mm, decreasing the sintered ore + 25mm ratio brings the harmonic mean particle diameter Dp closer to 12 mm and increases the initial void fraction ε0.

[0168] In addition, the RAR of the target blast furnace and the reduction ratio Rs at the start of fusion of the ore layer formed from the ore raw material used when calculating the RAR were * As shown in Fig. 7b, the reduction rate at the start of fusion of the ore layer, Rs * As the temperature increased, the RAR tended to decrease.

[0169] The reduction rate at the start of fusion of the ore layer, Rs * is the reduction rate Rs of the packed layer (the ore layer consisting of one type of ore) at the start of fusion for each type of ore material that forms the ore layer. * The reduction rate Rs at the start of fusion of the packed bed was calculated. * was calculated by taking a weighted average according to the blending ratio [mass%] of the ore raw material that forms the packed layer in the ore layer. In addition, the reduction ratio Rs at the start of fusion of the packed layer (the ore layer consisting of one type of ore raw material) * is the above-mentioned Rs * The conditions were determined based on an estimation model, and for each condition (a) above, conditions identical to or similar to the packed state of each packed bed (ore layer consisting of one type of ore raw material) were used, and for each condition (b) to (d) above, conditions identical to or similar to the blast furnace in which the ore layer was formed were used.

[0170] From the results of evaluations 1 to 3 described above, it can be seen that the initial void ratio ε0 of the sintered ore packed bed for charging increases, and the harmonic mean particle size Dp of the sintered ore for charging approaches the reference value S (12 mm). By adjusting the particle size distribution of the sintered ore for charging, the reduction ratio Rs at the start of fusion for the sintered ore for which the particle size distribution is adjusted can be increased. * It is estimated that the reduction rate Rs of the ore layer at the start of fusion can be increased. * It is understood that the RAR can be reduced by increasing the

Claims

1. A method for adjusting the particle size distribution of sintered ore to be charged for forming an ore layer, comprising: adjusting the particle size distribution of the sintered ore to be charged so that the harmonic mean particle size Dp of the sintered ore to be charged approaches a reference value S; The reduction rate Rs of the sintered ore packed bed for fusion start when the pressure loss of the sintered ore packed bed for fusion start when the pressure loss of the sintered ore packed bed for fusion start when the sintered ore for fusion start reaches a predetermined value is ＊ and the reduction rate Rs at the start of fusion ＊ Rs showing the relationship between the harmonic mean particle diameter Dp of the sintered ore used for the study and ＊ In the -Dp curve, the reduction rate Rs at the start of fusion ＊ The method for adjusting the particle size distribution of sintered ore is characterized in that the reference value S is determined as the harmonic mean particle size Dp at which the value of

2. The initial void ratio ε of the sintered ore packed bed for charging made of the sintered ore for charging ０ 2. The method for adjusting the particle size distribution of sintered ore according to claim 1, wherein the particle size distribution of the sintered ore to be charged is adjusted so that is higher after the particle size distribution adjustment than before the particle size distribution adjustment.

3. The reduction rate Rs at the start of fusion ＊ 3. The method for adjusting the particle size distribution of sintered ore according to claim 2, wherein the maximum value of is a local maximum value.

4. When the harmonic mean particle diameter Dp of the sintered ore for charging before adjusting the particle size distribution exceeds the reference value S, the harmonic mean particle diameter Dp of the sintered ore for charging after adjusting the particle size distribution ａ 4. The method for adjusting the particle size distribution of sintered ore according to claim 3, wherein the particle size distribution of the sintered ore to be charged is adjusted so that the particle size distribution approaches the reference value S within a range equal to or greater than the reference value S.

5. 5. The method for adjusting the particle size distribution of sintered ore according to claim 4, wherein the particle size distribution of the sintered ore to be charged is adjusted by reducing the proportion of coarse sintered ore having a particle size exceeding a predetermined particle size.

6. When the harmonic mean particle diameter Dp of the sintered ore for charging before adjusting the particle size distribution is less than the reference value S, the harmonic mean particle diameter Dp of the sintered ore for charging after adjusting the particle size distribution is ａ 4. The method for adjusting the particle size distribution of sintered ore according to claim 3, wherein the particle size distribution of the sintered ore to be charged is adjusted so that the particle size distribution approaches the reference value S within a range not exceeding the reference value S.

7. 7. The method for adjusting the particle size distribution of sintered ore according to claim 6, wherein the particle size distribution of the sintered ore to be charged is adjusted by reducing the proportion of fine sintered ore having a particle size less than a predetermined particle size.

8. The harmonic mean particle size Dp of the sintered ore for charging after adjusting the particle size distribution ａ The method for adjusting the particle size distribution of sintered ore according to any one of claims 3 to 7, characterized in that the particle size distribution of the sintered ore to be charged is adjusted so that the following formula (1) is satisfied: [Equation 1] In the above formula (1), S represents a reference value [mm], and Dp ａ indicates the harmonic mean particle size [mm] of the sintered ore to be charged after adjusting the particle size distribution.

9. 9. The method for adjusting the particle size distribution of sintered ore according to claim 1, wherein the reference value S is 12 mm.

10. The reduction rate Rs of the sintered ore packed bed for investigation made of the sintered ore for investigation at the time of fusion start ＊ The method for adjusting the particle size distribution of sintered ore according to any one of claims 1 to 9, characterized in that the particle size distribution of sintered ore is obtained using one or more of: (a) a packing state of a sintered ore packed bed made of the sintered ore to be charged, (b) a temperature of the sintered ore packed bed, (c) a composition and a flow rate of a reducing gas flowing into the sintered ore packed bed, and (d) a load applied to the sintered ore packed bed in a blast furnace into which the sintered ore to be charged is charged.

11. The reduction ratio Rs at the start of fusion for the sintered ore for charging, the particle size distribution of which is adjusted by the adjusting method according to claim 4, ＊ The change in ΔRs ＊ The change amount ΔRs is estimated based on the following formula (2): ＊ Estimation method. [Equation 2] In the above formula (2), ΔRs ＊ is the reduction rate Rs at the start of fusion for the sintered ore for charging before and after adjusting the particle size distribution ＊ indicates the change [%] in C １ is the reduction rate Rs of the sintered ore at the start of fusion relative to the harmonic mean particle diameter Dp of the sintered ore for investigation, in a range in which the harmonic mean particle diameter Dp of the sintered ore for investigation is equal to or greater than the reference value S. ＊ ΔDp represents the change in the harmonic mean particle diameter Dp of the sintered ore for charging before and after the particle size distribution adjustment [mm], and D １ is the initial porosity ε of the sintered ore for study ０ The reduction rate Rs of the sintered ore for investigation at the start of fusion ＊ indicates the rate of change [% / -] of Δε ０ is the initial void ratio ε of the sintered ore for charging before and after adjusting the particle size distribution ０ The change amount [-] is shown.

12. The reference value S is 12, Said C １ is −1.2, The above D １ is 150, The change amount ΔRs according to claim 11, ＊ Estimation method.

13. The reduction ratio Rs at the start of fusion for the sintered ore for charging, the particle size distribution of which is adjusted by the adjusting method according to claim 6, ＊ The change in ΔRs ＊ The change amount ΔRs is estimated based on the following formula (3). ＊ Estimation method. [Equation 3] In the above formula (3), ΔRs ＊ is the reduction rate Rs at the start of fusion for the sintered ore for charging before and after adjusting the particle size distribution ＊ indicates the change [%] in C ２ is the reduction rate Rs of the sintered ore at the start of fusion relative to the harmonic mean particle diameter Dp of the sintered ore for investigation, in a range in which the harmonic mean particle diameter Dp of the sintered ore for investigation is equal to or less than the reference value S. ＊ ΔDp represents the change in the harmonic mean particle diameter Dp of the sintered ore for charging before and after the particle size distribution adjustment [mm], and D ２ is the initial porosity ε of the sintered ore for study ０ The reduction rate Rs of the sintered ore for investigation at the start of fusion ＊ indicates the rate of change [% / -] of Δε ０ is the initial void ratio ε of the sintered ore for charging before and after adjusting the particle size distribution ０ The change amount [-] is shown.

14. The reference value S is 12, Said C ２ is 1.2, The above D ２ is 150, The change amount ΔRs according to claim 13, ＊ Estimation method.

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