JP2023050035A - ADJUSTMENT METHOD OF PARTICLE SIZE DISTRIBUTION OF SINTERED ORE AND ESTIMATION METHOD OF CHANGE AMOUNT ΔRs* IN REDUCTION RATIO Rs* AT THE START OF FUSION - Google Patents

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

The present invention relates to a method for adjusting the particle size distribution of sintered ore, and a method for estimating the amount of change ΔRs ^* in the reduction rate Rs ^* at the start of fusion bonding of sintered ore before and after adjusting the particle size distribution.

In the blast furnace, ore raw materials (sintered ore, pellets, lump ore, etc.) as iron-containing raw materials and coke as a reducing agent and fuel are alternately charged from the top of the furnace, and hot air is blown from the tuyeres at the bottom of the furnace. At the same time, auxiliary fuel such as pulverized coal is injected. The ore raw material and coke charged from the top of the furnace (hereinafter also collectively referred to as "charge") form alternately stacked ore layers and coke layers, respectively. The ore raw material and coke are heated by gas rising from the lower part of the blast furnace while gradually descending toward the lower part of the blast furnace as the load is unloaded in the blast furnace.

When the ore raw material descending while being heated and reduced in the blast furnace reaches the lower part of the furnace, it begins to soften and fuse to form an ore fused layer. In the ore cohesive layer, voids between ore raw materials are reduced, and gas permeability is deteriorated. As a result, the gas passes through the coke layers between the ore coalescing layers and rises toward the furnace top. Therefore, the shape of the cohesive zone has a great effect on the air permeability of the blast furnace. The cohesive zone refers to a region in the blast furnace where ore cohesive layers exist (including coke layers between ore cohesive layers).

The high-temperature properties of ore raw materials are one of the important factors that determine the shape of the cohesive zone. Therefore, conventionally, the reduction rate at the start of fusion (Rs), the fusion start temperature (Ts), the dropping start temperature (Td), or the difference between them (ΔT=Td−Ts), etc., which are obtained by a load softening test (Non-Patent Document 1).

In addition, as an index for evaluating the high-temperature properties of ore raw materials (hereinafter also referred to as “high-temperature property evaluation index”), the S value (time-pressure loss curve obtained by heating and reducing sintered ore, pressure loss of 200 mmH ₂ 0) is known. In Patent Document 1, sintered ore is divided into two types according to high temperature properties (S value), sintered ore with poor high temperature properties is charged as a lower layer, and sintered ore with excellent high temperature properties is added to the upper layer. The reducibility of the entire ore layer is improved by charging as

JP-A-2002-309306

Tetsu to Hagane Vol.83 (1997) pp.97-102 Tetsu to Hagane Vol.77 (1991) pp.1561-1568 Tetsu to Hagane Vol.80 (1994) pp.431-439 Tetsu to Hagane Vol.98 (2012) pp.431-439 Tetsu to Hagane Vol.66 (1980) pp.1908-1917 Tetsu to Hagane Vol.100 (2014) pp.270-276

An object of the present invention is to provide a method for adjusting the particle size distribution of sintered ore that can reduce the reducing material ratio. Another object of the present invention is to provide a method for estimating the amount of change ΔRs ^* in the reduction rate Rs ^* at the start of fusion of sintered ore before and after adjusting the particle size distribution.

In order to solve the above problems, the method for adjusting the particle size distribution of the charging sintered ore used for forming the ore layer according to the present invention is as follows: (1) The harmonic average particle diameter Dp of the charging sintered ore including adjusting the particle size distribution of the charging sintered ore so as to approach the value S, and the pressure loss of the investigational sintered ore packed bed made of the investigational sintered ore for determining the reference value S is predetermined. Harmonic average particle size of the sintered ore for investigation used to obtain the reduction rate Rs ^* at the start of fusion of the sintered ore packed bed for investigation when the value is reached, and the reduction rate Rs ^* at the start of fusion In the Rs ^* -Dp curve showing the relationship between Dp and Rs*, the reference value S is determined as the harmonic mean particle size Dp at which the reduction rate Rs ^* at the start of fusion bonding reaches its maximum value.

(2) the charging sintered ore so that the initial porosity ε ₀ of the charging sintered ore packed bed made of the charging sintered ore is higher after the particle size distribution adjustment than before the particle size distribution adjustment; The method for adjusting the particle size distribution according to (1), characterized in that the particle size distribution of the sintered ore is adjusted.

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

(4) When the harmonic average particle size Dp of the charging sintered ore before adjusting the particle size distribution exceeds the reference value S, the harmonic average particle size Dp of the charging sintered ore after adjusting the particle size distribution The method for adjusting the particle size distribution according to (3), wherein the particle size distribution of the sintered ore for charging is adjusted so that _a is equal to or greater than the reference value S.

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

(6) When the harmonic average particle size Dp of the sintered ore for charging before adjusting the particle size distribution is less than the reference value S, the harmonic average particle size Dp _a of the sintered ore for charging after adjusting the particle size distribution The method for adjusting the particle size distribution according to (3), wherein the particle size distribution of the sintered ore for charging is adjusted so that the is equal to or less than the reference value S.

(7) The method for adjusting the particle size distribution according to (6), characterized in that the particle size distribution of the charging sintered ore is adjusted by reducing the proportion of fine-grained sintered ore having a particle size less than a predetermined particle size. .

上記式（１）において、Ｓは、基準値［ｍｍ］を示し、Ｄｐ_ａは、粒度分布を調整した後の前記装入用焼結鉱の調和平均粒径［ｍｍ］を示す。 (8) Adjusting the particle size distribution of the sintered ore to be charged so that the harmonic average particle diameter _Dpa of the sintered ore to be charged after adjusting the particle size distribution satisfies the following formula (1): The method for adjusting the particle size distribution according to any one of (3) to (7).

In the above formula (1), S indicates a reference value [mm], and _Dpa indicates a harmonic mean particle size [mm] of the sintered ore for charging after adjusting the particle size distribution.

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

(10) The reduction rate Rs ^* at the start of fusion bonding of the sintered ore packed bed for investigation made of the sintered ore for investigation is determined by (a) the above (b) temperature of the sintered ore packed bed for charging; (c) reduction flowing in the sintered ore packed bed for charging Any one of (1) to (9), characterized in that it is obtained using one or more of gas composition and flow rate, and (d) load applied to the charging sinter packed bed. or the method for adjusting the particle size distribution according to item 1.

上記式（２）において、ΔＲｓ^＊は、粒度分布の調整前後における前記装入用焼結鉱に関する前記融着開始時還元率Ｒｓ^＊の変化量［％］を示し、Ｃ_１は、前記検討用焼結鉱の前記調和平均粒径Ｄｐが前記基準値Ｓ以上の範囲内における、前記検討用焼結鉱の前記調和平均粒径Ｄｐに対する前記検討用焼結鉱の前記融着開始時還元率Ｒｓ^＊の変化率［％／ｍｍ］を示し、ΔＤｐは、粒度分布の調整前後における前記装入用焼結鉱の前記調和平均粒径Ｄｐの変化量［ｍｍ］を示し、Ｄ_１は、前記検討用焼結鉱の初期空隙率ε_０に対する前記検討用焼結鉱の前記融着開始時還元率Ｒｓ^＊の変化率［％／－］を示し、Δε_０は、粒度分布の調整前後における前記装入用焼結鉱に関する前記初期空隙率ε_０の変化量［－］を示す。 (11) The amount of change ΔRs ^* of the reduction rate Rs ^* at the start of fusion for the charging sinter ore, the particle size distribution of which is adjusted by the adjustment method described in (4), is calculated based on the following formula (2): A method for estimating the amount of change ΔRs ^* , characterized by estimating.

In the above formula (2), ΔRs ^* indicates the amount of change [%] in the reduction rate Rs ^* at the start of fusion bonding regarding the charging sintered ore before and after adjusting the particle size distribution, and _C1 is the The reduction rate Rs at the start of fusion bonding of the sintered ore for investigation with respect to the harmonic average particle diameter Dp of the sintered ore for investigation in the range where the harmonic average particle diameter Dp of the sintered ore is equal to or greater than the reference value S ^* indicates the rate of change [% / mm], ΔDp indicates the amount of change [mm] in the harmonic average particle diameter Dp of the sintered ore for charging before and after adjusting the particle size distribution, and D ₁ is the study shows the rate of change [%/−] of the reduction rate Rs ^* at the start of fusion bonding of the sintered ore for investigation with respect to the initial porosity ε ₀ of the sintered ore for study, and Δε ₀ is the sintered ore before and after adjustment of the particle size distribution. The amount of change [-] in the initial porosity _ε0 for the required sintered ore is shown.

(12) The method for estimating the amount of change ΔRs ^* according to (11), wherein the reference value S is 12, the C ₁ is −1.2, and the D ₁ is 150.

上記式（３）において、ΔＲｓ^＊は、粒度分布の調整前後における前記装入用焼結鉱に関する前記融着開始時還元率Ｒｓ^＊の変化量［％］を示し、Ｃ_２は、前記検討用焼結鉱の前記調和平均粒径Ｄｐが前記基準値Ｓ以下の範囲内における、前記検討用焼結鉱の前記調和平均粒径Ｄｐに対する前記検討用焼結鉱の前記融着開始時還元率Ｒｓ^＊の変化率［％／ｍｍ］を示し、ΔＤｐは、粒度分布の調整前後における前記装入用焼結鉱の前記調和平均粒径Ｄｐの変化量［ｍｍ］を示し、Ｄ_２は、前記検討用焼結鉱の初期空隙率ε_０に対する前記検討用焼結鉱の前記融着開始時還元率Ｒｓ^＊の変化率［％／－］を示し、Δε_０は、粒度分布の調整前後における前記装入用焼結鉱に関する前記初期空隙率ε_０の変化量［－］を示す。 (13) The amount of change ΔRs ^* of the reduction rate Rs ^* at the start of fusion for the charging sintered ore, the particle size distribution of which is adjusted by the adjustment method described in (6), is calculated based on the following formula (3): A method for estimating the amount of change ΔRs ^* , characterized by estimating.

In the above formula (3), ΔRs ^* indicates the amount of change [%] in the reduction rate Rs ^* at the start of fusion bonding regarding the charging sintered ore before and after adjusting the particle size distribution, and _C2 is the The reduction rate Rs at the start of fusion bonding of the sintered ore for investigation with respect to the harmonic average particle diameter Dp of the sintered ore for investigation in the range where the harmonic average particle diameter Dp of the sintered ore is equal to or less than the reference value S ^* indicates the rate of change [% / mm], ΔDp indicates the amount of change [mm] in the harmonic average particle size Dp of the sintered ore for charging before and after adjusting the particle size distribution, and _D2 is the above-described study. shows the rate of change [%/−] of the reduction rate Rs ^* at the start of fusion bonding of the sintered ore for investigation with respect to the initial porosity ε ₀ of the sintered ore for study, and Δε ₀ is the sintered ore before and after adjustment of the particle size distribution. The amount of change [-] in the initial porosity _ε0 for the required sintered ore is shown.

(14) The method for estimating the amount of change ΔRs ^* according to (13), wherein the reference value S is 12, the _C2 is 1.2, and the _D2 is 150.

ADVANTAGE OF THE INVENTION According to this invention, the adjustment method of the particle size distribution of a sintered ore which can reduce a reducing material ratio can be provided. Further, according to the present invention, it is possible to provide a method for estimating the amount of change ΔRs ^* in the reduction rate Rs* at the start of fusion ^of sintered ore before and after adjusting the particle size distribution.

It is a figure explaining the outline|summary of an Rs ^* estimation model. It is a graph which shows the temperature change of a sintered ore packed bed. It is a graph which shows the change of the load concerning a sintered ore packed bed. It is a graph which shows the flow volume change of the reducing gas which flows through a sintered ore packed bed. It is a graph which shows the composition change of the reducing gas which flows through a sintered ore packed bed. It is a graph which shows the composition change of the reducing gas which flows through a sintered ore packed bed. It is a graph which shows the pressure change of the reducing gas which flows into a sintered ore packed bed. 4 is a flowchart showing a procedure for estimating a reduction rate Rs ^* at the start of fusion bonding; It is a figure explaining the analysis method using an X-ray CT image. It is a graph which shows the temperature change of a sintered ore packed bed. It is a graph which shows the composition change of the reducing gas which flows through a sintered ore packed bed. It is a graph which shows the change of the load concerning a sintered ore packed bed. 4 is a graph showing the relationship between the fusion start temperature Ts ^* and the harmonic mean particle size Dp. 4 is a graph showing the relationship between the reduction rate R ₁₂₀₀ and the harmonic mean particle size Dp. 4 is a graph showing the relationship between the reduction rate Rs ^* at the start of fusion bonding and the harmonic mean particle size Dp. 4 is a graph showing the relationship between the sintering +25 mm ratio and the initial porosity _ε0 , and the relationship between the sintering +25 mm ratio and the harmonic mean grain size Dp. 4 is a graph showing the relationship between the reducing agent ratio and the reduction rate Rs ^* at the start of fusion bonding with respect to sintered ore used when calculating the reducing agent ratio.

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

Conventionally, the fusion start temperature Ts, the reduction rate Rs at the start of fusion, and the like 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 rate Rs at the start of fusion are defined as the temperature (the temperature of the ore layer) and the reduction rate (the reduction rate of the ore layer) at which the pressure loss occurring in the ore layer reaches a predetermined value, respectively. It is obtained by reducing the ore raw material using a high-temperature property tester under the test conditions shown in Non-Patent Document 1. The predetermined value represents the pressure loss when the ore cohesive layer is formed.

On the other hand, in the blast furnace, (a) filling state of the ore layer (particle size (harmonic mean particle size), porosity, charged layer thickness, mixed charging of various raw materials, etc.), (b) temperature of the ore layer, (c ) The composition and flow rate of the reducing gas flowing through the ore layer and (d) the load applied to the ore layer vary depending on the blast furnace operating conditions, and the conditions included in these (hereinafter also referred to as “high temperature property related conditions”) Affects the high temperature properties of For this reason, it is preferable that the index for evaluating the high-temperature properties of ore raw materials reflects the influence of one or more of the conditions related to the high-temperature properties of the blast furnace into which the ore raw materials to be evaluated are charged. However, the fusion start temperature Ts and the reduction rate Rs at the start of fusion obtained by the method described in Non-Patent Document 1 are difficult to reflect these effects. For example, in Non-Patent Document 1, the reduction rate Rs at the start of fusion bonding is measured for sintered ore grain-sized to 10 to 15 mm.

The present inventors conducted studies based on this finding. As a result, the fusion start temperature of the ore layer (hereinafter also referred to as "fusion start temperature Ts ^* ") and the reduction rate at the start of fusion of the ore layer (hereinafter, "at the start of fusion Also referred to as "reduction rate Rs ^* ") was found. The fusion start temperature Ts ^* is the temperature (the temperature of the ore layer) when the pressure loss of the ore layer reaches a predetermined value, and is the temperature obtained using the high-temperature property-related conditions. The reduction rate Rs ^* at the start of fusion bonding is the reduction rate of the ore layer when the pressure loss of the ore layer reaches a predetermined value, and is the reduction rate obtained using the high-temperature property-related conditions.

Note that the fusion start temperature Ts ^* and the reduction rate Rs ^* at the start of fusion are high-temperature property evaluation indices required not for the ore raw material but for the ore layer. The predetermined value used to obtain the fusion start temperature Ts ^* and the reduction rate Rs ^* at the start of fusion is the pressure loss (or its gradient) when the ore fusion layer is formed. It can be 0.8 Pa or 50 kPa/m. The details of the fusion start temperature Ts ^* and the reduction rate Rs ^* at the start of fusion will be described later.

The inventors of the present invention further studied the fusion initiation temperature Ts ^* and the reduction rate Rs ^* at the initiation of fusion, and found that (a) the filling state of the ore layer (particle diameter (harmonic mean particle diameter), porosity, We paid attention to the particle size of the charging 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, so the reduction rate of the ore raw material increases. This contributes to an increase in the reduction rate Rs ^* at the start of fusion bonding. On the other hand, when the contact area with the reducing gas increases, the pressure loss in the ore layer increases. Therefore, as the contact area increases, the fusion initiation temperature Ts ^* begins to decrease. A decrease in the fusion initiation temperature Ts ^* can be a factor in reducing the reduction rate Rs ^* at the initiation of fusion. In other words, the reducibility and air permeability change in a trade-off relationship with the change in particle size. Based on this knowledge, the present inventors considered clarifying the appropriate particle size distribution of sintered ore, which is one of the ore raw materials, in the operation of a blast furnace from the viewpoint of high-temperature properties.

Therefore, as described later, the present inventors used an ore layer formed only of sintered ore (hereinafter also referred to as a "sintered ore packed layer") to determine the reduction rate Rs ^* at the start of fusion and the sintered ore The relationship of the harmonic average particle size Dp of the was examined. As a result, by adjusting the particle size distribution of the sintered ore so that the harmonic average particle diameter Dp of the sintered ore approaches the reference value S described later, the ore layer formed using the sintered ore starts fusion bonding. The inventors have found that the time reduction rate Rs ^* can be increased and the reducing agent ratio can be reduced, leading to the completion of the present invention. Hereinafter, the sintered ore for determining the reference value S may be referred to as "sintered ore for examination".

In this specification, the ore layer refers to a layer containing an ore raw material among the particle packed layers formed in the blast furnace, and the ore raw material refers to a raw material containing 50% by mass or more of iron. Examples of specific ore raw materials include sintered ore, pellets and lump ore. Further, in this specification, the ore cohesive layer refers to an ore layer in which the ore raw material is softened and/or cohesive, and the cohesive zone is a region in the blast furnace where the ore cohesive layer exists (ore melting). including coke layers between deposition layers).

An embodiment of the present invention will be described below.

The adjustment method of the present embodiment is a method of adjusting the particle size distribution of sintered ore. The sintered ore whose particle size distribution has been adjusted by the adjustment method of the present embodiment is used for forming an ore layer. Hereinafter, the sintered ore having an adjusted particle size distribution and forming an ore layer may be referred to as "charging sintered ore".

In addition, the ore layer does not need to be formed only of the charging sintered ore whose particle size distribution has been adjusted by the adjustment method of the present embodiment. It may also be formed including raw materials, coke, ferro-coke, and other raw materials such as adjuncts.

The adjustment method of the present embodiment adjusts the particle size distribution of charging sintered ore so as to satisfy the first condition shown below.

The first condition is that the harmonic average particle diameter Dp of the charging sintered ore to be adjusted for the particle size distribution (that is, the charging sintered ore before the particle size distribution adjustment) is the particle size of the charging sintered ore The condition is that the reference value S is approached by adjusting the distribution.

上記式（４）において、Ｄｐは、調和平均粒径［ｍｍ］を示し、ｎは、篩い分けに用いた篩の数［－］を示し、Ｗ_ｉは、粒径範囲ｉの装入用焼結鉱の質量比率［－］を示し、Ｄ_ｉは、粒径範囲ｉの代表径［ｍｍ］を示す。代表径Ｄ_ｉは、各篩の篩目の間隔を考慮して決定される値であり、例えば、篩目の間隔の中間粒径を用いることができる。 In the present embodiment, the harmonic mean particle size Dp of the sintered ore for charging is defined by the following formula (4).

In the above formula (4), Dp represents the harmonic average particle size [mm], n represents the number of sieves used for sieving [-], and W _i represents the quenched powder for charging in the particle size range i. indicates the mass ratio [-] of the ore, and D _i indicates the representative diameter [mm] of the particle size range i. The representative diameter D _i is a value determined in consideration of the mesh spacing of each sieve, and for example, an intermediate particle size between the meshes can be used.

Here, the harmonic mean particle diameter Dp approaches the reference value S means that the absolute value of the difference between the harmonic mean particle diameter Dp and the reference value S decreases. may be less than the standard value S by adjusting the particle size distribution, and the harmonic mean particle size Dp that is less than the standard value S may exceed the standard value S by adjusting the particle size distribution. .

In the adjustment method of the present embodiment, the particle size distribution can be adjusted by changing the proportion (mass ratio) of the charged sintered ore having a particle size range i. For example, when the harmonic average particle size Dp of the charging sinter ore whose particle size distribution is to be adjusted exceeds the reference value S, by decreasing the ratio of coarse-grained sinter ore exceeding a predetermined particle size, The particle size distribution can be adjusted to satisfy the condition of 1. The above-described predetermined particle size is a particle size exceeding the harmonic average particle size Dp of the charged sintered ore whose particle size distribution is to be adjusted, and is, for example, 50 mm. Further, for example, when the harmonic average particle size Dp of the sintered ore to be charged, which is the target for adjusting the particle size distribution, is less than the reference value S, the proportion of fine-grained sintered ore smaller than a predetermined particle size is reduced. , the particle size distribution can be adjusted to satisfy the first condition. In addition, the predetermined particle size described above is a particle size smaller than the harmonic average particle size Dp, and is 5 mm as an example.

Next, the reference value S to which the harmonic mean particle size Dp is approximated will be specifically described.

The reference value S is the reduction rate Rs ^* of the investigational sintered ore packed bed when the pressure loss of the investigational sintered ore packed bed made of the investigational sintered ore reaches a predetermined value (reduction rate Rs at the start of fusion bonding ^* ) and the harmonic average grain size Dp of the sintered ore for study used to obtain the reduction rate Rs ^* at the start of fusion bonding (hereinafter also referred to as “Rs ^* -Dp curve”). This is the harmonic mean particle diameter Dp at which the reduction rate Rs ^* at the start of fusion bonding reaches its maximum value.

The reference value S may differ depending on the test conditions of the load softening test described later and the input conditions of the Rs ^* estimation model, and cannot be uniquely defined, but can be set to 12 [mm], for example. Note that the Rs ^* -Dp curve may be obtained as a straight line.

To obtain the Rs ^* -Dp curve, either measurements by load softening tests or calculations by mathematical models are used. As a calculation method, for example, conditions related to high temperature properties (a) filling state of sintered ore packed bed, (b) temperature of sintered ore packed bed, (c) composition of reducing gas flowing through sintered ore packed bed and flow rate, and (d) a model for calculating the reduction rate Rs ^* at the start of fusion bonding of the sintered ore packed bed using the load applied to the sintered ore packed bed as input conditions (hereinafter, also referred to as "Rs ^* estimation model" ) is used. More specifically, a plurality of types of input conditions that differ only in the harmonic average particle size Dp of the sintered ore for investigation are input to the Rs ^* estimation model, and the time at which the sintered ore packed bed for investigation starts fusion bonding for each input condition The reduction rate Rs ^* is calculated, and the calculated reduction rate Rs ^* at the start of fusion bonding and the harmonic mean particle size Dp of the sintered ore for investigation used to calculate the reduction rate Rs ^* at the start of fusion are plotted in a graph. You can get it by going.

Conditions related to high-temperature properties (a) Regarding the filling state of the sintered ore packed bed, the sintered ore for charging and the sintered ore for investigation do not necessarily have to have the same porosity and other properties. Sintered ore having general properties may be used as the ore. According to the studies of the present inventors, even if the sintered ore has different porosity and other properties, the response of the reduction rate Rs ^* at the start of fusion bonding to the change in the harmonic average grain size Dp can be considered to be the same. This is because the sensitivity analysis can be performed without unifying the properties of the sintered ore for use and the sintered ore for investigation. In addition, the rate of change of the reduction rate Rs* at the start of fusion with respect to the harmonic mean particle size Dp for obtaining the amount of change ΔRs ^* in the reduction rate Rs ^* at the start of fusion ^for charging sintered ore before and after adjusting the particle size distribution C ₁ and C ₂ (described later), and change rates D ₁ and D ₂ (described later) of the reduction rate Rs ^* at the start of fusion with respect to the initial porosity ε ₀ Even if the properties are not unified, it is required with sufficient reliability.

It is preferable that the sintered ore for charging and the sintered ore for investigation have the same conditions (porosity and other properties) in (a) above, and the conditions in (a) above are the same. is most preferred. In other words, it is most preferable to use (a) the filling state of the sintered ore packed bed for charging made of the sintered ore for charging for the above (a) used as the input condition. Between the charging sintered ore and the investigational sintered ore, the closer each of the above conditions (a) is, the more the reduction rate Rs ^* at the start of fusion bonding calculated by the Rs ^* estimation model is. The influence of the conditions related to high-temperature properties of the blast furnace into which the sintered ore to be adjusted is charged (hereinafter also referred to as “target blast furnace”) is more reflected. Therefore, it is possible to obtain the reduction rate Rs ^* at the start of fusion that more reflects the high-temperature properties of the sintered ore to be charged, the particle size distribution of which is to be adjusted, in the target blast furnace.

The Rs ^* estimation model will be specifically described below.

(Rs ^* Outline of estimation model)
In the Rs ^* estimation model, first, a single layer of the sintered ore packed bed for investigation immediately after the sintered ore for investigation is charged into the blast furnace is divided into multiple regions arranged in the bed height direction (divided by a computational grid described later). area (hereinafter also referred to as “calculation cell”)). Next, the reduction rate of the sintered ore for examination, the shrinkage rate of the sintered ore packed bed for examination, and the pressure loss caused in the sintered ore packed bed for examination are estimated for each calculation cell. For estimation of reduction rate, shrinkage rate and pressure loss, (a) filling state of sintered ore packed bed for examination, (b) temperature of sintered ore packed bed for examination, (c) sintered ore packed bed for examination The composition and flow rate of the reducing gas flowing through and (d) the load on the investigational sinter packed bed are used as input conditions.

As described above, it is most preferable to use (a) the filling state of the charging sintered ore packed bed for (a) used as the input condition, but some of (a) used as the input condition Even if only the condition of (a) is the same as the filling state of the sintered ore packed bed for charging, the influence of the conditions related to the high-temperature properties of the target blast furnace can be reflected in the reduction rate Rs ^* at the start of fusion bonding. . For example, as the harmonic mean particle size in (a) used as the input condition, the harmonic mean particle size obtained from the particle size distribution of the charged sinter whose particle size distribution is to be adjusted, or used as the input condition By using the porosity obtained from the particle size distribution of the sintered ore for charging as the porosity in (a), the effect of the conditions related to the high-temperature properties of the target blast furnace can be applied to the reduction rate Rs ^* at the start of fusion bonding. can be reflected.

Then, the reduction rate Rs ^* at the start of fusion bonding of the sintered ore packed bed for investigation is estimated based on the reduction rate, shrinkage rate, and pressure loss estimated using these input conditions. As a specific estimation method, the reduction rate, shrinkage rate, and pressure loss are estimated for each calculation cell after a predetermined time t (time obtained by multiplying the calculation cycle Δt by the number of times of estimation) from the reference time. , the estimation is repeated until the pressure loss in the sintered ore packed bed for investigation reaches a predetermined value. Then, the average reduction rate of the sintered ore packed bed for investigation when the estimated pressure loss reaches a predetermined value is estimated as the reduction rate Rs ^* at the start of fusion bonding. The reference time is when the sintered ore packed bed for investigation is formed in the blast furnace (in other words, immediately after the sintered ore is charged), or when the sintered ore packed bed for investigation is lowered to the temperature zone where reduction starts. When you can. The temperature at which reduction begins can be, for example, 500°C.

(input condition)
The input conditions used for estimating the reduction rate, contraction rate and pressure loss are the conditions used for estimating the reduction rate, contraction rate and pressure loss. It is a concept that includes both conditions for obtaining conditions to be input into expressions.

FIG. 1 shows specific input conditions. First, among the input conditions shown in FIG. 1, (a) the filling state of the sintered ore packed bed will be described. The filling state is the initial filling state of the investigational sintered ore contained in the investigational sintered ore packed bed (that is, immediately after the investigational sintered ore constituting the investigational sintered ore packed bed is charged into the blast furnace). Specifically, the apparent density of the sintered ore for investigation, the harmonic average particle diameter of the sintered ore for investigation, the shape factor of the sintered ore for investigation, the chemical properties of the sintered ore for investigation Composition, softening shrinkage parameter, initial blending ratio (that is, 100%) indicating the volume ratio of the sintered ore for investigation, initial porosity of the sintered ore packed bed for investigation, and initial layer height of the sintered ore packed bed for investigation mentioned. In this specification, the softening shrinkage parameter refers to a constant η ₀ , coefficients c ₁ to c ₆ , coefficient α, coefficient β, and constant γ used in an estimation formula to be described later.

For each of the above conditions (a), the results obtained by forming the sintered ore packed bed for investigation in a test device and the packing state of the sintered ore packed bed for investigation obtained based on a known mathematical model are used. be able to. 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 below-described formula (22) described in Non-Patent Document 2.

Next, among the input conditions shown in FIG. 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, and (d) the load applied to the sintered ore packed bed and (e) the pressure of the reducing gas. Here, the temperature of the sintered ore packed bed is the temperature of the sintered ore packed bed for investigation (hereinafter also referred to as "estimated sintered ore packed bed") for which the reduction rate, shrinkage rate and pressure loss are estimated. Indicates temperature. The composition of the reducing gas indicates the composition of the reducing gas flowing through the sintered ore packed bed to be estimated. The flow rate of the reducing gas indicates the flow rate of the reducing gas flowing through the sintered ore packed bed to be estimated. The load applied to the sintered ore packed bed indicates the load applied to the sintered ore packed bed to be estimated. The pressure of the reducing gas indicates the pressure of the reducing gas flowing through the sintered ore packed bed to be estimated.

These input conditions are conditions that may change while the sinter packed bed descends in the blast furnace. Therefore, it is preferable to prepare in advance information representing changes in these input conditions during the process in which the sintered ore packed bed for investigation descends in the blast furnace. When estimating the reduction rate, shrinkage rate, and pressure loss, the value obtained when a predetermined time t has elapsed from the reference time (hereinafter simply referred to as "when the predetermined time t has elapsed") is selected from these information. Select and use as an input condition.

As specific information, the temperature rise pattern that shows the temperature change of the sintered ore packed bed for investigation according to the elapsed time, the load pattern that shows the change in the load according to the temperature change of the sintered ore packed bed for investigation, etc. , a flow rate pattern showing changes in gas flow rate according to temperature changes in the sintered ore packed bed for investigation, a composition pattern showing changes in reducing gas composition according to temperature changes in the sintered ore packed bed for investigation, and elapsed time A pressure pattern showing the pressure change of the reducing gas according to .

Information obtained from past operational results and publicly known information can be used for these pieces of information. As an example, the temperature rise pattern is the temperature rise pattern shown in FIG. 2a, the load pattern is the load pattern shown in FIG. 2b, the flow rate pattern is the flow rate pattern shown in FIG. The pressure pattern shown in FIG. 2f can be used for the composition pattern and pressure pattern shown in FIG. 2e.

Among the input conditions shown in FIG. 1, the above (b) to (d) are a general blast furnace different from the blast furnace (target blast furnace) into which the sintered ore for charging, which is the target of particle size distribution adjustment, is charged. may be used, but it is preferred that the conditions of the target blast furnace are used. That is, in the adjustment method of the present embodiment, as the above (b) to (d) used as input conditions, (b) the temperature of the sintered ore packed bed for charging, (c) the temperature of the sintered ore packed bed for charging It is preferable to calculate the reduction rate Rs ^* at the start of fusion using one or more of the composition and flow rate of the flowing reducing gas, and (d) the load applied to the charged sintered ore packed bed. . By using the conditions of the sintered ore packed bed for charging in the target blast furnace for at least one of the above (b) to (d), the reduction rate at the start of fusion Rs ^* calculated by the Rs ^* estimation model reflects the effects of conditions related to high-temperature properties of the target blast furnace. Therefore, it is possible to obtain the reduction rate Rs ^* at the start of fusion that more accurately evaluates the high-temperature properties of the sintered ore to be charged, which is the target of particle size distribution adjustment, in the target blast furnace.

Next, a method for estimating the reduction rate, shrinkage rate, and pressure loss using the input conditions described above will be described with reference to FIG. FIG. 3 is a flow chart showing a procedure for estimating the reduction rate Rs ^* at the start of fusion.

(Setting of computational grid)
In the process of step S101 (computational grid setting step), a computational grid is set that partitions one layer of the sintered ore packed bed for investigation in the blast furnace into an arbitrary number of regions arranged in the bed height direction. The area (calculation cell) partitioned by the computational grid is the area subject to estimation of the reduction rate, shrinkage rate, and pressure loss. loss is output.

(Ore reduction behavior)
In the processing of step S102 (reduction rate calculation step), the reduction rate of the sintered ore for investigation contained in the sintered ore packed bed for investigation when the predetermined time t has elapsed is obtained for each calculation cell.

The reduction rate in the calculation cell when the predetermined time t has elapsed can be obtained, for example, based on the three-interface unreacted nucleus model described in Non-Patent Document 3, and can be estimated using the following formula (5). can.

上記式（５）において、Ｆは所定時間ｔが経過したときのｉ番目（ｉ＝１～区画数）の計算セルの検討用焼結鉱の還元率［％］を示し、ρ_ｏ ^（ｓ）はｓ相の被還元酸素の見掛けモル濃度［ｍｏｌＯ／ｍ^３］を示し、ρ_ｏ ^（ｔ）はｔ相の被還元酸素の見掛けモル濃度［ｍｏｌＯ／ｍ^３］を示し、ρ_ｏ ^（ｈ）はｈ相の被還元酸素の見掛けモル濃度［ｍｏｌＯ／ｍ^３］を示し、ｒ_０は検討用焼結鉱（擬似球体）の中心から表面までの半径［ｍ］を示し、ｒ^{（ｓ／ｔ）}は検討用焼結鉱（擬似球体）の中心からｓ／ｔ界面までの半径［ｍ］を示す。ここで、ｓ相及びｔ相の関係としては、ｈ相（ヘマタイト）及びｍ相（マグネタイト）と、ｍ相（マグネタイト）及びｗ相（ウスタイト）と、ｗ相（ウスタイト）と全鉄（Ｆｅ）相との関係がある。以下、同様である。

In the above formula (5), F represents the reduction rate [%] of the sintered ore for investigation in the i-th (i = 1 to the number of divisions) calculation cell after a predetermined time t has elapsed, and ρ _o ^(s) is the apparent molar concentration of s-phase reducible oxygen [molO/m ³ ], ρ _o ^(t) is the apparent molar concentration of t-phase reducible oxygen [molO/m ³ ], and ρ _o ^(h) indicates the apparent molar concentration of h-phase reducible oxygen [molO/m ³ ], r ₀ indicates the radius [m] from the center to the surface of the sintered ore (pseudo-sphere) for investigation, r ^{(s/t )} indicates the radius [m] from the center of the study sinter (pseudo-sphere) to the s/t interface. Here, the relationship between the s phase and the t phase is as follows: h phase (hematite) and m phase (magnetite), m phase (magnetite) and w phase (wustite), w phase (wustite) and all iron (Fe) It has to do with phase. The same applies hereinafter.

The radius r ^(s/t) to the s/t interface in the above formula (5) can be obtained by the following formula (6).

上記式（６）において、ｒ^{（ｓ／ｔ）}は検討用焼結鉱（擬似球体）の中心からｓ／ｔ界面までの半径［ｍ］を示し、ｋ_ｃ ^{（ｓ／ｔ）}はｓ／ｔ界面の化学反応速度定数［ｍ／ｓ］を示し、ρ_ｏ ^（ｓ）はｓ相の被還元酸素の見掛けモル濃度［ｍｏｌＯ／ｍ^３］を示し、ρ_ｏ ^（ｔ）はｔ相の被還元酸素の見掛けモル濃度［ｍｏｌＯ／ｍ^３］を示し、Ｋ^{（ｓ／ｔ）}はｓ／ｔ界面の平衡定数を示し、Ｃ_Ｈ２ｉ ^{（ｓ／ｔ）}は界面における水素ガス濃度［ｍｏｌＨ_２／ｍ^３］を示し、Ｃ_Ｈ２ｅ ^{（ｓ／ｔ）}は界面における平衡水素ガス濃度［ｍｏｌＨ_２／ｍ^３］を示す。

In the above formula (6), r ^{(s / t)} represents the radius [m] from the center of the sintered ore for study (pseudo-sphere) to the s / t interface, and k _c ^{(s / t)} is s / t represents the chemical reaction rate constant [m/s] of the interface, ρ _o ^(s) represents the apparent molar concentration of s-phase reducible oxygen [molO/m ³ ], and ρ _o ^(t) represents the t-phase reducible indicates the apparent molar concentration of oxygen [molO/m ³ ], K ^(s/t) indicates the equilibrium constant of the s/t interface, and _CH2i ^(s/t) indicates the hydrogen gas concentration at the interface [molH ₂ /m ³ ] and C _H2e ^(s/t) indicates the equilibrium hydrogen gas concentration [molH ₂ /m ³ ] at the interface.

Here, the reducing gas may change its composition while passing through the sintered ore packed bed. Therefore, reducing gases having different compositions pass through the region of the sintered ore packed bed located on the upstream side of the flow of the reducing gas and the region of the sintered ore packed bed located on the downstream side of the flow of the reducing gas. There is Therefore, when estimating the reduction rate of the sintered ore packed bed for investigation, the reduction rate and the change in the composition of the reducing gas are estimated in a calculation cell located upstream of the flow of the reducing gas. In a computational cell located downstream, the reduction rate may be estimated using the composition of the reducing gas after the composition change.

Non-Patent Document 3, for example, can be used to estimate the reduction rate in consideration of changes in the composition of the reducing gas. A preferred method for determining the reduction rate in consideration of changes in the composition of the reducing gas is one-dimensional unsteady reaction rate analysis. A one-dimensional unsteady kinetic analysis is described, for example, in Non-Patent Document 4.

The method of estimating the composition change of the reducing gas in the sintered ore packed bed for investigation and obtaining the reduction rate of the sintered ore packed bed for investigation is not limited to one-dimensional unsteady reaction rate analysis. As another reduction reaction rate analysis method, for example, two-dimensional or three-dimensional unsteady reaction rate analysis may be performed. Also, the method of obtaining the reduction reaction rate of the sintered ore for investigation and estimating the reduction rate of each calculation cell is not limited to the three-interface unreacted nucleus model. As other reduction reaction models, a multi-stage reaction zone model, a grain model, or the like can be applied. Furthermore, even when using a one-dimensional unsteady reaction rate analysis or a three-interface unreacted nucleus model, applicable chemical reaction rate equations are not limited to those described above. Formulas may be used as appropriate.

(Shrinkage behavior of sintered ore packed bed)
In the processing of step S103 (shrinkage ratio calculation step), the shrinkage ratio of the sintered ore packed bed for investigation when the predetermined time t has elapsed is obtained for each calculation cell. The shrinkage rate of each computational cell after a predetermined time t has elapsed can be expressed as a time integral of the shrinkage rate of each computational cell. Therefore, if the shrinkage rate from when the sintered ore packed bed for investigation is formed in the blast furnace to when the predetermined time t has passed is obtained, the shrinkage rate of each calculation cell when the predetermined time t has passed can be estimated. can. In addition, since the sintered ore packed layer does not shrink in the temperature range until the reduction of the sintered ore starts, the shrinkage rate is The speed may be obtained by time integration.

The contraction behavior of the sintered ore packed bed has different controlling factors in the two temperature regions (region I and region II). Therefore, the contraction rate estimation formula can be determined separately for each of these temperature regions. When the temperature of the sintered ore packed bed for investigation is within the range of region I, the estimation formula for the shrinkage speed of each calculation cell can be expressed by formulas (7) to (8) described later. When the temperature of the sintered ore packed bed for investigation is within the range of region II, the estimation formula for the shrinkage rate of each calculation cell can be expressed by formulas (9) to (13) described later. The boundary temperature that separates the region I and the region II is the temperature at which the shrinkage rate of the sintered ore packed layer for investigation shows the maximum value, and the temperature region lower than the boundary temperature is defined as region I, and the temperature is lower than the boundary temperature. Region II is defined as a high temperature region.

In region I, the shrinkage speed of each computational cell can be obtained by the following formula (7). As shown in the following formula (7), in region I, the shrinkage speed 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 charged material).

上記式（７）において、ｄＳｒ_ｉ／ｄｔは所定時間ｔが経過するまでのｉ番目の計算セルの収縮速度［ｓ^－１］を示し、Ｓｒ_ｉは所定時間ｔが経過したときのｉ番目の計算セル全体の平均収縮率［－］を示し、Ｗは、所定時間ｔが経過したときの検討用焼結鉱充填層にかかる荷重［Ｐａ］を示し、ηは所定時間ｔが経過したときの検討用焼結鉱充填層に含まれる検討用焼結鉱の見かけの軟化粘度［Ｐａ・ｓ］を示す。

In the above formula (7), dSr _i /dt indicates the contraction speed [s ^-1 ] of the i-th calculation cell until the predetermined time t has passed, and Sr _i is the i-th cell when the predetermined time t has passed. Indicates the average shrinkage rate [-] of the entire calculation cell, W indicates the load [Pa] applied to the sintered ore packed bed for investigation when the predetermined time t has passed, and η indicates the load when the predetermined time t has passed. The apparent softening viscosity [Pa·s] of the sintered ore for investigation contained in the sintered ore packed bed for investigation is shown.

The apparent softening viscosity η in the above formula (7) can be obtained by the following formula (8).

上記式（８）において、ηは所定時間ｔが経過したときの検討用焼結鉱充填層に含まれる検討用焼結鉱の見かけの軟化粘度［Ｐａ・ｓ］を示し、η_０は定数［Ｐａ・ｓ］を示し、ｃ_１は係数［Ｋ］を示し、Ｔは所定時間ｔが経過したときの検討用焼結鉱充填層の温度［Ｋ］を示す。

In the above formula (8), η indicates the apparent softening viscosity [Pa s] of the sintered ore for investigation contained in the sintered ore packed bed for investigation when a predetermined time t has elapsed, and η ₀ is a constant [ Pa·s], _c1 indicates the coefficient [K], and T indicates the temperature [K] of the sintered ore packed bed for investigation after a predetermined time t has elapsed.

In the formula (8), the constant η ₀ and the coefficient c ₁ can be obtained in advance based on the formula (8) using, for example, the apparent softening viscosity η obtained by the load softening test. The load softening test simulates the temperature-programmed reduction behavior of the sinter packed bed in the blast furnace, and the load softening test described in Non-Patent Document 1 can be used.

In region II, the shrinkage speed of each computational cell can be obtained by the following formula (9). As shown in the following formula (9), in region II, the shrinkage rate is proportional to the melt generation rate. Moreover, as shown in the following formula (11), the coefficient β decreases as the volume ratio of metallic iron in the sintered ore packed bed for investigation increases. As can be understood from this point, in region II, the melt generation behavior and the aggregate effect of the generated metallic iron (the effect of inhibiting the shrinkage of the sintered ore packed bed by the metallic iron generated by the reduction of the sintered ore) is the main controlling factor that determines the shrinkage rate.

上記式（９）において、ｄＳｒ_ｉ／ｄｔは所定時間ｔが経過するまでのｉ番目の計算セルの収縮速度［ｓ^－１］を示し、Ｓｒ_ｉは、所定時間ｔが経過したときのｉ番目の計算セル全体の平均収縮率［－］を示し、βは係数［－］を示し、Ｍ_ＳＰはｉ番目の計算セルの検討用焼結鉱の初期質量［ｋｇ］を示し、Ｖ_０．ＳＰはｉ番目の計算セルの初期体積［ｍ^３］を示し、Ｖ_ｌｉｑは、所定時間ｔが経過するまでのｉ番目の計算セルにおける検討用焼結鉱１ｋｇ当たりの融液の生成量［ｍ^３／ｋｇ］を示す。

In the above formula (9), dSr _i /dt indicates the contraction speed [s ^-1 ] of the i-th calculation cell until the predetermined time t has passed, and Sr _i is the i-th calculation cell when the predetermined time t has passed. , β indicates the coefficient [-], M _SP indicates the initial mass [kg] of the sintered ore for investigation in the i-th calculation cell, and V _{0. SP} indicates the initial volume [m ³ ] of the i-th calculation cell, and V _liq indicates the amount of melt produced per 1 kg of the sintered ore for investigation in the i-th calculation cell until the predetermined time t has elapsed [m ³ /kg].

In the above formula (9), the initial volume V _{0 . SP} is the initial volume before shrinkage of each computational cell. Also, the initial mass M _SP of the sintered ore for investigation is the initial volume V _{0.0 of the i-th calculation cell.} It can be obtained from _SP , the volume ratio (1−ε _0i ) of the sintered ore for investigation in the i-th calculation cell, and the apparent density.

The melt generation amount V _liq in the above formula (9) can be obtained by the following formula (10).

上記式（１０）において、Ｖ_ｌｉｑは、所定時間ｔが経過したときのｉ番目の計算セルにおける検討用焼結鉱１ｋｇ当たりの融液の生成量［ｍ^３／ｋｇ］を示し、ｃ_２は、係数［ｍ^３／（ｋｇ・Ｋ）］を示し、ｃ_３は、係数［ｍ^３／ｋｇ］を示し、ｃ_４は、係数［ｍ^３／ｋｇ］を示し、Ｔは、所定時間ｔが経過したときの検討用焼結鉱充填層の温度［Ｋ］を示し、Ｒ_ｉは、所定時間ｔが経過したときのｉ番目のセルの還元率［－］を示す。

In the above formula (10), V _liq represents the amount of melt produced per 1 kg of sintered ore for study in the i-th calculation cell after a predetermined time t has elapsed [m ³ / kg], and c ₂ is , indicates the coefficient [m ³ /(kg K)], c ₃ indicates the coefficient [m ³ /kg], c ₄ indicates the coefficient [m 3 /kg], and T indicates the coefficient [m ³ /kg]. Shows the temperature [K] of the sintered ore packed bed for investigation when it has passed, and R _i shows the reduction rate [-] of the i-th cell when the predetermined time t has passed.

In the above formula (10), the coefficients c ₂ , c ₃ and c ₄ can be obtained in advance by thermodynamic equilibrium calculation (for example, by thermodynamic equilibrium calculation software Factsage). Specifically, if the thermodynamic equilibrium calculation is performed using the amount V _liq produced when the temperature T and the reduction rate _Ri are changed when the sintered ore for investigation is used, the temperature T and the reduction rate _Ri and the amount of production V _liq is obtained. Constants c ₂ , c ₃ , and c ₄ can be determined so that this relationship and the above equation (10) match.

The coefficient β in the above formula (9) can be obtained by the following formula (11).

上記式（１１）において、βは、係数［－］を示し、ｃ_５及びｃ_６は、係数［－］を示し、Ｘ_Ｆｅは、所定時間ｔが経過したときのｉ番目の計算セルの金属鉄の体積割合［－］を示す。上記式（１１）において、係数ｃ_５及びｃ_６は、高温性状試験（例えば、非特許文献１記載の高温性状試験）を行い、予め求めておくことができる。

In the above formula (11), β indicates the coefficient [-], c ₅ and c ₆ indicate the coefficient [-], X _Fe is the metal of the i-th calculation cell after a predetermined time t has passed Indicates the volume fraction of iron [-]. In the above formula (11), the coefficients _c5 and _c6 can be determined in advance by performing a high temperature property test (for example, the high temperature property test described in Non-Patent Document 1).

The volume ratio X _Fe of metallic iron in the above formula (11) can be obtained by the following formula (12).

上記式（１２）において、Ｘ_Ｆｅは、所定時間ｔが経過したときのｉ番目の計算セルの金属鉄の体積割合［－］を示し、Ｖ_Ｆｅは、所定時間ｔが経過したときのｉ番目の計算セルの金属鉄の体積［ｍ^３］を示し、Ｖ_0．SPは、ｉ番目の計算セルの初期体積［ｍ^３］を示し、Ｓｒ_ｉは、所定時間ｔが経過したときのｉ番目の計算セルの全体の平均収縮率Ｓｒ_ｉ［－］を示す。

In the above formula (12), X _Fe represents the volume ratio [-] of metallic iron in the i-th calculation cell after a predetermined time t has passed, and V _Fe represents the i-th cell after a predetermined time t has passed. represents the volume of metallic iron [m ³ ] in the computational cell of V _{0 . SP} indicates the initial volume [m ³ ] of the i-th computational cell, and Sr _i indicates the overall average shrinkage rate Sr _i [−] of the i-th computational cell after a predetermined time t has elapsed.

The volume V _Fe of metallic iron in the above formula (12) can be obtained by the following formula (13).

上記式（１３）において、Ｖ_Ｆｅは、所定時間ｔが経過したときのｉ番目の計算セルの金属鉄の体積［ｍ^３］を示し、Ｍ_ＳＰは、ｉ番目の計算セルの検討用焼結鉱の初期質量［ｋｇ］を示し、ρ_Ｆｅは、金属鉄の密度［ｋｇ／ｍ^３］を示し、Ｒ_ｉは、所定時間ｔが経過したときのｉ番目の計算セルの検討用焼結鉱の還元率［－］を示し、Ｔ．Ｆｅは、検討用焼結鉱中の総鉄量の初期割合［重量％］を示す。ここでは、軟化溶融時の検討用焼結鉱充填層における鉄の存在形態がＦｅ及びＦｅＯだけであると仮定し、上記式（１３）を規定している。

In the above formula (13), V _Fe indicates the volume [m ³ ] of metallic iron in the i-th calculation cell after a predetermined time t has elapsed, and M _SP is the study sintered volume of the i-th calculation cell. represents the initial mass of the ore [kg], ρ _Fe represents the density of metallic iron [kg/m ³ ], and _Ri represents the sintered ore for study in the i-th calculation cell after a predetermined time t has elapsed. shows the reduction rate [-] of T. Fe indicates the initial proportion [% by weight] of the total iron content in the sintered ore for investigation. Here, the above formula (13) is defined on the assumption that Fe and FeO are the only forms of iron in the sintered ore packed bed for investigation during softening and melting.

In the above formula (13), the initial proportion of the total iron content T. Fe can be obtained in advance.

η ₀ and c ₁ to c ₆ used in the above formulas (8), (10) and (11) can be determined according to properties such as the composition and pore structure of the sintered ore to be investigated. These coefficients do not change unless the type of the sintered ore for investigation is changed, and do not change depending on the change in the filling state of the sintered ore for investigation and the conditions related to the reducing gas.

η ₀ and c ₁ to c ₆ can be selected from the following ranges, for example.
η ₀ =6.0×10 ⁻¹⁷ to 3.0×10 ³
c ₁ =1.5×10 ⁴ to 9.0×10 ⁴
c ₂ =5.0×10 ⁻⁸ to 1.5×10 ⁻⁶
c ₃ =0.0 to 1.5×10 ⁻⁴
c ₄ =-1.0×10 ^-3 to -6.0×10 ^-5
_c5 = -40 to 0.0
c ₆ = 0.1-10

As described above, the shrinkage rate of each computational cell is expressed as the time integral of the shrinkage rate estimated by the above equations (7) and (9). Therefore, the value obtained by time-integrating the contraction speed estimated by the above formula (7) or the above formula (9) becomes the contraction rate of each calculation cell.

(Increase behavior of pressure loss accompanying layer shrinkage)
In the processing of step S104 (pressure loss calculation step), the pressure loss in the sintered ore packed bed for investigation when the predetermined time t has elapsed is obtained for each calculation cell. The pressure loss obtained in step S104 may be the pressure loss [Pa] generated in each calculation cell itself, or the pressure loss per unit length [Pa/m]. The pressure loss per unit length can be obtained based on the following formula (14) as an Ergun formula.

上記式（１４）において、ΔＰ／ΔＬは各計算セルで生じる単位長さあたりの圧力損失（圧力損失の勾配）［Ｐａ／ｍ］を示し、εは所定時間ｔが経過したときのｉ番目の計算セルの空隙率［－］を示し、ｄは所定時間ｔが経過したときのｉ番目の計算セルに含まれる検討用焼結鉱の調和平均粒径［ｍ］を示し、φはｉ番目の計算セルに含まれる検討用焼結鉱の形状係数を示し、形状係数φと調和平均粒径ｄを乗算したφｄは所定時間ｔが経過したときの検討用焼結鉱の有効径［ｍ］を示し、Ｕ［ｍ／ｓ］、μ［Ｐａ・ｓ］及びρ［ｋｇ／ｍ^３］のそれぞれは、所定時間ｔが経過したときの還元ガスの空塔流速、粘度及び密度を示す。

In the above formula (14), ΔP/ΔL indicates the pressure loss per unit length (gradient of pressure loss) [Pa/m] generated in each calculation cell, and ε is the i-th Indicates the porosity [-] of the calculation cell, d indicates the harmonic average particle size [m] of the sintered ore for investigation contained in the i-th calculation cell after the predetermined time t has elapsed, and φ indicates the i-th Shows the shape factor of the sintered ore for investigation contained in the calculation cell, and φd obtained by multiplying the shape factor φ by the harmonic average grain size d is the effective diameter [m] of the sintered ore for investigation after a predetermined time t has passed. U [m/s], μ [Pa·s] and ρ [kg/m ³ ] respectively indicate the superficial flow velocity, viscosity and density of the reducing gas after a predetermined time t has elapsed.

In the above formula (14), the effective diameter φd of the sintered ore for investigation when the predetermined time t has elapsed can be obtained from the formula (20) described later. Further, the superficial velocity U can be obtained by dividing the flow rate of the reducing gas after a predetermined time t has passed by the cross-sectional area of the calculation cell perpendicular to the direction in which the reducing gas flows. The flow patterns described above can be used. Further, the viscosity μ and the density ρ of the reducing gas can be obtained from a known function defined by the temperature and the composition of the reducing gas after a predetermined time t has elapsed. can be used.

The porosity ε in the above formula (14) can be obtained by the following formula (15).

上記式（１５）において、εは所定時間ｔが経過したときのｉ番目の計算セルの空隙率［－］を示し、αは係数［－］を示し、ε_０ｉはｉ番目の計算セルの初期空隙率［－］を示し、Ｓｒ_ｉは、所定時間ｔが経過したときのｉ番目の計算セル全体の平均収縮率［－］を示す。ここで、αＳｒ_ｉ及びε_０ｉは、式（１５）の括弧内の関係が成り立つ。

In the above formula (15), ε indicates the porosity [-] of the i-th calculation cell after the predetermined time t has passed, α indicates the coefficient [-], and ε _0i is the initial stage of the i-th calculation cell. Sr i indicates the porosity [-], and Sr _i indicates the average shrinkage [-] of the entire i-th computational cell after a predetermined time t has elapsed. Here, αSr _i and ε _0i satisfy the relationship in the parenthesis of Equation (15).

In Equation (15), the coefficient α indicates the ratio of the pore volume reduction amount to the total volume reduction amount during layer shrinkage, and depends on the amount of closed pores and the softening and melting properties of the sintered ore for investigation. Although the method of obtaining the coefficient α is not particularly limited, an example of obtaining it using an X-ray CT image analysis method will be described below.

FIG. 4 shows an overview of the method of analyzing an X-ray CT image. The crucible is filled with sintered ore for investigation, and the sintered ore for investigation is reduced while a reducing gas is circulated. A region in which only the sintered ore for investigation exists is specified from a crucible horizontal cross-sectional image obtained by X-ray CT imaging. For this region, a predetermined number of images are extracted at equal intervals in the height direction, and the porosity and apparent grain size are determined using each image. Specifically, the original image obtained by X-ray CT imaging is binarized, and the masking process is performed to extract only the sintered ore particles (image shown in (a) in FIG. 4) and the inside of the graphite crucible. is painted white (image shown in (b) in FIG. 4). For both images, the number of pixels in the black part, the number of pixels in the white part, and the number of pixels around the white part are counted, and the porosity of the sintered ore filling layer for examination and the firing for examination are calculated by formulas (16) to (19). Determine the apparent grain size of the ore. It should be noted that the particle size obtained from the horizontal cross-sectional image is π/4 times the actual size, assuming that the particles are spherical, so this can be corrected.

上記式（１６）～（１９）において、Ｓ´_{Ｓｏｌｉｄ}は固体領域画素数［ｐｉｘｅｌ］を示し、Ｓ_Ｖｏｉｄは空隙領域画素数［ｐｉｘｅｌ］を示し、Ｌ´_{Ｓｏｌｉｄ}は固体周囲画素数［ｐｉｘｅｌ］を示し、Ｓ_Ａはるつぼ外領域画素数［ｐｉｘｅｌ］を示し、Ｓ_Ｂはるつぼ内領域画素数［ｐｉｘｅｌ］を示し、Ｌ_０はるつぼ周囲画素数［ｐｉｘｅｌ］を示し、Ｄはるつぼ内径［ｍ］を示す。

In the above formulas (16) to (19), _S'Solid indicates the number of solid area pixels [pixel], S _Void indicates the number of void area pixels [pixel], and L' _Solid indicates the number of solid surrounding pixels [pixel]. , S _A indicates the number of pixels in the crucible outer region [pixel], _SB indicates the number of pixels in the crucible inner region [pixel], _L0 indicates the number of pixels around the crucible [pixel], and D is the inner diameter of the crucible [m]. indicates

The image analysis described above is performed on multiple sintered ore packed beds with different shrinkage ratios, and the porosity of the sintered ore packed bed for investigation at each shrinkage ratio and the apparent particle size of the sintered ore for investigation are calculated. (hereinafter referred to as "measured value"). In addition, using the X-ray CT image before the sintered ore for investigation softens and shrinks, the initial value of the porosity of the sintered ore packed bed for investigation and the apparent particle size of the sintered ore for investigation (hereinafter referred to as , called “initial value”). For each measured value of the porosity of the sintered ore packed bed for investigation obtained based on the analysis result of the X-ray CT image, the porosity of the sintered ore packed bed for investigation obtained based on the analysis result of the X-ray CT image is used to obtain the value of α that satisfies the above equation (15), and α is approximated by a linear expression of the shrinkage ratio Sr.

In the method described above, α is a function of the shrinkage ratio, but in a simple analysis, it may be a fixed value according to the brand of sintered ore for investigation. The coefficient α can be selected from, for example, the following range.
α = 0 to 1

Similarly, it is preferable to approximate each measured value of the apparent particle size obtained based on the analysis result of the X-ray CT image as a function of the shrinkage ratio Sr. The apparent grain diameter approximated as a function of the shrinkage ratio Sr can be used as the effective diameter φd of the sintered ore for investigation in the above formula (14). The effective diameter φd in the above formula (14) can be expressed by the following formula (20). In a simple analysis, it is not necessary to take into consideration the change in apparent grain size due to layer shrinkage. That is, in a simple analysis, the effective diameter φd of the sintered ore for investigation in the above formula (14) may be regarded as the initial effective diameter (φd) ₀ of the sintered ore for investigation.

上記式（２０）において、（φｄ）は所定時間ｔが経過したときの検討用焼結鉱の有効径［ｍ］を示し、（φｄ）_０は検討用焼結鉱の初期有効径［ｍ］を示し、Ｓｒ_ｉは、所定時間ｔが経過したときのｉ番目の計算セル全体の平均収縮率［－］を示し、γは定数［－］を示す。上記式（２０）における（φｄ）_０は、検討用焼結鉱の形状係数φに、検討用焼結鉱の初期調和平均粒径ｄ_０［ｍ］を乗じることで求めることができる。

In the above formula (20), (φd) indicates the effective diameter [m] of the sintered ore for investigation after a predetermined time t has elapsed, and (φd) ₀ is the initial effective diameter [m] of the sintered ore for investigation. , Sr _i indicates the average shrinkage rate [-] of the entire i-th computational cell after a predetermined time t has elapsed, and γ indicates a constant [-]. (φd) ₀ in the above formula (20) can be obtained by multiplying the shape factor φ of the sintered ore for investigation by the initial harmonic mean particle size d ₀ [m] of the sintered ore for investigation.

In the above formula (20), the value of the constant γ that satisfies the above formula (20) is set in advance for each actual measurement value of the apparent grain size of the sintered ore packed bed for investigation obtained based on the analysis result of the X-ray CT image. you can ask for it. When the value of the constant γ is obtained in advance, the effective diameter (φd) and the average shrinkage ratio _Sri in the above formula (20) are each determined based on the analysis results of the X-ray CT image. It is possible to use the actual measured value of the apparent grain size of the ore packed bed and the shrinkage ratio when the measured value _is obtained. Initial values can be used.

Note that the method for obtaining the pressure loss is not limited to the method using the above Ergun equation (14). For example, the method of correcting the coefficients of the inertia term in the Ergun equation as a function of the shrinkage ratio disclosed in Non-Patent Document 5, or other filling equations such as the orifice model-based estimation equation disclosed in Non-Patent Document 6. A layer pressure drop estimation formula can also be applied. In addition, the pressure loss (Pa) generated in each calculation cell is obtained by multiplying the pressure loss per unit length (Pa/m) obtained based on the above formula (14) by the length of the calculation cell in the layer height direction. can be obtained by

(Estimation of high temperature properties)
In the process of step S105, it is determined whether or not the pressure loss obtained 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 or not the pressure loss of the entire sintered ore packed bed for examination or the average value of the gradient of the pressure loss of the sintered ore packed bed for examination has reached a predetermined value. When the pressure loss reaches 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 step S102, and the processes of steps S102 to S104 are repeated. In the repeated processing of steps S102 to S104, the reduction rate, shrinkage rate, and pressure loss are estimated for each calculation cell when the calculation cycle Δt has elapsed.

In step S106 (high-temperature property estimation step), a reduction rate Rs ^* at the start of fusion bonding is obtained.

Rs ^* indicates the reduction rate of the sintered ore packed bed (ore layer) for investigation when the pressure loss occurring in the sintered ore packed bed (ore layer) rises to a predetermined value. Therefore, the average value of the reduction rate of each calculation cell when the pressure loss obtained in the process of step S104 indicates a predetermined value (that is, the reduction rate obtained in step S102) is obtained as the reduction rate Rs ^* at the start of fusion bonding. be done. Note that 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. The average value of the temperature (input condition) of each calculation cell of the sintered ore packed bed when showing is obtained as the fusion start temperature Ts ^* .

Using the Rs ^* estimation model described above, the reduction rate Rs ^* at the start of fusion bonding of the sintered ore packed bed for investigation can be obtained. The harmonic average grain size Dp corresponds to the initial grain size _d0 of the sintered ore for investigation.

As described above, the Rs ^* -Dp curve is obtained by inputting a plurality of types of input conditions that differ only in the harmonic average particle size Dp to the Rs ^* estimation model, and for each input condition at the start of fusion bonding of the sintered ore packed bed for investigation. The reduction rate Rs ^* is calculated, and the calculated reduction rate Rs ^* at the start of fusion bonding and the harmonic average particle size Dp used for calculating the reduction rate Rs ^* at the start of fusion are plotted on a graph. be able to.

In the Rs ^* -Dp curve, the reduction rate Rs ^* at the start of fusion can be approximated by a linear or quadratic expression of the harmonic mean particle diameter Dp. The Rs ^* -Dp curve is obtained as detailed below, eg as in FIG. 6c. FIG _. 6c shows two types of Rs ^* -Dp curves with an initial porosity ε ₀ of 0.38 or 0.40. can be represented.

上記式（２１）において、Ｒｓ^＊は検討用焼結鉱充填層の融着開始時還元率［％］を示し、Ｄｐは検討用焼結鉱の初期調和平均粒径［ｍｍ］を示し、ε_０は検討用焼結鉱充填層の初期空隙率［－］を示す。

In the above formula (21), Rs ^* indicates the reduction rate [%] at the start of fusion bonding of the sintered ore packed bed for investigation, Dp indicates the initial harmonic average particle size [mm] of the sintered ore for investigation, and ε ₀ indicates the initial porosity [-] of the sintered ore packed bed for investigation.

The range of the harmonic average particle diameter Dp for obtaining the Rs ^* -Dp curve, that is, the range of the harmonic average particle diameter Dp for calculating or measuring the reduction rate Rs ^* at the start of fusion bonding, is the charging powder whose particle size distribution is to be adjusted. Any range that includes the harmonic average particle size Dp of the sintered ore can be used, and can be appropriately set within a necessary range based on the range that can be used in actual operation. Depending on the range of the harmonic average particle size Dp, as illustrated in FIG. 6c, an Rs ^* -Dp curve showing the maximum value of the reduction rate Rs ^* at the start of fusion bonding at a certain harmonic average particle size Dp may be obtained. However, it is not limited to this, and a simple increasing or monotonically decreasing Rs ^* -Dp curve may be obtained.

As described above, even if the porosity and other properties are different between the charging sintered ore and the investigational sintered ore, the reduction rate Rs ^* at the start of fusion with respect to the change in the harmonic average particle size Dp Responses can be considered similar. Therefore, by using the Rs ^* -Dp curve, the amount of change ΔRs ^* in the reduction rate Rs ^* at the start of fusion for charging sinter ore whose particle size distribution is adjusted It is possible to estimate the difference between the reduction rate Rs ^* at the start of fusion for the ore and the reduction rate Rs ^* at the start of fusion for charging sinter ore before particle size distribution adjustment. In this specification, the reduction rate Rs ^* at the start of fusion of sintered ore refers to the reduction rate Rs ^* at the start of fusion of a sintered ore packed bed made of the sintered ore.

In the adjustment method of the present embodiment, the reference value S is the harmonic average particle size Dp at which the reduction rate Rs ^* at the start of fusion bonding in the Rs ^* -Dp curve is the maximum value. The maximum value may be the maximum value of the reduction rate Rs ^* at the start of fusion in the acquired Rs ^* -Dp curve, and does not necessarily have to be the maximum value. From the viewpoint of further increasing the reduction rate Rs ^* at the start of fusion for charging sinter ore whose particle size distribution is to be adjusted, the maximum value is preferably a maximum value.

Here, the response of the reduction rate Rs ^* at the start of fusion bonding to the change in the harmonic average grain size Dp between the charging sintered ore and the investigational sintered ore is considered to be the same, and the particle size distribution is to be adjusted. The target for approximating the harmonic average particle size Dp of the sintered ore for charging is the harmonic average particle size Dp (that is, the reference value S) at which the reduction rate Rs ^* at the start of fusion in the Rs ^* -Dp curve becomes the maximum value. . For this reason, the closer the harmonic average particle diameter Dp of the charged sintered ore whose particle size distribution is adjusted to the reference value S, the reduction rate at the start of fusion bonding for the charged sintered ore whose particle size distribution is adjusted. Rs ^* can be increased. If there is no change in the blending ratio of the charging sintered ore contained in the ore layer, the charging sintered ore is used as the reduction rate Rs ^* at the start of fusion bonding of the charging sintered ore increases. The reduction rate Rs ^* at the start of fusion of the ore layer that has been formed increases. Therefore, according to the present embodiment for adjusting the particle size distribution of the charging sintered ore so as to satisfy the first condition, the reduction rate at the start of fusion for the charging sintered ore whose particle size distribution is to be adjusted Rs ^* can be increased. As a result, the reduction rate Rs ^* at the start of fusion bonding of the ore layer formed using the sintered ore can be increased.

Note that the reduction rate Rs* at the start of fusion of the ore layer is obtained by calculating the reduction rate ^{Rs *} at the start of fusion of the packed bed (ore layer made of one type of ore raw material) for each type of ore raw material forming the ore layer. The obtained reduction rate Rs ^* at the start of fusion bonding of the packed bed can be obtained by taking a weighted average according to the blending ratio [% by mass] of the ore raw material forming the packed bed in the ore layer. Here, the Rs ^* estimation model described above can be used to obtain the reduction rate Rs ^* at the start of fusion bonding of the packed bed for each type of ore raw material forming the ore layer. Specifically, by using conditions that are the same as or similar to the packed state of the packed bed as the conditions (a) used as input conditions, the reduction rate Rs ^* at the start of fusion bonding of each packed bed can be obtained. can.

^As described above, the reduction rate Rs ^* at the start of fusion bonding represents the reduction rate when the ore fusion layer is formed. It means that the reduction rate is increased when (and fusion) to form an ore fusion layer. That is, it means that the reduction rate by indirect reduction (exothermic reaction) until the ore cohesive layer is formed increases, and the reduction rate by direct reduction (endothermic reaction) in the lower part of the furnace decreases. Therefore, if the reduction rate Rs ^* at the start of fusion bonding of the ore layer increases, the amount of heat absorbed in the lower part of the furnace decreases (the amount of endothermic reaction decreases), and the dripping of hot metal is promoted. As a result, the area of the cohesive zone is reduced, and the in-furnace gas (reducing gas) can easily pass through the ore cohesive layer. Therefore, according to the adjustment method of the present embodiment, which can increase the reduction rate Rs ^* at the start of fusion for charging sintered ore whose particle size distribution is to be adjusted, the ore layer formed using the sintered ore melts. Since the reduction rate Rs ^* at the start of deposition increases, the reduction efficiency and air permeability in the furnace can be improved, and the reducing agent ratio can be reduced. In addition, the coke ratio can be reduced and the tapping ratio can be increased.

In the adjustment method of this embodiment described above, the particle size distribution of the charging sintered ore may be adjusted so as to satisfy the first condition, and other conditions are not particularly limited.

In the adjustment method of the present embodiment, from the viewpoint of further increasing the reduction rate Rs ^* at the start of fusion bonding of the sintered ore to be charged, the particle size distribution of which is to be adjusted, in addition to the first condition, the following second condition It is preferable to adjust the particle size distribution so as to satisfy the following conditions.

The second condition is that the initial porosity ∈ ₀ is increased by adjusting the particle size distribution. In other words, the second condition is that when the charging sintered ore packed layer is formed with the charging sintered ore after the particle size distribution is adjusted, the charging sintered ore is better than the charging sintered ore before the particle size distribution is adjusted. , the initial porosity _ε0 of the sintered ore packed bed for charging is high. The initial porosity _ε0 indicates the porosity immediately after the sintered ore packed bed is formed (the porosity of the sintered ore packed bed immediately after charging the sintered ore for charging into the blast furnace).

Here, the high initial porosity ε ₀ means that the initial stage of the sintered ore packed bed for charging actually formed in a blast furnace or an experimental apparatus simulating a blast furnace (for example, the high-temperature property test apparatus shown in Non-Patent Document 1) A concept that does not only mean that the porosity ε ₀ is increased, but also includes that the initial porosity ε ₀ of the sintered ore packed bed for charging predicted from the particle size distribution of the sintered ore for charging is increased. is. The method for predicting the initial porosity ε ₀ of the sintered ore packed bed for charging from the particle size distribution of the sintered ore for charging is not particularly limited, but for example, the following described in Non-Patent Document 2: A method of prediction based on equation (22) can be used.

上記式（２２）において、ε_ｊは装入用焼結鉱充填層の初期空隙率ε_０［－］を示し、β_ｊは、比例定数を示し［－］、ｍは、装入用焼結鉱充填層に含まれる異なる粒径の粒子の種類の数［－］を示し、Ｓ_ｋは、接触粒子ｋの体積基準の混合分率Ｓ_ａｋを考慮した指数［－］を示し、ε（ｊ，ｋ）は、部分的な空間率［－］を示す。ｍは例えば、装入用焼結鉱の粒度分布を複数の粒径範囲に区切ったときの粒径範囲の個数である。

In the above formula (22), ε _j indicates the initial porosity ε ₀ [-] of the sintered ore packed bed for charging, β _j indicates a proportional constant [-], and m is the sinter for charging. represents the number [-] of types of particles with different particle diameters contained in the ore packed bed, S _k represents the index [-] considering the volume-based mixture fraction S _ak of contact particles k, and ε(j , k) denotes the partial space ratio [-]. m is, for example, the number of particle size ranges when the particle size distribution of the sintered ore for charging is divided into a plurality of particle size ranges.

In the adjustment method of the present embodiment, in order to adjust the particle size distribution so as to satisfy the first condition and the second condition, for example, a particle size distribution that satisfies the first condition and the second condition is designed, A method can be used in which the particle size distribution of the sintered ore to be charged, whose particle size distribution is to be adjusted, matches the designed particle size distribution.

Formula (22) above, for example, can be used to design a particle size distribution that satisfies the first and second conditions. Specifically, first, the initial porosity ε ₀ when the sintered ore packed bed for charging is formed from the sintered ore for charging whose particle size distribution is to be adjusted (hereinafter referred to as “initial porosity ε ₀ before adjustment ”) is obtained based on the above equation (22). Next, provisionally design a particle size distribution such that the harmonic average particle diameter Dp of the charging sintered ore to be adjusted for the particle size distribution approaches the reference value S, and use the charging sintered ore with the provisionally designed particle size distribution The initial porosity ε ₀ (hereinafter also referred to as “temporary design initial porosity ε ₀ ”) when the sintered ore packed bed for charging is formed is obtained based on the above equation (22). Finally, from among the provisionally designed particle size distributions, a particle size distribution in which the provisional design initial porosity ε ₀ is higher than the pre-adjustment initial porosity ε ₀ is specified, and the specified particle size distribution (provisional design particle size distribution) is A particle size distribution that satisfies the first condition and the second condition is determined (designed).

In addition, in the design of the particle size distribution described above, the provisional design of the particle size distribution is performed, but the provisional design does not necessarily have to be performed. The initial porosity ε ₀ of the sintered ore packed bed for charging is used to reduce the proportion of coarse-grained sintered ore exceeding a predetermined particle size (e.g., 50 mm), It can be increased by decreasing the ratio of sintered ore. If a means for increasing such an initial porosity ε ₀ is specified in advance, and the means is used to design a particle size distribution in which the harmonic mean particle size Dp of the charged sintered ore approaches the reference value S , in the designed particle size distribution, as the harmonic mean particle size Dp approaches the reference value S, the initial porosity ε ₀ increases. In other words, a particle size distribution that satisfies the first condition and the second condition can be designed without provisionally designing the particle size distribution.

The method of adjusting the particle size distribution of the charging sintered ore so as to satisfy the first condition and the second condition is not limited to the above-described method, and charging without designing the particle size distribution The particle size distribution of the sintered ore for use may be adjusted. For example, if the particle size distribution is adjusted so that the harmonic average particle size Dp of the charged sintered ore approaches the reference value S using a means capable of increasing the initial porosity ε ₀ , the adjustment of the particle size distribution is performed in the first and the second condition are satisfied.

The reduction rate Rs ^* at the start of fusion bonding of the sintered ore packed bed for charging increases as the initial porosity _ε0 of the sintered ore packed bed for charging increases. Therefore, according to the present embodiment in which the particle size distribution of the charging sintered ore is adjusted so as to satisfy the first condition and the second condition, the particle size distribution is adjusted so as to satisfy only the first condition. The reduction rate Rs ^* at the start of fusion bonding for the charged sinter ore whose particle size distribution is to be adjusted can be further increased compared to the case where the particle size distribution is adjusted.

In addition, in the adjustment method of the present embodiment, when the harmonic mean particle diameter Dp at which the reduction rate Rs ^* at the start of fusion bonding in the Rs ^* -Dp curve is the maximum value is set as the reference value S, the first condition and the second condition are used. In addition to the conditions, it is preferable to adjust the particle size distribution so as to satisfy the third condition or the fourth condition shown below.

The third condition is that when the harmonic average particle size Dp of the charging sinter ore whose particle size distribution is to be adjusted exceeds the reference value S, the charging sinter ore after adjusting the particle size distribution The condition is that the harmonic mean particle size _Dpa is set to the reference value S or more. In addition, the fourth condition is that when the harmonic average particle size Dp of the charging sinter ore whose particle size distribution is to be adjusted is less than the reference value S, the charging sinter ore after adjusting the particle size distribution The condition is that the harmonic average particle diameter _Dpa of the particles is set to the reference value S or less.

In the adjustment method of the present embodiment, when adjusting the particle size distribution so as to satisfy the third and fourth conditions in addition to the first and second conditions, the following formula (2) and formula Based on (3), the amount of change ΔRs ^* in the reduction rate Rs ^* at the start of fusion for charging sinter whose particle size distribution is adjusted It is possible to estimate the difference between the time reduction rate Rs ^* and the reduction rate Rs ^* at the start of fusion for the charging sintered ore before adjusting the particle size distribution.

In addition to the first and second conditions, when the particle size distribution is adjusted to satisfy the third condition, the reduction rate Rs The amount of change ΔRs ^* of ^* (the amount of change ΔRs ^* before and after adjustment of the particle size distribution) can be estimated by the following formula (2).

上記式（２）において、ΔＲｓ^＊は、粒度分布の調整前後における装入用焼結鉱に関する融着開始時還元率Ｒｓ^＊の変化量［％］を示し、Ｃ_１は、検討用焼結鉱の調和平均粒径Ｄｐが基準値Ｓ以上の範囲内における、検討用焼結鉱の調和平均粒径Ｄｐに対する検討用焼結鉱の融着開始時還元率Ｒｓ^＊の変化率［％／ｍｍ］を示し、ΔＤｐは、粒度分布の調整前後における装入用焼結鉱の調和平均粒径Ｄｐの変化量［ｍｍ］を示し、Ｄ_１は、検討用焼結鉱の初期空隙率ε_０に対する検討用焼結鉱の融着開始時還元率Ｒｓ^＊の変化率［％／－］を示し、Δε_０は、粒度分布の調整前後における装入用焼結鉱に関する初期空隙率ε_０の変化量［－］を示す。なお、本明細書において、焼結鉱に関する初期空隙率ε_０とは、その焼結鉱からなる焼結鉱充填層の初期空隙率ε_０を指す。

In the above formula (2), ΔRs ^* indicates the amount of change [%] in the reduction rate Rs ^* at the start of fusion bonding for the charging sintered ore before and after adjusting the particle size distribution, and _C1 is the study sintered ore. The rate of change in the reduction rate Rs ^* at the start of fusion bonding of the sintered ore under study with respect to the harmonic average particle size Dp of the sintered ore under investigation [%/mm] , where ΔDp indicates the amount of change [mm] in the harmonic average particle diameter Dp of the sintered ore for charging before and after adjusting the particle size distribution, and _D1 is the initial porosity _ε of the sintered ore for investigation. represents the rate of change [%/−] of the reduction rate Rs ^* at the start of fusion bonding of the sintered ore for use, and Δε ₀ is the amount of change in the initial porosity ε ₀ of the sintered ore charged before and after adjusting the particle size distribution [ -] is shown. In addition, in this specification, the initial porosity ε ₀ of the sintered ore refers to the initial porosity ε ₀ of the sintered ore packed bed made of the sintered ore.

The change rate _C1 in the above formula (2) is obtained by dividing the amount of change in the reduction rate Rs ^* at the start of fusion bonding in the range where the harmonic average particle size Dp is equal to or greater than the reference value S by the amount of change in the harmonic average particle size Dp. and corresponds to the slope of the Rs ^* -Dp curve in the range where the harmonic mean particle diameter Dp is equal to or greater than the reference value S. Therefore, the slope of the Rs ^* -Dp curve (the slope in the range where the harmonic mean particle size Dp is equal to or greater than the reference value S) can be used as the rate of change _C1 . If the slope of the Rs ^* -Dp curve changes in the range where the harmonic mean particle size Dp is equal to or greater than the reference value S, the average value of the slope may be used as the rate of change _C1 .

Here, the slope of one Rs ^* -Dp curve may be used for the change rate _C1 , but the average of the slopes of two or more Rs ^* -Dp curves obtained using different initial porosities _ε0 is preferably used, and it is more preferable to use the average value of the slopes of the two Rs ^* -Dp curves obtained using two different initial porosities ε ₀ for the sintered ore for charging before and after adjusting the particle size distribution. . If the initial porosity ε ₀ input to the Rs ^* estimation model is different, the slopes of the obtained Rs ^* -Dp curves may be different from each other. Therefore, by using the average value of the slopes of two or more Rs ^* -Dp curves obtained by inputting different initial porosities _ε0 as the rate of change _C1 , the amount of change ΔRs ^* can be predicted more accurately. .

The rate of change _D1 in the above formula (2) is a value obtained by dividing the amount of change in the reduction rate Rs ^* at the start of fusion bonding by the amount of change in the initial porosity _ε0 . It can be determined using two Rs ^* -Dp curves obtained using ₀ . For the two Rs ^* -Dp curves, it is preferable to use two Rs ^* -Dp curves obtained using two different initial porosities ε ₀ for the charging sintered ore before and after adjusting the particle size distribution. Specifically, the difference in the initial porosity ε ₀ used to obtain the two Rs ^* -Dp curves (hereinafter also referred to as the “initial porosity ε ₀ difference”), and the two Rs ^* -Dp curves It can be obtained by obtaining the difference in reduction rate Rs ^* at the start of fusion bonding (hereinafter also referred to as "Rs ^* difference") and dividing the obtained Rs ^* difference by the initial porosity _ε0 difference. Here, the Rs ^* difference is the difference in Rs ^* corresponding to any harmonic average particle diameter Dp, and the average value of the differences in two or more Rs ^* corresponding to two or more harmonic particle diameters Dp is used. can be

Note that the rate of change _D1 in the above formula (2) may be obtained from a plurality of Rs ^* -Dp curves as described above, or may be the slope of the Rs ^* _-ε0 curve. Here, the Rs ^* _-ε0 curve is obtained by inputting a plurality of types of input conditions that differ only in the initial porosity _ε0 into the Rs ^* estimation model described above, and calculating the reduction rate Rs ^* at the start of fusion bonding, This curve is obtained by plotting the initial porosity ε ₀ used to calculate the reduction rate Rs ^* at the start of fusion bonding. Note that when the slope of the Rs ^* _-ε0 curve changes, the average value of the slope may be used as the rate of change _D1 . In addition, the slope of one Rs ^* _-ε0 curve may be used for the rate of change _D1 , or the slopes of two or more Rs ^* _-ε0 curves obtained by inputting different harmonic average particle diameters Dp. An average value may be used.

The rate of change C ₁ and the rate of change D ₁ in the above formula (2) may differ depending on the input conditions of the Rs ^* estimation model and the reference value S, and cannot be uniquely determined. C ₁ can be -1.2 and D ₁ can be 150.

On the other hand, when the particle size distribution is adjusted so as to satisfy the fourth condition in addition to the first and second conditions, the reduction at the start of fusion for the charging sinter ore whose particle size distribution is to be adjusted The amount of change ΔRs ^* in the ratio Rs ^* (the amount of change ΔRs ^* before and after the adjustment of the particle size distribution) can be obtained by the following formula (3).

上記式（３）において、ΔＲｓ^＊は、粒度分布の調整前後における装入用焼結鉱に関する融着開始時還元率Ｒｓ^＊の変化量［％］を示し、Ｃ_２は、検討用焼結鉱の調和平均粒径Ｄｐが基準値Ｓ以下の範囲内における、検討用焼結鉱の調和平均粒径Ｄｐに対する検討用焼結鉱の融着開始時還元率Ｒｓ^＊の変化率［％／ｍｍ］を示し、ΔＤｐは、粒度分布の調整前後における装入用焼結鉱の調和平均粒径Ｄｐの変化量［ｍｍ］を示し、Ｄ_２は、検討用焼結鉱の初期空隙率ε_０に対する検討用焼結鉱の融着開始時還元率Ｒｓ^＊の変化率［％／－］を示し、Δε_０は、粒度分布の調整前後における装入用焼結鉱に関する初期空隙率ε_０の変化量［－］を示す。

In the above formula (3), ΔRs ^* indicates the amount of change [%] in the reduction rate Rs ^* at the start of fusion for charging sintered ore before and after adjustment of the particle size distribution, and _C2 is the study sintered ore. The rate of change in the reduction rate Rs ^* at the start of fusion bonding of the sintered ore under study with respect to the harmonic average particle size Dp of the sintered ore under study [%/mm] , where ΔDp is the amount of change [mm] in the harmonic average particle size Dp of the charging sinter ore before and after adjusting the particle size distribution, and _D2 is the initial porosity _ε of the sinter ore for investigation. represents the rate of change [%/−] of the reduction rate Rs ^* at the start of fusion bonding of the sintered ore for use, and Δε ₀ is the amount of change in the initial porosity ε ₀ of the sintered ore charged before and after adjusting the particle size distribution [ -] is shown.

The rate of change _C2 in the above formula (3) is obtained by dividing the amount of change in the reduction rate Rs ^* at the start of fusion within the range where the harmonic mean particle size Dp is equal to or less than the reference value S by the amount of change in the harmonic mean particle size Dp. and corresponds to the slope of the Rs ^* -Dp curve in which the harmonic mean particle diameter Dp is within the range of the reference value S or less. Therefore, the slope of the Rs ^* -Dp curve (the slope within the range where the harmonic mean particle diameter Dp is equal to or lower than the reference value S) can be used as the rate of change _C2 . If the slope of the Rs ^* -Dp curve changes within the range where the harmonic mean particle size Dp is equal to or less than the reference value S, the average value of the slope may be used as the rate of change _C2 .

The slope of one Rs ^* -Dp curve may be used for the rate of change _C2 , but from the viewpoint of being able to predict the amount of change ΔRs ^* more accurately, two values obtained using different initial porosities _ε0 It is preferable to use the average value of the slopes of the above Rs ^* -Dp curves, and two Rs ^* -Dp curves obtained using two different initial porosities ε ₀ for the sintered ore for charging before and after adjusting the particle size distribution. It is more preferable to use the average value of the slope of

The rate of change _D2 in the above formula (3) is synonymous with the rate of change _D1 in the above formula (2), and the method of obtaining it is also the same as the rate of change _D1 . Therefore, description of the rate of change _D2 is omitted.

The rate of change C ₂ and the rate of change D ₂ in the above formula (3) may differ depending on the input conditions of the Rs ^* estimation model and the reference value S, and cannot be uniquely determined. _C2 can be 1.2 and _D2 can be 150.

As described above, in the embodiment in which the amount of change ΔRs ^* is considered using equations (2) and (3), it is necessary to satisfy the third and fourth conditions. However, if the amount of change ΔRs ^* is not considered using formulas (2) and (3), it is not necessary to satisfy the third condition and the fourth condition, and the harmonic average particle diameter Dp exceeding the reference value S However, the particle size distribution may be adjusted to be less than the reference value S, or the harmonic mean particle diameter Dp less than the reference value S may exceed the reference value S by the particle size distribution adjustment. In addition, when the harmonic average particle diameter Dp exceeding the reference value S becomes less than the reference value S due to the adjustment of the particle size distribution, or the harmonic average particle diameter Dp less than the reference value S exceeds the reference value S due to the adjustment of the particle size distribution can consider the amount of change ΔRs ^* by using, for example, the quadratic expression of the above-described equation (21).

In addition, in the adjustment method of the present embodiment, when the harmonic mean particle diameter Dp at which the reduction rate Rs ^* at the start of fusion on the Rs ^* -Dp curve is the maximum value is set as the reference value S, the first condition must be satisfied. In addition, the particle size distribution is adjusted so that the condition (fifth condition) that the harmonic average particle size _Dpa of the sintered ore for charging after adjusting the particle size distribution satisfies the following formula (1) is preferred.

上記式（１）において、Ｓは、基準値［ｍｍ］を示し、Ｄｐ_ａは、粒度分布を調整した後の装入用焼結鉱の調和平均粒径［ｍｍ］を示す。

In the above formula (1), S represents the reference value [mm], and _Dpa represents the harmonic mean particle size [mm] of the charging sinter ore after adjusting the particle size distribution.

In the Rs ^* -Dp curve described above, the range of ±2 [mm] with respect to the harmonic average particle size Dp at which the reduction rate Rs ^* at the start of fusion bonding is the maximum value is compared to the case outside the range. , the reduction rate Rs ^* at the start of fusion tends to exhibit a higher value. For this reason, when the harmonic mean particle size Dp at which the reduction rate Rs ^* at the start of fusion bonding in the Rs ^* -Dp curve is the maximum value is set as the reference value S, the sintered ore for charging after adjusting the particle size distribution When the harmonic average particle diameter _Dpa satisfies the above formula (1), the reduction rate Rs ^* at the start of fusion bonding for the sintered ore to be charged, the particle size distribution of which is to be adjusted, can be further increased. The ratio is likely to be further reduced.

EXAMPLES Next, the present invention will be described more specifically with reference to Examples. However, the present invention is not limited only to these examples.

Evaluation 1 (Influence of Harmonic Average Particle Size Dp and Initial Porosity _ε0 on Reduction Rate Rs ^* at Start of Fusion)
Analysis was performed using the Rs ^* estimation model under the following analysis conditions, and the effects of the harmonic mean particle size Dp and the initial porosity _ε0 on the reduction rate Rs ^* at the start of fusion bonding were evaluated.

In this analysis, the apparent density of the sintered ore packed bed for investigation was set to 3485 kg/m ³ . The sintered ore packed layers for investigation are all formed of sintered ore for investigation with the same particle size, and the particle size (harmonic average particle size Dp) of the sintered ore for investigation is 10, 12, 14, Set to 16, 18, 20, 22, 24 or 26 mm. The initial porosity of the sintered ore packed bed for investigation was set to 0.38 or 0.40 in consideration of the particle size distribution (base condition I and base condition II) of evaluation 2 described later. For the temperature rise, load pattern, and reducing gas composition, the temperature rise pattern shown in FIG. 5a, the composition pattern (CO/(CO+CO ₂ )) shown in FIG. 5b, and the load pattern shown in FIG. 5c were used. For the flow rate of the reducing gas, set the bosh gas flow rate obtained from past operation results, and for the flow rate of the reducing gas, the value obtained 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 ( 0.82 Nm/s) was set. The furnace pressure was assumed to be constant at 2.7 atm (0.27 MPa). The shape factor was obtained from the grain size (harmonic mean grain size) of the sintered ore for investigation based on Non-Patent Document 2. The softening shrinkage parameters (η ₀ , c ₁ to c ₆ , α) were selected and set from the ranges described above. The layer height was set to 300 mm.

One layer of the sintered ore packed bed for investigation was partitioned into a plurality of calculation cells arranged in the bed height direction. The calculation cell was 1 mm in the layer height direction. The calculation period Δt was set to 5 seconds, and the estimation of the reduction rate, shrinkage rate, and pressure loss was repeated by the above-described method until the pressure loss gradient of the entire sintered ore packed bed for investigation reached 50 kPa/m. The reduction rate (reduction rate of sintered ore) of each calculation cell when the pressure loss reached 50 kPa/m was averaged to obtain the reduction rate Rs ^* at the start of fusion bonding. In this analysis, the temperature of each calculation cell was obtained when the gradient of the pressure loss reached 50 kPa/m, 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 for investigation reaches 1200 ° C. (reduction rate of the sintered ore for investigation) is also obtained, and these reduction rates are averaged to obtain the reduction rate. Acquired as _R1200 .

The analysis results are shown in FIGS. 6a-6c.

FIG. 6a is a graph showing the relationship between the fusion initiation temperature Ts ^* and the harmonic average grain size Dp, showing two curves with an initial porosity _ε0 of 0.38 or 0.40. As shown in FIG. 6a, when the harmonic average particle size Dp of the sintered ore for investigation is in the range of 22 to 26 mm, the pressure loss increases as the harmonic average particle size Dp decreases and layer shrinkage is suppressed by promoting reduction. This was offset, and the fusion initiation temperature Ts ^* hardly increased or decreased. On the other hand, when the harmonic average particle diameter Dp was lower than 22 mm, the influence of pressure drop increase increased, and the fusion initiation temperature Ts ^* decreased. Also, when the initial porosity ε ₀ decreased by 0.02, Ts ^* decreased by 8 to 15°C.

FIG. 6b is a graph showing the relationship between the reduction rate R ₁₂₀₀ and the harmonic mean particle size Dp, showing two curves with an initial porosity ε ₀ of 0.38 or 0.40. As shown in FIG. 6b, the reduction rate R ₁₂₀₀ increased almost linearly with decreasing harmonic mean particle size Dp. On the other hand, even if the initial porosity _ε0 decreased by 0.02, the reduction ratio _R1200 hardly changed.

FIG. 6c is a graph showing the relationship between the reduction rate Rs ^* at the start of fusion bonding and the harmonic average particle diameter _Dp , and shows two types of curves (Rs ^* - Dp curve). As shown in FIG. 6c, when the harmonic average particle size Dp is in the range of 12 to 26 mm, the reduction rate Rs ^* at the start of fusion increases as the harmonic average particle size Dp decreases. It took the maximum value and turned to decrease slightly at 10 mm. From this result, in the sintered ore with a harmonic average particle size Dp larger than 12 mm, the effect of reduction promotion due to the decrease in the harmonic average particle size Dp is large, and in the sintered ore with a harmonic average particle size Dp smaller than 12 mm, the harmonic average It has been clarified that the decrease in the particle size Dp has a large effect on the increase in pressure loss. That is, it was found that the reduction rate Rs ^* at the start of fusion bonding can be increased by adjusting the particle size distribution of the sintered ore to be charged so that the harmonic average particle size Dp approaches 12 mm.

Further, as shown in FIG. 6c, when the initial porosity _ε0 decreased by 0.02, the reduction rate Rs ^* at the start of fusion decreased by 1.5 to 4.2%. From this result, it was clarified that the reduction rate Rs ^* at the start of fusion bonding can be increased by adjusting the particle size distribution of the charged sintered ore so as to increase the initial porosity ε ₀ .

Further, from the Rs ^* -Dp curve shown in FIG. 6c, the amount of change ΔRs ^* in the reduction rate Rs ^* at the start of fusion bonding is calculated using the amount of change ΔDp _in the harmonic mean particle diameter Dp and the amount of change _Δε0 in the initial porosity ε0. As a result, it has become clear that the following formulas (23) and (24) can be used. The amount of change ΔRs ^* in the following formula (23) is adjusted so that the particle size distribution of the charging sintered ore having a harmonic average particle size Dp exceeding 12 mm is adjusted so that the harmonic average particle size Dpa after adjusting the particle size distribution is 12 mm or more. The amount of change ΔRs ^* in the following formula (24) is the particle size distribution of the charging sintered ore having a harmonic average particle size Dp of less than 12 mm, and the harmonic average particle size after adjusting the particle size distribution. The amount of change when the diameter Dpa is adjusted to 12 mm or less is shown.

上記式（２３）及び上記式（２４）において、ΔＲｓ^＊は、粒度分布の調整前後における装入用焼結鉱に関する融着開始時還元率Ｒｓ^＊の変化量［％］を示し、ΔＤｐは、粒度分布の調整前後における装入用焼結鉱の調和平均粒径Ｄｐの変化量［ｍｍ］を示し、Δε_０は、粒度分布の調整前後における装入用焼結鉱に関する初期空隙率ε_０の変化量［－］を示す。

In the above formula (23) and the above formula (24), ΔRs ^* indicates the amount of change [%] in the reduction rate Rs ^* at the start of fusion bonding regarding the charging sintered ore before and after adjusting the particle size distribution, and ΔDp is Shows the amount of change [mm] in the harmonic average particle size Dp of the charging sintered ore before and after adjusting the particle size distribution, and Δε ₀ is the initial porosity ε ₀ of the charging sintered ore before and after adjusting the particle size distribution. Indicates the amount of change [-].

In the above formula (23), the coefficient −1.2 [%/mm] multiplied by the amount of change ΔDp is the slope of the two types of Rs ^* -Dp curves in the range where the harmonic average particle diameter Dp is 12 mm or more. Average value. In the above formula (24), the coefficient +1.2 [%/mm] multiplied by the change amount ΔDp is the average of the slopes of the two types of Rs ^* -Dp curves in the range where the harmonic average particle size Dp is 12 mm or less. value. In addition, in the above formulas (23) and (24), the coefficient 150 [%/-] multiplied by the amount of change Δε ₀ is the Rs ^* difference (1.5 to 4.2%) between the two Rs ^* -Dp curves. is a value obtained by dividing the average value of by the initial porosity ε ₀ difference (0.02) used to obtain two types of Rs ^* -Dp curves.

Evaluation 2 (change in reduction rate Rs ^* at the start of fusion bonding due to adjustment of particle size distribution)
For each of the sintered ore for charging having the particle size distribution of the base condition I and the base condition II shown in Table 1 below, the initial porosity ε ₀ when the sintered ore packed bed for charging is formed is calculated by the above formula (22 ), and the harmonic average particle diameter Dp was determined from the above formula (4).

Regarding the sintered ore for charging under the base condition I, since the harmonic average particle diameter Dp is larger than 12 mm, by excluding coarse particles, the harmonic average particle diameter Dp approaches 12 mm and the initial porosity ε ₀ expected to rise. Therefore, regarding the sintered ore for charging under the base condition I in which coarse particles are excluded (excluding coarse particles shown in Table 1), based on the above formulas (22) and (4), when the sintered ore packed layer is formed The initial porosity ε ₀ was determined, and the harmonic mean particle size Dp was determined. As shown in Table 1, by eliminating coarse particles with a particle size of more than 40 mm and roughly halving coarse particles with a particle size of more than 25 mm to 40 mm or less, the harmonic average particle size Dp is reduced by 1.28 mm, and the initial The porosity _ε0 increased by 0.0045. Substituting the variation Δε 0 (0.0045) in the initial porosity ε ₀ and the variation Δε ₀ (0.0045) in the harmonic mean particle diameter Dp into the above equation (23) yields A 2.20% increase in Rs ^* could be estimated.

Regarding the sintered ore for charging under the base condition II, since the harmonic average particle diameter Dp is less than 12 mm, by excluding fine grains, the harmonic average particle diameter Dp approaches 12 mm and the initial porosity ε ₀ was expected to rise. Therefore, for the sintered ore for charging under the base condition II (excluding fines shown in Table 1) in which fine grains are excluded, a sintered ore packed bed for charging is formed based on the above formulas (22) and (4). The initial porosity ε ₀ was determined and the harmonic mean particle diameter Dp was determined. As shown in Table 1, removing fine grains with a grain size of 5 mm or less increased the harmonic mean grain size Dp by 0.84 mm and the initial porosity ε ₀ by 0.0043. Substituting the amount of change ΔDp (0.84 mm) in the harmonic mean particle size Dp and the amount of change Δε ₀ (0.0043) in the initial porosity ε ₀ into the above equation (24) yields the reduction rate at the start of fusion bonding Rs ^* could be estimated to increase by 1.65%.

Evaluation 3 (Influence of reduction rate Rs ^* at the start of fusion on reducing agent ratio)
For a 5000 m ³ class large blast furnace, the effect of the reduction rate Rs ^* at the start of fusion on the reducing agent ratio was evaluated. The reducing agent ratio (hereinafter also referred to as “RAR”) refers to the amount of reducing agent [kg/pt] required to produce 1 ton of pig iron.

A charging sintered ore having a particle size distribution similar to the base condition I shown in Table 1 (particle size distribution with a harmonic average particle size Dp exceeding 12 mm) was prepared. An ore layer was formed using this sintered ore for charging, and the target blast furnace was operated for a predetermined period. The ore layer contained sintered ore for charging as well as pellets and lump ore as ore raw materials. After a predetermined period of time, by changing the ratio of charging sintered ore with a particle size exceeding 25 mm (hereinafter also referred to as “sintering + 25 mm ratio”), the particle size of charging sintered ore used in the target blast furnace adjusted the distribution. Instead of charging sintered ore before particle size distribution adjustment, charge sintered ore with particle size distribution adjusted (the same amount as before particle size distribution adjustment) is used to form an ore layer, and the target blast furnace is kept for a predetermined period. operated. This operation was repeated multiple times, and the RAR of the target blast furnace was determined for each predetermined period.

For each charging sinter used in the target blast furnace (sintering + sintered ore with a different ratio of 25 mm), the initial porosity ε ₀ when the charging sinter packed bed is formed is calculated from the above formula (22). At the same time, the harmonic average particle size Dp was obtained from the above formula (4). FIG. 7a shows the relationship between the sintered +25 mm fraction and the initial porosity ε ₀ and the relationship between the sintered +25 mm fraction and the harmonic mean grain size Dp. As shown in Fig. 7a, the lower the sintering +25 mm fraction, the lower the harmonic mean grain size Dp and the higher the initial porosity ε ₀ . From this result, when the harmonic average particle diameter Dp exceeds 12 mm, by decreasing the sintering +25 mm ratio, the harmonic average particle diameter Dp approaches 12 mm and the initial porosity ε ₀ increases. I understand.

FIG. 7b shows the relationship between the RAR of the target blast furnace and the reduction rate Rs ^* at the start of fusion bonding of the ore layer formed from the ore raw material used when calculating the RAR. As shown in FIG. 7b, the RAR tended to decrease as the reduction rate Rs ^* at the start of fusion of the ore layer increased.

Note that the reduction rate Rs* at the start of fusion of the ore layer is obtained by calculating the reduction rate ^{Rs *} at the start of fusion of the packed bed (ore layer made of one type of ore raw material) for each type of ore raw material forming the ore layer. The obtained reduction rate Rs ^* at the start of fusion bonding of the packed bed was obtained by taking a weighted average according to the blending ratio [% by mass] of the ore raw material forming the packed bed in the ore layer. In addition, the reduction rate Rs ^* at the start of fusion of the packed bed (ore layer made of one type of ore raw material) is obtained based on the Rs ^* estimation model described above, and each packed bed Using conditions that are the same as or similar to the filling state of (the ore layer made of one type of ore raw material), and for each of the above conditions (b) to (d), conditions that are the same as or similar to those of the blast furnace in which the ore layer was formed. Using.

From the results of evaluations 1 to 3 described above, the initial porosity ε ₀ of the sintered ore packed bed for charging increases, and the harmonic average particle diameter Dp of the sintered ore for charging reaches the reference value S (12 mm). By adjusting the particle size distribution of the sintered ore to be charged so that it approaches, it is presumed that the reduction rate Rs ^* at the start of fusion bonding for the sintered ore to be charged, whose particle size distribution is to be adjusted, can be increased. Also, it is understood that the RAR can be reduced by increasing the reduction rate Rs ^* at the start of fusion bonding of the ore layer.

Claims (14)

A method for adjusting the particle size distribution of charging sintered ore used for forming an ore layer,
Adjusting the particle size distribution of the charging sintered ore so that the harmonic average particle diameter Dp of the charging sintered ore approaches the reference value S,
Reduction rate at the start of fusion bonding of the investigational sintered ore packed bed when the pressure loss of the investigational sintered ore packed bed made of the investigational sintered ore for determining the reference value S reaches a predetermined value Rs ^* and the harmonic average particle size Dp ^of the sintered ore for study used to ^{obtain the reduction rate Rs* at} the start of fusion bonding. A method for adjusting the particle size distribution of sintered ore, wherein the reference value S is determined as the harmonic average particle size Dp at which is the maximum value. The initial porosity ε ₀ of the sintered ore packed layer for charging made of the sintered ore for charging is higher after adjusting the particle size distribution than before adjusting the sintered ore for charging. The method for adjusting the particle size distribution of sintered ore according to claim 1, wherein the particle size distribution of is adjusted. 3. The method for adjusting the particle size distribution of sintered ore according to claim 2, wherein the maximum value of the reduction rate Rs ^* at the start of fusion bonding is a maximum value. When the harmonic average particle size Dp of the sintered ore for charging before adjusting the particle size distribution exceeds the reference value S, the harmonic average particle size Dp _a of the sintered ore for charging after adjusting the particle size distribution is the above The method for adjusting the particle size distribution of sintered ore according to claim 3, wherein the particle size distribution of the sintered ore for charging is adjusted so as to be equal to or greater than a reference value S. Adjustment of the particle size distribution of the sintered ore according to claim 4, wherein the particle size distribution of the charged sintered ore is adjusted by reducing the proportion of coarse-grained sintered ore exceeding a predetermined particle size. Method. When the harmonic average particle size Dp of the sintered ore for charging before adjusting the particle size distribution is less than the reference value S, the harmonic average particle size _Dpa of the sintered ore for charging after adjusting the particle size distribution is equal to the reference 4. The method for adjusting the particle size distribution of sintered ore according to claim 3, wherein the particle size distribution of the charged sintered ore is adjusted so as to be equal to or less than the value S. Adjustment of the particle size distribution of the sintered ore according to claim 6, wherein the particle size distribution of the charged sintered ore is adjusted by reducing the proportion of fine-grained sintered ore having a particle size less than a predetermined particle size. Method. The particle size distribution of the sintered ore to be charged is adjusted so that the harmonic average particle size _Dpa of the sintered ore to be charged after adjusting the particle size distribution satisfies the following formula (1): The method for adjusting the particle size distribution of the sintered ore according to any one of claims 3 to 7.

In the above formula (1), S indicates a reference value [mm], and _Dpa indicates a harmonic mean particle size [mm] of the sintered ore for charging after adjusting the particle size distribution. The method for adjusting the particle size distribution of sintered ore according to any one of claims 1 to 8, wherein the reference value S is 12 mm. The reduction rate Rs ^* at the start of fusion of the sintered ore packed bed for investigation made of the sintered ore for investigation is determined by (a) the charging (b) the temperature of the sintered ore packed bed for charging; and (c) the composition of the reducing gas flowing in the sintered ore packed bed for charging. and flow rate, and (d) the load applied to the charging sinter packed bed, obtained using one or more of A method for adjusting the particle size distribution of sintered ore. Estimating the amount of change ΔRs ^* of the reduction rate Rs ^* at the start of fusion for the charged sinter whose particle size distribution is adjusted by the adjustment method according to claim 4, based on the following formula (2): A method for estimating the amount of change ΔRs ^* , characterized by:

In the above formula (2), ΔRs ^* indicates the amount of change [%] in the reduction rate Rs ^* at the start of fusion bonding regarding the charging sintered ore before and after adjusting the particle size distribution, and _C1 is the The reduction rate Rs at the start of fusion bonding of the sintered ore for investigation with respect to the harmonic average particle diameter Dp of the sintered ore for investigation in the range where the harmonic average particle diameter Dp of the sintered ore is equal to or greater than the reference value S ^* indicates the rate of change [% / mm], ΔDp indicates the amount of change [mm] in the harmonic average particle diameter Dp of the sintered ore for charging before and after adjusting the particle size distribution, and D ₁ is the study shows the rate of change [%/−] of the reduction rate Rs ^* at the start of fusion bonding of the sintered ore for investigation with respect to the initial porosity ε ₀ of the sintered ore for study, and Δε ₀ is the sintered ore before and after adjustment of the particle size distribution. The amount of change [-] in the initial porosity _ε0 for the required sintered ore is shown. The reference value S is 12,
said C ₁ is -1.2;
wherein said _D1 is 150;
The method for estimating the amount of change ΔRs ^* according to claim 11, characterized in that: Estimating the amount of change ΔRs ^* of the reduction rate Rs ^* at the start of fusion for the charging sinter ore, the particle size distribution of which is adjusted by the adjustment method according to claim 6, based on the following formula (3): A method for estimating the amount of change ΔRs ^* , characterized by:

In the above formula (3), ΔRs ^* indicates the amount of change [%] in the reduction rate Rs ^* at the start of fusion bonding regarding the charging sintered ore before and after adjusting the particle size distribution, and _C2 is the The reduction rate Rs at the start of fusion bonding of the sintered ore for investigation with respect to the harmonic average particle diameter Dp of the sintered ore for investigation in the range where the harmonic average particle diameter Dp of the sintered ore is equal to or less than the reference value S ^* indicates the rate of change [% / mm], ΔDp indicates the amount of change [mm] in the harmonic average particle size Dp of the sintered ore for charging before and after adjusting the particle size distribution, and _D2 is the above-described study. shows the rate of change [%/−] of the reduction rate Rs ^* at the start of fusion bonding of the sintered ore for investigation with respect to the initial porosity ε ₀ of the sintered ore for study, and Δε ₀ is the sintered ore before and after adjustment of the particle size distribution. The amount of change [-] in the initial porosity _ε0 for the required sintered ore is shown. The reference value S is 12,
said _C2 is 1.2;
wherein said _D2 is 150;
The method for estimating the amount of change ΔRs ^* according to claim 13, characterized in that:

Images