Method for operating a blast furnace

Description

/ 20 METHOD FOR OPERATING A BLAST FURNACE TECHNICAL FIELD

[001] The present invention relates to a method for operating a blast furnace in which an iron feedstock containing reduced iron is charged into the blast furnace.

[002] Priority is claimed based on Japanese Patent Application No. 2024-001753, filed on January 10, 2024, the contents of which are incorporated herein by reference. FUNDAMENTALS OF THE TECHNIQUE

[003] In a blast furnace, the raw material iron and coke, which serves as a reducing agent and fuel, are charged alternately through the top of the furnace. In addition, tuyeres are formed at the bottom of the blast furnace, and hot air is blown through them, while auxiliary fuel, such as pulverized coal, is blown into the blast furnace.

[004] Patent Document 1 describes a technique in which reduced iron and the like are loaded into a position where Lc / Dc, which is a ratio of a coke layer thickness Lc to an average coke particle size Dc, is 2 or less (a region in which the coke layer is thin, corresponding to two or fewer coke particles thick).

[005] Patent Document 2 describes a technique in which the distribution of the gas composition in the direction of the furnace diameter in the upper portion of the furnace is measured, and reduced iron and the like are loaded through an auxiliary hopper in a region where nCO (CO2% / (CO% + CO2%)) is 0.57 or more. List of Citations Patent Documents

[006] Patent Document 1: Japanese Patent No. 6358231

[007] Patent Document 2: Japanese Patent No. 6769507 Petition 870260066542, dated 06 / 07 / 2026, page 13 / 41 / 20 Non-Patent Document

[008] Non-Patent Document 1: Takatani et al., ISIJ International, Vol.39(1999), pp.155-22. SUMMARY OF THE INVENTION Technical Problem

[009] The loading positions for reduced iron and similar in Patent Documents 1 and 2 are both regions with a high nCO (regions with a high reduction load).

[0010] However, the method in Patent Document 1 requires identifying a region where the coke layer is thin, and such identification is difficult.

[0011] Furthermore, the method in Patent Document 2 requires the provision of an auxiliary hopper, as a range in the direction of the furnace diameter where reduced iron and similar materials are loaded is small. Additionally, depending on operating conditions, there may be no region where nCO (CO2% / (CO% + CO2%)) is 0.57 or higher, resulting in limited operational flexibility. Furthermore, there is also a problem that the maximum limit on the amount of reduced iron and similar materials that can be loaded is low. Solution to the Problem

[0012] The essence of the present description is as follows.

[0013] (1) A method for operating a blast furnace according to an aspect of the present description is a method for operating a blast furnace in which an iron feedstock containing reduced iron is charged into the blast furnace, the method including: a process for acquiring in advance an nCO distribution in a reference operation in which no reduced iron is contained in the iron feedstock to be charged; a process for identifying a high nCO region of defining, as an average nCO, an average nCO value in the nCO distribution or a Petition 870260066542, dated 06 / 07 / 2026, p. 14 / 41 / 20 nCO calculated from a top gas, and to identify in advance a high nCO region in which a relative nCO, obtained by dividing the nCO in the nCO distribution by the average nCO, is 1.0 or more; and a loading process of 75% or more of the reduced iron in the high nCO region.

[0014] (2) In the method for operating a blast furnace according to (1), preferably, in the process of identifying a high nCO region, a relative nCO distribution, which is a relative nCO distribution obtained by dividing the nCO in the nCO distribution by the average nCO, is acquired, and the high nCO region is identified based on the relative nCO distribution.

[0015] (3) In the method for operating a blast furnace according to (1) or (2), preferably, the blast furnace includes a charging hopper for charging reduced iron, and the charging hopper is a shared charging hopper for charging reduced iron and an iron feedstock other than reduced iron.

[0016] (4) In the method for operating a blast furnace according to any one of (1) to (3), preferably, when the iron feedstock is 100% by mass, a proportion of reduced iron contained in the iron feedstock is 0.5% by mass or more and 50% by mass or less.

[0017] (5) In the method for operating a blast furnace according to any one of (1) to (4), preferably, in the charging process, 80% by mass or more of the reduced iron is charged into the high nCO region.

[0018] (6) In the method for operating a blast furnace according to any one of (1) to (5), preferably, in the process of identifying a high nCO region, a region in which the relative nCO is 1.2 or more is considered as the high nCO region. Advantageous Effects of the Invention

[0019] According to the present invention, the high nCO region can be identified, and the reduced iron can be distributed in a concentrated manner. Petition 870260066542, dated 06 / 07 / 2026, page 15 / 41 / 20 in the high nCO region. As a result, the reducing agent ratio (RAR) can be reduced more effectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] [Figure 1] A distribution of nCO obtained using a blast furnace mathematical model.

[0021] [Figure 2] A relative nCO distribution in which an nCO in the nCO distribution of Figure 1 is replaced by a relative nCO.

[0022] [Figure 3] A bar graph showing a reducing agent ratio (RAR) for each reduced iron loading position.

[0023] [Figure 4] A scatter plot showing a relationship between a reduced iron mixture ratio in a high nCO region and the reducing agent ratio (RAR).

[0024] [Figure 5] A distribution of nCO and a relative nCO distribution acquired in a real furnace. DESCRIPTION OF THE MODALITIES

[0025] A method for operating a blast furnace according to the present invention is a method for operating a blast furnace in which an iron feedstock containing reduced iron is charged into the blast furnace, and includes an acquisition process, a high nCO region identification process, and a charging process. Each process will be described in detail below. Acquisition Process

[0026] The acquisition process is a process of acquiring in advance a distribution of nCO in a reference operation. The reference operation is an operation in which an iron feedstock to be loaded does not contain reduced iron, and is an operation during a period from a point in time when the loading conditions were most recently changed until the point in time when the iron Petition 870260066542, dated 06 / 07 / 2026, page 16 / 41 / 20 reduced iron was loaded. It is important to note that if the loading conditions are altered, the conditions inside the furnace will fluctuate immediately after the alteration, but will eventually stabilize. In the acquisition process, it is preferable to acquire the nCO distribution in advance in a state where the conditions inside the furnace are stable. More preferably, in the acquisition process, the nCO distribution is acquired at a point in time as close as possible to the point in time when the reduced iron is loaded.

[0027] nCO is a ratio between CO and CO2, and is calculated by the following expression. nCO = CO2% / (CO% + CO2%)

[0028] A method for measuring % CO2 and % CO is not particularly limited. For example, % CO2 and % CO can be measured by gas chromatography or similar methods.

[0029] When reduced iron is defined in terms of metallization ratio, the metallization ratio is preferably 70% by mass or more. The metallization ratio is a relative ratio of metallic iron content to total iron content in reduced iron. Metallic iron is iron that is not bonded to oxygen or that does not exist in the form of pyrite.

[0030] Reduced iron may be scrap iron, pig iron blocks, reduced iron pellets, reduced iron briquettes or similar. Pig iron blocks refer to cast iron in fragments of about 10 to 30 kg to facilitate handling of cold pig iron.

[0031] The iron feedstock (excluding reduced iron) is one or more of the following: sintered ore, fragmented ore, pellets and the like, and may contain auxiliary materials (for example, limestone, siliceous stone or serpentine). The reference operation is preferably a stable operation. A stable operation is an operational state in which the gas flow in the furnace, the descent of the charge from a compacted bed of materials Petition 870260066542, dated 06 / 07 / 2026, page 17 / 41 / 20 loaded, a temperature distribution and the like are properly controlled. For example, an operating state in which all of the following conditions are met is considered to be stable operation.

[0032] • The gas flow in the furnace is not biased, and the gas is supplied relatively uniformly to the packed bed, or the fluctuations in the gas flow are small.

[0033] • Fluctuations in the descent of the compacted bed of loaded materials (e.g., stagnation of the descent of the load and slippage) are small.

[0034] • Heat is supplied to the oven without excess or deficiency, that is, temperature fluctuations are small.

[0035] The nCO distribution can be obtained by analyzing the gas composition measured by an upper blast furnace probe. A plurality of probes (e.g., an upper probe, an intermediate probe, and a lower probe) extending into the furnace are installed along a section of the blast furnace shaft, and among these probes, the one located closest to the top of the furnace is the upper probe. The number of measurement points obtained by the upper probe is generally around 7 to 15. The nCO distribution is a graph showing the distribution of nCO along the furnace diameter.

[0036] The nCO distribution can be obtained by providing the operational parameters of the reference operation to a blast furnace mathematical model (see Non-Patent Document 1) and by analyzing the operational parameters. That is, the nCO distribution can be obtained based on the results of measurements from the top probe of a real blast furnace, or it can be obtained based on the blast furnace mathematical model.

[0037] It should be noted that the blast furnace mathematical model described below refers to the blast furnace mathematical model in Non-Patent Document 1, unless otherwise indicated. Petition 870260066542, dated 06 / 07 / 2026, page 18 / 41 / 20

[0038] The blast furnace mathematical model is a mathematical model that divides an internal region of a blast furnace into a plurality of smaller regions and performs calculation processing by substituting predetermined blast furnace operating conditions and feedstock properties into calculation formulas for mass balance, momentum balance, and energy balance for each smaller region, thereby calculating state variables such as the reduction reaction ratio between solids (ores, feedstocks, and the like) and furnace gas (CO gas, H2 gas, and the like), furnace gas flow rate, furnace gas temperature, furnace gas composition, and nCO in each smaller region, and comprehensively simulating the furnace state. High nCO Region Identification Process

[0039] The high nCO region identification process is a process of identifying in advance a high nCO region in which a relative nCO, which is obtained by dividing the nCO in the nCO distribution by the average nCO, is 1.0 or more.

[0040] The average nCO can be an average nCO value in the nCO distribution (hereinafter also referred to as “distribution average nCO”) or it can be an nCO calculated from a top gas (hereinafter also referred to as “top gas nCO”). The distribution average nCO can be the arithmetic mean of nCO at each position of the furnace diameter measured by the top probe, or it can be a median value. Since the top gas is a gas collected at the top of the furnace, the top gas nCO is determined uniquely. The distribution average nCO and the top gas nCO are usually the same value. Therefore, the relative nCO calculated from the distribution average nCO and the relative nCO calculated from the top gas nCO are usually the same value.

[0041] It should be noted that the nCO of the top gas can be obtained by analyzing the top gas of the actual blast furnace, or it can be Petition 870260066542, dated 06 / 07 / 2026, page 19 / 41 / 20 acquired based on the results of the mathematical model analysis of the blast furnace.

[0042] Furthermore, according to the results of investigations carried out by the present inventors, the average nCO value in the nCO distribution is frequently around 50%. Therefore, in the process of identifying a high nCO region, the average nCO in the nCO distribution can be considered as 50%. In this case, it is not necessary to measure and calculate the average distribution nCO and the top gas nCO.

[0043] In the process of identifying a high nCO region, a region in which the relative nCO is 1.1 or more is considered to be the high nCO region. However, the region considered to be the high nCO region may be a region in which the relative nCO is 1.1 or more, a region in which the relative nCO is 1.2 or more, or a region in which the relative nCO is 1.3 or more.

[0044] According to the present inventors' findings, the high nCO region generally exists continuously. However, there may be cases where the high nCO region exists discontinuously. In this case, reduced iron can be loaded into each of the plurality of discontinuously existing high nCO regions. Loading Process

[0045] The loading process is a loading process of loading 75% by mass or more of the reduced iron into the high nCO region. That is, when the reduced iron contained in the iron feedstock layer is considered to be 100% by mass, 75% by mass or more of the reduced iron is loaded into the high nCO region. The amount of reduced iron added is preferably 77% by mass or more, 80% by mass or more, 82% by mass or more, or 85% by mass or more.

[0046] In the present embodiment, as the high nCO region is identified based on the average nCO (in other words, by use, as Petition 870260066542, dated 06 / 07 / 2026, page 20 / 41 / 20 a delimitation, the furnace diameter position where the relative nCO is 1.0), the high nCO region can be defined within a relatively wide range. Therefore, compared to the method in Patent Document 2, where the position where reduced iron is loaded (a furnace diameter region where nCO is 57% or more) is narrow or cannot be identified, excellent versatility is achieved. In many cases, the furnace diameter region where nCO is 57% or more, as described in Patent Document 2, does not exist in the furnace. Therefore, the operating method of Patent Document 2 often cannot be implemented. On the other hand, the furnace diameter position where the relative nCO becomes 1.0 will generally exist in the furnace by definition. The method for operating a blast furnace, according to the present embodiment, can be applied to various distributions of charged materials.

[0047] Furthermore, in an operation shown in Figure 1 described below, it is difficult to identify the region of the furnace diameter in which the nCO is 57% or more and, therefore, it is difficult to identify the position in which the reduced iron is loaded in the method of Patent Document 2.

[0048] By loading 75% or more by mass of the reduced iron contained in the iron feedstock layer into the high nCO region, the reduced iron can be concentrated in a region with a high reducing load, thus reducing the reducing agent ratio (RAR). The “iron feedstock layer” refers to a layer of ore located between layers of coke, and the ore layer can be formed by a single tailings or multiple tailings. It should be noted that reduced iron can be concentrated in a portion of the identified high nCO region, but there is a risk that the gas flow may change due to a local improvement in gas permeability at the loading position, resulting in unstable operation. Therefore, it is desirable to load reduced iron throughout the high nCO region. Furthermore, it is more desirable to load Petition 870260066542, dated 06 / 07 / 2026, page 21 / 41 / 20 uniformly reduces iron throughout the high nCO region.

[0049] A method for loading raw material to achieve this iron raw material layer can be explored using an experimental device that simulates a blast furnace, or using a numerical simulation model, such as the discrete element method (DEM). In such an experimental device, the iron raw material is loaded into the furnace while changing the placement of the reduced iron in a loading hopper to form the iron raw material layer. After the formation of the iron raw material layer, the distribution of the reduced iron within the iron raw material layer is evaluated, whereby a raw material loading method to achieve the layered structure described above can be explored. In the numerical simulation model, the processing performed in the experimental device described above is simulated by means of information processing using software.

[0050] Here, the loading hopper can store reduced iron and a non-reduced iron feedstock. That is, since the high nCO region can be identified over a relatively wide range, reduced iron and non-reduced iron feedstock can be loaded into the furnace from the same loading hopper (in other words, a shared loading hopper). Therefore, unlike Patent Document 2, it is not necessary to provide a dedicated auxiliary hopper for reduced iron.

[0051] When the iron feedstock (containing reduced iron) that forms the iron feedstock layer is considered to be 100% by mass, the proportion of reduced iron is preferably 0.5% by mass or more and 50% by mass or less. The proportion of reduced iron in the iron feedstock can be 0.8% by mass or more, 1.0% by mass or more, or 3% by mass or more. The proportion of reduced iron in the material Petition 870260066542, dated 06 / 07 / 2026, page 22 / 41 / 20 The iron content can be 40% by mass or less, 35% by mass or less, or 30% by mass or less. When the amount of iron reduced is excessively small, the effect of reducing the reducing agent ratio (RAR) cannot be sufficiently displayed. When the amount of iron reduced is excessively large, the amount of oxygen to be reduced decreases and, as a result, the amount of reducing gas required for the furnace operation design decreases, causing disadvantages such as the inability to maintain a top gas temperature.

[0052] The present inventors obtained knowledge about a suitable reduced iron loading position from the results of the analysis of the blast furnace mathematical model. That is, using the blast furnace mathematical model, the influence of the reduced iron loading position in the direction of the furnace diameter on the reducing agent ratio (TAR) was evaluated.

[0053] First, a large blast furnace A, having a furnace volume of approximately 4,500 m3, was defined as a target for the analysis, and the parameters of the blast furnace mathematical model were adjusted so that the operational parameters of a stable operating period, in which no reduced iron was used (in other words, the operational parameters of the reference operation), and the measurement values ​​of the top probe could be reproduced. Figure 1 shows the nCO distribution in the direction of the furnace diameter at the position of the top probe at this moment (corresponding to the nCO distribution acquired in the acquisition process).

[0054] The nCO (50.3%) shown by a dashed line in Figure 1 is an average nCO (top gas nCO) calculated based on the gas composition of the top gas. As described above, the average nCO can be the average of the nCO distribution calculated based on the top probe measurement results. Petition 870260066542, dated 06 / 07 / 2026, page 23 / 41 / 20

[0055] Figure 2 is a relative nCO distribution in which the nCO in the nCO distribution of Figure 1 is replaced by the relative nCO. The relative nCO was obtained by dividing the nCO in the nCO distribution by the average nCO. It can be confirmed that both nCO and relative nCO are low in a central portion of the furnace and in the vicinity of a furnace wall.

[0056] In the central portion of the furnace and in the vicinity of the furnace wall, the O / C ratio (ore to coke), which is the weight ratio of ore to coke, is low in order to ensure gas permeability in the furnace, and the nCO is generally low. The results of the analysis in Figure 1 are consistent with this.

[0057] A region in which the relative nCO was 1.0 or more was defined as the high nCO region, and the influence of the reduced iron loading position was analyzed by the blast furnace mathematical model. In the illustrated example, when the high nCO region is defined in terms of the dimensionless furnace radius ratio, the dimensionless furnace radius ratio of the high nCO region is 0.38 or more and 0.89 or less. Each loading condition is indicated by a Roman numeral (I to XV). The reduced iron was defined to have a metallization rate of 96% by mass and a particle size of 42 mm. 10% by mass of the iron feedstock in the reference operation was replaced by reduced iron (i.e., iron feedstock, except reduced iron:reduced iron = 90% by mass:10% by mass), and the influence of the reduced iron loading position in the furnace diameter direction on the reducing agent ratio (TAR) was evaluated.Tables 1 to 4 show the amount (% by mass) of reduced iron loaded at each furnace diameter position under each of the loading conditions I to XV. The furnace diameter position is shown in terms of the dimensionless ratio of the furnace radius. Petition 870260066542, dated 06 / 07 / 2026, page 24 / 41 / 20 [Table 1] Petition 870260066542, dated 06 / 07 / 2026, page 25 / 41 / 20 [Table 2] Petition 870260066542, dated 06 / 07 / 2026, page 26 / 41 / 20 [Table 3] Petition 870260066542, dated 06 / 07 / 2026, page 27 / 41 / 20 [Table 4] Petition 870260066542, dated 06 / 07 / 2026, page 28 / 41 / 20

[0058] In all loading conditions, the O / C distribution in the direction of the furnace diameter, which was used as a predefined condition, was kept constant. Here, the ore (O) was defined as the sum of the weight of the reduced iron and the weight of the other iron feedstock. In the case of loading condition II, the amount loaded on a central side of the furnace is greater than the amount loaded in the high nCO region, and in the case of loading condition XI, the amount loaded on a side of the furnace wall is greater than the amount loaded in the high nCO region. The blast air volume and oxygen enrichment rate were kept constant, and only the amount of PC injected was adjusted so that the pig iron temperature became constant, and the reducing agent ratio (RAR) was compared.

[0059] Figure 3 shows the influence of reduced iron loading conditions on the reducing agent ratio (RAR). The reducing agent ratio (RAR) deteriorated significantly when the reduced iron was concentrated near the center of the furnace (loading condition II) and when the reduced iron was concentrated near the furnace wall (loading condition XI). This deterioration is attributable to the deterioration of nCO and nH2. From these results, it can be stated that it is not desirable to concentrate reduced iron near the center of the furnace or on the furnace wall with a low O / C ratio. Furthermore, under loading conditions XII, XIII, and XIV, the reducing agent ratio (RAR) deteriorated significantly, as in loading condition II.

[0060] Table 5 and Figure 4 show a mixing ratio of reduced iron in the high nCO region (in the case where the total reduced iron is considered as 100% by mass, the proportion of reduced iron placed in the high nCO region) and the reducing agent ratio (RAR) for each loading condition. Figure 4 is a scatter plot of the data. Petition 870260066542, dated 06 / 07 / 2026, page 29 / 41 / 20 shown in Table 5, with the horizontal geometric axis representing the reduced iron mixing ratio in the high nCO region and the vertical geometric axis representing the reducing agent ratio (RAR). It should be noted that the reduced iron mixing ratio is a ratio of the amount of reduced iron loaded in the high nCO region to the total amount of reduced iron loaded into the furnace, in the case where the iron feedstock containing the reduced iron is loaded into the furnace. A loading condition was determined to be acceptable in cases where the reducing agent ratio was 442.0 kg / t or less. [Table 5] Proportion of reduced iron mixture in the high nCO region (% by mass) Ratio of reducing agents (kg / t) Acceptable / unacceptable Loading condition I 81 440.6 GOOD Loading condition II 16 451.3 BAD Loading condition III 100 439.7 GOOD Loading condition IV 79 440.7 GOOD Loading condition V 82 441.3 GOOD Loading condition VI 90 440.0 GOOD Loading condition VII 100 439.7 GOOD Loading condition VIII 84 440.9 GOOD Loading condition IX 82 440.6 GOOD Loading condition X 80 439.9 GOOD Loading condition XI 73 443.3 BAD Loading condition XII 23 455.9 BAD Loading condition XIII 37 448.7 POOR Loading condition XIV 54 442.9 POOR Loading condition XV 75 441.6 GOOD

[0061] Under loading conditions II, XI, XII, XIII, and XIV, in which the reducing agent ratio (RAR) deteriorated, it can be observed that the proportion of reduced iron mixture in the high nCO region was low. Furthermore, the reducing agent ratio (RAR) tended to decrease as the amount of reduced iron loaded in the high nCO region increased. From the results of these analyses, it was found that the reducing agent ratio (RAR) increased significantly when the proportion of reduced iron mixture in the high nCO region was less than 75% by mass. (Example)

[0062] The present invention will be described in detail with reference to Petition 870260066542, dated 06 / 07 / 2026, p. 30 / 41 / 20 an example.

[0063] In a large blast furnace B, having a furnace volume of 4,000 m3 or more, during a given period (hereinafter also referred to as an operating period) in which operation without the use of reduced iron (i.e., the reference operation) remained stable, the nCO distribution in the direction of the furnace diameter was acquired over several days by means of gas analysis using a top probe. The nCO of the top gas was measured by gas analysis in the upper portion of the furnace, and the relative nCO distribution was then calculated. Figure 5 shows the results.

[0064] Based on the relative nCO distribution, a region (i.e., a region in which the relative nCO is 1.0 or more) with a dimensionless furnace radius ratio of 0.33 to 0.94 was defined as the high nCO region. It should be noted that the period for identifying the high nCO region is optional, but it is more desirable to define the period for a period during which stable operation is performed. Stable operation will not be described again.

[0065] Without altering the loading conditions of the iron and coke feedstock during the operating period, 10% by mass of the iron feedstock was replaced by reduced iron having a metallization ratio of 96%. In the example, the reduced iron was intended to be loaded relatively uniformly in the identified high nCO region. In a comparative example, the reduced iron was intended to be concentrated near the furnace wall.

[0066] Based on the results of preliminary investigations obtained by simulation, the mixing ratio of reduced iron in the high nCO region was 84% ​​by mass in the example and 73% by mass in the comparative example. Table 6 shows a comparison of the main blast furnace operating parameters between the example and the comparative example. Petition 870260066542, dated 06 / 07 / 2026, page 31 / 41 / 20 [Table 6] Example Comparative Example Reduced iron mixture ratio (% by mass) 10.3 10.3 Specific consumption of reduced iron (kg / t) 158 157 Reduced iron mixture ratio in the high nCO region (% by mass) 84 73 Blow air volume (Nm3 / min) 5443 5624 Oxygen enrichment ratio (Nm3 / min) 153 158 Oxygen enrichment ratio (%) 2.1 2.1 Pig iron emission (t / d) 8429 8365 Pig iron temperature (°C) 1536 1531 Top gas temperature (°C) 139 157 Reducing agent ratio (kg / t) 440 452 Coke ratio (kg / t) 324 324 LHV ratio (kg / t) 116 128 Slag ratio (kg / t) 285 281 nCO (-) 48.5 47.6 nH (-) 51.1 50.9 SLC (kg / t) 68.8 66.1 Pressure drop in the furnace (kPa) 66.2 69.7

[0067] It can be observed that there is no significant difference in pig iron emission and pig iron temperature between the example and the comparison example. It was confirmed that the example exhibited higher nCO and nH2 than the comparison example, in addition to a further reduction in the reducing agent ratio (RAR) due to improved reduction efficiency. Petition 870260066542, dated 06 / 07 / 2026, pages 32 / 41

Claims

1 / 2 CLAIMS 1. A method for operating a blast furnace in which an iron feedstock containing reduced iron is charged into the blast furnace, the method characterized in that it comprises: an acquisition process of acquiring in advance an nCO distribution in a direction of the furnace diameter in a reference operation in which no reduced iron is contained in the iron feedstock to be charged; a high nCO region identification process of defining, as an average nCO, an average nCO value in the nCO distribution or an nCO calculated from a top gas, and identifying in advance a high nCO region in which a relative nCO, obtained by dividing the nCO in the nCO distribution by the average nCO, is 1.0 or more; and a charging process of charging 75% or more by mass of the reduced iron into the high nCO region.

2. A method for operating a blast furnace according to claim 1, characterized in that, in the process of identifying a high nCO region, a relative nCO distribution, which is a relative nCO distribution obtained by dividing the nCO in the nCO distribution by the average nCO, is acquired, and the high nCO region is identified based on the relative nCO distribution.

3. Method for operating a blast furnace according to claim 1 or 2, characterized in that the blast furnace includes a charging hopper for loading the reduced iron, and the charging hopper is a shared charging hopper for loading the reduced iron and an iron feedstock other than the reduced iron.

4. Method for operating a blast furnace according to claim 1 or 2, characterized in that, when the iron feedstock is 100% by mass, a proportion of reduced iron contained in the iron feedstock is 0.5% by mass or more and 50% by mass or less.

5. Method for operating a blast furnace according to claim 1 or 2, characterized in that, in the charging process, 80% or more by mass of the reduced iron is charged into the high nCO region.

6. Method for operating a blast furnace according to claim 1 or 2, characterized in that, in the process of identifying a high nCO region, a region in which the relative nCO is 1.2 or more is considered as the high nCO region. Petition 870260066542, dated 06 / 07 / 2026, pp. 41 / 41

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