Blast furnace operation method

Abstract

To provide a blast furnace operation method that can reduce CO2 emission from a blast furnace by suppressing deterioration of a reducing material ratio while using lump ore as a part of ore raw materials charged into a blast furnace.SOLUTION: In a blast furnace operation method, reducing gas having hydrogen is blown into a blast furnace, in which blast furnace raw materials are charged, through a tuyere or a shaft section. In the blast furnace operation method, lump ore and processed ore are used as an iron source in the blast furnace raw materials. On the side of the furnace wall with a dimensionless radius of 0.7-1.0, where the furnace center is 0 and the furnace wall is 1 in the radial direction of the blast furnace, large-size lump ore with a grain size of 20-35 mm is charged at a mass ratio of 6-18% to the whole lump ore.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for operating a blast furnace, and more particularly to a method for operating a blast furnace that can reduce the reducing agent rate of the blast furnace while using lump ore as part of the ore raw material charged into the blast furnace. [Background technology]

[0002] In blast furnace operation, pig iron is produced by charging blast furnace raw materials consisting of coke as a reducing agent and raw ore as an iron source. The raw ore is broadly classified into lump ore, which is obtained by crushing and sieving mined iron ore, and processed ore, which is obtained by agglomerating smaller fine ore into sintered ore, pellets, etc.

[0003] Lump ore and processed ore are selected and used appropriately depending on the blast furnace and its operating conditions, but processed ore such as sintered ore and pellets can be easily stabilized in quality because the blending of raw ore and the addition of auxiliary materials can be adjusted. Therefore, processed ore is used as the main raw ore material.

[0004] In contrast, lump ore has a high iron content, which reduces the generation of slag. However, it generally has lower self-fluxing properties than processed ore and is difficult to reduce. Therefore, when used in a blast furnace, it is crushed to a particle size of around 20 mm and classified to increase its reactivity. However, crushing lump ore in this manner requires an additional process (crushing process), which incurs additional costs.

[0005] On the other hand, given the societal demand for reduced carbon dioxide (CO2) emissions, it is necessary to minimize CO2 emissions from blast furnaces, which account for approximately 70% of CO2 emissions in the steel industry.

[0006] One known method is to inject reducing gas containing hydrogen into the tuyere or shaft. By injecting reducing gas containing hydrogen into the blast furnace in this way, the proportion of carbon used in the blast furnace is reduced (reducing agent ratio) compared to when this method is not implemented. In other words, hydrogen gas acts as a reducing agent instead of carbon and partially covers the iron oxide reduction, reducing the total burden of carbon-based reducing agents and enabling a reduction in CO2 emissions from the blast furnace.

[0007] For example, Patent Document 1 describes a method of operating a blast furnace in which a reducing gas containing 10 mass % or more of hydrogen, such as coke oven gas (COG) or LNG, is blown in from a tuyere, and a combustion gas (non-reducing gas) obtained by burning COG or LNG in advance with oxygen or air is supplied from the shaft as a preheating gas. In this method, the reduction reaction of iron oxide with hydrogen is a relatively large endothermic reaction, which may lower the temperature of the furnace top gas, so preheating gas is blown in from the shaft to compensate for this.

[0008] Furthermore, Patent Document 2 discloses that in blast furnace operation in which reducing gas is injected from the shaft (shaft tuyere) of the blast furnace, small-particle sintered ore is charged near the furnace wall in order to maximize the use of the reducing gas in the furnace. When reducing gas is injected from the shaft, unlike when it is injected from the blast furnace tuyere, there is no equivalent to a raceway, making it difficult for the reducing gas to penetrate to the center of the furnace. Therefore, it is thought that the reducing gas injected from the shaft rises near the furnace wall. Therefore, in this method, the particle size of the sintered ore charged near the furnace wall is reduced, increasing the airflow resistance near the furnace wall, thereby making it easier for the reducing gas to penetrate into the furnace. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-221547 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-199984 Summary of the Invention [Problem to be solved by the invention]

[0010] As mentioned above, there is a need to reduce CO2 emissions from blast furnaces, and one of the measures being considered is to inject reducing gas containing hydrogen into the blast furnace. In addition, while processed ores such as sintered ore and pellets have mainly been used as raw iron sources, if it were possible to increase the use of lump ore, which has lower self-fluxing properties and is less reducible (less reducible) than these processed ores, the effort and cost required to obtain processed ore could be reduced, which would be desirable from the perspective of resource conservation, etc.

[0011] Therefore, the present inventors have conducted extensive research into a method for suppressing a deterioration in the reducing agent ratio even when lump ore is used as part of the ore raw material charged into a blast furnace. As a result, they have unexpectedly found that the reducing agent ratio of a blast furnace can be reduced by charging a predetermined proportion of large-particle-size lump ore having a relatively large particle size onto the furnace wall side and injecting a reducing gas containing hydrogen from the tuyere or shaft, and have completed the present invention.

[0012] Therefore, an object of the present invention is to provide a blast furnace operation method that can suppress deterioration of the reducing agent ratio and reduce CO2 emissions from the blast furnace while using lump ore as part of the ore raw material charged into the blast furnace. [Means for solving the problem]

[0013] That is, the gist of the present invention is as follows. [1] A blast furnace operation method in which reducing gas containing hydrogen is injected from a tuyere or shaft into a blast furnace into which blast furnace raw materials have been charged, A blast furnace operating method characterized by using lump ore and treated ore as the iron source in the blast furnace raw materials, and charging large-particle lump ore having a particle size of 20 to 35 mm on the wall side of the blast furnace at a dimensionless radius of 0.7 to 1.0 in the radial direction of the blast furnace, with the furnace center being 0 and the furnace wall being 1, at a mass ratio of 6 to 18% of the total lump ore. [2] The method for operating a blast furnace according to [1], wherein ordinary lump ore having a particle size of less than 20 mm is mixed with the treated ore and charged. [3] A method for operating a blast furnace according to [1] or [2], in which blast furnace raw materials are charged using a charging sequence including a C dump for charging coke, an O1 dump for charging the large-sized lump ore, and an O2 dump for charging the normal lump ore mixed with the treated ore. [4] The method for operating a blast furnace according to any one of [1] to [3], wherein the lump ore is charged at a mass ratio of 10 to 30% of the total ore raw material consisting of lump ore and treated ore. [5] The reducing gas is coke oven gas (COG), and the injection rate of the coke oven gas is 50 to 150 Nm 3 The blast furnace operating method according to any one of [1] to [4], wherein the blast furnace is a t-pig. [Effects of the Invention]

[0014] According to the present invention, even if lump ore is used as part of the ore raw material, it is possible to suppress a deterioration in the reducing agent ratio of the blast furnace. Moreover, since large-particle lump ore having a relatively large particle size can be charged into the blast furnace, it is possible to eliminate the crushing process and other processes that are required when using lump ore. Furthermore, since lump ore can be used as is instead of processed ore such as sintered ore or pellets, the labor and cost required for converting it into processed ore can be saved. Furthermore, the ore raw material is not limited to a quality suitable for obtaining processed ore, and this method can be said to be desirable from the perspective of securing resources. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is an explanatory diagram that schematically shows an example of the charging distribution of blast furnace raw materials in the blast furnace operating method of the present invention. [Figure 2]FIG. 2 is a graph showing the relationship between the ratio of large-grain lump ore used and the amount of change (ΔC) in the amount of carbon used (Example 1-1). [Figure 3] FIG. 3 is a graph showing the relationship between the ratio of large-grain lump ore used and the amount of change (ΔC) in the amount of carbon used (Example 1-2). [Figure 4] FIG. 4 is a graph showing the relationship between the classification particle size of large lump ore and the change (ΔC) in the amount of carbon used (Example 2). DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described in detail below. In the present invention, in a blast furnace operation method in which a reducing gas containing hydrogen is injected from a tuyere or shaft into a blast furnace charged with blast furnace raw materials, lump ore and treated ore are used as the iron source for the blast furnace raw materials, and lump ore with a particle size of 20 to 35 mm is charged on the furnace wall side of a dimensionless radius of 0.7 to 1.0 in the radial direction of the blast furnace, with the furnace center being 0 and the furnace wall being 1, and the mass ratio of the large-sized lump ore charged on this furnace wall side is 6 to 18% of the total lump ore. In this invention, lump ore with a particle size of 20 to 35 mm is referred to as large-sized lump ore.

[0017] As mentioned above, lump ore has lower self-fluxing properties and is more difficult to reduce than processed ores such as sintered ore and pellets. This is thought to be due to the lump ore's dense nature and low porosity. On the other hand, hydrogen gas (H2 gas) contained in the reducing gas injected into the blast furnace is thought to be more suitable for reducing lump ore than CO gas, which is mainly generated in the blast furnace. This is because hydrogen is thought to penetrate deep into even dense lump ore with low porosity. However, to actually control the reducing agent ratio, there are optimal values ​​for the lump ore size (particle size) and its charging amount (proportion of the total lump ore).

[0018] Specifically, large lump ore with a particle size of 20 to 35 mm is charged to the wall side of the blast furnace, which is a dimensionless radius of 0.7 to 1.0, where the center of the furnace is 0 and the wall is 1. By controlling the particle size of the lump ore charged to the wall side of the blast furnace within this range, sufficient reduction can be achieved by the hydrogen contained in the reducing gas blown into the tuyere or shaft. Lump ore with a particle size exceeding 35 mm cannot be reduced by the reducing gas blown into the blast furnace, resulting in an increased reducing agent ratio (increased carbon consumption). Furthermore, particle sizes less than 20 mm are not significantly different from the particle size of lump ore currently commonly crushed and classified, which does not lead to a reduction in the crushing process. Furthermore, the effect of reducing the reducing agent ratio by distributing large lump ore closer to the wall side cannot be achieved.

[0019] In addition, the large lump ore with a particle size of 20 to 35 mm charged to the furnace wall side is set to a mass ratio of 6 to 18% of the total lump ore. By setting the amount of large lump ore unevenly distributed on the furnace wall side to this range relative to the total lump ore, the reducing agent rate of the blast furnace can be reduced (reduced carbon consumption) compared to the case of average charging, in which the same amount of lump ore is uniformly charged in the radial direction of the blast furnace. If this ratio is less than 6%, the effect of reducing the reducing agent rate by unevenly distributing the large lump ore on the furnace wall side is not fully achieved. Conversely, if it exceeds 18%, the reducing agent rate increases compared to the case of average charging as described above.

[0020] In the present invention, the reason why large lump ore having a predetermined particle size is charged on the furnace wall side with a dimensionless radius of 0.7 to 1.0 as described above is to reduce it with reducing gas blown in from the tuyere or shaft (for H reduction). Generally, the temperature at the tuyere of a blast furnace is about 2000°C, and at the shaft it is about 1000°C. On the other hand, hydrogen reduction is activated in the region of the blast furnace above 1000°C. Therefore, by blowing reducing gas containing hydrogen gas into the tuyere or shaft, the large lump ore is reduced as the reducing gas rises near the furnace wall.

[0021] Furthermore, in the present invention, lump ore having a particle size of less than 20 mm is preferably mixed with processed ore such as sintered ore or pellets, which is an ore raw material other than large-sized lump ore, and then charged. In the present invention, lump ore having a particle size of less than 20 mm is referred to as normal lump ore. Such normal lump ore is considered to have higher reactivity than large-sized lump ore because it has been crushed. Therefore, it can be mixed with processed ore such as sintered ore or pellets and then charged. In this case, the ore raw material mixture of the processed ore and the normal lump ore may be charged at any position in the radial direction of the blast furnace, or may be unevenly distributed in either direction in the radial direction, but it is preferably charged uniformly in the radial direction of the blast furnace.

[0022] FIG. 1 shows a schematic diagram of the distribution of blast furnace raw materials within a blast furnace as an example of a blast furnace operating method according to the present invention. In this example, the blast furnace raw materials are charged using a charging sequence including a C dump for charging coke, an O1 dump for charging large lump ore, and an O2 dump for charging normal lump ore mixed with treated ore. As described above, in the present invention, the large lump ore only needs to be charged on the furnace wall side, and there are no other limitations. The mixture of normal lump ore and treated ore and coke can be uniformly charged in the radial direction, as shown in FIG. 1. In addition to lump ore, treated ore used as an iron source for blast furnace raw materials in the present invention refers to fine ore or fine ore that has been subjected to agglomeration processes such as sintering or pelleting. Examples of such treated ores include unfired carbon-bearing agglomerated ores, which are formed by agglomerating fine ore with a carbonaceous material and a hydraulic binder such as cement.

[0023] In the present invention, the amount of lump ore used as the iron source for the blast furnace feedstock is not particularly limited and can be the same as in general blast furnace operation. However, it is preferable that the lump ore be 10 to 30% by mass of the total ore feedstock consisting of lump ore and processed ore. The amount of lump ore charged here is the sum of normal lump ore and large lump ore. In this way, even if the ratio of lump ore to the total ore feedstock changes, it is sufficient to distribute the large lump ore toward the furnace wall so that the mass ratio of the total lump ore is 6 to 18%. This means that normal lump ore can be sufficiently reduced by other reducing gases, such as CO gas, generated in the blast furnace by charging it in the same way as processed ore.

[0024] In the present invention, the reducing gas to be injected into the blast furnace is not particularly limited as long as it contains hydrogen, and examples thereof include pure hydrogen gas, coke oven gas (COG), natural gas (LNG), blast furnace gas (BFG), etc. These may be modified by increasing the hydrogen content. The amount of reducing gas to be injected into the blast furnace varies depending on the type of reducing gas, but for example, in the case of coke oven gas (COG), the amount to be injected into the blast furnace is 50 to 150 Nm 3 / t-pig is preferable. Excessive use of reducing gas containing hydrogen leads to a lower temperature in the blast furnace, which in turn reduces the reduction efficiency. On the other hand, if the amount is too small, the effect is not observed. In other words, when COG is injected, 150 Nm 3 It is believed that the more it is used up to / t-pig, the more effective it is in reducing carbon usage, but it is desirable to adjust the injection amount within this range while taking into consideration the supply balance.

[0025] Furthermore, this reducing gas does not need to be preheated before being injected from the tuyere or shaft, and can be injected at room temperature. Injecting the gas at room temperature eliminates the effect of heat loss due to gas heating. In other words, the main purpose of blast furnace operation using reducing gas is to reduce carbon dioxide emissions, but when considering the heat balance including pre-treatment, the heat loss due to pre-heating of the reducing gas works against the reduction of carbon dioxide emissions.

[0026] In the present invention, it is sufficient to charge large-grain lump ore having a relatively large particle size into the furnace wall side at a predetermined rate, and to blow in a reducing gas containing hydrogen from the tuyere or shaft, and other than the above, the operation can be the same as that of a known blast furnace. [Example]

[0027] The present invention will be specifically described below with reference to examples, although the present invention is not limited to these examples.

[0028] Example 1 Based on simulations using a blast furnace mathematical model, the following blast furnace operation was considered. The target blast furnace has a furnace volume of 4500m 3 The raw materials for the blast furnace were sintered ore and lump ore having the compositions shown in Table 1 as the iron source, and coke as the reducing agent. 3 In addition to this COG, air heated to 1200°C was blown in from the same tuyeres at a rate of 4870 Nm 3 / t-pig, room temperature oxygen 58800Nm 3 The reduction efficiency of the sintered ore and lump ore was 66.3% and 51.2%, respectively, according to JIS-RI. In addition to the above, in this example, the base conditions were a coke rate of 293.3 kg / t, a pulverized coal rate of 140.5 kg / t, a pig iron production rate of 12,000 t / day, and a hot metal temperature of 1,530°C. Since the reduction efficiency in the furnace changes depending on the amount of large-sized lump ore charged, the amount of pulverized coal used was adjusted to maintain a constant hot metal temperature. The mathematical model used was a modified version of the two-dimensional steady-state model proposed by Hatano et al. (Reference: Hatano Michiharu, Kurita Koichi, Iron and Steel, Vol. 66 (1980), pp. 1898-1907) that takes into account the radial distribution of the raw ore.

[0029] [Table 1]

[0030] In Example 1, the optimum range of the ratio of large-sized lump ore to the total lump ore was investigated among the ore raw materials used as the iron source. In this model calculation, the representative particle size of the large-sized lump ore was set to 27.5 mm, and the large-sized lump ore was placed on the furnace wall side with a dimensionless radius of 0.7 to 1.0, with the furnace center being 0 and the furnace wall being 1 in the radial direction of the blast furnace. In addition, ore with a particle size of less than 20 mm was considered to be normal sintered ore.

[0031] Specifically, in Example 1-1, the total lump ore (regular lump ore and large lump ore) was charged at 30% by mass of the total ore raw material consisting of lump ore and sinter, with the remaining 70% by mass being sinter. The ratio (balance) of the large lump ore to the regular lump ore in the total lump ore was varied in 3% by mass increments. The large lump ore was charged to the furnace wall side using the O1 dump shown in Figure 1, while the regular lump ore was mixed with the sinter using the O2 dump, also shown in Figure 1, and uniformly charged in the radial direction of the blast furnace. The change in carbon usage (ΔC) was then measured. For example, when the ratio of large lump ore was 3% by mass, the remaining 97% by mass was regular lump ore. The former was charged using the O1 dump, and the latter using the O2 dump. When the ratio of large lump ore used was 6 mass%, the remaining 94 mass% was normal lump ore, and the large lump ore was charged as O1 dump and the normal lump ore was charged as O2 dump so that the ratio was in the range of 0 to 27 mass% and 100 to 73 mass%, respectively.

[0032] Since this example was intended to investigate the effect of unevenly distributing large lump ore on the wall side of a blast furnace on promoting reduction, the change in carbon usage (ΔC) was also investigated when the large lump ore was not charged to the wall side of the blast furnace, but was instead mixed with the sintered ore and normal lump ore for even charging. In other words, when the large lump ore was unevenly distributed, three dumps were charged: C dump, O1 dump, and O2 dump. However, when the lump ore was evenly charged, C dump and O dump were repeated. However, during this even charging, the proportion of large lump ore in the lump ore was varied in 3% mass increments, just as in the case of unevenly distributing the large lump ore. The results are shown in Figure 2.

[0033] The amount of large lump ore charged in actual operation is determined primarily based on the ratio of oversized to undersized particles when sieved through a 20 mm sieve, which is based on the particle size distribution inherent to the lump ore. Since this example was conducted to investigate the optimum amount of large lump ore to be charged, the amount of large lump ore charged was intentionally varied without considering the inherent coarse / fine ratio of the lump ore. This was done to confirm the effect of uneven charging of the large lump ore on the furnace wall side, since the particle size distribution of lump ore varies depending on, for example, the type and time of arrival of the lump ore, and the proportion of large lump ore also varies.

[0034] In Figure 2, the vertical axis shows the change in carbon consumption, ΔC, relative to a 0% large lump ore ratio (all lump ores 20 mm or less). Figure 2 shows that for both uneven charging (peripheral charging of large lump ores), in which large lump ores are unevenly distributed toward the wall of the blast furnace, and average charging (evenly charged with regular lump ores mixed with sintered ore), the reduction efficiency of the blast furnace decreases and the carbon consumption increases as the amount of large lump ore used increases. However, specifically, until the large lump ore ratio reaches 6% by mass, the effect of large lump ore on the reduction efficiency (carbon consumption) is small in both peripheral charging and average charging. However, from 6% to 18% by mass, the increase in carbon consumption is smaller with peripheral charging of large lump ore than with average charging. This is thought to be because the reduction of large lump ore particles, which have poor reducibility, progressed due to hydrogen reduction (H2 reduction) at the peripheral area of ​​the furnace wall caused by COG injected from the tuyere.

[0035] On the other hand, when the ratio of large lump ore used exceeded 18 mass%, the carbon consumption for peripheral charging of large lump ore worsened compared to average charging. This is thought to be because the reduction in the peripheral areas on the furnace wall side could no longer be fully covered by hydrogen reduction using COG, leaving unreduced iron oxide all the way to the lower part of the blast furnace, which had a negative impact on the thermal indicators of the blast furnace, such as the molten iron temperature, forcing an increase in carbon consumption.

[0036] In Example 1-2, the total lump ore (normal lump ore and large lump ore) was charged to a total ore raw material consisting of lump ore and sinter, with 20% by mass of the total lump ore, and the remaining 80% by mass was sinter, and the effect of promoting reduction by distributing the large lump ore closer to the wall of the blast furnace was investigated. However, in this Example 1-2, the ratio (balance) of the large lump ore to the normal lump ore in the total lump ore was changed in 2% by mass increments, so that the large lump ore was in the range of 0 to 20% by mass and the normal lump ore was in the range of 100 to 80% by mass. The results, as shown in Figure 3, show that, as in Example 1-1, when the mass ratio of the large lump ore to the total lump ore was in the range of 6 to 18%, charging the large lump ore near the wall of the blast furnace resulted in an advantage in terms of carbon consumption.

[0037] These results confirmed that, when the ratio of large lump ore used was between 6% and 18% by mass, charging the large lump ore on the furnace wall side could reduce the increase in carbon usage (suppressing a deterioration in the reducing agent rate). The fact that similar results were obtained even when the lump ore ratio in the total ore raw material consisting of lump ore and sintered ore varied suggests that, at least up to a lump ore ratio of 30% by mass, small lump ore can be sufficiently reduced by uniformly charging it mixed with the sintered ore, without being charged near the furnace wall.

[0038] Example 2 In the same manner as in the simulation of Example 1, Example 2 investigated the particle size of large lump ore. In Example 2, the total amount of lump ore (large lump ore and normal lump ore) charged was 20% by mass of the total ore raw material consisting of lump ore and sinter, with the large lump ore and normal lump ore each accounting for 10% by mass. The remaining 80% by mass of the total ore raw material was sinter. As in Example 1, after the C dump shown in Figure 1, the large lump ore was charged into the furnace wall side with an O1 dump at a dimensionless radius of 0.7 to 1.0, and the normal lump ore was mixed with the sinter and uniformly charged in the radial direction of the blast furnace with the O2 dump. The change in carbon usage (ΔC) was investigated with and without COG injection from the tuyere.

[0039] Six types of lump ore (Cases 1 to 6) with different particle size compositions were prepared, as shown in Table 2 below. The lump ore in Case 1 was classified so that particles with particle sizes of 5 to 10 mm and 10 to 15 mm accounted for 50.0 mass% and particles with particle sizes of 15 to 20 mm or larger (15 to 20 mm, 20 to 25 mm, 25 to 30 mm, 30 to 35 mm, 35 to 40 mm, 40 to 45 mm, and 45 to 50 mm) accounted for 50.0 mass% (average particle size: 20.1 mm). For Case 1, the threshold for large lump ore was 15 mm. Those with particle sizes of 15 to 20 mm or larger were charged on the furnace wall side (O1 dump), while those with particle sizes of 5 to 10 mm and 10 to 15 mm were mixed with sintered ore and uniformly charged in the radial direction of the blast furnace (O2 dump). Similarly, for Cases 2 to 6, the particle size composition of the lump ores was set to a cumulative 50.0 mass% as the standard, and the threshold for large-sized lump ores was set to a range of 15 mm to 40 mm. For each lump ore, those with a particle size equal to or larger than the threshold (shown in bold and underlined in the table) were charged on the furnace wall side as large-sized lump ores, and the remainder was mixed with sintered ore and charged uniformly as normal lump ores.

[0040] [Table 2]

[0041] The change in carbon usage (ΔC) in the above case is shown in Figure 4. Regarding these results, when there was no COG injection, the carbon usage increased as the particle size of the large lump ore increased. This is thought to be because the CO gas generated inside the blast furnace could not keep up with the reduction of the large lump ore charged around the furnace wall. However, there was no difference due to the influence of COG injection up to a lump ore particle size threshold of 20 mm. This is presumably because lump ore with a particle size that is not too large can be sufficiently reduced by the CO gas generated inside the blast furnace.

[0042] On the other hand, when the particle size of the large lump ore was 20 mm or larger, the carbon consumption increased without COG injection, whereas with COG injection, the effect on the carbon consumption was minimal, at least up to a lump ore particle size of 35 mm. This means that large lump ore with particle sizes of 20 to 35 mm can be rapidly reduced by the hydrogen contained in the COG, preventing the delay in reduction caused by larger lump ore particle sizes. However, when the particle size exceeded 35 mm, hydrogen reduction by COG injection was no longer sufficient, and the carbon consumption increased rapidly. For this reason, it is desirable that the particle size of the large lump ore charged on the wall side of the blast furnace be in the range of 20 to 35 mm.

[0043] As described above, according to the present invention, even if lump ore is used as part of the ore raw material, it is possible to suppress a deterioration in the reducing agent ratio of the blast furnace. Moreover, since large-particle-sized lump ore having a relatively large particle size can be charged into the blast furnace, it is possible to eliminate the crushing process and the like that are required when using lump ore. Furthermore, since the lump ore can be used as is, it is possible to save the labor and cost required to obtain processed ore such as sintered ore or pellets.

Claims

1. A blast furnace operation method in which reducing gas containing hydrogen is injected from a tuyere or shaft into a blast furnace into which blast furnace raw materials have been charged, lump ore and treated ore are used as iron sources in the blast furnace raw material, and the lump ore is charged at a mass ratio of 10 to 30% of the total ore raw material consisting of the lump ore and the treated ore, A method for operating a blast furnace, characterized in that large-particle lump ore having a particle size of 20 to 35 mm is charged on the furnace wall side of a dimensionless radius of 0.7 to 1.0 in the radial direction of the blast furnace, with the furnace center being 0 and the furnace wall being 1, at a mass ratio of 6 to 18% of the total lump ore.

2. 2. The method for operating a blast furnace according to claim 1, wherein ordinary lump ore having a particle size of less than 20 mm is mixed with the treated ore and charged.

3. 3. The method for operating a blast furnace according to claim 2, wherein the blast furnace raw materials are charged using a charging sequence including a C dump for charging coke, an O1 dump for charging the large-sized lump ore, and an O2 dump for charging the normal lump ore mixed with the treated ore.

4. The reducing gas is coke oven gas (COG), and the injection rate of the coke oven gas is 50 to 150 Nm ３ The blast furnace operating method according to any one of claims 1 to 3, wherein the blast furnace is a blast furnace.

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