Blast furnace, method for operating blast furnace, and tuyere

Abstract

Provided is a method for operating a blast furnace that has a tuyere, wherein: the tuyere has a tuyere body, a gaseous reducing material-blowing lance, and a solid reducing material-blowing lance; the tuyere body has a hot-air flow path; one lance among the gaseous reducing material-blowing lance and the solid reducing material-blowing lance has an outlet in the hot-air flow path; and the other lance among the gaseous reducing material-blowing lance and the solid reducing material-blowing lance has an outlet in said one lance.

Description

Blast furnace, blast furnace operating method, and tuyeres

[0001] This disclosure relates to a blast furnace, a method of operating a blast furnace, and a tuyeres. This application claims priority under Japanese Patent Application No. 2025-052920, filed in Japan on 27 March 2025, the contents of which are incorporated herein by reference.

[0002] In the iron and steel industry, the blast furnace method is the dominant process for producing pig iron. In the blast furnace method, blast furnace iron-based raw materials (raw materials containing iron oxide, mainly sintered ore; hereinafter simply referred to as "iron-based raw materials") and coke are alternately and layered into the blast furnace from the top, while hot air is blown into the blast furnace from tuyeres at the bottom. The hot air reacts with, for example, pulverized coal blown in with the hot air and the coke in the blast furnace to generate high-temperature reducing gas (mainly CO gas in this case). In other words, the hot air gasifies the coke and pulverized coal. The reducing gas rises inside the blast furnace, heating and reducing the iron-based raw materials. The iron-based raw materials descend inside the blast furnace, being heated and reduced by the reducing gas. Subsequently, the iron-based raw materials melt and drip down the blast furnace while being further reduced by the coke. The iron-based raw materials are ultimately stored in the hearth as molten pig iron. The molten iron from the hearth is removed through the taphole and used in the next steelmaking process. Therefore, in the blast furnace method, carbon materials such as coke and pulverized coal are used as reducing agents.

[0003] By the way, in recent years, there has been much talk about preventing global warming, and carbon dioxide (CO2), one of the greenhouse gases, is being addressed. ２ Reducing CO2 emissions has become a social issue. As mentioned above, the blast furnace method uses carbon as a reducing agent, so a large amount of CO2 is emitted. ２ It generates gas. Therefore, the steel industry is CO2 ２ As one of the major industries in terms of gas emissions, we must respond to this societal demand. Specifically, there is an urgent need to further reduce the reducing agent ratio (amount of reducing agent used per ton of molten iron) in blast furnace operations.

[0004] Reducing agents play two roles in the furnace: generating heat to raise the temperature of the charge and reducing the iron-based raw materials. To reduce the reducing agent ratio, it is necessary to increase the reduction efficiency in the furnace. The reduction reaction in the furnace can be expressed by various reaction equations. Of these reduction reactions, the direct reduction reaction with coke (reaction equation: FeO + C ⇒ Fe + CO) is an endothermic reaction that involves a large amount of heat absorption. Therefore, minimizing the occurrence of this reaction is important in reducing the reducing agent ratio. Since this direct reduction reaction occurs in the lower part of the blast furnace, the iron-based raw materials must absorb CO and H before reaching the lower part of the furnace. ２ If iron-based raw materials can be sufficiently reduced with reducing gases such as those mentioned above, the amount of iron-based raw materials that are directly subject to reduction can be reduced.

[0005] When a large amount of hydrogen-based reducing gas is injected into the blast furnace from the tuyeres, the upper and lower parts of the furnace (the lower part here refers to the Sol Roth reaction (C + CO)) ２ →2CO) This is the region where the furnace temperature is higher than the starting temperature. The upper part of the furnace is the region above the lower part of the furnace. The thermal balance of the upper and lower parts changes significantly. Therefore, it is necessary to appropriately control the operating parameters so that the thermal balance of the upper and lower parts of the furnace is maintained. In other words, if a large amount of hydrogen-based reducing gas is blown into the blast furnace from the tuyere in order to enjoy a significant carbon reduction effect, the tuyere combustion temperature will decrease. If the oxygen enrichment rate is increased to suppress this decrease in tuyere combustion temperature, the heat flow ratio will increase. As a result, the furnace top gas temperature will decrease, falling below the lower limit of the furnace top gas temperature as an operational management standard, and there is a concern that this may lead to a significant delay in the heating of the charges in the upper part of the furnace and a deterioration of ventilation due to insufficient discharge of dust to the outside of the furnace.

[0006] Furthermore, if the reducing agent is replaced with a hydrogen-based reducing gas, resulting in a decrease in the reducing agent ratio, and operations are conducted in a way that reduces the amount of expensive coke charged, the thickness of the ore layer will increase compared to the thickness of the coke layer in the blast furnace. This raises concerns that the reduction gas concentration within the ore layer may decrease, leading to a significant decrease in furnace reaction efficiency and an increase in airflow resistance.

[0007] Herein, Patent Document 1 describes a blast furnace operation method in which at least a solid reducing agent is blown into the furnace from a tuyer using a lance, characterized in that when blowing only a solid reducing agent, two types of solid reducing agents and a combustion-supporting gas simultaneously, or three types of solid reducing agents, combustion-supporting gas and a gaseous reducing agent simultaneously, a tube bundle type lance is used, in which multiple blowing pipes are arranged in parallel and bundled together and housed in the main lance tube, and the solid reducing agent, combustion-supporting gas and a gaseous reducing agent are blown in through any of the aforementioned blowing pipes.

[0008] Furthermore, Patent Document 2 describes a double-tube lance for blowing pulverized coal, which is installed through a blower pipe connected to a tuyere, and comprises an inner tube for blowing pulverized coal into the tuyere, and a straight outer tube for blowing gas flowing between the inner tube into the tuyere, wherein the inner tube has a tip opening located at the tip of the outer tube, close to or in contact with the inner surface of the outer tube, a straight section coaxial with the central axis of the outer tube, and a curved section formed between the tip opening and the straight section, which curves from the straight section with a predetermined bending radius, and is characterized in that pulverized coal is blown in a direction different from the gas blowing direction of the outer tube.

[0009] International Publication No. 2014 / 010660, Japanese Patent Publication No. 2023-128469

[0010] The technologies disclosed in Patent Documents 1 and 2 involve providing a lance inside the tuyeres. However, it has been found that pulverized coal is difficult to disperse, and the gasification and combustion reactivity of pulverized coal is reduced. Therefore, there was room to reduce the reducing agent ratio in the operation of the blast furnace. This disclosure has been made in view of the above circumstances, and the object of this disclosure is to provide a tuyeres capable of reducing the reducing agent ratio, a blast furnace having the same, and a method for operating the blast furnace.

[0011] To solve the above problems, the present disclosure adopts the following configuration: (1) A blast furnace having a tuyere, wherein the tuyere comprises a tuyere body, a gaseous reducing agent injection lance, and a solid reducing agent injection lance, the tuyere body having a hot air passage, and either the gaseous reducing agent injection lance or the solid reducing agent injection lance having an outlet in the hot air passage, and the other lance having an outlet inside the first lance. (2) The blast furnace according to (1), wherein the gaseous reducing agent injection lance has an outlet in the hot air passage, and the solid reducing agent injection lance has an outlet inside the gaseous reducing agent injection lance. (3) The blast furnace according to (1), further comprising a heating device for heating the gaseous reducing agent. (4) A method for operating a blast furnace as described in any one of (1) to (3), wherein hot air is flowed through the hot air passage of the tuyere body, a gaseous reducing agent or a solid reducing agent is blown out from the outlet of the other lance inside the one lance, and the gaseous reducing agent and the solid reducing agent are blown out from the outlet of the one lance. (5) A tuyere used in a blast furnace, wherein the tuyere comprises a tuyere body, a gaseous reducing agent blowing lance, and a solid reducing agent blowing lance, the tuyere body having a hot air passage, and one of the lances, the gaseous reducing agent blowing lance and the solid reducing agent blowing lance, has an outlet in the hot air passage, and the other lance has an outlet inside the one lance. (6) The tuyeres according to (5), wherein the gas reducing agent blowing lance has an outlet in the hot air passage, and the solid reducing agent blowing lance has an outlet inside the gas reducing agent blowing lance.

[0012] According to this disclosure, it is possible to provide a tuyeres that enable operation to further reduce the reducing agent ratio, a blast furnace having the same, and a method for operating the blast furnace.

[0013] This is a schematic diagram of the blast furnace used in this embodiment. This is a cross-sectional view of a tuyeres attached to the blast furnace used in this embodiment. This is a cross-sectional view of a tuyeres attached to a blast furnace equipped with a conventional reducing agent injection lance. This is a diagram showing the results of the study on the lance confluence position. This is a diagram showing the evaluation results in the embodiment.

[0014] In conventional blast furnace operation methods, simply increasing the oxygen enrichment rate makes it difficult to simultaneously maintain the tuyere combustion temperature and the top gas temperature within the appropriate range. This is because the blast furnace process utilizes the exhaust gas (exhaust gas after the Sol-Roth reaction is completed in the lower furnace) after the heat balance in the lower furnace, where the reduction and thermal load are greatest, is established to establish the reduction and thermal balance in the upper furnace. In normal operation without the use of hydrogen-based reducing gas, the operation is carried out with appropriate parameters so that the heat balance in the upper and lower furnaces is simultaneously satisfied. On the other hand, in operation in which a large amount of hydrogen-based reducing gas is injected into the blast furnace, the ore reduction rate becomes almost 100% at the fusion zone level and the amount of molten reduction becomes almost zero, so the reduction and thermal load in the lower furnace is greatly reduced. Consequently, carbon consumption is reduced. However, when a large amount of hydrogen and pulverized coal are injected simultaneously, there is a concern that the gasification and combustion rate of pulverized coal will decrease because the reducing gas, which has a higher combustion rate, burns preferentially over the pulverized coal.

[0015] The inventors of the present invention have conducted detailed studies on a technique for injecting hydrogen gas and pulverized coal into a blast furnace from a lance attached around the tuyer. By reviewing the installation position of the lance, they succeeded in finding a blast furnace capable of injecting pulverized coal in a way that ensures sufficient dispersion. The following describes a blast furnace and a method of operating the blast furnace that are embodiments of this disclosure. In this disclosure, "good dispersibility" of pulverized coal in the blast furnace means that the pulverized coal is spread out within the raceway. For example, it means that the distribution of pulverized coal is wide when the distribution of pulverized coal in any cross-section of the raceway is observed.

[0016] The blast furnace of this embodiment is a blast furnace having a tuyere, the tuyere having a tuyere body, a gaseous reducing agent injection lance, and a solid reducing agent injection lance, the tuyere body having a hot air passage, and one of the lances, the gaseous reducing agent injection lance and the solid reducing agent injection lance, having an outlet in the hot air passage, and the other lance having an outlet inside the other lance.

[0017] Figure 1 shows a schematic diagram of the blast furnace 1 according to this embodiment. The blast furnace 1 in this embodiment is equipment for reducing iron ore and extracting molten pig iron. As shown in Figure 1, the core axis A, which is the central axis of the blast furnace 1, extends upward. The blast furnace 1 has a bottomed cylindrical shape centered on the core axis A. Although not specifically shown, iron-based raw materials and coke are charged into the blast furnace 1 alternately and in layers from the top 1a.

[0018] [Definition of Blast Furnace Direction] In this embodiment, the direction in which the core axis A extends (vertical direction), that is, the direction along the core axis A, is called the up-down direction. Of the up-down directions, the direction from the top 1a of the blast furnace 1 toward the bottom 1b is called the down-down direction, and the direction from the bottom 1b toward the top 1a is called the up-up direction.

[0019] Furthermore, the direction perpendicular to the core axis A is called the radial direction. Within the radial direction, the direction approaching the core axis A is called the inward radial direction, and the direction moving away from the core axis A is called the outward radial direction. Note that the direction moving inward in the radial direction is sometimes simply called the core direction. Also, the direction that circles around the core axis A is called the circumferential direction.

[0020] [Components of the blast furnace] The blast furnace 1 comprises a shaft section 2, a belly section 3, a Bosch section 4, and a hearth section 5. The shaft section 2, belly section 3, Bosch section 4, and hearth section 5 are arranged in this order from the top 1a of the furnace to the bottom 1b of the furnace.

[0021] The shaft section 2 has a tapered cylindrical shape that expands in diameter downwards. The shaft section 2 has a flared shape, with its diameter increasing towards the bottom. The belly section 3 has a cylindrical shape that extends along the core axis A. The belly section 3 has a straight body shape, with its diameter remaining constant at each position in the vertical direction.

[0022] The bosch section 4 is formed into a tapered cylindrical shape whose diameter decreases in the downward direction. The bosch section 4 has a tapered bottom shape, and its diameter dimension decreases in the downward direction. The hearth section 5 is disposed at the lower end of the blast furnace 1. The hearth section 5 has a substantially cylindrical shape. In the illustrated example, the inner diameter dimension of the hearth section 5 decreases stepwise in the downward direction. The hearth section 5 is provided with a tap hole not shown in the figure. Pig iron produced in the blast furnace 1 is taken out of the furnace through the tap hole.

[0023] As shown in Fig. 1, the blast furnace 1 is provided with tuyeres 6 disposed on the furnace wall of the hearth section 5. The blast furnace 1 is also provided with a blower 10 connected to the tuyeres 6 and a hydrogen-based reducing gas supply system 25. The hydrogen-based reducing gas supply system 25 comprises a hydrogen-based reducing gas tank 30 and a heating device 31. A plurality of tuyeres 6 are provided on the furnace wall of the hearth section 5 spaced apart from each other in the circumferential direction of the furnace. In this embodiment, hot air, an auxiliary reducing agent and enriched oxygen gas supplied from the blower 10, and hydrogen-based reducing gas supplied from the hydrogen-based reducing gas supply system 25 are blown into the furnace of the blast furnace 1 through the tuyeres 6. The hot air blown from the tuyeres 6 reacts with the auxiliary reducing agent blown from the tuyeres 6 and coke in the furnace to generate high-temperature reducing gas (mainly CO gas herein). That is, the hot air gasifies the coke and the auxiliary reducing agent. Examples of the auxiliary reducing agent include pulverized coal, waste plastic, heavy oil, propane gas and the like. Note that the auxiliary reducing agent may not be blown into the furnace in some cases. Although not particularly illustrated, a cavity (combustion space) called a raceway (RW) is formed in front of the tuyeres 6 by the hot air etc. blown from the tuyeres 6.

[0024] Hydrogen-based reducing gas refers to gas containing H at an elemental composition ratio of 30 mol% or more in the gas, which exists as a gas under standard conditions (0°C, 1 atm). For example, H ２ gas, unsaturated hydrocarbon-based gas (C ２ H ４ , C ２ H ２ , C ３ H ６ , etc.), saturated hydrocarbon-based gas (CH ４ , C ２ H ６, etc.), NH ３ Gas, coke oven gas, city gas, natural gas, etc., and mixtures thereof. Particularly preferred is H ２ Gas, unsaturated hydrocarbon gas (C ２ H ４ , C ２ H ２ , C ３ H ６ (etc.) H ２ The gas is preferable from the viewpoint of reducing carbon consumption per unit, as it does not contain carbon and does not cause a thermal decomposition reaction at the tuyeres. Furthermore, its low viscosity and density make it preferable from the viewpoint of permeability within the blast furnace. Unsaturated hydrocarbon gases are preferable because they contain double and triple bonds in their gas molecules, resulting in a relatively large heat of combustion per mol of oxygen, and they also serve as a heat source at the tuyeres. It is more preferable that the elemental composition ratio of H in the hydrogen-based reducing gas is 50 mol% or more. Also, the hydrogen-based reducing gas may contain other gases (e.g., N) (without impairing the effects of this embodiment). ２ A mixed gas with (or other gas) is also acceptable. It is preferable that the hydrogen-based reducing gas is heated before it is injected into the blast furnace 1. Heating the hydrogen-based reducing gas preheats the pulverized coal before it is injected into the blast furnace 1. This allows for a higher combustion rate of the pulverized coal. It is preferable that the hydrogen-based reducing gas is heated to, for example, 900°C or higher before being injected into the blast furnace 1. For this reason, the blast furnace 1 is equipped with a heating device 31 for heating the hydrogen-based reducing gas. The type of heating device 31 is not particularly limited and may be, for example, an electric heater.

[0025] Hydrogen-based reducing gas and the generated reducing gas rise within the furnace, reducing and heating the iron-based raw materials and coke. The iron-based raw materials descend within the furnace, being heated and reduced by the hydrogen-based reducing gas and the generated reducing gas. Subsequently, the iron-based raw materials melt and drip down the furnace while being further reduced by the coke. The iron-based raw materials are ultimately stored in the hearth section 5 as molten pig iron containing, for example, slightly less than 5% by mass of carbon. The molten pig iron from the hearth section 5 is removed from the tap and used in the next steelmaking process.

[0026] In this case, the reduction of iron-based raw materials is not only promoted by the reducing gas generated by the injection of the auxiliary reducing agent, but also by the injection of a hydrogen-based reducing gas. Therefore, the coke ratio (the mass of coke required to produce 1 ton of molten iron) and the auxiliary reducing agent ratio (the mass of auxiliary reducing agent required to produce 1 ton of molten iron; if the auxiliary reducing agent is pulverized coal, this becomes the pulverized coal ratio) can be reduced, thereby reducing the carbon consumption in the blast furnace 1.

[0027] <Structure of Tuyere 6> Next, the structure of the tuyere 6 used in the blast furnace 1 according to this embodiment will be described. Figure 2 is an enlarged cross-sectional view of the area around the tuyere 6 in Figure 1. As shown in Figure 2, the tuyere 6 comprises a tuyere body 6a, a gas reducing agent injection lance 11, and a solid reducing agent injection lance 17. The tuyere body 6a has a hot air passage 20. The confluence position 18 of the solid reducing agent injection lance 17 and the gas reducing agent injection lance 11 is preferably at the radial center within the gas reducing agent injection lance 11. The confluence position is at the center of the region within the gas reducing agent injection lance 11, which extends from the outlet 17a of the solid reducing agent injection lance 17 by the lance diameter of the solid reducing agent injection lance 17. Also, the lance diameter of the solid reducing agent injection lance 17 is smaller than the lance diameter of the gas reducing agent injection lance 11. Specifically, the lance diameter R of the gas reducing agent injection lance 11 ｇａｓ R of the lance diameter of the solid reducing agent blowing lance 17 ｓｏｌｉｄ Relationship (R ｓｏｌｉｄ / R ｇａｓ) is preferably 0.5 or less. The gaseous reducing agent injection lance 11 is installed along the injection direction of the hot air flow path 20. The outlet 11a of the gaseous reducing agent injection lance 11 is located inside the hot air flow path 20 of the tuyere body 6a. Examples of gaseous reducing agents include hydrogen-based reducing gases. The solid reducing agent injection lance 17 is connected to the gaseous reducing agent injection lance 11 upstream of the outlet 11a of the gaseous reducing agent injection lance 11. That is, the outlet 17a of the solid reducing agent injection lance 17 is located inside the gaseous reducing agent injection lance 11. Examples of solid reducing agents include coke, pulverized coal, biomass, and waste plastics. The solid reducing agent is not particularly limited, but since it is injected from the lance into the blast furnace 1, it is preferable that the particle size is less than 1 mm. It is also preferable that the solid reducing agent is injected using an inert gas containing nitrogen as a carrier gas. In Figure 2, the solid reducing agent injection lance 17 is shown to be installed above the gas reducing agent injection lance 11. However, it is sufficient that the outlet 17a of the solid reducing agent injection lance 17 is installed inside the gas reducing agent injection lance 11, and it may be installed at any position along the circumferential direction of the hot air flow path 20.

[0028] Figure 3 shows a conventional method in which an auxiliary reducing agent containing pulverized coal and a hydrogen-based reducing gas are injected into the blast furnace using a lance attached inside the tuyere. In the conventional method as shown in Figure 3, the hydrogen-based reducing gas and pulverized coal are not mixed, and the pulverized coal is attracted to the high-speed hydrogen-based reducing gas flow, making it difficult for the pulverized coal to disperse in the RW. In this embodiment, the outlet 17a of the solid reducing agent injection lance 17 is attached inside the gas reducing agent injection lance 11, so that high-temperature hydrogen and pulverized coal can be injected into the blast furnace 1 simultaneously from the outlet 11a of the gas reducing agent injection lance 11. With this configuration, the pulverized coal is heated by the high-temperature hydrogen before it is injected into the blast furnace 1, making it easier for the gasification and combustion reactions to proceed. In addition, it is less likely to be attracted to the high-speed hydrogen gas flow, and the pulverized coal tends to accumulate in the center of the tuyere opening 8. As a result, the pulverized coal is less likely to collide with the inner wall 6b of the tuyere body 6a. Furthermore, because the lance is not exposed to hot air containing oxygen or other air, and only contains hydrogen-based reducing gases, pulverized coal, and inert gases such as nitrogen which are carrier gases for the pulverized coal, the pulverized coal remains unburned inside the lance. Therefore, even when pulverized coal collides with the inner wall 6b of the tuyere, equipment wear is minimal.

[0029] (Confluence position of lances) Figure 4 shows the examination results of the confluence position 18 of the lances. The horizontal axis of the graph shown in Figure 4 represents the distance (mm) of pulverized coal from the confluence position 18, which is blown into the gaseous reducing material injection lance 11 from the solid reducing material injection lance 17, and the vertical axis represents the particle temperature (°C) of the pulverized coal in the lance. The measurement results describe the average temperature and minimum temperature of the pulverized coal blown into the lance. When the pulverized coal is blown into the blast furnace, it is preferably heated to 400°C or higher. This is because thermal decomposition of pulverized coal occurs at 400°C or higher, which can further promote combustion. Based on this, it can be seen from the results in Figure 4 that when the confluence position 18 of the gaseous reducing material injection lance 11 and the solid reducing material injection lance 17 is located 200 mm or more upstream from the outlet 11a of the gaseous reducing material injection lance 11, the average temperature exceeds 600°C, which is preferable. Furthermore, it can be seen that when the confluence position 18 is located 500 mm or more upstream from the outlet 11a of the gaseous reducing material injection lance 11, the minimum particle temperature exceeds 400°C, which is more preferable. Having the confluence position upstream of this value allows the pulverized coal to be blown into the blast furnace in a state where its temperature has been raised to 400°C or higher by the heat of high-temperature hydrogen, which is preferable from the perspective of promoting gasification and combustion reactions. There is no limitation on the upper limit of the confluence position, but the particle temperature will saturate beyond a certain extent.

[0030] In the above description, the outlet 17a of the solid reducing material injection lance 17 is configured to be installed inside the gaseous reducing material injection lance 11. However, a configuration may also be adopted in which the solid reducing material injection lance 17 is installed substantially parallel to the hot air flow channel 20, and the outlet 11a of the gaseous reducing material injection lance 11 is installed inside the solid reducing material injection lance 17. Even with this configuration, the pulverized coal flowing through the solid reducing material injection lance 17 can have its temperature raised by the high-temperature hydrogen-based reducing gas flowing through the gaseous reducing material injection lance 11 and then be blown into the blast furnace 1.

[0031] As described above, according to the tuyere and the blast furnace having the same of the present embodiment, by providing the blowout port 17a of the solid reducing material blowing lance 17 inside the gaseous reducing material blowing lance 17 provided in the tuyere 6 disposed at the lower part of the blast furnace 1, a solid reducing material containing pulverized coal and a gaseous reducing material containing hydrogen-based reducing gas are mixed, and the pulverized coal is blown into the blast furnace while being heated by the high-temperature hydrogen-based reducing gas. This configuration enables an operation in which the dispersion of pulverized coal in the raceway is improved, and the gasification and combustibility of pulverized coal are enhanced.

[0032] Hereinafter, the present disclosure will be specifically described by way of examples. The influence of the tuyere 6 attached to the blast furnace according to the present embodiment on the combustion rate of pulverized coal was evaluated by simulation. The calculation conditions are as shown in Table 1. Note that nitrogen gas was used as the carrier gas for pulverized coal, and pure hydrogen gas was used as the hydrogen-based reducing gas. The blowing temperature of hydrogen gas was set to 1090°C. In addition, the operation was performed with the merging position of the solid reducing material blowing lance 17 and the gaseous reducing material blowing lance 11 set at a position 1000 mm from the lance tip toward the upstream side of the gaseous reducing material blowing lance 11.

[0033]

[0034] Under the calculation conditions shown in Table 1, a simulation was performed on the combustion rate of pulverized coal achieved by the following blowing methods. The simulation results are shown in FIG. 5. • Pulverized coal lance type: As illustrated in FIG. 3, the solid reducing material blowing lance (pulverized coal lance) and the gaseous reducing material blowing lance (hydrogen lance) are located inside the hot air flow path. This is a conventional pulverized coal blowing method. • Blowing into hydrogen lance: As shown in FIG. 2, the blowout port of the solid reducing material blowing lance (pulverized coal lance) is provided inside the gaseous reducing material blowing lance (hydrogen lance), and this is a method of blowing pulverized coal into the inside of the gaseous reducing material blowing lance.

[0035] In Figure 5, the dispersibility of pulverized coal within the RW was evaluated by observing the distribution of pulverized coal passing through the cross-section of the RW. Figure 5 shows the distribution of pulverized coal passing through the cross-sections of the tuyere tip and the central part of the raceway, as confirmed by simulation. In this embodiment, the distribution of pulverized coal was evaluated in the central part of the RW, specifically in a cross-section perpendicular to the direction of airflow blown in from the tuyere, 500 mm from the tuyere tip. The diagram in Figure 5 showing the evaluation results of the pulverized coal distribution illustrates the tuyere opening 8. As shown in Figure 5, in the example of hydrogen lance injection, it can be seen that the pulverized coal is more dispersed in the central part of the RW than in the comparative example of conventional pulverized coal lance injection. Furthermore, the gasification and combustion rate of pulverized coal improved by 47% compared to the base pulverized coal lance type. This is thought to be because, in addition to the dispersion of pulverized coal within the RW, the pulverized coal is preheated within the hydrogen lance and blown into the tuyere and raceway in a state where the gasification and combustion reaction can proceed more easily. Therefore, this method of operating a blast furnace allows the reaction inside the furnace to proceed easily and reduces the reducing agent ratio. Furthermore, when examining the distribution of pulverized coal at the tip of the tuyeres, it can be seen that in this embodiment, the pulverized coal is concentrated in the center of the tuyeres opening 8. This means that collision of pulverized coal with the inner wall 6b of the tuyeres is suppressed, and wear of the tuyeres is prevented. Thus, it was found that the blast furnace operating method according to this embodiment allows for more stable blast furnace operation than the conventional pulverized coal lance blowing method used in the comparative example.

[0036] From the above results, it was found that the blast furnace, blast furnace operating method, and tuyeres according to this embodiment improve the combustion rate of pulverized coal and enable operation with a reduced reducing agent ratio.

[0037] While preferred embodiments of the present disclosure have been described in detail above with reference to the attached drawings, the present disclosure is not limited to such examples. It is clear to any person with ordinary skill in the art to which the present disclosure pertains that various modifications or alterations may be conceived within the scope of the technical idea set forth in the claims, and these will naturally also be understood to fall within the technical scope of the present disclosure.

[0038] 1. Blast furnace 1a. Top of furnace 1b. Bottom of furnace 2. Shaft section 3. Belly section 4. Bosch section 5. Hearth section 6. Tuyer 6a. Tuyer body 6b. Tuyer inner wall 8. Tuyer opening 10. Blower 11. Gas reducing agent injection lance 11a. Outlet 17. Solid reducing agent injection lance 17a. Outlet 18. Lance confluence position 20. Hot air flow path 25. Hydrogen-based reducing gas supply system 30. Hydrogen-based reducing gas tank 31. Heating device

Claims

1. A blast furnace having a tuyere, wherein the tuyere comprises a tuyere body, a gaseous reducing agent injection lance, and a solid reducing agent injection lance, the tuyere body having a hot air passage, and either the gaseous reducing agent injection lance or the solid reducing agent injection lance having an outlet within the hot air passage, and the other lance having an outlet inside the first lance.

2. The blast furnace according to claim 1, wherein the gaseous reducing agent injection lance has the outlet in the hot air flow path, and the solid reducing agent injection lance has the outlet inside the gaseous reducing agent injection lance.

3. The blast furnace according to claim 1, further comprising a heating device for heating a gaseous reducing agent.

4. A method for operating a blast furnace according to any one of claims 1 to 3, wherein hot air is flowed through the hot air passage of the tuyere body, a gaseous reducing agent or a solid reducing agent is blown out from the outlet of the other lance inside the one lance, and the gaseous reducing agent and the solid reducing agent are blown out from the outlet of the one lance.

5. A tuyere for use in a blast furnace, wherein the tuyere comprises a tuyere body, a gaseous reducing agent injection lance, and a solid reducing agent injection lance, wherein the tuyere body has a hot air passage, and either the gaseous reducing agent injection lance or the solid reducing agent injection lance has an outlet within the hot air passage, and the other lance has an outlet inside the first lance.

6. The tuyeres according to claim 5, wherein the gaseous reducing agent blowing lance has an outlet in the hot air passage, and the solid reducing agent blowing lance has an outlet inside the gaseous reducing agent blowing lance.

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