Blast furnace tuyere apparatus and blast furnace operation method

Abstract

A tuyere apparatus according to the present invention comprises: an outer circulation hole disposed on the outermost peripheral side inside a tuyere; and an inner circulation hole disposed on the inner peripheral side of the outer circulation hole. The inner circulation hole has two or more independent flow paths, the two or more independent flow paths being separated from the inner surface of the tuyere. A blast furnace operation method according to the present invention comprises, using the above-described blast furnace tuyere apparatus in a blast furnace: blowing a low oxygen concentration gas, a high oxygen concentration gas having an oxygen concentration higher than that of the low oxygen concentration gas, and a reduction material from the tuyere; blowing the low concentration oxygen gas from the outer circulation hole; blowing the high oxygen concentration gas and the reduction material from the inner circulation hole; and blowing the high oxygen concentration gas and the reduction material separately from the two or more independent flow paths.

Description

Blast furnace tuyere equipment and blast furnace operation method

[0001] The present invention relates to a tuyere system for a blast furnace and a method for operating a blast furnace using the tuyere system.

[0002] In recent years, against the backdrop of global environmental issues, carbon dioxide (CO ２ Therefore, in the operation of blast furnaces installed in steelworks, there is a demand to reduce the amount of carbon raw material newly input by improving reaction efficiency or recycling regeneration gas.

[0003] In a typical blast furnace, hot air (air heated to about 1200°C) is blown into the furnace from the tuyere as blast gas. The oxygen in this hot air reacts with the carbon in the coke and pulverized coal, which are reducing agents, to produce carbon monoxide (CO) gas and hydrogen (H ２ These carbon monoxide and hydrogen gases reduce the iron oxide in the iron ore charged into the blast furnace, and carbon dioxide is generated by the reduction reaction in which oxygen converts from the iron oxide to carbon monoxide.

[0004] As a technology for reducing the amount of carbon dioxide emitted in the operation of a blast furnace, a technology has been proposed in which carbon monoxide and carbon dioxide contained in by-product gases emitted from the blast furnace or the like are reformed to produce hydrocarbons such as methane and ethanol, and the produced hydrocarbons are then reintroduced into the blast furnace as reducing agents, thereby reducing the amount of reducing agent newly charged.As a technology for maximizing the use of these recycled reducing agents and minimizing the amount of reducing agent newly charged into the blast furnace, for example, Patent Document 1 proposes using oxygen gas as a blast gas.

[0005] The blast gas is injected into the blast furnace using, for example, a tuyere provided on the side wall at the bottom of a blast furnace body 1 as shown in Fig. 1. As shown in Fig. 2, for example, the tuyere equipment of a blast furnace is composed of an assembly of a plurality of parts such as a blowpipe 2, a small tuyere 3, an injection lance 4, a curved pipe 6, a straight pipe 7, a large tuyere 8, and a tuyere receiving metal fitting 9. The inside of the tuyere is under high-pressure conditions of about 400 kPa, so the connecting parts of the tuyere have a sealed structure to prevent leakage of the gas flowing inside.

[0006] As shown in Figure 3, the tip of the tuyere equipment of a blast furnace is exposed to an environment where high-temperature molten pig iron and molten slag flow downward together with high-temperature gases generated by the combustion of coke, etc. The blast gas blown into the coke packed bed in the blast furnace from the tip of the small tuyere 3 causes the coke in front of the tuyere to swirl and burn using its kinetic energy, forming a space called a raceway 5 about 1 m from the tip of the tuyere to the inside of the furnace. The formation of the raceway 5 separates the position where the highest temperature of the combustion reaction occurs and the drip area of ​​the high-temperature molten material from the tip of the tuyere to the inside of the blast furnace, thereby suppressing the thermal load at the tip of the tuyere.

[0007] As shown in Patent Documents 2 to 5, techniques have been developed to improve reaction efficiency by promoting agitation contact between the auxiliary reducing agent and oxygen. All of these techniques involve mixing the auxiliary reducing agent and a small amount of auxiliary oxygen gas into the heated air from an injection lance in an operation in which the blast gas is based on heated air.

[0008] International Publication No. 2021 / 106579 Pamphlet Japanese Patent Application Laid-Open No. 6-330113 Japanese Patent Application Laid-Open No. 11-12613 International Publication No. 2018 / 180892 Pamphlet Japanese Patent Application Laid-Open No. 2013-19006

[0009] In the conventional tuyere equipment configuration of a blast furnace, when oxygen gas comes into direct contact with the connecting parts of the tuyere, there is a slight possibility that highly oxidizing high-oxygen concentration gas will leak from the connecting parts of the tuyere.If high-oxygen concentration gas leaks, it could cause equipment damage such as abnormal combustion and lead to operational problems.

[0010] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a blast furnace tuyere equipment that uses a high-oxygen concentration gas mainly composed of oxygen as a blast gas, and that can suppress leakage of the high-oxygen concentration gas from the tuyere connection, and a blast furnace operating method using the tuyere equipment.

[0011] The gist of the present invention is as follows: (1) A tuyere facility for a blast furnace, comprising an outer flow hole disposed on the outermost side inside a tuyere, and an inner flow hole disposed on the inner side of the outer flow hole, wherein the inner flow hole has two or more independent flow paths, and the two or more independent flow paths are spaced apart from the inner surface of the tuyere.

[0012] (2) The tuyere equipment for a blast furnace according to (1), wherein the tuyere comprises a small tuyere and a blowpipe, a blowpipe is disposed inside the small tuyere and on the inner circumferential side of the blowpipe, spaced apart from the small tuyere, the outer flow hole is disposed between the small tuyere and the blowpipe and the blowpipe, and the inner flow hole is disposed inside the blowpipe.

[0013] (3) The tuyere equipment for a blast furnace according to (2), wherein the joint between the small tuyere and the blowpipe has a joint structure.

[0014] (4) A blast furnace tuyere facility according to any one of (1) to (3), wherein in the inner flow hole, at least one of the two or more independent flow paths has a narrowing shape toward the downstream side.

[0015] (5) A blast furnace tuyere facility according to any one of (2) to (4), wherein the clearance between the small tuyere and the blowing pipe is 20% or more of the inner diameter of the small tuyere.

[0016] (6) The tuyere equipment for a blast furnace according to any one of (2) to (5), wherein the blowing pipe has a water cooling mechanism.

[0017] (7) The tuyere facility for a blast furnace according to any one of (2) to (6), wherein the blowing pipe is connected to the blowpipe at a rear end of the blowpipe.

[0018] (8) A blast furnace tuyere facility according to any one of (2) to (7), comprising a mixing promotion structure having a conducting section that connects at least two of the two or more independent flow paths at the outlet of the blowing pipe.

[0019] (9) A method for operating a blast furnace using the blast furnace tuyere equipment according to any one of (1) to (8), characterized in that in the blast furnace, a low-oxygen concentration gas, a high-oxygen concentration gas having an oxygen concentration higher than that of the low-oxygen concentration gas, and a reducing agent are blown through the tuyere, the low-oxygen concentration gas is blown through the outer flow hole, the high-oxygen concentration gas and the reducing agent are blown through the inner flow hole, and the high-oxygen concentration gas and the reducing agent are blown separately through the two or more independent flow paths.

[0020] (10) The method for operating a blast furnace according to (9), wherein the gas flow velocity of the high-oxygen-concentration gas is 180 m / s or more downstream of the tuyere and 60 m / s or less upstream of the tuyere.

[0021] (11) The method for operating a blast furnace according to (9) or (10), wherein the reducing material includes at least one of blast furnace gas, coke oven gas, ammonia, carbon monoxide, hydrogen, methane, ethane, ethylene, acetylene, propane, propylene, propyne, butane, butene, butyne, methanol, ethanol, and dimethyl ether.

[0022] According to the present invention, it is possible to provide a blast furnace tuyere equipment that uses a high-oxygen concentration gas mainly composed of oxygen as a blast gas, and that can suppress leakage of the high-oxygen concentration gas from the tuyere connection, and a blast furnace operating method using the tuyere equipment.

[0023] FIG. 4 is a schematic cross-sectional view illustrating the structure of a blast furnace. FIG. 5 is a schematic cross-sectional view illustrating the structure of a conventional blast furnace tuyere equipment. FIG. 6 is a view illustrating the structure of a tip portion of a blast furnace tuyere equipment. FIG. 7 is a schematic cross-sectional view illustrating the structure of a blast furnace tuyere equipment according to one embodiment of the present invention. FIG. 8 is a partial schematic cross-sectional view illustrating the structure of the tip portion of the tuyere equipment of FIG. 4. FIG. 9 is a partial cross-sectional view showing a first example of a mixing promotion structure. FIG. 10 is a partial cross-sectional view showing a second example of a mixing promotion structure. FIG. 11 is a partial cross-sectional view showing a third example of a mixing promotion structure. FIG. 12 is a partial cross-sectional view (left) showing a fourth example of a mixing promotion structure and a cross-sectional view (right) perpendicular to the extending direction of the blowing pipe. FIG. 13 is a partial cross-sectional view (left) showing a fifth example of a mixing promotion structure and a cross-sectional view (right) perpendicular to the extending direction of the blowing pipe.

[0024] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0025] <Blast Furnace Tuyere Equipment> A blast furnace tuyere equipment according to one embodiment of the present invention will be described. The tuyere equipment of this embodiment is used for an operation in which a blast gas (mainly a gas with a high oxygen concentration) and a reducing agent are injected into the blast furnace.

[0026] The tuyere equipment of this embodiment can be, for example, a tuyere equipment used in a blast furnace as shown in Fig. 1. The tuyere equipment is arranged on a side wall at the bottom of a blast furnace body 1. Fig. 4 is a schematic cross-sectional view for explaining the structure of a tuyere equipment for a blast furnace according to one embodiment of the present invention. Fig. 5 is a partial schematic cross-sectional view for explaining the structure of the tip portion of the tuyere equipment of Fig. 4.

[0027] 4 and 5, the tuyere equipment of this embodiment comprises a blowpipe 2, a small tuyere 3, a curved pipe 6, a large tuyere 8, a tuyere receiving metal fitting 9, and an injection pipe 10. The tuyere equipment of this embodiment comprises a tuyere, which comprises a small tuyere 3, a blowpipe 2, and an injection pipe 10. A raceway 5 is formed at the end of the tuyere.

[0028] The blowpipe 2 is a pipe for guiding the low-oxygen concentration gas introduced from the bent pipe 6 to the small tuyere 3. The blowpipe 2 is preferably made of a heat-resistant material. As shown in the figure, the tip of the blowpipe 2 is connected to the rear end of the small tuyere 3 inside the large tuyere 8.

[0029] The small tuyere 3 is a pipe that guides the blast gas introduced from the blowpipe 2 into the furnace. The small tuyere 3 is disposed in a state that it protrudes into the blast furnace, and is in direct contact with the atmosphere inside the blast furnace.

[0030] The curved pipe 6 is a pipe that guides the blow gas to the blowpipe 2 .

[0031] The curved pipe 6, the blowpipe 2, and the small tuyere 3 are connected in this order. In this embodiment, the joint between the small tuyere 3 and the blowpipe 2 has a sliding joint structure. That is, the small tuyere 3 and the blowpipe 2 are joined without using a strong connection such as bolt fastening, but each joint is constructed by a sliding joint of smooth spherical surfaces, which firmly adhere to each other, and when the small tuyere 3 is displaced, the sliding action of the spherical surfaces makes it possible to prevent gas leakage and absorb displacement. Similarly, in this embodiment, the joint between the blowpipe 2 and the curved pipe 6 also has a sliding joint structure. With this structure, even when the small tuyere 3 is displaced due to thermal expansion and contraction caused by temperature fluctuations in the high-temperature region of the blast furnace exceeding 2000°C, the sliding action of the spherical surfaces makes it possible to absorb displacement (while preventing gas leakage), and therefore damage to the equipment can be prevented.

[0032] The tip of the large tuyere 8 cantilever-supports the rear end of the small tuyere 3. The inside diameter of the tip of the large tuyere 8 is approximately equal to the outside diameter of the rear end of the small tuyere 3. The large tuyere 8 and the small tuyere 3 can be fitted together as described above, or can be fixed together using fixing devices such as bolts.

[0033] The tuyere holder 9 supports the rear end of the large tuyere 8 at its tip, thereby securely fixing the small tuyere 3 and the large tuyere 8 to the lower side wall of the blast furnace body 1. As shown in the figure, the inner diameter of the tip of the tuyere holder 9 and the outer diameter of the rear end of the large tuyere 8 are approximately equal.

[0034] The blowing pipe 10 is a pipe for blowing the blast gas and the reducing agent into the furnace. The blowing pipe 10 is connected to the rear end of the blowpipe 2. In this embodiment, a high-oxygen concentration gas is mainly used as the blast gas.

[0035] As shown in Figures 4 and 5, the tuyere equipment includes an outer flow hole 13 located on the outermost side inside the tuyere, and a blowing pipe 10 located on the inner periphery of the outer flow hole 13. The blowing pipe 10 is located inside the small tuyere 3 and on the inner periphery of the blowpipe 2, spaced apart from the small tuyere 3. The outer flow hole 13 is located between the small tuyere 3 and the blowpipe 2 and the blowing pipe 10. An inner flow hole is located inside the blowing pipe 10. The inner flow hole has two or more independent flow passages. In this example, the two or more independent flow passages are an intermediate flow hole 12 located on the inner periphery of the outer flow hole 13, and a central flow hole 11 located further inner than the intermediate flow hole 12. In this example, the two or more independent flow passages have a double-pipe structure, but they may also have a triple-pipe or more double-pipe structure, or they may be formed by arranging a plurality of single pipes, for example. The intermediate flow hole 12 and the central flow hole 11 are installed at any position outside the furnace from the tip of the tuyere, and the gas ejected from each flow hole at the tip of the injection pipe 10 can be injected into the blast furnace as a mixed gas.

[0036] The outer circulation holes 13 are holes through which a low-oxygen concentration gas flows. The "low oxygen concentration" may be any oxygen concentration that does not burn the tuyere equipment or the surrounding equipment outside the tuyere even if it comes into contact with the equipment, and for example, an oxygen concentration of 35% or less (0 to 35%) is preferable. The low-oxygen concentration gas may be, for example, air or other gases (such as nitrogen gas (which may be nitrogen gas containing no oxygen)). Furthermore, a reducing agent may be circulated through the outer circulation holes 13. Since there is no risk of abnormal oxidation occurring even when the low-oxygen concentration gas and the reducing agent are heated to a high temperature, they may be heated to a high temperature and then blown in.

[0037] The inner circulation holes are holes for passing a high-oxygen concentration gas or a reducing agent having an oxygen concentration higher than that of the low-oxygen concentration gas (passed through the outer circulation holes 13). A "high oxygen concentration" preferably means, for example, an oxygen concentration of more than 35% (more than 35% but not more than 100%). High-oxygen concentration gas may cause abnormal oxidation of the flow path piping if heated to high temperatures, so it is preferably passed at a temperature of 800°C or less, and more preferably at room temperature. The inner circulation holes have at least two or more independent flow paths (in this example, two flow paths: the intermediate circulation hole 12 and the central circulation hole 11) through which the high-oxygen concentration gas and the reducing agent pass, respectively, through separate flow paths. By passing the high-oxygen concentration gas and the reducing agent through separate flow paths, operational problems such as ignition and abnormal combustion within the flow paths can be prevented.

[0038] The intermediate flow hole 12 is a hole through which a high-oxygen concentration gas having an oxygen concentration higher than that of the low-oxygen concentration gas flows.

[0039] The central flow hole 11 is a hole through which the reducing material flows. A solid reducing material or a gaseous reducing material can be used as the reducing material. It is particularly preferable to use a gaseous reducing material. In this case, the reducing material preferably contains at least one of blast furnace gas, coke oven gas, ammonia, carbon monoxide, hydrogen, methane, ethane, ethylene, acetylene, propane, propylene, propyne, butane, butene, butyne, methanol, ethanol, and dimethyl ether. When a solid reducing material is used, granular reducing materials such as pulverized coal and waste plastics can be used.

[0040] Here, in the tuyere equipment of this embodiment, the two or more independent flow paths (in this example, the intermediate flow holes 12 and the central flow hole 11) are separated from the inner surface 15 of the tuyere. In this example, an outer flow hole 13, which is another flow path (a flow path for circulating a low-oxygen concentration gas), is interposed between the two or more independent flow paths and the inner surface 15 of the tuyere.

[0041] The effects of the tuyere equipment for a blast furnace of this embodiment will be described below. The tuyere equipment for a blast furnace of this embodiment includes outer flow holes 13 arranged on the outermost side inside the tuyere and inner flow holes arranged on the inner side of the outer flow holes 13. The inner flow holes have two or more independent flow passages (in this example, intermediate flow holes 12 and central flow hole 11), and the two or more independent flow passages are separated from the inner surface 15 of the tuyere. In this configuration, by injecting the low-oxygen concentration gas through the outer flow hole 13, the high-oxygen concentration gas and the reducing agent through the inner flow hole, and injecting the high-oxygen concentration gas and the reducing agent separately through the two or more independent flow paths, the flow path into which the high-oxygen concentration gas is injected is separated from the inner surface 15 of the tuyere, so that the high-oxygen concentration gas does not come into contact with the inner surface 15 of the tuyere (even if it leaks from the flow path, it will be mixed with the low-oxygen concentration gas before coming into contact with the inner surface 15 of the tuyere), thereby preventing leakage of the high-oxygen concentration gas from the connecting parts of the tuyere parts, which are prone to gas leakage, and avoiding problems such as equipment damage due to abnormal combustion. Thus, the tuyere equipment for a blast furnace of this embodiment can prevent leakage of the high-oxygen concentration gas from the tuyere connecting parts in a blast furnace that uses a high-oxygen concentration gas mainly composed of oxygen as a blast gas. In particular, when the joint between the small tuyere 3 and the blowpipe 2 has a joint structure, as described above, while the effect of preventing damage to the equipment by absorbing displacement due to thermal expansion and contraction caused by temperature fluctuations can be obtained, the problem of leakage of high-oxygen concentration gas from the joint between the tuyere parts becomes more pronounced, so in such cases the configuration of the tuyere equipment of this embodiment is particularly effective. Also, as described above, the inner circulation hole has two or more independent flow paths (in this example, the intermediate circulation hole 12 and the central circulation hole 11), and therefore, by flowing the high-oxygen concentration gas and the reducing agent through separate flow paths, it is possible to prevent operational problems such as ignition and abnormal combustion within the flow paths.

[0042] In specific terms, the tuyere comprises a small tuyere 3 and a blowpipe 2, and a blowing pipe 10 is arranged inside the small tuyere 3 and on the inner circumferential side of the blowpipe 2, spaced apart from the small tuyere 3, and an outer flow hole 13 is arranged between the small tuyere 3 and the blowpipe 2 and the blowing pipe 10, and it is preferable that an inner flow hole is arranged inside the blowing pipe 10.

[0043] When high-oxygen gas is used as the blast gas for a blast furnace, the gas flow velocity at the tuyere tip is reduced compared to conventional air blast due to the lack of nitrogen in the blast gas. As a result, a sufficiently large raceway 5 is not formed, and the dripping area of ​​the high-temperature molten material may approach the tip of the tuyere, resulting in frequent tuyere damage. Therefore, to form a sufficiently large raceway 5 and reduce the thermal load on the tuyere, it is desirable to reduce the cross-sectional area of ​​the high-oxygen gas flow path and increase the discharge gas flow velocity into the blast furnace. However, because high-oxygen gas has a high oxidizing power, simply reducing the cross-sectional area of ​​the high-oxygen gas flow path in the injection pipe 10 and allowing it to flow at a high velocity may result in abnormal oxidation of the piping due to friction, which may cause damage to the piping equipment. Therefore, as shown in Figures 4 and 5, it is preferable that at least one of the two or more independent flow paths in the inner flow hole (in this example, the intermediate flow hole 12) has a downstream-oriented constricted shape. By adopting such a configuration, the flow velocity of the high-oxygen concentration gas is prevented from becoming too high upstream to prevent damage to the piping equipment, while the flow velocity of the high-oxygen concentration gas is made sufficiently high downstream to form a sufficiently large raceway, thereby suppressing the thermal load on the tuyere and preventing damage to the tuyere.

[0044] More specifically, it is preferable that the flow velocity of the high-oxygen concentration gas be 60 m / s or less in the upstream section and 180 m / s to 250 m / s in the downstream section. Setting the oxygen flow velocity in the upstream section to 60 m / s or less can prevent abnormal oxidation of the piping due to friction. On the other hand, setting the flow velocity in the downstream section to 180 m / s or more can more reliably form a raceway. Setting the flow velocity in the downstream section to 250 m / s or less can prevent excessive piping pressure loss, resulting in an insufficient gas flow. As an example, the "upstream section" can be located upstream of the tip of the blowpipe 2, and therefore the flow velocity of the high-oxygen concentration gas can be 60 m / s or less upstream of the tip of the blowpipe 2. As another example, the "downstream section" can be located at the tip of the small tuyere 3, and the flow velocity of the high-oxygen concentration gas at this position can be set to 180 m / s to 250 m / s.

[0045] In order to achieve the above-described preferable flow rate conditions for the high-oxygen-concentration gas, it is preferable that the holes through which the high-oxygen-concentration gas flows (in this example, the intermediate flow holes 12) have a tapered shape extending downstream. In this example, as shown in the figure, the intermediate flow holes 12 have a large cross-sectional area portion on the upstream side and a small cross-sectional area portion (smaller than the large cross-sectional area portion) on the downstream side, which are smoothly connected. The cross-sectional area of ​​the large cross-sectional area portion is preferably three times or more, more preferably four times or more, the cross-sectional area of ​​the small cross-sectional area portion. As shown in FIG. 5 , the connection position (connection region) between the large cross-sectional area portion and the small cross-sectional area portion is preferably located inside the small tuyere 3, from the viewpoint of reducing the flow rate of the high-oxygen-concentration gas. In the illustrated example, the large cross-sectional area portion and the small cross-sectional area portion each have a substantially constant cross-sectional area, but either or both of the large cross-sectional area portion and the small cross-sectional area portion may have a shape in which the cross-sectional area gradually decreases downstream.

[0046] The gas flow rate of the high-oxygen concentration gas varies depending on the operating conditions of the blast furnace, but minor changes in operation will not pose a problem if the flow path cross-sectional area is optimized as described above. However, if the operating conditions change significantly, the same tuyere equipment will no longer be able to maintain the appropriate flow rate conditions. In that case, the flow path cross-sectional area of ​​the high-oxygen concentration gas flow path can be changed and optimized by modifying the equipment. When a removable injection pipe 10 is used, the flow path cross-sectional area can be easily changed, so it is possible to prepare injection pipes 10 of multiple shapes in anticipation of changes in operating conditions and to use them by switching them as appropriate to suit the operating conditions. 5, if there is concern that the small tuyere 3 may be damaged due to the effects of high-temperature molten material or the like (for example, if the tuyere cooling water temperature rises abnormally), it is advisable to flow high-temperature air, reducing gas, nitrogen gas or other low-oxygen concentration gas through the outer flow holes 13, and adjust the outer diameter of the tip of the blowing pipe 10 and the inner diameter of the small tuyere 3 to reduce the cross-sectional area of ​​the flow path for the low-oxygen concentration gas, increase the outflow gas velocity of the tuyere, and secure a large space for the raceway 5, the image of which is shown in Figure 3, thereby separating the drip region of the high-temperature molten material from the tip of the tuyere toward the inside of the furnace. This makes it possible to reduce or adjust the thermal load on the tip of the small tuyere 3.

[0047] Here, it is preferable that the clearance between the small tuyere 3 and the blowing pipe 10 (the distance at the tip (see the two-way arrow in Figure 5)) be 20% or more of the inner diameter of the small tuyere 3 (the inner diameter at the tip). The position of the small tuyere 3 fluctuates due to thermal fluctuations inside the blast furnace or physical collisions with the raw materials inside the blast furnace. At this time, the small tuyere 3 and the blowing pipe 10 are arranged at a distance from each other, but if the displacement of the small tuyere 3 is too large, there is a possibility that the small tuyere 3 and the blowing pipe 10 will come into contact. If the small tuyere 3 and the blowing pipe 10 come into contact, a large force will be applied to the blowing pipe 10, through which the high-oxygen concentration gas flows, damaging the flow path of the high-oxygen concentration gas and causing leakage of the high-oxygen concentration gas. Therefore, it is preferable to design the small tuyere 3 so that it will not come into contact with the blowing pipe 10 and be damaged if it fluctuates. It is expected that the small tuyere 3 may be displaced by up to 20% of its inner diameter due to the effects of thermal expansion and contraction of surrounding equipment, etc., so the clearance between the small tuyere 3 and the blowing pipe 10 is preferably 20% or more, and more preferably 30% or more, of the inner diameter of the small tuyere 3. In order to ensure the clearance between the small tuyere 3 and the blowing pipe 10 while also ensuring an appropriate cross-sectional area for the high-oxygen concentration gas flow path, the connection position (connection region) between the large cross-sectional area section and the small cross-sectional area section of the throttle shape of the high-oxygen concentration gas flow path should be located upstream of the small tuyere 3, for example, inside the blowpipe 2, from the perspective of ensuring the above clearance. This makes it possible to maintain a sufficient clearance between the small tuyere 3 and the blowing pipe 10 throughout the entire interior of the small tuyere 3. Furthermore, from the perspective of achieving both a reduction in the flow rate of the high-oxygen concentration gas and ensuring the above clearance, the connection position (connection region) between the large area section and the small area section is preferably located near the tip of the blowpipe 2.

[0048] The blowing pipe 10 preferably has a water-cooling mechanism 14. In this example, the water-cooling mechanism 14 is a hole through which cooling water can flow, and is adjacent to the outer circulation hole 13. In this example, the water-cooling mechanism 14 has an outward path and a return path, and the outward path and the return path are separated by a wall. By providing such a water-cooling mechanism 14, it is possible to protect the blowing pipe 10 even when, for example, heated air is circulated through the outer circulation hole 13, and the effect of suppressing abnormal oxidation can be further improved.

[0049] As described above, the blowing pipe 10 is connected to the rear end of the blowpipe 2. The blowing pipe 10 attached to the rear end of the blowpipe 2 can be configured to be detachable by providing an attachment part. By appropriately replacing the blowing pipe 10 with one having an appropriately set flow passage thickness of each flow hole so that the flow passage cross-sectional area satisfies the appropriate gas flow velocity condition, the gas flow velocity condition can be optimized even when the operating conditions of the blast furnace change.

[0050] The tuyere equipment is preferably provided with a mixing promotion structure for mixing the high-oxygen concentration gas and the reducing agent inside the injection pipe 10. Such a mixing promotion structure preferably has a conduit at the outlet of the injection pipe that connects at least two of the two or more independent flow paths. This promotes mixing of the high-oxygen concentration gas and the reducing agent inside the injection pipe 10, thereby improving the combustibility of the reducing agent. When the combustibility of the reducing agent is improved, the gas volume increases due to combustion expansion, allowing the size of the raceway 5 to be further increased, making it possible to further suppress the thermal load on the tuyere. In particular, it is preferable to provide such a mixing promotion structure at the tip of the injection pipe 10.

[0051] 6A to 6E show specific examples of the mixing promotion structure. In the example shown in FIG. 6A, the flow path of the blowing pipe 10 has a double-pipe structure. As described above, the outer circumferential side can have intermediate flow holes 12 and the inner circumferential side can have a central flow hole 11. In this case, as shown in the figure, the tip of the pipe (the inner pipe of the double pipe) located at the boundary between the central flow hole 11 and the intermediate flow hole 12 is positioned upstream of the tip of the blowing pipe 10. With this configuration, the reducing agent flowing through the central flow hole 11 and the high-oxygen concentration gas flowing through the intermediate flow hole 12 begin to mix upstream of the blowing pipe 10, thereby promoting mixing of the reducing agent and the high-oxygen concentration gas inside the blowing pipe 10.

[0052] In the example shown in Fig. 6B, in addition to the structure shown in Fig. 6A, a taper is provided on the inner surface of the outer periphery of the inner pipe of the double pipe, with the diameter narrowing toward the downstream side. With this configuration, the outer flow (high-oxygen concentration gas) collides inward with the inner flow (reducing material), further promoting mixing of the outer flow and the inner flow.

[0053] In the example shown in Figure 6C, in addition to the structure shown in Figure 6A, the outer surface of the tip of the inner pipe of the double pipe is milled so that the outer flow path widens toward the downstream side. With this configuration, the outer flow collides inward with the inner flow, further promoting mixing of the outer flow and the inner flow.

[0054] In the examples shown in Figures 6D and 6E, in addition to the structure shown in Figure 6A, portions of the outer flow passage (four to eight locations in the circumferential direction) (eight locations in the example of Figure 6D, four locations in the example of Figure 6E) are blocked to make the outer flow passage porous. This strengthens the turbulence and further promotes mixing of the outer flow and the inner flow. In addition, by providing through-holes connecting the central flow hole 11 and the middle flow hole 12 in the inner pipe of the double pipe at a position upstream of the blocked flow passage, mixing of the outer flow and the inner flow can be further promoted. Note that in the examples of Figures 6D and 6E, the flow passages are blocked at equal intervals around the circumference, but the flow passages can also be blocked at different intervals around the circumference.

[0055] <Blast Furnace Operation Method> Next, a blast furnace operation method according to one embodiment of the present invention will be described. As an example, the blast furnace operation method according to this embodiment can be performed in a blast furnace equipped with the tuyere equipment of the embodiment described above. Such an embodiment of the tuyere equipment has already been described, so a repeated description will be omitted.

[0056] In the blast furnace operating method of this embodiment, a low-oxygen concentration gas, a high-oxygen concentration gas having an oxygen concentration higher than that of the low-oxygen concentration gas, and a reducing agent are injected into the blast furnace from the tuyere, the low-oxygen concentration gas is injected from the outer flow hole 13, the high-oxygen concentration gas and the reducing agent are injected from the inner flow hole, and the high-oxygen concentration gas and the reducing agent are injected separately from two or more independent flow paths (for example, an intermediate flow hole 12 and a central flow hole 11).

[0057] According to the method for operating a blast furnace of this embodiment, the flow path into which the high-oxygen concentration gas is blown is separated from the inner surface 15 of the tuyere, so that the high-oxygen concentration gas does not come into contact with the inner surface 15 of the tuyere (even if the high-oxygen concentration gas leaks from the flow path, it is mixed with the low-oxygen concentration gas before coming into contact with the inner surface 15 of the tuyere). This makes it possible to prevent leakage of the high-oxygen concentration gas from the connecting parts of the tuyere parts, which are prone to gas leakage, and to avoid problems such as equipment damage due to abnormal combustion. As described above, the method for operating a blast furnace of this embodiment makes it possible to prevent leakage of the high-oxygen concentration gas from the connecting parts of the tuyere parts in tuyere equipment that uses a high-oxygen concentration gas mainly composed of oxygen as the blast gas. In particular, when the joint between the small tuyere 3 and the blowpipe 2 has a slip-fit ​​structure, as described above, the effect of preventing equipment damage by absorbing displacement due to thermal expansion and contraction caused by temperature fluctuations is obtained, but the problem of leakage of the high-oxygen concentration gas from the connecting parts of the tuyere parts becomes more pronounced. Therefore, the method for operating a blast furnace of this embodiment is particularly effective in such cases. Furthermore, as described above, the inner circulation hole has two or more independent flow paths (in this example, the intermediate circulation hole 12 and the central circulation hole 11). Therefore, by flowing the high-oxygen concentration gas and the reducing agent through separate flow paths, it is possible to prevent operational problems such as ignition and abnormal combustion within the flow paths.

[0058] As described above, it is preferable that the flow velocity of the high-oxygen concentration gas be 60 m / s or less in the upstream section and 180 m / s to 250 m / s or less in the downstream section. Setting the oxygen flow velocity in the upstream section to 60 m / s or less can prevent abnormal oxidation of the piping due to friction. Setting the flow velocity in the downstream section to 180 m / s or more can more reliably form the raceway 5. Setting the flow velocity in the downstream section to 250 m / s or less can prevent excessive piping pressure loss, resulting in an insufficient gas flow. As an example, the upstream section can be located upstream of the tip of the blowpipe 2, and therefore the flow velocity of the high-oxygen concentration gas can be 60 m / s or less upstream of the tip of the blowpipe 2. As another example, the downstream section can be located at the tip of the small tuyere 3, and the flow velocity of the high-oxygen concentration gas at this position can be set to 180 m / s to 250 m / s.

[0059] As described above, in the method of this embodiment, a solid reducing agent or a gaseous reducing agent can be used as the reducing agent. It is particularly preferable to use a gaseous reducing agent. In this case, the reducing agent preferably contains at least one of blast furnace gas, coke oven gas, ammonia, carbon monoxide, hydrogen, methane, ethane, ethylene, acetylene, propane, propylene, propyne, butane, butene, butyne, methanol, ethanol, and dimethyl ether. When a solid reducing agent is used, granular reducing agents such as pulverized coal and waste plastics can be used.

[0060] 1: blast furnace body, 2: blowpipe, 3: small tuyere, 4: blowing lance, 5: raceway, 6: curved pipe, 7: straight pipe, 8: large tuyere, 9: tuyere receiving metal fitting, 10: blowing pipe, 11: central flow hole, 12: intermediate flow hole, 13: outer flow hole, 14: water cooling mechanism, 15: inner surface of tuyere

Claims

1. A tuyere installation for a blast furnace, comprising an outer flow hole arranged on the outermost side inside the tuyere, and an inner flow hole arranged on the inner side of the outer flow hole, wherein the inner flow hole has two or more independent flow paths, and the two or more independent flow paths are separated from the inner surface of the tuyere.

2. Tuyere equipment for a blast furnace as set forth in claim 1, wherein the tuyere comprises a small tuyere and a blowpipe, a blowpipe is arranged inside the small tuyere and on the inner peripheral side of the blowpipe, spaced apart from the small tuyere, the outer flow hole is arranged between the small tuyere and the blowpipe and the blowpipe, and the inner flow hole is arranged inside the blowpipe.

3. Tuyere equipment for a blast furnace according to claim 2, wherein the joint between the small tuyere and the blowpipe has a sliding joint structure.

4. A blast furnace tuyere facility according to any one of claims 1 to 3, wherein in the inner flow hole, at least one of the two or more independent flow paths has a narrowing shape toward the downstream side.

5. Tuyere equipment for a blast furnace as set forth in claim 2 or 3, or claim 4 dependent on claim 2 or 3, wherein the clearance between the small tuyere and the blowing pipe is 20% or more of the inner diameter of the small tuyere.

6. A blast furnace tuyere installation according to claim 2, 3 or 5, or claim 4 depending on claim 2 or 3, wherein the blowing pipe has a water cooling mechanism.

7. A blast furnace tuyere installation according to claim 2, 3, 5 or 6, or claim 4 depending on claim 2 or 3, wherein the blowing pipe is connected to the blowpipe at its rear end.

8. A blast furnace tuyere facility according to claim 2, 3, 5, 6 or 7, or claim 4 dependent on claim 2 or 3, which is provided with a mixing promotion structure having a conducting section at the outlet of the blowing pipe that connects at least two of the two or more independent flow paths.

9. A method for operating a blast furnace using blast furnace tuyere equipment as defined in any one of claims 1 to 8, characterized in that a low-oxygen concentration gas, a high-oxygen concentration gas having an oxygen concentration higher than that of the low-oxygen concentration gas, and a reducing agent are injected into the blast furnace from the tuyere, the low-oxygen concentration gas is injected from the outer flow hole, the high-oxygen concentration gas and the reducing agent are injected from the inner flow hole, and the high-oxygen concentration gas and the reducing agent are injected separately from the two or more independent flow paths.

10. A method for operating a blast furnace according to claim 9, wherein the gas flow velocity of the high-oxygen-concentration gas is 180 m / s or more downstream of the tuyere and 60 m / s or less upstream of the tuyere.

11. The method of operating a blast furnace according to claim 9 or 10, wherein the reducing material comprises at least one of blast furnace gas, coke oven gas, ammonia, carbon monoxide, hydrogen, methane, ethane, ethylene, acetylene, propane, propylene, propyne, butane, butene, butyne, methanol, ethanol, and dimethyl ether.

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