Blast furnace, method for operating blast furnace, and method for manufacturing hot air tuyere

Abstract

Disclosed is a novel feature capable of increasing the combustion rate of a solid reducing agent if the solid reducing agent is supplied together with a reducing gas into a blast furnace through a hot air tuyere. In a blast furnace according to the present disclosure, a hot air tuyere comprises a tuyere body, a hot air flow path, a reducing gas blowout port, and a solid reducing agent blowout port. The hot air flow path is defined by an inner wall of the tuyere body, the reducing gas blowout port faces the hot air flow path, and the solid reducing agent blowout port faces the hot air flow path. A reducing gas blown out from the reducing gas blowout port contains a hydrogen-based reducing gas, and a solid reducing agent blown out from the solid reducing agent blowout port contains carbon. The length L1 between a tip end of the tuyere body and the center of the reducing gas blowout port is shorter than the length L2 between the tip end of the tuyere body and the center of the solid reducing agent blowout port, and the length L1 between the tip end of the tuyere body and the center of the reducing gas blowout port is from 50 to 120 mm.

Description

Blast furnace, method of operating a blast furnace, and method of manufacturing a hot blast tuyere

[0001] This application discloses a blast furnace, a method for operating a blast furnace, and a method for manufacturing hot blast tuyere nozzles.

[0002] CO in the steelmaking process ２ Reducing emissions has been studied. For example, when producing pig iron in a blast furnace, a reducing gas such as hydrogen gas may be used in place of a portion of the reducing material, such as coke. As a method for supplying reducing gas to a blast furnace, Patent Document 1 discloses a method in which a lance for injecting reducing gas is disposed in the hot blast flow path or wall surface of a hot blast tuyere, and reducing gas is injected through the lance. Although not intended to inject reducing gas, Patent Document 2 discloses a method in which a fuel injection lance is inserted into the wall surface of a hot blast tuyere, and pulverized coal as fuel is injected into the blast furnace through the fuel injection lance.

[0003] Patent No. 4997734 Patent No. 5840202

[0004] In the prior art, when a solid reducing material is supplied together with a reducing gas into the inside of a blast furnace through a hot blast tuyere, there is room for improvement in terms of increasing the combustion rate of the solid reducing material.

[0005] The present application discloses the following multiple aspects as means for solving the above problems. <Aspect 1> A blast furnace having a hot blast tuyere, the hot blast tuyere having a tuyere body, a hot blast passage, a reducing gas outlet, and a solid reducing material outlet, the hot blast passage is defined by an inner wall of the tuyere body, the reducing gas outlet faces the hot blast passage, the solid reducing material outlet faces the hot blast passage, the reducing gas blown out from the reducing gas outlet contains a hydrogen-based reducing gas, the solid reducing material blown out from the solid reducing material outlet contains carbon, and a length L between a tip of the tuyere body and a center of the reducing gas outlet is １ The length L between the tip of the tuyere body and the center of the solid reducing material outlet ２ The length L between the tip of the tuyere body and the center of the reducing gas outlet is shorter than １The blast furnace of aspect 1, wherein the length L between the tip of the tuyere body and the center of the reducing gas outlet is 50 mm or more and 120 mm or less. １ is 50 mm or more and 75 mm or less. <Aspect 3> The blast furnace of Aspect 1 or 2, wherein the reducing gas outlet is provided on the inner wall of the tuyere body. <Aspect 4> The blast furnace of Aspect 1 or 2, wherein the reducing gas outlet is arranged inside the hot blast flow path. <Aspect 5> The blast furnace of any of Aspects 1 to 4, wherein the solid reducing material outlet is provided on the inner wall of the tuyere body. <Aspect 6> The blast furnace of any of Aspects 1 to 4, wherein the solid reducing material outlet is arranged inside the hot blast flow path. <Aspect 7> A method for operating a blast furnace, comprising: supplying hot air into the inside of the blast furnace through a hot air flow path of a tuyere body of a hot air tuyere; and supplying a reducing gas containing a hydrogen-based reducing gas and a solid reducing material containing carbon to the hot air flow path through a reducing gas outlet facing the hot air flow path and a solid reducing material outlet facing the hot air flow path; １ The length L between the tip of the tuyere body and the center of the solid reducing material outlet ２ The length L between the tip of the tuyere body and the center of the reducing gas outlet is shorter than １ The method for operating a blast furnace according to aspect 7, wherein the length L between the tip of the tuyere body and the center of the reducing gas outlet is 50 mm or more and 120 mm or less. １is 50 mm or more and 75 mm or less. <Aspect 9> The method of operating a blast furnace according to aspect 7 or 8, comprising supplying the reducing gas from the reducing gas outlet provided in the inner wall of the tuyere body to the hot blast passage. <Aspect 10> The method of operating a blast furnace according to aspect 7 or 8, comprising supplying the reducing gas from the reducing gas outlet arranged inside the hot blast passage to the hot blast passage. <Aspect 11> The method of operating a blast furnace according to any of aspects 7 to 10, comprising supplying the reducing gas from the solid reducing material outlet provided in the inner wall of the tuyere body to the hot blast passage. <Aspect 12> The method of operating a blast furnace according to any of aspects 7 to 10, comprising supplying the reducing gas from the solid reducing material outlet arranged inside the hot blast passage to the hot blast passage. <Aspect 13> A method for manufacturing a hot air tuyere, the hot air tuyere having: a tuyere body; a hot air flow path; a reducing gas outlet; and a solid reducing material outlet, the hot air flow path being defined by an inner wall of the tuyere body, the reducing gas outlet facing the hot air flow path, the solid reducing material outlet facing the hot air flow path, the reducing gas blown out from the reducing gas outlet containing a hydrogen-based reducing gas, and the solid reducing material blown out from the solid reducing material outlet containing carbon, the manufacturing method comprising: determining a hydrogen combustion rate Z (%) in the hot air tuyere, a length L between a tip of the tuyere body and a center of the reducing gas outlet, and a solid reducing material blown out from the solid reducing material outlet. １ , and the length L between the tip of the tuyere body and the center of the solid reducing material outlet ２ and determining the length L of the hot blast tuyere based on the target hydrogen combustion rate Z (%) and the relational expression (1). １ and the length L ２and determining the actual dimensions of one or both of the above. <Aspect 14> The method for manufacturing a hot-blast tuyere according to Aspect 13, wherein the hydrogen combustion rate Z (%) is determined based on a predetermined relational expression (2) between the tuyere pressure drop change ΔP (kPa) and the hydrogen combustion rate Z (%), and a target tuyere pressure drop change ΔP (kPa).

[0006] According to the technology of the present disclosure, when a solid reducing material is supplied together with a reducing gas into the inside of a blast furnace through a hot blast tuyere, the combustion rate of the solid reducing material can be increased.

[0007] 1 shows a schematic diagram of an example of the configuration of a blast furnace. Some components of the blast furnace are omitted. 1 shows a schematic diagram of an example of the configuration of a tuyere body, hot blast flow path, reducing gas outlet, and solid reducing material outlet of a hot blast tuyere ... relationship between the length between the tip of the tuyere body and the center of the reducing gas outlet and the solid reducing material combustion rate (pulverized coal combustion rate). 1 shows a relationship between the length between the tip of the tuyere body and the center of the reducing gas outlet and the solid reducing material combustion rate (pulverized coal combustion rate). 1 shows a relationship between the length between the center of the solid reducing material outlet and the center of the reducing gas outlet and the reducing gas combustion rate (hydrogen combustion rate) at the hot blast tuyere. 1 shows a relationship between the change in pressure drop in the tuyere and the hydrogen combustion rate at the hot blast tuyere with respect to pulverized coal injection operation.

[0008] Hereinafter, an embodiment of the blast furnace, the blast furnace operation method, and the hot-air tuyere manufacturing method of the present disclosure will be described. However, the blast furnace, the blast furnace operation method, and the hot-air tuyere manufacturing method of the present disclosure are not limited to the following embodiment.

[0009] 1. Blast Furnace As shown in FIG. 1, a blast furnace 100 according to one embodiment has a hot blast tuyere 10. As shown in FIGS. 2A to 2C, the hot blast tuyere 10 has a tuyere body 11, a hot blast passage 12, a reducing gas outlet 13x, and a solid reducing material outlet 14x. The hot blast tuyere 10 is defined by the inner wall of the tuyere body 11. The reducing gas outlet 13x faces the hot blast passage 12. The solid reducing material outlet 14x faces the hot blast passage 12. The reducing gas blown out from the reducing gas outlet 13x contains a hydrogen-based reducing gas. The solid reducing material blown out from the solid reducing material outlet 14x contains carbon. A length L between a tip 11x of the tuyere body 11 and the center of the reducing gas outlet 13x is １ is the length L between the tip 11x of the tuyere body 11 and the center of the solid reducing material outlet 14x ２ The length L between the tip 11x of the tuyere body 11 and the center of the reducing gas outlet 13x is shorter than １ is 50 mm or more and 120 mm or less.

[0010] 1.1 Hot Blast Tuyere As shown in FIG. 1 , the hot blast tuyere 10 is provided, for example, below the shaft lower end 101ax of the blast furnace 100 and above the tap hole 102. The "shaft lower end" refers to the boundary between the shaft 101a and the belly 101b. The "shaft" refers to the portion above the belly 101b, where the furnace diameter typically increases from top to bottom. The "belly" refers to the portion below the shaft and above the bosch 101c, where the furnace diameter typically is greatest. The furnace diameter (diameter) of the belly 101b may be, for example, 5 m or more and 20 m or less, or 10 m or more and 18 m or less. The "tap hole" refers to a molten iron tap port provided at the bottom of the blast furnace 100. The "hot blast tuyere" refers to a nozzle for supplying hot air to the blast furnace. The blast furnace 100 may have a hot air tuyere 10 below the belly lower end 101bx and above the tap hole 102, or may have a hot air tuyere 10 below the morning glory lower end 101cx and above the tap hole 102.

[0011] The number of hot air tuyere 10 provided in the blast furnace 100 is not particularly limited and can be determined according to the internal volume of the blast furnace. The blast furnace 100 may have a plurality of hot air tuyere 10 arranged in the circumferential direction of the blast furnace 100. In other words, the blast furnace 100 may have a plurality of hot air tuyere 10 arranged in the circumferential direction when viewed from above. Usually, the height positions of the centers of the plurality of hot air tuyere 10 are the same.

[0012] 1.1.1 Tuyere Body and Hot Air Flow Channel The hot air tuyere 10 has a hollow tuyere body 11. The hot air flow channel 12 is defined by an inner wall 11a of the tuyere body 11. The upstream side of the hot air flow channel 12 (the side opposite the tip 11x of the tuyere body 11) of the tuyere body 11 is connected to a blowpipe (not shown), and the downstream side of the hot air flow channel 12 (the side of the tip 11x of the tuyere body 11) faces the inside of the blast furnace 100. The tuyere body 11 has an opening 12x facing the interior of the blast furnace 100, and the opening 12x serves as the outlet of the hot air flow channel 12. The tuyere body 11 can be connected to a hot air stove outside the blast furnace 100 via a hot air pipe, a blowpipe, or the like. In other words, the blast furnace 100 can be configured so that hot air is supplied from the hot air stove to the inside of the blast furnace 100 via the hot air pipe, the blowpipe, and the tuyere body 11. The opening diameter of the outlet of the hot air flow path 12 of the tuyere body 11 (the circle equivalent diameter of the opening 12x facing the inside of the blast furnace 100, the nozzle diameter) may be, for example, 20 mm or more and 400 mm or less, or 40 mm or more and 300 mm or less.

[0013] The wall of the tuyere body 11 has, for example, an inner wall 11a that defines the hot air flow path 12, an outer wall 11b facing the inside of the blast furnace 100, and a tip 11x. The tuyere body 11 may have a cooling water flow path inside the wall. This makes it possible to cool the tuyere body 11 and its surroundings during operation of the blast furnace 100 and suppress thermal damage, etc. The shape of the cooling water flow path is not particularly limited. The tuyere body 11 is made of a known material, for example, copper.

[0014] 1.1.2 Reducing Gas Outlet The hot air tuyere 10 has a reducing gas outlet 13x, and a reducing gas containing a hydrogen-based reducing gas is supplied from the reducing gas outlet 13x to the hot air flow passage 12. More specifically, as shown in FIG. 1 , the blast furnace 100 may be configured so that the reducing gas supplied from a reducing gas supply source 20 via a pipe 21 to the hot air tuyere 10 passes through a reducing gas flow passage 13 provided in the hot air tuyere 10 and is blown from the reducing gas outlet 13x into the hot air flow passage 12. In other words, the blast furnace 100 may be provided with a reducing gas injection device, and the reducing gas injection device may include a reducing gas supply source 20, a pipe 21 connected to the reducing gas supply source 20, a hot air tuyere 10 connected to the pipe 21, a reducing gas flow passage 13 provided in the hot air tuyere 10, and a reducing gas outlet 13x provided at the downstream tip of the reducing gas flow passage 13. Alternatively, the technology of the present disclosure can be said to be a blast furnace system including a blast furnace 100 and a reducing gas supply source 20. That is, as shown in Fig. 1 , a blast furnace system according to one embodiment may include a blast furnace 100, a reducing gas supply source 20, and a pipe 21 connecting a hot air tuyere 10 of the blast furnace 100 and the reducing gas supply source 20.

[0015] 2A to 2C, the reducing gas outlet 13x faces the hot air flow passage 12. That is, the blast furnace 100 is configured so that reducing gas is supplied to the hot air flow passage 12 via the reducing gas outlet 13x. When the reducing gas outlet 13x faces the hot air flow passage 12, the concentration distribution of the reducing gas inside the blast furnace 100 can be made more uniform than when the reducing gas outlet 13x is provided at the tip 11x of the tuyere body 11.

[0016] The reducing gas outlet 13x may be provided on the inner wall 11a of the tuyere body 11 as shown in Figures 2A and 2B, or may be arranged inside the hot blast channel 12 as shown in Figure 2C. In particular, when the reducing gas outlet 13x is provided on the inner wall 11a of the tuyere body 11, better effects can be expected in terms of uniforming the reducing gas concentration in the blast furnace 100 and improving the combustion rate of the solid reducing material. On the other hand, when the reducing gas outlet 13x is arranged inside the hot blast channel 12, the position of the reducing gas outlet 13x can be easily changed as desired. Therefore, for example, it is possible to change the position of the reducing gas outlet 13x as the operation changes. ２ -L １ Even if the optimum point of L changes, it is possible to change the L without replacing the hot air tuyere 10. ２ -L １ It is expected to have the effect of being able to adjust the

[0017] 2A to 2C, the reducing gas outlet 13x is provided closer to the tip 11x of the tuyere body 11 than the solid reducing material outlet 14x (described later). Specifically, the length L between the tip 11x of the tuyere body 11 and the center (centroid) of the reducing gas outlet 13x １ is the length L between the tip 11x of the tuyere body 11 and the center (centroid) of the solid reducing material outlet 14x. ２ The length L １ is the length L ２ By making the length L shorter than , the combustion rate of the solid reducing material, which will be described later, can be increased. This makes it possible to utilize the combustion heat of the solid reducing material and operate the blast furnace with high efficiency. ２ and the length L １ Difference L ２ -L １ may be, for example, greater than 0 mm and equal to or less than 150 mm, or equal to or greater than 50 mm and equal to or less than 100 mm.

[0018] In addition, "the length L between the tip 11x of the tuyere body 11 and the center of the reducing gas outlet 13x" １ " and "The length L between the tip 11x of the tuyere body 11 and the center of the solid reducing material outlet 14x ２" is measured as follows. First, "the tip 11x of the tuyere body 11" refers to the tip of the tuyere body 11 that protrudes furthest toward the inside of the blast furnace 100. A vertical plane X including the tip is assumed. Also, a vertical plane Y including the center of the reducing gas outlet 13x and parallel to the vertical plane X is assumed. Also, a vertical plane Z including the center of the solid reducing material outlet 14x and parallel to the vertical plane X is assumed. Here, the shortest length (distance) L between the vertical plane X and the vertical plane Y is ＸＹ is a value between 0 and L depending on the horizontal direction of the vertical plane X and the vertical plane Y. １ That is, the length L between the tip 11x of the tuyere body 11 and the center of the reducing gas outlet 13x is １ " is the shortest length (distance) L between the vertical plane X and the vertical plane Y. ＸＹ Similarly, "the length L between the tip 11x of the tuyere body 11 and the center of the solid reducing material outlet 14x" means the maximum value of ２ " is the shortest length (distance) L between the vertical plane X and the vertical plane Z. ＸＺ means the maximum value of

[0019] 2A to 2C, the reducing gas outlet 13x is provided outside the furnace with respect to the tip 11x of the tuyere body 11. In this embodiment, the length L between the tip 11x of the tuyere body 11 and the center of the reducing gas outlet 13x is １ It is important that the length L is 50 mm or more and 120 mm or less. １ It has been found that the combustion rate of the solid reducing material is high when the length L is in the vicinity of 75 mm. １ is 75 mm±45 mm, that is, 30 mm or more and 120 mm or less, the combustion rate of the solid reducing material is high. On the other hand, taking into consideration that the closer the reducing gas outlet 13x is to the tip 11x of the tuyere body 11, there is a concern that the reducing gas injection means may be thermally damaged, and that there are structural restrictions in the vicinity of the tip 11x of the tuyere body 11 (for example, if a reducing gas injection passage is provided in the vicinity of the tip 11x of the tuyere body 11, it may be impossible to appropriately form a water-cooling structure for the tuyere body 11), the length L １It is difficult to make the length L less than 50 mm. １ By setting the length L to be 50 mm or more and 120 mm or less, the reducing gas injection passage and the reducing gas outlet 13x can be appropriately formed in the tuyere body 11, and the combustion rate of the solid reducing material can be increased during blast furnace operation. This makes it possible to utilize the combustion heat of the solid reducing material and operate the blast furnace with high efficiency. １ may be 55 mm or more, 60 mm or more, 65 mm or more, 70 mm or more, 75 mm or more, 80 mm or more, 85 mm or more, 90 mm or more, 95 mm or more, 100 mm or more, 105 mm or more, 110 mm or more, or 115 mm or more, or may be 115 mm or less, 110 mm or less, 105 mm or less, 100 mm or less, 95 mm or less, 90 mm or less, 85 mm or less, 80 mm or less, 75 mm or less, 70 mm or less, 65 mm or less, 60 mm or less, or 55 mm or less. １ When the distance is 60 mm or more and 100 mm or less, and particularly 70 mm or more and 90 mm or less, the combustion rate of the solid reducing material is more likely to be improved.

[0020] On the other hand, the present inventor has conducted extensive research and found that the hydrogen combustion rate Z (%) in the hot blast tuyere and the length L １ (mm) and the above length L ２ It has been found that the relationship between the length L between the tip 11x of the tuyere body 11 and the center of the reducing gas outlet 13x and the change in tuyere pressure drop ΔP (kPa) and the hydrogen combustion rate Z (%) can be expressed by the following formula (1): １ The shorter the length L, the lower the combustion rate of the hydrogen-based reducing gas in the hot blast tuyere 10, and the more the pressure loss in the hot blast tuyere 10 can be reduced. １ may be, for example, 50 mm or more and 100 mm or less, 50 mm or more and 95 mm or less, 50 mm or more and 90 mm or less, 50 mm or more and 85 mm or less, 50 mm or more and 80 mm or less, or 50 mm or more and 75 mm or less. Z=0.0016×L １ -0.016 x L ２+0.2282 (1) ΔP=177.51Z-18.337 (2)

[0021] The above length L １ However, when the distance is 60 mm or more and 100 mm or less, 60 mm or more and 95 mm or less, 60 mm or more and 90 mm or less, 60 mm or more and 85 mm or less, 60 mm or more and 80 mm or less, 60 mm or more and 75 mm or less, 70 mm or more and 100 mm or less, 70 mm or more and 95 mm or less, 70 mm or more and 90 mm or less, 70 mm or more and 85 mm or less, 70 mm or more and 80 mm or less, or 70 mm or more and 75 mm or less, the combustion rate of the solid reducing material can be more significantly increased while reducing the pressure loss in the hot air tuyere 10.

[0022] 1.1.2.2 Configuration of the Reducing Gas Flow Passage The reducing gas outlet 13x is an outlet provided downstream of the reducing gas flow passage 13. In the blast furnace 100, the reducing gas flow passage 13 may be provided, for example, as a reducing gas injection port or a reducing gas injection lance. In the present application, the term "port" refers to a gas flow passage provided so as to penetrate the wall of the tuyere body 11, and the term "lance" refers to a gas passage having an outlet in the hot air flow passage 12 without penetrating the wall of the tuyere body 11.

[0023] 2A and 2B , the reducing gas injection port serving as the reducing gas flow path 13 is provided to penetrate the wall of the tuyere body 11. For example, the reducing gas injection port has a reducing gas flow path 13 inside the wall of the tuyere body 11 and has a reducing gas outlet 13x downstream of the flow path. The length, longitudinal shape, opening shape, etc. of the reducing gas injection port can be determined appropriately taking into account the wall thickness of the tuyere body 11 and the water-cooling structure inside the wall. As described above, the reducing gas injection port serving as the reducing gas flow path 13 can be connected to the reducing gas supply source 20 via the piping 21, etc. In other words, the blast furnace 100 can be configured such that, for example, reducing gas supplied from the reducing gas supply source 20 via the piping 21 to the reducing gas injection port is supplied into the interior of the blast furnace 100 via the reducing gas injection port and the hot air flow path 12. There are no particular limitations on the shapes of the reducing gas supply source 20 and the piping 21 outside the blast furnace 100.

[0024] 2C , the reducing gas injection lance serving as the reducing gas flow path 13 does not penetrate the wall of the tuyere body 11, and its tip is disposed in the hot air flow path 12. The length, longitudinal shape, opening shape, and the like of the reducing gas injection lance can be determined appropriately in consideration of the shape of the hot air flow path 12. Like the reducing gas injection port, the reducing gas injection lance can be connected to the reducing gas supply source 20 via a pipe 21 or the like. In other words, the blast furnace 100 can be configured such that, for example, reducing gas supplied from the reducing gas supply source 20 via the pipe 21 to the reducing gas injection lance is supplied into the interior of the blast furnace 100 via the reducing gas injection lance and the hot air flow path 12. There are no particular limitations on the shapes of the reducing gas supply source 20 and the pipe 21 outside the blast furnace 100.

[0025] In the blast furnace 100, the hot blast tuyere 10 may have a plurality of reducing gas flow passages 13. For example, a plurality of reducing gas injection ports may be employed as the reducing gas flow passages 13, a plurality of reducing gas injection lances may be employed, or both at least one reducing gas injection port and at least one reducing gas injection lance may be employed. In this case, the reducing gas supply source connected to one reducing gas flow passage 13 and the reducing gas supply sources connected to the other reducing gas flow passages 13 may be the same as or different from each other. That is, reducing gas may be supplied from one reducing gas supply source to the plurality of reducing gas flow passages 13 via branch flow passages, or reducing gas may be supplied from one reducing gas supply source to one reducing gas flow passage 13 and then supplied from another reducing gas supply source to the other reducing gas flow passages 13.

[0026] 1.1.2.3 Other Matters The diameter (area-equivalent diameter of a circle) of the reducing gas outlet 13x is not particularly limited. There is an upper limit to the flow rate of the reducing gas supplied to the blast furnace 100 through the reducing gas outlet 13x. If the diameter of the reducing gas outlet 13x is too large or too small, it may be difficult to control the flow rate of the reducing gas blown out from the reducing gas outlet 13x. Therefore, it is preferable that the diameter of the reducing gas outlet 13x be within a predetermined range. From this perspective, the diameter may be, for example, 10 mm or more and 50 mm or less, or 20 mm or more and 30 mm or less. Alternatively, the diameter of the reducing gas outlet 13x may be 10% or more and 50% or less, or 15% or more and 30% or less, of the diameter (area-equivalent diameter of a circle) of the opening 12x serving as the outlet of the hot air channel 12. When the reducing gas outlet 13x has such a diameter, the flow rate of the reducing gas is more easily controlled.

[0027] The number of reducing gas outlets 13x provided in the hot air tuyere 10 is not particularly limited. The number of reducing gas outlets 13x provided in the hot air tuyere 10 may be one or more. When the number is one, the contact surface area between the reducing gas and the hot air is small, reducing pressure loss inside the tuyere, and therefore, it is expected that fluctuations in the flow rate of the reducing gas in response to pressure fluctuations due to operational fluctuations can be reduced. When the number is multiple, it is expected that even if one outlet becomes unusable, operation can be continued by redirecting the flow rate to another outlet.

[0028] The height position of the reducing gas outlet 13x provided in the hot air tuyere 10 is not particularly limited. The height position of the center of the reducing gas outlet 13x may be higher, lower, or the same height as the height position of the center of the opening 12x serving as the outlet of the hot air flow channel 12. In particular, when the height position of the reducing gas outlet 13x is located at a position above the height position of the center of the opening 12x serving as the outlet of the hot air flow channel 12, the combustion rate of the solid reducing material is likely to be further increased. Furthermore, when the height position of the reducing gas outlet 13x is located at a position above the height position of the solid reducing material outlet 14x described below, the combustion rate of the solid reducing material is likely to be further increased, and the concentration distribution of the reducing components inside the blast furnace 100 is likely to be in a good state.

[0029] 1.1.3 Solid Reducing Material Outlet The hot air tuyere 10 has a solid reducing material outlet 14x, and a solid reducing material containing carbon is supplied from the solid reducing material outlet 14x to the hot air passage 12. More specifically, as shown in FIG. 1 , the blast furnace 100 may be configured so that the solid reducing material supplied from a solid reducing material supply source 30 via a pipe 31 to the hot air tuyere 10 passes through a solid reducing material passage 14 provided in the hot air tuyere 10 and is blown from the solid reducing material outlet 14x into the hot air passage 12. In other words, the blast furnace 100 may be provided with a solid reducing material injection device, and the solid reducing material injection device may include a solid reducing material supply source 30, a pipe 31 connected to the solid reducing material supply source 30, a hot air tuyere 10 connected to the pipe 31, a solid reducing material passage 14 provided in the hot air tuyere 10, and a reducing gas outlet 14x provided at the downstream end of the solid reducing material passage 14. Alternatively, the technology of the present disclosure can be said to be a blast furnace system including a blast furnace 100 and a solid reducing material supply source 30. That is, as shown in Fig. 1 , a blast furnace system according to one embodiment may include a blast furnace 100, a solid reducing material supply source 30, and a pipe 31 connecting a hot air tuyere 10 of the blast furnace 100 and the solid reducing material supply source 30.

[0030] 1.1.3.1 Position of the Solid Reducing Material Outlet As shown in Figures 2A to 2C, the solid reducing material outlet 14x faces the hot blast flow path 12. That is, the blast furnace 100 is configured so that the solid reducing material is supplied to the hot blast flow path 12 via the solid reducing material outlet 14x. When the solid reducing material outlet 14x faces the hot blast flow path 12, the combustion rate of the solid reducing material can be increased compared to when the solid reducing material outlet 14x is provided at the tip 11x of the tuyere body 11. The relative positional relationship of the solid reducing material outlet 14x with respect to the tip 11x of the tuyere body 11 and the reducing gas outlet 13x is as described above.

[0031] The solid reducing material outlet 14x may be disposed inside the hot air flow path 12 as shown in Figures 2A and 2C, or may be provided on the inner wall 11a of the tuyere body 11 as shown in Figure 2B. When the solid reducing material outlet 14x is disposed inside the hot air flow path 12, the hot air and the solid reducing material are actively mixed, promoting a temperature rise of the solid reducing material, which is expected to have the effect of increasing the combustion rate. When the solid reducing material outlet 14x is provided on the inner wall 11a of the tuyere body 11, it is expected to have the effect of improving visibility from the rear end of the tuyere, making equipment management easier.

[0032] 1.1.3.2 Configuration of Solid Reducing Material Supply Path The solid reducing material outlet 14x is an outlet provided downstream of the solid reducing material supply path 14. In the blast furnace 100, the solid reducing material supply path 14 may be provided as a solid reducing material injection port or a solid reducing material injection lance. The definitions of "port" and "lance" are as described above.

[0033] 2A and 2C , the solid reducing material injection lance serving as the solid reducing material supply passage 14 has its tip disposed in the hot blast passage 12 without penetrating the wall of the tuyere body 11. The length, longitudinal shape, opening shape, and the like of the solid reducing material injection lance can be determined appropriately in consideration of the shape of the hot blast passage 12. As described above, the solid reducing material injection lance serving as the solid reducing material supply passage 14 can be connected to the solid reducing material supply source 30 via the piping 31 or the like. In other words, the blast furnace 100 can be configured such that the solid reducing material is supplied from the solid reducing material supply source 30 to the hot blast passage 12 via the piping 31 and the solid reducing material injection lance, for example. At least a portion of the solid reducing material supplied to the hot blast passage 12 is combusted inside the hot blast passage 12, and the remainder is supplied into the blast furnace 100. There are no particular limitations on the shapes of the solid reducing material supply source 30 and the piping 31.

[0034] As shown in FIG. 2B , the solid reducing material injection port serving as the solid reducing material supply path 14 is provided to penetrate the wall of the tuyere body 11. For example, the solid reducing material injection port has a supply path 14 inside the wall of the tuyere body 11, and a solid reducing material outlet 14x downstream of the supply path. The length, longitudinal shape, opening shape, etc. of the solid reducing material injection port can be appropriately determined taking into account the wall thickness of the tuyere body 11 and the water-cooling structure inside the wall. As described above, the solid reducing material injection port serving as the solid reducing material supply path 14 can be connected to the solid reducing material supply source 30 via a pipe 31 or the like. In other words, the blast furnace 100 can be configured such that the solid reducing material is supplied from the solid reducing material supply source 30 to the hot blast flow path 12 via the pipe 31 and the solid reducing material injection port, for example. At least a portion of the solid reducing material supplied to the hot blast flow path 12 is combusted inside the hot blast flow path 12, and the remainder is supplied into the blast furnace 100. There is no particular limitation on the form of the solid reducing material supply source 30 or the pipe 31.

[0035] In the blast furnace 100, the hot blast tuyere 10 may have a plurality of solid reducing material supply paths 14. For example, a plurality of solid reducing material injection ports may be employed as the solid reducing material supply paths 14, a plurality of solid reducing material injection lances may be employed, or both at least one solid reducing material injection port and at least one solid reducing material injection lance may be employed. In this case, the solid reducing material supply source connected to one solid reducing material supply path 14 and the solid reducing material supply sources connected to the other solid reducing material supply paths 14 may be the same as or different from each other. That is, the solid reducing material may be supplied from one solid reducing material supply source to the plurality of solid reducing material supply paths 14 via branch paths, or the solid reducing material may be supplied from one solid reducing material supply source to one solid reducing material supply path 14, and the solid reducing material may be supplied from another solid reducing material supply source to the other solid reducing material supply paths 14.

[0036] 1.1.2.3 Other Matters The diameter (area-equivalent circle diameter) of the solid reducing material outlet 14x is not particularly limited. Considering pressure loss constraints, it is difficult to reduce the diameter. Furthermore, reducing the diameter too much can result in excessively high flow velocity, which can lead to problems such as severe wear on the transport piping. Meanwhile, a high flow velocity is required at the solid reducing material outlet 14x to prevent flashback. If the diameter is excessively large, increasing the flow velocity tends to increase the variability in the amount of solid reducing material injected. To stably inject the solid reducing material, it is preferable to set the diameter within a predetermined range. From this perspective, the diameter may be, for example, 10 mm to 50 mm, or 20 mm to 30 mm. Alternatively, the diameter of the solid reducing material outlet 14x may be 10% to 50% or 15% to 30% of the diameter (area-equivalent circle diameter) of the opening 12x serving as the outlet of the hot air flow channel 12. When the solid reducing material blow-out port 14x has such a diameter, the solid reducing material can be blown in more stably.

[0037] There is no particular limitation on the number of solid reducing material outlets 14x provided in the hot air tuyere 10. The number of solid reducing material outlets 14x provided in the hot air tuyere 10 may be one or more.

[0038] There are no particular limitations on the height position of the solid reducing material outlet 14x provided in the hot air tuyere 10. The height position of the center of the solid reducing material outlet 14x may be higher or lower than the height position of the center of the opening 12x serving as the outlet of the hot air flow channel 12, or may be the same height position.

[0039] 1.2 Hot Air The hot air supplied from the hot air tuyere 10 into the blast furnace 100 may be, for example, air or oxygen-enriched air. The temperature of the hot air is, for example, 1000°C or higher. The temperature of the hot air may be 1000°C or higher and 2000°C or lower, 1000°C or higher and 1700°C or lower, 1000°C or higher and 1500°C or lower, or 1000°C or higher and 1300°C or lower. The flow velocity of the hot air at the opening 12x serving as the outlet of the hot air channel 12 may be appropriately adjusted depending on the operating conditions of the blast furnace 100, and may be, for example, 100 m / s or higher and 300 m / s or lower, or 200 m / s or higher and 250 m / s or lower.

[0040] 1.3 Reducing Gas The reducing gas is a gas that functions as a reducing agent inside the blast furnace 100. In other words, even if a gas does not function as a reducing agent before being supplied to the blast furnace 100, as long as it can generate a reducing agent (reducing component) inside the blast furnace 100 by thermal decomposition or the like, it is considered to be included in the "reducing gas" referred to in the present application. In this embodiment, the reducing gas includes at least a hydrogen-based reducing gas. The "hydrogen-based reducing gas" refers to one or both of hydrogen elemental gas and a compound that generates hydrogen gas by a decomposition reaction (e.g., a thermal decomposition reaction). In other words, the hydrogen-based reducing gas may be hydrogen gas itself, a gas of a compound that generates hydrogen by a decomposition reaction, or a mixture thereof. Examples of compounds that generate hydrogen by a decomposition reaction include hydrocarbons such as methane, alcohols such as methanol and ethanol, and ammonia. In one embodiment, the hydrogen-based reducing gas may be one or more selected from hydrogen gas, hydrocarbon gas, alcohol gas, and ammonia gas. In particular, a greater effect can be expected when the reducing gas includes hydrogen gas as a hydrogen-based reducing gas. The proportion of the hydrogen-based reducing gas in the reducing gas may be, for example, 30% by volume or more and 100% by volume or less, 40% by volume or more and 100% by volume or less, 50% by volume or more and 100% by volume or less, 60% by volume or more and 100% by volume or less, 70% by volume or more and 100% by volume or less, 80% by volume or more and 100% by volume or less, or 90% by volume or more and 100% by volume or less. When the reducing gas contains hydrogen gas, the proportion of the hydrogen gas in the reducing gas may be, for example, 30% by volume or more and 100% by volume or less, 40% by volume or more and 100% by volume or less, 50% by volume or more and 100% by volume or less, 60% by volume or more and 100% by volume or less, 70% by volume or more and 100% by volume or less, 80% by volume or more and 100% by volume or less, or 90% by volume or more and 100% by volume or less. The reducing gas may contain a reducing gas other than the hydrogen-based reducing gas. Examples of reducing gases other than the hydrogen-based reducing gas include carbon monoxide gas. In this embodiment, other gases may be blown in together with the reducing gas from the reducing gas outlet 13x. Examples of other gases besides the reducing gas include inert gases (nitrogen, etc.).In this embodiment, the reducing gas may be at least one selected from coke oven gas (COG), converter gas (LDG), blast furnace gas (BFG), natural gas (NG), and synthesis gas (Syngas). One reducing gas may be used alone, or two or more reducing gases may be used in combination. The temperature of the reducing gas supplied from the reducing gas outlet 13x to the hot air channel 12 may be, for example, 0°C or higher and 2000°C or lower, or 25°C or higher and 1500°C or lower. In this embodiment, the flow velocity of the reducing gas at the reducing gas outlet 13x may be, for example, equal to or lower than the sonic velocity at the operating temperature of each reducing gas. Other gases may be supplied from the reducing gas outlet 13x together with the reducing gas. Examples of other gases include inert gases such as nitrogen gas.

[0041] 1.4 Solid Reducing Material The solid reducing material may be any known solid reducing material used in the technical field of blast furnaces. As described above, the technology of the present disclosure improves the combustion rate of the solid reducing material, and is premised on the fact that the solid reducing material contains carbon, which is a combustible component. The proportion of carbon in the solid reducing material is not particularly limited, and may be 50% by mass or more and 100% by mass or less, or 75% by mass or more and 100% by mass or less. The solid reducing material may be, for example, pulverized coal, coke, or char obtained by carbonization of biomass or lignite. Examples of biomass that can be used include agricultural biomass (straw, sugarcane, rice bran, vegetation, coconut kernels, etc.), forestry biomass (papermaking waste, sawmill waste, thinned wood, firewood, etc.), livestock biomass (livestock waste), fisheries biomass (fishery processing residue), and waste biomass (food waste, RDF (Refuse Derived Fuel), garden trees, construction waste, sewage sludge). There are no particular limitations on the origin of lignite. Char is a carbonaceous substance that is generated when carbonaceous material is heated without achieving a softened or molten state (see JIS 0104, Terminology of Coal Utilization Technology). One type of solid reducing agent may be used alone, or two or more types may be used in combination. The solid reducing agent may have a shape and size that allows it to be blown into the hot air flow path 12 from the solid reducing agent outlet 14x. The solid reducing agent is blown in together with a carrier gas, such as an inert gas such as nitrogen gas or air.

[0042] 2. Blast Furnace Operation Method The technology disclosed herein also has an aspect as a blast furnace operation method. That is, a method for operating a blast furnace 100 according to one embodiment includes supplying hot air into the interior of the blast furnace 100 through the hot air flow path 12 of the tuyere body 11 of the hot air tuyere 10, and supplying a reducing gas containing a hydrogen-based reducing gas and a solid reducing material containing carbon to the hot air flow path 12 through a reducing gas outlet 13x facing the hot air flow path 12 and a solid reducing material outlet 14x facing the hot air flow path 12. Here, the length L between the tip 11x of the tuyere body 11 and the center of the reducing gas outlet 13x is １is the length L between the tip 11x of the tuyere body 11 and the center of the solid reducing material outlet 14x ２ The length L between the tip 11x of the tuyere body 11 and the center of the reducing gas outlet 13x is shorter than １ is 50 mm or more and 120 mm or less.

[0043] The details and preferred embodiments of the method for supplying the hot air, reducing gas, and solid reducing material are as described above. For example, in the method for operating the blast furnace 100 according to this embodiment, the length L between the tip 11x of the tuyere body 11 and the center of the reducing gas outlet 13x is １ However, the distance may be 50 mm or more and 75 mm or less. The method for operating the blast furnace 100 according to this embodiment may include supplying the reducing gas to the hot blast passage 12 from the reducing gas outlet 13x provided on the inner wall 11a of the tuyere body 11. The method for operating the blast furnace 100 according to this embodiment may also include supplying the reducing gas to the hot blast passage 12 from the reducing gas outlet 13x arranged inside the hot blast passage 12. The method for operating the blast furnace 100 according to this embodiment may also include supplying the reducing gas to the hot blast passage 12 from the solid reducing material outlet 14x provided on the inner wall 11a of the tuyere body 11. The method for operating the blast furnace 100 according to this embodiment may also include supplying the reducing gas to the hot blast passage 12 from the solid reducing material outlet 14x arranged inside the hot blast passage 12.

[0044] 3. Manufacturing Method of Hot Air Tuyere As described above, a hot air tuyere has a tuyere body, a hot air flow path, a reducing gas outlet, and a solid reducing material outlet. The hot air flow path is defined by the inner wall of the tuyere body, the reducing gas outlet faces the hot air flow path, the solid reducing material outlet faces the hot air flow path, the reducing gas blown out from the reducing gas outlet contains a hydrogen-based reducing gas, and the solid reducing material blown out from the solid reducing material outlet contains carbon. The technology of the present disclosure also has an aspect as a manufacturing method of a hot air tuyere having such a configuration. That is, a manufacturing method of a hot air tuyere according to one embodiment includes the following: a hydrogen combustion rate Z (%), a length L between the tip of the tuyere body and the center of the reducing gas outlet １ , and the length L between the tip of the tuyere body and the center of the solid reducing material outlet ２ and determining the length L of the hot blast tuyere based on the target hydrogen combustion rate Z (%) and the relational expression (1). １ and the length L ２ "Hydrogen combustion rate" refers to the ratio of O2 in the high-temperature air (hot air) among the reducing gases blown into the hot air tuyere. ２ It means the proportion of hydrogen that reacts with the fuel and is burned before it reaches the raceway. The "hydrogen combustion rate" can be calculated by performing a simulation using FLUENT, a general-purpose thermal fluid analysis software. The "actual dimensions" mean the actual dimensions of the hot blast tuyere that is manufactured. The length L １ and length L ２ The length L may be as described above. １ is the length L ２ may be shorter than the length L １ may be 50 mm or more and 120 mm or less.

[0045] In one embodiment of the method for manufacturing a hot blast tuyere, the hydrogen combustion rate Z (%) may be determined based on a predetermined relational expression (2) between the tuyere pressure drop change ΔP (kPa) and the hydrogen combustion rate Z (%), and a target tuyere pressure drop change ΔP (kPa). The "tuyere pressure drop change" is an index that indicates the pressure difference between a certain point inside the tuyere, which is set as 0, and the raceway. The "tuyere pressure drop change" can be calculated by performing a simulation using FLUENT, a general-purpose thermal fluid analysis software.

[0046] Specific examples of the above-mentioned relational expressions (1) and (2) are as follows. However, the relational expressions (1) and (2) are not limited to the following expressions. As described above, the hydrogen combustion rate Z (%) and the above-mentioned length L １ (mm) and the above length L ２ The relationship between the tuyere pressure drop change ΔP (kPa) and the hydrogen combustion rate Z (%) can be expressed by the following formula (1). By using these formulas, the hot blast tuyere can be manufactured appropriately. Z = 0.0016 × L １ -0.016 x L ２ +0.2282 (1) ΔP=177.51Z-18.337 (2)

[0047] The relation (1) is the length L １ and L ２ In addition, the relational expression (2) may include other parameters in addition to the tuyere pressure drop change ΔP and the hydrogen combustion rate Z. Examples of the other parameters include the solid reducing agent injection amount, the reducing gas injection amount, the solid reducing agent injection angle, the reducing gas injection angle, etc. It is believed that the calculation accuracy is improved by taking the other parameters into consideration.

[0048] 4. Supplementary Information In the operation of the blast furnace 100, for example, iron ore (iron oxide), coke, etc. may be charged into the interior of the blast furnace 100 from the top of the blast furnace 100. Hot air may be supplied into the interior of the blast furnace 100 from a hot stove outside the blast furnace 100 via a hot air pipe and hot air tuyere 10. Reducing gas may be supplied into the interior of the blast furnace 100 from a reducing gas supply source outside the blast furnace 100 via a reducing gas flow path 13, a reducing gas outlet 13x, and a hot air flow path 12. A solid reducing material may be supplied into the interior of the blast furnace 100 from a solid reducing material supply source outside the blast furnace 100 via a solid reducing material supply path 14, a solid reducing material outlet 14x, and a hot air flow path 12. The coke, solid reducing material, etc. supplied into the interior of the blast furnace 100 are combusted to generate reducing gas. The iron oxide is reduced and dissolved by the reducing gas generated by the combustion of the coke, solid reducing material, etc., or by the reducing gas supplied from the reducing gas outlet 13x, to obtain molten iron. The molten iron is tapped from a tap hole 102 provided at the bottom of the blast furnace 100. In this embodiment, by supplying the reducing gas into the inside of the blast furnace 100 through the reducing gas outlet 13x, the amount of coke, etc., and solid reducing material used can be reduced accordingly. As a result, CO ２ The amount of generated iron can be reduced. The blast furnace 100 can have various configurations as long as it is capable of producing pig iron as described above. For example, the blast furnace 100 may have other tuyere(s), port(s), or lance(s) in addition to the above-described hot blast tuyere(s) 10. Furthermore, the above-described hot blast tuyere(s) 10 may have other ports, lances, etc. in addition to the above-described hot blast channel 12, reducing gas channel 13, and solid reducing material supply channel 14. The configuration of the blast furnace 100 other than the hot blast tuyere(s) 10 is known in the art, and therefore will not be described in detail here.

[0049] 5. Effects As described above, according to this embodiment, when reducing gas and solid reducing material are supplied into a blast furnace through a hot blast tuyere, the combustion rate of the solid reducing material can be increased. This makes it possible to operate the blast furnace with high efficiency by utilizing the combustion heat of the solid reducing material.

[0050] The present invention will be further described below with reference to examples, but the present invention is not limited to these examples. The present invention allows for various conditions to be adopted as long as the gist of the invention is not deviated from and the object is achieved. In the following examples, a reducing gas consisting solely of hydrogen gas is used, but the type of reducing gas is not limited to this. It is believed that a similar effect can be achieved with any reducing gas containing a hydrogen-based reducing gas. In the following examples, a case in which pulverized coal is used as the solid reducing agent is exemplified, but the type of solid reducing agent is not limited to this. It is believed that a solid reducing agent containing carbon can achieve the same effect. In the following examples, the concentration of hydrogen molecules inside a blast furnace was evaluated by performing a simulation taking into account gas flow, heat transfer, and chemical reactions using the general-purpose thermal fluid analysis software FLUENT. The raceway region near the tuyere was treated as a cavity where no coke was present, and the coke-packed bed region in the blast furnace away from the raceway was treated as a porous medium. The standard k-ε model was used for turbulence analysis, the vortex dissipation model for gas combustion, and the O model for coke combustion. ２ , CO ２ , H ２ Field's model was used for the gasification reaction of O

[0051] Using simulation, the following were found: (1) When hydrogen gas at room temperature (20°C) is supplied into the hot air flow path from one hydrogen injection port that penetrates the upper wall of the tuyere body at a position 75 mm from the tip of the tuyere body, and pulverized coal is supplied into the hot air flow path from a pulverized coal injection lance at a position 150 mm from the tip of the tuyere body; (2) When hydrogen gas at room temperature (20°C) is supplied into the hot air flow path from two hydrogen injection ports that penetrate the upper wall of the tuyere body at a position 75 mm from the tip of the tuyere body, and pulverized coal is supplied into the hot air flow path from a pulverized coal injection lance at a position 150 mm from the tip of the tuyere body. (3) When hydrogen gas at room temperature (20°C) is supplied into the hot air flow path from one hydrogen injection port that penetrates the lower wall of the tuyere body at a position 75 mm from the tip of the tuyere body, and pulverized coal is supplied into the hot air flow path from a pulverized coal injection lance at a position 150 mm from the tip of the tuyere body. (4) When hydrogen gas at room temperature (20°C) is supplied into the blast furnace from one hydrogen injection port that penetrates the upper wall of the tuyere body at the tip (0 mm from the tip) of the tuyere body, and pulverized coal is supplied into the hot air flow path from a pulverized coal injection lance at a position 150 mm from the tip of the tuyere body. (5) When room temperature (20°C) hydrogen gas is supplied into the blast furnace from one hydrogen injection port penetrating the lower wall of the tuyere body at the tip (0 mm from the tip) of the tuyere body, and pulverized coal is supplied into the hot air flow path from a pulverized coal injection lance at a position 150 mm from the tip of the tuyere body. (6) When room temperature (20°C) hydrogen gas is supplied into the hot air flow path from one hydrogen injection lance at a position 150 mm from the tip of the tuyere body, and pulverized coal is supplied into the hot air flow path from a pulverized coal injection lance at a position 150 mm from the tip of the tuyere body. (7) When room temperature (20°C) hydrogen gas is supplied into the hot air flow path from two hydrogen injection lances at a position 150 mm from the tip of the tuyere body, and pulverized coal is supplied into the hot air flow path from a pulverized coal injection lance at a position 150 mm from the tip of the tuyere body. The pulverized coal combustion rate (%) and hydrogen combustion rate (%) were confirmed for each of the above. The flow rate of hydrogen gas was 4270 Nm ３ / hr, and the supply rate of pulverized coal was 1,316 kg / hr.

[0052] 3A and 3B show the relationship between the length between the tip of the tuyere body and the center of the reducing gas outlet and the pulverized coal combustion rate. In Fig. 3A, "upper inside tuyere" refers to the case of (1) above, "lance" refers to the case of (6) above, "upper tuyere tip" refers to the case of (4) above, and "upper inside tuyere, two lines" refers to the case of (2) above. In Fig. 3B, "lower inside tuyere" refers to the case of (3) above, "lower tuyere tip" refers to the case of (5) above, and "two lance lines" refers to the case of (7) above.

[0053] As far as the inventors have confirmed, the injection behavior when gas is injected from Lance 1 is similar to that when gas is injected from the top of the tuyere, and can be considered to be substantially the same. Furthermore, the injection behavior when gas is injected from Lance 2 is similar to that when gas is injected from the bottom of the tuyere, and can be considered to be substantially the same. That is, the four open plots shown in Figure 3A correspond to the cases where hydrogen gas is injected from the top of the tuyere and the distance from the tuyere tip to the hydrogen gas injection position is changed to 0 mm, 75 mm, or 150 mm. The three solid plots shown in Figure 3B correspond to the cases where hydrogen gas is injected from the bottom of the tuyere and the distance from the tuyere tip to the hydrogen gas injection position is changed to 0 mm, 75 mm, or 150 mm.

[0054] From the results shown in Figures 3A and 3B, it can be seen that the pulverized coal combustion rate is significantly improved when the length between the tip of the tuyere body and the center of the reducing gas outlet is around 75 mm, regardless of whether the reducing gas is injected from the reducing gas outlet provided at the top of the tuyere or from the reducing gas outlet provided at the bottom of the tuyere.

[0055] Figure 4 shows the relationship between the length between the tip of the tuyere body and the center of the reducing gas outlet and the hydrogen combustion rate in the hot blast channel. Figure 5 also shows the relationship between the change in pressure drop in the tuyere and the hydrogen combustion rate in the tuyere for pulverized coal injection operation. In Figures 4 and 5, the open triangle plot for "above the tuyere" and the black triangle plot for "below the tuyere" are plotted in the same position. Also, the open circle plot for "above the tuyere tip" and the black circle plot for "below the tuyere tip" are plotted in the same position. As shown in Figure 4, it can be seen that the shorter the length between the tip of the tuyere body and the center of the reducing gas outlet, the lower the hydrogen combustion rate. Furthermore, as shown in Figure 5, it can be seen that the pressure drop in the tuyere can be reduced by lowering the hydrogen combustion rate. From the results shown in Figures 3 to 5, from the viewpoint of improving the pulverized coal combustion rate, lowering the hydrogen combustion rate, and reducing the pressure loss in the tuyere, it can be said that the length between the tip of the tuyere body and the center of the reducing gas outlet is preferably, for example, 50 mm or more and 75 mm or less.

[0056] In the above example, hydrogen gas at room temperature is injected into the blast furnace from the tuyere body, but the temperature of the hydrogen gas is not limited to this. The trends shown in Figures 3A and 3B are obtained regardless of the hydrogen gas injection temperature.

[0057] REFERENCE SIGNS LIST 100 Blast furnace 10 Hot blast tuyere 11 Tuyere body 11a Inner wall 11b Outer wall 11x Tip 12 Hot blast passage 12x Opening 13 Reducing gas passage 13x Reducing gas outlet 14 Solid reducing material supply path 14x Solid reducing material outlet 20 Reducing gas supply source 21 Piping 30 Solid reducing material supply source 31 Piping

Claims

1. A blast furnace having a hot blast tuyere, the hot blast tuyere having a tuyere body, a hot blast passage, a reducing gas outlet, and a solid reducing material outlet, the hot blast passage is defined by an inner wall of the tuyere body, the reducing gas outlet faces the hot blast passage, the solid reducing material outlet faces the hot blast passage, the reducing gas blown out from the reducing gas outlet contains a hydrogen-based reducing gas, the solid reducing material blown out from the solid reducing material outlet contains carbon, and a length L between a tip of the tuyere body and a center of the reducing gas outlet １ The length L between the tip of the tuyere body and the center of the solid reducing material outlet ２ The length L between the tip of the tuyere body and the center of the reducing gas outlet is shorter than １ However, the diameter is between 50mm and 120mm in a blast furnace.

2. The blast furnace according to claim 1, wherein the length L between the tip of the tuyere body and the center of the reducing gas outlet is １ However, the diameter is between 50mm and 75mm in a blast furnace.

3. A blast furnace according to claim 1 or 2, wherein the reducing gas outlet is provided on the inner wall of the tuyere body.

4. A blast furnace according to claim 1 or 2, wherein the reducing gas outlet is arranged inside the hot blast flow path.

5. A blast furnace according to any one of claims 1 to 4, wherein the solid reducing material outlet is provided on the inner wall of the tuyere body.

6. A blast furnace according to any one of claims 1 to 4, wherein the solid reducing material outlet is arranged inside the hot blast flow path.

7. A method for operating a blast furnace, comprising: supplying hot air into the inside of the blast furnace through a hot air flow path of a tuyere body of a hot air tuyere; and supplying a reducing gas containing a hydrogen-based reducing gas and a solid reducing material containing carbon into the hot air flow path through a reducing gas outlet facing the hot air flow path and a solid reducing material outlet facing the hot air flow path; １ The length L between the tip of the tuyere body and the center of the solid reducing material outlet ２ The length L between the tip of the tuyere body and the center of the reducing gas outlet is shorter than １ A method for operating a blast furnace, wherein the thickness of the blast furnace is 50 mm or more and 120 mm or less.

8. A method for operating a blast furnace according to claim 7, wherein the length L between the tip of the tuyere body and the center of the reducing gas outlet is １ A method for operating a blast furnace, wherein the thickness of the blast furnace is 50 mm or more and 75 mm or less.

9. A method for operating a blast furnace according to claim 7 or 8, comprising supplying the reducing gas to the hot blast flow path from the reducing gas outlet provided on the inner wall of the tuyere body.

10. A method for operating a blast furnace according to claim 7 or 8, comprising supplying the reducing gas to the hot blast passage from the reducing gas outlet disposed inside the hot blast passage.

11. A method for operating a blast furnace according to any one of claims 7 to 10, comprising supplying the reducing gas to the hot blast flow path from the solid reducing material outlet provided on the inner wall of the tuyere body.

12. A method for operating a blast furnace according to any one of claims 7 to 10, comprising supplying the reducing gas to the hot blast passage from the solid reducing material outlet disposed inside the hot blast passage.

13. A method for manufacturing a hot air tuyere, the hot air tuyere having a tuyere body, a hot air flow path, a reducing gas outlet, and a solid reducing material outlet, the hot air flow path is defined by an inner wall of the tuyere body, the reducing gas outlet faces the hot air flow path, the solid reducing material outlet faces the hot air flow path, the reducing gas blown out from the reducing gas outlet contains a hydrogen-based reducing gas, and the solid reducing material blown out from the solid reducing material outlet contains carbon, the manufacturing method comprising: determining a hydrogen combustion rate Z (%), a length L between the tip of the tuyere body and the center of the reducing gas outlet, １ , and the length L between the tip of the tuyere body and the center of the solid reducing material outlet ２ and determining the length L of the hot blast tuyere based on the target hydrogen combustion rate Z (%) and the relational expression (1). １ and the length L ２ determining the actual dimensions of one or both of the hot air tuyere sizes.

14. A method for manufacturing a hot-air tuyere according to claim 13, wherein the hydrogen combustion rate Z (%) is determined based on a predetermined relational expression (2) between the tuyere pressure drop change ΔP (kPa) and the hydrogen combustion rate Z (%), and a target tuyere pressure drop change ΔP (kPa).

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