Method of injection of a reducing gas in a blast furnace, and, blast furnace

Description

/ 19 METHOD OF INJECTING A REDUCING GAS INTO A BLAST FURNACE, AND, BLAST FURNACE FIELD

[001] The present application describes a method of injecting a reducing gas into and for a blast furnace. FUNDAMENTALS

[002] Efforts are being made to reduce CO2 emissions in iron production processes. For example, when pig iron is produced in a blast furnace, a reducing gas, such as hydrogen gas, is often used to replace some of the coke or other reducing material. PTL 1 describes a method of injecting reducing gas into a blast furnace, in which a reducing gas injection lance is installed within the hot air flow passage or on the wall face of a hot jet tuyere, and the reducing gas is injected through the lance. Although it does not deal with the injection of a reducing gas, PTL 2 describes the insertion of a fuel injection lance on the wall face of a hot jet tuyere and the injection of pulverized coal as fuel into a blast furnace through the fuel injection lance. [LIST OF QUOTES] [PATENT LITERATURE]

[003] [PTL 1] Japanese Patent Publication No. 4997734

[004] [PTL 2] Japanese Patent Publication No. 5840202 SUMMARY [TECHNICAL PROBLEM]

[005] When a lance is situated in the flow passage of a hot jet tuyere, as described in PTL 1, the lance is exposed to hot air, potentially causing thermal damage to the lance. Furthermore, when a reducing gas with a low relative density is injected into the blast furnace via a reducing gas injection lance located in the hot jet tuyere, a skewed flow of the reducing gas tends to occur as... Petition 870260075940, dated 07 / 30 / 2026, page 14 / 38 / 19: the reducing gas rises along the wall faces of the blast furnace. Such skewed flow of reducing gas in the blast furnace has not been adequately examined in the state of the art. The present application describes a technology that allows easy control of thermal damage to a reducing gas injection lance when a reducing gas with a low relative density is injected into a blast furnace, also allowing suppression of the skewed flow of reducing gas. [SOLUTION TO THE PROBLEM]

[006] The present application describes the following aspects as means to solve this problem. <Aspecto 1>

[007] A method of injecting a reducing gas into a blast furnace, the method comprising: Injecting hot air into the blast furnace from a hot jet tuyer provided below the lower end of the blast furnace shaft and above the tap hole, while injecting a reducing gas into the blast furnace from a reducing gas injection lance that is provided on a wall face of the hot jet tuyer and that has an opening in the tip section of the hot jet tuyer, wherein: The reducing gas is a gas that acts as a reducing material inside the blast furnace; the relative density of the reducing gas is lower than the relative density of the hot air, and the central height position P1 of the reducing gas injection lance opening is equal to or lower than the central height position P2 of the hot air tuyere. <Aspecto 2>

[008] The method of injecting a reducing gas into a blast furnace according to aspect 1, wherein Petition 870260075940, dated 07 / 30 / 2026, page 15 / 38 / 19 the height position Pi is lower than the height position P2. <Aspecto 3>

[009] The method of injecting a reducing gas into a blast furnace according to aspect 1 or 2, wherein the reducing gas comprises hydrogen gas. <Aspecto 4>

[0010] A blast furnace having: a hot jet tuyere provided below the lower end of the blast furnace shaft and above the tap hole, and a reducing gas injection lance that is provided on a wall face of the hot jet tuyere and that has an opening in the tip section of the hot jet tuyere, wherein: The reducing gas injected into the blast furnace from the reducing gas injection lance is gas that acts as a reducing material inside the blast furnace; the relative density of the reducing gas is lower than the relative density of the hot air injected into the blast furnace by the hot air tuyere; and the central height position Pi of the reducing gas injection lance opening is equal to or lower than the central height position P2 of the hot air tuyere. <Aspecto 5>

[0011] The blast furnace according to aspect 4, wherein the height position P1 is lower than the height position P2. <Aspecto 6>

[0012] The blast furnace according to aspect 4 or 5, in which the reducing gas comprises hydrogen gas. [ADVANTAGEOUS EFFECTS OF THE INVENTION]

[0013] With the technology of the present invention, it is possible to reduce thermal damage to the reducing gas injection lance when a reducing gas with Petition 870260075940, dated 07 / 30 / 2026, page 16 / 38 / 19 low relative density is injected into a blast furnace from the reducing gas injection lance, and inhibit the skewed flow of the reducing gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic view showing an example of the structure of a blast furnace. Some parts of the blast furnace construction have been omitted.

[0015] Figure 2 schematically shows an example of the construction of the lance tip section in the tip section of a hot jet tuyer.

[0016] Figure 3A schematically shows an example of the positional relationship between a hot jet tuyere and a reducing gas injection lance in a blast furnace.

[0017] Figure 3B schematically shows an example of the positional relationship between a hot jet tuyere and a reducing gas injection lance in a blast furnace.

[0018] Figure 3C schematically shows an example of the positional relationship between a hot jet tuyere and a reducing gas injection lance in a blast furnace.

[0019] Figure 4 schematically shows the positional relationships between different hot jet tuyeres and a boom opening for a State of the Art Example, Examples 1 to 3 and Comparative Examples 1 and 2. DESCRIPTION OF THE MODALITIES

[0020] The embodiments of the reducing gas injection method in a blast furnace and of a blast furnace, according to the present invention, will now be described. However, the reducing gas injection method in a blast furnace and the blast furnace described are not limited to the embodiments described below. 1. Method of injecting a reducing gas into a blast furnace.

[0021] As shown in Figure 1, the gas injection method Petition 870260075940, dated 07 / 30 / 2026, page 17 / 38 / 19 reducing agent in a blast furnace 10 according to an embodiment comprising: injecting hot air into the blast furnace 10 from a hot jet tuyer 13 provided below the lower end 11ax of the blast furnace 10 shaft and above the tap hole 12, while injecting reducing gas into the blast furnace 10 from a reducing gas injection lance 14, which is provided on the wall face of the hot jet tuyer 13 and which has an opening 14a in the tip section 13a of the hot jet tuyer 13.

[0022] Reducing gas is a gas that functions as a reducing material inside the blast furnace 10.

[0023] The relative density of the reducing gas is less than the relative density of hot air.

[0024] The central height position P1 of the opening 14a of the reducing gas injection lance 14 is equal to or lower than the central height position P2 of the hot jet tuyere 13. 1.1 Hot jet vent

[0025] Blast furnace 10 has a hot jet tuyere 13 that is below the lower end 11ax of the shaft and above the tap hole 12. The term “lower end of the shaft” refers to the boundary section between the shaft 11a and the furnace belly 11b. The term “shaft” refers to the section above furnace belly 11b, where the furnace diameter normally increases from top to bottom. The term “furnace belly” refers to the section lowest in the shaft and above the furnace 11c, where the furnace diameter is generally at its maximum. The furnace diameter (diameter) of furnace belly 11b can be 5 m 20 m, or 10 m 18 m, for example. The term “tapping hole” refers to a hot metal tapping hole provided in the bottom of blast furnace 10. The term “hot air tuyere” refers to a nozzle for injecting hot air into the blast furnace. Blast furnace 10 may have the hot air tuyere 13 below the lower end of the furnace belly 11bx and above the tapping hole 12, or it may have the Petition 870260075940, dated 07 / 30 / 2026, page 18 / 38 / 19 hot jet vent 13 below the lower end of the bosch 11cx and above the race hole 12.

[0026] This hot jet tuyere construction 13 is public knowledge. For example, the hot jet tuyere 13 may have a water-cooled structure. The hot jet tuyere 13 may be connected to an air heating furnace mounted on the outside of the blast furnace 10 by means of a hot air tube. In other words, the blast furnace 10 may be constructed so that hot air is injected into the blast furnace 10 from an air heating furnace through the hot air tube and the hot jet tuyere 13. The diameter of the hot jet tuyere 13 (the diameter equivalent to the circle of the opening facing the inside of the blast furnace 10, or the nozzle diameter) may be from 20 mm to 400 mm, or from 40 mm to 300 mm, for example.

[0027] The number of hot jet tuyeres 13 provided in blast furnace 10 is not particularly restricted and can be determined according to the internal volume of the blast furnace. For example, a plurality of hot jet tuyeres 13 may be situated in blast furnace 10 in the circumferential direction of blast furnace 10. In other words, in blast furnace 10, the plurality of hot jet tuyeres 13 may be arranged in the circumferential direction, viewed from above. The central height position P2 of the plurality of hot jet tuyeres 13 will generally be the same. 1.2 Reducing gas injection lance

[0028] Blast furnace 10 has a reducing gas injection lance 14. The reducing gas injection lance 14 can be connected to a reducing gas supply source provided outside blast furnace 10, by means of a reducing gas supply channel, for example. In other words, blast furnace 10 can be constructed so that the reducing gas is injected into blast furnace 10 from a reducing gas supply source, through a reducing gas supply channel and by the reducing gas injection lance 14. Petition 870260075940, dated 07 / 30 / 2026, page 19 / 38 / 19 There are no specific restrictions regarding the shape of the reducing gas supply source or the reducing gas supply channel.

[0029] For this embodiment, it is important that the reducing gas injection lance 14 be provided on the wall face of the hot jet tuyer 13. The fact that the “reducing gas injection lance is provided on the wall face of the hot jet tuyer” does not mean that it is necessarily embedded within the wall face of the hot jet tuyer up to the tip of the lance, as shown in Figure 1, and, for example, as shown in Figure 2, the phrase includes forms in which at least part of the lance comes into contact more internally than the wall face of the hot jet tuyer, while remaining exposed in the flow passage of the hot jet tuyer.In other words, provided that at least a portion of the entire periphery of the lance is located more internally than the wall face of the hot jet tuyere, allowing the reducing gas injection lance to be cooled by the water-cooled structure within the hot jet tuyere (i.e., provided that thermal damage to the lance can be suppressed), the reducing gas injection lance may have at least a portion of its entire periphery exposed in the flow passage of the hot jet tuyere. From the point of view of further inhibiting thermal damage to the reducing gas injection lance, preferably, the entire periphery of the reducing gas injection lance in the hot jet tuyere is provided within the wall face of the hot jet tuyere.For this embodiment, the reducing gas injection lance 14 has an opening 14a in the tip section 13a of the hot jet tuyer 13 and is constructed so that the reducing gas is injected into the blast furnace 10 through the opening 14a. The phrase “the reducing gas injection lance has an opening in the tip section of the hot jet tuyer” means that the reducing gas injection lance is open at or near the tip of the hot jet tuyer. For this embodiment, it is not necessary for the end face of the hot jet tuyer and the lance opening to be aligned (the lance tip reaching the tuyer tip). Petition 870260075940, dated 07 / 30 / 2026, page 20 / 38 / 19 of hot jet). That is, the phrase “having an opening in the tip section of the hot jet tuyer” includes forms in which the end face of the hot jet tuyer and the boom opening are aligned (the boom tip reaching the tip of the hot jet tuyer), but also forms in which the boom tip approaches the tip of the hot jet tuyer. Specifically, when the distance from the boom tip to the tip of the hot jet tuyer is from 0 mm to 50 mm, the boom is considered to “have an opening in the tip section of the hot jet tuyer”.According to this embodiment, therefore, if the reducing gas injection lance 14 is provided within the wall face of the hot jet tuyer 13, the probability of the reducing gas injection lance 14 being exposed to hot air will be lower and, even if it is exposed to hot air, the reducing gas injection lance 14 can be cooled by the water cooling structure within the wall face of the hot jet tuyer 13, thus helping to reduce thermal damage to the reducing gas injection lance 14.

[0030] The diameter of the opening 14a of the reducing gas injection lance 14 (the diameter equivalent to the circle of the opening facing the interior of the blast furnace 10) can be from 10 mm to 50 mm, or from 20 mm to 30 mm, for example. Alternatively, the diameter of the opening 14a of the reducing gas injection lance 14 can be from 0.05% to 0.8% or from 0.1% to 0.5% of the diameter of the hot jet tuyere 13.

[0031] The number of reducing gas injection lances 14 provided in blast furnace 10 is not particularly restricted. For example, at least one reducing gas injection lance 14 may be provided in one or more hot jet tuyeres 13 provided in blast furnace 10. In other words, when blast furnace 10 has a plurality of hot jet tuyeres 13, only some of the hot jet tuyeres 13 may have a reducing gas injection lance 14, or all of them may have a reducing gas injection lance 14. A reducing gas injection lance 14 may also be provided for a single Petition 870260075940, dated 07 / 30 / 2026, page 21 / 38 / 19 hot jet tuyere 13, or a plurality of reducing gas injection lances 14 may be provided. The central height position Pi of each opening 14a of the plurality of reducing gas injection lances 14 may be the same or different. 1.3 Positional relationship between the hot jet tuyere and the opening of the reducing gas injection lance

[0032] For this embodiment, it is important that the central height position P1 of the opening 14a of the reducing gas injection lance 14 be equal to the central height position P2 of the hot jet tuyere 13, or lower than the height position P2. Based on the knowledge recently acquired by the present inventors, when the central height position P1 of the opening 14a of the reducing gas injection lance 14 is located higher than the central height position P2 of the hot jet tuyere 13, the reducing gas injected by means of the reducing gas injection lance 14 tends to rise along the wall faces of the blast furnace 10, resulting in a skewed flow of the reducing gas inside the blast furnace 10.Conversely, when the central height position P1 of the opening 14a of the reducing gas injection lance 14 is equal to or lower than the central height position P2 of the hot jet tuyere 13, the amount of reducing gas flowing below the hot air inside the blast furnace 10 increases, while the amount of reducing gas rising along the wall faces decreases, so that the reducing gas more easily reaches the center in the radial direction inside the blast furnace 10 (the furnace center). As a result, the skewed flow of reducing gas inside the blast furnace 10 is suppressed, and the efficiency of reducing gas utilization is improved. The effect of suppressing the skewed flow of reducing gas is even more observable when the central height position P1 of the opening 14a of the reducing gas injection lance 14 is located below the central height position P2 of the hot jet tuyere 13.

[0033] Figures 3A and B show cases where the central height position P1 of the opening 14a of the reducing gas injection lance 14 is located Petition 870260075940, dated 07 / 30 / 2026, page 22 / 38 / 19 below the central height position P2 of the hot jet tuyer 13. The center of the opening 14a of the reducing gas injection lance 14 can be provided directly below the center of the hot jet tuyer 13, as illustrated in Figure 3A. That is, the location at the center of the opening 14a of the reducing gas injection lance 14 in the circumferential direction of the blast furnace 10 may be the same as the location of the center of the hot jet tuyere 13. Alternatively, as shown in Figure 3B, the center of the opening 14a of the reducing gas injection lance 14 may be provided below, at an angle relative to the center of the hot jet tuyere 13. That is, the center of the opening 14a of the reducing gas injection lance 14 may be situated at a different location from the center of the hot jet tuyere 13 in the circumferential direction of the blast furnace 10.

[0034] Figure 3C shows a case where the central height position P1 of the opening 14a of the reducing gas injection lance 14 is the same as the central height position P2 of the hot jet tuyer 13. The opening 14a of the reducing gas injection lance 14 can also be provided next to the hot jet tuyer 13, as illustrated in Figure 3C. 1.4 Hot air

[0035] The hot air injected by the hot jet tuyere 13 may consist of air or oxygen-enriched air, for example. The temperature of the hot air may be 1000°C or higher, for example. The temperature of the hot air may be 1000°C to 2000°C, 1000°C to 1700°C, 1000°C to 1500°C or 1000°C to 1300°C. The hot air flow velocity in the hot jet tuyere 13 (hot air flow rate (m³ / s) / open area of ​​the hot jet tuyere 13 outlet (m²)) may be adjusted as appropriate to the operating conditions of the blast furnace 10. According to one embodiment, the hot air flow velocity may be the flow velocity V1 described below. 1.5 Reducing gas

[0036] The reducing gas injected by the reducing gas injection lance 14 is Petition 870260075940, dated 07 / 30 / 2026, page 23 / 38 / 19 a gas that functions as a reducing material within blast furnace 10. Specifically, the term “reducing gas,” as used in this document, includes the concept of a gas that can generate a reducing material (reducing components) by thermal decomposition within blast furnace 10, even if it is a gas that does not function as a reducing material before being injected into blast furnace 10. The relative density of the reducing gas is lower than the relative density of the hot air injected into blast furnace 10 through the hot jet tuyere 13. Examples of such reducing gases include one or more selected from hydrogen gas, hydrocarbon gas (such as methane gas), carbon monoxide gas, and ammonia gas. When the reducing gas comprises hydrogen gas, an even greater effect can be expected from the technology described. The temperature of the reducing gas injected by the reducing gas injection lance 14 can be from 0°C to 2000°C, or 25°C to 1500°C, for example.For this embodiment, the flow velocity of the reducing gas at opening 14a of the reducing gas injection lance 14 (reducing gas flow rate (m3 / s) / open area of ​​the reducing gas injection lance outlet 14 (m2)) can reach the speed of sound at the operating temperature of the reducing gas, for example. According to one embodiment, the flow velocity of the reducing gas injected by the reducing gas injection lance 14 can be the flow velocity V2 described below. 1.6 Hot Air Flow Velocity and Reducing Gas Flow Velocity

[0037] The flow velocity V1 of the hot air injected from the hot jet tuyere 13 is not particularly restricted and, for example, if the flow velocity V1 is 100 m / s 1,000 m / s and especially 200 m / s 400 m / s, it will be even easier to inhibit the diverted flow of the reducing gas inside the blast furnace 10. The flow velocity V2 of the reducing gas injected through the reducing gas injection lance 14 is also not particularly restricted, and, for example, if the flow velocity V2 is 100 m / s 1,000 m / s and especially 200 m / s 800 m / s, then the air permeation inside the blast furnace 10 will be stabilized and the reduction reaction in the furnace will occur in a manner Petition 870260075940, dated 07 / 30 / 2026, page 24 / 38 / 19 stable. 1.7 Other gases

[0038] Other gases may also be injected into the reducing gas injection lance 14 along with the reducing gas. Examples of other gases include inert gases such as nitrogen gas. 2. Blast furnace

[0039] Although one aspect of the technology described is a method of injecting reducing gas into a blast furnace, another aspect is the blast furnace itself. Specifically, as illustrated in Figure 1, blast furnace 10, according to one embodiment, has: a hot jet tuyere 13 provided below the lower end 11ax of the blast furnace shaft 10 and above the tap hole 12, and a reducing gas injection lance 14 provided within the wall face of the hot jet tuyere 13 and having an opening 14a in the tip section 13a of the hot jet tuyere 13.

[0040] The reducing gas injected into blast furnace 10 by the reducing gas injection lance 14 is a gas that functions as a reducing material inside blast furnace 10.

[0041] The relative density of the reducing gas is lower than the relative density of the hot air injected into the blast furnace 10 through the hot jet tuyer 13.

[0042] The central height position P1 of the opening 14a of the reducing gas injection lance 14 is equal to or lower than the central height position P2 of the hot jet tuyere 13.

[0043] As mentioned above, when the height position P1 is lower than the height position P2 in blast furnace 10, it is believed that the effect of inhibiting the skewed flow of the reducing gas is even greater. When the reducing gas comprises hydrogen gas, the effect of the described technology may be even greater. Petition 870260075940, dated 07 / 30 / 2026, page 25 / 38 / 19 3. Additional observations

[0044] During the operation of blast furnace 10, for example, iron ore (iron oxide) or coke is charged from the top of blast furnace 10 into blast furnace 10, while hot air is injected into blast furnace 10 from an external air heating furnace of blast furnace 10 through the hot air tube and hot jet tuyer 13, and reducing gas is injected into blast furnace 10 from an external reducing gas supply source of blast furnace 10, through the reducing gas flow path and by the reducing gas injection lance 14. The coke supplied to blast furnace 10 undergoes combustion to generate reducing gas. The iron oxide is reduced and dissolved by the reducing gas produced by the combustion of the coke, for example, or by the reducing gas injected by the reducing gas injection lance 14, to obtain hot metal. The hot metal exits through the tap hole 12 provided at the lower end of the blast furnace 10.According to this embodiment, the injection of reducing gas into blast furnace 10 by the reducing gas injection lance 14 can correspondingly reduce the amount of carbon-containing reducing material used, such as coke. As a result, it is possible to reduce the amount of CO2 generated. Blast furnace 10 may have any of several constructions, provided it allows the production of pig iron as described above. Blast furnace 10 may also have another tuyere or lance in addition to the hot jet tuyere 13 or the reducing gas injection lance 14 described above. Another reducing gas injection lance may also be present above the hot jet tuyere 13 in blast furnace 10. Aspects of the construction of blast furnace 10, other than the hot jet tuyere 13 and the reducing gas injection lance 14, are public knowledge in the technical field and will not be described in detail here. 4. Effect

[0045] As explained above, according to this embodiment, the reducing gas injection lance 14 is provided within a face wall of the hot jet nozzle 13, thus helping to avoid thermal damage. Petition 870260075940, dated 07 / 30 / 2026, page 26 / 38 / 19 to the lance. Furthermore, according to this modality, if the central height position Pi of the opening 14a of the reducing gas injection lance 14 is equal to or lower than the central height position P2 of the hot jet tuyere 13, then it will be possible to reduce the skewed flow of reducing gas inside the blast furnace 10. EXAMPLES

[0046] The present invention will now be described in more detail using Examples, it being understood that these Examples are not intended to be limiting of the invention. The invention can be applied under a variety of different conditions that do not depart from its essence and that allow its objective to be achieved. The following Examples are illustrative cases in which hydrogen gas was used as a reducing gas, but the type of reducing gas is not limited to these cases.

[0047] A simulation model was used to change the location where a reducing gas was injected, while comparing the difference in hydrogen concentrations on the furnace wall, on the uppermost side of the blast furnace charge, and in the central section of the furnace. Specifically, the difference in hydrogen concentration was determined for the following Prior Art Examples, Examples 1 to 3 and Comparative Examples 1 to 2.

[0048] State of the Art Example: As shown in the “State of the Art Example” of Figure 4, a lance was inserted into the hot air flow passage of a hot jet tuyer (outside the wall face), so that the center of the opening at the tip of the lance was located in the center of the opening of the hot jet tuyer. Hot air was injected through the hot jet nozzle, while hydrogen gas was injected through the lance.

[0049] Example 1: As indicated in “Example 1” of Figure 4, the lance was inserted into the wall face of the hot jet tuyer, so that the center of the opening at the tip of the lance was located directly below the Petition 870260075940, dated 07 / 30 / 2026, page 27 / 38 / 19 center of the hot jet nozzle opening. Hot air was injected through the hot jet nozzle, while hydrogen gas was injected through the lance.

[0050] Example 2: As indicated in “Example 2” of Figure 4, the lance was inserted into the wall face of the hot jet tuyer, so that the center of the opening at the tip of the lance was located at an angle below the center of the opening of the hot jet tuyer. Hot air was injected through the hot jet nozzle, while hydrogen gas was injected through the lance.

[0051] Example 3: As indicated in “Example 3” of Figure 4, the lance was inserted into the wall face of the hot jet tuyer, so that the central height position of the opening at the tip of the lance was the same as the central height position of the opening of the hot jet tuyer. Hot air was injected through the hot jet nozzle, while hydrogen gas was injected through the lance.

[0052] Comparative Example 1: As indicated in “Comparative Example 1” of Figure 4, the lance was inserted into the wall face of the hot jet tuyer, so that the center of the opening at the tip of the lance was located at an angle above the center of the opening of the hot jet tuyer. Hot air was injected through the hot jet nozzle, while hydrogen gas was injected through the lance.

[0053] Comparative Example 2: As indicated in “Comparative Example 2” of Figure 4, the lance was inserted into the wall face of the hot jet tuyer, so that the center of the opening at the tip of the lance was located directly above the center of the opening of the hot jet tuyer. Hot air was injected through the hot jet nozzle, while hydrogen gas was injected through the lance.

[0054] The results are shown in Table 1 below. Petition 870260075940, dated 07 / 30 / 2026, page 28 / 38 / 19 [Table 11] Example of the State of the Art Example 1 Example 2 Example 3 Ex. Comp. 1 Ex. Comp. 2 Lance Location Outside the wall face Inside the wall face Inside the wall face Inside the wall face Inside the wall face Inside the wall face Initial Lance Position Center Directly below Below, at an angle Directly to the side Above, at an angle Directly above Hydrogen Concentration Difference [%] 2 2 3 4 8 9

[0055] As can be clearly observed in the results of Table 1, when the central height position of the reducing gas injection lance opening was equal to or lower than the central height position of the hot jet tuyer, as in the Prior Art Example and Examples 1 to 3, practically no difference was observed in the hydrogen concentration on the upper side of the furnace charge. This may occur because the hydrogen gas and hot air were sufficiently mixed at the tuyer level, so that the hydrogen dispersed along with the hot air in the furnace. However, when the tip section of the reducing gas injection lance was not in contact with the wall face of the hot jet tuyer, so that the entire periphery of the lance was exposed in the flow passage of the hot jet tuyer, as in the Prior Art Example, this tended to result in thermal damage to the lance caused by the hot air.The durability of the lance is therefore a problem in the implementation of the State of the Art Example. However, this problem can be solved by situating the reducing gas injection lance within the wall face of the hot jet tuyere (at least part of the entire periphery of the lance being situated within the wall face of the hot jet tuyere), as in Examples 1 to 3. In other words, Examples 1 to 3 are more advantageous than the State of the Art Example, both from the point of view of inhibiting the skewed flow of the reducing gas and reducing thermal damage to the lance. Petition 870260075940, dated 07 / 30 / 2026, page 29 / 38 / 19

[0056] On the other hand, when the central height position of the reducing gas injection lance opening was higher than the central height position of the hot jet tuyer, as in Comparative Examples 1 and 2, a significant difference in hydrogen concentration was observed between the center of the furnace and the furnace wall section on the uppermost side of the furnace load. This may be due to the fact that the relative density of hydrogen gas is lower than the relative density of air (hot air), such that the hydrogen gas preferentially flows along the sides of the wall inside the furnace without being compressed by the hot air injected by the hot jet tuyer.

[0057] It can therefore be concluded that providing the reducing gas injection lance on the wall face of the hot jet tuyere can inhibit thermal damage to the lance. When a reducing gas injection lance is provided on the wall face of the hot jet tuyere and the lance opening is located at the tip section of the hot jet tuyere, with the injection of a reducing gas through the lance, it will be possible to prevent the skewed flow of the reducing gas inside the blast furnace if the central height position P1 of the lance opening is equal to or lower than the central height position P2 of the hot jet tuyere.

[0058] To summarize these results, it can be concluded that by injecting a reducing gas with a low relative density into a blast furnace using the following method (1) and blast furnace (2), it is possible to reduce thermal damage to the reducing gas injection lance and prevent biased flow of the reducing gas.

[0059] (1) A method of injecting a reducing gas into a blast furnace, the method comprising: Injecting hot air into the blast furnace from a hot jet tuyer located below the lower end of the blast furnace shaft and above the tap hole, while injecting a reducing gas into the blast furnace from a reducing gas injection lance located on a wall face of the tuyere. Petition 870260075940, dated 07 / 30 / 2026, page 30 / 38 / 19 hot jet and which has an opening in the tip section of the hot jet nozzle, in which: The reducing gas is a gas that acts as a reducing material inside the blast furnace; the relative density of the reducing gas is lower than the relative density of the hot air, and the central height position P1 of the reducing gas injection lance opening is equal to or lower than the central height position P2 of the hot air tuyere.

[0060] (2) A blast furnace having: a hot jet tuyere provided below the lower end of the blast furnace shaft and above the tap hole, and a reducing gas injection lance that is provided on a wall face of the hot jet tuyere and that has an opening in the tip section of the hot jet tuyere, wherein: The reducing gas injected into the blast furnace from the reducing gas injection lance is gas that acts as a reducing material inside the blast furnace; the relative density of the reducing gas is lower than the relative density of the hot air injected into the blast furnace by the hot air tuyere; and the central height position Pi of the reducing gas injection lance opening is equal to or lower than the central height position P2 of the hot air tuyere. LIST OF REFERENCE SIGNS

[0061] 10 Blast furnace Oven belly Racing hole Hot jet vent 13th Section tip Petition 870260075940, dated 07 / 30 / 2026, page 31 / 38 / 19 Reducing gas injection lance 14th Opening Petition 870260075940, dated 07 / 30 / 2026, pages 32 / 38

Claims

1 / 2 CLAIMS 1.A method for injecting a reducing gas into a blast furnace, characterized in that it comprises: injecting hot air into the blast furnace from a hot jet tuyere provided below the lower end of the blast furnace shaft and above the tap hole, while injecting a reducing gas into the blast furnace from a reducing gas injection lance that is provided on a wall face of the hot jet tuyere and that has an opening in the tip section of the hot jet tuyere, wherein: the distance from the tip of the reducing gas injection lance to the tip of the hot jet tuyere is from 0 mm to 50 mm, the reducing gas is a gas that functions as a reducing material within the blast furnace, the relative density of the reducing gas is less than that relative density of the hot air, and the central height position Pi of the opening of the reducing gas injection lance is equal to or less than the central height position P2 of the hot air tuyere.

2. A method for injecting a reducing gas into a blast furnace according to claim 1, characterized in that: the height position Pi is lower than the height position P2.

3. A method for injecting a reducing gas into a blast furnace according to claim 1 or 2, characterized in that: the reducing gas comprises hydrogen gas.

4. Blast furnace, characterized by the fact that it has: a hot jet tuyere provided below the furnace belly of the blast furnace and above the tap hole, and a reducing gas injection lance that is provided on one face. Petition 870260082599, dated 08 / 14 / 2026, page 1. 10 / 14 2 / 2 wall of the hot jet tuyere and having an opening in the tip section of the hot jet tuyere, wherein: the distance from the tip of the reducing gas injection lance to the tip of the hot jet tuyere is from 0 mm to 50 mm, the reducing gas injected into the blast furnace from the reducing gas injection lance is gas that functions as a reducing material within the blast furnace, the relative density of the reducing gas is less than that relative density of the hot air injected into the blast furnace by the hot air tuyere, and the central height position Pi of the reducing gas injection lance opening is equal to or less than the central height position P2 of the hot air tuyere.

5. Blast furnace according to claim 4, characterized in that: the height position Pi is lower than that height position P2.

6. Blast furnace according to claim 4 or 5, characterized in that: the reducing gas comprises hydrogen gas. Petition 870260082599, dated 08 / 14 / 2026, page 11 / 14

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