Method of injecting a reducing gas into a blast furnace, and, blast furnace

Description

21 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 flow passage of a hot wind tuyere, and the reducing gas is injected through the lance and the tuyere. Although it does not deal with the injection of a reducing gas, PTL 2 describes the insertion of a fuel injection lance into the wall face of a hot wind 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 span is situated within a hot wind tuyere, as described in PTL 1, the span diameter must be reduced depending on the shape and size of the hot wind tuyere. Consequently, if a large quantity of reducing gas is injected through the span situated within the hot wind tuyere, the flow velocity of the reducing gas will exceed the speed of sound. Therefore, the prior art Petition 870260063963, dated 06 / 29 / 2026, page 14 / 41 / 21, still presents room for improvement in terms of controlling the flow rate of the reducing gas. When a reducing gas with low relative density is injected into a blast furnace, the reducing gas tends to rise along the faces of the blast furnace walls, resulting in a skewed flow of the reducing gas. Such skewed flow of reducing gas in the blast furnace was not adequately examined in the prior art. From this point of view, the present application describes a technique that allows easy control of the flow rate of a reducing gas with low relative density being injected into a blast furnace, while simultaneously allowing the suppression of the skewed flow of the 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 air 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 inlet provided below the lower end of the blast furnace shaft and above the tap hole, 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 less than the relative density of the hot air; the reducing gas injection inlet is provided separately from the hot air tuyere; and the central height P1 of the reducing gas injection inlet is equal to the central height P2 of the hot air tuyere, or Petition 870260063963, dated 06 / 29 / 2026, page 15 / 41 / 21 is smaller than that position of height P2. <Aspecto 2>

[008] The method of injecting a reducing gas into a blast furnace according to aspect 1, wherein the position of height P1 is less than the position of height 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 air tuyere provided below the lower end of the blast furnace shaft and above the tap hole, and a reducing gas injection inlet provided below the lower end of the blast furnace shaft and above the tap hole, wherein: The reducing gas injected into the blast furnace through the reducing gas injection inlet is gas that functions as a reducing material within the blast furnace; the relative density of the reducing gas is less than the relative density of the hot air injected into the blast furnace through the hot air tuyere; the reducing gas injection inlet is provided separately from the hot air tuyere; and the central height position P1 of the reducing gas injection inlet is equal to or less than the central height position P2 of the hot air tuyere. <Aspecto 5>

[0011] The blast furnace according to aspect 4, where the position of height P1 is less than the position of height P2. <Aspecto 6> Petition 870260063963, dated 06 / 29 / 2026, page 16 / 41 / 21

[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 control the flow rate of a reducing gas with low relative density that is injected into a blast furnace, and to inhibit the skewed flow of the reducing gas. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0015] Figure 2A schematically shows an example of the positional relationship between the hot air tuyere and the reducing gas injection inlet in a blast furnace.

[0016] Figure 2B schematically shows an example of the positional relationship between the hot air tuyere and the reducing gas injection inlet in a blast furnace.

[0017] Figure 2C schematically shows an example of the positional relationship between the hot air tuyere and the reducing gas injection inlet in a blast furnace.

[0018] Figure 3A schematically shows the positional relationship between the hot air wind vane and the pitch as an example of the previous technique.

[0019] Figure 3B schematically shows the positional relationship between the hot air tuyere and the reducing gas injection tuyere, for Example 1.

[0020] Figure 3C schematically shows the positional relationship between the hot air tuyere and the reducing gas injection tuyere, for Example 2.

[0021] The 3D figure schematically shows the positional relationship between the hot air tuyere and the reducing gas injection tuyere, by Petition 870260063963, dated 06 / 29 / 2026, page 17 / 41 / 21 Example 3.

[0022] Figure 3E schematically shows the positional relationship between the hot air tuyere and the reducing gas injection tuyere, for Example 4.

[0023] Figure 3F schematically shows the positional relationship between the hot air tuyere and the reducing gas injection tuyere, for Comparative Example 1.

[0024] Figure 3G schematically shows the positional relationship between the hot air tuyere and the reducing gas injection tuyere, for Comparative Example 2.

[0025] Figure 3H schematically shows the positional relationship between the hot air tuyere and the reducing gas injection tuyere, for Comparative Example 3. DESCRIPTION OF THE MODALITIES

[0026] 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.

[0027] As shown in Figure 1, the method of injecting a reducing gas into a blast furnace 10 according to one embodiment comprises: inject hot air into blast furnace 10 from a hot air tuyere 13 provided below the lower end 11ax of blast furnace shaft 10 and above the tap hole 12, while injecting reducing gas into blast furnace 10 from a reducing gas injection inlet 14 provided below the lower end 11ax of blast furnace shaft 10 and above the tap hole 12.

[0028] Reducing gas is a gas that functions as a reducing material inside the blast furnace 10. Petition 870260063963, dated 06 / 29 / 2026, page 18 / 41 / 21

[0029] The relative density of the reducing gas is less than the relative density of hot air.

[0030] The reducing gas injection inlet 14 is provided separately from the hot air vent 13.

[0031] The central height position Pi of the reducing gas injection inlet 14 is the same as the central height position P2 of the hot air tuyere 13, or lower than that height position P2. 1.1 Hot wind breeze

[0032] The blast furnace 10 has a hot air tuyere 13 which 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 the 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 Bosch 11c, where the furnace diameter is generally at its maximum. The furnace diameter (diameter) of the furnace belly 11b may be 5 m 20 m, or 10 m 18 m, for example. The term “tap hole” refers to a hot metal tap hole provided at the bottom of the 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 hot air tuyeres 13 below the lower end of furnace belly 11bx and above the tap hole 12, or it may have hot air tuyeres 13 below the lower end of Bosch 11cx and above the tap hole 12.

[0033] This construction of the hot air tuyere 13 is public knowledge. For example, the hot air tuyere 13 may have a water-cooled structure. The hot air 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. Petition 870260063963, dated 06 / 29 / 2026, p. 19 / 41 / 21 of an air heating furnace through the hot air tube and the hot air tuyere 13. The diameter of the hot air tuyere 13 (the diameter equivalent to the circle of the opening facing inwards from the blast furnace 10, or the diameter of the nozzle) can be from 20 mm to 400 mm, or from 40 mm to 300 mm, for example.

[0034] The number of hot air tuyeres 13 provided in blast furnace 10 is not particularly restricted and can be determined according to the internal volume of the blast furnace. A plurality of hot air 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 air tuyeres 13 may be arranged in the circumferential direction, viewed from above. The position of the central height P2 of the plurality of hot air tuyeres 13 will generally be the same. 1.2 Reducing gas injection inlet

[0035] Blast furnace 10 has a reducing gas injection inlet 14 that is below the lower end 11ax of the shaft and above the tap hole 12. This will allow the reduction reaction to occur efficiently within blast furnace 10. Furthermore, when a reducing gas injection inlet 14 is provided near the hot air tuyere in the direction of furnace height, below the lower end 11ax of the shaft and above the tap hole 12, the discharge of hot metal or slag is less likely to be impeded by the reducing gas injection inlet 14.

[0036] There are no specific restrictions as to the shape of the reducing gas injection inlet 14. The reducing gas injection inlet 14 may also be a tuyere (nozzle), for example. The reducing gas injection inlet 14 may be defined using a metal (such as copper) or a refractory material.

[0037] In blast furnace 10, molten iron or slag may potentially fall into the reducing gas injection inlet 14. When hydrogen gas is injected as a reducing gas through the gas injection inlet Petition 870260063963, dated 06 / 29 / 2026, page 20 / 41 / 21 reducing gas 14 to reduce the amount of carbon material added, the amount of heat inside the blast furnace 10 may decrease, requiring heating of the reducing gas itself as heat compensation. In such cases, it becomes difficult to cool the reducing gas injection inlet 14 by the reducing gas. To help prevent the loss by melting of the metal or refractory material that defines the reducing gas injection inlet 14, a water-cooled structure around the reducing gas injection inlet 14 may be provided (within the tuyere walls, if the reducing gas injection inlet 14 is a tuyere).

[0038] The reducing gas injection inlet 14 can be connected to a reducing gas supply source provided on the outside of the blast furnace 10, by means of a reducing gas supply channel, for example. That is, the blast furnace 10 can be constructed so that the reducing gas is injected into the blast furnace 10 from a reducing gas supply source, through a reducing gas supply channel and a reducing gas injection inlet 14. There are no specific restrictions as to the shape of the reducing gas supply source or the reducing gas supply channel.

[0039] For this embodiment, it is important that the reducing gas injection inlet 14 be provided separately from the hot air tuyere 13. If the reducing gas injection inlet 14 is provided separately from the hot air tuyere 13, the diameter of the reducing gas injection inlet 14 can be increased independently of the shape and size of the hot air tuyere 13. This allows the flow velocity of the reducing gas to be controlled to remain below the speed of sound, even when a large quantity of reducing gas is injected through the reducing gas injection inlet 14. When a large quantity of reducing gas is expected to be injected into the blast furnace 10 through the reducing gas injection inlet 14, the diameter of the reducing gas injection inlet 14 (the equivalent diameter of the circle of the opening facing the interior of the blast furnace 10) can be from 30 mm to 400 mm Petition 870260063963, dated 06 / 29 / 2026, page 21 / 41 / 21 or from 60 mm to 100 mm, for example. Alternatively, the diameter of the reducing gas injection inlet 14 may be from 0.15% to 8% or from 0.5% to 3% of the diameter of the furnace belly 11b. The diameter of the reducing gas injection inlet 14 may be from 7.5% to 200% of the diameter of the hot air tuyere 13.

[0040] The number of reducing gas injection inlets 14 provided in blast furnace 10 is not particularly restricted. For example, the plurality of reducing gas injection inlets 14 can be arranged in the circumferential direction of the blast furnace. In other words, the plurality of reducing gas injection inlets 14 can be provided in the circumferential direction of blast furnace 10, viewed from above. Each of the central height positions Pi of the plurality of reducing gas injection inlets 14 can be the same. 1.3 Positional relationship between the hot air tuyere and the reducing gas injection inlet

[0041] For this embodiment, it is important that the central height position P1 of the reducing gas injection inlet 14 be equal to or lower than the central height position P2 of the hot air tuyere 13. Based on the new knowledge acquired by the present inventors, when the central height position P1 of the reducing gas injection inlet 14 is located above the central height position P2 of the hot air tuyere 13, the reducing gas injected through the reducing gas injection inlet 14 tends to rise along the faces of the blast furnace wall 10, resulting in a skewed flow of reducing gas inside the blast furnace 10.In contrast, when the central height position P1 of the reducing gas injection inlet 14 is equal to or lower than the central height position P2 of the hot air 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, with the reducing gas more easily reaching the center in the radial direction inside the blast furnace 10 (the furnace center). Petition 870260063963, dated 06 / 29 / 2026, page 22 / 41 / 21 As a result, the skewed flow of reducing gas within blast furnace 10 is suppressed and the utilization efficiency of the reducing gas is improved. The effect of suppressing the skewed flow of reducing gas is even more noticeable when the central height position Pi of the reducing gas injection inlet 14 is located below the central height position P2 of the hot air tuyere 13.

[0042] Figures 2A and B show cases where the central height P1 of a reducing gas injection inlet 14 is located lower than the central height P2 of a hot air tuyere 13. As shown in Figure 2A, the center of the reducing gas injection inlet 14 can be provided directly below the center of the hot air tuyere 13. That is, the location of the center of the reducing gas injection inlet 14 in the circumferential direction of the blast furnace 10 can be the same as the location of the center of the hot air tuyere 13. Alternatively, as shown in Figure 2B, the center of each reducing gas injection inlet 14 can be provided below, at an angle to, the center of each hot air tuyere 13. That is, the center of each reducing gas injection inlet 14 can be located at a different location from the center of each hot air tuyere 13 in the circumferential direction of the blast furnace 10. blast furnace 10.For example, when a plurality of hot air tuyeres 13 is provided in the circumferential direction of the blast furnace 10, the locations of the reducing gas injection inlets 14 in the circumferential direction of the blast furnace 10 may be between the plurality of hot air tuyeres 13. The present inventors have confirmed that when the positions of the central height P1 of the reducing gas injection inlets 14 are situated lower than the positions of the central height P2 of the hot air tuyeres 13, and the positions at the centers of the reducing gas injection inlets 14 in the circumferential direction of the blast furnace 10 are located between the centers of the plurality of hot air tuyeres 13, the effect of inhibiting the skewed flow of the reducing gas is further increased.

[0043] Figure 2C shows a case where the position of the central height. Petition 870260063963, dated 06 / 29 / 2026, page 23 / 41 / 21 Pi of a reducing gas injection inlet 14 is the same as the central height position P2 of a hot air tuyere 13. As shown in figure 2C, the reducing gas injection inlet 14 can be provided along the side of the hot air tuyere 13.

[0044] The length L between the central height position P1 of the reducing gas injection inlet 14 and the central height position P2 of the hot air tuyere 13 is 0 mm or greater. The length L can be from 0 mm to 3,000 mm, greater than 0 mm and up to 3,000 mm, or greater than 0 mm and up to 300 mm, for example. 1.4 Hot air

[0045] The hot air injected by the hot air tuyere 13 may consist of air or oxygen-enriched air, for example. The temperature of the hot air may be 1000°C or more, for example. The temperature of the hot air may vary from 1000°C to 2000°C, from 1000°C to 1700°C, from 1000°C to 1500°C or from 1000°C to 1300°C. The hot air flow velocity in the hot air tuyere 13 (hot air flow rate (m3 / s) / open area of ​​the hot air tuyere outlet 13 (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

[0046] The reducing gas injected through the reducing gas injection inlet 14 is a gas that functions as a reducing material within the blast furnace 10. Specifically, the term “reducing gas,” as used in this document, includes the concept of a gas that can generate reducing components by thermal decomposition within the blast furnace 10, even if it is a gas that does not function as a reducing material before being injected into the blast furnace 10. The relative density of the reducing gas is less than the relative density of the hot air injected into the blast furnace 10 through the hot air tuyere 13. Petition 870260063963, dated 06 / 29 / 2026, page 24 / 41 / 21 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 through the reducing gas injection inlet 14 can be from 0°C to 2000°C, or from 25°C to 1500°C, for example. As mentioned above, if the reducing gas injection inlet 14 is provided separately from the hot air vent 13 for this embodiment, it is possible to control the flow velocity of the reducing gas (reducing gas flow rate (m3 / s) / open area of ​​the reducing gas injection inlet outlet 14 (m2)) to below the speed of sound. That is, the flow velocity of the reducing gas at the reducing gas injection inlet 14 will be below the speed of sound. It is known that the "speed of sound" depends not only on the type of gas, but also on the temperature of the gas.The “speed of sound” can be determined by calculation according to the type and temperature of the gas injected into blast furnace 10. According to one embodiment, the flow velocity of the reducing gas can be the flow velocity V2 described below. 1.6 Hot Air Flow Velocity and Reducing Gas Flow Velocity

[0047] The flow velocity V1 of the hot air injected from the hot air 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 inlet 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 stable manner. 1.7 Other gases Petition 870260063963, dated 06 / 29 / 2026, page 25 / 41 / 21

[0048] Other gases may also be injected into the reducing gas injection inlet 14 along with the reducing gas. Examples of other gases include inert gases such as nitrogen gas. 2. Blast furnace

[0049] 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 shown in Figure 1, blast furnace 10, according to one embodiment, has: a hot air 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 inlet 14 provided below the lower end 11ax of the blast furnace shaft 10 and above the tap hole 12.

[0050] The reducing gas injected into blast furnace 10 through the reducing gas injection inlet 14 is a gas that functions as a reducing material within blast furnace 10.

[0051] The relative density of the reducing gas is less than the relative density of the hot air injected into blast furnace 10 through the hot air tuyere 13.

[0052] The reducing gas injection inlet 14 is provided separately from the hot air vent 13.

[0053] The central height position P1 of the reducing gas injection inlet 14 is the same as the central height position P2 of the hot air tuyere 13, or lower than that height position P2.

[0054] 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 Petition 870260063963, dated 06 / 29 / 2026, page 26 / 41 / 21 to be even larger. 3. Additional observations

[0055] 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 air tuyere 13, and reducing gas is injected into the blast furnace from an external reducing gas supply source of blast furnace 10, through the reducing gas flow path and the reducing gas injection inlet 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 through the reducing gas injection inlet 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 design, injecting reducing gas into blast furnace 10 through reducing gas injection inlet 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 can 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 injection gate in addition to the hot air tuyere 13 or reducing gas injection inlet 14 described above. Another reducing gas injection inlet may also be present above the hot air tuyere 13 in blast furnace 10. Aspects of the construction of blast furnace 10, other than the hot air tuyere 13 and reducing gas injection inlet 14, are public knowledge in the technical field and will not be described in detail here. 4. Effect

[0056] As explained above, according to this modality, it is Petition 870260063963, dated 06 / 29 / 2026, page 27 / 41 / 21 it is possible to control the flow rate of the reducing gas to below the speed of sound by injecting a reducing gas into blast furnace 10 through a reducing gas injection inlet 14 provided separately from the hot air tuyere 13. Furthermore, if the central height Pi of the reducing gas injection inlet 14 is equal to or lower than the central height P2 of the hot air tuyere 13, then it is possible to reduce the skewed flow of the reducing gas within blast furnace 10. EXAMPLES

[0057] 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. 1. Analysis of hydrogen gas flow rate

[0058] A simulation model was used to estimate the amount of hydrogen injection required per hydrogen gas injection inlet, where the reduction in carbon consumption per unit output was 30% or more in a blast furnace with an average hot metal output of 12,000 t / d, assuming a hydrogen injection temperature of 600°C. The hydrogen gas flow velocity was calculated from the estimated volume of hydrogen injection required and the diameter of the hydrogen gas injection inlet. A rating of “G” was assigned when the calculated flow velocity was less than the speed of sound in a hydrogen atmosphere, and a rating of “P” was assigned when it was equal to or greater than the speed of sound. The speed of sound in a hydrogen atmosphere at 600°C is approximately 1269 m / s. The calculation results are shown in Table 1 below. Petition 870260063963, dated 06 / 29 / 2026, page 28 / 41 / 21 [Table 11] Internal diameter (mm) H2 flow rate per injection inlet (m3 / h) 7500 8000 8500 9000 9500 Lance (Example of the Previous Technique) 25 Flow velocity (m / s) 2337 2492 2648 2804 2960 G or PPPPPP Tuyere (Examples) 60 Flow velocity (m / s) 406 433 460 487 514 G or PGGGGG 80 Flow velocity 228 243 259 274 289 G or PGGGGG

[0059] As can be clearly observed from the results in Table 1, injecting hydrogen gas at a flow velocity below the speed of sound is not possible with a conventional pass (a pass integrated with the hot air tuyere). In other words, a conventional pass limits the flow rate of hydrogen gas injected into the blast furnace, making it impossible to adequately reduce carbon consumption per unit output. In contrast, when hydrogen gas is injected through an injection inlet with a large internal diameter (for example, a reducing gas injection tuyere provided separately from the hot air tuyere), adjusting the internal diameter to 60 mm for 1 atmosphere and to 80 mm for furnace pressure allows hydrogen gas to be injected at a flow velocity below the speed of sound.An internal diameter of 60 mm or 80 mm does not differ significantly from the internal diameter of a hot air tuyere provided in a blast furnace and can be considered satisfactory for use in a blast furnace. Moreover, increasing the hydrogen temperature results in a higher speed of sound. That is, increasing the hydrogen temperature allows for the injection of hydrogen gas at a flow rate below the speed of sound, even when the injection inlet diameter has been reduced. However, it has been confirmed that, even with increased hydrogen temperature, it is difficult to control the hydrogen gas flow rate below the speed of sound when the injection inlet diameter is reduced to the size of the diameter of... Petition 870260063963, dated 06 / 29 / 2026, page 29 / 41 / 21 a conventional bid.

[0060] This suggests that the flow velocity of the reducing gas can be controlled to below the speed of sound by injecting a reducing gas into the blast furnace through a reducing gas injection inlet (e.g., a reducing gas injection tuyere) provided separately from the hot wind tuyere, rather than a span integrated with the hot wind tuyere. 2. Analysis of the location of the reducing gas injection.

[0061] A simulation model was used to alter the location where hydrogen gas was injected as the reducing gas, comparing the difference in hydrogen concentrations in the furnace wall, in the uppermost part of the blast furnace charge, and in the central section of the furnace. Specifically, the difference in hydrogen concentrations was determined for the following Prior Art Examples, Examples 1 to 4 and Comparative Examples 1 to 3.

[0062] Example of the Prior Technique: As illustrated in figure 3A, hot air was injected through a hot air tuyere, and hydrogen gas was injected through a lance integrated into the hot air tuyere.

[0063] Example 1: As shown in figure 3B, hot air was injected through a hot air tuyere, and hydrogen gas was injected through a reducing gas injection tuyere formed separately from the hot air tuyere, directly below the hot air tuyere.

[0064] Example 2: As shown in figure 3C, hot air was injected through the hot air tuyeres, and hydrogen gas was injected from a reducing gas injection tuyere, provided separately from the plurality of hot air tuyeres, below the lower end of the hot air tuyeres and between the hot air tuyeres situated around the circumference of the furnace.

[0065] Example 3: As shown in figure 3D, the hot air was Petition 870260063963, dated 06 / 29 / 2026, page 30 / 41 / 21 injected through the hot air tuyeres, and hydrogen gas was injected from a reducing gas injection tuyere, provided separately from the plurality of hot air tuyeres, at the same height as the lower ends of the hot air tuyeres and between the hot air tuyeres located around the circumference of the furnace.

[0066] Example 4: As shown in figure 3E, hot air was injected through the hot air tuyeres, and hydrogen gas was injected from a reducing gas injection tuyere, provided separately from the hot air tuyere particle, at the same height as the centers of the hot air tuyeres and between the hot air tuyeres situated around the circumference of the furnace.

[0067] Comparative Example 1: As shown in Figure 3F, hot air was injected through the hot air tuyeres, and hydrogen gas was injected from a reducing gas injection tuyere, provided separately from the plurality of hot air tuyeres, at the same height as the upper ends of the hot air tuyeres and between the hot air tuyeres situated around the circumference of the furnace.

[0068] Comparative Example 2: As shown in Figure 3G, hot air was injected through hot air tuyeres, and hydrogen gas was injected from a reducing gas injection tuyere provided separately from the plurality of hot air tuyeres, above the upper ends of the hot air tuyeres and between the hot air tuyeres situated around the circumference of the furnace.

[0069] Comparative Example 3: As shown in Figure 3H, hot air was injected through a hot air tuyere, and hydrogen gas was injected through a reducing gas injection tuyere formed separately from the hot air tuyere, directly above the hot air tuyere.

[0070] The results are shown in Table 2 below. Petition 870260063963, dated 06 / 29 / 2026, page 31 / 41 / 21 [Table 21] Example of the Previous Technique Example 1 Example 2 Example 3 Example 4 Ex. Comp. 1 Ex. Comp. 2 Ex. Comp. 3 Configuration Figure 3A Figure 3B Figure 3C Figure 3D Figure 3E Figure 3F Figure 3G Figure 3H Difference in hydrogen concentration [%] 2 2 2 2 3 8 9 9

[0071] As can be clearly observed from the results in Table 2, virtually no difference in hydrogen concentration was observed in the uppermost part of the blast furnace charge when hydrogen gas was injected through a conventional throw (a throw integrated with the hot air tuyere) (Prior Technique Example). This may be because the hydrogen gas and hot air were sufficiently mixed at the tuyere level, so that the hydrogen dispersed along with the hot air in the furnace.

[0072] When hydrogen gas was injected from the reducing gas injection tuyere, and the central height position of the reducing gas injection tuyere was above the central height position of the hot air tuyere, a significant difference in hydrogen concentration was observed in the center of the furnace and in the furnace wall sections at the uppermost extreme part of the blast furnace charge (Comparative Examples 1 to 3). This may be due to the fact that the relative density of hydrogen gas is less than the relative density of hot air, and that the hydrogen gas flowed preferentially along the sides of the furnace wall without being compressed by the hot air injected through the hot air tuyere.

[0073] In contrast, when hydrogen gas was injected through the reducing gas injection tuyere, virtually no difference in hydrogen concentration was observed in the uppermost part of the blast furnace charge when the central height position of the reducing gas injection tuyere was equal to or lower than the central height position of the hot wind tuyere (Examples 1 to 4). This may occur because the injected hydrogen gas Petition 870260063963, dated 06 / 29 / 2026, page 32 / 41 / 21 through the reducing gas injection tuyere was pressed against the hot air injected through the hot air tuyere, migrating to the center of the furnace below the level of the hot air tuyere, while rising along with the hot air.

[0074] This suggests that when a reducing gas is injected from a reducing gas injection inlet (e.g., a reducing gas injection tuyere) provided separately from the hot air tuyere, it is possible to suppress the skewed flow of the reducing gas within the blast furnace if the central height position P1 of the reducing gas injection inlet is the same as, or lower than, the central height position P2 of the hot air tuyere. 3. Summary

[0075] Summarizing these results, it can be concluded that the following method (1) and blast furnace (2) allow easy control of the flow rate of a reducing gas with low relative density when the reducing gas is injected into the blast furnace and can inhibit the biased flow of the reducing gas.

[0076] (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 air 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 inlet provided below the lower end of the blast furnace shaft and above the tap hole, wherein: Reducing gas is a gas that acts as a reducing agent inside the blast furnace; the relative density of the reducing gas is less than the relative density of the hot air; the reducing gas injection inlet is provided separately from the... Petition 870260063963, dated 06 / 29 / 2026, page 33 / 41 / 21 hot air vent, and the central height position Pi of the reducing gas injection inlet is equal to the central height position P2 of the hot air vent, or is less than that height position P2.

[0077] (2) A blast furnace having: a hot air tuyere provided below the lower end of the blast furnace shaft and above the tap hole, and a reducing gas injection inlet provided below the lower end of the blast furnace shaft and above the tap hole, wherein: The reducing gas injected into the blast furnace through the reducing gas injection inlet is gas that functions as a reducing material within the blast furnace; the relative density of the reducing gas is less than the relative density of the hot air injected into the blast furnace through the hot air tuyere; the reducing gas injection inlet is provided separately from the hot air tuyere; and the central height position P1 of the reducing gas injection inlet is equal to or less than the central height position P2 of the hot air tuyere. LIST OF REFERENCE SIGNS

[0078] 10 Blast furnace 11th Cuba 11b Oven belly 11c Bosch Racing hole Hot wind gust Reducing gas injection inlet Petition 870260063963, dated 06 / 29 / 2026, pages 34 / 41

Claims

1 / 2 CLAIMS 1. A method for injecting a reducing gas into a blast furnace, the method characterized in that it comprises: injecting hot air into the blast furnace from a hot air 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 inlet provided below the lower end of the blast furnace shaft and above the tap hole, wherein: 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 the relative density of the hot air, the reducing gas injection inlet is provided separately from the hot air tuyer, and the position of the central height P1 of the reducing gas injection inlet is equal to the position of the central height P2 of the hot air tuyer, or is less than that position of height P2.

2. A method for injecting a reducing gas into a blast furnace according to claim 1, characterized in that the position of height P1 is lower than the position of height 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 air tuyere provided below the lower end of the blast furnace shaft and above the tap hole, and a reducing gas injection inlet provided below the lower end of the blast furnace shaft and above the tap hole, wherein: Petition 870260063963, dated 06 / 29 / 2026, page. 35 / 41 2 / 2 The reducing gas injected into the blast furnace through the reducing gas injection inlet is gas that functions as a reducing material inside the blast furnace; the relative density of the reducing gas is less than the relative density of the hot air injected into the blast furnace through the hot air tuyere; the reducing gas injection inlet is provided separately from the hot air tuyere; and the central height Pi of the reducing gas injection inlet is equal to or less than the central height P2 of the hot air tuyere.

5. Blast furnace according to claim 4, characterized in that the position of height P1 is lower than the position of height P2.

6. Blast furnace according to claim 4 or 5, characterized in that the reducing gas comprises hydrogen gas. Petition 870260063963, dated 06 / 29 / 2026, pp. 36 / 41

Images