Method for blowing reducing gas into blast furnace, and blast furnace

Abstract

The present invention discloses a method with which it is possible to easily control the flow rate of a reducing gas and to minimize drift of the reducing gas in cases where the reducing gas that has a small specific gravity is blown into the inside of a blast furnace. A method according to the present disclosure is a method for blowing a reducing gas into a blast furnace, the method comprising: blowing hot air into the inside of a blast furnace from a hot air tuyere which is provided below the lower end of the shaft of the blast furnace and above the taphole; and blowing a reducing gas into the inside of the blast furnace from a reducing gas blowing port which is provided below the lower end of the shaft of the blast furnace and above the taphole. Here, the reducing gas functions as a reducing material inside the blast furnace, and the specific gravity of the reducing gas is smaller than the specific gravity of the hot air. The reducing gas blowing port is provided separately from the hot air tuyere, and the height position P1 of the center of the reducing gas blowing port is the same as the height position P2 of the center of the hot air tuyere or is located below the height position P2.

Description

Method for injecting reducing gas into blast furnace and blast furnace

[0001] The present application discloses a method for injecting reducing gas into a blast furnace and a blast furnace.

[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 injecting reducing gas into a blast furnace, Patent Document 1 discloses a method in which a lance for injecting reducing gas is disposed in a flow path of a hot blast tuyere, and reducing gas is injected through the lance and the tuyere. 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] As disclosed in Patent Document 1, when a lance is disposed inside a hot blast tuyere, the lance diameter needs to be reduced depending on the shape and size of the hot blast tuyere. Therefore, when a large amount of reducing gas is injected through a lance disposed inside the hot blast tuyere, the flow velocity of the reducing gas exceeds the sonic velocity. In this regard, the conventional technology leaves room for improvement in controlling the flow velocity of the reducing gas. Furthermore, when a reducing gas with a low specific gravity is injected into a blast furnace, the reducing gas tends to rise along the wall surface of the blast furnace, resulting in uneven flow of the reducing gas. The conventional technology has not adequately considered the uneven flow of the reducing gas inside the blast furnace. In view of the above, the present application discloses a technology that can easily control the flow velocity of the reducing gas and suppress uneven flow of the reducing gas when a reducing gas with a low specific gravity is injected into the blast furnace.

[0005] The present application discloses the following multiple aspects as means for solving the above problems. <Aspect 1> A method for injecting reducing gas into a blast furnace, comprising: injecting hot air into the interior of the blast furnace from a hot air tuyere provided below the lower end of the shaft of the blast furnace and above the tap hole; and injecting reducing gas into the interior of the blast furnace from a reducing gas inlet provided below the lower end of the shaft of the blast furnace and above the tap hole, wherein the reducing gas is a gas that functions as a reducing agent inside the blast furnace, the specific gravity of the reducing gas is smaller than the specific gravity of the hot air, the reducing gas inlet is provided separately from the hot air tuyere, and a height position P of the center of the reducing gas inlet is １ The height position P of the center of the hot air tuyere ２ or the height position P ２ The method for injecting reducing gas into a blast furnace according to the first aspect, wherein the reducing gas is present below the height position P １ However, the height position P ２ a reducing gas supply port provided in the blast furnace, the reducing gas being located below a lower end of the shaft of the blast furnace and above a tap hole; ... １ The height position P of the center of the hot air tuyere ２ or the height position P ２ The blast furnace of aspect 4, wherein the height position P １ However, the height position P ２Aspect 6 The blast furnace according to Aspect 4 or 5, wherein the reducing gas includes hydrogen gas.

[0006] According to the technology of the present disclosure, when a reducing gas with a low specific gravity is injected into the inside of a blast furnace, it is possible to control the flow rate of the reducing gas and to suppress uneven flow of the reducing gas.

[0007] 1 is a schematic diagram of a blast furnace. Some components of the blast furnace are omitted from the drawing.

[0023] FIG. 1 is a schematic diagram of an example of the positional relationship between hot blast tuyere and reducing gas inlet in a blast furnace.

[0024] FIG. 1 is a schematic diagram of an example of the positional relationship between hot blast tuyere and reducing gas inlet in a blast furnace.

[0025] FIG. 1 is a schematic diagram of an example of the positional relationship between hot blast tuyere and reducing gas inlet in a blast furnace.

[0026] FIG. 1 is a schematic diagram of an example of the positional relationship between hot blast tuyere and reducing gas inlet in a blast furnace.

[0027] FIG. 1 is a schematic diagram of an example of the positional relationship between hot blast tuyere and reducing gas inlet in a blast furnace.

[0028] FIG. 1 is a schematic diagram of an example of the positional relationship between hot blast tuyere and reducing gas inlet in a prior art example.

[0029] FIG. 1 is a schematic diagram of an example of the positional relationship between hot blast tuyere and reducing gas inlet in Example 1.

[0029] FIG. 1 is a schematic diagram of an example of the positional relationship between hot blast tuyere and reducing gas inlet in Example 2.

[0029] FIG. 1 is a schematic diagram of an example of the positional relationship between hot blast tuyere and reducing gas inlet in Example 3.

[0029] FIG. 1 is a schematic diagram of an example of the positional relationship between hot blast tuyere and reducing gas inlet in Example 4.

[0029] FIG. 1 is a schematic diagram of an example of the positional relationship between hot blast tuyere and reducing gas inlet in Comparative Example 1.

[0029] FIG. 1 is a schematic diagram of an example of the positional relationship between hot blast tuyere and reducing gas inlet in Comparative Example 10 is a schematic diagram showing the positional relationship between the hot blast tuyere and the reducing gas injection tuyere in Comparative Example 3.

[0008] Hereinafter, an embodiment of the method for injecting a reducing gas into a blast furnace and the blast furnace according to the present disclosure will be described. However, the method for injecting a reducing gas into a blast furnace and the blast furnace according to the present disclosure are not limited to the following embodiment.

[0009] 1. Method of Injecting Reducing Gas into a Blast Furnace As shown in FIG. 1 , a method of injecting reducing gas into a blast furnace 10 according to one embodiment includes: injecting hot air into the interior of the blast furnace 10 from a hot air tuyere 13 provided below the shaft lower end 11ax of the blast furnace 10 and above the tap hole 12; and injecting reducing gas into the interior of the blast furnace 10 from a reducing gas injection port 14 provided below the shaft lower end 11ax of the blast furnace 10 and above the tap hole 12. The reducing gas is a gas that functions as a reducing agent inside the blast furnace 10. The specific gravity of the reducing gas is smaller than the specific gravity of the hot air. The reducing gas injection port 14 is provided separately from the hot air tuyere 13. The height position P of the center of the reducing gas injection port 14 is １ is the height position P of the center of the hot air tuyere 13 ２ or the height position P ２ It exists below.

[0010] 1.1 Hot Blast Tuyere The blast furnace 10 has a hot blast tuyere 13 below the shaft lower end 11ax and above the tap hole 12. The "shaft lower end" refers to the boundary between the shaft 11a and the belly 11b. The "shaft" refers to the portion above the belly 11b, where the furnace diameter typically increases from top to bottom. The "belly" refers to the portion below the shaft and above the bosch 11c, where the furnace diameter typically is greatest. The furnace diameter (diameter) of the belly 11b 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 hole provided at the bottom of the blast furnace 10. The "hot blast tuyere" refers to a nozzle for blowing hot air into the blast furnace. The blast furnace 10 may have a hot air tuyere 13 below the belly lower end 11bx and above the tap hole 12, or may have a hot air tuyere 13 below the morning glory lower end 11cx and above the tap hole 12.

[0011] The configuration of the hot air tuyere 13 is known. For example, the hot air tuyere 13 may have a water-cooled structure. The hot air tuyere 13 may be connected to a hot air stove outside the blast furnace 10 via a hot air pipe or the like. In other words, the blast furnace 10 may be configured so that hot air is blown into the interior of the blast furnace 10 from the hot air stove via the hot air pipe and the hot air tuyere 13. The diameter of the hot air tuyere 13 (the circle-equivalent diameter of the opening facing the interior of the blast furnace 10, 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.

[0012] The number of hot air tuyere 13 provided in the blast furnace 10 is not particularly limited, and can be determined depending on the internal volume of the blast furnace. In the blast furnace 10, a plurality of hot air tuyere 13 can be arranged in the circumferential direction of the blast furnace 10. In other words, in the blast furnace 10, a plurality of hot air tuyere 13 can be arranged in the circumferential direction when viewed from above. Usually, the height position P of the center of each of the plurality of hot air tuyere 13 is ２ is similar.

[0013] 1.2 Reducing Gas Inlet The blast furnace 10 has a reducing gas inlet 14 below the shaft lower end 11ax and above the taphole 12. This allows the reduction reaction to proceed efficiently inside the blast furnace 10. Furthermore, when the reducing gas inlet 14 is provided below the shaft lower end 11ax and above the taphole 12, near the hot air tuyere in the height direction of the furnace, the reducing gas inlet 14 is less likely to interfere with the discharge of molten iron and slag.

[0014] There is no particular limitation on the shape of the reducing gas inlet 14. The reducing gas inlet 14 may be, for example, a tuyere (nozzle). The reducing gas inlet 14 may be defined by a metal (for example, copper) or a refractory material.

[0015] In the blast furnace 10, there is a possibility that molten iron or slag may drip into the reducing gas inlet 14. Furthermore, when hydrogen gas is injected as the reducing gas through the reducing gas inlet 14 and the input of carbonaceous material is reduced, the amount of heat inside the blast furnace 10 decreases, and the reducing gas itself may be heated to compensate for the heat. In this case, it is difficult to cool the reducing gas inlet 14 using the reducing gas. In this regard, in order to suppress melting or the like of the metal or refractory material that defines the reducing gas inlet 14, a water-cooling structure may be provided around the reducing gas inlet 14 (in the wall surface of the tuyere if the reducing gas inlet 14 is a tuyere).

[0016] The reducing gas injection port 14 can be connected to a reducing gas supply source outside the blast furnace 10 via a reducing gas supply passage or the like. In other words, the blast furnace 10 can be configured so that reducing gas is injected into the blast furnace 10 from the reducing gas supply source via the reducing gas supply passage and the reducing gas injection port 14. There are no particular limitations on the configuration of the reducing gas supply source or the reducing gas supply passage.

[0017] In this embodiment, it is important that the reducing gas inlet 14 is provided separately from the hot air tuyere 13. When the reducing gas inlet 14 is provided separately from the hot air tuyere 13, the diameter of the reducing gas inlet 14 can be increased regardless of the shape or size of the hot air tuyere 13. This allows the flow velocity of the reducing gas to be controlled to less than the sonic velocity even when a large amount of reducing gas is injected through the reducing gas inlet 14. When it is assumed that a large amount of reducing gas is injected into the interior of the blast furnace 10 through the reducing gas inlet 14, the diameter of the reducing gas inlet 14 (the circle-equivalent diameter of the opening facing the interior of the blast furnace 10) may be, for example, 30 mm to 400 mm, or 60 mm to 100 mm. Alternatively, the diameter of the reducing gas inlet 14 may be 0.15% to 8% or 0.5% to 3% of the diameter of the furnace belly 11b. Alternatively, the diameter of the reducing gas inlet 14 may be 7.5% or more and 200% or less of the diameter of the hot air tuyere 13 .

[0018] The number of reducing gas inlets 14 provided in the blast furnace 10 is not particularly limited. For example, a plurality of reducing gas inlets 14 may be arranged in the circumferential direction of the blast furnace. In other words, in the blast furnace 10, a plurality of reducing gas inlets 14 may be arranged in the circumferential direction when viewed from above. The height position P of the center of each of the plurality of reducing gas inlets 14 １ may be the same as each other.

[0019] 1.3 Positional relationship between the hot air tuyere and the reducing gas inlet In this embodiment, the height position P of the center of the reducing gas inlet 14 １ is the height position P of the center of the hot air tuyere 13 ２ or at the height position P ２ According to the new findings of the present inventors, it is important that the center of the reducing gas blowing port 14 is located below the height position P １ is the height position P of the center of the hot air tuyere 13 ２ If the height position P of the center of the reducing gas blowing port 14 is higher than the height position P of the center of the reducing gas blowing port 14, the reducing gas blown through the reducing gas blowing port 14 will tend to rise along the wall surface of the blast furnace 10, and the reducing gas will tend to flow unevenly inside the blast furnace 10. １ is the height position P of the center of the hot air tuyere 13 ２ or at the height position P ２ When the reducing gas inlet 14 is located below the height position P １ The height position P of the center of the hot air tuyere 13 ２ When the gas supply passage is located below the pressure vessel, the effect of suppressing the uneven flow of the reducing gas becomes more remarkable.

[0020] 2A and 2B, the height position P １ is the height position P of the center of the hot air tuyere 13 ２2A , the center of the reducing gas injection port 14 may be located directly below the center of the hot air tuyere 13. That is, the position of the center of the reducing gas injection port 14 in the circumferential direction of the blast furnace 10 may be the same as the position of the center of the hot air tuyere 13. Furthermore, as shown in FIG. 2B , the center of the reducing gas injection port 14 may be located obliquely below the center of the hot air tuyere 13. That is, the center of the reducing gas injection port 14 may be located at a position different from the center of the hot air tuyere 13 in the circumferential direction of the blast furnace 10. For example, when a plurality of hot air tuyere 13 are provided in the circumferential direction of the blast furnace 10, the position of the reducing gas injection port 14 in the circumferential direction of the blast furnace 10 may be located between the plurality of hot air tuyere 13. As far as the inventors have confirmed, the height position P １ is the height position P of the center of the hot air tuyere 13 ２ When the center of the reducing gas inlet 14 in the circumferential direction of the blast furnace 10 is located below the center of the hot air tuyere 13, and the center of the reducing gas inlet 14 is located between the centers of the multiple hot air tuyere 13, the effect of suppressing the uneven flow of the reducing gas is further enhanced.

[0021] 2C, the height position P １ is the height position P of the center of the hot air tuyere 13 ２ 2C, the reducing gas inlet 14 may be provided beside the hot air tuyere 13.

[0022] The height position P of the center of the reducing gas inlet 14 １ and the height position P of the center of the hot air tuyere 13 ２ The length L between the first and second electrodes is 0 mm or more. The length L may be, for example, 0 mm or more and 3000 mm or less, more than 0 mm and 3000 mm or less, or more than 0 mm and 300 mm or less.

[0023] 1.4 Hot Air The hot air blown from the hot air tuyere 13 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 hot air tuyere 13 (flow rate of the hot air (m ３ / s) / opening area of ​​the hot air tuyere 13 outlet (m ２ ) may be adjusted depending on the operation status of the blast furnace 10. In one embodiment, the flow velocity of the hot air may be a flow velocity V1 described later.

[0024] 1.5 Reducing Gas The reducing gas injected through the reducing gas inlet 14 functions as a reducing agent inside the blast furnace 10. In other words, even if a gas does not function as a reducing agent before being injected into the blast furnace 10, the term "reducing gas" as used herein is included as long as it can generate reducing components by thermal decomposition or the like inside the blast furnace 10. Furthermore, the specific gravity of the reducing gas is lower than the specific gravity of the hot air injected into the blast furnace 10 through the hot air tuyere 13. Examples of such reducing gas include at least one selected from hydrogen gas, hydrocarbon gas (e.g., methane gas), carbon monoxide gas, and ammonia gas. In particular, when the reducing gas contains hydrogen gas, the technology disclosed herein can be expected to exhibit even greater effects. The temperature of the reducing gas injected through the reducing gas inlet 14 may be, for example, 0°C or higher and 2000°C or lower, or 25°C or higher and 1500°C or lower. As described above, in this embodiment, the reducing gas inlet 14 is provided separately from the hot air tuyere 13, so that the flow rate of the reducing gas (flow rate of the reducing gas (m ３ / s) / opening area of ​​the outlet of the reducing gas inlet 14 (m ２ ) can be controlled to be less than the sonic velocity. That is, the flow velocity of the reducing gas at the reducing gas injection port 14 is less than the sonic velocity. It is known that the "sonic velocity" depends not only on the type of gas but also on the temperature of the gas. The "sonic velocity" can be determined by calculation or the like depending on the type and temperature of the gas injected into the blast furnace 10. In one embodiment, the flow velocity of the reducing gas may be a flow velocity V2 described below.

[0025] 1.6 Hot Air Flow Velocity and Reducing Gas Flow Velocity The flow velocity V1 of the hot air blown from the hot air tuyere 13 is not particularly limited, but for example, if the flow velocity V1 is 100 m / s or more and 1000 m / s or less, and particularly 200 m / s or more and 400 m / s or less, it is more likely to suppress uneven flow of the reducing gas inside the blast furnace 10. Furthermore, the flow velocity V2 of the reducing gas blown from the reducing gas inlet 14 is not particularly limited, but for example, if the flow velocity V2 is 100 m / s or more and 1000 m / s or less, and particularly 200 m / s or more and 800 m / s or less, ventilation inside the blast furnace 10 is stable, resulting in operation in which the reduction reaction inside the furnace proceeds stably.

[0026] 1.7 Other Gases Other gases may be blown in together with the reducing gas through the reducing gas blowing port 14. Examples of other gases include inert gases such as nitrogen gas.

[0027] 2. Blast Furnace The technology disclosed herein has aspects as a method for injecting reducing gas into a blast furnace, as well as aspects as a blast furnace itself. That is, as shown in FIG. 1 , a blast furnace 10 according to one embodiment has: a hot blast tuyere 13 provided below the shaft lower end 11ax of the blast furnace 10 and above the tap hole 12; and a reducing gas inlet 14 provided below the shaft lower end 11ax of the blast furnace 10 and above the tap hole 12. The reducing gas injected into the blast furnace 10 from the reducing gas inlet 14 is a gas that functions as a reducing agent inside the blast furnace 10. The specific gravity of the reducing gas is smaller than the specific gravity of the hot air blown into the blast furnace 10 from the hot blast tuyere 13. The reducing gas inlet 14 is provided separately from the hot blast tuyere 13. The height position P of the center of the reducing gas inlet 14 is １ is the height position P of the center of the hot air tuyere 13 ２ or the height position P ２ It exists below.

[0028] As described above, in the blast furnace 10, the height position P １ However, the height position P ２It is believed that the effect of suppressing the uneven flow of the reducing gas is further enhanced when the reducing gas is located below the pressure drop. Furthermore, it is believed that the effect of the technology of the present disclosure is further enhanced when the reducing gas contains hydrogen gas.

[0029] 3. Supplementary Information In the operation of the blast furnace 10, for example, iron ore (iron oxide), coke, etc. are charged into the blast furnace 10 from the top thereof. Meanwhile, hot air is blown into the blast furnace 10 from a hot stove outside the blast furnace 10 via a hot blast pipe and hot blast tuyere 13. Furthermore, reducing gas is blown into the blast furnace 10 from a reducing gas supply source outside the blast furnace 10 via a reducing gas flow path and a reducing gas inlet 14. The coke, etc. supplied into the blast furnace 10 is combusted to generate reducing gas. The reducing gas generated by the combustion of the coke, etc., and the reducing gas blown through the reducing gas inlet 14 reduce and dissolve iron oxide to obtain molten pig iron. The molten pig iron is tapped from a tap hole 12 provided at the bottom of the blast furnace 10. In this embodiment, blowing reducing gas into the blast furnace 10 through the reducing gas inlet 14 allows the amount of carbon-containing reducing material, such as coke, to be reduced accordingly. As a result, CO ２ The amount of generated iron can be reduced. The blast furnace 10 can have various configurations as long as it is capable of producing pig iron as described above. For example, the blast furnace 10 may have other tuyere(s) and / or nozzle(s) in addition to the above-described hot blast tuyere(s) 13 and reducing gas nozzle(s) 14. Furthermore, in the blast furnace 10, other reducing gas nozzle(s) may be present above the hot blast tuyere(s) 13. The configuration of the blast furnace 10 other than the hot blast tuyere(s) 13 and reducing gas nozzle(s) 14 is known in the art, and therefore will not be described in detail here.

[0030] 4. Effects As described above, according to this embodiment, the flow velocity of the reducing gas can be controlled to be less than the sonic velocity by injecting the reducing gas into the blast furnace 10 through the reducing gas injection port 14 provided separately from the hot blast tuyere 13. １ The height position P of the center of the hot air tuyere 13 ２ or at the height position P ２By being located below this, it is possible to suppress uneven flow of the reducing gas inside the blast furnace 10.

[0031] The present invention will be further described below with reference to examples, but the present invention is not limited to the following examples. The present invention allows various conditions to be adopted as long as the object is achieved without departing from the gist of the present invention. In the following examples, hydrogen gas is used as the reducing gas, but the type of reducing gas is not limited to this.

[0032] 1. Study on hydrogen gas flow velocity Using a simulation model, the required hydrogen injection amount per hydrogen gas injection port for a blast furnace with an average production rate of 12,000 t / d, when the reduction rate of carbon consumption per unit of production is 30% or more, was estimated, assuming a hydrogen injection temperature of 600°C. The hydrogen gas flow velocity was calculated from the estimated required hydrogen injection amount and the diameter of the hydrogen gas injection port. If the calculated flow velocity was slower than the sonic velocity in a hydrogen atmosphere, it was evaluated as "○", and if it was equal to or greater than the sonic velocity, it was evaluated as "×". The sonic velocity in a hydrogen atmosphere at 600°C is approximately 1,269 m / s. The calculation results are shown in Table 1 below.

[0033]

[0034] As is clear from the results shown in Table 1, conventional lances (lances built into hot blast tuyere) cannot inject hydrogen gas at subsonic flow rates. In other words, conventional lances are limited in the flow rate of hydrogen gas injected into a blast furnace, making it impossible to sufficiently reduce carbon consumption. In contrast, when hydrogen gas is injected through a large-diameter inlet (e.g., a reducing gas inlet provided separately from the hot blast tuyere), an inner diameter of 60 mm at 1 atmosphere and an inner diameter of 80 mm at furnace pressure can inject hydrogen gas at subsonic flow rates. Inner diameters of 60 mm and 80 mm are not significantly different from the inner diameters of hot blast tuyere s installed in blast furnaces and can be used in blast furnaces without any problems. Furthermore, increasing the hydrogen temperature increases the velocity at which the sonic velocity is reached. In other words, increasing the hydrogen temperature allows hydrogen gas to be injected at subsonic flow rates even when the inlet diameter is reduced. However, it was confirmed that even if the temperature of the hydrogen is increased, if the diameter of the injection port is reduced to the conventional lance diameter, it becomes difficult to control the flow rate of the hydrogen gas to a speed below the speed of sound.

[0035] From the above, it can be said that by injecting reducing gas into the inside of a blast furnace through a reducing gas inlet (for example, a reducing gas injection tuyere) provided separately from the hot blast tuyere, rather than through a lance built into the hot blast tuyere, the flow velocity of the reducing gas can be controlled to less than the speed of sound.

[0036] 2. Study of the position where reducing gas is injected Using a simulation model, the position where hydrogen gas as a reducing gas is injected was changed, and the difference in hydrogen concentration between the furnace wall at the top surface of the contents inside the blast furnace and the center of the furnace was compared. Specifically, the hydrogen concentration difference was determined for each of the following prior art example, Examples 1 to 4, and Comparative Examples 1 to 3.

[0037] Prior example: As shown in FIG. 3A, hot air was blown in from a hot air tuyere, and hydrogen gas was blown in from a lance built in the hot air tuyere.

[0038] Example 1: As shown in FIG. 3B, hot air was blown in from a hot air tuyere, and hydrogen gas was blown in from a reducing gas blowing tuyere provided separately from the hot air tuyere immediately below the hot air tuyere.

[0039] Example 2: As shown in Figure 3C, hot air was blown in from the hot air tuyere, and hydrogen gas was blown in from a reducing gas blowing tuyere that was provided separately from the hot air tuyere and located between multiple hot air tuyere circumferentially of the furnace and below the lower ends of the hot air tuyere.

[0040] Example 3: As shown in Figure 3D, hot air was blown in from the hot air tuyere, and hydrogen gas was blown in from a reducing gas blowing tuyere that was provided separately from the hot air tuyere and located between multiple hot air tuyere circumferentially of the furnace and at the same height as the lower ends of the hot air tuyere.

[0041] Example 4: As shown in Figure 3E, hot air was blown in from the hot air tuyere, and hydrogen gas was blown in from a reducing gas blowing tuyere that was provided separately from the hot air tuyere and located between multiple hot air tuyere circumferentially of the furnace and at the same height as the center of the hot air tuyere.

[0042] Comparative Example 1: As shown in Figure 3F, hot air was blown in from the hot air tuyere, and hydrogen gas was blown in from a reducing gas blowing tuyere that was installed separately from the hot air tuyere and located between multiple hot air tuyere circumferentially of the furnace and at the same height as the upper ends of the hot air tuyere.

[0043] Comparative Example 2: As shown in Figure 3G, hot air was blown in from the hot air tuyere, and hydrogen gas was blown in from a reducing gas blowing tuyere that was provided separately from the hot air tuyere and located between multiple hot air tuyere circumferentially of the furnace and above the upper ends of the hot air tuyere.

[0044] Comparative Example 3: As shown in FIG. 3H, hot air was blown in from the hot air tuyere, and hydrogen gas was blown in from a reducing gas blowing tuyere provided separately from and directly above the hot air tuyere.

[0045] The results are shown in Table 2 below.

[0046]

[0047] As is clear from the results shown in Table 2, when hydrogen gas was injected through a conventional lance (a lance built into the hot blast tuyere), almost no difference in hydrogen concentration was observed at the top of the blast furnace load (prior example). This is thought to be because the hydrogen gas and hot blast were sufficiently mixed at the tuyere level, and the hydrogen was dispersed along with the hot blast inside the furnace.

[0048] Furthermore, when hydrogen gas was blown in through the reducing gas blowing tuyere, and the height position of the center of the reducing gas blowing tuyere was higher than the height position of the center of the hot blast tuyere, a large difference in hydrogen concentration was observed between the furnace center and the furnace wall at the top surface of the contents inside the blast furnace (Comparative Examples 1 to 3). This is thought to be because the specific gravity of hydrogen gas is smaller than the specific gravity of hot blast, and the hydrogen gas was not pushed by the hot blast blown in from the hot blast tuyere, and so the hydrogen gas flowed preferentially along the wall side of the furnace.

[0049] In contrast, when hydrogen gas was blown through the reducing gas blowing tuyere, if the height position of the center of the reducing gas blowing tuyere was the same as or lower than the height position of the center of the hot blast tuyere, almost no difference in hydrogen concentration was observed at the top surface of the contents inside the blast furnace (Examples 1 to 4). This is thought to be because the hydrogen gas blown through the reducing gas blowing tuyere was pushed by the hot blast blown through the hot blast tuyere, moved below the hot blast tuyere level toward the center of the furnace, and then rose together with the hot blast.

[0050] From the above, when the reducing gas is blown from a reducing gas blowing port (for example, a reducing gas blowing port) provided separately from the hot air blowing port, the height position P １ is the height position P of the center of the hot air tuyere ２ or at the height position P ２ It can be said that by being located below the pressure vessel, it is possible to suppress uneven flow of reducing gas inside the blast furnace.

[0051] 3. Summary In summary of the above results, it can be said that, according to the following method (1) and blast furnace (2), when a reducing gas with a low specific gravity is injected into the inside of a blast furnace, the flow rate of the reducing gas can be easily controlled and uneven flow of the reducing gas can be suppressed.

[0052] (1) A method of injecting reducing gas into a blast furnace, comprising: injecting hot air into the interior of the blast furnace from a hot air tuyere provided below the lower end of the shaft of the blast furnace and above the tap hole; and injecting reducing gas into the interior of the blast furnace from a reducing gas inlet provided below the lower end of the shaft of the blast furnace and above the tap hole, wherein the reducing gas is a gas that functions as a reducing agent inside the blast furnace, the specific gravity of the reducing gas is smaller than the specific gravity of the hot air, the reducing gas inlet is provided separately from the hot air tuyere, and a height position P of the center of the reducing gas inlet is １ The height position P of the center of the hot air tuyere ２ or the height position P ２ A method of injecting reducing gas into a blast furnace located below the

[0053] (2) A blast furnace, comprising: a hot blast tuyere provided below the shaft lower end of the blast furnace and above the tap hole; and a reducing gas inlet provided below the shaft lower end of the blast furnace and above the tap hole, wherein the reducing gas blown into the blast furnace from the reducing gas inlet is a gas that functions as a reducing agent inside the blast furnace, the specific gravity of the reducing gas is smaller than the specific gravity of the hot air blown into the blast furnace from the hot blast tuyere, the reducing gas inlet is provided separately from the hot blast tuyere, and the height position P of the center of the reducing gas inlet is １ The height position P of the center of the hot air tuyere ２ or the height position P ２ A blast furnace located below.

[0054] 10 Blast furnace 11a Shaft 11b Belly 11c Bosch 12 Taphole 13 Hot blast tuyere 14 Reducing gas inlet

Claims

1. A method of injecting reducing gas into a blast furnace, comprising: injecting hot air into the interior of the blast furnace from a hot air tuyere provided below the lower end of the shaft of the blast furnace and above the tap hole; and injecting reducing gas into the interior of the blast furnace from a reducing gas inlet provided below the lower end of the shaft of the blast furnace and above the tap hole, wherein the reducing gas is a gas that functions as a reducing agent inside the blast furnace, the specific gravity of the reducing gas is smaller than the specific gravity of the hot air, the reducing gas inlet is provided separately from the hot air tuyere, and a height position P of the center of the reducing gas inlet is １ The height position P of the center of the hot air tuyere ２ or the height position P ２ A method of injecting reducing gas into a blast furnace located below the 2. The method for injecting reducing gas into a blast furnace according to claim 1, wherein the height position P １ However, the height position P ２ A method of injecting reducing gas into a blast furnace located below the 3. A method for injecting a reducing gas into a blast furnace according to claim 1 or 2, wherein the reducing gas contains hydrogen gas.

4. A blast furnace, comprising: a hot blast tuyere provided below the lower end of the shaft of the blast furnace and above the tap hole; and a reducing gas inlet provided below the lower end of the shaft of the blast furnace and above the tap hole, wherein the reducing gas blown into the interior of the blast furnace from the reducing gas inlet is a gas that functions as a reducing agent inside the blast furnace, the specific gravity of the reducing gas is smaller than the specific gravity of the hot air blown into the interior of the blast furnace from the hot blast tuyere, the reducing gas inlet is provided separately from the hot blast tuyere, and the height position P of the center of the reducing gas inlet is １ The height position P of the center of the hot air tuyere ２ or the height position P ２ A blast furnace located below.

5. A blast furnace according to claim 4, wherein the height position P １ However, the height position P ２ A blast furnace located below.

6. A blast furnace according to claim 4 or 5, wherein the reducing gas contains hydrogen gas.

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