Method for injecting reducing gas into a 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

Technical Field

[0001] This application discloses a method for blowing reducing gas into a blast furnace and a blast furnace.

Background Art

[0002] In the ironmaking process, reduction of CO2 emissions has been under consideration. For example, when producing pig iron in a blast furnace, it may be possible to use a reducing gas such as hydrogen gas in place of a part of coke or the like as a reducing material. As a method for blowing reducing gas into a blast furnace, Patent Document 1 discloses a method of arranging a lance for blowing reducing gas in the flow path of a hot blast tuyere and blowing the reducing gas through the lance and the tuyere. Incidentally, although not assuming blowing of reducing gas, Patent Document 2 discloses a method of inserting a fuel injection lance into the wall surface of a hot blast tuyere and blowing pulverized coal as fuel into the blast furnace through the fuel injection lance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] As disclosed in Patent Document 1, when a lance is placed inside a hot air tuyer, the diameter of the lance needs to be reduced depending on the shape and size of the hot air tuyer. Therefore, when attempting to blow a large amount of reducing gas through a lance placed inside a hot air tuyer, the flow velocity of the reducing gas exceeds the speed of sound. In this respect, there is room for improvement in the conventional technology regarding the control of the flow velocity of the reducing gas. Furthermore, when a reducing gas with a low specific gravity is blown into a blast furnace, the reducing gas tends to rise along the walls of the blast furnace, causing uneven flow of the reducing gas. In the conventional technology, sufficient consideration has not been given to the uneven flow of reducing gas inside a blast furnace. From these viewpoints, this application discloses a technology that allows for easy control of the flow velocity of the reducing gas and suppression of uneven flow of the reducing gas when a reducing gas with a low specific gravity is blown into the interior of a blast furnace. [Means for solving the problem]

[0005] This application discloses several embodiments as means for solving the above-mentioned problems. <Aspect 1> A method for injecting reducing gas into a blast furnace, Hot air is blown into the interior of the blast furnace from a hot air tuyeres located below the lower end of the blast furnace shaft and above the taphole, This includes injecting reducing gas into the interior of the blast furnace from a reducing gas injection port located below the lower end of the blast furnace shaft and above the taphole, The reducing gas is a gas that functions as a reducing agent inside the blast furnace. The specific gravity of the reducing gas is less than the specific gravity of the hot air. The aforementioned reducing gas inlet is provided separately from the aforementioned hot air vent, The height position P1 at the center of the reducing gas inlet is the same as the height position P2 at the center of the hot air tuyere, or is located below the height position P2. Method for injecting reducing gas into a blast furnace. <Aspect 2> A method for injecting reducing gas into a blast furnace according to Embodiment 1, The aforementioned height position P1 is located below the aforementioned height position P2. Method for injecting reducing gas into a blast furnace. <Aspect 3> A method for injecting reducing gas into a blast furnace according to embodiment 1 or 2, The reducing gas includes hydrogen gas. Method for injecting reducing gas into a blast furnace. <Aspect 4> A blast furnace, A hot air tuyere is provided below the lower end of the blast furnace shaft and above the taphole, A reducing gas injection port is provided below the lower end of the blast furnace shaft and above the taphole, It has, 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 less than the specific gravity of the hot air blown into the blast furnace from the hot air tuyeres. The aforementioned reducing gas inlet is provided separately from the aforementioned hot air vent, The height position P1 at the center of the reducing gas inlet is the same as the height position P2 at the center of the hot air tuyere, or is located below the height position P2. Blast furnace. <Aspect 5> A blast furnace according to embodiment 4, The aforementioned height position P1 is located below the aforementioned height position P2. Blast furnace. <Aspect 6> A blast furnace according to embodiment 4 or 5, The reducing gas includes hydrogen gas. Blast furnace. [Effects of the Invention]

[0006] According to the technology of this disclosure, when a reducing gas with a low specific gravity is injected into the interior of a blast furnace, the flow velocity of the reducing gas can be controlled, and the uneven flow of the reducing gas can be suppressed. [Brief explanation of the drawing]

[0007] [Figure 1]It schematically shows the structure of a blast furnace. Some structures provided in the blast furnace are shown in an omitted manner. [Figure 2A] It schematically shows an example of the positional relationship between the hot blast tuyere and the reducing gas injection port in a blast furnace. [Figure 2B] It schematically shows an example of the positional relationship between the hot blast tuyere and the reducing gas injection port in a blast furnace. [Figure 2C] It schematically shows an example of the positional relationship between the hot blast tuyere and the reducing gas injection port in a blast furnace. [Figure 3A] It schematically shows the positional relationship between the hot blast tuyere and the lance for a prior example. [Figure 3B] It schematically shows the positional relationship between the hot blast tuyere and the reducing gas injection tuyere for Example 1. [Figure 3C] It schematically shows the positional relationship between the hot blast tuyere and the reducing gas injection tuyere for Example 2. [Figure 3D] It schematically shows the positional relationship between the hot blast tuyere and the reducing gas injection tuyere for Example 3. [Figure 3E] It schematically shows the positional relationship between the hot blast tuyere and the reducing gas injection tuyere for Example 4. [Figure 3F] It schematically shows the positional relationship between the hot blast tuyere and the reducing gas injection tuyere for Comparative Example 1. [Figure 3G] It schematically shows the positional relationship between the hot blast tuyere and the reducing gas injection tuyere for Comparative Example 2. [Figure 3H] It schematically shows the positional relationship between the hot blast tuyere and the reducing gas injection tuyere for Comparative Example 3.

Mode for Carrying Out the Invention

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

[0009] 1. Method for Injecting Reducing Gas into a Blast Furnace As shown in Figure 1, the method for injecting reducing gas into a blast furnace 10 according to one embodiment is: Hot air is blown into the interior of the blast furnace 10 from a hot air tuyeres 13 located below the lower end 11ax of the shaft of the blast furnace 10 and above the taphole 12, This includes injecting reducing gas into the interior of the blast furnace 10 from a reducing gas inlet 14 located below the lower end 11ax of the shaft of the blast furnace 10 and above the taphole 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 less than the specific gravity of the hot air. The reducing gas inlet 14 is provided separately from the hot air nozzle 13. The height position P1 at the center of the reducing gas inlet 14 is the same as the height position P2 at the center of the hot air tuyere 13, or is located below the height position P2.

[0010] 1.1 Hot air nozzle The blast furnace 10 has hot air tuyeres 13 located below the lower end of the shaft 11ax and above the tapping port 12. The "lower end of the shaft" refers to the boundary between the shaft 11a and the furnace belly (belly) 11b. The "shaft" refers to the part above the furnace belly 11b, where the furnace diameter usually increases from top to bottom. The "furnace belly" refers to the part below the shaft and above the bellows (bosch) 11c, where the furnace diameter is usually the largest. The furnace diameter (diameter) of the furnace belly 11b may be, for example, 5m to 20m, or 10m to 18m. The "tapping port" refers to the molten iron tapping port located at the bottom of the blast furnace 10. The "hot air tuyeres" refer to nozzles for blowing hot air into the blast furnace. The blast furnace 10 may have hot air tuyeres 13 located below the lower end 11bx of the furnace belly and above the taphole 12, or it may have hot air tuyeres 13 located below the lower end 11cx of the bellows and above the taphole 12.

[0011] The configuration of the hot air tuyere 13 is well 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 furnace 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 furnace via the hot air pipe and the hot air tuyere 13. The diameter of the hot air tuyere 13 (the diameter of the opening facing the inside 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 tuyeres 13 provided in the blast furnace 10 is not particularly limited and can be determined according to the internal volume of the blast furnace. Multiple hot air tuyeres 13 may be arranged in the circumferential direction of the blast furnace 10. In other words, in the blast furnace 10, multiple hot air tuyeres 13 may be arranged in the circumferential direction when viewed from above. Typically, the height position P2 of the center of each of the multiple hot air tuyeres 13 is the same.

[0013] 1.2 Reducing gas inlet The blast furnace 10 has a reducing gas inlet 14 located below the lower end 11ax of the shaft 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 located below the lower end 11ax of the shaft and above the taphole 12, near the hot air tuyeres in the height direction of the furnace, it is less likely that the reducing gas inlet 14 will obstruct the discharge of molten iron or slag.

[0014] There are no particular restrictions 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 (e.g., copper) or a refractory material.

[0015] In the blast furnace 10, molten iron and slag may drip into the reducing gas inlet 14. Also, when hydrogen gas is injected as a reducing gas from the reducing gas inlet 14 to reduce the amount of carbon material added, 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 with the reducing gas. In this regard, a water cooling structure may be provided around the reducing gas inlet 14 (or inside the wall of the tuyere if the reducing gas inlet 14 is a tuyere) to suppress melting or erosion of the metal or refractory material defining the reducing gas inlet 14.

[0016] The reducing gas inlet 14 can be connected to an external reducing gas supply source of the blast furnace 10 via a reducing gas supply channel or the like. In other words, the blast furnace 10 can be configured so that reducing gas is injected into the interior of the blast furnace 10 from a reducing gas supply source via a reducing gas supply channel and the reducing gas inlet 14. There are no particular restrictions on the form of the reducing gas supply source or the reducing gas supply channel.

[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, it is possible to increase the diameter of the reducing gas inlet 14 regardless of the shape and size of the hot air tuyere 13. This makes it possible to control the flow velocity of the reducing gas to less than the speed of sound, even when a large amount of reducing gas is injected from the reducing gas inlet 14. Assuming 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 diameter equivalent to the circle of the opening facing the interior of the blast furnace 10) may be, for example, 30 mm or more and 400 mm or less, or 60 mm or more and 100 mm or less. Alternatively, the diameter of the reducing gas inlet 14 may be 0.15% or more and 8% or less, or 0.5% or more and 3% or less, of the diameter of the furnace belly 11b. Alternatively, the diameter of the reducing gas inlet 14 may be 7.5% to 200% of the diameter of the hot air nozzle 13.

[0018] The number of reducing gas inlets 14 provided in the blast furnace 10 is not particularly limited. For example, multiple reducing gas inlets 14 may be arranged in the circumferential direction of the blast furnace. In other words, in the blast furnace 10, multiple reducing gas inlets 14 may be arranged in the circumferential direction when viewed from above. The height position P1 of the center of each of the multiple reducing gas inlets 14 may be the same.

[0019] 1.3 Positional relationship between the hot air nozzle and the reducing gas inlet In this embodiment, it is important that the height position P1 at the center of the reducing gas inlet 14 is the same as, or lower than, the height position P2 at the center of the hot air tuyere 13. According to our new findings, if the height position P1 at the center of the reducing gas inlet 14 is higher than the height position P2 at the center of the hot air tuyere 13, the reducing gas injected from the reducing gas inlet 14 tends to rise along the wall surface of the blast furnace 10, causing uneven flow of the reducing gas inside the blast furnace 10. In contrast, if the height position P1 at the center of the reducing gas inlet 14 is the same as, or lower than, the height position P2 at the center of the hot air tuyere 13, the amount of reducing gas flowing below the hot air inside the blast furnace 10 increases, and the amount of reducing gas rising along the wall surface decreases, making it easier for the reducing gas to reach the radial center (furnace center) inside the blast furnace 10. As a result, uneven flow of the reducing gas inside the blast furnace 10 is suppressed, and the utilization efficiency of the reducing gas is improved. In particular, the effect of suppressing the uneven flow of the reducing gas becomes even more pronounced when the height position P1 of the center of the reducing gas inlet 14 is lower than the height position P2 of the center of the hot air tuyere 13.

[0020] Figures 2A and 2B show the case where the height position P1 of the center of the reducing gas inlet 14 is lower than the height position P2 of the center of the hot air tuyere 13. As shown in Figure 2A, the center of the reducing gas inlet 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 inlet 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. Also, as shown in Figure 2B, the center of the reducing gas inlet 14 may be located diagonally below the center of the hot air tuyere 13. That is, in the circumferential direction of the blast furnace 10, the center of the reducing gas inlet 14 may be located at a different position from the center of the hot air tuyere 13. For example, when multiple hot air tuyeres 13 are provided in the circumferential direction of the blast furnace 10, the position of the reducing gas inlet 14 in the circumferential direction of the blast furnace 10 may be located between the multiple hot air tuyeres 13. As far as the inventors have confirmed, the effect of suppressing the uneven flow of reducing gas is further enhanced when the height position P1 of the center of the reducing gas inlet 14 is lower than the height position P2 of the center of the hot air tuyere 13, and the position of the center of the reducing gas inlet 14 in the circumferential direction of the blast furnace 10 is between the centers of the multiple hot air tuyeres 13.

[0021] Figure 2C shows the case where the height position P1 of the center of the reducing gas inlet 14 is the same as the height position P2 of the center of the hot air tuyere 13. As shown in Figure 2C, the reducing gas inlet 14 may be provided next to the hot air tuyere 13.

[0022] The length L between the height position P1 at the center of the reducing gas inlet 14 and the height position P2 at the center of the hot air tuyere 13 is 0 mm or more. This length L may be, for example, 0 mm or more and 3000 mm or less, greater than 0 mm and 300 mm or less, or greater than 0 mm and 300 mm or less.

[0023] 1.4 Hot air The hot air blown in from the hot air tuyer 13 may consist of, 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 between 1000°C and 2000°C, between 1000°C and 1700°C, between 1000°C and 1500°C, or between 1000°C and 1300°C. The flow velocity of the hot air in the hot air tuyer 13 (the flow rate of the hot air (m) 3 / s) / Opening area of ​​the outlet of the hot air nozzle 13 (m 2 )) may be adjusted according to the operating conditions of the blast furnace 10. In one embodiment, the flow velocity of the hot air may be the flow velocity V1 described later.

[0024] 1.5 Reducing gas The reducing gas injected from the reducing gas inlet 14 is a gas that functions as a reducing agent inside the blast furnace 10. That is, even if a gas does not function as a reducing agent before being injected into the blast furnace 10, if it can generate reducing components by thermal decomposition inside the blast furnace 10, it is included in the term "reducing gas" as used in this application. Furthermore, the specific gravity of the reducing gas is less than the specific gravity of the hot air injected into the blast furnace 10 from the hot air tuyere 13. Examples of such reducing gases include at least one selected from hydrogen gas, hydrocarbon gases (e.g., methane gas), carbon monoxide gas, and ammonia gas. In particular, when the reducing gas includes hydrogen gas, an even greater effect can be expected from the technology of this disclosure. The temperature of the reducing gas injected from the reducing gas inlet 14 may be, for example, 0°C to 2000°C, or 25°C to 1500°C. Furthermore, as described above, in this embodiment, a reducing gas inlet 14 is provided separately from the hot air tuyere 13, thereby increasing the flow velocity (flow rate (m³) of the reducing gas. 3 / s) / Opening area of ​​the outlet of the reducing gas inlet 14 (m 2The velocity can be controlled to be less than the speed of sound. That is, the velocity of the reducing gas at the reducing gas inlet 14 is less than 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 or other means depending on the type and temperature of the gas injected into the blast furnace 10. In one embodiment, the velocity of the reducing gas may be the velocity V2 described later.

[0025] 1.6 Flow velocity of hot air and flow velocity of reducing gas The flow velocity V1 of the hot air blown in from the hot air tuyeres 13 is not particularly limited, but for example, if the flow velocity V1 is between 100 m / s and 1000 m / s, and more particularly between 200 m / s and 400 m / s, the uneven flow of reducing gas inside the blast furnace 10 is more easily suppressed. Also, the flow velocity V2 of the reducing gas blown in from the reducing gas inlet 14 is not particularly limited, but for example, if the flow velocity V2 is between 100 m / s and 1000 m / s, and more particularly between 200 m / s and 800 m / s, the ventilation inside the blast furnace 10 is stable, and the in-furnace reduction reaction proceeds stably.

[0026] 1.7 Other Gases Other gases may be blown in along with the reducing gas from the reducing gas inlet 14. Examples of other gases include inert gases such as nitrogen gas.

[0027] 2.Blast furnace The technology disclosed herein has aspects not only as a method for injecting reducing gas into a blast furnace, but also as a blast furnace itself. That is, as shown in Figure 1, a blast furnace 10 according to one embodiment is A hot air tuyere 13 is provided below the lower end 11ax of the shaft of the blast furnace 10 and above the taphole 12, The blast furnace 10 has a reducing gas inlet 14 located below the lower end 11ax of the shaft and above the taphole 12. The reducing gas blown 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 less than the specific gravity of the hot air blown into the blast furnace 10 from the hot air tuyeres 13. The reducing gas inlet 14 is provided separately from the hot air nozzle 13. The height position P1 at the center of the reducing gas inlet 14 is the same as the height position P2 at the center of the hot air tuyere 13, or it is located below the height position P2.

[0028] As described above, in the blast furnace 10, the effect of suppressing the uneven flow of reducing gas is considered to be further enhanced when the height position P1 is located below the height position P2. Furthermore, the effect of the technology of this disclosure is considered to be further enhanced when the reducing gas contains hydrogen gas.

[0029] 3. Supplement In the operation of the blast furnace 10, for example, iron ore (iron oxide) and coke are charged into the blast furnace 10 from the top, while hot air is blown into the blast furnace 10 from a hot blast furnace outside the blast furnace 10 via hot air pipes and hot air tuyeres 13, and reducing gas is blown into the blast furnace from a reducing gas supply source outside the blast furnace 10 via a reducing gas flow path and reducing gas inlet 14. The coke and other materials supplied into the blast furnace 10 are burned to generate reducing gas. The iron oxide is reduced and dissolved by the reducing gas produced by the combustion of the coke and other materials, and by the reducing gas blown in from the reducing gas inlet 14, to obtain molten iron. The molten iron is tapped out from a tap 12 located at the bottom of the blast furnace 10. In this embodiment, by blowing reducing gas into the blast furnace 10 via the reducing gas inlet 14, the amount of carbon-containing reducing material such as coke used can be reduced accordingly. As a result, CO2 emissions can be reduced. The blast furnace 10 can take on various configurations as long as it is capable of producing pig iron as described above. For example, the blast furnace 10 may have other tuyeres and inlets in addition to the hot air tuyeres 13 and reducing gas inlets 14 described above. Also, in the blast furnace 10, other reducing gas inlets may be located above the hot air tuyeres 13. As the configuration of the blast furnace 10 other than the hot air tuyeres 13 and reducing gas inlets 14 is known in the art, a detailed explanation is omitted here.

[0030] 4. Effects As described above, according to this embodiment, by injecting reducing gas into the blast furnace 10 through a reducing gas inlet 14 provided separately from the hot air tuyere 13, the flow velocity of the reducing gas can be controlled to less than the speed of sound. Furthermore, by having the height position P1 of the center of the reducing gas inlet 14 be the same as the height position P2 of the center of the hot air tuyere 13, or lower than the height position P2, uneven flow of the reducing gas inside the blast furnace 10 can be suppressed. [Examples]

[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 for the adoption of various conditions without departing from its gist and insofar as it achieves its objective. In the following examples, the case in which hydrogen gas is used as the reducing gas is illustrated, but the type of reducing gas is not limited thereto.

[0032] 1. Examination of hydrogen gas flow velocity Using a simulation model, the required hydrogen injection rate per hydrogen gas inlet was estimated for a blast furnace with an average production rate of 12,000 t / d, assuming a reduction rate of 30% or more in carbon consumption per unit of production, based on a hydrogen injection temperature of 600°C. The hydrogen gas flow velocity was calculated from the estimated required hydrogen injection rate and the hydrogen gas inlet diameter. A "○" was used to indicate that the calculated flow velocity was slower than the speed of sound in a hydrogen atmosphere, while a "×" was used to indicate that it was faster 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.

[0033] [Table 1]

[0034] As is clear from the results shown in Table 1, conventional lances (lances built into the hot air tuyeres) cannot inject hydrogen gas at a flow rate below the speed of sound. In other words, conventional lances have limitations on the flow rate of hydrogen gas injected into the blast furnace, and cannot sufficiently reduce the carbon consumption per unit of fuel. In contrast, when injecting hydrogen gas through a large-diameter nozzle (for example, a reducing gas nozzle provided separately from the hot air tuyeres), an inner diameter of 60 mm at 1 atmosphere and 80 mm even at furnace pressure allows for the injection of hydrogen gas at a flow rate below the speed of sound. Inner diameters of 60 mm and 80 mm are not significantly different from the inner diameters of hot air tuyeres provided in blast furnaces, and can be used without problems in blast furnaces. Furthermore, increasing the temperature of hydrogen makes the speed at which sound is reached even faster. That is, by increasing the temperature of hydrogen, it is possible to inject hydrogen gas at a flow rate below the speed of sound even when the diameter of the nozzle is reduced. However, even if the hydrogen temperature is increased, it was found that reducing the diameter of the inlet to the conventional lance diameter makes it difficult to control the hydrogen gas flow rate to below the speed of sound.

[0035] From the above, it can be said that by injecting reducing gas into the blast furnace not through a lance built into the hot air tuyer, but through a reducing gas injection port (for example, a reducing gas injection tuyer) provided separately from the hot air tuyer, the flow velocity of the reducing gas can be controlled to below the speed of sound.

[0036] 2. Consideration of the location for injecting reducing gas. Using a simulation model, the hydrogen concentration difference between the furnace wall at the top surface of the blast furnace interior container and the center of the furnace was compared while changing the injection point of hydrogen gas as the reducing gas. Specifically, the hydrogen concentration difference was determined for each of the following prior examples, Examples 1-4, and Comparative Examples 1-3.

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

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

[0039] Example 2: As shown in Figure 3C, hot air was blown in from a hot air tuyere, and hydrogen gas was blown in from a reducing gas injection tuyere, which was provided separately from the hot air tuyeres, between a plurality of hot air tuyeres in the circumferential direction of the furnace and below the lower end of the hot air tuyeres.

[0040] Example 3: As shown in Figure 3D, hot air was blown in from a hot air tuyere, and hydrogen gas was blown in from a reducing gas injection tuyere, which was provided separately from the hot air tuyeres, between a plurality of hot air tuyeres in the circumferential direction of the furnace, at the same height as the lower end of the hot air tuyeres.

[0041] Example 4: As shown in Figure 3E, hot air was blown in from a hot air tuyere, and hydrogen gas was blown in from a reducing gas injection tuyere, which was provided separately from the hot air tuyeres, between a plurality of hot air tuyeres in the circumferential direction of the furnace, at the same height as the center of the hot air tuyeres.

[0042] Comparative Example 1: As shown in Figure 3F, hot air was blown in from a hot air tuyere, and hydrogen gas was blown in from a reducing gas injection tuyere, which was provided separately from the hot air tuyeres, between a plurality of hot air tuyeres in the circumferential direction of the furnace, at the same height as the upper end of the hot air tuyeres.

[0043] Comparative Example 2: As shown in Figure 3G, hot air was blown in from a hot air tuyere, and hydrogen gas was blown in from a reducing gas injection tuyere, which was provided separately from the hot air tuyeres, between a plurality of hot air tuyeres in the circumferential direction of the furnace and above the upper end of the hot air tuyeres.

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

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

[0046] [Table 2]

[0047] As is clear from the results shown in Table 2, when hydrogen gas was blown in through a conventional lance (a lance built into the hot air tuyer), there was almost no difference in hydrogen concentration at the top surface of the blast furnace interior container (previous example). This is thought to be because the hydrogen gas and hot air were sufficiently mixed at the tuyer level, and the hydrogen was dispersed together with the hot air in the furnace.

[0048] Furthermore, when hydrogen gas was injected from a reducing gas injection tuyere, and the height of the center of the reducing gas injection tuyere was higher than the height of the center of the hot air tuyere, a significant difference in hydrogen concentration was observed between the furnace center and the furnace wall at the uppermost surface of the blast furnace interior container (Comparative Examples 1-3). This is thought to be because the specific gravity of hydrogen gas is lower than that of hot air, and the hydrogen gas was not pushed by the hot air injected from the hot air tuyere, but rather flowed preferentially along the furnace wall.

[0049] In contrast, when hydrogen gas was injected from the reducing gas injection tuyere, if the height of the center of the reducing gas injection tuyere was the same as or lower than the height of the center of the hot air tuyere, there was almost no difference in hydrogen concentration at the uppermost surface of the blast furnace interior container (Examples 1-4). This is thought to be because the hydrogen gas injected from the reducing gas injection tuyere was pushed by the hot air injected from the hot air tuyere, moving towards the furnace center below the level of the hot air tuyere, and rising together with the hot air.

[0050] From the above, it can be said that when reducing gas is injected from a reducing gas inlet (for example, a reducing gas inlet) that is provided separately from the hot air tuyere, the uneven flow of reducing gas inside the blast furnace can be suppressed if the height position P1 of the center of the reducing gas inlet is the same as, or lower than, the height position P2 of the center of the hot air tuyere.

[0051] 3. Summary In summary, the following methods (1) and blast furnace (2) allow for easy control of the flow velocity of a reducing gas with a low specific gravity when it is injected into the blast furnace, and also suppress the uneven flow of the reducing gas.

[0052] (1) A method for injecting reducing gas into a blast furnace, Hot air is blown into the interior of the blast furnace from a hot air tuyeres located below the lower end of the blast furnace shaft and above the taphole, This includes injecting reducing gas into the interior of the blast furnace from a reducing gas injection port located below the lower end of the blast furnace shaft and above the taphole, The reducing gas is a gas that functions as a reducing agent inside the blast furnace. The specific gravity of the reducing gas is less than the specific gravity of the hot air. The aforementioned reducing gas inlet is provided separately from the aforementioned hot air vent, The height position P1 at the center of the reducing gas inlet is the same as the height position P2 at the center of the hot air tuyere, or is located below the height position P2. Method for injecting reducing gas into a blast furnace.

[0053] (2) A blast furnace, A hot air tuyere is provided below the lower end of the blast furnace shaft and above the taphole, A reducing gas injection port is provided below the lower end of the blast furnace shaft and above the taphole, It has, 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 less than the specific gravity of the hot air blown into the blast furnace from the hot air tuyeres. The aforementioned reducing gas inlet is provided separately from the aforementioned hot air vent, The height position P1 at the center of the reducing gas inlet is the same as the height position P2 at the center of the hot air tuyere, or is located below the height position P2. Blast furnace. [Explanation of Symbols]

[0054] 10 blast furnace 11a shaft 11b Hearth (Berry) 11c Morning Glory (Bosch) 12 Taphead 13 Hot air nozzle 14. Reducing gas inlet

Claims

1. A method for injecting reducing gas into a blast furnace, Hot air is blown into the interior of the blast furnace from a hot air tuyeres located below the lower end of the blast furnace shaft and above the taphole, This includes injecting reducing gas into the interior of the blast furnace from a reducing gas injection port located below the lower end of the blast furnace shaft and above the taphole, The reducing gas is a gas that functions as a reducing agent inside the blast furnace. The specific gravity of the reducing gas is less than the specific gravity of the hot air. The reducing gas inlet is not built into the hot air tuyere, but is provided separately from the hot air tuyere. The height position P of the center of the aforementioned reducing gas injection port. １ However, the height position P of the center of the hot air nozzle ２ The same as, or the aforementioned height position P ２ Located below, Method for injecting reducing gas into a blast furnace.

2. A method for injecting reducing gas into a blast furnace according to claim 1, The height position P １ However, the aforementioned height position P ２ Located below, Method for injecting reducing gas into a blast furnace.

3. A method for injecting reducing gas into a blast furnace according to claim 1 or 2, The reducing gas includes hydrogen gas. Method for injecting reducing gas into a blast furnace.

4. A blast furnace, A hot air tuyere is provided below the lower end of the blast furnace shaft and above the taphole, A reducing gas injection port is provided below the lower end of the blast furnace shaft and above the taphole, It has, 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 less than the specific gravity of the hot air blown into the blast furnace from the hot air tuyeres. The reducing gas inlet is not built into the hot air tuyere, but is provided separately from the hot air tuyere. The height position P of the center of the aforementioned reducing gas injection port. １ However, the height position P of the center of the hot air nozzle ２ It is the same as, or the height position P. ２ Located below, Blast furnace.

5. A blast furnace according to claim 4, the height position P １ is located below the height position P ２ ​ Blast furnace.

6. A blast furnace according to claim 4 or 5, The reducing gas includes hydrogen gas. Blast furnace.

Images