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

Abstract

Disclosed is a method for increasing the possibility that a reducing gas can be stably blown into a blast furnace via a reducing-gas-blowing lance even when the furnace state of the blast furnace becomes unstable and molten slag or the like flows back into a hot-air tuyere. A method according to the present disclosure is used for blowing a reducing gas into a blast furnace, the method comprising blowing hot air into the interior of the blast furnace from a hot-air tuyere that is provided to the blast furnace at a position below a shaft lower end and above an iron tapping hole, as well as blowing a reducing gas into the interior of the blast furnace via a reducing-gas-blowing lance that is provided in the wall surface of the hot-air tuyere and has an opening at the distal-end part of the hot-air tuyere. The reducing gas functions as a reducing material in the interior of the blast furnace. The height position P1 of the center of the opening in the reducing-gas-blowing lance is above the height position P2 of the center of the hot-air tuyere.

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 the hot blast flow path or wall surface of a hot blast tuyere, and reducing gas is injected through the lance. Although not intended to inject reducing gas, Patent Document 2 discloses a method in which a fuel injection lance is inserted into the wall surface of a hot blast tuyere, and pulverized coal as fuel is injected into the blast furnace through the fuel injection lance.

[0003] Patent No. 4997734 Patent No. 5840202

[0004] In the prior art, when the furnace conditions become unstable and molten slag or the like flows back into the hot blast tuyere, it may become difficult to stably inject reducing gas into the blast furnace. This application discloses a technology that increases the possibility of stably injecting reducing gas into the blast furnace even when slag or the like flows back into the hot blast tuyere.

[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: blowing hot air into the interior of the blast furnace from a hot blast 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 through a reducing gas injection lance provided within a wall surface of the hot blast tuyere and having an opening at a tip end of the hot blast tuyere, wherein the reducing gas functions as a reducing agent inside the blast furnace, and a height position P of the center of the opening of the reducing gas injection lance is set at a height P of the center of the opening of the reducing gas injection lance. １ The height position P of the center of the hot air tuyere ２A method for injecting reducing gas into a blast furnace, wherein the reducing gas injection lance is located at a height P of the center of the opening of the reducing gas injection lance, and the height P of the center of the opening of the reducing gas injection lance is at a height P of the center of the opening of the reducing gas injection lance. １ The height position P of the center of the hot air tuyere ２ A blast furnace located above.

[0006] According to the technology disclosed herein, even if the furnace conditions in the blast furnace become unstable and molten slag or the like flows back into the hot blast tuyere, the possibility of stably injecting reducing gas into the blast furnace through the reducing gas injection lance is increased.

[0007] 1 is a schematic diagram illustrating an example of the configuration of a blast furnace. Some components provided in the blast furnace are omitted. 2 is a schematic diagram illustrating another example of the configuration of a lance tip at the tip of a hot blast tuyere. 3 is a schematic diagram illustrating an example of the positional relationship between a hot blast tuyere and a reducing gas injection lance in a blast furnace. 4 is a schematic diagram for explaining the position where slag reaches when slag flows back into a hot blast tuyere.

[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: blowing hot air into the interior of the blast furnace 10 from a hot blast tuyere 13 provided below the shaft lower end 11ax of the blast furnace 10 and above a tap hole 12; and injecting reducing gas into the interior of the blast furnace 10 from a reducing gas injection lance 14 provided within a wall surface of the hot blast tuyere 13 and having an opening 14a at a tip end 13a of the hot blast tuyere 13. The reducing gas is a gas that functions as a reducing agent inside the blast furnace 10. A height position P of the center of the opening 14a of the reducing gas injection lance 14 is １ is the height position P of the center of the hot air tuyere 13 ２ It exists above.

[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 usually increases from top to bottom. The "belly" refers to the portion below the shaft and above the bosch 11c, where the furnace diameter usually becomes maximum. The furnace diameter (diameter) of the belly 11 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 Injection Lance The blast furnace 10 has a reducing gas injection lance 14. The reducing gas injection lance 14 can be connected to a reducing gas supply source 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 from the reducing gas supply source into the interior of the blast furnace 10 via the reducing gas supply passage and the reducing gas injection lance 14. There are no particular limitations on the configuration of the reducing gas supply source or the reducing gas supply passage.

[0014] In this embodiment, it is important that the reducing gas injection lance 14 is provided within the wall surface of the hot air tuyere 13. The "reducing gas injection lance provided within the wall surface of the hot air tuyere" does not necessarily have to be embedded in the wall surface of the hot air tuyere up to the tip of the lance as shown in FIG. 1 . It also includes, for example, a configuration in which at least a portion of the lance is exposed within the flow path of the hot air tuyere while contacting the inside of the wall surface of the hot air tuyere, as shown in FIG. 2 . That is, as long as at least a portion of the entire circumference of the reducing gas injection lance is located inside the wall surface of the hot air tuyere and the reducing gas injection lance can be cooled by the water-cooling structure within the hot air tuyere (as long as thermal damage to the lance can be suppressed), a portion of the entire circumference of the lance may be exposed within the flow path of the hot air tuyere. From the viewpoint of further suppressing thermal damage to the reducing gas injection lance, it is preferable that the entire circumference of the reducing gas injection lance is provided within the wall surface of the hot air tuyere. In this embodiment, the reducing gas injection lance 14 has an opening 14a at the tip 13a of the hot air tuyere 13, and is configured so that reducing gas is injected into the blast furnace 10 through the opening 14a. The phrase "a reducing gas injection lance having an opening at the tip of the hot air tuyere" means that the reducing gas injection lance opens at or near the tip of the hot air tuyere. In this embodiment, the tip surface of the hot air tuyere and the lance opening do not need to be flush with each other (i.e., the tip of the lance does not need to reach the tip of the hot air tuyere). That is, "having an opening at the tip of the hot air tuyere" includes not only a configuration in which the tip surface of the hot air tuyere and the lance opening are flush with each other (i.e., the tip of the lance reaches the tip of the hot air tuyere), but also a configuration in which the tip of the lance reaches near the tip of the hot air tuyere. Specifically, a lance is considered to have an "opening at the tip of the hot air tuyere" when the distance from the tip of the lance to the tip of the hot air tuyere is 0 mm or more and 50 mm or less. In this way, in this embodiment, the reducing gas injection lance 14 is provided within the wall surface of the hot air tuyere 13, so that the reducing gas injection lance 14 is less likely to be exposed to hot air, and even if it is exposed to hot air, the reducing gas injection lance 14 can be cooled by the water-cooling structure within the wall surface of the hot air tuyere 13, thereby suppressing thermal damage to the reducing gas injection lance 14, etc.

[0015] The diameter of the opening 14 a of the reducing gas injection lance 14 (the circle-equivalent diameter of the opening facing the inside of the blast furnace 10) may be, for example, 10 mm to 50 mm, or 20 mm to 30 mm. Alternatively, the diameter of the opening 14 a of the reducing gas injection lance 14 may be 0.05% to 0.8%, or 0.1% to 0.5% of the diameter of the hot blast tuyere 13.

[0016] The number of reducing gas injection lances 14 provided in the blast furnace 10 is not particularly limited. For example, at least one reducing gas injection lance 14 may be provided in at least one hot blast tuyere 13 provided in the blast furnace 10. In other words, when the blast furnace 10 has a plurality of hot blast tuyere 13, only some of the plurality of hot blast tuyere 13 may have reducing gas injection lances 14, or all of the plurality of hot blast tuyere 13 may have reducing gas injection lances 14. Furthermore, one reducing gas injection lance 14 may be provided for one hot blast tuyere 13, or multiple reducing gas injection lances 14 may be provided. The height position P of the center of the opening 14a of each of the multiple reducing gas injection lances 14 １ may be the same as each other or may be different from each other.

[0017] 1.3 Positional relationship between the hot blast tuyere and the opening of the reducing gas injection lance In this embodiment, the height position P of the center of the opening 14a of the reducing gas injection lance 14 １ is the height position P of the center of the hot air tuyere 13 ２ It is important that the center of the opening 14a of the reducing gas injection lance 14 is located above the height position P １ is the height position P of the center of the hot air tuyere 13 ２ If the slag injection lance 14 is located above the slag injection lance 14, even if slag or the like flows back into the hot blast tuyere 13, the slag or the like is unlikely to flow back into the reducing gas injection lance 14, and the opening of the reducing gas injection lance 14 can be maintained. Therefore, in this embodiment, even if the furnace conditions in the blast furnace 10 become unstable and molten slag or the like flows back into the hot blast tuyere 13, it is more likely that reducing gas can be stably injected into the blast furnace 10 via the reducing gas injection lance 14. The position (height) to which the slag reaches when a backflow of slag occurs into the hot blast tuyere will be specifically described in the examples.

[0018] 3A and 3B, the height position P of the center of the opening 14a of the reducing gas injection lance 14 is １ is the height position P of the center of the hot air tuyere 13 ２ 3A shows an example in which the center of the opening 14a of the reducing gas injection lance 14 is located above the center of the hot blast tuyere 13. As shown in Fig. 3A, the center of the opening 14a of the reducing gas injection lance 14 may be located directly above the center of the hot blast tuyere 13. That is, the position of the center of the opening 14a of the reducing gas injection lance 14 in the circumferential direction of the blast furnace 10 may be the same as the position of the center of the hot blast tuyere 13. Furthermore, as shown in Fig. 3B, the center of the opening 14a of the reducing gas injection lance 14 may be located diagonally above the center of the hot blast tuyere 13. That is, the center of the opening 14a of the reducing gas injection lance 14 may be located at a position different from the center of the hot blast tuyere 13 in the circumferential direction of the blast furnace 10. Furthermore, when the center position of the opening 14a of the reducing gas injection lance 14 is directly above the center of the hot air tuyere 13 (i.e., when viewed from the tip side of the hot air tuyere 13, the angle between the line segment connecting the center position of the hot air flow path of the hot air tuyere 13 to the center position of the reducing gas injection lance and the horizontal line is 90°), mixing of the hot air and the reducing gas is more advanced relatively, which may be advantageous for improving the reduction efficiency in the furnace.

[0019] 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.

[0020] 1.5 Reducing Gas The reducing gas injected from the reducing gas injection lance 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 includes any gas that can generate a reducing agent (reducing component) by thermal decomposition or the like inside the blast furnace 10. Examples of such reducing gases include at least one selected from hydrogen gas, hydrocarbon gas (e.g., methane gas), carbon monoxide gas, ammonia gas, and alcohol gas (e.g., methanol gas or ethanol gas). In addition, in the technology disclosed herein, at least one selected from coke oven gas (COG), converter gas (LDG), blast furnace gas (BFG), natural gas (NG), and synthesis gas (Syngas) may be used as the reducing gas. These reducing gases may be used alone or in combination of two or more. In particular, when the reducing gas contains hydrogen gas, the technology of the present disclosure is expected to be even more effective. The temperature of the reducing gas injected from the reducing gas injection lance 14 may be, for example, 0°C or higher and 2000°C or lower, or 25°C or higher and 1500°C or lower. In this embodiment, the flow velocity of the reducing gas at the opening 14a of the reducing gas injection lance 14 (flow rate of the reducing gas (m ３ / s) / opening area of ​​the outlet of the reducing gas inlet 14 (m ２ ) may be, for example, equal to or less than the sonic velocity of each reducing gas at the temperature at which the reducing gas is used. In one embodiment, the flow velocity of the reducing gas injected from the reducing gas injection lance 14 may be a flow velocity V2, which will be described later.

[0021] 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, the operation of the blast furnace 10 is likely to be stabilized. Furthermore, the flow velocity V2 of the reducing gas blown from the reducing gas injection lance 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, the ventilation inside the blast furnace 10 is stabilized, resulting in operation in which the reduction reaction in the furnace proceeds stably.

[0022] 1.7 Other Gases Other gases may be injected together with the reducing gas from the reducing gas injection lance 14. Examples of other gases include inert gases such as nitrogen gas.

[0023] 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 injection lance 14 provided within the wall surface of the hot blast tuyere 13 and having an opening 14a at the tip end 13a of the hot blast tuyere 13. The reducing gas injected into the blast furnace 10 from the reducing gas injection lance 14 is a gas that functions as a reducing agent inside the blast furnace 10. The height position P of the center of the opening 14a of the reducing gas injection lance 14 is １ is the height position P of the center of the hot air tuyere 13 ２ It exists above.

[0024] As described above, in the blast furnace 10, the reducing gas injection lance 14 is provided inside the wall surface of the hot blast tuyere 13, so that thermal damage to the lance can be suppressed. １ The height position P of the center of the hot air tuyere 13 ２By being located above this, it is more likely that reducing gas can be stably injected into the blast furnace 10 from the reducing gas injection lance 14 even in a situation where slag or the like flows back into the hot blast tuyere 13.

[0025] 3. Supplementary Information During 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 injection lance 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 injected from the reducing gas injection lance 14 reduce and melt the iron oxide to obtain molten iron. The molten iron is tapped from a tap hole 12 provided at the bottom of the blast furnace 10. In this embodiment, the reducing gas is injected into the inside of the blast furnace 10 through the reducing gas injection lance 14, so that the amount of carbon-containing reducing material such as coke used can be reduced accordingly. 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 lance(s) in addition to the hot blast tuyere(s) 13 and the reducing gas injection lance(s) 14 described above. Furthermore, in the blast furnace 10, other reducing gas injection lance(s) may be present at the same height as the center of the hot blast tuyere(s) 13 or below. The configuration of the blast furnace 10 other than the hot blast tuyere(s) 13 and the reducing gas injection lance(s) 14 is known in the art, and therefore will not be described in detail here.

[0026] 4. Effects As described above, according to this embodiment, the height position P １ The height position P of the center of the hot air tuyere 13 ２By being located above this, even if the furnace conditions in the blast furnace 10 become unstable and molten slag or the like flows back into the hot air tuyere 13, it is more likely that reducing gas can be stably injected into the blast furnace 10 through the reducing gas injection lance 14.

[0027] 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.

[0028] 1. Investigation of Slag Return History An investigation into the occurrence of slag return into the hot blast tuyere of a blast furnace revealed that eight instances of slag return causing blockage of the hot blast tuyere were confirmed over the past 10 years. Here, the height of the slag that reaches during slag return was further investigated. Specifically, as shown in Figure 4, the height of the hot blast tuyere opening was divided into four sections, from the top to the bottom, and the number of times the slag reached each of the "top," "upper center," "lower center," and "lowest" sections was investigated. The results are shown in Table 1 below.

[0029]

[0030] As shown in Table 1, over the past 10 years, the number of times that slag has reached the "bottom" of the hot air tuyere opening due to slag return was 5, the number of times that slag has reached the "lower center" of the hot air tuyere opening was 2, the number of times that slag has reached the "upper center" of the hot air tuyere opening was 1, and the number of times that slag has reached the "top" of the hot air tuyere opening was 0.

[0031] 2. Conclusions Regarding the Position of the Reducing Gas Injection Lance Opening Based on the above-mentioned past operational results, when a lance is disposed within the wall surface of a hot blast tuyere, a lance opening is provided at the tip of the hot blast tuyere, and reducing gas is injected into a blast furnace through the lance opening, if the height position of the center of the lance opening is higher than the height position of the center of the hot blast tuyere, even if slag flows back into the hot blast tuyere due to slag return, the slag is less likely to reach the lance opening, and the lance opening is more likely to be maintained. In other words, according to the following method (1) or blast furnace (2), even if slag flows back into the hot blast tuyere, the possibility of stably injecting reducing gas into a blast furnace via the reducing gas injection lance is increased.

[0032] (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 blast tuyere provided below a lower end of the shaft of the blast furnace and above a tap hole; and injecting reducing gas into the interior of the blast furnace through a reducing gas injection lance provided in a wall surface of the hot blast tuyere and having an opening at a tip end of the hot blast tuyere, wherein the reducing gas functions as a reducing agent inside the blast furnace, and a height position P of the center of the opening of the reducing gas injection lance is １ The height position P of the center of the hot air tuyere ２ A method of injecting reducing gas into a blast furnace located above the

[0033] (2) A blast furnace, comprising: a hot blast tuyere provided below a lower end of the shaft of the blast furnace and above a tap hole; and a reducing gas injection lance provided within a wall surface of the hot blast tuyere and having an opening at a tip end of the hot blast tuyere, wherein the reducing gas injected from the reducing gas injection lance into the inside of the blast furnace is a gas that functions as a reducing agent inside the blast furnace, and a height position P of the center of the opening of the reducing gas injection lance is １ The height position P of the center of the hot air tuyere ２ A blast furnace located above.

[0034] 10 Blast furnace 11a Shaft 11b Furnace belly 11c Morning glory 12 Taphole 13 Hot blast tuyere 13a Tip 14 Reducing gas injection lance 14a Opening

Claims

1. A method for injecting reducing gas into a blast furnace, comprising: blowing hot air into the interior of the blast furnace from a hot blast 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 through a reducing gas injection lance provided within the wall surface of the hot blast tuyere and having an opening at the tip of the hot blast tuyere, wherein the reducing gas functions as a reducing agent inside the blast furnace, and the height position P of the center of the opening of the reducing gas injection lance is １ The height position P of the center of the hot air tuyere ２ A method of injecting reducing gas into a blast furnace located above the 2. 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 injection lance provided within the wall surface of the hot blast tuyere and having an opening at the tip of the hot blast tuyere, wherein the reducing gas injected from the reducing gas injection lance into the inside of the blast furnace is a gas that functions as a reducing agent inside the blast furnace, and a height position P of the center of the opening of the reducing gas injection lance １ The height position P of the center of the hot air tuyere ２ A blast furnace located above.

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