Pulverized coal injection lance

Abstract

To provide a double tube lance in which gas is circulated through an outer tube and pulverized coal is blown from an inner tube, and which is easy to install and replace while suppressing abrasion of a tuyere inner surface by blown pulverized coal.SOLUTION: A pulverized coal blowing lance having double tube structure is installed through a blower pipe connected to a tuyere, and includes an inner tube for blowing pulverized coal into the tuyere, and a straight tubular outer tube for blowing gas flowing between the inner tube and the outer tube into the tuyere. The inner tube has a tip opening at a position close to the inner surface side of the outer tube or a position in contact with the inner surface at a position of the tip of the outer tube, a straight tube portion coaxial with the central axis of the outer tube, and a curved tube portion formed between the tip opening portion and the straight tube portion and curved at a predetermined bending radius from the straight tube portion. The pulverized coal blowing lance blows pulverized coal in a direction different from the blowing direction of the gas in the outer pipe.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a lance for supplying pulverized coal or the like into a tuyere. [Background technology]

[0002] In blast furnace operation, iron sources such as iron ore, sintered ore, and pellets are alternately charged with coke. One way to reduce costs in blast furnace operation is to reduce the amount of coke charged. Instead of reducing the amount of coke charged, pulverized coal is injected into the tuyere through a lance as a powdered reducing agent.

[0003] A double-tube lance consisting of an inner tube and an outer tube has been proposed as a lance structure for supplying pulverized coal into a tuyere (Patent Document 1). In the lance of Patent Document 1, preheated heating gas, fuel gas, oxygen-containing gas, etc. flow between the outer tube and the inner tube, and solid fuel such as pulverized coal transported by a carrier gas flows through the inner tube.

[0004] Also proposed is a lance in which a gaseous reducing agent flows through an inner tube and a cooling gas flows between the outer tube and the inner tube (Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-213591 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-312757 Summary of the Invention [Problem to be solved by the invention]

[0006] In a double-tube lance, when pulverized coal is circulated through the inner tube and a gaseous reducing agent is circulated through the outer tube and injected into the tuyere, it was found that the pulverized coal injected from the lance into the tuyere collides with the inner surface of the tuyere opposite the tip of the lance, causing wear to the tuyere.

[0007] To address this problem, for example, as in Patent Document 2, if the lance is curved so that the direction in which the pulverized coal is blown is in the same direction as the hot air in the air pipe, the curved portion of the lance makes it difficult to insert or remove the lance from the guide pipe for installing the lance, which is formed on the side of the air pipe.

[0008] The present invention aims to provide a double-tube lance in which gas is circulated through the outer tube and pulverized coal is injected from the inner tube, which suppresses wear on the inner surface of the tuyere caused by the injected pulverized coal and is easy to install and replace. [Means for solving the problem]

[0009] The present invention has been made to solve the above problems, and the gist of the invention is as follows.

[0010] (1) A lance for injecting pulverized coal with a double-pipe structure that is installed to penetrate a blower pipe connected to a tuyere, the lance having an inner pipe for injecting pulverized coal into the tuyere and a straight outer pipe for injecting gas flowing between the inner pipe and the inner pipe into the tuyere, the inner pipe having a tip opening that is located close to the inner surface of the outer pipe at the tip of the outer pipe or in contact with the inner surface, a straight pipe section that is coaxial with the central axis of the outer pipe, and a curved pipe section that is formed between the tip opening and the straight pipe section and bends from the straight pipe section at a predetermined bending radius, the lance for injecting pulverized coal in a direction different from the direction of gas injection into the outer pipe.

[0011] (2) The lance for injecting pulverized coal according to (1) above, characterized in that the direction of injection of pulverized coal from the inner tube into the tuyere is directed toward the tip of the tuyere rather than the direction of injection from the outer tube. According to (2), it is possible to suppress wear of the double-tube lance due to collision of the pulverized coal with the inner surface of the tuyere when it is injected.

[0012] (3) The lance for injecting pulverized coal according to (1) or (2) above, characterized in that the extension of the central axis of the inner pipe at the tip opening passes through the opening with the smallest inner diameter of the tuyere. According to (3), it is possible to suppress wear of the double-tube lance due to collision of pulverized coal with the inner surface of the tuyere when it is injected.

[0013] (4) The lance for injecting pulverized coal according to any one of (1) to (3) above, characterized in that the predetermined bending radius of the curved pipe portion is 500 mm or more and 1000 mm or less. According to (4), it is possible to suppress wear of the inner pipe itself, while suppressing wear of the pulverized coal injected from the inner pipe due to collision with the inner surface of the tuyere.

[0014] (5) The lance for injecting pulverized coal according to any one of (1) to (4) above, characterized in that the gas flowing between the outer tube and the inner tube is a reducing gas. According to (5), even if the gas flowing through the outer tube is a reducing gas that suppresses the combustion of the pulverized coal and makes it easier for the pulverized coal to collide with the inner surface of the tuyere, the pulverized coal is injected toward the opening at the tip of the tuyere, thereby enabling stable operation of the blast furnace by making better use of the effect of suppressing wear due to collisions with the inner surface of the tuyere. [Effects of the Invention]

[0015] According to the present invention, in a double-tube lance in which gas is circulated through the outer tube and pulverized coal is injected from the inner tube, it is possible to provide a double-tube lance that suppresses wear on the inner surface of the tuyere caused by the injected pulverized coal and is easy to install and replace. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 2 is a diagram showing the configuration of the vicinity of the tuyere of the blast furnace according to the present embodiment. [Figure 2] FIG. 2 is an enlarged view of the tip side of the lance of the present embodiment. [Figure 3] 3 is a view of the tip of the lance of the present embodiment as viewed in the direction of arrow A. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment will be described with reference to the drawings. Fig. 1 is a diagram showing the configuration of the vicinity of a tuyere 6 of a blast furnace 1 of this embodiment. Fig. 2 is an enlarged view of the tip side of a lance 10 of this embodiment. In Fig. 2, only the tuyere 6 is shown with a dashed line to show the positional relationship between the lance 10 and the tuyere 6, and other parts such as a blower pipe 8 are omitted.

[0018] In the blast furnace 1, iron ore such as sintered ore, pellets, or lump ore is used as the main raw material, and coke, pulverized coal, gaseous reducing agents, powdered reducing agents, etc. are used as reducing agents. Iron ore and coke are alternately charged in layers from the top of the blast furnace 1. As a result, within the blast furnace 1, a lump zone, a cohesive zone where the iron ore melts and changes from solid to liquid, and a drip zone where the liquid molten iron and molten slag drip down the coke layer are formed. The blast furnace may be a bell-type blast furnace or a bell-less type blast furnace.

[0019] As shown in FIG. 1, a blast furnace 1 of this embodiment is provided with a tuyere 6, a blower pipe 8, and a lance 10 on the side wall thereof.

[0020] The tuyere 6 is an inlet for blowing hot air into the blast furnace 1. The tuyere 6 is installed on the side wall of the blast furnace 1, penetrating the blast furnace shell 2 and the refractory material 4, and is connected to a blower pipe 8. Pulverized coal blown in from a lance 10 is also blown into the blast furnace 1 from the tuyere 6 together with the hot air.

[0021] The blower pipe 8 supplies hot air generated in the hot stove to the tuyere 6. In this embodiment, a lance 10 is installed so as to penetrate the side surface of the blower pipe 8 on the tuyere 6 side. The blower pipe 8 may be provided with a guide pipe for installing the lance 10.

[0022] The lance 10 injects pulverized coal, which is a powdered reducing agent, into the tuyere 6. As described above, the lance 10 penetrates the blower pipe 8 and opens into the tuyere 6. The tip of the lance 10 may be located inside the blower pipe 8. As shown in FIG. 2 , the lance 10 of this embodiment has a double-pipe structure having an inner pipe 12 and an outer pipe 14. Pulverized coal is injected into the inner pipe 12 together with a carrier gas. Gas, such as a gaseous reducing agent, injected from a nozzle 16 flows between the outer pipe 14 and the inner pipe 12. The outer pipe 14 is a straight pipe at least in the range from its tip to the portion that penetrates into the blower pipe 8. Because the range that is inserted into the blower pipe 8 is straight, the lance 10 can be easily inserted into the blower pipe 8 (or a guide pipe into which the lance is inserted) for installation, or removed for replacement.

[0023] In this embodiment, when it is stated that gas flows through the outer pipe 14 or that gas circulates through the outer pipe 14, it means that gas flows in the cylindrical space between the outer pipe 14 and the inner pipe 12. In addition, the direction in which pulverized coal, gaseous reducing agent (gas), etc. are injected into the lance 10 and flow into the tuyere 6 is also referred to as the "injection direction."

[0024] The configuration of the lance 10 of this embodiment will be described in detail with reference to FIGS. 2 and 3. FIG. 3 shows the tip of the lance 10 as viewed downstream in the injection direction of the lance 10 (as viewed in the direction of arrow A in FIG. 2). First, the inventors investigated the case where pulverized coal was injected into a blast furnace using a double-tube lance in which both the inner and outer tubes were straight, with pulverized coal flowing through the inner tube and a gaseous reducing agent flowing through the outer tube. As a result, they found that the main cause of tuyere wear was that the pulverized coal injected into the tuyere from the inner tube was made more linear by the gaseous reducing agent injected from the outer tube, causing the pulverized coal to impinge on the inner surface of the tuyere facing the lance. In other words, they found that the gaseous reducing agent injected from the outer tube flowed tubularly around the pulverized coal, suppressing the dispersion of the pulverized coal and facilitating its linear movement, making it more likely for the pulverized coal to impinge on the inner surface of the tuyere than when only pulverized coal was injected.

[0025] In contrast, in the lance 10 of this embodiment, the outer pipe 14 is straight, but the inner pipe 12 has a curved portion on the downstream side (tip side) in the blowing direction of the lance 10. Specifically, the inner pipe 12 has a straight pipe section 12a that extends coaxially and parallel to the outer pipe 14 on the upstream side in the blowing direction, a curved pipe section 12b that is curved at a predetermined bending radius and continues downstream from the straight pipe section 12a, and a tip section 12c that continues from the curved pipe section 12b and extends to a tip opening 12d at the position of the tip surface of the outer pipe 14.

[0026] The tip opening 12d, which is the end of the inner tube 12, is located on approximately the same plane as the tip surface of the outer tube 14. As shown in Fig. 3, the tip opening 12d is located close to the inner surface of the outer tube 14 at the tip of the outer tube 14. Alternatively, the tip opening 12d may be located in contact with the inner surface of the outer tube 14.

[0027] The inner pipe 12 has a straight pipe-like tip portion 12c and a curved pipe portion 12b formed so as to smoothly connect from the position of the tip opening 12d to a straight pipe portion 12a that is coaxial with the outer pipe 14. Specifically, as shown in Fig. 2, the tip portion 12c extends straight to the curved pipe portion 12b in a direction in which the inner pipe central axis a approaches the outer pipe central axis b. Then, at the curved pipe portion 12b, the inner pipe central axis a curves until it coincides with the outer pipe central axis b (the inner pipe central axis a of the straight pipe portion 12a), and connects to the straight pipe portion 12a.

[0028] As described above, the curved pipe portion 12b is formed between the tip opening 12d and the straight pipe portion 12a. The curved pipe portion 12b bends with a constant bending radius from the end of the straight pipe portion 12a to a position where it smoothly connects with the tip portion 12c, which extends straight from the tip opening 12d. Therefore, the length of the curved pipe portion 12b and the tip portion 12c and the boundary position where the curved pipe portion 12b begins from the straight pipe portion 12a vary depending on the bending radius of the curved pipe portion 12b and the diameters of the inner pipe 12 and the outer pipe 14. Alternatively, the curved pipe portion 12b may have a structure without the straight pipe-shaped tip portion 12c, such that the end of the curved pipe portion 12b is the tip opening 12d.

[0029] In this embodiment, the lance 10 is disposed in the blast pipe 8 in relation to the tuyere 6 and the blower pipe 8 so that the position of the lance 10 around the outer pipe central axis b is such that the curved portion of the inner pipe 12 (curved pipe portion 12b and tip portion 12c) is oriented to deviate the most from the tuyere central axis c. In other words, the lance 10 may be disposed relative to the blower pipe 8 so that the blowing direction of the inner pipe 12 into the tuyere 6 is oriented in the direction furthest from the inner surface of the tuyere on the side opposite to the lance 10. In addition, the lance 10 is preferably disposed in the blower pipe 8 so that an extension line of the inner pipe central axis a at the tip opening 12d of the inner pipe 12 passes through the opening 6a at the position where the inner diameter of the opening on the tip side of the tuyere 6 is smallest.

[0030] With the above-described configuration, the pulverized coal injected from the inner pipe 12 changes direction from the straight pipe section 12a through the curved pipe section 12b and the tip section 12c, and is injected in a direction different from the gas injection direction of the outer pipe 14. Specifically, the outer pipe 14 injects gas toward the inner surface of the opposing tuyere 6 (near the inner surface at the tip of the tuyere in the examples of Figures 1 and 2), whereas the inner pipe 12 injects pulverized coal in a direction more along the tuyere central axis c (air blowing direction within the tuyere) than the outer pipe 14. In other words, the injection direction of the inner pipe 12 into the tuyere 6 is more oriented toward the center of the opening 6a at the tip of the tuyere 6 than the outer pipe 14. As a result, the pulverized coal injected from the inner pipe 12 flows toward the opening of the tuyere 6, thereby preventing it from colliding with the inner surface of the tuyere 6 and reducing wear on the tuyere 6.

[0031] The bending radius R of the curved pipe portion 12b of the inner pipe 12 is preferably 500 mm≦R≦1000 mm. When the bending radius R of the curved pipe portion 12b is within this range, wear of the inner pipe 12 can be suppressed, and the effect of suppressing the pulverized coal injected from the inner pipe 12 from colliding with the inner surface of the tuyere and wearing it can be sufficiently obtained.

[0032] If the bending radius R of the curved pipe portion 12b is less than 500 mm, the curve of the curved pipe portion 12b becomes too sharp, making it more likely that the pulverized coal being injected will collide with the inner surface of the inner pipe, such as the curved pipe portion 12b, and this is undesirable because it increases wear on the inner pipe 12 itself. If the bending radius R of the curved pipe portion 12b is greater than 1000 mm, the blowing direction of the inner pipe 12 cannot be sufficiently directed toward the center of the opening 6a on the tip side of the tuyere 6, and the wear suppression effect on the tuyere 6 cannot be sufficiently obtained.

[0033] In the design stage of the double-tube lance 10, the cross-sectional area of ​​the cylindrical section between the outer tube 14 and the inner tube 12 is determined so that the flow rate of gas flowing through the cylindrical space between the outer tube 14 and the inner tube 12 does not exceed a predetermined value when gas is injected within the gas flow rate range expected in blast furnace operation. This determines the difference between the outer diameter and the inner diameter of the inner tube. The predetermined gas flow rate is set appropriately depending on the equipment and operating conditions, but is set so that it does not exceed the sonic velocity, for example. By determining the diameters of the outer tube 14 and the inner tube 12 in this manner, a sufficient gap is secured between the inner and outer tubes to form the curved tube portion 12b, and the injection direction of the inner tube 12 can be directed toward the opening 6a of the tuyere 6.

[0034] The lance 10 of this embodiment can be applied to any gas flowing through the outer tube 14, but greater effectiveness can be achieved in operations in which a gaseous reducing agent (reducing gas) having the property of suppressing combustion of the pulverized coal injected from the inner tube 12 is injected. This is because if the combustion of the pulverized coal injected into the tuyere 6 is suppressed by the gas from the outer tube 14, the unburned pulverized coal is more likely to collide directly with the inner surface of the tuyere 6 and cause wear. Even in such cases, with the lance 10 having a double-tube structure of this embodiment, the pulverized coal is injected toward the center of the opening 6a at the tip of the tuyere 6, thereby suppressing collision with the tuyere 6 and suppressing wear.

[0035] The gaseous reducing agent (reducing gas) to be blown into the outer tube 14 may be, for example, methane gas, natural gas, city gas, coke oven gas, coal gas, hydrogen gas, or the like.

[0036] Note that the lance 10 of this embodiment can be used for any type of gas as long as the operation involves injecting gas into the outer tube 14. The gas injected into the outer tube 14 may be, for example, an inert gas such as nitrogen used for cooling purposes, air, oxygen, or the like. Even if the gas is a combustion-supporting gas that promotes the combustion of pulverized coal, if any solid remains unburned, the gas is injected toward the center of the tuyere 6, thereby achieving the effect of suppressing wear on the tuyere 6.

[0037] In this embodiment, pulverized coal is injected from the inner tube 12, but the present invention is not limited to this, and a powdered reducing material other than pulverized coal may also be used. For example, the powdered reducing material injected from the inner tube 12 may be needle coke derived from coal tar generated in the process of producing coke, or needle coke produced from petroleum coke.

[0038] According to the present embodiment, in the double lance for injecting pulverized coal and a gaseous reducing agent, the pulverized coal is injected toward the opening at the tip of the tuyere 6, thereby suppressing wear due to collision with the inner surface of the tuyere facing the lance 10. Furthermore, since the outer tube 14 is straight and only the inner tube 12 is curved within the outer tube 14, the lance 10 itself is straight. Therefore, the lance 10 can be easily inserted into the blower pipe 8 (or guide pipe) for installation or removed for replacement. Furthermore, since the bending radius R of the curved pipe portion 12b is 500 mm≦R≦1000 mm, wear inside the inner tube due to bending can be suppressed while wear due to collision of pulverized coal with the inner surface of the tuyere 6 can be sufficiently suppressed. Therefore, the lance 10 of this embodiment can reduce equipment troubles in the tuyere 6 of the blast furnace 1, enabling stable blast furnace operation. [Explanation of symbols]

[0039] 1 blast furnace 2 Blast Furnace Shell 4 Refractories 6 Tuyere 6a opening 8 Air pipe 10. Lance 12 Inner tube 12a Direct Management Department 12b Curved pipe section 12c tip 12d tip opening 14 Outer tube

Claims

1. A lance for injecting pulverized coal having a double-pipe structure that is installed by penetrating a blower pipe connected to a tuyere, an inner tube for injecting pulverized coal into the tuyere; a straight outer tube that blows gas into the tuyere and flows between the outer tube and the inner tube; a straight pipe section that is coaxial with the central axis of the outer pipe; and a curved pipe section that is formed between the tip opening and the straight pipe section and that curves from the straight pipe section at a predetermined bending radius; wherein the inner pipe has a tip opening that is located close to the inner surface of the outer pipe or in contact with the inner surface at the tip of the outer pipe;

2. 2. The lance for injecting pulverized coal according to claim 1, wherein the direction of injection of pulverized coal into the tuyere of the inner tube is directed toward the tip of the tuyere rather than the direction of injection of the outer tube.

3. 3. The lance for injecting pulverized coal according to claim 1, wherein the lance is installed so that an extension line of the central axis of the inner pipe at the tip opening passes through the opening with the smallest inner diameter of the tuyere.

4. 4. The lance for injecting pulverized coal according to claim 1, wherein the gas flowing between the outer tube and the inner tube is a reducing gas.

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