Blast furnace operation method

Abstract

Proposed is a blast furnace operation method that can reduce, to a greater extent than with conventional methods, the amount of melt remaining within a furnace before stopping blasting, without damaging graphite bricks. The present invention is a blast furnace operation method in which blasting is started up again after blasting is stopped. A furnace inner wall of a furnace bottom section of a blast furnace includes: a mud material 3 that blocks a taphole 2 located in an area where a through-hole 7 is opened; and carbon bricks 4 that internally line other areas. A through-hole is opened so that, during lowered-stock operation before blasting is stopped, in the area where the mud material of the taphole is disposed, a lower end 7a of the through-hole on a furnace inner wall surface side is located lower than where the lower end of the through-hole on the furnace inner wall surface side is located during normal operation, thus allowing melt 5 to be discharged via the through-hole.

Description

[Technical field]

[0001] The present invention relates to a method for operating a blast furnace, in which operation is stopped, the blast furnace is shut down, and then the furnace is started up again. [Background technology]

[0002] When blast furnaces are forced to reduce molten iron production, the blast flow rate is reduced, which can lead to poor furnace conditions due to inactivation of the furnace core. If the productivity falls below 1.5 due to a reduction in molten iron production, operations will continue with a coke rate of over 400 kg / t, but this is not economically rational because coke is an expensive raw material. In addition, since the downward elasticity of blast furnace production is limited, if a significant reduction in production is forced, it may be necessary to shut down the blast furnace. In addition, in order to renovate the auxiliary equipment of an aging blast furnace, a blast stop is sometimes carried out on a scale that causes the molten iron and slag in the furnace to solidify. To deal with such situations, there is a technology called banking, which shuts down the blast furnace for a long period of time.

[0003] When banking is implemented, the raw material line must be reduced to the tuyere level, the remaining coke and slag in the furnace must be cooled to room temperature in preparation for blasting (3 months), and then heavy machinery must be brought into the furnace to scrape out the remaining coke and lay coke and sleepers (2.5 months), requiring a shutdown period of at least 5.5 months. This means that it is not possible to rapidly recover demand or carry out intermediate repairs that are limited by the construction period, and it is not possible to adjust production in response to demand trends.

[0004] As a technique for shortening the downtime, Patent Document 1 discloses a method of removing molten iron from the hearth by tapping from a hearth tap hole provided on the furnace wall below the normal tap hole during blow-off. Patent Document 2 discloses a method of providing an opening in the lower wall of a blast furnace after blow-off and carrying out the hearth contents remaining on the entire hearth surface. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2006-137985 A [Patent Document 2] Japanese Patent Application Publication No. 7-197112 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the techniques disclosed in Patent Documents 1 and 2 have a problem in that the hearth tap hole or opening is provided below the tap hole, which damages the carbon bricks that constitute the hearth bricks.

[0007] In order to solve the above problems, an object of the present invention is to propose a blast furnace operation method capable of reducing the amount of molten material remaining in the furnace before the blasting shutdown compared to the conventional method, without damaging the carbon bricks. [Means for solving the problem]

[0008] The blast furnace operation method of the present invention was developed to solve the above-mentioned problems, and is a method of operating a blast furnace which restarts after blast shutdown, in which the inner wall at the bottom of the blast furnace has mud material which blocks the taphole at the portion where the through hole is opened, and carbon bricks which line the other portions, and during reduced-scale operation before blast shutdown, the through hole is opened at the portion where the mud material for the taphole is provided so that the lower end of the opening on the inner wall surface of the furnace is positioned lower than the lower end of the opening on the inner wall surface of the furnace during normal operation, and molten material is discharged through the through hole.

[0009] In addition, in the blast furnace operation method of the present invention, (1) A plurality of tap holes are provided in the circumferential direction of the bottom part of the blast furnace, and during reduced-scale operation before the blast furnace is shut off, the through holes that are blocked with mud material during normal operation are sequentially opened so that the lower ends of the openings on the inner wall surface side of the through holes are positioned lower than the lower ends of the openings on the inner wall surface side of the through holes during normal operation; (2) The through hole is opened so that the lower end of the through hole on the furnace inner wall surface side is positioned at the lower end of the tap hole on the furnace inner wall surface side where the mud material is provided; (3) making the inclination angle of the penetration hole larger than the inclination angle of the penetration hole during normal operation; (4) In order to discharge the molten material from the through hole, the blowing pressure from the tuyere is set to 150 to 250 kPa. (5) After the molten material is discharged through the through hole before the air is stopped, the through hole is blocked with a mud material to stop the air from being stopped, and when the air is restarted, the through hole is opened so that the through hole is in the position during normal operation, and the molten material in the furnace is discharged through the through hole, thereby suppressing a drop in the temperature of the molten material during start-up. is considered to be a more preferable solution. Effect of the Invention

[0010] According to the blast furnace operation method of the present invention, it is possible to reduce the amount of solidified molten material remaining in the furnace after cessation of blasting without damaging the hearth bricks. This makes it possible to suppress the temperature drop of the molten material obtained at the time of restarting the blast furnace, thereby realizing a smoother restart of the blast furnace. [Brief description of the drawings]

[0011] [Figure 1] 1(a) and 1(b) are cross-sectional schematic diagrams showing the state of a tap hole during normal operation of a blast furnace. [Diagram 2] 1( a ) and 1 ( b ) are cross-sectional schematic diagrams showing the state of a tap hole in a blast furnace operation method according to the present invention. [Diagram 3] FIG. 2 is a schematic cross-sectional view for explaining a state immediately before the end of reduction in length in the blast furnace operation method according to the present invention. [Figure 4] FIG. 2 is a schematic cross-sectional view for explaining a method of opening a tap hole in a blast furnace operation method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the embodiments of the present invention will be described in detail. Note that the following embodiments are merely examples of devices and methods for embodying the technical idea of ​​the present invention, and the configuration is not limited to the one described below. In other words, the technical idea of ​​the present invention can be modified in various ways within the technical scope described in the claims. In addition, in the following embodiments, an example of a blast furnace operation method that is the subject of the present invention will be described, and then the features of the blast furnace operation method of the present invention will be described.

[0013] <One embodiment of normal operation of a blast furnace to which the present invention is applied> Figures 1(a) and (b) are schematic cross-sectional views showing the state of the tap hole during normal operation of a blast furnace. Figures 1(a) and (b) show a part of the hearth of a blast furnace 1, and the inner wall of the hearth of the blast furnace is composed of mud material 3 that blocks the tap hole 2 at the part where the through hole 7 is opened, and carbon bricks 4 that line the other parts. 5 is a tuyere.

[0014] A blast furnace 1 is usually provided with a plurality of tap holes 2, for example, four tap holes 2, and these tap holes 2 are alternately used to perform normal operation of the blast furnace. Specifically, focusing on one tap hole 2, as shown in FIG. 1(a), in the tap hole 2 for tapping the molten material 6 in the furnace, a through hole 7 is provided in the mud material 3 blocking the tap hole 2 so as to penetrate from the outside of the furnace to the inside of the furnace, and the molten material 6 in the furnace is tapped through the through hole 7. Then, as shown in FIG. 1(b), the tap hole 2 for not tapping the molten material 6 in the furnace is blocked by the mud material 3, and is configured so that the molten material 6 in the furnace is not discharged to the outside of the furnace from the tap hole 2. Then, after the tapping of the molten material 6 in the furnace is completed, the tap hole 2 is blocked again by the mud material 3. By continuously performing the above operations, normal operation of the blast furnace is performed. In addition, reference numeral 8 denotes a tapping launder that transports the tapped molten material 6 from the furnace to the outside of the furnace.

[0015] <One embodiment of the blast furnace operation method according to the present invention> When a long-term shutdown (hereinafter also referred to as banking) is performed to reduce production or repair the blast furnace 1, a reduced-scale operation is performed to reduce the line of the raw material (molten material 6), for example, to the level of the tuyere 5. In the blast furnace operation according to this embodiment, during the reduced-scale operation before the shutdown, the through hole 7 is opened at the portion of the taphole 2 where the mud material 3 is provided, so that the opening lower end 7a (FIG. 2(a)) of the through hole 7 on the furnace inner wall surface side is lower than the opening lower end 7a (FIG. 2(b)) of the taphole 2 on the furnace inner wall surface side during normal operation, and the molten material 6 is discharged through the through hole 7.

[0016] Fig. 3 is a schematic cross-sectional view for explaining the state immediately before the end of the reduction in length in the blast furnace operation method according to the present invention. As shown in Fig. 3, the molten material 6 (slag 6a and molten pig iron 6b) remaining in the furnace solidifies during banking to become a solidified molten material. Such solidified molten material removes heat from the molten pig iron produced during re-blowing, lowering the temperature of the molten material and reducing the fluidity of the molten material, thus hindering smooth start-up. In contrast, if the solidified molten material remaining in the furnace after banking can be reduced by implementing the blast furnace operation method according to the present invention, the temperature drop of the molten material obtained when the blast furnace is restarted can be suppressed, and a smooth restart of the blast furnace can be realized.

[0017] FIG. 4 is a schematic cross-sectional view for explaining a tap hole opening method in a blast furnace operation method according to the present invention. In the example shown in FIG. 4, the solid line shows a method of opening the through hole 7 by directing the rod of the hole opening machine 11 toward the center of the mud material 3 of the tap hole 2 in the case of tapping during normal operation. Also, the dashed line and the dashed line show a method of opening the through hole 7 by directing the rod of the hole opening machine 11 toward the mud material 3 of the tap hole 2 so that the through hole 7 is located lower than the through hole 7 during normal operation during the reduced scale operation before the blasting stop of the blast furnace operation method according to the present invention. Here, the example of the dashed line shows a state in which the carbon brick 4 forming the tap hole 2 is hardly worn when opening the hole during the reduced scale operation. Also, the example of the dashed line shows a state in which the carbon brick 4 forming the tap hole 2 is worn when opening the hole during the reduced scale operation. Normally, the carbon bricks 4 are worn down by about 0.1° / year from the time of firing to the time of reduced-scale operation. Therefore, even if the angle of the through hole 7 opened by the rod of the hole-opening machine 11 is increased according to the number of years since firing, as in the example shown by the dashed line, the carbon bricks 4 are not damaged and the maximum effect of removing the molten material from the furnace can be obtained.

[0018] As an example, in the case of tapping during normal operation shown by the solid line, the angle of the penetration hole 7 with respect to the mud material 3 of the taphole 2 is set to 10° and the hole is opened by the rod of the hole opening machine 11. In the case of reduced-scale operation shown by the dashed line, the angle of the penetration hole 7 with respect to the mud material 3 of the taphole 2 is set to 13.8° and the hole is opened by the rod of the hole opening machine 11. Furthermore, in the case of reduced-scale operation shown by the dashed and dotted line, the angle of the penetration hole 7 with respect to the mud material 3 of the taphole 2 is set to 15° and the hole is opened by the rod of the hole opening machine 11.

[0019] As shown in the example of the dashed line or the dashed line in FIG. 4, if the inclination angle of the through hole 7 with respect to the mud material 3 of the tap hole 2 is made higher than the through hole 7 during normal operation, the lower end 7a of the through hole 7 on the furnace inner wall surface side can be made lower than the lower end 7a of the through hole 7 during normal operation. In this way, in order to make the lower end position 7a of the through hole 7 on the furnace inner wall surface side lower than the lower end 7a of the through hole 7 during normal operation, it is preferable to make the hole opening angle of the hole opening machine 11 higher than the conventional one. Since it is difficult to change the height of the hole opening machine 11, if it is possible to deal with it by simply changing the inclination angle of the hole opening machine 11, the lower end of the through hole on the furnace inner wall surface side can be easily lowered.

[0020] Table 1 below shows the liquid level, liquid level drop, reduced volume of molten material, and reduced mass of molten material when the inclination angle of the through hole 7 is changed. Here, the through hole angle of 10° indicates the inclination angle of the through hole 7 during normal operation. In addition, the through hole angles of 13.8° and 15° are inclination angles at which the lower end 7a of the through hole 7 is the lower end inside the furnace of the tap hole 2 where the mud material 3 is provided. The molten material reduction effect in the cases of the through hole angles of 13.8° and 15° was calculated as the amount of molten material reduction relative to the case of normal operation with a through hole angle of 10°, which is set to 0.

[0021] [Table 1]

[0022] As shown in Table 1, the liquid level of the molten material decreases as the angle of the through hole 7 is increased and the lower end position 7a of the through hole 7 is lowered, and the volume and mass of the molten material 6 remaining in the furnace are reduced. The lower limit of the lower end position 7a of the through hole 7 is the lower end of the inside of the furnace of the tap hole 2 where the mud material 3 is provided. For this reason, it is preferable to provide the through hole 7 so that the lower end position 7a of the through hole 7 is the lower end position of the inside of the furnace of the tap hole 2 where the mud material 3 is provided, and this makes it possible to minimize the molten material 6 remaining in the furnace within a range that does not damage the carbon bricks 4. As a result, the temperature drop of the molten material 6 obtained when the blast furnace is restarted can be further suppressed, and a smoother restart of the blast furnace can be realized. In this embodiment, it is found that in the blast furnace operation method of the present invention, the angle of the through hole 7 during reduced scale operation is preferably set to 13.8° to 15°.

[0023] In addition, the blast pressure from the blast furnace tuyere 5 before reduction is preferably 150 to 250 kPa. Since the level of the molten material 6 inside the furnace is lower than the position of the through hole 7 outside the furnace, the molten material 6 in the furnace is discharged through the through hole 7 due to the pressure difference between the high pressure inside the furnace (blast pressure) and the atmospheric pressure. For this reason, it is preferable to set the blast pressure from the blast furnace tuyere 5 to 150 kPa or more to increase the pressure inside the furnace and increase the pressure difference. This allows even more molten material 6 to be discharged through the through hole 7. On the other hand, if the blast pressure is increased too much, the blast flow rate increases, and the amount of molten material generated increases, which is not preferable. Therefore, the blast pressure from the blast furnace tuyere 5 is preferably 250 kPa or less.

[0024] After the molten material 6 is discharged, the through hole 7 is blocked with the mud material 3 to perform banking. When restarting the blast furnace after that, it is preferable to open the mud material 3 of the taphole 2 to form the through hole 7 so that it is at the through hole position during normal operation, and discharge the molten material in the furnace from the through hole 7. In this way, by lowering the through hole position during reduced-scale operation below the through hole position during restart, a discharge space where no solidified molten material exists in front of the through hole during restart can be secured. This further suppresses the temperature drop of the molten material during restart, and thus enables a smoother restart of the blast furnace.

[0025] Although the above description focuses on one tap hole 2, a blast furnace basically has four tap holes. Basically, two of the four tap holes are used, or three at most. For example, the opening of multiple tap holes can be performed in the following order.

[0026] First, one tap hole is opened, and then the tap hole diagonally opposite to it is opened. When three tap holes are used, the tap hole between the two tap holes that have already been opened is opened. The tap holes may be opened in the order described above, for example, or in another order, and the order of opening is not particularly limited. For example, the order of opening may be determined taking into consideration the need for trough repairs.

[0027] In addition, the time interval for opening the tap hole is not particularly limited and is determined depending on the furnace conditions and the air volume at that time. Therefore, the time interval for opening the tap hole may vary widely, such as 5 minutes, 10 minutes, 1 hour, etc., and is not particularly limited. [Industrial Applicability]

[0028] According to the blast furnace operation method of the present invention, a stable operation method can be provided not only for restarting a blast furnace, but also for various vertical melting furnaces other than a blast furnace. [Explanation of symbols]

[0029] 1 blast furnace 2 Taphole 3 Mud material 4 Carbon Bricks 5 Tuyere 6. Melt 6a Slug 6b Molten iron 7 Through hole 7a Bottom end 8 Tapping sluice 11 Drilling machine

Claims

1. A method for restarting a blast furnace after shutting down, comprising the steps of: The inner wall of the blast furnace hearth has a mud material for blocking a tap hole at a portion where a through hole is opened, and carbon bricks for lining other portions, a blast furnace operating method in which, during reduced scale operation before blasting shutdown, the through hole is opened at a portion of the tap hole where mud material is provided, so that the lower end of the through hole on the inner wall surface side of the furnace is lower than the lower end of the through hole on the inner wall surface side of the furnace during normal operation and is at the lower end position of the tap hole on the inner wall surface side formed by worn carbon bricks, and molten material is discharged through the through hole.

2. 2. A blast furnace operating method according to claim 1, wherein a plurality of tapping holes are provided in the circumferential direction of the bottom part of the blast furnace, and during reduced-scale operation before blast shutdown, the through holes blocked with mud material during normal operation are sequentially opened so that the lower ends of the openings on the inner wall surface side of the through holes are positioned lower than the lower ends of the openings on the inner wall surface side of the through holes during normal operation.

3. The through hole is opened so that a lower end of the through hole on the furnace inner wall surface side is located at a lower end of the tap hole on the furnace inner wall surface side where the mud material is provided. The blast furnace operation method according to claim 1 or 2.

4. The blast furnace operating method according to claim 1 or 2, wherein the inclination angle of the through hole is made larger than the inclination angle of the through hole during normal operation.

5. The blast furnace operating method according to claim 1 or 2, wherein the blast pressure from the tuyere is set to 150 to 250 kPa in order to discharge the molten material from the through hole.

6. 3. A blast furnace operation method according to claim 1 or 2, further comprising the steps of: after discharging the molten material through the through hole before the blasting is stopped, blocking the through hole with a mud material to stop the blasting; and, when restarting the furnace, opening the through hole so that it is in a position during normal operation; and discharging the molten material in the furnace through the through hole to suppress a decrease in temperature of the molten material during start-up.

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