Blast furnace operation method

Abstract

To provide a blast furnace operation method for charging new coke into a furnace while suppressing impact of falling, for starting up the blast furnace.SOLUTION: There is provided a blast furnace operation method configured to: lower a height of a raw material charging layer surface relative to a height of a bosh part upper end of the blast furnace and stop supply of wind; then, supply the wind again. The method is configured to: blow an oxygen-containing gas from a burner which is inserted into a tap hole after supply stop of the wind to the blast furnace; burn the coke left in the furnace, for reducing volume of the residue in the furnace; then, suspend new coke into the furnace from a top of the furnace for charging the new coke into the volume reduction region of the residue in the furnace; then, supply the wind from a tuyere of the furnace.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] A blast furnace is a facility that heats, reduces, and melts iron ore using high-temperature reducing gas generated by the reaction between high-temperature air and oxygen blown in from numerous tuyere ports arranged in the direction of the blast and coke charged from the top of the furnace together with the raw materials, and discharges the molten iron and molten slag from a tap hole installed below the tuyere. During normal operation of a blast furnace, the reaction heat inside the furnace and the heat supply from the tuyere are balanced, allowing for stable operation of the blast furnace.

[0003] Here, when the blast furnace is shut down or stopped for a long time, the heat supply to the blast furnace is stopped. On the other hand, because heat radiation continues due to the temperature difference between the inside of the blast furnace and the atmosphere, the cooling inside the furnace progresses, and some of the molten material solidifies and becomes a solidified material. When restarting the blast from this state, the solidified material in the furnace must be melted, and for that, the coke packed layer through which the solidified material passes must be heated. For this reason, when the blast furnace is shut down for a long time or when it is expected to be restarted, the coke ratio in the furnace is increased to shut down the blast, and thermal compensation is performed until the injection of pulverized coal can be started after the blast. At the same time, all but one or two tuyere above the tap hole are blocked with refractories, etc., to limit the amount of molten iron and slag generated with the blast, and a cycle of smooth discharge of a small amount of molten material is established. After that, the adjacent tuyere is opened, and the number of open tuyere is gradually increased, and normal operation is restored.

[0004] As a method for restoring a blast furnace to normal operation after cessation of blowing, Patent Document 1 discloses that a burner is inserted from the tap hole and oxygen or the like is blown in from the burner to burn the coke between the tap hole and the tuyere to reduce the volume of the solidified material, and then new coke is added from the top of the furnace to the reduced volume area and blown in air from the tuyere, thereby restoring the blast furnace to normal operation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6947345 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the method of Patent Document 1, new coke is charged from the top of the furnace, so that the impact of the drop breaks the coke, and the fine powder generated by this breakage fills the gaps between the coke, thereby deteriorating the gas permeability of the coke layer. This deterioration in gas permeability may make it difficult to smoothly start up the blast furnace after the cessation of blowing.

[0007] The object of the present invention is to propose a blast furnace operation method in which operation is stopped, the blast furnace is tuned down, and then blasted again, in which new coke can be charged into the furnace while suppressing the impact of the fall, thereby enabling the blast furnace to be started up smoothly. [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 blast furnace operation method in which the height of the surface of the raw material packed bed is reduced below the height of the upper end of the morning glory part of the blast furnace, air is stopped, and then air is blown again. After the blast furnace is stopped, oxygen-containing gas is blown in from a burner inserted into the tap hole, and the coke remaining in the furnace is burned to reduce the volume of the residue in the furnace. Then, new coke is hung from the top of the furnace into the furnace and charged into the area where the volume of the residue in the furnace has decreased, and then air is blown from the blast furnace tuyere.

[0009] In addition, in the blast furnace operation method of the present invention, (1) filling a container with the new coke and lowering the container into a furnace to charge the new coke; (2) filling a container with the new coke, suspending the container in a furnace, and charging the new coke into the container; (3) charging the new coke into the container so that the container is at least 1.0 m higher than the blast furnace tuyere; (4) The container is a flexible container having a diameter of 1.5 m or less and a height of 1.5 m or less; (5) The strength of the new coke is 85.6% by mass or more; (6) The moisture content of the new coke is 2.0% by mass or less; are each considered to be a preferred embodiment. Effect of the Invention

[0010] According to the blast furnace operation method of the present invention, in blast furnace operation in which the surface of the raw material packed bed directly above the blast furnace tuyere is lowered below the upper end of the blast furnace morning glory section to stop blowing air, and then blowing air again, destruction of the coke charged in the volume reduction section can be suppressed, making it possible to perform a stable and smooth start-up. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a schematic cross-sectional view showing a part of a cross section of a furnace body of a blast furnace. [Diagram 2] FIG. 2 is a schematic cross-sectional view of the lower part of a blast furnace showing the state in which a burner is inserted from the tap hole. [Diagram 3] FIG. 2 is a schematic diagram showing an example of a burner. [Figure 4] FIG. 2 is a schematic cross-sectional view showing a state in which the volume of the residue in the furnace is reduced by burning the remaining coke using a burner. [Diagram 5] FIG. 2 is a schematic cross-sectional view illustrating a method of loading coke into a furnace by suspending a flexible container from the top of the furnace. [Figure 6] 1 is a schematic cross-sectional view showing a state in which new coke is charged into a volume reduction region together with a flexible container. FIG. [Figure 7] FIG. 1 is a top view of a volume reduction area of ​​the furnace residue before being charged into a flexible container. [Figure 8] FIG. 1 is a top view of a volume reduction region of the furnace residue after the flexible container is charged. 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 example of a blast furnace operation method to which the present invention is applied> FIG. 1 is a schematic cross-sectional view showing a part of the cross section of the furnace body of a blast furnace. In the embodiment shown in FIG. 1, when the blast furnace is shut down for a long period of time, the height of the surface of the raw material packed bed directly above the tuyere of the blast furnace is reduced below the upper end of the morning glory part of the blast furnace to shut down the blast furnace. After that, to return the blast furnace to normal operation by blowing hot air from the tuyere, first, a burner is inserted from the tap hole, and oxygen-containing gas or oxygen-containing gas and combustible gas are blown from the burner to burn the coke remaining in the furnace and reduce the volume of the residue in the furnace.

[0014] Fig. 2 is a schematic cross-sectional view of the lower part of a blast furnace showing a state where a burner is inserted from the tap hole. In the embodiment shown in Fig. 2, the tap hole is blocked with a material called mud material when the blast furnace is not blown, so in order to insert a burner into the furnace, the tap hole blocked with mud material is first opened. A known tap hole opening machine can be used to open the tap hole. After the tap hole is opened, a burner is inserted from the tap hole into the lower part of the blast furnace.

[0015] 3(a) and (b) are schematic diagrams showing an example of a burner. In the embodiment shown in FIG. 3(a) and (b), the burner has a double-tube structure of an inner tube and an outer tube through which gas flows, and has a cap covering the ends of the inner tube and the outer tube, and a thermocouple outside the outer tube for measuring the burner temperature. When the cap is present as shown in FIG. 3(a), the gas blown in from the gas inlet of the inner tube is discharged from the gas outlet of the outer tube without leaking to the outside. On the other hand, when the cap is not present as shown in FIG. 3(b), the gas blown in from the gas inlet of the inner tube is supplied into the furnace. Therefore, the burner has a function of cooling the burner by flowing gas from the inner tube to the outer tube with the cap present, so that the burner can be stably inserted into the furnace.

[0016] Combustion is started by stopping the cooling caused by the gas flow from the inner tube to the outer tube, dissolving and removing the cap, and then, for example, blowing a combustible gas into the furnace from the inner tube of the burner, and blowing an oxygen-containing gas into the lower part of the furnace from the outer tube as a combustion supporting gas. When the temperature at the tip of the burner exceeds the combustion start temperature of the surrounding coke (approximately 800°C), the gas blown from the burner is switched to only the oxygen-containing gas to burn the coke. It is preferable to blow pure oxygen as the oxygen-containing gas, but a gas with an oxygen concentration lower than 100% may be used as long as the coke combustion can be sustained.

[0017] Fig. 4 is a schematic cross-sectional view showing a state in which the volume of the residue in the furnace is reduced by burning the remaining coke using a burner. In the embodiment shown in Fig. 4, when the coke is burned off by combustion, more coke rolls into the space vacated by the burning according to the angle of repose, and the volume of the residue in the furnace is reduced as the coke is burned off one by one.

[0018] <Features of the blast furnace operation method according to this embodiment> The feature of the blast furnace operation method according to this embodiment is that new coke is charged into the volume-reduced region where the volume of the furnace residue has been reduced.

[0019] Fig. 5 is a schematic cross-sectional view illustrating a method of suspending a flexible container from the furnace top to charge coke into the furnace. In the embodiment shown in Fig. 5, new coke is loaded into the flexible container in advance. The flexible container loaded with new coke is suspended by the furnace top crane to above the volume reduction area of ​​the furnace residue. After positioning the flexible container in this manner, the flexible container is dropped into the volume reduction area. As a result, new coke is loaded into the volume reduction area together with the flexible container.

[0020] It is preferable to use an autohook as the hook of the furnace top crane. When the flexible container suspended from the autohook lands, the hook rotates and the load wire is automatically released from the hook. In this way, a flexible container filled with new coke is loaded into the furnace. At this time, the container suspended into the furnace is burned and disappears after the start of air blowing, so it does not adversely affect the start-up operation.

[0021] This operation is repeated to charge new coke together with the flexible container into the residue reduction area. Fig. 6 is a cross-sectional schematic diagram showing a state in which new coke together with the flexible container is charged into the volume reduction area. In the embodiment shown in Fig. 6, it is preferable to charge the flexible container into the furnace so that the upper surface position of the flexible container is 1.0 m higher than the tuyere height of the blast furnace. An operator can visually determine from the furnace mouth whether the upper surface position of the flexible container is 1.0 m higher than the tuyere height.

[0022] As shown in FIG. 6, when a flexible container is charged in a volume reduction region, a gap is generated between the flexible containers. After the flexible container is charged at the tip of the tuyere, hot air is blown from the tuyere, and the flexible container burns due to the hot air, spreading the coke inside the container in the furnace. Since the coke enters the gap between the flexible containers, the charging height of the coke becomes lower than the charging height of the flexible container. Therefore, if the charging height of the flexible container is set to the same as the tuyere height, the charging height of the coke may become lower than the tuyere height. In contrast, by charging the flexible container in the furnace so that the charging height of the flexible container is 1.0 m or more higher than the tuyere height, the coke can be charged at the tip of the tuyere even if the charging height of the coke is lowered. Therefore, it is preferable to charge the flexible container in the furnace so that the upper surface position of the flexible container is 1.0 m higher than the tuyere height of the blast furnace.

[0023] The dimensions of the flexible container used in this embodiment are, for example, a diameter of 1.2 m and a height of 1.3 m. The dimensions of the flexible container are preferably a diameter of 1.5 m or less and a height of 1.5 m or less, because such dimensions allow the flexible container to be suitably loaded into the volume reduction region of the actual in-furnace residue.

[0024] The strength of the new coke used in this embodiment is preferably 85.6% by mass or more in terms of drum strength (DI15 / 150). This is because the use of coke with such strength can further suppress the powdering of the coke due to the impact when it is charged into the furnace. The drum strength (DI15 / 150) can be measured according to JIS K 2151:2004.

[0025] Furthermore, the moisture content of the new coke used in this embodiment is preferably 2.0 mass% or less, because by using coke with such a moisture content, the amount of fine powder adhering to the coke surface and carried into the furnace is reduced, and the decrease in the permeability of the coke layer due to the fine powder can be suppressed.

[0026] In the above-described embodiment, as an example of the present invention, a case has been shown in which new coke is filled into a container, the container is lowered into the furnace, and the new coke is charged into the volume-reduced region of the furnace residue together with the container. However, the blast furnace operation method of the present invention is not limited to a method using a container, and other methods not using a container may also be used, as long as new coke can be lowered into the furnace and charged into the volume-reduced region of the furnace residue. EXAMPLES

[0027] According to the above-mentioned embodiment, the internal volume is actually 5000 m 3 In carrying out a blast furnace operation method in which the height of the surface of the raw material packed bed is reduced below the height of the upper end of the morning glory of the blast furnace, air is stopped, and then air is blown again, new coke is filled into a container, the container is lowered into the furnace, and the new coke is charged into the container and the container together with the container into the area in the furnace where the volume of the residual material has decreased, and an example of an optimal container dimension was determined.

[0028] Fig. 7 is a top view of the volume reduction area of ​​the residue in the furnace before it is charged into the flexible container. Fig. 8 is a top view of the volume reduction area of ​​the residue in the furnace after it is charged into the flexible container. Since the dimension of the white arrow in the volume reduction area shown in Fig. 7 is about 3 m, it can be seen that by using a flexible container with a diameter of 1.5 m or less and a height of 1.5 m or less, new coke filled in a flexible container can be charged into the volume reduction area of ​​the residue, as shown in Fig. 8.

[0029] After the flexible container filled with new coke is charged in front of the tuyere, a predetermined amount of raw ore and coke are charged in alternating layers from the rotating chute at the top of the furnace. Hot air is then blown from the tuyere of the blast furnace to resume operation.

[0030] In this embodiment, a container box with an open bottom may be used instead of the flexible container. In this case, the container box is filled with new coke, and the container box is hoisted and charged into the blast furnace by a crane, and after being positioned above the volume reduction area, the bottom is opened and the new coke is charged into the volume reduction area. After the coke is charged, the emptied container box is hoisted and removed from the furnace top, and the container box is filled with new coke again. Furthermore, a plastic container may be used instead of the flexible container. In this case, the plastic container may be filled with new coke, and the container may be hoisted down into the furnace, and the new coke together with the container may be charged into the furnace.

[0031] Furthermore, when charging into the furnace by hanging, it is not necessary to hang the coke all the way down to the bottom of the furnace, and the flexible container may be dropped after hanging it partway down to charge it. By hanging the coke at least a little from the furnace top to charge into the furnace, the impact of the drop is mitigated compared to charging by dropping the flexible container from the furnace top, and this makes it possible to suppress the coke from being broken into powder.

[0032] As described above, in the blast furnace operation method according to the present embodiment, new coke is lowered from the furnace top into the furnace and charged into the volume-reduced area of ​​the furnace residue. This allows coke to be charged into the volume-reduced area without people having to enter the furnace, and the impact of the drop is mitigated to prevent pulverization due to breakage, allowing a highly permeable coke packed layer to be formed in front of the tuyere of the blast furnace. As a result, the blast furnace can be smoothly started up even after a long period of refueling. [Industrial Applicability]

[0033] According to the blast furnace operation method of the present invention, a smooth start-up of the blast furnace can be realized even after a long period of blast shutdown.

Claims

1. A blast furnace operation method in which the height of the raw material packed bed surface is reduced below the height of the upper end of the morning glory of the blast furnace, and then air is stopped and then air is blown again, A method of operating a blast furnace, comprising blowing in oxygen-containing gas from a burner inserted into the tap hole after shutting down the blast furnace, burning the coke remaining in the furnace and reducing the volume of the residue in the furnace, hanging new coke from the top of the furnace into the area where the volume of the residue in the furnace has decreased, and then blowing air from the blast furnace tuyere.

2. 2. The method of claim 1, further comprising the steps of: filling a container with the new coke; and lowering the container into a furnace to charge the new coke.

3. The method for operating a blast furnace according to claim 1, further comprising the steps of: filling a container with the new coke; suspending the container into a furnace; and charging the new coke into the container.

4. The blast furnace operating method according to claim 3, wherein the new coke is charged into the container so as to be 1.0 m or more higher than the blast furnace tuyere.

5. 5. The method of claim 3 or 4, wherein the container is a flexible container having a diameter of 1.5 m or less and a height of 1.5 m or less.

6. The blast furnace operation method according to any one of claims 1 to 4, wherein the drum strength (DI15 / 150) of the new coke measured in accordance with JIS K 2151:2004 is 85.6% by mass or more.

7. The blast furnace operation method according to any one of claims 1 to 4, wherein the moisture content of the new coke is 2.0% by mass or less.

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