Blast furnace operation method

Abstract

Provided is a method for operating a blast furnace, which solves the problem that a long time of at least 5.5 months is required after a pause in a conventional blast furnace sealing technique, and which enables smooth blow-in of the blast furnace in a short pause period. In the blast furnace operation method, the height of the surface of a raw material filling layer right above the tuyere of the blast furnace is reduced than the height of the upper end of the belly of the blast furnace, blowing down is carried out, and then blowing-down is carried out again, in which after the blast furnace is blown down, oxygen-containing gas is blown in from the tap hole, coke remaining between the tuyere and the tap hole is combusted, and the volume of the residue in the furnace is reduced. The coke is recharged into the volume-reduced area, and then the tuyere at the upper part of the tap hole is opened to start blowing.

Description

Technical Field

[0001] The present invention provides a blast furnace operation method, which relates to a method for starting up a blast furnace during banking when re-blowing air while there is still content remaining in the furnace during the blow-down operation of the blast furnace. Background Art

[0002] When the blast furnace is forced to significantly reduce production, since the air supply flow rate becomes low, it may lead to abnormal furnace conditions accompanied by the inerting of the furnace core. Therefore, when the tapping ratio is less than 1.5, the operation is continued with a coke ratio exceeding 400 kg / t. However, coke is a high-cost raw material, resulting in an increase in unit cost, so it is uneconomical. For example, it is also possible to repeatedly implement blowing stops. However, since the coke ratio needs to be increased before and after the blowing stop, an increase in the coke ratio cannot be avoided. As described above, it is very difficult to economically ensure the production reduction flexibility of the blast furnace. Therefore, there is a technique called banking in which the blast furnace is suspended for a long time until the molten iron slag in the furnace solidifies.

[0003] When implementing banking, first, the raw material level is reduced to the tuyere level and cooled until the remaining coke and residual slag in the furnace reach normal temperature (3 months). Then, heavy machinery is put into the furnace, and after removing the remaining coke, a dense paving operation of coke and sleepers is carried out (2.5 months). Therefore, a stoppage period of at least 5.5 months is required.

[0004] One of the main reasons why it takes 5.5 months to prepare for starting up the furnace during the blast furnace suspension is that in order to remove the remaining coke in the furnace, it is necessary to enter the furnace. Therefore, it takes about 90 days to cool the furnace as described above, and the period from the blast furnace suspension to starting up the furnace becomes long. In addition, although heavy machinery is also used to enter the furnace after cooling, as a safety condition, a safety net needs to be set up or the coke needs to be removed throughout the week. Therefore, the operation of removing the remaining coke takes about 40 days. Therefore, it is sometimes impossible to respond to a sudden demand recovery.

[0005] In addition, when updating the auxiliary equipment of the blast furnace, for example, in the case of equipment update that requires about 2 months of blast furnace blowing stop, the suspension period usually becomes longer than necessary.

[0006] Furthermore, as a method for smoothly restarting the operation of a blast furnace after a long-term shutdown, for example, there is the blast furnace operation method of Patent Document 1. In the blast furnace operation method disclosed in Patent Document 1, first, the height of the surface of the raw material filling layer directly above the tuyere of the blast furnace is made smaller than the height of the upper end of the belly of the blast furnace to carry out the shutdown. Then, after the blast furnace is shut down, oxygen or oxygen and combustible gas are blown in from a burner inserted into the taphole to burn the coke remaining in the furnace, reducing the volume of the residues in the furnace. After reloading coke in the volume reduction area, air is supplied from the tuyere.

[0007] [Prior Art Documents]

[0008] [Patent Documents]

[0009] Patent Document 1: Japanese Patent No. 6947345 Gazette Summary of the Invention

[0010] [Problems to be Solved by the Invention]

[0011] However, in the blast furnace operation method described in Patent Document 1, a burner with a complex structure must be used, and a supply pipeline for combustible gas needs to be equipped. Therefore, there is a problem that the preparation of the equipment used in blast furnace operation becomes complicated. In addition, if combustible gas is supplied, hydrogen is generated when the coke burns, and the waste gas components may be within the explosive composition range, presenting a safety problem.

[0012] In addition, if the blast furnace is suspended for a long time, the remaining molten iron slag solidifies. When the solidified molten iron slag is heated during the restart of the blast furnace, the molten iron slag expands, applying tensile stress to the blast furnace shell. As a result, cracks may occur in the shell and cause fracture. Therefore, in order to smoothly restart the blast furnace after a long-term suspension, it is necessary to keep the tensile stress applied to the blast furnace shell within the allowable range.

[0013] Furthermore, as a general method for restarting the blast furnace after a long-term suspension, first, the part other than one or two tuyeres on the taphole is blocked by refractory materials or the like to limit the amount of molten iron slag generated along with the air supply and establish a smooth discharge cycle of a small amount of molten material. Then, the tuyeres in the adjacent part are opened, and the number of opened tuyeres is gradually increased to resume normal operation. However, in this method, it is not clear what degree of tensile stress is applied to the blast furnace shell during the restart of the blast furnace. Therefore, if the opening time of the tuyeres in the adjacent part is too early, the expansion speed of the molten iron slag becomes high, and there is a problem that the blast furnace shell breaks and the blast furnace cannot be restarted smoothly.

[0014] The object of the present invention is to solve the above problems, to solve the problem that in the conventional blast furnace shutdown technology, a long shutdown of at least 5.5 months is required after the suspension, and to propose a blast furnace operation method that can smoothly start up the blast furnace with a short suspension period.

[0015] [Means for Solving the Problem]

[0016] In the blast furnace operation method of the present invention, the height of the surface of the raw material filling layer directly above the blast furnace tuyere is made smaller than the height of the upper end of the blast furnace belly to stop the blast, and then the blast is resumed. Among them, after the blast furnace is stopped, a gas containing oxygen is blown into the tapping hole to burn the coke remaining between the tuyere and the tapping hole, reduce the volume of the residues in the furnace, and then reload coke in the volume reduction area, and then open the tuyere above the tapping hole to start the blast.

[0017] It should be noted that in the blast furnace operation method of the present invention configured as described above, the following is considered a more preferable solution method.

[0018] (1) Strain gauges are provided on the blast furnace bottom iron sheet, and the number of tuyere openings is increased with reference to the measured values of the strain gauges.

[0019] [Effects of the Invention]

[0020] According to the blast furnace operation method of the present invention, the shortest shutdown period in the past was 5.5 months, but even if the equipment is simplified, the shutdown period can be shortened to about 2 months, and the blast furnace can be started up safely and smoothly. Description of the Drawings

[0021] Figure 1 It is a schematic diagram for explaining an embodiment of the blast furnace reduction process in the blast furnace operation method of the present invention.

[0022] Figure 2 It is a schematic diagram for explaining an embodiment of the oxygen injection process in the blast furnace operation method of the present invention.

[0023] Figure 3 It is a schematic diagram for explaining another embodiment of the oxygen injection process in the blast furnace operation method of the present invention.

[0024] Figure 4 It is a diagram for explaining an embodiment of the coke charging process in the blast furnace operation method of the present invention.

[0025] Figure 5 It is a diagram for explaining an embodiment of the blast start process in the blast furnace operation method of the present invention. Detailed Embodiments

[0026] Hereinafter, embodiments of the present invention will be specifically described. It should be noted that the following embodiments illustrate devices and methods for embodying the technical concept of the present invention, and the structure is not limited to the following structure. That is, various changes can be made to the technical concept of the present invention within the technical scope described in the claims.

[0027] The blast furnace operation method of the present invention reduces the height of the surface of the raw material filling layer directly above the blast furnace tuyere and shuts down the furnace (blast furnace reduction process), and then resumes blowing (blowing start process). The blast furnace operation method is characterized in that after the blast furnace is shut down, a gas containing oxygen is blown into the tapping hole (oxygen blowing process) to burn the coke remaining between the tuyere and the tapping hole, reducing the volume of the residues in the furnace (coke volume reduction process). And after charging coke again into the volume reduction area (coke charging process), the tuyere above the tapping hole is opened to start blowing (blowing start process).

[0028] Hereinafter, the blast furnace reduction process ( Figure 1 ), oxygen blowing process ( Figure 2 ), coke charging process ( Figure 3 ), and blowing start process ( Figure 4 ) in the blast furnace operation method of the present invention will be described in sequence. It should be noted that in Figure 5 , 1 is the blast furnace, 1a is the iron skin of the blast furnace 1, 2 is the tuyere, 3 is the tapping hole, 4 is the normal raw material level, 5 is the raw material level during reduction, 5a is the volume reduction area, 6 is the molten iron slag, and 7 is the new coke. Figures 1 to 5 <Blast furnace reduction process>

[0029]

[0030] Figure 1 Figure 1 is a schematic diagram for explaining an embodiment of the blast furnace reduction process in the blast furnace operation method of the present invention. As Figure 1 shows, in the reduction process of the blast furnace, the height of the surface of the raw material filling layer directly above the tuyere 2 of the blast furnace 1 is reduced from the normal raw material level 4 to the raw material level 5 during reduction. Here, the raw material level 5 during reduction refers to a position where the height is reduced compared to the upper end of the blast furnace belly, for example, the position of the tuyere 2 (tuyere level).

[0031] To perform the reduction operation of the blast furnace, first, additional coke is charged and the charging of iron raw materials is suspended. While blowing hot air into the furnace from the tuyere 2, the raw material charging level is reduced. The hot air blowing flow rate from the tuyere 2 is reduced according to the descending condition of the raw materials. Reduction is performed when the charging of iron raw materials is suspended and the hot air blowing flow rate is reduced. The temperature rise of the top gas is cooled by sprinkling water from the sprinkler pipe provided at the top of the furnace and reduced. The raw material charging level is reduced to the tuyere level, the sprinkling is stopped, the hot air blowing from the tuyere 2 is stopped, and the furnace is shut down.

[0032] <Regarding the oxygen injection process>

[0033] Figure 2 It is a schematic diagram for explaining an embodiment of the oxygen injection process in the blast furnace operation method of the present invention. Figure 3 It is a schematic diagram for explaining another embodiment of the oxygen injection process in the blast furnace operation method of the present invention. In the oxygen injection process, first, as Figure 2 shown, after the blast furnace is shut down, a gas containing oxygen is injected from the tapping hole 3 to burn the coke remaining between the tuyere 2 and the tapping hole 3. Then, as Figure 3 shown, the volume of the residues in the furnace is reduced to form a volume reduction region 5a.

[0034] In blast furnace operation, when the ventilation and liquid flowability between the tuyere and the tapping hole cannot be ensured, the molten iron and slag produced in the furnace cannot be discharged from the tapping hole to the outside of the furnace, and the molten iron slag stays in the furnace. As a result, there may be ventilation failures and tuyere breakages caused by an increase in the pressure loss in the furnace, and further, furnace cooling failures where the molten iron slag in the blast furnace solidifies.

[0035] During a long-term shutdown of the blast furnace, since the solidified molten iron slag adheres to the gaps between the coke between the tapping hole and the tuyere or the coke becomes small in particle size during the cooling process in the furnace, the porosity between the tapping hole and the tuyere may be reduced. Therefore, a gas containing oxygen is introduced to burn and consume the coke between the tapping hole and the tuyere.

[0036] In the oxygen injection process of the blast furnace operation method of the present invention, it is found that by directly injecting a gas containing oxygen through the lance pipe from the tapping hole, the coke between the tapping hole and the tuyere can be burned and consumed. Therefore, even without using a burner with a complex structure having a combustion function as in the prior art, by injecting a gas containing oxygen using a lance pipe with a simple structure, stable shutdown of the blast furnace can be achieved. It should be noted that when burning and consuming the coke between the tapping hole and the tuyere, since the lance pipe becomes high temperature, it is preferably made into a double-pipe structure, with oxygen supplied from the inner pipe part and nitrogen supplied to the outer pipe part to cool the lance pipe.

[0037] <Regarding the coke charging process>

[0038] Figure 4 It is a diagram for explaining an embodiment of the coke charging process in the blast furnace operation method of the present invention. As Figure 4As shown, in the coke charging process, coke without adherent solidification products is charged into the cavity part where the coke has been combusted and consumed, i.e., the volume reduction area 5a. As an example, the coke charging can be carried out by the following method. First, new coke 7 is pre-filled into a flexible container. Then, the flexible container filled with new coke 7 is suspended above the volume reduction area 5a of the in-furnace residue by a top crane. In this way, after positioning the flexible container, the flexible container is dropped towards the volume reduction area 5a. Thereby, the new coke 7 together with the flexible container is charged into the volume reduction area 5a. After charging the new coke 7 into the volume reduction area 5a, the auxiliary raw materials, coke, and iron raw materials added for composition adjustment during coke ash slagging are charged into the furnace via a distribution chute and filled to the normal raw material level 4.

[0039] <Regarding the blast start process>

[0040] Figure 5 It is a diagram for explaining an embodiment of the blast start process in the blast furnace operation method of the present invention. In the azimuth where there is no tapping hole 3 in the circumferential direction of the blast furnace, the residual coke between the tapping hole and the tuyere has not been combusted and consumed and has not been replaced with new coke 7 without adherent solidification products. Therefore, as Figure 5 shown, in the blast start process, the tuyere 2 above the tapping hole 3 into which a gas containing oxygen is blown is opened, and the blast is started from the tuyere 2. Here, the position of the tuyere 2 does not necessarily have to be arranged directly above the tapping hole 3 into which a gas containing oxygen is blown, as long as it is arranged above the tapping hole 3 into which a gas containing oxygen is blown. In addition, it is not necessary to open only one tuyere, and multiple adjacent tuyeres can also be opened above the tapping hole 3. Therefore, in the furnace start-up operation after a long-term shutdown, as Figure 5 shown, the preferred range of the opened tuyeres is 30 - 50° (here it is 40°) above the tapping hole 3 into which a gas containing oxygen is blown.

[0041] And, after starting the furnace by opening the tuyere 2 above the tapping hole 3, while confirming that the melt can be discharged without problems, the range of the opened tuyeres is gradually expanded in sequence, and all the tuyeres are opened and the blast is started again.

[0042] In the blast furnace operation method of the present invention, as a preferred embodiment, a strain gauge can also be provided on the iron sheet 1a at the bottom of the blast furnace 1, and the number of opened tuyeres is increased with reference to the measured value of the strain gauge. According to this preferred embodiment, for example, through the measured value of the strain gauge, the tensile stress applied to the iron sheet 1a at the bottom of the blast furnace 1 can be monitored. Therefore, the fracture of the iron sheet 1a of the blast furnace 1 caused by the expansion of the molten iron slag due to heating can be eliminated. As a result, the blast furnace can be started up smoothly.

[0043] [Examples]

[0044] In a blast furnace with an internal volume of 5000 m 3 , the height of the surface of the raw material filling layer directly above the tuyere of the blast furnace is reduced to the tuyere level to stop the blast, and then oxygen is supplied from the taphole to the lance at a rate of 400 Nm 3 / hr or more and 900 Nm 3 / hr or less, and the average flow rate is 600 Nm 3 / hr. At the same time, cooling nitrogen for the lance is supplied from the taphole to the lance at a rate of 400 Nm 3 / hr or more and 1300 Nm 3 / hr or less, and the average flow rate is 1000 Nm 3 / hr to carry out the combustion operation of the residual coke between the tuyere and the taphole.

[0045] After the coke combustion consumption operation, coke is charged into the formed cavity (volume reduction area). Then, blowing is started with the tuyere opening at the upper part of the taphole that reliably connects the taphole and the tuyere and other tuyeres closed. At this time, a strain gauge is installed on the blast furnace bottom iron skin, and the number of opened tuyeres is increased in such a way that the measured value of the strain gauge is below the allowable range. In Table 1 below, the number of days required for stopping the blast and subsequent recovery to the normal operating state is compared between the prior art and the present technology. Here, the prior art is as follows: after reducing the raw material line to the tuyere level, it is cooled until the residual coke and residual slag in the furnace become normal temperature, and heavy machinery is put into the furnace to carry out the removal of the residual coke and the paving operation of coke and sleepers.

[0046] [Table 1]

[0047]

[0048] From the results in Table 1, it can be seen that in the present technology, compared with the prior art, it takes 20 more days from restarting the blowing to restoring to the normal operating state with all tuyeres opened, but the total recovery days can be shortened by about 100 days. In addition, the blast furnace iron skin does not break, and the blast furnace can be smoothly started up.

[0049] Explanation of reference numerals

[0050] 1 Blast furnace

[0051] 1a Iron skin

[0052] 2 Tuyere

[0053] 3 Taphole

[0054] 4 Normal raw material level

[0055] 5 Raw material level during reduction

[0056] 5a volume reduction region

[0057] 6 molten iron slag

[0058] 7 new coke

Claims

1. A blast furnace operation method, characterized in that during a blast furnace shutdown, the height of the surface of the raw material filling layer directly above the tuyere of the blast furnace is reduced compared to the height of the upper end of the blast furnace belly, and then the blast is resumed. After the blast furnace is shut down, a gas containing oxygen is blown into the taphole to burn the coke remaining between the tuyere and the taphole, reducing the volume of the residues in the furnace. Then, coke is recharged into the volume reduction area, and then the tuyere above the taphole is opened to start the blast.

2. The blast furnace operation method according to claim 1, characterized in that, Strain gauges are installed on the blast furnace bottom iron sheet, and the number of tuyere openings is increased with reference to the measured values of the strain gauges.

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