JP2006137985A - Operation method while blast furnace is repaired - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operation method while a blast furnace is repaired, which keeps a tapping ratio at a high level so as not to reduce a production quantity, at the same time, reduces an amount of a solidified deposit such as solidified molten pig iron on a bottom part to reduce a demolition cost, and shortens a repairing period of time. <P>SOLUTION: This operation method comprises the steps of: keeping a monthly mean minimum tapping ratio to 2.1, a monthly mean lowest molten pig iron temperature to 1,520°C, a temperature in a blast furnace bottom to a similar range to the highest temperature in the past, for at least four months before blowing-down; thereby keeping the molten pig iron 2 on the bottom part 1i to a molten state with low viscosity until the blowing-down time to stably keep the thickness of a solidified deposit 3 on the furnace bottom part to 100 mm or thinner; and tapping the molten pig iron on the furnace bottom part from a tap hole 12 at the furnace bottom, which is provided in a furnace wall of a lower part than a normal tap hole 10, in blowing-down. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an operation method at the time of blast furnace repair that reduces the amount of deposits on the bottom of the furnace when the blast furnace is blown over and repaired.

In blast furnaces, lining refractories and furnace cooling equipment are deteriorated and damaged with long-term operation, so repairs are periodically made and replaced.
A particular problem in this blast furnace refurbishment is that the hot metal remaining in the furnace after blow-off operation solidifies at the bottom of the furnace and remains in large quantities as a residue lump. Since the removal of the residual lump is very difficult, there is a problem that the repair period is prolonged and the repair cost is increased.

As a countermeasure against this, for example, there is a case in which a bottom extraction outlet is provided below the normal outlet and the bottom discharge is performed to discharge the hot metal out of the furnace from the residual extraction outlet.
The hot metal discharged by this method is received by a torpedo car via a slag and transported, but when the position of the outlet for removing residue is in a position where it cannot be received by the torpedo car on the equipment layout. Since a torpedo car cannot be used, the discharged hot metal is discharged into a slag pit or the like and crushed to scrape.
However, in the operation period at the end of the furnace cost until the blow-off, the temperature at the bottom of the furnace is lowered due to the lowering of the output ratio from the normal operation in terms of protecting the bottom refractory. For this reason, there is a problem that the amount of solidified adhesion of hot metal at the bottom of the furnace grows and the effect of reducing the thickness of the residue is not sufficient. There are suggestions.

For example, in Patent Document 1, the tip of the extraction pipe charged from the outlet is immersed in an unsolidified salamander (residual molten iron) retained in the furnace bottom, and the outer end of the extraction pipe is provided with a built-in ejector. A blast furnace bottom salamander removal method is disclosed that connects to a transport pipe, sucks the bottom salamander using the ejector effect, and discharges it to the outside of the furnace.
However, this method requires a large ejector that can ensure a large suction force because the salamander has a large specific gravity. In addition, the extraction pipe needs to be equipped with a heat-resistant structure and a heating structure that suppresses the progress of solidification until it is discharged from the extraction pipe. There is also a need to do.
In addition, considering the problem of equipment layout restrictions for the discharge treatment of the suctioned salamander and the estimation error of furnace bottom deposits, it is not possible to install a large diameter outlet as described above near the bottom surface of the melt. Have difficulty.

In Patent Document 2, when the blast furnace is blown off and renovated, the charge is reduced, and when the stock level drops to the top of the tuyere, additional coke is charged, followed by silica, By loading high load packing with high specific gravity, such as iron ore, the core coke is allowed to settle in the hot metal and the molten iron is discharged while preventing melting of the silica and iron ore, reducing the amount of residue Is disclosed.
However, this method has a problem in that a considerable amount of silica or iron ore must be additionally charged at the time of blast furnace blow-off operation, and the additional charge must be scraped out after blow-off, resulting in an increase in work load.

Patent Document 3 discloses that when a refining operation is carried out and a blast furnace is blown off and repaired without reducing the bottom of the blast furnace, a coke ratio of 350 kg / t or less has been reduced since at least one month before the blast furnace is blown off. It is disclosed that the operation at a ratio of 1.8 or less is continued to sink the core coke into the molten iron to reduce the amount of residual lump at the time of blowing.
However, in order to sink the core coke into the hot metal, when the low iron ratio operation is performed before the blast furnace is blown off, there is a problem that not only the productivity is lowered, but the solidification volume of the hot metal is likely to increase. In some cases, it is forced to carry out difficult operations such as dismantling and removing the residue remaining solidified in the furnace.

In order to solve such a problem, prior to refurbishment, there is an increasing demand for reducing the bottom of the furnace as much as possible by discharging residues and solidified deposits outside the furnace as much as possible.
JP 63-243216 A JP 2003-301208 A JP 2001-355011 A

  In the present invention, when the blast furnace is refurbished, while maintaining the output ratio at a high level and suppressing the decrease in the production amount, not only the solidified molten iron at the bottom of the furnace but also the adhering material that adheres to or solidifies at the bottom of the furnace (Hereinafter referred to as “solidified deposits”) to reduce the cost of dismantling work, and to provide a method that enables the repair period to be shortened.

In order to solve the above-mentioned problems advantageously, the present invention has the following (1) to (2).
(1) At least 4 months ago, operation has been carried out to maintain a monthly average minimum hot metal ratio of 2.1 and a monthly average minimum hot metal temperature of 1520 ° C. And operating the molten steel at the bottom of the furnace from the furnace bottom outlet provided on the furnace wall below the normal outlet at the time of blowout. .
(2) The furnace bottom cooling water is adjusted to three stages of continuous water flow / intermittent water flow / reservoir evaporative cooling to maintain the furnace bottom temperature within a range equivalent to the past maximum temperature. Item 2. An operation method at the time of blast furnace repair described in Item 1.

In the present invention, compared to the case of the conventional method,
(1) The amount of solidified deposits at the furnace bottom can be greatly reduced, and the cost of dismantling work can be reduced.
(2) The repair period can be shortened.
(3) The rate of hot metal recovery and commercialization can be increased.
There is an improvement effect.

The present invention will be specifically described with reference to the drawings.
Renovation of the blast furnace is generally performed after the process of shifting from normal operation to reduced scale operation, discharging the hot metal in the furnace, stopping the supply of hot air to the blast furnace, and cooling by pouring water.
In the present invention, when this blast furnace refurbishment is performed, the operating conditions are controlled from at least 4 months before the blow-off, and the output ratio is maintained at a high level to suppress the decrease in the production amount, and the solidification at the bottom of the furnace is suppressed. After suppressing the growth of the kimono, the molten iron remaining at the bottom of the furnace is discharged at the time of blowing out the remaining hot metal so that the amount of solidified deposits at the bottom of the furnace can be reduced.

More specifically, at least 4 months before the blowout, the monthly average iron ratio is maintained at 2.1 (t / d / m ³ ) or higher, the monthly average minimum hot metal temperature is maintained at 1520 ° C or higher, and the furnace bottom temperature has been kept in the past. Maintaining the same temperature range as the maximum temperature (for example, about 400 ° C), keeping the solidified deposit thickness at the bottom of the furnace to 100mm or less, and normally discharging residual hot metal excluding the solidified deposit when blowing up The bottom of the furnace is discharged from the bottom of the furnace provided at the bottom of the opening, thereby making it possible to reduce the amount of solidified deposits remaining on the bottom of the furnace to about 50 to 60% of the conventional amount.

Here, the operation to ensure the monthly average (considering off-wind and fluctuations in operation) minimum output ratio of 2.1 t / d / m ³ and monthly average minimum hot metal temperature of 1520 ° C is to maintain hot metal productivity. In addition, this operation is continued for at least 4 months in order to stably prevent the solidified deposits from gradually growing on the inner surface of the bottom of the furnace bottom due to the effect of cooling the bottom of the furnace. Suppress the growth of solidified deposits stably and reliably to less than 100 mm,
・ Suppresses the decrease in the amount of brewing due to the rise of the furnace bottom due to the growth of solidified deposits.
・ Reduce the cost of dismantling work and shorten the dismantling period.
-Increase the amount of hot metal discharged from the bottom of the furnace and greatly reduce the amount of solidified deposits at the bottom of the furnace. Etc. can be realized.

  Keeping the furnace bottom temperature high is effective to suppress the increase in the layer thickness of the deposits, but ensure that the furnace wall and the furnace bottom are damaged within the allowable range and stable operation until blowout. Therefore, if the past maximum temperature is 400 ° C., for example, if the past maximum temperature is 400 ° C., it is preferable to select within a range of about 300 to 400 ° C. This temperature region can be easily realized by selecting the bottom cooling water from continuous water / intermittent water / reservoir evaporative cooling and adjusting the cooling capacity in accordance with the bottom temperature. .

The present invention will be described more specifically with reference to the drawings.
Fig. 1 shows the implementation of the present invention in a 5,000 m ³ class blast furnace, maintaining a monthly average hot metal ratio of 2.1 t / d / m ³ and a monthly average minimum hot metal temperature of 1520 ° C or higher from at least 4 months before blowing up. Then, after maintaining the furnace bottom temperature in a region equivalent to the past maximum temperature, for example, in the range of 360 to 400 ° C., and suppressing the solidified deposit thickness of the furnace bottom to 100 mm or less, That is, an example of the state of the inside 1i of the furnace bottom before blowing up is schematically shown.
In this state, conceptually, from the bottom of the furnace, solidified deposit 3, residue (molten metal) 2, graphite-based soot layer 4, coke / graphite / soot layer 5, coke / soot layer 6, coke It remains in the order of layer 7.

  The total amount of residue in the residue at the bottom 1i of the furnace is about 1700t (of which the residue 2 is about 1500t). When the residue is blown up in this state, the residue 2 is solidified and remains at the bottom of the furnace. Therefore, along with the solidified deposit 3, dismantling work such as crushing / discharging is extremely difficult, the repair period is prolonged, the repair cost is increased, and the productivity of the blast furnace is greatly reduced. Therefore, the side wall portion 11 that is about 3 to 4 m below the normal spout 10 is used to suppress the growth of the solidified adhering matter 3 until the time of blowout and to maintain the residue 2 in a molten state. The furnace bottom taping is performed from the furnace bottom tapping port 12 having an inner diameter of about 100 mmφ, and the residue 2 is discharged out of the furnace.

  According to the inventors' investigation, in order to maintain the hot metal temperature at 1520 ° C. or more and stabilize the amount of solidified deposits at the furnace bottom at a low level, the monthly average output is 11000 t / d level (monthly average output) It has been found that it is effective to continue the operation at a ratio of about 2.1) for at least about 4 months. Therefore, in the present invention, in order to ensure such a state stably, an operation is performed in which the monthly average output is 11000 t / d level (about 2.1% per month average) from 4 months before the blowout. It is. In order to realize such operations, it is also considered to increase the particle size and strength of coke and improve the liquid permeability of hot metal.

The temperature at the bottom of the furnace temporarily decreases when the wind blows off before the shift to scaled down operation or before the bottom of the furnace is discharged. There is also a concern that the molten iron solidified layer on the surface of the furnace bottom is likely to grow. In order to eliminate this concern, during this time, the cooling by the furnace bottom cooling device 13 is eased and the furnace bottom temperature is set to the past maximum temperature region, for example 400 It is effective to maintain the temperature at about ° C.
In this way, the pre-blow-out operation can be performed to suppress the layer thickness of the solidified deposit 3 at the bottom of the furnace to 100 mm or less. By carrying out dredging, the residue 2 excluding the solidified deposit 3 can be efficiently discharged and collected outside the furnace, and the amount of residue remaining solidified on the bottom of the furnace after being blown up can be almost eliminated.

FIG. 2 schematically shows an example of a furnace bottom outlet 12 for carrying out the furnace bottom extraction, an installation structure of the furnace 16, and a receiving structure (furnace bottom extraction structure) of the residue 2 on the torpedo car 17. It is shown.
The furnace bottom outlet 12 is preferably located as close to the upper surface of the vertical brick 11u as possible in order to reduce the residue 2 residue, but the residue 2 region (temperature sensor installed at the furnace bottom) 14 and the bottom bottom residue height sensor 15), and the optimum position within the range where the residue 2 can be received on the torpedo car 17 is selected and installed (in principle, one location is installed). However, it is also considered to install in multiple places.

When the furnace bottom outlet 12 is installed, first, a hole is made in the iron skin 1a at the time of pre-breathing, and at the end of the scale-down operation (at the time of blow-off).
First, before the reduction operation is completed, a drill is drilled to the middle of the side wall portion 11 and, at the end of the reduction operation (at the time of blowout), the furnace bottom outlet 12 is opened to open the furnace bottom. Carry out tapping.
In addition, the installation position of the furnace bottom outlet 12 is not fixed, and an optimal position for efficiently discharging the residue 2 can be selected according to the formation status of the residue 2 region. In FIG. 4, 13o is a furnace wall cooling device.

The trough 16 that receives the residue 2 discharged from the furnace bottom outlet 12 and transfers it to the torpedo car 17 is a temporary type here, and can be installed when the furnace bottom outlet 12 is installed.
Here, the torpedo car 17 is arranged so as to be movable by switching to the two series of tracks 18, so that the kite 16 is provided with a switching damper 19, and the residue 2 from the furnace bottom outlet 12 is arranged in two series of tracks 18. It can be switched and transferred to the upper torpedo car 17 and is arranged so as to be conveyed as hot metal to a converter or a casting machine.

In this example, in a 5,000 m ³ class blast furnace, the average monthly hot metal ratio is 2.1 or higher and the monthly average lowest hot metal temperature is maintained at 1520 ° C. or higher from 4 months before the blowout. The furnace wall cooling device 13o) is controlled to maintain the furnace bottom temperature at 360 to 400 ° C., which is equivalent to the past maximum temperature, and the operation of suppressing the solidified deposit 3 thickness of the furnace bottom to 100 mm or less, This is a case where the furnace bottom outlet 12 is opened by opening the furnace bottom outlet 12 provided 3.5 m below the normal outlet 10 at the time of blow-off after the reduced scale operation.

The position of the furnace bottom outlet 12 is selected according to the residue 2 area detected by the temperature sensor 14 and the furnace bottom residue height sensor 15 during the scale-down operation (when the wind is off), and the middle of the side wall portion 11 is selected. It was drilled with a cone until it was installed (unopened state), and penetrated and opened at the time of blowout.
After the furnace bottom extraction, the average thickness of the solidified deposit 3 at the bottom of the furnace was approximately 100 mm. The upper layer of the solidified deposit was a graphite-based soot layer 4 that could be scraped, a coke / graphite / soot layer 5, a coke / soot layer 6, and a coke layer 7. The amount of the solidified deposit 3 and the residue in the upper layer is an amount that can be removed by the removing operation for about 9 days.

(Comparative example)
(1) Solidified deposits 3 in the furnace bottom when the operation conditions specified in the present invention (maintaining the monthly average minimum heating ratio 2.1 and the monthly average minimum hot metal temperature 1520 ° C.) are continuously operated for 2 months The average thickness is about 300 mm, and it is assumed that the removal work of the solidified deposit 3 and the upper layer residue takes 12 days.
(2) Furnace bottom when operated continuously for 4 months at a monthly average minimum hot metal temperature of 1500 ° C., wherein the monthly average minimum output ratio is 2.1 or more and specified in the present invention. The average thickness of the solidified deposit 3 is estimated to be about 600 mm, and it is assumed that the removal work of the solidified deposit 3 and the upper layer residue takes 14 days.

  The present invention is not limited to the contents of the above embodiments. Furnace bottom structure, furnace bottom outlet, dredger, torpedo car arrangement, structure, furnace bottom extraction operation, etc. are the furnace volume, output, basic operating conditions, operation schedule, charging raw material, hot air, fine powder of the target blast furnace There is a change within a range that satisfies the scope of the claims according to the blowing conditions of charcoal (heavy oil).

Side sectional conceptual explanatory drawing which shows the example of residual states, such as residue, soot, and coke, in the furnace bottom part of the blast furnace which implemented this invention. The side cross-section conceptual explanatory drawing which shows arrangement | positioning and structural examples, such as a furnace bottom tap outlet, a soot, and a torpedo car for the furnace bottom tap according to this invention.

Explanation of symbols

1: Blast furnace 1a: Iron skin 1i: Inside the furnace bottom 2: Residue (layer)
3: Solidified deposit 4: Graphite main layer 5: Coke / graphite / saddle layer 6: Coke / saddle layer 7: Coke layer 10: Normal outlet 11: Side wall 11u: Vertical brick 12: Furnace bottom outlet 13: Furnace bottom cooling device 13o: Furnace wall cooling device 14: Temperature sensor 15: Residual height sensor 16: １７ 17: Torpedo car 18: Orbit 19: Damper

Claims (2)

  At least 4 months ago, the operation that maintains the monthly average minimum iron ratio of 2.1 and the monthly average minimum hot metal temperature of 1520 ° C will be carried out, and the hot metal at the bottom of the furnace will be kept in a low-viscosity molten state until the time of blowout. Then, the operation method at the time of blast furnace refurbishment, characterized in that the molten iron at the bottom of the furnace is discharged from the bottom of the furnace bottom provided on the furnace wall part below the normal outlet at the time of blowout. The furnace bottom cooling water is adjusted in three stages of continuous water flow / intermittent water flow / reservoir evaporative cooling to maintain the furnace bottom temperature within a range equivalent to the past maximum temperature. Operation method at the time of blast furnace refurbishment described.

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