JP2013159801A - Furnace bottom structure of converter, and tuyere replacement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain both productivity and cost in the operation of a converter having a bottom-blowing function.SOLUTION: A furnace bottom structure of a converter is configured to perform refining by blowing a gas into the converter through a plurality of tuyeres 2a-2d provided in a furnace bottom part. The plurality of tuyeres 2a-2d are disposed in such a manner that the distance between the tuyeres 2a-2d being used is 500 mm or more, and the distance between the tuyeres 2a-2d and a fixed furnace floor 3 is 250 mm or more, whereby a tuyere replacement system for inserting a new tuyere for tuyere replacement and a furnace bottom replacement system for replacing the furnace bottom part including the tuyeres can be executed. When a broken tuyere is replaced in an operation using N/2 or less of the tuyeres 2a-2d as operating tuyeres, a gas hole of the operating tuyere is blocked, and the remaining non-operating tuyere is used as a new operating tuyere. The furnace material cost can be reduced 30% or more, compared with in the past, and a stable tuyere wear damage rate can be attained through the service life of the converter.

Description

  The present invention relates to a furnace bottom structure of a converter provided with a tuyere for blowing gas into molten iron or molten steel at the furnace bottom, and a tuyere replacement method for a converter having the furnace bottom structure.

  In a converter having a function of blowing gas into hot metal or molten steel in a furnace from a tuyere provided at the bottom of the furnace, the tuyere (hereinafter sometimes simply referred to as “bottom-blown tuyere”). The wear is large compared to other furnace bottoms and is much greater than the wear on the side walls, so it is common to replace the bottom blow tuyere when worn.

  This bottom-blown tuyere can be replaced by dismantling the worn tuyere and inserting a new tuyere at the dismantled position, or by drilling a perforating brick previously installed at another location. There are a tuyere replacement method for inserting a new tuyere and a furnace bottom exchanging method for exchanging a furnace bottom part including a worn tuyere.

  Of these, the tuyere replacement method requires only a narrow tuyere replacement range, but the tuyere that has been replaced with a decrease in the remaining brick thickness around the tuyere as the number of times the furnace is used or the number of tuyere replacements increases. The life of the is shortened. Therefore, the tuyere must be frequently replaced, which is not preferable for shortening the non-operating time.

  On the other hand, the furnace bottom replacement method also updates the general furnace bottom part other than the tuyere, so even if the number of times the furnace is used increases, wear of the replaced tuyere is relatively small, but the renewal range is wide. Therefore, a large amount of bricks are discarded, which is not preferable. In addition, the replacement work becomes large and the work cost is higher than that of the tuyere replacement method.

  Thus, both the tuyere replacement method and the furnace bottom replacement method have advantages and disadvantages, and are not a tuyere replacement method that achieves both the productivity and cost of converter operation.

Therefore, the following techniques have been proposed for the replacement of the bottom blowing tuyeres of the converter.
In the tuyere exchange system, various tuyere exchange methods such as Patent Documents 1 and 2 have been proposed.

  The technologies proposed in these Patent Documents 1 and 2 are technologies for extending the life of tuyere by exchanging tuyere itself. However, as the number of times the furnace is used increases, the remaining brick thickness around the tuyere decreases and The life expectancy of the mouth is becoming shorter, so it is not a fundamental solution.

  In the furnace bottom replacement system, for example, Patent Document 3 proposes a specific furnace bottom structure. However, the furnace bottom structure proposed in Patent Document 3 also replaces the furnace bottom part of the area including all tuyere with a separately prepared furnace bottom part when the peripheral part of the tuyere is melted. It remains the same. Therefore, there is a problem that, even if the melting loss of bricks other than the tuyere is slight, it must be replaced, and a large amount of bricks are discarded.

Japanese Patent No. 3424144 JP 2004-285475 A Japanese Utility Model Publication No. 1-58647

  The problem to be solved by the present invention is that when replacing the bottom blower tuyeres of the converter, there are a tuyere replacement method and a furnace bottom replacement method, and various proposals have been made. It means that improvement is required from the viewpoint of both productivity improvement and cost reduction.

  In order to solve the above-described conventional problems, the present invention makes it possible to selectively perform tuyere replacement and furnace bottom replacement in accordance with the state of wear of the bottom blowing tuyere and the surrounding furnace bottom. Therefore, it is characterized by having a furnace bottom structure having an exchange function by both tuyere exchange and furnace bottom exchange.

  According to the present invention having such a feature, the bottom through one furnace cost from the completion of the construction of the entire inner wall including the side wall of the converter to the time when the entire inner wall needs to be reconstructed (at the time when the furnace is stopped). The stability of the blowing tuyere life can be ensured, and both improvement in converter productivity and reduction in furnace material costs can be achieved.

  The object of the present invention is to suppress the life reduction of tuyere exchanged through one furnace cost, shorten the non-operation time of the converter to increase productivity, reduce the amount of bricks to be discarded, and It is also to reduce the operating cost of the converter by suppressing the work costs associated with the replacement of the mouth.

  Among these, first, in order to suppress the life reduction of the replaced tuyere, it is necessary to secure not only the tuyere but also the remaining brick thickness at the periphery thereof. Fig. 1 (a) shows the change in the remaining tuyere thickness in the tuyere replacement method, and Fig. 1 (b) shows the change in the remaining tuyere thickness in the furnace bottom exchange method.

  If the number of times the furnace is used is small and the melting damage of the bricks around the tuyere is slight, the tuyere replacement system can ensure a long tuyere life because the effective usage thickness of the tuyere is large, Since the replacement range is only tuyere, the furnace material cost can be reduced.

  On the other hand, in the furnace bottom replacement method, the tuyere life can be secured stably and long, but even though there is a remaining brick thickness other than the tuyere, it will be exchanged including it, so there is an excess range. It becomes exchange.

  When the number of times the furnace is used increases, the melting of not only the tuyere but also the brick around the tuyere progresses. In such a case, in the tuyere replacement method in which only the tuyere is replaced, if the tuyere brick to be replaced is lengthened, it protrudes to the inside of the furnace from the bricks around the tuyere, and the protruding tuyere bricks are scrap or thermal shock. Cause breakage. In addition, when a short tuyere brick having a length equivalent to that of the brick in the vicinity of the tuyere is inserted, the effective use thickness of the tuyere brick becomes small. That is, in any case, the service life is short, and continuing the tuyere replacement in such a state lowers the productivity of the converter and causes the deterioration of the furnace material cost. The use of the converter will be stopped.

On the other hand, in the furnace bottom replacement method, since the bricks around the melted tuyere are also exchanged, the effective usage thickness of the tuyere bricks is not affected by the melting of the bricks around the tuyere and ensures a long tuyere life. can do.
In other words, each replacement method is not appropriate throughout the entire period of one furnace.

  Therefore, in order to secure a stable tuyere life and reduce furnace material costs, the inventor adopted the tuyere replacement method when the melting damage of the bricks around the tuyere was minor, and the melting damage of the bricks around the tuyere We considered that it would be effective to adopt the bottom replacement method when the process progressed, and considered the appropriate bottom range for the bottom structure with both types.

  It is desirable that the exchange range of the furnace bottom be as narrow as possible, but at least four tuyere are available so that the operating tuyere can be selected while taking into account the effect of stirring the molten iron or the entire molten steel in the converter. The effect of the distance between tuyere on wear of tuyere and the effect of wear on the fixed hearth outside the range of furnace bottom replacement due to tuyere position is above 80 tons / charge. It investigated using the bottom blow converter.

  The replacement range of the bottom of the furnace is that the replacement radius R on the top surface of the bottom ware brick is 650 mm, the distances A to C between the tuyere are between 400 to 860 mm, and the distance D between the tuyere and the fixed hearth is It changed between 220-330 mm (refer Fig.2 (a)).

  As a result, in the combined use of the tuyere exchange method and the furnace bottom exchange method, the distance between the tuyere to be used is 500 mm or more, and the distance between the tuyere and the fixed hearth is 250 mm or more. We have found a furnace bottom structure that can stabilize the wear rate and reduce the furnace material cost.

The bottom structure of the bottom blow converter of the present invention is:
Based on the findings of the inventor's investigation above, it was made possible to enable both types of tuyere replacement and furnace bottom replacement,
In a converter for refining by blowing gas into hot metal or molten steel in the furnace from a plurality of tuyere provided at the bottom of the furnace,
By arranging multiple tuyere so that the distance between tuyere for use is 500 mm or more and the distance between tuyere and fixed hearth is 250 mm or more, a new tuyere is inserted and tuyere is replaced. The main feature is that both the tuyere exchanging system and the furnace bottom exchanging system for exchanging the bottom of the furnace including the tuyere can be implemented.

And in the operation of the bottom blowing converter having the furnace bottom structure of the present invention,
The above mentioned feather of a converter in which N (N is an integer) tuyere are arranged at the bottom of the furnace so that the distance between the tuyere for use is 500 mm or more and the distance between the tuyere and the fixed hearth is 250 mm or more. N / 2 or less of the mouths are operated as operating tuyere, and when replacing a working tuyere that has been worn out by operation, the gas holes of the working tuyere are filled, and the remaining non-working tuyere is replaced with new working tuyere. It is preferable to do.

  In the present invention, by adopting a furnace bottom structure that allows both tuyere replacement and furnace bottom replacement, it is possible to reduce the furnace material cost by 30% or more compared to the conventional, and stable tuyere through one furnace cost. It is possible to achieve a wear rate.

(A) is the figure which showed the remaining thickness transition of the tuyere in a tuyere exchange system, (b) is the figure which showed the remaining thickness transition of the tuyere in a furnace bottom exchange system. It is the schematic diagram of the wear brick of an exchange furnace bottom, (a) is the figure seen from upper direction, (b) is the figure which expanded and showed the AA cross section of (a) figure. It is a schematic diagram of the iron skin structure of a furnace bottom, (a) is a longitudinal cross-sectional view, (b) is the figure seen from the downward direction. It is a figure similar to FIG.2 (b) explaining the problem of the comparative example of the furnace bottom structure of this invention.

  The furnace bottom structure of the converter according to the present invention is a converter for refining by blowing gas into molten iron or molten steel in the furnace from a plurality of tuyere provided at the bottom of the furnace. It is possible to implement both the tuyere exchanging method for performing the above and the furnace bottom exchanging method for exchanging the furnace bottom part including the tuyere. The tuyere replacement method and the furnace bottom replacement method are performed by selecting the tuyere replacement and the furnace bottom replacement according to the state of wear of the bottom blowing tuyere and the surrounding furnace bottom. Generally, the tuyere replacement method is used when the melting damage of the bricks around the tuyere is minor, such as in the first half of the furnace cost, and the melting of the bricks around the tuyere, such as in the latter half of the furnace cost. When the process proceeds, it is preferable to adopt the furnace bottom replacement method.

In the furnace bottom structure, it is necessary to arrange a plurality of tuyere so that the distance between the tuyere used for use is 500 mm or more and the distance between the tuyere and the fixed hearth is 250 mm or more.
Further, the tuyere replacement method is such that N (N is an integer) tuyere are arranged at the bottom of the converter, and N / 2 or less of those tuyere are used as working tuyere. When the mouth is worn out, it is preferable to fill the gas holes of the working tuyere and use the remaining non-working tuyere as new working tuyere.

Examples of the present invention will be described below.
80% ton of hot metal at a temperature of 1250 to 1380 ° C. with components of C: 3.2 to 4.9%, Si: 0.01 to 0.80%, P: 0.005 to 0.090% In an upper bottom blowing converter with a furnace capacity of 80 tons / charge, C: 0.03-0.95%, Si: 0.01% or less, P: 0.003-0.030% Refined to ingredients. The bottom blowing gas flow rate during refining was 0.01 to 0.06 Nm ³ / min per ton of molten steel, and the molten steel temperature at the end of refining was set to 1680 ° C to 1710 ° C.

  Test Nos. 1 to 4 listed in Table 1 below are the exchange method defined in the present invention, the shortest distance between tuyere used (hereinafter referred to as the shortest tuyere distance), and between the tuyere and the fixed hearth. This is an example of the invention that satisfies all the conditions of the distance D. On the other hand, Test Nos. 5 to 10 are comparative examples that do not satisfy at least one of the replacement method, the shortest tuyere distance, and the tuyere-fixed hearth distance D defined in the present invention.

  FIG. 2 is a schematic diagram of a replacement furnace bottom wear brick, and FIG. 3 is a schematic diagram of a furnace bottom iron structure. In FIGS. 2 and 3, 2aa to 2da denote nozzle holes of tuyere 2a to 2d, and 3 denotes a fixed hearth. Further, in FIG. 3, 1 a is the iron core of the exchange furnace bottom 1, 4 is the exchange iron skin of the tuyere 2 a to 2 d, 5 is the tuyere nozzle hole flange, and 6 is press fit between the exchange furnace bottom 1 and the fixed hearth 3. A hole 7 indicates the iron skin of the main body.

  In addition, Table 1 below shows a list of conditions of Test Nos. 1 to 10, and Table 2 below shows a list of results of Test Nos. 1 to 10. In addition, this test was done about what has four tuyere 2a-2d in the exchange furnace bottom 1 of a furnace bottom part, as shown in FIG.2 and FIG.3.

  First, in the test method No. 5 (only the operating tuyere is 2b and 2c), the shortest tuyere distance is 781mm, and the distance between the tuyere 2c and the fixed hearth 3 is 259mm. The tuyere wear rate due to is 0.55 mm per charge, and the furnace material cost index at this time was 100. Here, the smaller the furnace material cost index, the lower the cost.

  In addition, in the test method No. 6 with only tuyere replacement (operating tuyere is 2b and 2c), the shortest tuyere distance is 781 mm, and the distance between tuyere 2c and fixed hearth 3 is 259 mm. The tuyere wear rate was 0.68 mm per charge and the furnace material cost index was 102.

  In the tuyere replacement method, the replacement range is only tuyere, so costs can be reduced. Was equivalent to the furnace bottom exchange type.

  Next, although test Nos. 7 to 8 (both operating tuyere are 2b and 2c) are exchange methods using both furnace bottom exchange and tuyere exchange, the distance D between tuyere 2c and fixed hearth 3 is It is a comparative example of less than 250 mm.

  Test No. 7 is a comparative example in which the distance between the tuyere is 820 mm, but the distance D between the tuyere 2c and the fixed hearth 3 is 240 mm. Because the distance between the tuyere 2c and the fixed hearth 3 is small, the wear bricks of the fixed hearth 3 are worn out, and even if the hearth replacement is performed, the fixed hearth 3 and the replacement hearth 1 as shown in FIG. There was a step at the boundary. Then, the spalling of the exchange furnace bottom 1 occurred from this step, and the spalling gradually derived to the inside of the exchange furnace bottom 1 and the wear progressed to the tuyere 2a to 2d. The tuyere wear rate at this time was 0.70 mm per charge, and the furnace material cost index was 104.

  Test No. 8 is a furnace bottom structure in which the distance D between the tuyere 2c and the fixed hearth 3 is 220 mm, which is smaller than that of Test No. 7, so that the same phenomenon as Test No. 7 is further promoted. The mouth wear rate was 0.74 mm per charge, and the furnace material cost index was 108, which was worse than Test No. 7.

  Finally, test Nos. 9 to 10 (both operating tuyere are 2a and 2b) are comparative examples in which the distance between the shortest tuyere is less than 500 mm, although it is an exchange method using both furnace bottom exchange and tuyere exchange. .

  Test No. 9 is a comparative example in which the shortest tuyere distance is 450 mm and the distance D between the tuyere 2a and the fixed hearth 3 is 275 mm. Since the distance between the tuyere 2a and the fixed hearth 3 is 250 mm or more, the wear of the fixed hearth 3 was slight. However, since the shortest tuyere distance is as small as 450 mm, depending on the shape of the mushroom generated at the tuyere's spout, there is much exposure between the tuyere bricks due to bottom blowing gas agitation and protection between the tuyere bricks. However, it was worn like a mortar from the tuyere brick to the center of the furnace bottom. Therefore, the tuyere wear rate was as high as 0.77 mm per charge, and the furnace material cost index was 110.

  Test No. 10 has a furnace bottom structure with a minimum distance between the tuyere of 400 mm, which is smaller than that of Test No. 9, so the same phenomenon as Test No. 9 is further promoted, and the tuyere wear rate is 1 charge. It was 0.85 mm per unit and the furnace material cost index was 120, which was worse than Test No. 9.

  On the other hand, Test Nos. 1 to 4 are exchange methods using both furnace bottom exchange and tuyere exchange. The shortest tuyere distance is 500 mm or more, and the distance D between the tuyere and the fixed hearth is 250 mm or more. It is an example of an invention. Of these test Nos. 1 to 4, test No. 1 uses tuyere 2a and 2b as the initial operating tuyere for one furnace, and test Nos. 2 and 3 use tuyere 2b and 2c for one furnace. This was the initial operational tuyere. In Test No. 4, all four tuyere 2a to 2d were used from the beginning of one furnace cost.

  By doing in this way, compared with the comparative example of the said test No. 5-10, a tuyere wear rate became 0.55-0.62 mm per charge, and the furnace bottom replacement system shown in FIG.1 (b) The furnace material cost index could be greatly reduced to 50-70.

  Among the inventive examples of Test Nos. 1 to 4, if the distance D between the tuyere and the fixed hearth is considerably larger than 330 mm and 250 mm or more as in Test No. 3, the range of the exchange furnace bottom is further narrowed. Thus, it is possible to reduce the furnace material cost index.

  In addition, when half of the tuyere is used as the working tuyere as in Test Nos. 1 to 3, when replacing the tuyere, the gas holes of the worn working tuyere are filled with refractory, and the remaining non-working tuyere By replacing the operating tuyere so as to be a new working tuyere, the wear rate and furnace material cost can be further reduced even with the same working tuyere.

  In the test Nos. 1 to 10, the test was performed on the number of tuyere in the furnace bottom replacement range shown in FIG. 2, but the number of tuyere increased within the predetermined range and the tuyere was fixed on the fixed hearth. It is also possible to provide a replaceable tuyere.

  From the above results, by arranging a plurality of tuyere such that the distance between tuyere used for use is 500 mm or more and the distance between tuyere and fixed hearth is 250 mm or more as in the present invention, It has been confirmed that both the mouth exchange and the furnace bottom exchange can be performed, and the stable tuyere wear rate and furnace material cost can be reduced.

  Further, in the operation of the bottom blown converter having the furnace bottom structure of the present invention, the operation tuyere is operated with half or less of the tuyere as the working tuyere, and the working tuyere gas hole is replaced when the working tuyere worn by the operation is replaced. By curing the remaining non-working tuyere, the wear rate and furnace material cost can be further reduced with the same number of working tuyere.

DESCRIPTION OF SYMBOLS 1 Exchange furnace bottom 1a Exchange furnace bottom iron skin 2a-2d Tuyere 3 Fixed hearth 4 Tuyere exchange iron skin 5 Tuyere nozzle hole flange 6 Press-in hole between exchange furnace bottom and fixed hearth 7 Main body iron skin

Claims (2)

In a converter for refining by blowing gas into hot metal or molten steel in the furnace from a plurality of tuyere provided at the bottom of the furnace,
By arranging multiple tuyere so that the distance between tuyere for use is 500 mm or more and the distance between tuyere and fixed hearth is 250 mm or more, a new tuyere is inserted and tuyere is replaced. A bottom structure of a converter, characterized in that both a tuyere exchanging system and a furnace bottom exchanging system for exchanging the bottom of the furnace including the tuyere can be implemented.   The above mentioned feather of a converter in which N (N is an integer) tuyere are arranged at the bottom of the furnace so that the distance between the tuyere for use is 500 mm or more and the distance between the tuyere and the fixed hearth is 250 mm or more. In operation using N / 2 or less of the mouths as operating tuyere, when replacing a worn working tuyere, the gas hole of the working tuyere is filled, and the remaining non-working tuyere is used as new working tuyere. A converter tuyere replacement method characterized by the above.

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