JPH0613253Y2 - Blowing tuyere - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a tuyere capable of easily replacing a tuyere damaged during operation of a bottom blowing converter and an upper bottom blowing converter, The present invention relates to a blowing tuyere for a converter, in which a stable effect of improving various characteristics by a bottom blowing tuyere having a twisted double tube bundle can be continuously obtained through one furnace cost.

<Prior Art> Conventionally, a double-tube tuyere is known as a tuyere for blowing, which blows blowing gas from the bottom of the converter into the hot metal contained in the converter. This double tube tuyere consists of an outer tube and an inner tube inserted into this outer tube, and refining gas such as oxygen from the inner tube side, protective gas from the gap between the inner tube and the outer tube, For example, hydrocarbon gas such as propane is blown into the molten iron contained in the converter.

This double tube tuyere has an advantage that the tuyere life is longer than that of the Thomas converter because the protective gas is blown into the molten iron together with the refining gas. However, even when using this double tube tuyere, the furnace bottom refractory near the tuyere opening in the converter gradually wears down as the operation is repeated, and as a result, the furnace away from the tuyere opening is removed. There was a difference in the amount of wear from the bottom refractory, and therefore the life of the bottom depended on the amount of wear of the bottom refractory near the tuyere opening.

On the other hand, during the operation of the converter, the flow rate of the refining gas blown into the molten iron contained in the furnace from the double tube tuyere is selected and determined by the refining time and the steel type. Further, the flow rate of the bottom blowing refining gas is blown in a certain flow rate range for the purpose of improving the metallurgical effect, that is, improving the steel quality even in the same blowing.

Here, a certain flow rate range must be within the maximum flow rate variable range that is almost uniquely determined by the number and diameter of the bottom blowholes. In addition, the maximum flow rate variable range here is the minimum flow rate at which molten iron does not enter the tuyere, and if the bottom blowing gas flow rate is gradually increased, so-called blow-through causes a spitting phenomenon, The maximum flow rate is the limit flow rate that does not reduce the iron yield due to this.

Therefore, it is essential to design the bottom blower mouth so that the range of the maximum and minimum flow rates is wider than the flow rate range required for metallurgical and converter operation. When using the double tube tuyere, there is a problem that the variable width of the bottom blowing gas flow rate is limited within a narrow range and the desired bottom blowing flow rate cannot be achieved.

In order to solve the above problems, a gas refining gas blowing pipe for refining which is improved from a conventional double pipe tuyere is disclosed in JP-A-55-164018. This refining gas blowing pipe was proposed for the purpose of obtaining a double pipe tuyere in which the range in which the gas flow rate can be changed is wide, and as shown in FIG. Twisted collecting tube bundle 6 joined adjacent to
Is twisted at a predetermined angle with respect to the tube axis direction, and the outer tube 7
Is interpolated into. During operation, the refining gas 10 is blown into the molten iron in the converter from the inside of the inner tube, and the protective gas 9 is blown from the gap between the twisted collecting tube bundle and the outer tube. Further, since the twisted collection tube bundle 6 is twisted at a predetermined angle, no blow-through occurs even if a large flow of gas is blown, and
It is also possible to produce a high carbon steel by narrowing the gas flow rate.

However, in the refining gas blowing pipe proposed above, the sum (Sin) of the cross-sectional areas of the inner pipe from which the refining gas is blown out and the cross-sectional area of the gap between the twisted collecting tube bundle and the outer pipe from which the protective gas is blown out. The ratio (Sout / Sin) to (Sout) is about 0.5, and this refining gas injection pipe has a structural restriction that the inner pipe 1 is inscribed in the outer pipe 7. Therefore, the ratio cannot be made lower than that, and there is a drawback that the cross-sectional area of the protective gas blowout part becomes excessively large compared with the ratio of about 0.25 in a normal double tube tuyere. Therefore, the following problems occur.

That is, if the ratio of the protective gas flow rate to the oxygen gas flow rate is set to the same level as that of the normal double tube tuyere, the flow rate of the protective gas becomes about half that in the case of using the normal double tube tuyere. There is a risk that molten iron in the converter will be inserted into the protective gas outlet. On the contrary, if the flow velocity of the protective gas is set to be approximately the same as that of a normal double pipe tuyere in order to avoid such a danger, the protective gas flow rate needs to be about twice as much as the oxygen flow rate, resulting in a high production cost. There is a disadvantage that

Here, in order to solve these problems, a blowing tuyere of a converter in which the above refining gas injection pipe is improved is disclosed in Japanese Patent Laid-Open No. 59-179709.
Japanese Patent Publication No.

This blowing tuyere can mitigate the wear of the furnace bottom refractory near the tuyere opening inside the converter, extend the life of the furnace bottom, and adjust by changing the gas injection amount. Wide range and therefore versatile. Moreover, even if the blowing gas flow rate is increased to perform high-speed blowing to improve productivity, there is no hindrance such as blow-through, and the protective gas flow rate is almost the same as that of a normal double-tuyere. It was proposed for the purpose of providing a tuyere for blowing a converter, which can reduce the cost. The present invention is for blowing a converter as shown in FIG. 5, in which a concentric double pipe 3 consisting of an outer pipe 2 and an inner pipe 1 inserted in the outer pipe is opened at the bottom of the converter. In the tuyere, a plurality of the concentric double tubes are adjacent to each other, and a twisted double tube bundle portion is formed by twisting the concentric double tubes with each other.

In the refining gas blowing pipe disclosed in the above-mentioned JP-A-55-164018, Sout / Sin = 0.5 or less cannot be set as described above, but in this blowing tuyere, Sout / Sin =
Sin can be set arbitrarily and can be set to the same level as that of a normal double tube tuyere.

Further, the following advantages have been found to be obtained by using this blowing tuyere as compared with a normal double tube tuyere. That is, as a result of properly using the above two types of tuyeres in a 5t scale converter, the average tuyere erosion rate was 0.6mm / charge, average of 1.4mm / charge for a normal double tube tuyeres. The iron yield was 91.5% compared to 80.8% for a normal double tube tuyere.

<Problems to be Solved by the Invention> However, even when the converter tuyere disclosed in Japanese Patent Laid-Open No. 59-179709 is used, the tuyere's melting loss progresses as the operation is repeated, It was found from the experimental results of the present inventors that local tuyere melting may occur. That is, when many tuyeres are buried in the furnace bottom,
The protective gas is supplied from the protective gas branch pipe (header) at the bottom of the furnace to the tuyere, but the solidified iron (mushroom) at the tip of the tuyere
Pressure loss in the protective gas pipe of each tuyere due to the size of the tuyere or the porosity in the solidified iron fluctuates due to the progress of blowing or operation, and the production and decline of mushrooms in each tuyere are uneven. And the pressure loss of the protective gas pipe of each tuyere becomes different. This causes a difference in the flow rate of the protective gas at each tuyere, which makes the tuyere cooling non-uniform, resulting in a different melting loss rate between the tuyere.

When falling into such a state, the life of the hearth is limited by the tuyere with a high melting rate, the life of the hearth becomes short, and stable converter operation becomes impossible.

As a technique for avoiding this trouble, there is a method of controlling the protective gas flow rate for each tuyere and increasing the flow rate of the protective gas in the tuyere having a high melting loss rate. In carrying out this method, not only the equipment needs to be remodeled greatly but also the equipment cost is increased, and even in the case of a large-scale converter having a large number of bottom blown tuyeres, it is difficult to even remodel the equipment. Therefore this method is not practical.

As another countermeasure technique, there is a method of pulling out the tuyere with a high rate of erosion and pulling it from the furnace bottom, and then plugging or inserting a new tuyere to restore the tuyere. This method is economically advantageous because it can be carried out relatively easily and without large-scale equipment. Here, in the method of pulling out the tuyere from the bottom of the furnace, as a result of an experiment in a 5t-scale converter, it is possible to pull out the tuyere relatively easily in the case of a normal double-tube tuyere. In the case of a tuyere consisting of a twisted double tube bundle in which a number of heavy tubes are twisted together, the pullout resistance is 4 to 7 times higher than that of a normal double tube tuyere, and not only can it not be pulled out easily. However, there is a problem that the tuyere itself is broken in the middle due to its resistance, and it takes a lot of labor to remove the tuyere remaining in the furnace bottom refractory.

As described above, in order to maintain the effect of stable characteristics improvement by the blowing tuyere of the twisted double tube bundle in which a large number of the above-mentioned concentric double tubes are twisted, it is necessary to pull out The development of an easily twistable double tube bundle is an essential issue.

The present invention is a tuyere for the twisting double tube bundle, which has a large variable range of the bottom blowing flow rate, and can achieve a high iron yield and a low tuyere melting loss rate. The purpose of the present invention is to provide a blowing tuyere for a converter in which the damaged tuyere can be easily replaced during operation of the furnace.

<Means for Solving the Problems> The present invention is a tuyere for blowing that is formed by opening a concentric double tube consisting of an outer tube and an inner tube inserted in the outer tube below the bath surface. , A plurality of the concentric double tubes are adjacent to each other, and a twisted double tube bundle in which the concentric double tubes are twisted together is inserted into a metal outer cylinder, and the twisted double tube bundle is A concentric double tube consisting of an outer tube and an inner tube inserted into the outer tube, or a tuyere for blowing, characterized in that the gap between the outer tube and the metal outer tube is filled with a refractory material. In a blowing tuyere opened below the bath surface, a plurality of concentric double tubes are adjacent to each other, and a twisted double tube bundle formed by twisting the concentric double tubes is columnar. It may be a tuyere for blowing, which is characterized in that it is enclosed in the refractory material. Further, the refractory material described in 1 and 2 above is a blowing tuyere which is a magnesia-based refractory material containing 5 to 40% by weight of carbon (hereinafter abbreviated as%).

<Operation> As a tuyere for the blowing of a converter, a large number of concentric double tubes are adjacent to and joined to each other, and a twisted double tube bundle is formed by twisting these concentric double tubes with each other. Since the tuyere is used as the tuyere, the range that can be changed by adjusting the gas flow rate can be widened as compared with the conventional double-pipe tuyere as in the previously filed invention of the applicant, and different steel types can be melted in the same converter. Can be manufactured. Also, it is possible to reduce the wear of the furnace bottom refractory near the tuyere opening in the converter and extend the furnace bottom life, and increase the blowing gas flow rate to perform high-speed blowing to improve productivity. However, blowout, spitting, etc. will not occur and the yield will not be reduced.

Furthermore, the ratio of the oxygen blowing section cross-sectional area to the protective gas blowing section cross-sectional area can be set arbitrarily, and it is possible to make it approximately the same as that of a normal double pipe tuyere. Compared with the case of using the double tube tuyere, there is no need to increase the number, and the production cost can be reduced, which is advantageous.

In the present invention, the tuyere structure as shown in FIGS. 1 and 2 is installed in the converter in order to maintain the above advantages through the furnace cost. That is, the tuyere of the twisted double tube bundle is inserted into a metal outer tube and the gap between the tuyere of the twisted double tube bundle and the metal outer tube is filled with a refractory material, or the twisted double tube bundle is twisted into a cylindrical refractory material. We adopted a form in which the tuyere of a heavy tube bundle was buried and stored. Therefore, if the tuyere melting loss progresses locally during the converter operation, it is possible to easily pull out the tuyere with significant melting loss and replace the tuyere by plugging or inserting a new tuyere into the furnace bottom. In addition, the life of the bottom of the furnace is not limited by the tuyere of significant melting loss, and the effect of improving the various characteristics of the tuyere of the twisted double tube bundle can be maintained through the furnace cost, making the converter stable and economical. Can operate.

The adoption of a MgO-C refractory material having a carbon content of 5 to 40% as a refractory material makes it possible to have excellent spalling resistance and to withstand erosion of slag by improving thermal conductivity. Therefore, it is possible to suppress a decrease in the life of the tuyere due to the wear of the refractory near the tuyere, and it is possible to achieve stable and economical operation of the converter.

<Example> An example of the present invention, which was carried out by using the upper-bottom blowing converter having a furnace capacity of 5 ton shown in Fig. 3, is shown below.

Prior to the operation, in this embodiment, the bottom blown tuyere shown in FIG.
It was attached to the bottom of the furnace. Here, as the cylindrical refractory material shown in FIG. 2, a MgO—C based refractory material of MaO: 72% and C: 20% was adopted. The operation was carried out by charging about 5 tons of molten iron into the converter and then blowing it a total of 15 times under the operating conditions shown in Table 1.

Table 2 shows the temperature and composition of molten steel at the time of tapping in 15 times of blowing.

Of the 15 blows, after the 6th blow was completed and the molten steel was tapped, when observing the bottom of the furnace, one of the four bottom tuyeres compared to the other tuyeres. It was confirmed that the melting loss was progressing abnormally at 60 to 70 mm. Therefore, the tuyeres were immediately pulled out, new tuyeres were inserted, and from the seventh blowing, the operation was resumed with four tuyeres again.

Also, when pulling out the tuyere, the load cell measured the pull-out resistance, and a maximum load of 340 kgf was detected, but the tuyere restoration work can be performed smoothly without any trouble such as breakage of the tuyere itself. It took about 55 minutes from pulling out to reviving.

Average tuyere erosion rate of 0.65 mm / through 15 blowing experiments
The charge and average iron yield were 91.6%.

The comparative example was carried out by using exactly the same equipment and operating method as the example, but the tuyere having the structure shown in FIG. The blowing experiment was conducted 8 times, and the temperature and the composition of components at the time of blowing were adjusted so as to be the same as those in the examples. At the time of completion of the eighth blowing, it was confirmed that one of the four tuyere had an abnormal progress of erosion of 70 to 90 mm as compared with the other tuyere, so that the example I tried to replace the tuyere as well.

However, when the tuyere was pulled out, the welded portion of the tuyere and the tuyere flange was broken, and the tuyere body was left behind in the furnace bottom refractory. For this reason, it became impossible to remove the melted tuyere, and the blowing after the ninth time was abandoned. Here, the breaking load was 2470 kgf, which was about 7 times that in the example.

Also, the average tuyere erosion rate through the 8 blowing experiments was 0.
93mm / charge, average iron yield was 91.4%. Thus, the iron yield is not different between the example and the comparative example,
The tuyere erosion rate is significantly different depending on whether or not the tuyere is replaced.

As described above, according to the present invention, the tuyere structure is embedded in a columnar refractory material and then installed on the bottom of the converter to extract the damaged melted tuyere. It becomes easier and the life of the hearth is not limited by the damaged melted tuyere. Therefore, it is possible to maintain the effect of improving various characteristics of the tuyere, in which a large number of concentric double tubes are adjacent to each other, and the double tubes are twisted together to form a twisted double tube bundle, through the furnace cost, It enables stable and economical operation of the converter.

<Advantages of the Invention> When the blowing tuyere according to the present invention is used, it becomes possible to easily replace the melted tuyere damaged during the operation of the bottom blowing converter and the upper bottom blowing converter. The effect of improving various characteristics by the tuyere forming the twisted double tube bundle can be maintained through the furnace cost, and safe and economical operation of the converter can be realized.

[Brief description of drawings]

1 and 2 are drawings of a blowing tuyere of a converter according to the present invention, in which (a) is a side sectional view and (b) is A- of (a).
A sectional view, FIG. 3 is a schematic view of an upper-bottom blowing converter in which the present invention is implemented, and FIGS. 4 and 5 are drawings of a blowing tuyere of a conventional converter. ) Is a side sectional view, (b) is B- of (a)
It is a B sectional view. DESCRIPTION OF SYMBOLS 1 ... Inner tube, 2 ... Outer tube (of concentric double tube), 3 ... Concentric double tube, 4 ... Metal outer tube, 5 ... Twisted double tube bundle, 6 ... Twisted collecting tube bundle, 7 ... Outer tube, 8 ... Refractory material, 9 ... Protective gas, 10 ... Refining gas, 11 ... Converter body, 12 ... Bottom blown tuyere, 13 ... Molten iron, 14 ... Top blown oxygen lance, 15 ... Flux tank, 16 ... Flange.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshikazu Sakuraya 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Division (72) Tetsuya Fujii 1 Kawasaki-cho, Chiba-shi Kawasaki Steel Co., Ltd. Mari Okada, Examiner, Research Division

Claims (3)

[Scope of utility model registration request] 1. A blowing tuyere comprising a concentric double tube consisting of an outer tube and an inner tube inserted into the outer tube, the tuyere being a plurality of the concentric double tubes. The tubes are adjacent to each other, and the twisted double tube bundle in which the concentric double tubes are twisted together is inserted into the metal outer cylinder, and the gap between the twisted double tube bundle and the metal outer cylinder is fireproof. A tuyere for blowing, characterized by being filled with a conductive material. 2. A blowing tuyere formed by opening a concentric double tube consisting of an outer tube and an inner tube inserted in the outer tube below the bath surface, and a plurality of the concentric double tubes. A tuyere for blowing, characterized in that a twisted double tube bundle in which the tubes are adjacent to each other and the concentric double tubes are twisted together is enclosed in a columnar refractory material. 3. A tuyere for blowing, wherein the refractory material according to claim 1 or 2 is a magnesia refractory material containing 5 to 40% by weight of carbon.