JPH06100921A - Tuyere for metal refining furnace - Google Patents

Abstract

PURPOSE:To prevent the damage of a tuyere and a furnace bottom part by constituting the tuyere for metal refining furnace of a triple pipe, embedding the outermost pipe into a furnace wall part and arranging a gas permeable porous body on the peripheral part of an inner pipe at the outside of a center pipe projecting to the inside of the furnace. CONSTITUTION:By blowing combustion assistant gas of C3H8, etc., together with O2 from the tuyere in the furnace bottom part of the metal refining furnace, the refining is executed. This tuyere is constituted of the triple pipe and O2 from the center pipe 32 and C3H8 from the inner pipe 40 are blown, and further, C3H8 for cooling is blown from the outermost pipe 42. The outermost pipe 42 is substantially embedded into the furnace wall part 29, and the inner pipe 40 and the center pipe 32 are set so as to project to the inside of the furnace. Further, the gas permeable porous body 30 is arranged on the outer periphery of the inner pipe 40 so as to stick to at least the tip part thereof and cover the tip part of the outermost pipe 42 and its surrounding part. By this method, the porous body 30 as an artificial mushroom together with the inner pipe 40 are protected by cooling, and the damage the tuyere and the refractory of the furnace wall part 29 around the tuyere can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to tuyere of a metal refining furnace such as a steelmaking converter and a smelting reduction furnace for iron. More specifically, it relates to tuyere for blowing gas and / or powder into molten metal contained in a metal refining furnace.

[0002]

2. Description of the Related Art A steelmaking converter, which is a typical example of a metal refining furnace, will be described below.

As a steelmaking converter, in recent years, in addition to a top-blown oxygen converter, a bottom-blown converter for blowing gas from the bottom has been widely used. According to this, the slag and molten steel are sufficiently stirred by blowing the gas for stirring the steel bath from the bottom of the furnace, while the amount of FeO generated in the slag by the oxygen gas blown from the upper part is reduced. There is an effect, and thereby the yield can be improved.

The gas supply port for stirring the molten steel is called a tuyere, which usually has a steel pipe structure. Such tuyere is always cooled with nitrogen gas or the like to prevent melting damage. In particular, in the process of blowing oxygen or a mixed gas mainly containing oxygen from the bottom of the furnace, as a method of extending the life of the bottom blowneck that blows such gas, a gas passage for cooling is provided outside the pipe into which the gas is blown. Multi-tube tuyeres consisting of so-called double or triple tubes are used.

Thus, the cooling of the tuyere is of the utmost importance, and in any structure, sufficient cooling must be performed in order to stably extend the life of the tuyere. Therefore, as a cooling gas for such multi-tube tuyere, propane gas having a large endothermic amount due to thermal decomposition is generally used, including an inert gas. There is also a process that uses kerosene or CO ₂ gas instead of propane gas,
Also in this case, the tuyere is cooled by utilizing the endothermic reaction accompanying the same decomposition reaction.

FIG. 3 is a schematic explanatory view schematically showing a state where oxygen gas and propane gas are blown into the molten steel (1200 to 1650 ° C.) from the double pipe 12 of the multi-tuyere 10. In the figure,
Propane gas blown from the outer gas passage 14 partially decomposes and absorbs heat in the passage, and H ₂ which is the final decomposition product.
And C react with O ₂ gas in the molten steel to generate CO and H ₂ O gas, and stir the molten steel. The reaction at this time can be described as follows. C ₃ H ₈ → 3C + 4H ₂ endothermic reaction C + 1 / 2O ₂ → CO exothermic reaction H ₂ + 1 / 2O ₂ → H ₂ O exothermic reaction However, since the above gas generation reaction is an exothermic reaction as a whole, The temperature near the mouth and outlet becomes extremely high, and melting loss is likely to occur. Further, when such a gas forms bubbles and leaves the tuyere tip, a back attack occurs due to the elasticity of the bubbles. On the brick surface, the stress due to the back attack is directly received. In addition, a large temperature gradient is generated by heating from the side surface and the upper surface and cooling from the tuyere, and thermal stress is further applied to the brick surface. It is presumed that a crack is generated on the brick surface due to these stresses, slag metal further enters the crack, and the crack propagates.

On the other hand, as shown in FIGS. 4 and 5, the gas produced by decomposing these cooling gases supercools the molten steel to produce a solidified material called mushroom 20 above the tuyere. At this time, even if small mushrooms start to form, the cracks cause the refractory to peel off, and at the same time the mushrooms melt away or fall off. Due to these repetitions, the tuyere and surrounding refractories are damaged, but when the damage depression becomes large to some extent, a stagnant zone (dead zone) of molten steel is created and the heat supply by molten steel convection decreases, as shown in Fig. 5. Mushroom 20 grows big. The gradual growth of this mushroom protects the tuyere and the refractory material around the tuyere.

That is, in FIG. 4, a small mushroom 20 is first generated in the vicinity of the outlet of the outer gas passage 14, and then this grows into a large mushroom 20 as shown in FIG. Until such mushrooms are formed, the refractory around the tuyere cracks due to the back attack when CO and H ₂ O gas are generated, as shown in Fig. 3, and further heat stress is applied, slag, metal, etc. Thermal damage occurs due to the formation of an intrusion layer, and the refractory in that portion is peeled off to form a refractory erosion area 13 as shown by the shaded area in FIG.

As described above, in the early stage of operation of the furnace, the cooling gas is decomposed at the tip of the tuyere metal to enter the molten metal with only the tuyere metal and no mushroom, and the supplied oxygen is supplied to the portion in contact with the molten steel. Will react with.

Therefore, in order to prevent damage to the tuyere and refractory around the tuyere at the beginning of the operation of the furnace, it is necessary to prevent the invasion of slag metal and protect the surrounding bricks. Once you have mushrooms 20 as shown in Figure 5,
There is no concern about such heat damage, and the tuyere can have a long life. However, the damage to the tuyere and surrounding refractories up to that point cannot be recovered. As described above, the lifetime of the tuyere and the refractory material around the tuyere is controlled by the mushroom formation, and a rapid method for producing healthy mushrooms is important for prolonging the tuyere life.

For example, in the method disclosed in Japanese Unexamined Patent Publication No. 62-109918, a double or triple tube is used, and a mixed gas of propane gas and CO ₂ gas is supplied from the outer tube and the inside of the furnace is supplied. Trying to quickly form mushrooms.
However, in actual operation, the molten steel is cooled in the operation process,
It is difficult to quickly generate mushrooms, which are breathable coagulates, and some damage to refractories is unavoidable, and it has been considered that the tuyere life can be extended accordingly.

Further, when there is no molten metal in the initial stage, such as when scrap is melted or ore is reduced to produce pig iron, it is particularly difficult to produce mushrooms and the tuyere damage is large in the initial stage of refining.

[0013]

SUMMARY OF THE INVENTION The object of the present invention is to provide a mushroom non-formation timing at the beginning of furnace operation at a multi-tube bottom blowhole installed on the bottom of a metal refining furnace, which is a drawback of the conventional method. The present invention is to provide a tuyere that prevents damage to the tuyere and the furnace bottom part around the tuyere and enables a long life of the tuyere.

In order to achieve the above object, the inventor of the present invention, when cooling is performed by providing multiple pipe tuyeres at the bottom of a metal refining furnace, the damage is caused by the mushroom non-production period and the unstable period in the initial operation of the furnace. Focusing on the fact that the mushrooms are concentrated in the area, the idea is to install the artificially formed mushrooms from the beginning to protect the tuyere and extend the service life. Patent application was filed as -68573.

Certainly, according to such a method, the durability around the tuyere can be markedly improved and the life can be prolonged as compared with the conventional method, but in the converter actually used, 30 charges are blown per day. Smelting is not uncommon, and it is used continuously for 1000 charges or more. However, it was found that even if the above-mentioned tuyere is used, the tip end of the pipe of the combustion-supporting gas (O ₂ , Air, etc.) will be melted if the number of charges is increased.

That is, as shown in FIG. 6 (a), the protective action is sufficiently observed up to about 30 charges, but when the charge exceeds 30 charges, melting loss is observed at the mushroom tip as shown in FIG. 6 (b). Will be available. When the melting loss progresses as it is, the melting loss of the central tube 14 also progresses as shown in FIG. 6 (c), and finally the furnace wall is damaged as shown in FIG. 6 (d). Become. Therefore, a more specific object of the present invention is
It is an object of the present invention to provide a metal refining furnace tuyere structure capable of minimizing damage to the refractory and tuyere even during such long-term use.

[0017]

Therefore, as a result of further studying this point, the present inventor completed the present invention with the following findings. Since the combustion-supporting gas also reacts with [C] in the metal as shown in the reaction formula of 2 [C] + O ₂ → 2CO (exothermic reaction),
Increasing the amount of heat received at the tip of the combustion-supporting gas pipe is inevitable.

However, the cooling by the artificial mushroom as described above is performed almost uniformly. Therefore, the tip of the pipe for the combustion-supporting gas is easily melted with the passage of time.

Therefore, another one is placed around the combustion-supporting gas pipe.
If multiple pipes for passing cooling gas are installed and the outside is protected by a gas permeable porous material such as porous metal and / or refractory, protection of flammable gas piping and surrounding refractories at the beginning of operation Provides both protection and a long-lasting tuyere.

The present invention is a tuyere of a metal refining furnace composed of triple tubes, in which the outermost tube is substantially buried in the furnace wall and the inner tube and the central tube are projected inside the furnace. A metal refining furnace tuyere provided with a gas-permeable porous body that is adhered to the outer circumference of the inner tube at least at its tip and covers the tip of the outermost tube and its periphery. .

According to a preferred embodiment of the present invention, the gas permeable porous body has an opening at the center so that the inner tube and the central tube can pass therethrough, and is generally the same as or close to the mushroom described above. It is composed of a porous refractory or metal through which a morphological cooling gas passes.

[0022]

1 is a schematic sectional view showing an example of a tuyere according to the present invention, and FIG. 2 is a schematic explanatory view showing a gas supply system to the tuyere together. As shown in the figure, a metal refining furnace tuyere 28 composed of a triple tube according to the present invention includes an outermost tube 42 which is substantially buried in a furnace wall 29, and an inner tube 40 which is installed so as to project inside the furnace. And a central tube 32, and a gas-permeable porous body 30 provided so as to adhere to the outer circumference of the inner tube at least at its tip and cover the tip of the outermost tube.

In the illustrated example, the outermost tube 42 also partially projects inside the furnace, but it is extremely small compared to the inner tube and the central tube, and the amount of projection is fixed to the porous body 30. This is to facilitate. Therefore, as long as appropriate fixing means are provided, such protrusion is not necessary and may be installed in a state of being completely embedded in the furnace wall as shown in FIG. However, preferably, the porous body 30 is also provided with a fitting portion 31 for fitting with the outermost tube at the bottom portion thereof, and correspondingly, a projecting portion is also provided for the outermost tube.

Whole mushroom type gas permeable porous body 30
Has some resistance to molten metal,
Any so-called porous metal or ceramic may be used as long as it is gas permeable.

A central tube 32 is provided at the center of the porous body 30, and an inner tube 40 is provided at the outer side of the central tube 32.
As can be seen from Fig. 2, this is the central hole of the multi-tuyere.
It is arranged concentrically with respect to 34. Nozzle holes 38 for cooling gas provided around the central hole 34 of the multi-tube tuyere project to the inside of the furnace by the same distance as the central hole 34,
Further, a nozzle hole 36 for cooling gas is provided around it. The periphery of the nozzle hole 36 is covered with the porous body 30 described above.

The cooling gas exits from the nozzle hole 36, passes through the porous body 30, and is discharged into the molten steel. At this time, the release area, that is, the outer surface of the porous body expands toward the inside of the furnace, so the chances that the cooling gas released from the outer surface will contact the oxygen gas from the center hole is significantly reduced, and The rapid reaction between the product and oxygen gas is prevented.

The porous body 30 constituting the tuyere according to the present invention
Is a metal or refractory, and a large number of small holes may be mechanically formed, but a sintered body by a powder metallurgy method, and in the case of metal, a foamed metal is more preferable.
Also, an aggregate of ceramic fibers having pores in the fibers, that is, ceramic foam is put in a mold,
If a metal is cast on it to make it, the porous body can be manufactured relatively easily, and the protective member can be made at low cost. In this case, the porous body consists of metal and ceramic foam.

As the metal component, iron having a carbon concentration of 0.5 to 3.5%, which is lower than that of hot metal, as in natural mushrooms,
Steel is desirable, and other components may be used as long as they do not adversely affect refining. Cast iron or the like is preferable, but heat resistant steel such as stainless steel may be used.

Further, the refractory material is magcarbon mainly composed of MgO, magdoro, magro brick or the like. The porosity is preferably 5 to 50 pores / cm ² and a pore diameter <0.6 mm.

The shape of the porous body 30 is not particularly limited and has a through hole through which the central tube 32 and the inner tube 40 are installed,
The structure is not limited to a specific structure as long as it is in close contact with the outer periphery of the inner pipe 40 at least at its tip and covers the cooling gas nozzle hole 36 and its peripheral portion. Here, the "peripheral portion" means a region where at least melting of the refractory is observed during the so-called mushroom non-generation period.

Moreover, in general, in order for the gas to flow more uniformly in the porous main body 30 as shown in FIG. 1, a shape close to a semi-spherical shape is preferable. In addition, the cross section may be trapezoidal, rectangular, or conical.

As shown in FIG. 2, in actual operation, a stirring gas (O ₂ ) is blown from the bottom blowing tuyere center hole 34, and a cooling gas such as propane gas is blown from the nozzle holes 36 and 38, respectively. Cooling gas from the nozzle hole 36 (e.g. propane gas) is thermally decomposed in the porous body 30 to cool the porous body, while cooling gas from the nozzle hole 38 (e.g. propane gas) It is cooled by causing a decomposition endothermic reaction at the tip of the central tube 32. Thus, the multi-tube tuyere hardware and the surrounding refractory material are protected. As described above, the fixing means for the porous body 30 is not limited to a particular one, but, for example, as shown in FIG.
(C ≦ 2%) or a refractory material or a mixture thereof to configure the central tube 32, the inner tube 40, and the outermost tube 42 of the multi-tuyere, and pre-screw the tips of the inner tube 40 and the outermost tube 42. The inner and outermost pipes of this multi-tube tuyere are provided so as to project into the furnace, and the inner and outermost pipes are fitted with through-holes. Similarly, the porous body 30 that has been threaded may be screwed into. At this time, it is preferable to provide a kind of gas reservoir 44 in the porous body so as to surround the inner tube 40 as shown in FIG.

[0033]

EXAMPLE Under the refining conditions shown in Table 1, a bottom-blown triple tube tuyere according to the present invention shown in FIG. The weight of the porous material is C: 1.67, S
i: <0.01, P: 0.050, S: 0.004, Mn: 0.30, the balance of Fe metal is cast into a ceramic foam,
The pore diameter was 0.15 to 0.3 mm, and the number of pores was 35 to 50 / cm ² . The dimensions were 80 mm high and 160 mm in diameter.

Table 2 shows the operation results of the conventional example and the comparative example. In the comparative example, the same porous material was used, but Japanese Patent Application No.
The double pipe tuyere shown in −68573 was used. This corresponds to the structure shown in FIG.

As a result, mushrooms having a diameter of about 120 mm were formed after 30 charges even in the tuyere in which the porous member was not provided as a protective member as in the conventional case, but the tuyere had an average length with respect to the initial tuyere length. There was damage of 0.28mm / ch. In the comparative example, the initial tuyere length was damaged by 0.19 mm / ch, and the protective member initially attached was sound, and the bricks around the tuyere were hardly damaged.

However, in the comparative example, wear increases as the number of charges increases, but in the triple tube tuyere according to the present invention, cooling near the tuyere is dramatically increased, so that low wear can be maintained. Therefore, according to the present invention, it is understood that the low wear amount is maintained for a long period of time. The carbon content at the time of tapping in this example was 0.05%, and the temperature was 1660 ° C.

[0037]

[Table 1]

[0038]

According to the present invention, it is possible to extend the life of the bottom blowing tuyere, which is an important element of the upper bottom blowing converter, by a simple means, and the cost merit is great. It can be said that the present invention has a great practical advantage.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a tuyere structure according to the present invention.

FIG. 2 is a schematic sectional view showing a tuyere structure according to the present invention together with a gas supply system.

FIG. 3 is a schematic explanatory view of the state of gas injection from a bottom-blown tuyere that has been conventionally observed.

FIG. 4 is a schematic explanatory view of how the refractory near the bottom blowing tuyere is damaged.

FIG. 5 is a schematic explanatory view of a so-called mushroom that is also formed on the front surface of the tuyere.

6 (a) to 6 (d) are shown in Japanese Patent Application No. 3-68573.
FIG. 7 is a schematic explanatory view showing the manner of wear of the refractory near the tuyere disclosed in No.

[Explanation of symbols]

 28: Metal refining tuyere 29: Furnace wall 30: Gas permeable porous body 32: Center tube 34: Center hole 36: Nozzle hole 38: Nozzle hole 40: Inner tube 42: Outermost tube

Claims (1)

[Claims] 1. A metal refining furnace tuyere composed of triple tubes, wherein the outermost tube is substantially buried in the furnace wall, and the inner tube and the central tube are installed so as to project inside the furnace, and A metal refining furnace tuyere provided with a gas-permeable porous body which is closely attached to the outer periphery of the tube at least at its tip and covers the tip of the outermost tube and its periphery.