JP2007224399A - Bottom-blow tuyere to be used in smelting vessel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bottom-blow tuyere which can more effectively cool a metallic material of the tuyere. <P>SOLUTION: The bottom-blow tuyere is arranged in the bottom of a smelting vessel which accommodates a molten metal; is used for blowing a smelting gas into a smelting vessel therethrough; and has a cylindrical outer pipe and a cylindrical solid inner pipe arranged so that the central axis of the outer pipe matches the central axis of the inner pipe to provide an annular space between the outer pipe and the inner pipe. The outer pipe has such protrusions on the inner wall surface as not to contact with the outer wall surface of the inner pipe. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tuyere (hereinafter referred to as a bottom-blown tuyere) that is disposed at the bottom of a container for containing and refining molten metal and blows a refining gas into the molten metal in the container.

When refining a molten metal, gas may be blown into the molten metal for the purpose of promoting the reaction by stirring. For example, as in the case of decarburization of pig iron in a converter in an iron making process, an inert gas such as argon or nitrogen is blown from the bottom of the converter.
Various types of tuyere are used for blowing inert gas. One of them is a concentric combination of cylinders as disclosed in Patent Document 1, and the inside of the inner tube is made of refractory or the like. There is a type in which gas is blown through a gap between the inner tube and the outer tube (hereinafter referred to as an annular tuyere). This type has an advantage that the structure is simple and the manufacturing cost is relatively low as compared with a capillary tube type tuyere combined with many tubes.

  Generally, when gas is blown from the bottom of a container, if the gas flow rate is reduced at the tuyere, especially when targeting hot molten metal such as molten steel at 1600 ° C or higher, a hot water bottle in which the molten steel flows back into the tuyere There is a risk that the tuyere will be worn out by the phenomenon called. In the case of an annular tuyere, the outer pipe portion having a large heat load from the outside is often melted and worn even though the gas flow rate is larger than the hot water limit flow rate. .

In order to avoid this, a method of reducing the heat receiving area by reducing the thickness of the outer tube is conceivable. However, there is a limit to the amount of reduction in thickness in consideration of strength, and the effect is small.
In addition, by reducing the gap distance between the inner tube and outer tube of the annular tuyere, it is conceivable to increase the heat removal amount by increasing the linear velocity even at the same gas flow rate, but when you want to increase the gas flow rate The upper elasticity of the is limited. In addition, there is a restriction in terms of dimensional accuracy in the manufacture of tuyere hardware that combines an inner tube and an outer tube. Moreover, excessively increasing the linear velocity of the gas may hinder the production of solidified iron (so-called mushrooms) attached to the upper end of the tuyere, which is supposed to help protect the tuyere.

In addition to such a shape of the tuyere, a method of mixing hydrocarbons that decompose at high temperatures and cause an endothermic reaction in the gas to be fed is also conceivable. Equipment is necessary, which is a big investment issue.
JP-A-57-114623

  An object of the present invention is to provide a bottom-blown tuyere that can solve the above problems and can enhance the cooling effect of the tuyere hardware (that is, the outer tube and the inner tube).

  The present invention is a bottom blowing tuyere disposed at the bottom of a refining vessel for containing and refining molten metal, and blows a refining gas into the refining vessel, and has a cylindrical outer tube and a solid cylindrical shape. The inner tube has an inner tube, and the central axis of the outer tube and the central axis of the inner tube are aligned to provide an annular space between the outer tube and the inner tube, and provided on the inner wall surface of the outer tube. And a bottom blowing tuyere having protrusions that do not contact the outer wall surface of the inner tube.

  In the bottom blowing tuyere of the present invention, the inner diameter of the outer tube is preferably 40 mm or more.

  According to the present invention, the cooling effect of the tuyere hardware of the bottom blowing tuyere can be enhanced.

FIG. 1 is a cross-sectional view schematically showing an example of a bottom blowing tuyere of the present invention. The bottom blow tuyere 1 according to the present invention has a refractory 5 disposed around a double pipe structure including an inner tube 2 and an outer tube 3 and inside the inner tube 2. This will be described in detail below.
An inner tube 2 is disposed at the center of the bottom blowing tuyere 1. The inside of the inner pipe 2 is a refractory material.
An outer tube 3 is disposed outside the inner tube 2. The central axis of the inner tube 2 and the central axis of the outer tube 3 coincide with each other, and the outer diameter d ₂ of the inner tube ₂ and the inner diameter D ₁ of the outer tube 3 satisfy the relationship of D ₁ > d ₂ . That is, the inner tube 2 and the outer tube 3 have a concentric double tube structure, and an annular space is formed between the inner tube 2 and the outer tube 3. This annular space becomes a gas flow path.

A protrusion 4 is provided on the inner wall surface of the outer tube 3. By providing this projection 4, the contact area between the outer tube 3 and the gas increases, and the cooling effect can be enhanced.
The protrusion 4 expands the contact area between the outer tube 3 and the cooling gas without hindering the gas flow. Therefore, the tip of the protrusion 4 is not brought into contact with the outer wall surface of the inner tube 2, and the space between the protrusion 4 and the inner tube 2 and the space between the adjacent protrusions 4 are used as gas flow paths.

The shape of the protrusion 4 is not particularly limited. For example, a shape that expands the contact area between the outer tube 3 and the gas, such as a flat (so-called fin) protrusion, a hemispherical protrusion, a rectangular parallelepiped protrusion, or the like may be used.
The number of protrusions 4 is not particularly limited. However, in order to obtain a uniform cooling effect, it is preferable that two or more protrusions 4 are evenly dispersed. That is, it is preferable to arrange two or more protrusions 4 at equal intervals in a cross section perpendicular to the central axis of the outer tube 3 as shown in FIG. In addition, it is preferable that two or more protrusions 4 are arranged at equal intervals even in a cross section (not shown) parallel to the central axis of the outer tube 3.

The upper limit value of the number of protrusions 4 is not particularly limited. What is necessary is just to set according to the dimension of the outer tube | pipe 3 or the inner tube | pipe 2 in the range which does not prevent the distribution | circulation of gas.
The inner diameter D ₁ of the outer tube 3 is preferably not more than 40mm. The reason is that by increasing the inner diameter of the outer tube 3, it is possible to suppress the expansion of gas bubbles in the opening (that is, the portion in contact with the molten metal) and to reduce the wear of the bottom blowing tuyere.

As described above, by providing the protrusion 4 on the inner wall surface of the outer tube 3 of the tuyere metal having a structure in which gas is blown from the annular gap between the outer tube 3 and the inner tube 2, the outer tube 3 and the cooling gas are provided. The contact area can be expanded and the cooling effect can be enhanced.
Since the inner pipe 2 is blocked from heat input from the outer refractory by the gap with the outer pipe 3, the temperature rise is suppressed. In contrast, the outer wall 3 of the outer tube 3 is in contact with the cooling gas, but the outer wall is in contact with the high temperature refractory 5. Therefore, since the temperature of the outer tube 3 is likely to rise due to heat conduction from the refractory, the protrusion 4 is provided on the inner wall surface to enhance the cooling effect. Although protrusions may be provided on the outer wall surface of the inner tube 2, it is preferable not to provide protrusions on the inner tube 2 because there is a concern that the flow of the cooling gas may be hindered.

  Seven types of bottom blow tuyere shown in Table 1 were produced. In the bottom blow tuyere of Invention Examples 1 to 5, protrusions 4 of a rectangular parallelepiped (width 2 mm, height 1.8 mm, installed over the entire length) as shown in FIG. 1 were provided on the inner wall surface of the outer tube 3. No protrusion was provided in the bottom blowing tuyere of Comparative Examples 1 and 2.

First, the bottom blow tuyere of Invention Example 1 was installed in an experimental converter (capacity 5 tons) to decarburize and refine the molten steel. Decarburization refining was performed by blowing N ₂ gas (flow rate: _2.5 Nm ³ / min) as a cooling gas into the molten steel from the annular space between the inner pipe 2 and the outer pipe 3.
When performing decarburization refining, a thermocouple was embedded in the outer wall surface at a position 50 mm from the tip of the outer tube 3, and the temperature of the outer tube 3 when the molten steel temperature reached 1650 ° C. was measured. The result is as shown in FIG. That is, the measured value of Comparative Example 1 to be described later was set as an index (= 1), and was 0.85 with respect to the index.

Next, decarburization refining was performed in the same manner as in Invention Example 1 using the bottom blow tuyere of Invention Example 2 and Comparative Example 1. The temperature of the outer tube 3 is as shown in FIG.
Further, decarburization refining was performed in the same manner as in Invention Example 1 using the bottom blow tuyere of Invention Example 3, and the temperature of the outer tube 3 was measured. The result is as shown in FIG. That is, the measured value of Comparative Example 2 described later was taken as an index (= 1), and was 0.86 with respect to that index.

Next, decarburization refining was performed in the same manner as in Invention Example 1 using the bottom blowing tuyere of Invention Example 4 and Comparative Example 2. The temperature of the outer tube 3 is as shown in FIG.
As is clear from FIG. 2, the temperature of the outer tube 3 was lower in each of the inventive examples 1 to 4 than the comparative examples 1 and 2.
In addition, the result of decarburization refining similarly to invention example 1 using the bottom blowing tuyere of invention example 5 is mentioned later.

Moreover, after decarburization refining was complete | finished, the bottom blowing tuyere of Invention Examples 1-4 and Comparative Examples 1-2 was collect | recovered, and the amount of erosion loss of the outer tube 3 was measured. The result is as shown in FIG. In FIG. 3, the amount of erosion of Invention Examples 1 and 2 is shown as a ratio with the measured value of Comparative Example 1 as an index (= 1), and the amount of erosion of Invention Examples 3 and 4 is the measured value of Comparative Example 2. The ratio is shown as an index (= 1).
As is clear from FIG. 3, Invention Examples 1 to 4 each had a smaller amount of erosion of the outer tube 3 than Comparative Examples 1 and 2.

  FIG. 4 shows the result of collecting the bottom blow tuyere of Invention Example 5 after the decarburization refining and measuring the amount of erosion of the outer pipe 3. In FIG. 4, the measured value of the amount of erosion in Invention Example 5 is taken as an index (= 1), and the amount of erosion in Invention Examples 1 to 4 shown in FIG. 3 is shown as a ratio to the index. As is apparent from FIG. 4, the amount of melting loss in Invention Example 5 was about twice that in Invention Examples 1 to 4. This data shows that the bottom blowing tuyere having an inner diameter of the outer tube 3 of less than 40 mm reduces the cooling effect. However, compared with the amount of erosion of Comparative Example 1 shown in FIG. 3, the amount of erosion of Invention Example 5 is 0.11, and it can be seen that the cooling effect was sufficiently exhibited in the bottom blowing tuyeres of Example 5 of the Invention. .

It is sectional drawing which shows typically the example of the bottom blowing tuyere of this invention. It is a graph which shows the temperature of an outer tube | pipe. It is a graph which shows the amount of molten loss of an outer tube. It is a graph which shows the amount of molten loss of an outer tube.

Explanation of symbols

1 Bottom blowing tuyere 2 Inner pipe 3 Outer pipe 4 Protrusion 5 Refractory

Claims (2)

  A bottom blowing tuyere that is disposed at the bottom of a refining vessel for containing and refining molten metal and blows refining gas into the refining vessel, and includes a cylindrical outer tube and a cylindrical solid inner tube, And an annular space is provided between the outer tube and the inner tube by aligning the central axis of the outer tube with the central axis of the inner tube, and the inner wall surface of the outer tube. A bottom-blown tuyere having a protrusion provided on the outer tube and not in contact with the outer wall surface of the inner tube.   The bottom blow tuyere according to claim 1, wherein an inner diameter of the outer tube is 40 mm or more.

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