JPS5848616A - Cooling method for tuyere of refining vessel - Google Patents

Abstract

PURPOSE:To cool the concentrical double-ply pipe tuyeres installed under the surface of a molten iron bath and to protect the same against erosion by running a fluid mixture of CO2 and a fine particle carbon material contg. alkaline metal components as protecting fluid in the annular flow passage on the outer side of said tuyeres. CONSTITUTION:In order to cool and protect the concentrical double-ply pipe tuyeres which are installed on the bottom of a converter and run gaseous oxygen for refining through the central flow passage, a fluid mixture of CO2 and a fine particle carbon material carrying 0.1-2.0% alkaline metal components is used as the protecting fluid to be run in the annular flow passage on the outer side of the central flow passage. Inexpensive coke powder and the like are suited for said fine particle carbon material. The alkali metals are carried in the carbon material by spraying an aq. soln. of alkali salt of NaCl or the like on coke powder or the like then drying the same. In the molten iron the alkali metals act as a catalyst and the endothermic reaction of CO2+C 2CO progresses quickly, whereby an effective cooling effect is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention proposes a cooling method that is particularly advantageous for cooling concentric double pipe tubes installed at the bottom of a bottom-blown converter.

Oxygen bottom-blown converter has better stirring and mixing than LD converter, and Il! It has advantages in terms of shortening the opening time for steel, improving alloy yield, and improving iron yield. However, since the tuyeres are located below the bath surface, it is difficult to cool the tuyere itself, and the conventional method generally used is to use concentric double pipe tuyeres, and the outer annular flow is A hydrocarbon-based gas such as propane is passed through the pipe, and the heat absorbed by the decomposition of the hydrocarbon-based gas is used to cool and protect the siding. The disadvantage of this prior art is that hydrogen remains in the steel after decomposition of hydrocarbons, resulting in LD
Compared to a converter, the hydrogen content in the steel is 2 to J ppIII higher.

There is also a technology that uses CO2 as a tuyere protective fluid.However, unlike the aforementioned propane, the cooling effect of CO2 does not involve a decomposition reaction, so it does not have the same heat removal effect as blowing argon or nitrogen. Kana (According to the inventors' calculations, 13 to 7% CO2 gas is required in terms of 0 body tank%,
Since it is essential to use a large amount of 002, it has the disadvantage of being expensive.

This invention aims to overcome the drawbacks of the above-mentioned tuyere cooling technology, and overcomes the above-mentioned drawbacks by using a mixed fluid of CO, c fine powder, and alkali metal as a protective fluid. It is. The details of the configuration will be explained below.

The present invention is based on the use of a mixed fluid of CO2 gas and carbon particles as a protective fluid (cooling gas). When such a mixed fluid is used, C in the high temperature area in front of the tuyere tip
Since an endothermic reaction of o2+C-+200 occurs, the heat removal performance is dramatically increased compared to the conventional method in which Co2 alone is injected into the molten metal as a cooling gas.

However, the above endothermic reaction rate is not so large;
The solid carbon to be mixed in will not work effectively as a siding coolant unless the reaction progresses during the short time it passes through the siding tip, so conditions such as the need for extremely small particle size are imposed. .

In order to solve this problem, the present invention proposes that if an alkali metal is added to solid carbon as a catalyst, C02+C-+
This method was developed with a focus on the fact that the reaction rate of λOO becomes extremely high.In particular, by adopting this method, restrictions on the type and particle size of carbon materials, which previously could not be used when the reaction rate was high, can be relaxed. This makes it possible to perform tuyere cooling easily and economically.

There are many types of solid carbon currently available. These are used for a variety of purposes and have different properties and prices. The conditions for the solid carbon used for tuyere cooling, which is the object of the present invention, are that it must be large enough to pass through the gaps formed in the pine mushrooms at the tip of the tuyere, and that it must be of a large size with an average particle size of 100 μm or less, and must react quickly with CO8. From the viewpoint of reaction rate, an average particle size of 10
Solid carbon with a particle diameter of less than μ is considered to be effective for tuyere cooling, and suitable carbon black produced by decomposition of gaseous carbonized tree leaves or finely pulverized activated carbon are suitable. However, such carbon black and the like are not only difficult to transport and expensive, but also have some problems in that their use as a tuyere coolant increases the cost of producing iron.

Therefore, in the present invention, solid carbon having a large particle size can be used by using an alkali metal as a catalyst for the reaction between solid carbon and 002. If an alkali metal is added to solid carbon such as coke, the result is shown in Figure 1.

As shown in Figure 2, the reaction rate with CO2 increases rapidly, and as can be seen from the relationship between the reaction rate and the alkali metal addition edge shown in Figure 2, the addition of a certain amount of alkali metal dramatically increases the reaction rate. . As is clear from the drawing, the reaction rate increases when the weight ratio of alkali metal is 0.01%.
That's all. Moreover, it can be seen that the effect has reached a plateau at 2% or more. In this way, if 0.0/% to 2% of alkali metal is added to coke powder, the reaction with CO2 M! Even with coke having an average particle size of lOOμ, a reaction rate comparable to that of carbon black having a particle size of several μm can be obtained. Note that there is no need to particularly limit the method of adding the alkali metal; for example, Na04 #K
An alkali salt such as OI, NaOH, or KOH may be dissolved in water, and the solution may be sprayed onto solid carbon such as coke and then dried to entrain it.

Next, embodiments of this invention will be described.

A demonstration example is an example in which a blowing experiment was conducted using a 11-test converter. The following is a typical example of blowing conditions under the same conditions except for the type of carbon injected from the tuyere.

Hot metal amount s j t, s hot metal component: ”/li, s%, 5
110.3! %, Knlo, zo%s X'10. /l
o%s S10. oz2%s blowstop 1010, os%, temperature ttso℃, hearth tuyere &! 1 piece, hot metal temperature/JJO
°C, oxygen delivery rate/2. I Mm”/win (total amount bottom blowing), 00g ratio c to 0□)s%, carbon addition device 002
! 10 = / (molar ratio).

The results of blowing under the above conditions are shown in Table 1. 〇Table 1 - Coke ratio when sprayed with KOj aqueous solution. This is made by crushing coke powder with a ball mill to adjust the particle size. The alkali metal to be added is KO! The reagent was dissolved in water to make a specified aqueous solution, and the aqueous solution was evenly sprayed onto the coke to add the desired filter.Table 1 shows the results of continuous spraying with S heat under the same conditions, and the tuyere melting. This is a comparison of the average amounts.

As shown in the comparative example, if no alkali metal is added, coke with an average particle diameter of μ causes large tuyere melting, so it cannot be used as a substitute for acetylene black even though it is available at a low price. .

As can be seen from Table 1, when alkali was added to increase the reaction rate with CO2, even coke showed a tuyere cooling effect almost equivalent to that of acetylene black, even though the particle size was large.

As explained above, according to the present invention, tuyere cooling can be performed easily and economically, and inexpensive solid carbon can be used as the tuyere coolant, so that steel manufacturing costs can be reduced.

[Brief explanation of the drawing]

The m/diagram in the drawing is a characteristic diagram of the C02→200 reactor associated with potassium addition, and FIG. 2 is a diagram showing the relationship between alkali addition and reaction rate. Patent applicant Kawasaki Steel Corporation Figure 1 Temperature cliff q5θ Figure 2

Claims (1)

[Scope of Claims] 1. For cooling the concentric double pipe siding that allows oxygen gas for the M weight to flow from the center channel installed below the surface of the molten iron bath in the refining vessel, an annular channel outside the center channel is used. In the method of cooling the tuyere by flowing a protective fluid, the protective fluid contains C02 and 0.5% by weight. /~λ・
A method for cooling a tuyere characterized by using a mixed fluid with a fine carbon material containing 0% alkali metal.