JPH03183714A - Method for restraining wearing of refractory in metallurgical furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is applicable to a furnace that uses a large amount of oxygen and utilizes its exothermic action to perform metallurgical operations such as melting and reduction, such as melting and reducing iron ore. In particular, the present invention relates to a method for suppressing the wear of refractories above the molten material surface, which is a problem.

(Prior art) In a steel manufacturing method using normal oxygen, such as a converter method,
Seven lacs such as quicklime and calcined dolomite are used to adjust the composition of the slag. In this case, in order to prevent the amount of absorbed heat from increasing and to speed up the process of slagging, flux is added as quicklime or calcined dolomite, which is obtained by calcining raw carbonate outside the furnace and decomposing it.
Further, it is customary to add oxygen to the molten slag, for example, at a point, so that the reaction with the molten slag proceeds as quickly as possible.

On the other hand, by applying steelmaking technology, especially gas top-bottom blowing technology,
Methods such as smelting reduction, in which a large amount of oxygen is injected to burn and heat carbonaceous materials to melt and reduce ores, have recently been attracting attention, and various studies have already been conducted.

In the smelting reduction method, the bottom blowing gas is an important element in stirring the melt in an appropriate state and optimizing the reaction rate and heat transfer. However, since a large amount of oxygen is required, if the entire amount is blown from the bottom, the stirring will be too strong, so it is mainly blown from the top.

In such a melt reduction method, it is desirable to increase the secondary combustion rate of the atmosphere, especially in order to increase the calorific value per unit amount of carbon material. However, with the terminal method where oxygen is mainly sprayed from above, the temperature of the atmosphere increases as a result.
This is a harsh condition for refractories.

(Question H that the invention seeks to solve) In a metallurgical furnace that blows oxygen upward, a large amount of oxygen is used,
At present, there is no satisfactory method for suppressing wear and tear on refractories when performing metallurgical operations such as melting and reduction that utilize the heat generated by the oxidation reaction. The present invention provides a method for reducing wear on refractories, particularly those located above the melt surface.

(Means for Solving the Problems) The present invention advantageously solves the above-mentioned problems, and the gist thereof is to use oxygen gas in order to suppress wear and tear on refractories in metallurgical furnaces that can blow gas from the top and bottom. When top blowing, one type of flux such as limestone, quicklime, slaked lime, raw dolomite, calcined dolomite, etc., or dust containing 15% or more of 080 min, or 2fi or more, is directed toward the molten slag surface as in the conventional method. This is a method for suppressing refractory wear in a metallurgical furnace, which is characterized by spraying from the molten material surface toward the upper refractory surface.

(Function) The wear and tear of refractories is controlled by temperature and the degree of reaction with slag components. Under conditions where the molten layer is stirred by bottom-blown gas and a large amount of oxygen is blown from the top, slag scatters into the upper space and falls on the refractories above the molten surface. in a state.

At this time, if the surface temperature of the refractory increases due to the high temperature atmosphere, there is a problem in that the refractory is worn out due to a reaction between the refractory and the slag component.

The method of the present invention, in which the flux of limestone, quicklime, slaked lime, raw dolomite, calcined dolomite, etc. is sprayed not toward the molten slag surface but toward the refractory surface above the molten material surface is more effective as follows. The effect of suppressing wear on refractories based on this mechanism can be obtained.

That is, (1) the melting point is increased by adding components such as CaO or MgO to the molten slag falling on the refractory surface;

As a result, the slag body is kept in a molten state necessary for efficient smelting reactions, and its temperature is kept as low as possible for metallurgical operations of the molten material.

On the other hand, the scattered slag passes through a space with a higher temperature than the slag body, and its temperature is also higher than the slag body, but as the melting point increases, the temperature difference becomes smaller, the viscosity increases, and some parts begin to solidify. As a result, even if it comes into contact with a refractory, it is unlikely to react with it. Therefore, a process that would be impossible if the slag components were the same can be made possible.

■ The temperature near the refractory surface is lowered by the cooling effect of the refractory wall surface by carrier gas such as nitrogen used for flux injection, and by the absorbed heat due to thermal decomposition of carbonates, attached water, hydroxides, etc.

■ Covering the vicinity of the refractory surface with the injected powder blocks radiant heat from the high-temperature atmosphere inside the furnace and suppresses the temperature rise on the refractory surface.

■ One of the embodiments that further enhances the effect of the present invention is to spray powdered coal together on the refractory surface. When used in combination with flux spraying, the negative effects of acidic components such as 5102 contained in coal ash on refractory wear can be suppressed by neutralization.

With these methods, most of the injected flux remains in the furnace and ultimately participates in the composition adjustment of the slag body, but some remains attached to the refractory surface as a coating material, and the remaining bulk The parts scatter as dust. In addition to those caused by this flux, dust is composed of ore, scattered particles such as carbonaceous materials, and those caused by metals, mainly consisting of metallic iron oxide. Dust recovered by exhaust gas treatment is recycled as pseudo particles. By being sprayed against the refractory walls of the metallurgical furnace, the same effect as described above is produced.

At this time, pseudo particles are more likely to be generated due to the flux present in the dust, and as a result, there is also the effect that handling of the dust becomes easier. As shown in FIG. 2, the CaO concentration condition in the dust necessary to obtain this effect is 15% or more. Here, the trouble occurrence frequency index on the vertical axis in Figure 2 is the trouble occurrence frequency when CaO is not included.
．． It was defined as 0 and expressed as a ratio to it.

(Example) FIG. 1 shows an example of a metallurgical furnace for carrying out the present invention.

1 in the figure is for stirring nitrogen into metal bath 2 (100ONm3
/h) It is a bottom blowing tuyere for blowing in as gas.

Oxygen gas (2000ON 3/h) was blown onto the slag 4 through the top blowing lance 3. Nitrogen gas was used as a carrier gas for spraying flux and/or dust, and the solid-gas ratio was set to 17.

The lining refractory material 5 is a magcarbon brick. 6 in the figure is a blowing port for spraying various powders onto the refractory surface.
The powder blowing pipe 7 has a figure 7-shaped tip. The furnace is equipped with three blowholes.

The operating method is hot metal (C; 4.6%, Sl, 0.01%).
) and slag (Ca039%, 510234%, Mg
O.

6%, 802's: 14%) while blowing oxygen to the coal (63% fixed carbon, 13% ash, 25% volatile)
%), iron ore (T, Fe 68.7%, gangue 5.8%)
), iron scrap (chopper scrap, c: 0.2%) was continuously introduced, and the amount of input was adjusted so that the temperature of the metal was 1450°C ± 30°C. In addition, the input ratio of the iron source is ore/scrap -0.9 as iron.

Under the above common conditions, powder (components are shown in Table 2) was injected from the powder inlet 6 under various conditions as shown in Table 1. Then, the refractory wear index (the amount of refractory erosion divided by the amount of blown acid, normalized to 1 based on the conventional method) was determined.

Comparing these results with the conventional method that does not involve powder blowing, the refractory wear index is reduced to approximately 1 month, and the effect of suppressing refractory wear is remarkable.

Table 2 Table 2 Analysis results of raw materials used (effects of the invention) The present invention provides a furnace in which gas is blown from the top and bottom, particularly a large amount of oxygen is blown from the top, and the resulting heat generation effect is utilized for metallurgical operations. Flux containing CaO necessary for metallurgical operations,
Instead of adding dust toward the molten slag surface for the purpose of early slag formation and scattering suppression as in the past, by spraying powder particles toward the refractory wall surface, various effects can be achieved. The combined effect is that it makes it possible to efficiently suppress the wear and tear of the refractories above the molten material surface, which is currently the biggest problem. It has great industrial and economical effects, such as reducing the cost of refractories, making it possible to use an inexpensive flux source, and making it easier to handle the generated dust.

[Brief explanation of drawings]

Figure 's1 shows an example of a metallurgical furnace used to carry out the present invention, and Figure 2 shows how the CaO concentration in dust affects the frequency of handling troubles such as piping clogging during the operation of introducing dust into the furnace. FIG. 1: Bottom blowing tuyere 2: Metal bath 3: Top blowing lance 4 Varnish slug 5: Lining refractory 6: Powder blowing lower: Powder blowing pipe and 4 others Figure: Powder blowing official

Claims (1)

[Claims] 1. Limestone, quicklime, slaked lime, raw dolomite, calcined dolomite, CaO used as flux when top-blowing oxygen gas in a metallurgical furnace that can blow gas from the top and bottom.
1. A method for suppressing wear of refractories in a metallurgical furnace, characterized by spraying one or more types of dust containing 15% or more of dust toward a refractory surface above a molten material surface.