JPS5942042B2 - Blast furnace operating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for operating a blast furnace, and in particular, the present invention relates to a method for operating a blast furnace. This is a proposal for a method to control chemical reactions at the inner tuyere level.

The charging of raw materials such as ore to the top of the blast furnace requires extremely careful control since it does not directly affect the furnace condition.

The mainstream of conventional control is the ore in the radial direction of the furnace,
It targets the coke layer thickness distribution and particle size distribution. For example, the ore layer thickness distribution as shown in Figure 1-a affects the gas flow distribution and the shape of the cohesive zone, and the fuel ratio of the blast furnace, This is an important factor governing stable operations.

Moreover, the ore particle size distribution as shown in FIG. 1-b affects air permeability and reducibility.

For this reason, in conventional blast furnaces, the ore layer thickness distribution,
Blast furnace operations are carried out by controlling particle size distribution, but these conventional methods do not control the chemical reaction itself from the raceway to the furnace core in the siding area, which has a large temperature distribution, so it is difficult to control the final hot metal composition. cannot be directly adjusted.

For example, in which part (temperature range) in the radial direction of the tuyere should the reduction reaction of SiO2 be activated?
) In this respect, conventional methods cannot actively adjust the distribution of the amount of SiO2 in the radial direction of the furnace, and iron ore is normally charged uniformly, so this is necessary. In other words, in order to adjust the (Si) concentration, methods have been used to adjust the furnace heat level and the basicity of the slag.

However, in the case of a blast furnace, it is known that there is a positive correlation between the [Si] concentration and the furnace heat level, and it is difficult to operate in a situation where the furnace heat level is high and the (Si) concentration is low.

The purpose of the present invention is to overcome the drawbacks of the conventional blast furnace operating method described above, and the ore charged in the blast furnace is separated in advance into multiple types of ore with different basicities, and each of the ores thus separated is By charging the slag at different positions in the radial direction of the furnace depending on the temperature distribution at the mouth level, for example, the basicity of the slag dripping from the raceway at the tuyere level to the furnace core can be distributed. This is a method of controlling the chemical reaction at the tuyere level, which is mainly composed of Sin2), and adjusting the hot metal composition to the target.

The details of the configuration of the present invention will be explained below.

The present invention charges a plurality of types of charge ores with different basicities at different positions in the furnace radial direction according to the temperature distribution in the furnace at the tuyere level, and This is a method for controlling the basicity distribution, and the following method is preferably adopted as a specific method for giving basicity distribution to ore charging.

■ First, the ore to be charged is sorted into three types of basicity (B2a, B11.B2°) and sent separately to the top of the furnace using a charging conveyor.

■ Next, adjust the armature angle of the movable armor for a bell blast furnace, or the tilting angle of the rotating chute for a bellless blast furnace, to move each base-transformed ore that has been pre-separated as described above into a predetermined position in the radial direction. Separate them and drop them at different locations.

FIG. 2 is an example of the charge distribution deposited by adopting such a charging method.

Whether the actual charge is as shown in the diagram is checked from time to time using a charge profile meter.

FIG. 3 shows an example of the basicity distribution of the furnace charge layer obtained by the above-mentioned irregular base charging, in which the basicity of the furnace wall is higher than that of the center.

This mutual movement in the radial direction accompanying the descent of the charge layer is small and does not reduce the effect of separate charging, and the same basicity distribution is maintained at the tuyere level.

Now, when the temperature distribution 2 at the tuyere level is higher at the furnace wall, as shown in Figure 4, in peripheral flow operation, ■ ore charging to obtain the basicity distribution as shown in Figure 2. If you do (
The method of the present invention) will be compared with (1) the case of charging ore as shown in FIG. 1 with no basicity distribution (conventional method).

Note that the temperature distribution at the tuyere level will be determined by actual measurements or model calculations, if necessary.

The reaction in which (Sin2) in the slag is reduced is (Si0
2) +2C→(S i ) + 2CO, and the more the reduction progresses, the more (Si,l) in the hot metal increases.

By the way, the above reaction tends to proceed under the conditions that the (SiO□) concentration in the slag is high, that is, the basicity (Ca O / S io 2 ) is low, and/or the temperature is high.

In the case of example (2) of the present invention, the temperature is high near the furnace wall at the tuyere level, but the reduction reaction of 5i02 is suppressed due to the high basicity in this area, and the temperature is low in the center, although the basicity is low. Because of the low concentration (SiO2), the reduction reaction does not proceed much.

On the other hand, in the case of the conventional method (■), slag with the average basicity of the charged ore (relatively lower than that of the present invention) enters the high temperature section, so the reduction reaction of (8102) is significantly lower than that of the present invention. proceed.

Therefore, in the example of the present invention, (Si,
l can be lowered.

As shown in the examples above, if a basicity distribution is given in the radial direction of the furnace, the hot metal components can be adjusted by controlling the furnace heat level and the average basicity near the raceway 3 in front of the tuyere 1 to a constant value. Can be done.

In addition, although FIG. 3 describes the case where the basicity is high on the furnace wall side and the basicity is low in the center, the distribution is not necessarily limited to the above distribution.

For example, if the basicity distribution is reversed to that shown in Figure 3 above, that is, if ore is charged so that the basicity is lower at the furnace wall than at the center, (Si) increases and Si pig iron can be produced without increasing the hot metal temperature.

In the above example, the basicity of the ore is B2a, B2b, B! 2
We have explained the case of dividing into three types of basicity, but it is effective if the basicity is divided into two or more types, but dividing it into too many types has disadvantages such as making the cutting operation from the storage tank complicated. Therefore, in practice, it is preferable to divide the types into five types at most.

In addition, the difference in basicity between each group separated as above is determined by the number of basicity divisions, the target (Si
), the difference in basicity is 0.0, although it varies depending on operating conditions etc.
A range of 1 to 2.0 is suitable.

If the difference is less than 0.01, no effect can be expected even when four types of basicity are used, and if the difference is more than 2.0, it is not advisable due to raw material circumstances.

That is, even when the highest B2 sintered ore and the lowest B2 raw ore are combined, it is difficult to achieve a grade of 2.0 or more.

Next, the present embodiment will be explained.

Conventionally, one charge of 80 tons of ore with an average basicity of 1.25 was divided into two, 40 tons of ore with a basicity of 1.6 and 40 tons of ore with a basicity of 0.9. Charge.

First, using movable armor (MA), basicity 1.6
When charging the material, use the MA notch 4a in Fig. 2.
Charge to the furnace wall side.

Next, when charging the material with a basicity of 0.9, use 4b (extrusion distance Im) and charge it to the center side of the furnace.

As a result, ores with high basicity gather on the furnace wall and ores with low basicity gather in the furnace center. can be converted into

If charging was done by the conventional method without using the present invention, the basicity distribution was uniform and the (Si) content in the hot metal was 0.35%. was constant, but (Si) decreased to 0.2s%.

Table 1 on the next page shows a comparison between the method of the present invention and the conventional method. In the case of the method of the present invention, the purpose has been sufficiently achieved for low (Si) pig operation, for example, (Si)% It is possible to control this separately from the control of the furnace heat level.

[Brief explanation of drawings]

Figure 1 of the drawings is a route map of the furnace top profile when the layer thickness distribution a and particle size distribution A are adjusted during ore charging, and Figure 2 is the furnace top profile when ore is charged separately for base transformation. Figure 3 is a basicity distribution map of the charge layer in the furnace, and Figure 4 is a route map showing the temperature distribution in the furnace.

Claims (1)

[Claims] 1. According to the temperature distribution in the furnace at the tuyere level, multiple types of charge ores with different basicities are charged at different positions in the radial direction of the furnace, and the basicity distribution of the charge in the radial direction of the furnace is controlled. A blast furnace operating method characterized by: