JPH0959703A - Operation of blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain both of the protection of a furnace bottom refractory and the stable operation of a blast furnace by deciding TiO2 charging quantity based on Si concn. in molten iron while controlling the Ti concn. in the molten iron. SOLUTION: At the time of rising the Ti concn. in the molten iron by charging the TiO2 source into the blast furnace, it is necessary to adjust this charging quantity so as to obtain the viscosity of molten iron, i.e., the Ti concn. in this critical concn. range. For example, in the case of adding 15kg/tp of TiO2 source, the Ti concn. is increased accompanying the increase of the Si concn. under relation of the Si concn. and the Ti concn. Then, the TiO2 charging quantity is decided based on the Si concn. in the molten iron while controlling the Ti concn. in the molten iron so as to obtain within the critical concn. range decided from the predetermined relation of the viscosity of the molten iron and the Ti concn. in the molten iron. By this method, at the time of charging the TiO2 source into the blast furnace, the unstable furnace condition of iron tapping trouble, etc., caused by excessive rising of the viscosity of the molten iron can be avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for operating a blast furnace, in which a TiO ₂ source is introduced into the blast furnace in order to prevent the blast furnace bottom refractory from being damaged.
In particular, the present invention relates to a blast furnace operating method capable of avoiding instability of the furnace condition such as tapping trouble due to excessive increase in hot metal viscosity when a TiO ₂ source is charged into the blast furnace.

[0002]

2. Description of the Related Art In recent years, extending the life of a blast furnace has become an important issue from the viewpoint of reducing the cost of ironmaking. One of the factors that influence the life of a blast furnace is the wear of the refractory at the bottom of the furnace.
In the case of the bottom of the furnace, since the environment is such that hot metal is always present, unlike the shaft part, there is no technique for repairing when the wind blows during blast furnace operation, and there are many problems to be solved.

As a technique for protecting the refractory at the bottom of the furnace, there has been a conventional method for strengthening the cooling of the bottom of the furnace and at the same time, for the source of TiO ₂ (hereinafter simply referred to as Ti
Introduction of O ₂ may be called) have been made. The TiO ₂ charged into the blast furnace is reduced in the blast furnace and transferred to the hot metal,
Part of it becomes a solid solution of TiN and TiC, that is, titanium copper bear of red copper color. Since this solid solution has a high melting point of 2000 ° C. or higher, it adheres to the wear part of the refractory material on the side wall of the furnace bottom to protect the furnace bottom. Phenomenon is that by admixing TiO ₂ into the hot metal, the viscosity of the hot metal is increased to a certain value or more to promote the adhesion of such titanium bare.

Therefore, in the conventional case, when the bottom of the furnace is worn, the temperature of the area rises. Therefore, the temperature of the bottom of the furnace is constantly monitored by a thermometer provided on the bottom of the furnace, and the temperature rise is observed. When this happens, the bottom of the furnace has been protected by introducing a TiO ₂ source.

By the way, even in the past, a blast furnace operating method for the purpose of protecting the bottom of the blast furnace has been proposed, for example, Japanese Patent Publication No. 6-4887 and JP-A-4-297511.
Japanese Patent Laid-Open Publication No. 9-242242 discloses a method of blowing coke or metal (metal oxide) together with TiO ₂ .

However, in any case, as a basic operation, when the temperature of the bottom of the furnace rises and the wear of the bottom refractory is feared, it is possible to deal with it by simply increasing the input amount of TiO _2. There is. For example, when refractory wear is severe and importance is attached to the protection of the hearth, the TiO ₂ input amount may be significantly increased to 20 kg / pt.

However, as a result, a large amount of Ti may be distributed in the hot metal and the Ti concentration in the hot metal may rise excessively. When the Ti concentration in the hot metal increases, the increase in the hot metal viscosity cannot be avoided, and when the Ti concentration in the hot metal, that is, the hot metal viscosity increases excessively, the hot metal does not flow smoothly, leading to tapping trouble, Blast furnace operation problems will be caused.

On the contrary, when the amount of TiO ₂ input is too small,
In some cases, the Ti concentration in the hot metal does not rise so much, the viscosity of the hot metal does not rise as much as desired, and there is no effect on the protection of the furnace bottom.In this case, it is necessary to further increase the amount of TiO ₂ input to protect the furnace bottom. Come out. Moreover, during that time, the bottom protection will not be performed, which may lead to a serious accident in some cases. Therefore, at present, even if it sometimes causes a decrease in the operating rate, a large amount of TiO ₂ is added to protect the bottom of the furnace.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to increase a predetermined amount of TiO _{2 to} protect a furnace bottom refractory and to increase a predetermined hot metal viscosity, and to prevent a tapping trouble due to an excessive increase in hot metal viscosity. It is to develop the technology to avoid the deterioration of the furnace condition and the deterioration of the blast furnace operating rate. A specific object of the present invention is to develop a technique for controlling the amount of the TiO ₂ source when the TiO ₂ source is charged to the blast furnace for the purpose of protecting the furnace bottom refractory and realizing a stable operation of the blast furnace.

[0010]

Here, the present inventors
Various studies were conducted in order to achieve the above-mentioned object, and attention was paid to the fact that the behavior of Ti in the hot metal is similar to that of Si.When introducing a TiO ₂ source into the blast furnace to protect the furnace bottom, the Si level in the hot metal ( It was found that the Ti concentration in the hot metal after charging the TiO ₂ source can be understood to some extent by the furnace heat level).

That is, the Ti concentration in the hot metal which is increased by introducing the TiO ₂ source can be determined by the hot metal Si level at that time, that is, the furnace heat level. Therefore, the amount of TiO ₂ input for realizing a predetermined hot metal viscosity increase can be determined. The present invention has been completed, knowing that it can be determined according to the hot metal Si level.

Here, in the present invention, in a blast furnace operating method in which a predetermined amount of TiO ₂ is additionally charged when the bottom temperature of the blast furnace exceeds a predetermined critical temperature, the hot metal viscosity and the hot metal Ti which are obtained in advance are It is a blast furnace operating method characterized by determining the amount of TiO ₂ input based on the hot metal Si concentration while controlling the hot metal Ti concentration so that it falls within a critical concentration region determined from the relationship with the concentration.

[0013]

The operation of the present invention will be described more specifically with reference to the accompanying drawings. FIG. 1 is a graph showing a general relationship between hot metal viscosity and Ti concentration in hot metal.

In the figure, the hot metal viscosity is required to some extent to protect the furnace bottom refractory, and the hot metal viscosity at that time is called the minimum required viscosity. On the other hand, if the hot metal viscosity rises excessively, tapping trouble will occur, and the limiting viscosity at that time is called the maximum limiting viscosity. Specifically, those values vary depending on the hot metal temperature, but generally, the minimum required viscosity is about 5 cp and the maximum limiting viscosity is about 10 cp. The Ti concentration in the hot metal when the respective viscosities are obtained is called the minimum required Ti concentration and the maximum limit Ti concentration, and the concentration region between them is called the critical concentration region. In the illustrated example, the lower limit and the upper limit are Ti: 0.1 to 0.15% and Ti: 0.20 to 0.
The region of 25% is the critical concentration region.

That is, the TiO ₂ source was charged into the blast furnace to produce hot metal.
When increasing the Ti concentration, it is necessary to adjust the input amount so that the hot metal viscosity, that is, the Ti concentration falls within this critical concentration region.

FIG. 2 is a graph showing the relationship between the Si concentration in the hot metal and the Ti concentration in the hot metal when a fixed amount of the TiO ₂ source is added. In the figure, for example, 15 Kg / pt of the TiO ₂ source was added. Then,
The relationship between the Si concentration and the Ti concentration at that time is shown in the graph at the left end. It can be seen that the Ti concentration also increases as the Si concentration in the hot metal increases.

That is, SiO ₂ in the charge of the blast furnace is distributed as Si in the hot metal and as SiO _{2 in the} slag. This distribution ratio is governed by the furnace heat of the blast furnace, etc. When the furnace heat rises, the amount of Si in the hot metal rises, while the amount of SiO ₂ in the slag decreases. TiO ₂ also behaves similarly to the above-mentioned SiO _2, and when the Si content in the hot metal is high, the Ti concentration in the hot metal also rises.

In the figure, the critical concentration region is also described as a region between the lower limit control values, and as described above, the Ti concentration in the hot metal is regulated within this region. In other words, if within the critical concentration range determined from the relationship between the hot metal viscosity and the hot metal Ti concentration in FIG. 1, these upper and lower control values may be appropriately determined.

Therefore, for example, if the Si concentration in the hot metal at the time when the furnace bottom temperature rises is 0.30%, at that time, the Ti concentration in the hot metal must be within the above-mentioned critical concentration region.
The amount of O ₂ source input must be 15 kg / pt. Of course, if the input amount is further subdivided, it can be seen that an input amount of about 13 kg is acceptable.

Then, if 15 kilograms are continuously input, Si
Depending on how the amount changes, for example, the amount of Si increases to 0.45
%, The Ti concentration in the hot metal deviates from the above critical concentration range, so the input amount of the TiO ₂ source is, for example, 10 Kg / pt.
It is changed to. When the Si content decreases, the reverse operation is performed. In the same manner, the amount of input TiO ₂ is controlled while constantly monitoring the Si concentration in the hot metal. The present invention controls the input amount of the TiO ₂ source on the basis of the above principle. The specific operation is performed as follows.

First, by constantly monitoring the bottom temperature of the blast furnace, it is detected that the temperature exceeds a predetermined critical temperature. Normally, the blast furnace feedstock always contains a certain amount of TiO ₂ , and the blast furnace operation is continued in such a state. Especially, the ore having a high TiO ₂ content is not charged into the blast furnace.

However, when the furnace bottom temperature rises and exceeds the above-mentioned critical temperature, first, according to the present invention, ore having a high TiO ₂ content is added to the blast furnace raw material and charged into the blast furnace, or the tuyere The TiO ₂ source ore is blown into the blast furnace. In addition, in the present specification, including both charging modes, it is referred to as “charging into the blast furnace”. At that time, first, the target critical concentration region of Ti in the hot metal is determined in order to avoid instability of the furnace condition such as tapping trouble due to viscosity increase. This may be an amount between the maximum critical viscosity and the minimum required viscosity, and the critical concentration region corresponding to it may be determined by appropriately setting the amount between them. On the other hand, the amount of Si in the hot metal is detected, and the amount of TiO ₂ source to be added so that the Ti concentration is within the critical concentration region is determined based on the relationship between the Si concentration in the hot metal and the Ti concentration that was previously obtained. To do. Then, the TiO ₂ input amount is adjusted according to the hot metal Si level (furnace heat level) so that it is always within the above-mentioned critical concentration region.

Then, when the temperature of the bottom of the furnace finally decreases, the supply of the TiO ₂ source is stopped and the normal operation is resumed. Therefore, according to the present invention, Ti
When the TiO ₂ input amount is controlled according to the Si level in the hot metal when the O ₂ source is input, that is, the furnace heat level, the furnace condition occurs because the hot metal viscosity increases excessively when the TiO ₂ amount is increased. You can avoid trouble.

Further, according to the present invention, when the furnace bottom temperature rises when the hot metal Si level is high and the furnace bottom temperature rises,
In the conventional method, the amount of TiO ₂ input is often raised too much,
Operational problems that occur at such times can be effectively prevented.

Thus, in order to maintain stable operation, Si in the hot metal is
By controlling the amount of TiO ₂ input according to the concentration, such operational troubles can be avoided. Next, the function and effect of the present invention as described above will be described more specifically by way of examples.

[0026]

EXAMPLE In this example, the critical temperature of the bottom of the furnace was set to 200 ° C., and when the temperature of the bottom of the furnace exceeded 200 ° C., the input amount of the TiO ₂ source to the blast furnace raw material was controlled according to the present invention. At this time, the relationship of FIG. 2 was previously obtained from the relationship of FIG.

Example 1 Since the furnace bottom temperature exceeded the critical temperature of 200 ° C., it was decided to start feeding a TiO ₂ source to protect the furnace bottom refractory. ↓ At this time, since the hot metal Si level was low at 0.30% or less, the amount of TiO ₂ input was increased a little from the relationship shown in FIG.
With (charged TiO ₂ amount of 8 to 10 kg / up), the Ti concentration in the hot metal did not increase so much, and it was judged that the effect of protecting the furnace bottom was weak, so the amount of TiO ₂ added was increased. Due to the reason ↓, the input amount of TiO ₂ was greatly increased to 20 kg / pt.

From the above effects, the following results were obtained. (i) A solidified layer was formed at the bottom of the furnace and the temperature of the furnace bottom dropped
(The furnace bottom refractories were protected). (ii) There was no excessive increase in the Ti concentration in the hot metal and no operational troubles.

Example 2 Since the furnace bottom temperature exceeded the critical temperature of 200 ° C., it was decided to increase the amount of TiO ₂ input to the blast furnace compounded raw material in order to protect the furnace bottom refractory. ↓ Since the hot metal Si level is high at the 0.60% level, it is judged from the relationship shown in Fig. 2 that if the amount of TiO ₂ input is increased, the hot metal Ti will rise excessively, which may cause operational troubles (operation. Trouble above: Due to excessive increase in hot metal viscosity,
(It becomes difficult to discharge the hot metal in the furnace, and the residual hot metal in the furnace becomes involved, which inevitably reduces the operating rate.) Due to the reason ↓, the input amount of TiO ₂ was set as low as 10 kg / pt and increased.

From the above effects, the following results were obtained. (i) There was no operational trouble without excessive rise of hot metal Ti (focusing on the protection of the bottom of the furnace, the amount of TiO ₂ input was 20 kg / pt
If so, the hot metal viscosity may have increased excessively, which may have caused operating problems.)

[0031] (ii) furnace bottom solidified layer is formed, since the furnace bottom temperature is lowered (Si levels were high, the TiO ₂ input amount 10
Increasing the amount to kg / pt increased the amount of hot metal Ti sufficiently and was effective in protecting the hearth bottom.)

[0032]

As shown in the above example, the purpose of protecting the hearth bottom is as follows.
Upon up of TiO ₂ input amount, by controlling in accordance with TiO ₂ input amount to the hot metal Si level, it was possible to realize (1) hearth refractories protective, (2) both of blast furnace stable operation.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between hot metal viscosity and Ti concentration in hot metal.

FIG. 2 is a graph showing the relationship between the Si concentration in hot metal and the Ti concentration in hot metal when a predetermined amount of TiO ₂ source is added.

Claims (1)

[Claims] 1. In a blast furnace operating method in which a predetermined amount of TiO ₂ is additionally charged when the blast furnace bottom temperature exceeds a predetermined critical temperature, the previously determined relationship between hot metal viscosity and hot metal Ti concentration is used. Hot metal so that it falls within the determined critical concentration range
A method for operating a blast furnace, characterized in that while controlling the Ti concentration, the TiO ₂ input amount is determined based on the hot metal Si concentration.