JPH03215619A - Method for blowing flux into blast furnace - Google Patents

Abstract

PURPOSE:To prevent the clogging of piping for blowing with flux by mixing pulverized coal to the flux at the specific ratio at the time of blowing MgO, CaO series flux from a tuyere for producing low Si molten iron in a blast furnace. CONSTITUTION:In order to lower the Si content in the molten iron tapped during operating the blast furnace, the MgO, CaO based flux is blown from the tuyere and reacted with SiO2 in molten slag in the vicinity of the blowing tuyere, and by making the stable slag, activity of SiO2 is reduced to prevent the increase of Si in the molten iron with the reduction of SiO2. In this case, in order to prevent the clogging of the flux blowing pipe with the MgO, CaO based flux having high m.p., the pulverized coal is mixed with the flux at 0.07-0.4 ratio. The low Si molten iron can stably be produced with the molten material of flux without clogging of the piping.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of Nisaku] The second invention relates to a method for blowing flax into a blast furnace by mixing pulverized coal and flax and blowing the mixture through the blast furnace lining.

ΣConventional Technology Pulverized coal is injected through the blast furnace tuyeres for the purpose of lowering the coke ratio. Also, made? ~ In pursuit of total cost minimization during steelmaking and the needs of high-grade steel manufacturing, in addition to hot metal pretreatment technology, tuyere powder is introduced as a low-Si operation technology for blast furnaces by injecting powder through the lining to lower Si in the pig iron. Blow-in technology is being tried by various steel companies.

One method is to inject 5 kg or more of fine powdered iron oxide per tonne of hot metal, or to inject the iron oxide together with fuel.
Japanese Unexamined Patent Application Publication No. 1983-1988- oxidizes Si and turns it into SiO2 slag
96803). Alternatively, there is a method in which a MgO source or a CaO source is injected through the tuyere by franking. This is because SiO gas is generated in the blast furnace mainly near the tuyere raceway where the ambient temperature is high, and it is thought that St enters the hot metal through the reaction of SiO ÷ C-SiO + CO.
gO. By injecting CaO-based furanox into the tuyere, the activity of Si02 in the slag near the tuyere is reduced, and S i O 2 ”.C→ S i O+
It is thought that this suppresses the reaction of CO and lowers the Si content in the pig iron.

[Problems to be Solved by the Invention] When flux is injected in a concentrated manner, there is a problem in that pipes, vents, and nozzles are subject to increased wear and clogging, but this problem can be solved by mixing flux and pulverized coal. It is known that however,
The appropriate mixing ratio of Franks and pulverized coal has not been clarified, and depending on the mixing ratio, pipe clogging may occur. An object of the present invention is to provide an appropriate mixing ratio that does not cause pipe clogging.

[Means for Solving the Problems] The present invention aims to achieve the above objects,
MgO from the blast furnace tuyeres into the furnace. In the method of injecting flux into a blast furnace in which Cao-based flux and pulverized coal are mixed and injected, the mixing ratio of flux and pulverized coal is set to 0.07 to 0.
This is a method for injecting flux into a blast furnace, characterized in that the flux is in the range of 4.

[Function] The reason why the mixing ratio of flux and pulverized coal is set in the range of 0.07 to 0.4 is that if the mixing ratio of flux and pulverized coal is less than 0.07, the concentration of flux in pulverized coal will fluctuate greatly. However, the effect of reducing Si in pig iron is extremely small, and if the mixing ratio of flux and pulverized coal exceeds 0.4, the fluidity in the pipes deteriorates, causing pipe clogging, making it difficult to blow in. This is because. [Example] Examples of the present invention will be described in detail below. The inventors, etc.
To investigate the fluidity of a mixture of flux and pulverized coal,
A test was conducted to investigate changes in the degree of compaction and collapse angle of the mixture by changing the mixing ratio (mixing weight ratio) of flux and pulverized coal. Here, it is well known that the smaller the degree of compression and the angle of collapse, the better the fluidity and the less clogging occurs in the pipes. Figure 3 shows the change in the degree of compaction of the mixture. When pulverized coal is mixed (mixing ratio: 0), the degree of compaction is 34%, and as the mixing ratio increases, the degree of compaction also increases, and the degree of compaction increases as the mixing ratio increases. When the ratio was 1, the degree of compression was 41%. Figure 4 shows the change in the collapse angle of the mixture.When the mixture tastes like pulverized coal, the collapse angle is 19 degrees, and as the mixture ratio increases, the collapse angle also increases, and when the mixture ratio is 1, the collapse angle is 19 degrees. 2 corners
It became 4 degrees. In other words, it was found that as the mixing ratio increased, the fluidity deteriorated.

Furthermore, a test was conducted by temporarily installing piping to be used when injecting flux, and it was found that if the mixing ratio exceeded 0.4, clogging occurred in the piping, making it impossible to inject the flux. The compression change at this time is 37? ≦, the collapse angle is 21
It was degree.

Next, using a small test blast furnace, the amount of decrease in S1 in the pig iron was investigated by changing the mixing ratio of flux and pulverized coal. 1st
The figure shows the results. There is almost no decrease in Si in the pig iron until the mixing ratio is 0.07, and when the mixing ratio exceeds 0.07, the amount of decrease in Si in the pig gradually slows down. When the mixing ratio was 0.4, it became 0.15%, and when the mixing ratio exceeded 0.4, pipe clogging occurred as in the previous test result, making the blowing test impossible. Ta. During this test, the mixture was sampled upstream of the injection lance, and the variation in flux concentration in the pulverized coal (maximum value to minimum value) for each mixing ratio was investigated. Figure 2 shows the results; when the mixing ratio is less than 0.07, the variation is large;
It was found that when the mixing ratio exceeded 0.07, the variation decreased rapidly. This means that if the mixing ratio is small, it becomes difficult to mix the flux uniformly into the pulverized coal, and the mixing ratio of the flux to the pulverized coal is 0.
．． 07 or more [Effects of the Invention] The method of the present invention has the effect that, in the method of mixing flux with pulverized coal and blowing it in, there is no piping clogging and S1 in the pig iron can be reliably lowered. .

[Brief explanation of drawings]

Figure 1 shows the mixing ratio (furanox/pulverized coal) and Si% in pig iron.
Figure 2 is a graph showing the relationship between the mixing ratio (flux/
Figure 3 is a graph showing the relationship between the mixing ratio (flux/pulverized coal) and degree of compaction; Figure 4 is the graph showing the relationship between the mixing ratio (flux/pulverized coal) and the collapse angle. It is a graph diagram showing the relationship between.

Claims (1)

[Claims] In a method of injecting flux into a blast furnace in which a mixture of MgO, CaO-based flux and pulverized coal is injected into the furnace from the blast furnace tuyere, the mixing ratio of flux and pulverized coal is 0.07-0.
4. A method for injecting flux into a blast furnace.