JPS63247308A - Smelting-reduction iron making method - Google Patents

Abstract

PURPOSE:To economically and efficiently execute smelting-reduction of raw material iron ore by sieving the raw material iron ore, pre-reducing the obtd. coarse grain by fluid bed, heating the fine powder at high temp., and then charging respectively from furnace top and tuyere in a vertical type smelting- reduction furnace. CONSTITUTION:The raw material iron ore A composing many kinds of grain sizes is separated into the coarse grain one and the fine powdery ore by a sieve 4. The plus sieve grain C of the coarse grain ore obtd. in there, is pre- reduced by the fluid bed formed by reducing gas G in the fluid bed pre-reduction furnace 1 and then, the reduced iron D obtd. is charged together with coke E for reducing material from the furnace top of the vertical type smelting- reduction furnace 2. On the other hand, the minus sieve powder B of the fine powdery or is made to high temp. condition by combustion heat between fine powdery coal and oxygen or plasma in blasting pipe L and blown into the furnace from the tuyere 3. By this method, all of the above raw material iron ore A is smelting-reduced without executing pretreatment, such as briquetting of the ore, and molten iron is economically obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention efficiently reduces and reduces all of the raw material iron ore containing various particle size components without any special pre-treatment such as preforming. It relates to a smelting reduction iron manufacturing method that can be melted.

[Conventional technology] Raw material iron ore is extracted and extracted as a mixture of powdered ore and granular ore.
It is imported and has a fairly wide particle size distribution from fine to coarse.

In producing molten iron by reducing and melting such raw material iron ore through the smelting reduction ironmaking process, the iron ore is generally reduced to 50 to 70% in a preliminary reduction furnace, and then in an electric furnace.
It is charged into a melting reduction furnace such as a vertical furnace or converter for further reduction and melting. Note that the gas generated from the melting reduction furnace is sent to the preliminary reduction furnace and used as a reducing agent.

Among these smelting reduction ironmaking processes, the method of using a fluidized bed furnace as a preliminary reduction furnace is a method in which granular iron ore is reduced to a fluidized state by reducing gas, and the method involves connecting a blast furnace and a converter. Compared to the indirect steelmaking method using a steel mill and the direct steelmaking method using a shaft furnace, the raw iron ore is subjected to agglomeration treatment (
It is excellent in that it does not require any further steps (such as pelletization, sintering, briquetting, etc.), and can be said to be an effective preliminary reduction method.

[Problems to be Solved by the Invention] However, the fluidization characteristics in a fluidized bed furnace depend on the particle size distribution of the raw material iron ore, and components with too fine particle size, especially those with a viscosity of 100
Fine ore of ~200 μm or less becomes a factor that deteriorates the fluidization characteristics of the solid-gas fluidized bed. The reason for this is that the variation in particle size becomes noticeable, which complicates the control of reducing gas injection to obtain a stable fluid state, and the fine ore particles adhere to each other on their surfaces as the pre-reduction progresses, causing so-called For example, it is easy to cause a sticking phenomenon. Therefore, when using a fluidized bed furnace as a preliminary reduction furnace, it is desirable to sieve and agglomerate fine iron ore with a particle size of 100 to 200 μm or less, which complicates the preliminary treatment process and increases production costs. This is a factor that causes

The present invention has been made in view of these circumstances, and aims to melt and reduce all raw material iron ore containing a mixture of various particle size components from fine to coarse particles without subjecting it to any preliminary treatment such as agglomeration. The purpose of this invention is to provide a method that enables the reduction of fluidized bed pre-reduction methods, thereby increasing the economic efficiency and productivity of the fluidized bed pre-reduction method.

[Means for Solving the Problems] However, the smelting reduction iron manufacturing method of the present invention involves separating raw iron ore into coarse ore and fine ore, pre-reducing the coarse ore in a fluidized bed, and then The gist is that the ore is charged from the top of the smelting reduction furnace, while the fine ore is heated to a high temperature and blown into the tuyere of the vertical smelting reduction furnace to be molten and reduced.

[Function] As mentioned above, fine iron ore deteriorates the fluidization characteristics in the fluidized bed furnace and inhibits the progress of preliminary reduction in the fluidized bed furnace, but fine iron ore itself is not difficult to reduce, but rather due to its specific surface area. It is considered that the reducibility of iron ore is better than that of coarse-grained iron ore. Therefore, the present inventors thought of reducing and melting fine iron ore obtained by sieving raw material iron ore by directly introducing it into a smelting reduction furnace without introducing it into a fluidized bed furnace, and in line with this policy. As a result of repeated research, we have completed the present invention shown in the above configuration.

That is, in the present invention, a fluidized bed furnace is used as the preliminary reduction furnace, and a vertical furnace is used as the smelting reduction furnace. In other words, the fluidized bed furnace has the advantage of being able to pre-reduce raw iron ore without agglomerating it, as mentioned above, and coarse iron ore (raw iron ore other than fine iron ore) can be treated in the fluidized bed as before. It is pre-reduced in a furnace and then introduced into a vertical melting reduction furnace where it is reduced and melted. By adopting the configuration in which coarse iron ore is separately introduced into the fluidized bed furnace, the fluidization characteristics in the fluidized bed furnace are stabilized, and fluctuations in the metallization rate of reduced iron can be suppressed. Furthermore, since there is no fine iron ore, no sticking phenomenon occurs during the fluidized bed reduction process even if high temperature gas (approximately 900° C., usually 800° C.) is used, and productivity in the fluidized bed furnace can be improved. Incidentally, fine iron ore and other coarse iron ore may be separated using a sieve or the like, and the coarse iron ore on the sieve may be charged into an eight-layer flow furnace. There is no particular restriction on the size of the sieve, as long as it separates fine iron ore that deteriorates the fluidization characteristics in the fluidized bed furnace, but as a guide, a suitable size between 100 and 200 μm is recommended. It is recommended to use a sieve.

On the other hand, fine iron ore separated by a sieve is fed into a rigid smelting reduction furnace without passing through a fluidized bed furnace.
If reduced iron obtained from a fluidized bed furnace and reducing agents such as coke are introduced from the top of a vertical smelting reduction furnace, the ventilation inside the furnace will deteriorate, resulting in a worsening of the reduced state of not only the fine iron ore but also the reduced iron. , the overall productivity and quality of the melting reduction operation will deteriorate significantly. Therefore, in the present invention, pulverized iron ore is blown into a vertical smelting reduction furnace through a tuyere that blows combustion air, and, for example, the pulverized iron ore is introduced into a blow pipe leading to the tuyere. However, the direct reduction of fine iron ore injected into the furnace from the tuyere is as follows (1), (
2) The reaction proceeds as shown in the formula.

Fe203(S) + C(S)-2FeO(L) +
Co(G) ・”・・’ (1) Fed(IjuC(
S) −Fe(I +CD (G) −・・−(
2) Since the above reaction is a very large endothermic reaction, simply injecting fine iron ore through the tuyere will cause a decrease in the temperature inside the furnace, and will also have an adverse effect on the reduction and melting of the reduced iron. Therefore, in the present invention, for example, pulverized coal and zero
2 is blown into the furnace and the heat of combustion is used to guarantee the heat, or the temperature of the blast is increased by plasma heating to make the fine iron ore hot and then blown into the furnace. As a result, the fine iron ore is directly reduced according to the reactions of equations (1) and (2) above, and the reduction and melting reaction of the reduced iron in the vertical smelting reduction furnace also progresses well, making it possible to efficiently and economically produce molten iron. can do.

Furthermore, the residence time of fine iron ore injected through the tuyere in the raceway space is extremely short, approximately 0.01 seconds, so even if the heat transfer efficiency to fine iron ore is increased, it will not be possible to supply heat locally and intensively. has a limit. Therefore, the amount of fine iron ore that can be injected through the tuyere is limited by the raceway space volume, that is, the equipment size of the vertical smelting reduction furnace. However, a generally adopted rigid smelting reduction furnace with a molten iron production capacity of about 100 tons/Hr has a reduced iron processing capacity of 104 to 115 tons/Hr.
Therefore, the amount of fine iron ore that can be blown from the tuyere at this time is about 14 to 27 tons/Hr. The iron content of coarse iron ore that can be introduced into the fluidized bed furnace is 60-65%.
Then, the amount of coarse iron ore that can be processed in the fluidized bed furnace-rigid smelting reduction furnace system is 133 to 145 tons/Hr.
Therefore, the ratio of the processable amounts of fine iron ore and coarse iron ore is in the range of approximately 1:5 to 1=10. However, the content of fine iron ore of 100 to 200 μm or less in the raw material iron ore currently supplied is about 10 to 20%, and this particle size structure matches well with the above-mentioned throughput ratio. Therefore, by employing the method of the present invention, currently supplied raw material iron ore can be melted and reduced without leaving either fine iron ore or coarse iron ore.

[Example] FIG. 1 is a schematic diagram showing an embodiment of the present invention, in which a smelting reduction system was constructed by combining a fluidized bed furnace 1 and a rigid smelting reduction furnace 2. Raw material iron ore A is first passed through a sieve 4 to obtain a particle size of 1
Sieved Kudamatsu (fine iron ore) B with a particle size of less than 00 μm and a particle size of 100
It was separated into sieved soil powder (coarse iron ore) C with a size of μm or more. Next, the sieved soil powder C is introduced into a fluidized bed furnace 1, and then a rigid smelting reduction furnace 2.
Fluidized bed reduction was carried out by contacting with high-temperature reducing gas G supplied from. The reduced iron oxide with a metallization rate of about 70% obtained in the fluidized bed furnace 1 is charged into the furnace from the top of the rigid melting reduction furnace 2 together with coke E, and is reduced by the Co gas rising in the furnace, and eventually becomes It was melted and stored at the bottom of the furnace. On the other hand, the sieved Kudamatsu B is introduced into the blast pipe leading to the tuyere 3 of the vertical smelting reduction furnace 2, and is transported by air heated to a high temperature by the combustion heat of the pulverized coal and oxygen introduced upstream from the introduction position. and flowed into the furnace. Then, it was melted and reduced based on the direct reduction reaction shown in formulas (1) and (2) above, and stored at the bottom of the furnace. In this way, hot metal and slag were obtained from the vertical smelting reduction furnace, and by separating them from the slag, the desired hot metal could be obtained.

[Effects of the Invention] The present invention is configured as described above, and all raw iron ore containing various particle size components can be melted and reduced without pretreatment such as preforming. We were able to provide an economical direct steel manufacturing method that takes advantage of the features of reduction.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention. 1... Fluidized bed preliminary reduction furnace

Claims (1)

[Claims] The raw iron ore is separated into coarse ore and fine ore, and the coarse ore is pre-reduced in a fluidized bed before being charged into the top of a vertical smelting reduction furnace, while the fine ore is heated to a high temperature and melted in the vertical smelter. A smelting reduction iron manufacturing method characterized by blowing through the tuyere of a reduction furnace and melting and reducing.