JPH03287709A - Smelting reduction iron making method - Google Patents

Abstract

PURPOSE:To suppress the powdering of carbon material and to effectively utilize fine coal by using briquettes of a specified diameter obtd. by briquetting the fine coal of a specified grain size as the carbon material and charging the briquettes into a molten layer in a furnace from the upper part of the furnace. CONSTITUTION:Briquettes of >=2mm diameter obtd. by briquetting fine coal of <=1mm grain size are used as carbon material in smelting reduction by top blowing of oxygen. The briquettes are charged into a molten layer of raw material for iron in a smelting reduction furnace from the upper part of the furnace. The degree of powdering of the briquettes is lower than that of conventional lump coke and the amt. of the carbon material scattered is reduced, accordingly the efficiency of utilization of the coal can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing iron-carbon alloys such as hot metal without using a blast furnace.

(Prior Art) A blast furnace method is currently used as a method for producing hot metal from iron ore. Although this is an excellent method for mass production, it uses coal with excellent caking properties called coking coal, which has limited resources, and carbonizes it in a chamber coke oven. Requires a large coke. Coke ovens are very expensive equipment, and updating them in the future will require enormous costs. Therefore, in the future, it is necessary to develop a method for manufacturing pig iron without using coke from a chamber coke oven.

In order to solve these problems, research is being carried out on a new method of producing iron called the smelting reduction method. Among these methods, a method in which the gas is blown upward, for example, using a reaction vessel such as a converter and blowing oxygen upward while charging iron ore or its pre-reduced product and carbonaceous material, has a major point in productivity. Therefore, it has been cited as one of the methods that has a high possibility of replacing the current blast furnace method. In this method, when coal is directly used as the carbon material, coal called steam coal, which is produced in large quantities, can be used, and there is an advantage that expensive equipment such as a chamber coke oven is not required.

(Problems to be Solved by the Invention) FIG. 2 shows an example of equipment used to carry out the smelting reduction iron manufacturing method according to the method of the present invention. Oxygen is blown through a top-blowing lance 1 in a container, for example, a converter, in which gas can be blown upward. Gas bottom blowing from the bottom blowing tuyeres 2 is carried out to stir the melt. Nitrogen gas is usually used. Without this bottom blowing, high reduction reaction rate and heat transfer rate of iron oxide cannot be obtained, and the high productivity required by the present invention cannot be obtained. On the other hand, if this stirring becomes too strong, an oxidizing atmosphere, which is a characteristic of the process of the present invention in which iron oxide contained in the slag 4 is reduced while blowing oxygen and burning the carbon material 3, is created. Since the conditions for suppressing the contact of the metal 5 are disturbed, adverse effects such as an increase in the amount of dust generated by iron oxide fume appear due to the contact reaction between the oxygen jet and the metal. Therefore, at least the majority of the oxygen gas will be supplied into the furnace from the upper lance. Therefore, it is necessary to blow in a large amount of gas from the top.

In the figure, 6 indicates air bubbles and 7 indicates a refractory lining.

The iron raw material contains iron oxide such as iron ore or its preliminary reduction product. For the same reason as stated above, even if the iron raw material is in the form of powder, it is preferable to inject it into the molten layer from the top rather than from the bottom. Raw coal or the like is added as a flux.

As the carbonaceous material, a method is usually used in which agglomerated coke or lump coke is directly introduced into the molten layer.

When coke is used as the carbonaceous material, separate coke production equipment is required, which increases the cost of the carbonaceous material. In addition, when agglomerates are used as carbon material, the agglomerates introduced into the molten layer are pulverized due to the rapid generation of volatile matter, and some of the pulverized coal is accompanied by gas. It is discharged from the system through the upper space. As a result, a phenomenon was observed in which the amount of carbonaceous material used increased.

On the other hand, when using pulverized coal, the amount of blown gas scattering out of the system increases, further reducing the utilization efficiency of the carbon material, making it difficult to use.

The above is a summary of the issues related to carbonaceous materials in the conventional smelting reduction ironmaking method, which uses a reaction vessel in which gas is blown over, and top-blows oxygen while charging iron ore or its pre-reduced product and carbonaceous materials. It is as follows.

(1) When powdered coal is used, there is a high rate of coal being discharged out of the system along with the blown gas. Therefore, it is difficult to use powdered coal.

(2) Even in the case of lump carbonaceous material, when lump coal is used, it is pulverized in the reaction vessel, and a part of it is blown up into the upper space along with the blown gas and discharged out of the system. This causes an increase in the unit consumption of carbonaceous materials.

Coal is generally purchased in the form of a powder mixture.

Therefore, for the above reasons, effective utilization of powdered coal becomes a problem.

Therefore, major issues regarding carbonaceous materials in the smelting reduction ironmaking process include preventing pulverization within the molten layer of agglomeration and how to use pulverized coal in the final process.

The present invention is a method for solving these problems.

(Means for Solving the Problems) The gist of the present invention is to melt and reduce iron raw materials containing iron oxide and oxygen by top-blowing oxygen while adding carbonaceous materials using a reaction vessel in which gas is top-blown. A method for manufacturing a carbon-containing alloy by carrying out the following steps, characterized in that an agglomerate of 2 mm or more obtained by molding pulverized coal of 1 mm or less as a carbon material is charged into a molten layer from the upper part of a smelting reduction furnace. It is a smelting reduction iron manufacturing method.

(Function) The smelting reduction iron manufacturing method according to the method of the present invention will be described in detail below along with its function. As the melting reduction equipment used in the method of the present invention, for example, the equipment shown in FIG. 2 described above can be used.

The carbon material used in the method of the present invention is 1 piece of air-dried coal.
Grind into pieces smaller than mm. This powdered coal is then molded using a high-pressure molding machine such as a roll converter. 2)
The agglomerates from which powdery substances have been removed are used as carbon material in the smelting reduction method. After molding, the powdered material less than 2 mm is returned to the molding machine and reused.

The particle size of the powdered coal was set to 1 mm or less because in high-pressure molding machines such as roll converters, coal with a particle size of more than 1 ωm tends to cause microcracks within the particles due to the pressure during molding.
This is because the strength of the agglomerated product decreases as shown in FIG.

In addition, the particle size of the agglomerates is defined as 2 mm or more.
This is because when the powder is introduced into the molten layer, it easily accompanies the blown gas and is discharged out of the system.

Note that a binder such as pitch is not normally required when molding powdered coal, but it may be used if necessary. For example, when producing a thick agglomerate, the strength of the agglomerate is reduced because the transmission of pressure to the agglomerate body is reduced. Therefore, a small amount of binder is used to prevent the strength of the agglomerate from decreasing.

The agglomerate produced in this way was heated to 1350 in a melt reduction furnace.
When poured from above into a molten layer at a temperature of ℃ to 1450℃,
The degree of powdering was significantly lower than that of agglomeration. the result,
The amount of carbon material scattering was significantly reduced.

The reason why agglomerates formed from powdered coal are less likely to be powdered during high-temperature rapid heating than agglomerates is not clear, but it is thought to be as follows. Although agglomerates appear to be homogeneous components, detailed observation using a microscope reveals that various components, such as exdinite, vitrinite, and inertinite, are distributed non-uniformly. These components differ in the amount and timing of volatile components generated during heating. For this reason, when agglomerates are placed in a high temperature state such as a molten layer, the rate of generation of volatile components differs locally, which causes internal strain. On the other hand, in agglomerates, the raw coal is finely granulated, so each component in the agglomerates is relatively homogeneously distributed. For this reason, the generation of volatile matter during high-temperature heating is evened out positionally within the agglomerate. It was thought that this reduced the internal strain of the agglomerate and reduced the possibility of pulverization during high-temperature heating.

In this way, according to the method of the present invention, the high temperature of carbonaceous material? It is possible to improve the overall efficiency of coal usage by reducing pulverization within the melting layer and utilizing pulverized coal.

(Example) A description will be given below based on an example. An agglomerate was produced using steam coal having the components shown in Table 1 under the conditions shown in Table 2.

The agglomerates produced in this way (6t)
kg into a molten layer at 1350℃ in a smelting reduction furnace,
The carbonaceous material was collected after 5 minutes. Then, the particle size distribution of the carbonaceous material was measured and the pulverization status was investigated.

Table 1 Analytical properties of the coal used (wt, U) Table 2 The same treatment was carried out on lump coal of 5 to 10 mm in order to compare the manufacturing conditions of the agglomerates.

Table 3 shows the particle size distribution of the carbon material after rapid heating.

As will be seen, the method of the present invention is 211 times more expensive than the conventional method.
The ratio of +m or less is smaller, and powdering within the high-temperature molten layer is reduced. This indicates that the amount of powdered carbonaceous material scattered outside the system is reduced.

Table 3: Particle size distribution of carbonaceous material after rapid heat treatment It is also clear that the method of the present invention can effectively utilize powdered coal from the beginning.

(Effects of the Invention) By carrying out the present invention, it is possible to improve the utilization efficiency of coal in the smelting reduction method, and it has great industrial significance in that it can be put to practical use economically.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the influence of the particle size of pulverized coal on the strength of agglomerates, and Figure 's2 is a diagram showing an example of equipment for the smelting reduction iron manufacturing process. 1... Top blowing lance 2... Bottom blowing tuyere 3...
・Charcoal material 4...Slag 5...Metal
6... Bubbles 7... Refractory lining 4 people Figure Particle size of coal before forming (u)

Claims (1)

[Claims] 1. A method for producing a carbon-containing alloy by melting and reducing an iron raw material containing iron oxide and adding carbonaceous material while top-blowing oxygen using a reaction vessel in which gas is blown upward.
2 mm obtained by molding powdered coal of 1 mm or less as a carbon material
A smelting reduction iron manufacturing method characterized by introducing the above agglomerates into a molten layer from the upper part of a smelting reduction furnace.