JPH03287708A - Smelting reduction iron making method - Google Patents

Abstract

PURPOSE:To prevent the powdering of briquettes and to increase the efficiency of utilization of coal and fine raw material for iron by mixing fine coal of a specified grain size with fine iron-contg. raw material of a specified grain size, briquetting this mixture and charging the resulting briquettes of a specified diameter as carbon material into a molten layer in a furnace from the upper part of the furnace. CONSTITUTION:Briquettes of >=2mm diameter obtd. by briquetting a mixture of fine coal of <=1mm grain size with fine iron-contg. raw material of <=0.6mm 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.

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) Currently, a blast furnace method is used to produce 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 producing 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 making iron called the smelting reduction method. Among these methods, the method of using a reaction vessel such as a converter that can blow gas upward and blowing oxygen upward while charging iron ore or its pre-reduced product and carbonaceous material is highly effective from the viewpoint of productivity. It is said to be one of the products that has a high possibility of replacing the current blast furnace. This one? In the case of directly using coal as a carbon material, it is possible to use coal called steam coal, which is produced in large quantities, and has the advantage of not requiring expensive equipment such as a chamber coke oven.

(Problems to be Solved by the Invention) FIG. 3 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, a high iron oxide reduction reaction rate and a high heat transfer rate 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 to burn the carbonaceous material 3, is generated. 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 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, for example, in powder form, it is desirable to inject it into the molten layer from the top rather than from the bottom. In this case, since fine powder iron-containing raw materials are easily scattered, coarse grain raw materials are desirable. Raw coal or the like is added as a flux.

The carbonaceous material is usually agglomerated or lump coke, which is directly melted.
The method used is to put it into the fJ& layer.

Using lump coke as the carbon material requires separate coke production equipment, which increases the cost of the carbon material. In addition, when coal is used as a 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 accompanies the gas and rises to the top. It is discharged from the space to the outside of the system. As a result, a phenomenon was observed in which the amount of carbonaceous material used increased.

On the other hand, the use of powdered coal increases the amount of blown gas that scatters out of the system, further reducing the utilization efficiency of the carbon material, making it difficult to use.

In the smelting reduction ironmaking process, which uses a top-blown gas reaction vessel and top-blows oxygen while charging iron ore or its pre-reduced product and carbonaceous material, the issues related to raw materials in the conventional method can be summarized as follows. That's it.

(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) When using lump coal, lump coal 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.

(3) In addition, although the degree of fine iron-containing raw materials is lower than that of coal, compared to coarse iron-containing raw materials, the amount of raw materials containing pulverized iron is scattered out of the system along with the blown gas, and the unit consumption rate increases.

Coal and ores are generally purchased in the form of a powder mixture.

Therefore, for the above-mentioned reasons, effective utilization of powdered materials becomes a problem.

Therefore, major issues regarding the raw materials for the smelting reduction iron manufacturing process are how to prevent pulverization within the molten layer of agglomeration, and how to use raw materials containing powdered coal and fine iron in the final process.

The present invention is an alternative to 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. In the method of manufacturing a carbon-containing alloy by performing
．． This is a smelting reduction iron manufacturing method characterized in that an agglomerate of 2 mm or more obtained by molding a mixture of powdered iron-containing raw materials of 6 m+++ or less is charged into a molten layer from the upper part of a smelting reduction furnace.

(Function) The smelting reduction iron manufacturing method according to the present invention will be described in detail below along with its functions.As the smelting reduction equipment used in the method of the present invention, the equipment shown in FIG. 3 described above can be used.

The carbon material used in the method of the present invention is an air-dried raw material, and the coal is adjusted to a thickness of 1 mm or less, and the powdered iron-containing raw material is adjusted to a thickness of 0.6 mm or less. The powdered raw materials are mixed in a predetermined ratio and then molded using a high-pressure molding machine such as a roll compactor. Then, the agglomerates from which powdery materials of less than 2 mm are removed are used as part of the carbon material and iron raw material in the smelting reduction iron manufacturing process. Powdered matter less than 2 mm during molding is returned to the molding machine and reused.

The particle size of the pulverized coal was set to 1 mm or less because in high-pressure molding machines such as roll compactors, coal particles larger than 1 mm will generate microcracks within the particles due to the pressure during molding, as shown in Figure 1. This is because the strength of the agglomerates decreases as described above.

The particle size of the fine iron-containing raw material was reduced to 0.6 mm or less using a high-pressure molding machine such as a roll compactor. This is because the strength of the agglomerates decreases.

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.

Incidentally, a binder such as pitch is not normally used when molding the powdered raw material, but it may be used if necessary. For example, when producing thick agglomerates, the strength of the agglomerates is reduced because the transmission of pressure to the agglomerate portions is reduced. Therefore, a small amount of binder is used to prevent the strength of the agglomerate from decreasing.

The agglomerate thus produced was heated to 1350'C to 145°C.
When the material was poured into the 0.degree. C. molten layer from above, the degree of powdering was significantly lower than that of agglomeration. As a result, the amount of carbon material scattered 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 lump coal is placed in a high-temperature state such as a molten layer, the 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. This was thought to reduce the internal strain of the agglomerate and reduce its pulverization in high-temperature conditions such as in a molten layer.

As described above, according to the method of the present invention, it is possible to improve the overall efficiency of raw material use, such as reducing the pulverization of carbonaceous materials in the high-temperature molten layer and utilizing powdered raw materials.

Example) The following is a description based on an example. An agglomerate was produced under the conditions shown in Table 3 using steam coal having the components shown in Table 1 and iron ore shown in Table 2.

600g of the agglomerate produced in this way is molten iron or 750k.
The carbonaceous material was poured into the molten layer at 1350° C. from the top using a melting reduction furnace of 1.1 g, and the carbonaceous material was recovered after 5 minutes.

Then, the particle size distribution of the carbonaceous material was measured and the pulverization status was investigated. For comparison, lump coal of 5 to 10 mm was subjected to the same treatment.

Table 1 Analytical properties of coal used (vit, %;) (actual Table 2 Analytical properties of iron ore used (Wt, X) Table 4 shows the particle size distribution of the carbon material after rapid heating.

From this, it can be seen that in the method of the present invention, the ratio of carbonaceous materials with a diameter of 2 mm or less is smaller than in the conventional method, and there is less pulverization of the carbonaceous materials. This indicates that the amount of carbon material scattered is small. Furthermore, it is clear that the method of the present invention can effectively utilize powdered raw materials from the beginning.

Table 3 Conditions for producing agglomerates Table 4 Particle size distribution of carbonaceous material after rapid heat treatment (effects of the invention) By implementing the present invention, it is possible to improve the utilization efficiency of coal and fine iron raw materials in the smelting reduction method,
It is of great industrial significance in terms of economics as well as the fact that it enables practical application.

[Brief explanation of the drawing]

Figure 's1 is a diagram showing the influence of coal particle size on the strength of agglomerates during molding of powdered coal, and Figure 2 is a diagram showing the influence of particle size of fine iron-containing raw material mixed into powdered coal on strength of agglomerates. The figure shown in FIG. 3 is a diagram showing an example of equipment used in the smelting reduction iron manufacturing method. 1... Top blowing lance 2... Bottom blowing tuyere 3...
・Charcoal material 4...Slag 5...Metal
6... Bubbles 7... Refractory lining 4 people Figure 1 Figure 3 Top-blown lance Figure 2 0.0 42-

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.
Agglomerates of 2 mm or more obtained by molding a mixture of powdered coal of 1 mm or less and powdered iron-containing raw material of 0.6 mm or less as carbon material are charged into the molten layer from the upper part of the smelting reduction furnace. Smelting reduction iron manufacturing method.