JPH0428810A - Smelting reduction iron-making method - Google Patents

Abstract

PURPOSE:To reduce unit consumption of carbonaceous material and to improve efficiency of a reduction furnace by arranging a ferro coke production process with pre-reduction process of iron-containing raw material and production process of coke, etc., integrally combined and using the obtd. formed ferro coke as raw material. CONSTITUTION:By using a gas top blowing reaction vessel and using the iron- containing raw material and reducing agent as the raw material and top-blowing oxygen to this, smelting and reduction are executed to produce an iron-carbon- containing alloy. In the above method, the mixed material of powdered iron- containing raw material and powdered coal is carbonized at 600-900 deg.C to obtain the formed ferro coke having 2-100mm grain size. This ferro coke is charged to a fused zone from upper part of the smelting reduction furnace to execute the smelting reduction iron-making.

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 pig iron from iron ore. The blast furnace method is an excellent method for mass production, but it uses coal with excellent caking properties called coking coal, which has limited resources, and carbonizes it in a chamber coke oven. Requires strong coke. Additionally, the Muroni coke oven is extremely expensive equipment, and updating it will require a huge amount of money in the future. Therefore, in the future it will be necessary to develop a method for producing pig iron without using a chamber coke oven.

As one means to solve these problems, research is being carried out on a new method of producing iron called the smelting reduction method. Among them, the method of using a reaction vessel such as a converter that can blow gas upward, and blowing oxygen upward while adding iron ore or its pre-reduced material and carbonaceous materials as iron-containing raw materials, has a high productivity. Therefore, it is considered one of the methods that has a high possibility of replacing the current blast furnace method. Coal, coke or char is used as the carbon material in this method. The coke or char does not need to be of high strength as in the blast furnace process.

Therefore, it is possible to use a large amount of low-caking coal called thermal coal, which is produced in large quantities as coal, and when coke is used as a carbon material, coke can be produced without using an expensive chamber coke oven. can be manufactured.

(Problems to be Solved by the Invention) FIG. 7 shows an example of smelting reduction equipment in the smelting reduction iron manufacturing method. In a container in which gas can be blown upward, such as a converter, oxygen is blown through a top blowing lance. Gas bottom blowing 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 for the present invention cannot be obtained. On the other hand, if this stirring becomes too strong, the oxidizing atmosphere and metal Since the conditions for suppressing contact are disturbed, negative effects appear, such as an increase in the amount of dust generated by iron oxide fumes 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 conventional smelting reduction iron manufacturing method, special steel Vol. 39 No. 1 p.
Coal is used as the carbonaceous material as described in 23-28. An example of the process flow in this case is shown in FIG. 2(b). When pulverized coal is put into the smelting reduction furnace, as mentioned above, a large amount of oxygen gas is blown into the smelting reduction furnace, so combustion in the furnace interior space and scattering outside the system become noticeable, resulting in oxidation. Coal consumption without iron reduction increases. This makes it difficult to use pulverized coal. Therefore, backfilling is usually used. However, in this case as well, the backfill undergoes rapid pyrolysis and becomes powdered within the molten layer. A part of the pulverized coal is discharged into the space above the furnace along with the gas, where it is burned and scattered outside the system. is high, and the coal-equivalent unit consumption of the carbon material is higher than when coke or char is used as the carbon material.

Furthermore, when coal is used, there is a delay in carburization of pig iron, which slows down the reduction reaction and causes a decrease in productivity. Although fine powdered iron-containing raw materials are not exposed to coal, they are scattered outside the system by blown gas. Therefore, fine iron-containing raw materials are not preferred. In addition, in order to reduce the carbon material consumption rate and improve the efficiency of the smelting reduction furnace, CAMP-IS is usually used.
As described in IJ Vol. 2 (1989)-117, the iron-containing raw material is used after being pre-reduced. For this purpose, a separate production facility for pre-reduced products is required.

Furthermore, in the conventional smelting reduction iron manufacturing method, coke is used as the carbonaceous material instead of the above-mentioned coal, as described in Japanese Patent Application No. 62-90894. An example of the process flow in this case is shown in FIG. 2(a). In this case, since powdering of carbonaceous materials such as backfilling is less likely to occur, the increase in the carbonaceous material consumption rate due to powdering is reduced, but additional equipment for producing lump coke or lump char is required. On the other hand, pre-reduced iron-containing raw materials are used to reduce the carbon material consumption rate and improve the efficiency of the smelting reduction furnace. For this purpose, separate preliminary reduction equipment is required. Therefore, in this case, although it is possible to reduce the carbon material consumption rate and improve the efficiency of the smelting reduction furnace, it requires a preliminary reduction process for iron-containing raw materials and a carbonization process to produce coke or char from coal in addition to the smelting reduction process. The smelting reduction ironmaking process becomes complicated. Additionally, equipment costs also increase accordingly.

The present invention aims to provide a method for solving these problems.

(Means for Solving the Problems) The gist of the present invention is to melt and reduce iron-containing raw materials and reducing agents by blowing oxygen over them using a reaction vessel in which gas is blown upward. A method for producing a carbon-containing alloy, characterized in that formed ferro coke obtained by carbonizing a formed product made of a mixture of powdered iron-containing raw material and powdered coal as a raw material is charged into a molten layer from the upper part of a smelting reduction furnace. It is based on the smelting reduction iron manufacturing method.

In the present invention, the carbonization temperature of the molded product is set at 600"C or higher and 90"C or higher.
The particle size of the molded ferro coke is 2 [1
From m1 to 100III [ll or less.

(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. An example of the smelting reduction ironmaking process flow used in the method of the present invention is shown in FIG. We have established a molded ferro coke production process that combines the preliminary reduction process of iron-containing raw materials such as iron ore and the coke or char production process,
The object of the present invention is to provide a smelting reduction method for manufacturing iron-carbon alloy iron using the formed ferro coke produced therein as a raw material for a smelting reduction furnace.

The raw material used in the present invention is a powdered raw material that is a mixture of air-dried powdered coal and powdered iron-containing raw material in a predetermined ratio, and after adding a binder such as tar, pinch, or polyvinyl alcohol as necessary, briquette machine, extrusion molding machine,
Molten coal is produced using roll compactors and other molding machines.

Here, the use of a binder is not absolutely necessary, and there is no need to add it if the briquette is not damaged in the subsequent carbonization process. The thus produced briquette coal is carbonized in a horizontal, vertical or other type of carbonization equipment to produce shaped ferrocoke.

The shaped ferro coke produced in this manner needs to have enough strength to prevent it from becoming powder during the treatment process up to its introduction into the melting reduction furnace.

Here, the particle size of the powdered coal is preferably 3 mm or less.

This is because, as shown in FIG. 3, when the coal particle size exceeds 3 mm, the strength of the formed ferro coke becomes markedly reduced.

The particle size of the powdery iron-containing raw material is preferably 1IXIIl] or less.

Figure 4 shows the relationship between the particle size of iron ore, which is a ferrous raw material, and the strength of formed ferro coke. From now on, the particle size of the iron-containing raw material will be 1 m.
It can be seen that when it exceeds m, the strength of the formed ferro coke decreases significantly.

Further, the carbonization temperature when producing molded ferro coke from the molded product is preferably 600 to 900''C.

This is because if the carbonization temperature is low, the strength of the formed ferro coke will be markedly reduced as shown in FIG. 5, and the preliminary reduction rate of the iron-containing raw material will be low.

When the carbonization temperature exceeds 900° C., the increase in the strength of the formed ferrocoke is small, and on the other hand, equipment costs increase because highly heat-resistant materials are required for high-temperature heating medium manufacturing equipment, carbonization equipment, etc.

Furthermore, an increase in carbonization temperature results in an increase in fuel costs.

These factors increase the manufacturing cost of the product, which is undesirable.

Furthermore, the particle size of the molded ferro coke is 2 strokes or more and 100 mm.
The following are preferred. If the amount is less than 2, as shown in FIG. 6, it will easily accompany the blown gas and be discharged out of the system when the raw material is introduced into the melting reduction furnace. In addition, the particle size is 100m
If it exceeds m, it becomes difficult to produce a molded product with high strength when molding the powdered raw material with a briquette machine or the like, and the quality of the molded ferro coke deteriorates.

As is clear from the above, the method of the present invention provides a smelting reduction method using a high-performance raw material obtained by simultaneously processing a carbonaceous raw material such as coal and a ferrous raw material such as iron ore. In addition, it is possible to utilize fine powder parts of purchased coal, berent feet, dust generated from a smelting reduction furnace, and other dust, which are difficult to use in conventional methods. Further, the iron-containing raw material in the shaped ferro coke is preliminarily reduced during carbonization by the carbonaceous material such as coal coexisting in the shaped product, and a reduction rate of about 40 to 80% can be obtained. Therefore, unlike conventional methods, there is no need to pre-reduce the iron-containing raw material in a separate process.

Therefore, unlike the conventional method shown in FIG. 2(a), there is no need to separately provide a preliminary reduction step for iron-containing raw materials and a carbonization step for coal, and the process can be simplified.

When the formed ferro coke produced in this manner was introduced from above into a molten layer at 1350 to 1450'C in a smelting reduction furnace, the degree of pulverization was significantly reduced compared to backfilling. As a result, the amount of carbonaceous material scattered was significantly reduced, and the basic unit of carbonaceous material was reduced. Furthermore, since the iron oxide in the shaped ferro coke is pre-reduced, the carbon material consumption rate can be reduced to the same degree as conventional pre-reduced iron-containing raw materials, and the productivity of the smelting reduction furnace can be improved.

As described above, according to the present invention, it is possible to simplify the process of the smelting reduction iron manufacturing method, and it is also highly effective in reducing the carbon material consumption rate and improving the productivity of the smelting reduction furnace.

(Example) The following will explain based on an example. Table 1 as carbon material raw material
Powdered coal having the components shown in Table 3 was produced using iron ore having the components shown in Table 2 as an iron-containing raw material under the conditions shown in Table 3.

The molded product was loaded into a vertical carbonization furnace from the top, and a high-temperature inert gas was blown into the bottom of the furnace to carbonize the product until the final temperature of the molded product reached 800°C. Table 4 shows the properties of the obtained shaped ferro coke.

Table 4 Properties of formed ferro coke
The operation was carried out by charging 52 kg/min of formed ferro coke, which had been sieved to a size of 2 to 75 mm, and 17 kg/min of the iron ore shown in Table 2 into a smelting reduction furnace under the conditions shown in Table 5. The reduction rate of iron-containing components in the raw material is approximately 40%).

Table 5 Operating conditions of the smelting reduction furnace As a result, in the case of the method of the present invention described above, the carbon material consumption rate is 1370 kg/molten iron in terms of coal, and the production rate is 30 kg'/9
Pig/min.

For comparison, (a) lump coal 36 with the properties shown in Table 1 as the carbon material.
kg/win, the reduction rate of the ores in Table 2 as iron-containing raw materials is 4
The furnace was operated by charging 32 kg/min of pre-reduced ore reduced to 0%, resulting in a carbon material consumption rate of 1510 kg/min and a production rate of 23 kg/min. Also,(
b) 25 kg/win of coke obtained by carbonizing the coal in Table 1 at a temperature of 800°C as a carbon material, and (a) as a ferrous raw material.
Using the same pre-reduced ore of 38 kg/min, the carbon material consumption rate was 1390 kg/min in terms of coal, and the production rate was 28 kg/min.

From the above, it is clear that the method of the present invention reduces the coal consumption rate and improves the productivity of the smelting reduction furnace.

(Effect of the invention) By implementing the present invention, in the melt reduction method that is being researched as a method to solve the problems of the current blast furnace method,
It was possible to omit the preliminary reduction process for ores, reduce the unit consumption of carbonaceous materials, and increase the efficiency of the smelting reduction furnace. Furthermore, it is clear that powdered raw materials can be used effectively, and it is of great industrial significance in terms of economics and practical application.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an example of the process of the smelting reduction iron manufacturing method according to the method of the present invention, Figures 2 (a) and (b) are diagrams showing an example of the process of the smelting reduction iron manufacturing method using the conventional method, and Figure 3 is a diagram showing an example of the process of the smelting reduction iron manufacturing method using the conventional method. Figure 4 shows the influence of raw material coal particle size on the strength of shaped ferro coke. Figure 4 shows the influence of raw material ore particle size on the strength of shaped ferro coke. Figure 5 shows the influence of raw material coal particle size on the strength of shaped ferro coke. Figure 6 is a diagram showing the influence of briquette carbonization temperature, Figure 6 is a diagram showing the relationship between particle size and scattering rate of formed ferro coke, and Figure 7 is a diagram showing an example of a smelting reduction furnace used in the smelting reduction iron manufacturing method. Formed ferro coke manufacturing process Figure 2 Coke/char manufacturing process Pre-reduced ore manufacturing process Pre-reduced ore manufacturing process (a) (b) Particle size of raw coal dry w: 1 IIL degree <0.7 <10
<100 Liao 11 Reduction furnace feeding side grain skin (-n

Claims (3)

[Claims] (1) In a method of producing an iron-carbon alloy by melting and reducing iron-containing raw materials and reducing agents by blowing oxygen over them using a reaction vessel with top-blown gas, the raw materials are iron-containing powders. A smelting reduction iron manufacturing method characterized by charging molded ferrocoke obtained by carbonizing a molded product made of a mixture of raw material and powdered coal into a molten bed from the upper part of a smelting reduction furnace. (2) The method according to claim 1, wherein the carbonization temperature of the molded product is 600°C or more and 900°C or less. (3) The method according to claim 1, wherein the particle size of the shaped ferro coke is 2 mm or more and 100 mm or less.