JPH1112619A - Method for producing reduced iron - Google Patents

Abstract

(57) [Problem] To provide a method for producing reduced iron efficiently from powdered iron raw material by high-temperature reduction at low cost. A method for producing reduced iron from a powdered iron raw material, characterized by the following steps: A step of mixing a powdered iron raw material and a powdered solid reducing agent to obtain a mixture, forming the mixture into a tile-shaped product 3 by using, for example, a double-roll compression molding machine 2, and placing the mixture on a hearth 5 of a heated reduction furnace 4. Placing the fuel and oxygen-containing gas into the reducing furnace, reducing the powdered iron raw material while maintaining the furnace temperature at 1100 ° C. or higher, and reducing the obtained reduced iron into a reducing furnace. The process of discharging from.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a powdery raw material containing iron oxide as a main component by high-temperature reduction, that is, dust, sludge, scale, etc., containing powdery iron ore and iron generated in an ironworks. Hereinafter, the present invention relates to a method for efficiently producing reduced iron at a low cost from these materials, which are collectively referred to as “powder iron raw material”.

[0002]

2. Description of the Related Art In recent years, as the production of steel products by an electric furnace has become popular, attention has been paid to a technique for obtaining an iron source used as a raw material by solid reduction of iron ore. A typical example of such a technique is to mix powdered iron ore with a powdered solid reducing agent to form agglomerates, so-called “pellets”, which are heated to a high temperature to produce iron ore. There is a technique of reducing iron oxide therein to obtain solid metallic iron (for example, US Pat. No. 3,443,931, Japanese Patent Application Laid-Open No.
-238307).

[0003] The reduction process of fine iron ore disclosed in the above-mentioned US Pat. No. 3,443,931 generally comprises the following steps.

1) A raw pellet is prepared by mixing a powdery solid reducing agent such as coal or coke with a powdery iron ore.

[0005] 2) The raw pellets are heated to a temperature range in which combustible volatile components generated in the pellets do not ignite to remove adhering moisture.

[0006] 3) The obtained dried pellets are reduced by heating to a high temperature, and metallization proceeds.

[0007] 4) The metalized pellets are cooled and then discharged outside the furnace.

However, the above-mentioned US Pat.
The conventional method for producing reduced iron (disclosed as “pellet method” for convenience) as disclosed in US Pat. No. 3,931 has basically the following problems.

1) Since the strength of the agglomerate (pellet) cannot withstand handling if it is agglomerated, it is necessary to dry the pellet before charging it into the reduction furnace. Therefore, in addition to the agglomeration equipment having a complicated mechanism, a drying equipment is required, and the cost of operation and maintenance thereof becomes considerable. Further, since the time required from the drying of the pellets to the end of the reduction becomes long, the production efficiency is low and it is difficult to keep the production cost of reduced iron low.

2) It is inevitable that particles other than a predetermined size are formed during agglomeration. The undersize has to be returned to the mixing step as it is, and the oversize has to be pulverized and returned to the mixing step, so that the production efficiency is poor.

3) Dust, sludge, scale, etc. containing iron generated in steelworks (hereinafter, these are collectively referred to as "waste oxide" in steelworks) are also valuable iron sources. The oxides discharged from the steelworks in the as-collected form often have a shape that is too large to be pelletized, such as a lump formed by combining powdery substances or a mill scale. Therefore, when these are used alone or mixed with fine iron ore in place of fine iron ore and agglomerated into pellets, they need to be finely pulverized to a predetermined particle size in advance, and a fine pulverizing facility is indispensable. I can't.

Since the reduction reaction of the pellets proceeds faster as the temperature increases, in order to increase the reduction reaction rate and improve the productivity, it is necessary to increase the temperature rising rate of the pellets and quickly reach the predetermined temperature. It is important. In the method proposed in the above-mentioned Japanese Patent Application Laid-Open No. 7-238307, an oxygen-containing gas is supplied to the surface of the charged pellet for a while after the pellet is charged into the furnace, and the flammable gas generated from within the pellet is supplied. The active material is actively burned, and the surface heat of the pellets is quickly raised to an appropriate reduction temperature by the heat of combustion.

However, the method disclosed in Japanese Patent Application Laid-Open No. 7-238307 is also in the category of the "pellet method" which involves the steps of mixing, agglomerating, and drying the raw materials, and the problems of the pellet method are almost solved. It has not been.

As described above, the conventional "pellet method" has many problems.

[0015]

SUMMARY OF THE INVENTION An object of the present invention is to produce reduced iron at a low cost by a simple method instead of the conventional "pellet method". The specific object of the present invention is to reduce the raw material form in the case of subjecting the powdered iron raw material to reduction to pellets, instead of pellets, to charge the raw materials in a reduction furnace and reduce the temperature at a high temperature. An object of the present invention is to provide a method for producing reduced iron that has solved the problems.

[0016]

Means for Solving the Problems As a result of repeated studies to solve the above-mentioned problems, the present inventors provide a powdery iron raw material mainly containing iron oxide such as powdered iron ore for reduction. In this case, it is effective to use a tile-shaped product instead of agglomerates (pellets) as in the past, place it directly on the hearth of a reduction furnace, and reduce it at a high temperature. It was found that a reduction result almost equivalent to that in the case of reducing pellets was obtained.

The present invention has been made based on the above findings, and the gist of the present invention resides in a method for producing reduced iron from a powdered iron raw material, characterized by the following steps.

A step of mixing a powdered iron raw material and a powdered solid reducing agent to obtain a mixture; a step of forming the mixture into a tile shape and placing the mixture on a hearth of a heated reduction furnace; The fuel and the oxygen-containing gas are blown into the furnace, and the blown fuel, the combustible volatile component generated from the powdered solid reducing agent, and the CO gas generated by reducing the powdered iron raw material are blown into the furnace. Combustion by gas, maintaining the temperature inside the furnace at 1100 ° C or higher,
A step of reducing the powdered iron raw material; and a step of discharging the reduced iron obtained in the reduction step from a reduction furnace.

Here, the "pulverized iron raw material" is a powdered iron raw material containing iron oxide as a main component, and specifically includes the above-mentioned powdered iron ore and iron generated in an ironworks. Dust, sludge, scale, etc. In the present invention, these can be used alone or in a mixture of two or more.

The "powder solid reducing agent" is a powder of a solid substance mainly containing carbon such as coal, charcoal, coke (including petroleum coke). These can also be used alone or in combination of two or more.

As preferred embodiments of the method of the present invention, the following methods can be employed alone or in combination.

[Preferred Embodiment 1] In the step of mixing the powdered iron raw material and the powdered solid reducing agent to obtain a mixture, a binder is added.

[Preferred Embodiment 2] Irregularities are formed on the surface of the tile-shaped molded product opposite to the surface in contact with the hearth.

[Preferred Embodiment 3] After the surface of the tile-shaped molded product is coated with a powdery solid reducing agent, the fuel and oxygen-containing gas are blown into the furnace.

[Preferred Aspect 4] When the tile-shaped molded product is placed on the hearth of a heated reduction furnace and heated, the tile-shaped molded product is generated during the generation of the flammable volatile components generated from the solid reducing agent in the tile-shaped product. An oxygen-containing gas is supplied to the surface of the tile-shaped product, and combustible volatile components are burned on the surface to promote the temperature rise of the tile-shaped product.

[Preferred Embodiment 5] A powdery solid reducing agent is thinly spread on a hearth of a reducing furnace, and a tile-like molded product is placed thereon.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The feature of the method of the present invention is that, when producing reduced iron from powdered iron raw material, the form of the raw material to be charged into the reduction furnace is not formed into agglomerates (pellets), but tile-shaped. The material is placed on the hearth as it is and reduced at high temperature.

Hereinafter, the method of the present invention will be described in detail in the order of the above steps.

1. Step: In reducing the powdered iron raw material at a high temperature, the powdered iron raw material and the powdered solid reducing agent are mixed in advance.

However, depending on the conditions of the powdered iron raw material and the moisture originally contained in the solid reducing agent, when mixing the powdered iron raw material with the powdered solid reducing agent, some water and other By adding one or both of the binders, uniform and quick mixing is facilitated, and scattering of fine powder from the surface of the mixture can be effectively prevented. Further, the formation into a tile in the next step is facilitated, and the generation of powder when the tile-shaped product is charged into the reduction furnace is reduced.

When dust containing zinc (Zn) or the like is used as a raw material, there is a concern that Zn will remain in the reduced iron of the product and the product value will be reduced. Due to the high temperature, low-boiling metals such as Zn evaporate and are discharged out of the furnace together with the exhaust gas. Therefore, the amount of these low-boiling metals remaining in the product reduced iron can be reduced, and the product quality can be improved.At the same time, the dust collected by the dust collection equipment is concentrated in these low-boiling metals, so Can be recovered and used.

2. Step: The mixture obtained in the previous step is formed into a tile and placed on the hearth of a heated reduction furnace.

The means for forming into a tile shape is not particularly limited, but it is desirable to use a double-roll compression molding machine because the equipment is simple and the molding can be performed easily and efficiently.

The width of the tile-shaped molded product may be appropriately determined according to the scale of the reduction furnace. The thickness is generally 10-20m
m is preferable.

The tile-shaped product is placed on the hearth of a heated reduction furnace. There is no particular restriction on the type of reduction furnace,
In terms of workability, a rotary hearth furnace (rotary hearth furnace)
Is recommended.

FIG. 1 is a cross-sectional view of a part of a rotary hearth furnace, schematically showing a state in which a tile-shaped product is placed on a hearth. As shown in the figure, a mixture of a powdered iron raw material, a powdered solid reducing agent, and a binder is supplied from a hopper 1 to a double roll compression molding machine 2 to be formed into a tile shape, and the tile-shaped molded product 3 is continuously processed as it is. It is placed on the hearth 5 of the reduction furnace 4. Reference numeral 6 in the figure is a heat shield plate. If the reduction furnace is a rotary hearth furnace, such a continuous operation can be advantageously performed.

3. Step: The powdered iron raw material mixed with the reducing agent in the above steps and formed into a tile shape is reduced. That is, the fuel and the oxygen-containing gas are blown into the furnace, and the blown fuel, the combustible volatile component (VM) generated from the powdered solid reducing agent and the CO gas generated by reducing the powdered iron raw material are burned. And the furnace temperature is 1100 ° C
While maintaining the above, the powdered iron raw material formed into a tile is reduced to produce reduced iron.

As the fuel, a commonly used fuel such as natural gas or heavy oil can be used. However, the fuel is not limited to this, and a combustible gas generated in a steel mill may be used.

As the oxygen-containing gas, it is preferable to use air or a gas whose oxygen concentration is equal to or slightly richer than the air composition.

The furnace temperature for performing high-temperature reduction is 110
0 ° C or higher. The reduction proceeds even in a temperature range lower than 1100 ° C., but in such a temperature range, the reduction rate is slow, which is not preferable for industrial production. During the reduction of the iron oxide, the temperature of the charged bed becomes lower than the temperature in the furnace due to the endothermic reaction.
It is desirable to maintain the temperature at about 200 to 1400 ° C.

However, this temperature is a property to be adjusted according to the progress of the reduction, the properties and the mixing ratio of the iron raw material and the solid reducing agent to be used, and the like. That is, in the period immediately after the raw material (tile-shaped molded product) enters the furnace interior, the temperature of the tile-shaped molded product is low, so that the temperature in the furnace is kept high to raise the temperature of the tile-shaped molded product. It is more advantageous to promote reduction.

Further, since the melting points of the gangues in the ore and the ash in the coal are varied depending on the composition of the raw materials, the temperature in the furnace is controlled in accordance with the composition, and the material is not dissolved and flows out during the reduction. It should be noted that However, the generation of an appropriate amount of melt in the tile-shaped molded article gives good results in both heat transfer and reaction promotion, and should be actively utilized. In the case of using pellets, when the melt is generated, the pellet strength is reduced and large plastic deformation is exhibited, and the pellet particles are fused to each other, making it difficult to handle.However, there is no concern about the method of the present invention. .

The heating holding time (reduction time) required for the reduction is governed by various factors such as the type of the iron raw material, the thickness of the tile-shaped product, the heating temperature, and the like. Roughly the reduction time obtained in a small test can be used as a guide,
It is recommended to determine the optimal return time by accumulating operation results.

4. Step: The reduced iron obtained in the above step is discharged from the reduction furnace. In this case, if the temperature of the tile-shaped molded product at the time of discharge is 1170 ° C. or more, there is a possibility that a melt exists in the tile-shaped molded product, which may hinder the discharge operation. Before discharging, it is desirable to stop heating so that the temperature in the tile-shaped molded product falls below 1170 ° C. In addition, as a method of lowering the temperature in the bed below 1170 ° C. in a short time, there are various methods such as a method of blowing an inert gas such as a normal temperature reducing gas or nitrogen onto the bed surface and a method of bringing a water cooling plate into contact with the bed surface. The method can be adopted.

In the method of the present invention, as described above, the form of the raw material to be charged into the reduction furnace is a tile-like molded product, which has the following advantages.

First, when pellets are used as the raw material at the time of entering the furnace interior, since the strength is insufficient as it is, it is necessary to increase the strength by drying to prevent collapse during handling. If it is placed on the hearth as a material, it will not collapse without going through a drying step. In addition, even if a small amount of cracks are formed when water or the like evaporates due to exposure to the high temperature in the furnace, it does not lead to a large collapse and does not hinder the reduction.

In the case of pelletizing, as described above, generation of particles having a size other than a predetermined size cannot be avoided. Undersized particles are directly returned to the mixing step.
Oversized particles need to be returned to the grinding process,
When forming into a tile, there is no need to do so, and efficient production can be performed.

Further, when pelletizing, it is necessary to make the raw fuel into fine particles, but when forming into a tile, there is no need to pulverize it. However, no fine pulverizing equipment is required.

Compared to the case where the powdered iron raw material is pelletized, there is an advantage that the speed of forming into a tile is remarkably fast, efficient, and the equipment can be made compact.

That is, the raw material adjustment (fine pulverization, particle size adjustment), agglomeration (pelletization) step, and drying performed by the conventional “pellet method” according to the method of the present invention using a powdered iron raw material as a tile-shaped molded product. The steps can be omitted, and the production efficiency can be greatly improved, and the production cost of reduced iron can be significantly reduced.

Next, a preferred embodiment of the method of the present invention will be described.

[Preferred Embodiment 1] When a mixture of the powdered iron raw material and the powdered solid reducing agent is formed into a tile shape, the strength of the formed product is insufficient, so that a part of the mixture is charged into a rotary hearth furnace. May break down and become shards, or generate powder.

In order to solve this problem, a method of adding a binder when mixing the powdered iron raw material and the powdered solid reducing agent to improve the strength of the tile-shaped molded product can be adopted. In addition to water, any of inorganic binders such as bentonite and lime and organic binders such as tar can be used as the binder. These may be used alone or in combination of two or more.

[Preferred Embodiment 2] When molding the powdered iron raw material into a tile shape, if the thickness of the tile-like molded product is too large, the rate of temperature rise in the molded product is reduced and the reduction is delayed, so that it is a good idea. is not.

In order to solve this problem, as shown in FIG. 2 as an example, the upper surface of the tile-shaped product 3 (the surface opposite to the surface in contact with the hearth) is made uneven to increase the heat receiving area. It is effective to use the method.

In addition, when the upper surface of the tile-shaped molded article is made uneven, the amount of raw material loaded per unit area of the hearth increases, so that a good result that productivity is improved can be obtained.

[Preferred Embodiment 3] The same can be said for the conventional method of reducing the pelletized raw material at a high temperature. However, since the oxygen-containing gas is continuously blown into the furnace during the high-temperature reduction of the tile-shaped molded product, the high-temperature reduction is performed. It is feared that the surface of the reduced iron inside is reoxidized and the metallization ratio of the resulting reduced iron product is not sufficiently improved.

In order to prevent the reoxidation of the reduced iron surface during such high-temperature reduction, it is effective to adopt a method in which the surface of the tile-like molded product is covered with a powdery solid reducing agent. It is. At this time, the upper surface of the tile-shaped molded product placed on the hearth (the surface opposite to the surface in contact with the hearth) may be coated with a powdery solid reducing agent. When forming a mixture of iron-based raw material, powdered solid reducing agent, and a binder to be added as needed into a tile shape, it is recommended that the surface be covered with a powdered solid reducing agent mixed with a binder. You.

[Preferred Aspect 4] In order to reduce the reduction time of the powdered iron raw material (iron oxide) in the tile-shaped molded product on the hearth, the temperature of the tile-shaped product is quickly raised to the appropriate reduction temperature. It is desirable. For that purpose, when heating the tile-shaped molded product, combustible volatile components generated from the solid reducing agent in the tile-shaped molded product are burned on the surface of the tile-shaped molded product, and heating is also performed by using the combustion heat. Is advantageous. In other words, a combustible volatile component (VM) is generated in a gaseous state by heating from a solid reducing agent such as coal, but this is diffused into the space inside the furnace and then burned, rather than being burned. Combustion at is advantageous for heating the bed. This combustion on the bed surface can be realized by blowing an oxygen-containing gas such as air onto the bed surface after the bed is formed.

When an oxygen-containing gas is sprayed on the surface of the tile-shaped molded product, reoxidation of the reduced iron oxide is concerned. In order to prevent this, a combustible volatile component from the solid reducing agent is required. It is effective to spray an oxygen-containing gas only during the period of occurrence. During this period, the surface of the tile-shaped molding is covered with a relatively large amount of flammable volatile components,
Oxygen in the blown oxygen-containing gas is preferentially consumed for combustion of combustible volatile components, and as a result, reoxidation can be prevented.

The combined use of this method and the above-mentioned "method of making the surface of a tile-shaped molded product covered with a powdery solid reducing agent" is more effective in preventing reoxidation.

The oxygen-containing gas supplied directly to the surface of the above-mentioned tile-shaped molded product is also air or a gas whose oxygen concentration is adjusted to be equal to or slightly richer than air as described above. Good. In order to improve the rate of temperature rise of the tile-shaped molded product, it is possible to use an oxygen-containing gas and a fuel at the same time after securing the amount of oxygen necessary for burning the combustible volatile components.

After the generation of the volatile components from the solid reducing agent is completed, the temperature inside the furnace becomes 1100 ° C. or higher, preferably 1200 hours, by burning the fuel blown from outside the furnace.
What is necessary is just to heat up to 1400 degreeC or more. Thereby, the reduction of the iron oxide proceeds promptly in the furnace, and the reduced iron is produced.

[Preferred Aspect 5] When the method of the present invention is carried out, the tile-shaped molded product may adhere to the hearth refractory on which the tile-shaped product is mounted, which may hinder the subsequent work.

In order to solve this problem, it is effective to employ a method in which a powdery solid reducing agent is firstly spread thinly on the hearth of a reducing furnace, and a tile-like molded product is placed thereon. This is because sticking is effectively prevented by the powdery reducing agent interposed between the tile-shaped molded product and the hearth refractory.

[0066]

EXAMPLE A powdered iron raw material having the composition shown in Table 1, coal (pulverized coal) as a powdered solid reducing agent shown in Table 2, and bentonite as a binder shown in Table 3 were prepared. The forms of iron oxides in iron ore A and iron ore B in Table 1 are hematite (Fe ₂ O ₃ ) and magnetite (Fe ₃
O ₄ ). Table 4 shows the particle size composition of the powdered iron raw material and the coal.

[0067]

[Table 1]

[0068]

[Table 2]

[0069]

[Table 3]

[0070]

[Table 4]

Bentonite was added to the powdered iron ore and the coal to obtain a mixed raw material having a mixing ratio shown in Table 5, and then, using a double roll compression molding machine, a thickness of 15 mm and a width of 150 mm.
The tile-shaped molded product having a length of 150 mm and the same width and length as those of the tile-shaped molded product, but were formed into a tile-shaped molded product having irregularities of the shape shown in FIG. 2 on the surface thereof.

For comparison, a part of the mixed raw material was made into a raw pellet having a diameter of 18 mm using a pan-type pelletizer, and then heated to 115 ° C. to obtain a dry pellet from which water was removed by 90% or more.

[0073]

[Table 5]

These tile-shaped molded products and pellets were subjected to a reduction test under the conditions shown in Table 6 using a small high-temperature heating reduction test furnace. The “average furnace temperature” in Table 6 is the average gas temperature in the furnace space after the blowing of the oxygen-containing gas onto the surface of the tile-shaped product or pellet is stopped.

FIG. 3 is a schematic longitudinal sectional view of the test furnace used, and FIG. 4 is a sectional view taken along line BB of FIG. As shown in the drawing, burners are installed in the upper and lower stages in the high-temperature heating and reducing test furnace 7, and the lower burner 9 emits air as an oxygen-containing gas only during the period in which flammable volatile components are generated from the solid reducing agent. Tiles or pellets (FIGS. 3 and 4)
In this example, the tile-shaped molded article 3 is sprayed on the surface of the molded article 3 to burn the combustible volatile components. When the generation of the flammable volatile components was completed, the use of the lower burner 9 was stopped. On the other hand, the upper burner 8 is a heating burner for maintaining the temperature in the furnace at a predetermined temperature.

Although the test furnace is of a fixed type, the burners are installed in two stages above and below. However, in the case of a rotary hearth furnace, there is no need to use two stages, and only one stage may be used. That is, in the rotary hearth, the oxygen-containing gas blows against the surface of the tile-shaped molded product at the angle of the burner installed in the flammable volatile component generation section located downstream of the charging portion of the tile-shaped molded product. Should be at an appropriate angle. Further, it is advantageous that the oxygen-containing gas blown into the furnace is heat-exchanged with exhaust gas and preheated to about 500 to 600 ° C. before being blown.

In the reduction test, the target value of the metallization ratio was 92%
Was set, and the reduction time that could achieve this target value was measured. The results are shown in Table 6 above.

The test was first performed under the conditions of “test number 1”. As a result, it was confirmed that a metallization ratio of 92% could be achieved if the reduction time was about 15 minutes without pelletization. This reduction time may be extremely short as compared with a reduction time of about 8 to 10 hours in a shaft furnace type direct reduction method using a reducing gas obtained by reforming ordinary natural gas. Is shown.

"Test No. 2" was a case where the upper surface of the tile-shaped molded product was made uneven, and the reduction time was almost the same as that of "Test No. 1". Was increased by about 1.9 times, and it was confirmed that productivity was also improved by about 1.9 times. This is because even if the raw material loading amount per unit area of the hearth is about 1.9 times, the heat receiving area is increased by the unevenness formed on the upper surface of the tile-shaped molded product, and the convex part is heated from both sides. This is considered to be due to the fact that the rate of temperature rise was improved.

"Test No. 3" and "Test No. 4" were obtained by thinly coating the surface of the tile-shaped product with pulverized coal and then reducing the temperature at a high temperature. The reduction time was the same as in "Test No. 1". Nevertheless, the metallization rate was improved by about 1%, and it was confirmed that the coating with pulverized coal was effective in preventing the re-oxidation of the surface of the tile-shaped product. In addition, "Test No. 3" is a case where the tile-shaped molded product was placed on the hearth and then the surface was covered with pulverized coal, and "Test No. 4" was obtained by mixing a binder when forming into a tile shape. This is the case where it is covered with pulverized coal.

[Test No. 5] indicates that after the tile-shaped molded product was charged into the furnace, the generation of flammable volatile components in the coal continued for about 2 hours.
In this case, air is supplied to the surface of the tile-shaped molded product for only minutes, and the combustible volatile components generated from coal are also burned on the surface of the tile-shaped molded product.

As a result, the reduction time was 12 minutes, which was further shortened by 3 minutes from the 15 minutes in “Test No. 1”, and the burning of the combustible volatile components generated from the tile-like molded product was reduced by the surface of the tile-like molded product. However, it was possible to confirm the advantage of the method of heating and raising the temperature while performing.

"Test No. 6" is a case where a conventional dry pellet was used. The reduction time in this case was 10 minutes, which was slightly shorter than in the case of "Test No. 5." This is presumably because the pellets were used after being dried, while the tile-shaped products were used without being dried. However, when pellets are used, drying for a relatively long time outside the furnace is required, so that the processing time is spent correspondingly, which is not an advantage.

Therefore, the result of “Test No. 6” shows that the method of the present invention using a powdery raw material as a tile-shaped molded product is inferior to the case of using agglomeration (pelletization). It can be said that there is no reduction method.

"Test No. 7" is a case where the ore B (the form of iron oxide is magnetite) shown in Table 4 was used.
The reduction time at this time was 11 minutes, which was slightly shorter than that of "Test No. 5" (ore A in which the form of iron oxide was hematite). This is because although the reduction of magnetite and hematite to metallic iron is an endothermic reaction, the heat of reaction per iron atom is about 4760 kca for magnetite.
It is considered that the temperature drop in the tile-shaped molded product was small due to the small l / kmol, and as a result, the reduction reaction was promoted.

"Test No. 8" is a case where an iron raw material in which ore A is blended with dust generated in an ironworks is used, and "Test No. 9" is a case where an iron raw material in which dust and mill scale are blended is used.

The reduction times were about 12 minutes and 11 minutes, respectively.
Minutes, the result was almost the same as that of “Test No. 5” using iron ore.

The reason why the mixed material S of Test No. 9 was slightly coarse but the reduction time did not change so much was that the form of iron oxide in the mixed material S was FeO, so that Fe ₂ O ₃
Is about 30%, and the amount of reduction to metallic iron can be reduced, and the reaction endothermic amount per Fe atom from FeO to metallic iron is smaller than that of Fe ₂ O _3. About 20590 kcal / kmol, the temperature drop in the tile-shaped molded product is small, and as a result,
It is considered that the reduction reaction was promoted.

The Zn removal ratio in Test No. 8 using dust containing Zn was 92%, and the Zn removal effect by the method of the present invention could be confirmed.

In these tests, when the tile-shaped molded product was placed on the hearth of the reduction furnace, first, a powdered solid reducing agent such as powdered coal was spread, and the tile-shaped molded product was placed thereon. It was also confirmed that adopting the method of performing high-temperature reduction by placing the apparatus can sufficiently prevent the tile-shaped molded product and the hearth from sticking due to high-temperature heating, which sometimes occurs.

[0091]

[Table 6]

[0092]

According to the method of the present invention, reduced iron can be produced efficiently and at low cost from a powdered iron raw material containing iron oxide such as fine iron ore as a main component by high-temperature reduction.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a part of a rotary hearth furnace, schematically illustrating an example of a state in which a tile-shaped product is placed on a hearth.

FIG. 2 is a diagram showing an example of the shape of a tile-shaped product supplied to a rotary hearth furnace.

FIG. 3 is a schematic vertical sectional view of a high-temperature heating reduction test furnace used in Examples.

FIG. 4 is a cross-sectional view of the high-temperature heat reduction test furnace shown in FIG.

[Description of Signs] 1: Hopper 2: Double roll compression molding machine 3: Tile molding 4: Reduction furnace 5: Hearth 6: Shielding plate 7: High-temperature heating reduction test furnace 8: Upper burner 9: Lower burner

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshihisa Nakamura 4-5-33 Kitahama, Chuo-ku, Osaka City, Osaka Sumitomo Metal Industries, Ltd.

Claims (6)

[Claims] 1. A method for producing reduced iron from a powdered iron raw material, characterized by the following steps: A step of mixing a powdered iron raw material and a powdered solid reducing agent to obtain a mixture, forming the mixture into a tile, and placing the mixture on a hearth of a heated reduction furnace; The oxygen-containing gas is blown, and the injected fuel, combustible volatile components generated from the powdered solid reducing agent, and CO gas generated by reducing the powdered iron raw material are burned by the oxygen-containing gas blown into the furnace. And maintaining the temperature in the furnace at 1100 ° C. or higher,
A step of reducing the powdered iron raw material; and a step of discharging the reduced iron obtained in the reduction step from a reduction furnace. 2. The method for producing reduced iron according to claim 1, wherein a binder is added in the step according to claim 1. 3. The process according to claim 1, wherein the surface of the tile-shaped molded product is provided with irregularities on the surface opposite to the surface in contact with the hearth. Production method. 4. The method according to claim 1, wherein after the surface of the tile-like molded product is coated with a powdery solid reducing agent, fuel and oxygen-containing gas are blown into the furnace. The method for producing reduced iron according to any one of the above. 5. The process according to claim 1, wherein an oxygen-containing gas is supplied to the surface of the tile-shaped product while the combustible volatile component generated from the solid reducing agent in the tile-shaped product is generated. The method for producing reduced iron according to any one of claims 1 to 4, wherein a combustible volatile component is burned on its surface to promote the temperature rise of the tile-shaped molded product. 6. The process according to claim 1, wherein a powdery solid reducing agent is thinly spread on a hearth of the reducing furnace, and a tile-like molded product is placed thereon. 6. The method for producing reduced iron according to any one of items 1 to 5.