WO2012049974A1

WO2012049974A1 - Process for production of reduced iron

Info

Publication number: WO2012049974A1
Application number: PCT/JP2011/072310
Authority: WO
Inventors: 幸弘上杉; 直史寺本; 祐輝 ▲桑▼内
Original assignee: 新日本製鐵株式会社
Priority date: 2010-10-14
Filing date: 2011-09-29
Publication date: 2012-04-19
Also published as: JP5423645B2; JP2012082493A; KR20130080844A; CN103154276A; BR112013008360A2

Abstract

This process for producing reduced iron comprises: a kneading step of adding water having a temperature of 60-90˚C inclusive to a mixture comprising a powdery iron oxide raw material and a powdery reducing material and kneading the resulting mixture; a granulation step of granulating the mixture obtained in the kneading step to produce a granulated material; and a reduction step of reducing the granulated material obtained in the granulating step to produce reduced iron.

Description

Method for producing reduced iron

The present invention relates to a method for producing reduced iron.
This application claims priority based on Japanese Patent Application No. 2010-231512 filed in Japan on October 14, 2010, the contents of which are incorporated herein by reference.

In the steelmaking and steelmaking processes, dust that is generated mainly in blast furnaces, converters, electric furnaces, melting furnaces, etc., containing iron as a main component is reused as a raw material.

In order to use the solid iron-containing cold material such as dust as a raw material, after mixing the reducing material to the iron oxide raw material that is the collected solid iron-containing cold material, kneaded, then through agglomeration treatment An agglomerated product is produced, and then the agglomerated product is reduced to produce reduced iron (see, for example, Patent Document 1 below).

Japanese Unexamined Patent Publication No. 2009-97065

However, in the method for producing reduced iron as described in Patent Document 1 described above, a mixture of raw materials may not be agglomerated during the granulation process for agglomeration, and powder may remain. There was a problem when further improving the granulation property.

The present invention has been made in view of the above problems, and the object of the present invention is to further improve the granulation property when agglomerating a mixture as a raw material for reduced iron. It is providing the manufacturing method of reduced iron.

In order to solve the above problems, the present invention employs the following aspects.
(1) That is, in the method for producing reduced iron according to one embodiment of the present invention, water at 60 ° C. or more and 90 ° C. or less is added to a mixture containing an iron oxide raw material and a reducing material that are both in powder form and kneaded. A kneading step to perform; a granulation step to agglomerate the mixture after the kneading step to obtain an agglomerate; a reduction step to reduce the agglomerate after the granulation step to produce reduced iron; Have The moisture referred to in the present invention includes water and water vapor.

(2) In the kneading step according to the aspect described in (1) above, a binder soluble in water may be further added to the mixture.

(3) In the case of (2) above, the binder may be a liquid organic binder or a powdery organic binder.

(4) In the case of (3) above, the binder may be a powdered organic binder and a cereal starch selected from the group consisting of rice, tapioca, rye and corn.

(5) In the kneading step according to the aspect described in (1) above, the water content of the mixture may be 6% to 9% by adding the water.

(6) The particle diameter of the mixture before kneading in the kneading step in the aspect described in (1) may be 70 μm to 500 μm with an 80% particle diameter under a sieve.

(7) The water content of the mixture before the water is added in the kneading step in the aspect described in (1) may be 1% to 3%.

According to the above aspect of the present invention, when the mixture containing the iron oxide raw material and the reducing material is granulated, moisture of 60 ° C. or more and 90 ° C. or less is added to the mixture. Uniformity can be achieved, and the granulation property in the granulation step can be further improved.

It is explanatory drawing for demonstrating an example of the manufacturing process of reduced iron. It is a flowchart for demonstrating each process of the manufacturing method of reduced iron which concerns on one Embodiment of this invention. It is the graph which showed the time required for the penetration | invasion of the water | moisture content to a mixture. It is the graph which showed the ratio of the lump which exists in a mixture. It is the graph which showed the change of the dissolution ratio to the water | moisture content of a corn starch. It is the graph which showed the change of the intensity | strength after drying of an agglomerate.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the moisture includes water and water vapor.

<About the manufacturing process of reduced iron>
Prior to describing the method for producing reduced iron according to the present embodiment, the production process of reduced iron will be described in detail with reference to FIG. Drawing 1 is an explanatory view for explaining an example of a manufacturing process of reduced iron.

Iron oxide raw materials such as iron dust and iron ore collected from each facility in the steelworks and reducing materials such as coal, coke, and fine carbon are stored in the hopper 11 and the like in advance. The iron oxide raw material and the reducing material are blended so as to have a preset blending ratio, and then charged into the pulverizer 13.

A pulverizer 13 typified by a vibration mill such as a ball mill pulverizes the charged iron oxide raw material and the reducing material to a predetermined particle size while mixing. The particle sizes of the iron oxide raw material and the reducing material after pulverization may be appropriately set according to values suitable for a reducing furnace such as a rotary hearth furnace and a rotary kiln used for producing reduced iron. The mixture of the pulverized iron oxide raw material and the reducing material is conveyed to the kneader 15.

The kneader 15 receives and kneads the mixture pulverized to a predetermined particle size by the pulverizer 13. In addition, the kneading machine 15 often performs a humidity conditioning process for adding water to the mixture until the water content is suitable for charging into a reduction furnace used for producing reduced iron. An example of the kneading machine 15 is a mix muller, but various types of kneading machines can be used besides this. The mixture kneaded by the kneader 15 is conveyed to the molding machine 17.

A molding machine 17 such as a pan pelletizer (dish granulator), a double roll compressor (briquette making machine), an extrusion molding machine, etc. accepts and molds a mixture containing an iron oxide raw material and a reducing material, such as pellets and briquettes. Agglomerates like Here, the agglomerated material refers to pellets, briquettes, extruded products that have been cut by extrusion molding, and granular materials / agglomerated materials such as mass-adjusted agglomerated materials. The molding machine 17 agglomerates the mixture so that the mixture does not scatter in the furnace ascending gas flow when, for example, it is heated and charged into the melting furnace 23 after drying and heating reduction described later. . The generated agglomerated material is charged into the dryer 19.

The dryer 19 receives the agglomerated material from the molding machine 17 and dries it. The moisture content is suitable for the heating reduction process described later (in other words, the moisture content suitable for each reduction furnace used for producing reduced iron). : For example, 1% or less). The agglomerated product adjusted to a predetermined moisture content is conveyed to a reduction furnace 21 described later.

For example, a reduction furnace 21 such as a rotary hearth furnace (RHF) or a rotary kiln heats and reduces the charged agglomerate in a heating atmosphere using an LNG burner, a COG burner, or the like, and reduces the agglomerate. It will be iron. The reducing furnace heats the agglomerate to, for example, about 1000 to 1300 ° C. to reduce the agglomerate and produce reduced iron. The manufactured reduced iron is conveyed to the melting furnace 23.

The melting furnace 23 melts the reduced iron supplied from the reduction furnace 21 in the state of, for example, a high-temperature pellet to form molten iron. Thus, the hot metal produced | generated by the melting furnace 23 is conveyed using a ladle etc., and after using a desulfurization and refining process, it is utilized as crude molten steel.

<About the manufacturing method of reduced iron>
Based on the above description, the method for producing reduced iron according to the present embodiment will be described in detail below.

[Outline of reduced iron production method according to this embodiment]
As described above, the method for producing reduced iron according to the present embodiment produces reduced iron by heating and reducing agglomerates formed by mixing an iron oxide raw material and a reducing material. As the iron oxide raw material according to the present embodiment, iron dust (e.g., iron-containing cold material melting converter, refining converter, dust melting converter, etc. is generated and collected by a wet dust collector or the like). Converter dust, blast furnace dust, mill scale, electric furnace dust, etc.), non-ferrous smelting dust, and iron ore. Further, as the reducing material according to the present embodiment, for example, coal such as pulverized coal, carbon material such as coke, and fine carbon can be used.

Here, in the production process of reduced iron according to the present embodiment, during the granulation process using the granulator, the raw material mixture may not be agglomerated and powder may remain. Such residual powder hinders the improvement of granulation performance in the granulation process. Therefore, as a result of intensive studies aimed at improving granulation properties in the granulation step, the present inventor added water at a temperature of 60 ° C. or higher and 90 ° C. or lower to the raw material mixture during the granulation step. Thus, the inventors have conceived that it is possible to improve the granulation property in the granulation step.

As will be described in detail below, as a result of the study by the present inventors, by using moisture at 60 ° C. or higher and 90 ° C. or lower in the granulation step, the surface tension is lowered, the hydrophilicity is increased, It becomes possible to improve the moisture diffusion efficiency into the mixture by increasing the movement of the water, making it possible to improve the water permeability to the mixture containing the iron oxide raw material and the reducing material. It became clear that By improving the diffusion efficiency like this, it becomes possible to make the distribution of moisture present in the mixture containing the iron oxide raw material and the reducing material more uniform than before, and improve the granulation properties during granulation. It becomes.

Furthermore, as a result of the study by the present inventor, by using moisture at a temperature of 60 ° C. or higher and 90 ° C. or lower during the granulation step, not only the granulation property is improved, but also the strength of the agglomerated product to be produced is increased. It has also been found that it is possible to improve compared to the prior art. In the method for producing reduced iron as described above, various binders have been added to the mixture of the oxide raw material and the reducing material in order to improve the strength of the agglomerated material. . However, like the method for producing reduced iron according to the present embodiment, by adding moisture at a temperature of 60 ° C. or more and 90 ° C. or less to the mixture in the granulation step, the diffusion efficiency of moisture into the mixture is dramatically increased. By being improved, moisture penetrates deeper to a deeper depth, so that the strength of the agglomerated product to be produced can be further improved without increasing the amount of binder to be added. In addition to adding moisture at 60 ° C or higher and 90 ° C or lower in the granulation step, it is possible to further improve the strength of the agglomerated product produced by adding a binder to the mixture. It becomes.

[Flow of reduced iron production method according to this embodiment]
Below, an example of the flow of the manufacturing method of the reduced iron based on this embodiment based on the above knowledge is demonstrated in detail, referring FIG. FIG. 2 is a flowchart showing a flow of a method for producing reduced iron according to the present embodiment.

In the method for producing reduced iron according to the present embodiment, first, an iron oxide raw material selected from the group consisting of iron making dust and iron ore generated in the iron making process is mixed with the reducing material (step S101) and pulverized from the hopper 11. The machine 13 is charged. As the pulverized coal used as the reducing material, it is possible to use, for example, those having an 80% particle size of about 5 mm to 10 mm under a sieve and a water content of about 8 to 12%. Further, the blending ratio of the iron oxide raw material and the reducing material is adjusted in consideration of suitable conditions for obtaining good reduced iron in the reduction step described later. For example, it can be set to about 90:10. This mixture has a particle size of, for example, about 4 mm when charged into the pulverizer.

Subsequently, the mixture of the iron oxide raw material and the reducing material is pulverized by the pulverizer 13 until the particle size becomes, for example, 70 μm to 500 μm (80% particle size under sieve), preferably 150 μm to 300 μm. (Step S103). By setting the particle size of the mixture to 70 μm to 500 μm, it becomes possible to produce reduced iron with a high metallization rate with a small variation in metallization rate (for example, about 6% or less), and the lower limit of the particle size By setting it as 70 micrometers, it becomes possible to suppress the explosion of the agglomerate in the reduction process. Also, by setting the particle size of the mixture to 150 μm to 300 μm, it is possible to produce reduced iron with a high metallization rate with a very small variation in metallization rate (for example, about 3% or less). By setting the thickness to 150 μm, explosion of the agglomerated material in the reduction process can be avoided.

In the pulverization step (step S103), it is preferable to adjust the water content of the mixture made of the iron oxide raw material and the reducing material to about 1% to 3%. By setting it as this moisture content, it becomes possible to hold | maintain favorable kneadability in the kneading | mixing process mentioned later.

As the pulverizer for pulverizing the mixture, for example, a vibration mill such as a ball mill or a rod mill can be used. In order to keep the particle size of the mixture in the above range and the water content of the mixture to about 1% to 3% on the exit side of a vibration mill such as a ball mill, the processing speed of the ball mill used for pulverization is appropriately set. That's fine. For example, first, the pulverization ratio is calculated from the target value of the particle diameter on the exit side of the vibration mill (ball mill) and the particle diameter on the entry side of the vibration mill. Then, by using the calculated grinding ratio and the theoretical capacity curve of the vibration mill at the target value of the moisture content on the exit side of the vibration mill, as described in Patent Document 1, It is possible to determine the processing speed.

Further, in the method for producing reduced iron in the present embodiment, by drying the iron oxide raw material before mixing, the moisture content of the mixture at the time of charging the pulverizer is set to a value at which the vibration mill exhibits appropriate pulverizability. It becomes possible to hold, and it is not necessary to constantly change the control of the vibration mill during grinding. Moreover, even if the moisture content of the iron oxide raw material fluctuates due to various factors, the millability of the vibration mill is maintained at a suitable value by appropriately controlling the setting of the dryer 12 during drying before mixing. It becomes possible.

When the pulverization of the mixture is completed, the pulverized mixture is charged into a kneader 15 such as a mix muller so that the water content becomes a value appropriate for kneading (for example, about 6 to 9%). And then kneaded (step S105). Further, when kneading the mixture, a predetermined binder may be added to the mixture in order to improve the strength of the agglomerated product to be produced.

Here, as described above, in the method for producing reduced iron according to the present embodiment, moisture having a temperature of 60 ° C. or more and 90 ° C. or less is used in order to adjust the moisture content of the mixture. By utilizing such moisture, it becomes possible to improve the permeability of moisture to the mixture, and the diffusion efficiency of moisture into the mixture can be dramatically improved. As a result, it becomes possible to further homogenize the water present in the mixture and improve the granulation properties during granulation.

Moreover, in the manufacturing method of reduced iron which concerns on this embodiment, not only the improvement of granulation property but manufacturing is performed by using the water | moisture content of 60 degreeC or more and 90 degrees C or less for the humidification process for adjusting a moisture content rate. It is possible to dramatically improve the strength of the agglomerated product. Therefore, according to the manufacturing method of reduced iron which concerns on this embodiment, it becomes possible to aim at the reinforcement | strengthening of the agglomerated material manufactured, without increasing the quantity of the binder to add.

Any binder can be used as long as it is soluble in water at 60 ° C. or higher and 90 ° C. or lower as the binder used in the kneading step. Examples of such a binder include a liquid organic binder and a powder organic binder. Examples of liquid organic binders include molasses and lignin. Examples of the powdery organic binder include starch of grains such as rice, tapioca, rye and corn. Among these organic binders, when the necessary moisture and binder addition in the kneading step are added as a slurry, the addition is viscous and does not mix well in the kneading step. Therefore, the powder form is better than the liquid form. Since the organic system is vaporized during the reduction and contributes to the improvement of the reduction, it is particularly preferable to use a powdery organic binder.

By using a binder that is soluble in water at 60 ° C. or higher and 90 ° C. or lower, the solubility of the binder itself in water is improved, and as a result, the dispersion efficiency of the binder can be improved. As a result, the binder itself reaches the entire mixture, and the strength of the agglomerated product to be produced can be further improved.

Further, in addition to the organic binder, an inorganic binder such as cement, bentonite, fly ash and the like may be further added.

In addition, as the amount of the binder added to the mixture, it is possible to increase the strength of the agglomerated product to be produced, but from the viewpoint of production cost etc., the total mass of the mixture to be kneaded On the other hand, it is preferably 2% or less during drying.

When the kneading by the kneading machine 15 is completed, the mixture is charged and granulated in a molding machine 17 such as a pan pelletizer (dish type granulator), a double roll compressor (briquette making machine), an extrusion molding machine (step). S107), resulting in an agglomerated product.

The produced agglomerated material is dried by the dryer 19, and has a moisture content of 1% or less, for example (step S109). The agglomerated product after drying is charged into a reduction furnace 21 such as RHF and subjected to a reduction treatment. The agglomerated product according to the present embodiment exhibits not only good granulation properties but also good crushing strength by using moisture at 60 ° C. or higher and 90 ° C. or lower in the kneading step. Therefore, the agglomerate is hardly broken in the reduction furnace 21 even in the reduction step, and the agglomerate can be sufficiently reduced. For example, when using RHF as the reduction furnace 21, for example, the temperature in the reduction furnace 21 is set to about 1350 ° C., and the speed of the rotating bed is set so that the reduction process is completed in about 15 minutes. Is possible. By performing such a reduction treatment, it is possible to efficiently produce reduced iron that is difficult to break and has a high metalization rate.

As described above, according to the method for producing reduced iron according to the present embodiment, it is possible not only to improve the granulation property in the granulation step but also to prevent cracking and to achieve a high metallization rate. It is possible to produce reduced iron. Therefore, it is possible to improve the oxygen intensity of the reduced iron melting converter, and it is possible to maintain hot metal productivity at a high level.

Hereinafter, the method for producing reduced iron according to the present invention will be further described with reference to Examples and Comparative Examples. In addition, the Example shown below is an example of this invention to the last, Comprising: This invention is not necessarily limited only to the Example shown below.

In the examples and comparative examples described below, agglomerates were produced according to the procedure shown in FIG. In the pulverization step (step S103), a ball mill (diameter × length: 3.3 m × 6.0 m, input amount: 40 ton / h, motor capacity: 700 KW, ball: 49 ton) is used, and the kneading step (step S105). ) Used a mix muller. In the granulation step (Step S107), a double roll compressor was used, and in the drying step (Step S109), a band dryer was used.

In Examples and Comparative Examples described below, ironworks dust containing converter dust and blast furnace dust was used as an iron oxide raw material, and coal was used as a reducing material. Moreover, in the Example and comparative example demonstrated below, the iron oxide raw material and the reducing material were mixed so that it might become mass ratio of 87:13, and it was set as the mixture. The particle size of the mixture was 80 μm under sieve and 300 μm or less. In addition, in the water treatment in the kneading step, water was added so that the water content was 8.0%. In the following examples, the difference between the examples and the comparative examples is the temperature of moisture used in the kneading step.

[Moisture penetration time into the mixture]
First, with reference to FIG. 3, the change in the water penetration time into the mixture will be described.
The water permeation time into the mixture corresponds to a water content of 8% with respect to this mixture after collecting 20 g of the mixture before mixing and mixing the iron oxide raw material and the reducing material at the above-mentioned ratio. When moisture was added, the time until the added moisture completely penetrated into the mixture was measured. Here, the temperature of the moisture to be added is five types of 0 ° C., 15 ° C., 60 ° C., 80 ° C. and 90 ° C., and in FIG. Show.

As is apparent from FIG. 3, when water at 0 ° C. in ice water is added, the water penetration time into the mixture is increased compared to when water at 15 ° C. is added. Recognize. In addition, when water at 60 ° C., 80 ° C., and 90 ° C. was added, the time for water penetration into the mixture decreased compared to when water at 15 ° C. was added, and the higher the water temperature, It can be seen that the infiltration time decreases. As shown in FIG. 3, by adding water at 90 ° C. to the mixture, the water penetrates in 60% of the time compared to the case of adding water at 15 ° C., and the water penetration time into the mixture is 40%. % Can be seen. In this way, by adding moisture of 60 ° C. or higher and 90 ° C. or lower (in this example, moisture of 60 ° C., 80 ° C., and 90 ° C.) to the mixture, the time for water penetration into the mixture is significantly reduced. Is possible.

[Dama presence ratio]
Next, a change in the ratio of lumps present in the mixture after kneading (and before granulation) will be described with reference to FIG. In the following description, “dama” refers to a lump having a particle size of 5 mm or more remaining when the mixture is sieved. In the present example, a mixture after kneading (and before granulation) to which water at four temperatures of 15 ° C., 60 ° C., 80 ° C., and 90 ° C. was added was collected, and then sieved to obtain a particle of 5 mm or more. The total weight of lumps containing water having a diameter was measured. FIG. 4 shows a ratio based on the weight of the lump when water having a temperature of 15 ° C. is added in the kneading step.

As is apparent from FIG. 4, the use of moisture at temperatures of 60 ° C., 80 ° C., and 90 ° C. in the kneading process reduces the presence of lumps compared to when moisture at 15 ° C. is used. In addition, it can be seen that as the temperature of moisture increases, the degree of decrease in the presence of lumps increases. In addition, it can be seen that the use of moisture at a temperature of 90 ° C. in the kneading step reduces the amount of lumps to about 87% compared to when moisture at 15 ° C. is used. This result shows that by using moisture at 60 ° C. or more and 90 ° C. or less (in this example, moisture at 60 ° C., 80 ° C. and 90 ° C.), the moisture diffuses more uniformly into the mixture, and the moisture in the mixture It is shown that the homogenization of the material is realized and the granulation property is improved.

[Corn starch dissolution rate]
Next, in this example, with respect to corn starch used as an organic binder, it was actually measured how the rate of dissolution in water changes due to changes in the temperature of water. In this measurement, 5.0 g of corn starch was added to 500 mL of moisture (water temperature was 4 types of 20 ° C., 60 ° C., 80 ° C., and 90 ° C.), and the dissolved mass (g) remaining undissolved was measured. Thus, the dissolution rate was calculated.

The obtained results are shown in FIG. As is clear from FIG. 5, the ratio of corn starch dissolved in water having a water temperature of 20 ° C. was 40%, whereas the ratio of dissolution in water having a water temperature of 60 ° C. was about The dissolution rate was about 70% with respect to moisture having a water temperature of 80 ° C., and the dissolution rate was about 96% with respect to moisture having a water temperature of 90 ° C.

This result shows that the solubility of the binder itself in the water is improved by setting the temperature of the water added in the kneading step to 60 ° C. or more and 90 ° C. or less, and the binder is dissolved in the water. This shows that the dispersion efficiency of the binder is improved.

[Changes in strength of agglomerates]
Next, the crushing strength after drying was measured for a plurality of types of agglomerates produced according to the above-described process. The crushing strength was measured according to the crushing strength measuring method among the strength measuring methods specified in JIS Z-8841.

In addition, the agglomerate which measured crushing strength is the agglomerate manufactured by adding the water of the temperature of 15 degreeC, 60 degreeC, 80 degreeC, 90 degreeC, 120 degreeC, 160 degreeC, and 200 degreeC, respectively, and the said There are a total of 14 types of agglomerates prepared by further adding (externally adding) 1% corn starch to the mixture and adding moisture at the above temperature. In addition to these examples, an agglomerated product produced by adding moisture at 90 ° C. to a mixture in which the amount of binder added is reduced by 13%, and a mixture in which the amount of binder added is reduced by 21%. The crushing strength of the agglomerate produced by adding water at 90 ° C. was measured in the same manner. The agglomerated material produced has an elliptical shape with a major axis of 20 to 30 mm.

The obtained results are shown in FIG. In addition, in FIG. 6, the relative intensity | strength which set the crushing intensity | strength of the agglomerate at the time of adding a 15 degreeC water | moisture content with respect to the mixture in which the binder is not added to 1 is shown.

As is clear from FIG. 6, the crushing strength is remarkably improved when the temperature of the added water is 60 ° C. or more both in the case where the binder is not added and in the case where the binder is added. I understand that. Thus, it can be seen that by adding moisture at 60 ° C. or higher in the kneading step, it is possible to improve not only the granulation property in the granulation step but also the strength of the agglomerated product to be produced. . In addition, when the temperature of the added water is 90 ° C. to 200 ° C. in both the case where the binder is not added and the case where the binder is added, the crushing strength has a substantially constant value. I understand. The upper limit of the temperature of the water added to the mixture is determined by the kneading step and the heat resistance temperature of the equipment used in each step performed after the kneading step, the equipment restrictions of the steam supply equipment, etc., and the dissolution ratio in water in FIG. Since the temperature of water at 90 ° C. reaches nearly 100%, the temperature of water for improving the strength of the agglomerated product to be produced is optimally 60 ° C. or higher and 90 ° C. or lower.

Next, attention is focused on the strength when water at 15 ° C. is added to the mixture to which the binder is added, and the strength when water at 90 ° C. is added to the mixture with the added amount of the binder reduced. As is clear from FIG. 6, between the agglomerates to which the same 90 ° C. moisture was added, a reduction in the crushing strength was observed by reducing the amount of binder added. However, the crushing strength of the agglomerated material in which the amount of binder added is reduced by 13% and water at 90 ° C. is added is the same value as the crushing strength when water at 80 ° C. is added to the mixture containing the binder. The crushing strength of the agglomerated product in which the amount of binder added was reduced by 21% and water at 90 ° C. was added was the crushing strength when water at 15 ° C. was added to the mixture containing the binder. It can be seen that they have similar values. This result indicates that the amount of binder added can be controlled by adding water at 60 ° C. or higher and 90 ° C. or lower to the mixture, and the method for producing reduced iron according to the present embodiment is used. This suggests that it is possible to expand the range of operations for producing reduced iron.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to only such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

According to the method for producing reduced iron of the present invention, it is possible to further improve the granulation property when agglomerating a mixture as a raw material of reduced iron.

DESCRIPTION OF SYMBOLS 11 Hopper 12 Dryer 13 Crusher 15 Kneading machine 17 Molding machine 19 Dryer 21 Reduction furnace 23 Melting furnace

Claims

A kneading step of adding and kneading water at 60 ° C. or higher and 90 ° C. or lower to a mixture containing an iron oxide raw material and a reducing material both in powder form;
A granulation step of agglomerating the mixture after the kneading step into an agglomerated product;
A reduction step of reducing the agglomerated product after the granulation step to produce reduced iron;
A method for producing reduced iron, comprising:
The method for producing reduced iron according to claim 1, wherein in the kneading step, a binder soluble in moisture is further added to the mixture.
3. The method for producing reduced iron according to claim 2, wherein the binder is a liquid organic binder or a powder organic binder.
The method for producing reduced iron according to claim 3, wherein the binder is the powdery organic binder, and is a starch of grains selected from the group consisting of rice, tapioca, rye and corn. .
The method for producing reduced iron according to claim 1, wherein in the kneading step, the water content of the mixture is adjusted to 6% to 9% by the addition of the water.
2. The method for producing reduced iron according to claim 1, wherein the particle size of the mixture before kneading in the kneading step is 70 μm to 500 μm with an 80% particle size under sieve.
The method for producing reduced iron according to claim 1, wherein the water content of the mixture before the water is added in the kneading step is 1% to 3%.