JP5334240B2 - Method for producing reduced iron agglomerates for steelmaking - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a reduced iron agglomerate for steel-making, in which high zinc powdery iron based dust and sludge are subjected to reduction roasting treatment, and are thereafter agglomerated. <P>SOLUTION: Disclosed is the method for producing the reduced iron agglomerate for steel-making, where a carbonaceous material is mixed into powdery iron based dust and sludge containing a zinc component of 1.0 to 10 mass% as the average composition, the mixture is subjected to reduction roasting treatment, so as to produce reduced iron, and the obtained powdery reduced iron is cooled and is thereafter agglomerated by a briquette molding machine. In the production method, it is preferable that the reduced iron after the cooling is classified by sieve treatment, a material through a sieve is agglomerated by the briquette molding machine, further, the reduced iron after the agglomeration is circulated before the sieve treatment, and the material through the sieve is fed to the briquette molding machine once more. Further, it is preferable that a rotary kiln is used as a device for the reduction roasting treatment, and a double roll compression molding machine is used as the briquette molding machine. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for producing reduced iron agglomerates for steelmaking from iron-based dust and sludge having a high zinc component content generated in an integrated steelworks, and more specifically, granular iron having a high zinc component content. The present invention relates to a method for producing reduced iron agglomerates for steel making, in which carbonaceous materials are blended with system dust and sludge, reduced roasted to produce reduced iron, and agglomerated.

  In the integrated steelworks, various dusts and sludges (hereinafter referred to as “dusts”) containing granular iron in each production process are by-produced. In order to effectively use resources, dusts are used as raw materials for a sintering process for producing raw materials for blast furnaces. However, when dusts having a zinc (Zn) component of 0.1% by mass or more are used as sintering raw materials, the zinc ore is also contained in the sintered ore that is the product, and the formation of furnace wall deposits in the blast furnace The blast furnace operation will be adversely affected, such as damage to the furnace wall refractories.

  Therefore, in order to avoid the occurrence of problems in blast furnace operation, the dust containing zinc components is subjected to dezincing treatment by reduction roasting as disclosed in Non-Patent Document 1, for example. In the reduction roasting process, dust and charcoal are charged into a high-temperature furnace at 1000 ° C. or more, and air is blown into the furnace from one end of the furnace to burn the charcoal, and the other end of the furnace Is carried out by a method for discharging the combustion exhaust gas and the fine powder containing ZnO. As disclosed in Non-Patent Document 1, for the roasting process, a method using a rotary kiln in which a cylindrical drum-shaped furnace body rotates is common, but a rotary in which a disk-shaped hearth rotates in a horizontal plane. A hearth furnace is also used.

  A method for treating dust will be described below using a typical rotary kiln as an example.

  FIG. 1 is a diagram showing a process flow of a conventional dust processing method. As shown in the figure, the granular dusts 1 and the coke or anthracite 2 which are carbon materials are conveyed by a belt conveyor 3 and mixed by a mixer 4. Then, the mixed raw material is charged into the furnace from one end 6 of the rotary kiln 5 that performs rotational movement. On the other hand, an in-kiln supply gas (mainly air) 15 is supplied from the other end 7 of the furnace, and the CO gas generated from the in-furnace raw material is combusted to raise the in-furnace temperature.

In this rotary kiln, the raw material 30 moves from one end 6 of the furnace to the other end 7 while performing a rolling motion in a rotating cylindrical furnace having a slightly inclined gradient, and reduced iron 31 from the other end 7. As discharged. On the other hand, the kiln furnace gas 151 flows from the other end 7 toward the one end 6 in the direction opposite to the raw material, and is discharged from one end 6 as the kiln exhaust gas 16. Here, although not clearly shown, not only air but also some fuel gas such as coke oven gas is supplied as appropriate from the other end 7 not only for air but also for thermal compensation. Sometimes. During this time, the inside of the rotary kiln furnace is maintained in a reducing atmosphere by CO, CO _{2 and the} like generated by the combustion of the carbonaceous material, and the furnace temperature reaches a maximum of about 1250 ° C.

In such a high temperature and reducing atmosphere, Zn (gas phase) is thermodynamically more stable than ZnO (solid phase), so dezincification by volatilization of zinc in dusts. Processing is possible. Further, since the Fe component is more stable in Fe (solid phase) than Fe ₂ O ₃ (solid phase), Fe ₃ O ₄ (solid phase), and FeO (solid phase), the raw material is oxidized. It is reduced from iron to reduced iron containing metallic iron. That is, the reduction roasting process proceeds in the rotary kiln furnace, the zinc component is volatilized and removed from the dusts, and reduced iron containing 40% by mass or more of metallic iron is manufactured. The reduced iron produced as described above is cooled by the cooling device 8 and then classified by the vibration sieving device 9, and the sieved product 10 is blast furnace together with the sintered ore 13 which is another blast furnace charge. 14 is charged. On the other hand, the sieving product 11 is sent to the sintering machine 12 together with other iron ore raw materials and used as a sintering raw material.

  However, reduced iron containing a large amount of metallic iron is used as a raw material for blast furnaces for the purpose of reduction and melting for producing metallic iron and for agglomerating raw materials for charging and using the blast furnace. Is extremely wasteful in terms of heat energy required for the processing. If it becomes possible to use reduced iron containing metallic iron as a raw material for a steelmaking furnace for producing steel from metallic iron, that is, a converter or an electric furnace, in terms of thermal energy, Can be expected. The present applicant, in Patent Document 1, discloses a steelmaking method in which reduced iron obtained by heating and reducing iron-containing dust together with a carbon-containing material is recovered as molten iron in hot metal by charging it into a hot metal dephosphorization furnace. Proposed.

  Thus, in order to utilize reduced iron in the steelmaking process, it is extremely important to sufficiently remove moisture, powder, zinc components, etc. in raw materials which are not preferable in a steelmaking furnace, particularly a converter or an electric furnace, It is necessary to construct an efficient system to achieve this.

  In the operation of a steelmaking furnace, the entire amount of zinc component is volatilized and dissipated as gaseous zinc, so the zinc component of reduced iron used as a steelmaking raw material is limited to 1.0% by mass or less.

  On the other hand, as exemplified in the above-mentioned Patent Document 1, in the conventional reduction roasting treatment of dusts, in order to agglomerate the reduced iron obtained as a product, at the stage of raw material dusts, using a dish granulator A spherical green ball is used, or a briquette is formed by a compression molding apparatus, and then a reduction roasting process is performed. However, when this method is applied to a process of dezincing using dusts having a high zinc component content (hereinafter also referred to as “high zinc dusts”) as a raw material, it is agglomerated in the previous stage of the reduction roasting treatment. Therefore, the contact between the reducing gas and the solid becomes insufficient in the reduction roasting furnace. Even if the contact between the reducing gas and the solid is insufficient, there is no obstacle in the production of metallic iron, but the efficiency of dezincing by reducing and volatilizing zinc decreases, and the content of zinc component in the reduced iron is reduced. The problem of becoming higher occurs.

  For this reason, when agglomeration of reduced iron that has been reduced and volatilized by zinc is necessary, a method of agglomerating after reducing iron is formed without agglomeration in the previous stage of the reduction roasting process. Is preferred. That is, it is effective to reduce and roast powdery dusts in the form of powder to produce reduced iron, and then agglomerate the obtained powdered reduced iron.

  Generally, hot briquetting using a double roll type compression molding machine is adopted as the agglomeration treatment of the granular reduced iron. Although hot briquetting has few restrictions on the molding process itself, it requires a combination of molding equipment and cooling equipment, and has the disadvantages that a huge equipment installation space is required and equipment costs are significantly increased. On the other hand, in the system in which reduced iron is molded after cooling, there is a problem that briquette cannot be molded well if the raw material has too much fine powder, and conversely if briquette exists, briquetting itself becomes impossible.

  In Patent Document 2, after reducing the reduced iron, an inert gas is blown so that the crushed surface is not oxidized, and pulverization and molding are performed in a non-oxidizing atmosphere, so that a metal melt is used without using a binder. A method for obtaining a non-ignitable briquette by using an adhesion action is disclosed. However, the technique disclosed herein is a method of briquetting by crushing all the bulk materials such as granular reduced iron (25 mm or less) and reduced pellets (16 mm or less) having a larger particle size than the object of the present invention. Nothing is shown about the particle size composition of the raw material at the time of molding.

JP 2007-302960 A (claims and paragraphs [0015] to [0022]) Japanese Patent Publication No. 1-22231 (Claims, first column, lines 10 to 20 and second column, lines 3 to 3, column 1) Dongfeng Heigen, Yoichi Aminaga, Yoshizumi Kawaguchi, Masanori Hatakeyama, Kiyoji Miyamoto: CAMP-ISIJ, Vol. 10 (1997) 36-39

  In briquetting powdered reduced iron after cooling, the properties and particle size composition of the reduced iron are important factors that determine whether or not briquetting can be performed. With conventional agglomeration techniques, the appropriate conditions for agglomerating granular reduced iron produced from dusts with a high zinc content are not clear, and it has been difficult to produce reduced iron agglomerates for steelmaking. It was.

  The present invention has been made in view of the above problems, and its problem is to produce reduced iron by subjecting high-zinc granular iron-based dust and sludge to reduction roasting, and agglomerate the steel. It is providing the manufacturing method of the reduced iron agglomerated mineral.

  In order to solve the above-mentioned problems, the present inventors, based on the conventional problems, agglomerate after reducing high-zinc granular iron-based dusts to reduce iron by reducing roasting treatment. The production method of reduced iron agglomerate for steelmaking was studied, and the present invention was completed by obtaining the following findings (a) to (d).

  (A) When the zinc component content in the reduced iron agglomerate (reduced iron briquette) charged into the steelmaking furnace exceeds 1.0 mass%, an operational problem occurs in the steelmaking furnace. The average zinc component content of the dusts used as the raw material for the reduced iron agglomerate needs to be 10% by mass or less. Moreover, it is not necessary to perform a dezincing process about the raw material whose average zinc component content rate is less than 1.0 mass%.

  (B) The dezincification reaction of zinc in dusts is mainly a reaction according to the following formula (1). To promote the reaction, it is necessary to secure a sufficient contact area between CO (gas) and ZnO (solid). is there.

ZnO (solid) + CO (gas) → Zn (gas) + CO ₂ (gas) (1)
For the above reasons, when the raw material is an agglomerated material, the zinc present in the material is difficult to be volatilized and removed. Therefore, a method of agglomerating the obtained reduced iron with a briquette molding machine is suitable for reduction roasting using powdered dust that can ensure a large contact area with CO (gas). is there.

  (C) In the reduction roasting treatment of (b) above, it may be in a state of being finely divided without being agglomerated at a position in the furnace at 1000 ° C. or higher where dezincification occurs. From this point of view, it is preferable to use a rotary kiln that rotates a cylindrical furnace and stirs the raw material rather than a rotary hearth furnace in which the raw material is placed on the hearth.

  (D) The briquetted reduced iron agglomerated mineral is formed by molding powdered reduced iron. For example, after forming into a plate shape, crushing to form the agglomerated mineral If a system for subsequent crushing is employed, crushed powder is newly generated. Therefore, for briquetting, it is preferable to use a double roll briquette molding machine having pockets (holes) on the outer peripheral surface of the roll, and compression molding.

This invention is completed based on said knowledge, The summary exists in the manufacturing method of the reduced iron agglomeration for steel manufacture shown to following (1)-( 4 ).

(1) Carbon steel is mixed with granular iron-based dust and sludge containing 1.0 to 10% by mass of a zinc component with an average composition, and then reduced roasting is performed to produce reduced iron. A method for producing reduced iron agglomerate for steel making, characterized in that the reduced iron is cooled and classified by sieving , and the sieved material is agglomerated by a briquette molding machine.

( 2 ) The reduced iron after agglomeration by the briquette molding machine is circulated before the sieving process, and the sieved product is reduced to a reduced iron agglomerated mineral product. The method for producing a reduced iron agglomerated ore for steelmaking as described in ( 1 ) above, characterized in that it is supplied.

( 3 ) The method for producing a reduced iron agglomerate for steelmaking according to (1) or ( 2 ), wherein a rotary kiln is used as the reduction roasting apparatus.

( 4 ) The method for producing reduced iron agglomerates for steel making according to (1) to ( 3 ), wherein a double roll type compression molding machine is used as the briquette molding machine.

  In the present invention, the “zinc component” means zinc contained in the form of metal or compound in dusts.

  “Powder and granular” means powders, granules or a mixed state thereof having a particle size of 5 mm or less.

  “Iron-based dust” means dust having an iron content of 20% by mass or more, such as metallic iron and iron oxide.

  “Reduction roasting treatment” refers to heating the object to be processed, such as ore and dust, to a temperature below the melting point, causing the object to be processed and reducing gas, carbon, etc. to interact with each other to cause a reduction reaction. It means the process of reducing the processed product.

  “Agglomeration” means agglomeration of fine ore and dust for the purpose of particle size adjustment and quality improvement.

  In the following description, “mass%” representing the zinc component content and the like is also simply referred to as “%”.

According to the method of the present invention, after mixing the carbonaceous material in particulate ferrous dust and sludge high zinc, performing reduction roast process to produce reduced iron, and classified by sieving after this cooling, Since the sieved material is agglomerated by a briquette molding machine, a high-quality reduced iron agglomerate for steelmaking can be produced. Therefore, the method of the present invention is useful as a method for producing reduced iron agglomerates for steelmaking from which undesirable zinc components are sufficiently removed as components in the iron source material supplied to steelmaking furnaces such as converters and electric furnaces. This technology can make a significant contribution in the field of materials and steelmaking.

As described above, in the method of the present invention, after mixing a carbonaceous material with granular iron-based dust and sludge containing 1.0 to 10% by mass of a zinc component with an average composition, reduction roasting is performed to reduce the reduced iron. This is a method for producing reduced iron agglomerates for steelmaking, in which the powdered reduced iron is cooled and classified by sieving, and the under-sieved material is agglomerated by a briquette molding machine. Hereinafter, the method of the present invention will be described in more detail, including the reasons for defining the method as described above and preferred embodiments.

1. Basic Configuration of the Present Invention FIG. 2 shows a process flow of a method for producing a reduced iron agglomerate for steelmaking according to the present invention. The process flow shown in the figure is a process flow according to a reference example of the present invention. As shown in the figure, the granular dusts 1 and the carbonaceous material 2 are conveyed by a belt conveyor 3 and mixed by a mixer 4, and then rotated from one end 6 of a rotary kiln 5 that performs rotational movement. Is charged. The kiln supply gas 15 is supplied from the other end 7 of the furnace, and the CO gas generated from the furnace raw material is combusted to raise the furnace temperature.

In the above rotary kiln, the raw material 30 moves from one end 6 of the furnace to the other end 7 while performing a rolling motion in a rotating cylindrical furnace having a slightly inclined gradient, and reduced iron from the other end 7. It is discharged as 31. On the other hand, the kiln furnace gas 151 flows from the other end 7 toward the one end 6 in the direction opposite to the raw material, and is discharged from one end 6 as the kiln exhaust gas 16. During this time, the inside of the rotary kiln furnace is maintained in a reducing atmosphere by CO, CO _{2 and the} like generated by the combustion of the carbonaceous material, and the reduction roasting reaction of the raw material proceeds. The reduced iron produced in this way is cooled by the cooling device 8 and then compression-molded by the briquette molding machine 17 to form reduced iron briquette 19 which is charged and used in the steel making furnace 20.

  In the steelmaking furnace 20, a raw material is heated to a high temperature state in a reaction vessel (reaction furnace) whose upper part is opened, and a refining operation is performed by melting iron. Therefore, a large amount of dust is volatilized and dissipated from the opening at the top of the furnace, and if this amount becomes excessively large, the refining operation cannot be performed. Therefore, the steelmaking raw material is required to have a low volatility dissipation property. 1stly, the inside of a steelmaking furnace is in a high temperature state, and the powder which exists in a use raw material is easy to volatilize and dissipate without melt | dissolving in molten steel. For this reason, powdery raw materials cannot be brought into the steelmaking furnace. Second, if water is present in the raw material, powder is generated by steam explosion and is volatilized and dissipated as described above. Therefore, it is preferable that the water | moisture content in a raw material shall be 4 mass% or less. Thirdly, in a high temperature state where molten steel is present, the zinc component is reduced and volatilized, causing trouble in the refining operation, so that the amount of the zinc component in the raw material brought into the furnace is limited.

2. Zinc Content in Dusts The method of the present invention is a method for producing reduced iron agglomerates using high zinc dusts generated at ironworks as a raw material, instead of using high-purity iron ore as a raw material. Therefore, management of the zinc component content in the raw material is extremely important in defining the components of the product reduced iron. In a steelmaking furnace, if the zinc content in the reduced iron briquette is higher than 1.0% by mass, problems in refining operations often occur. Since the dezincification rate in the reduction roasting can ensure at least 90% or more, in order to reduce the zinc component content of the reduced iron product to 1.0% by mass or less, dust as a raw material for the reduction roasting It is sufficient if the average zinc component content of the product is 10% by mass or less.

  On the other hand, it is not necessary to perform a dezincing process for a raw material having a zinc component content of 1.0 mass% or less. Since the raw materials for reduction roasting are mixed and processed, the zinc content of each brand is not particularly specified, but as the average composition of the charged raw materials, the zinc content is in the range of 1.0 to 10% by mass. Must be within.

3. Raw material form suitable for dezincification and roasting furnace The influence of the raw material form on the dezincification by the reduction roasting process, that is, the granular state or the agglomerated state will be described. Unlike the conventional direct iron manufacturing method in which reduced iron is produced using high-purity iron ore as a raw material, the method of the present invention does not subject the raw material to a special agglomeration treatment in advance, and remains in a granular state without reducing roasting. It is important to bake. The reason will be described below.

  FIG. 3 is a diagram showing the relationship between the particle diameter of the feedstock and the dezincification rate in the reduction roasting test. The result of the figure is that the raw material was green-balled using a dish-type granulator in the laboratory, and the resulting green ball was subjected to reduction roasting treatment at 1200 ° C. under air flow to form a green ball. This is a comparative investigation of the difference in the influence on the dezincification rate between the raw material and the granular raw material. The coal content in the green ball was 20%.

  The broken line in the figure shows the dezincification rate when using a powdery raw material, and the solid line shows the dezincification rate when using a green balled raw material. From the results shown in the figure, when a powdery raw material is used, a high dezincification rate of 98% is obtained, whereas when a green ball raw material is used, the dezincification rate is low, Moreover, it has been found that the dezincification rate decreases as the particle size of the green ball increases.

  As described above, the reason why the behavior of the dezincification rate of dust zinc differs depending on the form of the raw material dust is as follows. That is, the dezincification reaction of zinc in dusts is mainly represented by the following formula (1).

ZnO (solid) + CO (gas) → Zn (gas) + CO ₂ (gas) (1)

  In order to promote the reaction of the above formula (1), it is necessary to secure a sufficient contact area between CO (gas) and ZnO (solid), that is, to secure a reaction interface area. Therefore, when the raw material dusts are agglomerates, the reaction interfacial area is small, and the zinc component existing on the particle surface is easily reduced and volatilized, but the zinc component existing inside the particle is difficult to be volatilized and removed. . As a result, in the case of an agglomerate, the dezincification rate decreases. Here, the agglomerate means a strongly agglomerated material, and does not mean a pseudo agglomerated material that collapses in the reduction roasting process. In order to promote the reduction roasting reaction, it is important that the dezincification reaction by the reduction roasting occurs at a temperature of 1000 ° C. or higher, and is in a finely divided state without being agglomerated.

  For this reason, reduction roasting uses a granular dust that can ensure a large contact area with CO gas, and a method of agglomerating the obtained reduced iron with a briquette molding machine. Is appropriate.

From the above viewpoint, it is preferable to use a rotary kiln as the reduction roasting furnace. The reason is that a rotary kiln having a structure in which raw material dust is agitated while rotating a cylinder can mitigate pseudo-particle formation of the raw material, compared to a rotary hearth furnace having a structure in which the raw material is placed on the hearth. Because. In addition, since the raw material can be agitated, it is possible to secure a good contact state between the gas and the raw material particles and further improve the efficiency of the dezincification reaction (the invention according to claim 3 ). ).

4). Reduced iron cooling Reduced roasted reduced iron is discharged in the form of powder in a red hot state, but when cooled in an air atmosphere, Fe in the reduced iron may be reoxidized to FeO. There is. Therefore, in order to prevent this reoxidation, rapid cooling is performed by water cooling, indirect water cooling (cooling the outside of the apparatus by water) and direct air cooling, or cooling in a nitrogen gas atmosphere.

High zinc dusts generated in steelworks differ from high-purity iron ore and contain slag components (SiO ₂ , Al ₂ O ₃ , CaO, etc.) in addition to iron and zinc components. When the reduced iron in a red hot state is cooled with water, it contains a large amount of water. As a result, when the reduced iron after the water-cooling treatment is sieve-classified, it takes a long time for the surface of the reduced iron particles to dry, and during this time, the reduced iron is reoxidized by the oxidation catalytic action of the contained water. The problem occurs. Therefore, the reduced iron is preferably cooled by a combination of indirect water cooling (cooling the outside of the apparatus with water) and direct air cooling, or in a nitrogen gas atmosphere.

5. Agglomeration and sieving of reduced iron The powdered reduced iron thus cooled is agglomerated by a briquette molding method. When compacting a powdered material, a binder is usually added, but metallic iron is highly ductile, and the content of metal iron (mass%) / total iron content (mass%) x Briquetting is possible if the metallization rate represented by 100 (%) is 40% or more. However, briquetted reduced iron agglomerates are formed by molding powdered reduced iron. For example, after forming into a plate shape, crushing to form an agglomerated plate shape. If a system for crushing the molded product is adopted, crushed powder is newly generated. For these reasons, it is preferable to use a double roll briquette molding machine having pockets (holes) on the outer peripheral surface of the molding roll for the briquette molding, and compression molding is performed (invention according to claim 4 ).

  In the case of manufacturing briquettes with a double roll briquette molding machine, it is determined whether or not moldability is possible depending on how well the raw material can be supplied to a portion that becomes a compression contact of the double roll. The powdery raw material is supplied like a continuous fluid by the action of gravity, but when there are coarse particles with a particle diameter of 5 mm or more, or when the particle diameter is composed only of powder with a particle diameter of 1 mm or less, The powdery raw material does not flow smoothly like a continuous fluid, and the briquette cannot be manufactured stably.

  In the reduced iron after the reduction roasting treatment according to the method of the present invention, particles having a particle size of 1 mm or less are present in an amount of about 24% by mass, and coarse particles having a particle size of 5 mm or more are also present in an amount of about 31% by mass. If coarse particles having a particle size of 5 mm or more are present, the briquette molding is adversely affected. Therefore, it is preferable to remove such coarse particles in advance by sieving.

  FIG. 4 is a diagram showing a process flow in which reduced iron is sieved before the agglomeration process in the method for producing reduced iron agglomerate for steelmaking according to the present invention.

The reduced iron 31 cooled by the cooling device 8 is subjected to a sieving process (classification process) by the vibration sieving device 9, and the sieved product is compression-molded and agglomerated by the briquette molding machine 17 to become a molded product 18. The molded product 18 is charged into the steelmaking furnace 20 as reduced iron briquette 19 through a route indicated by reference numeral A in the drawing (invention according to claim 1 ).

In addition to briquettes, powder such as burrs (joint fragments between briquette particles) is generated and mixed in the briquetted molding 18. Therefore, in order to remove this powder, it is preferable to classify again with a vibrating sieve device to separate the reduced iron powder of the under sieve and the reduced iron briquette (reduced iron agglomerate) 19 of the above sieve. In this case, two vibration sieving devices are required before and after the briquette molding machine 17, and a mixture of reduced iron briquettes discharged from the briquette molding machine 17 and mixed powders such as burrs is shown in FIG. By circulating in front of the vibration sieve device 9 through the route indicated by the symbol B, one vibration sieve device can be omitted, and a more compact agglomeration facility can be achieved (according to claim 2 ). invention).

  In order to confirm the effect of the method for producing reduced iron agglomerated minerals according to the present invention, the following tests were conducted and the results were evaluated.

1. Example 1
Based on the process flow of the method for producing reduced iron agglomeration for steel making shown in FIG. 2 and another process flow in which reduced iron is sieved before the agglomeration treatment as shown in FIG. An ore production test was conducted.

1-1. Production test of reduced iron Table 1 shows the properties and blending ratios of dusts and carbonaceous materials as raw materials.

  Dusts include many types such as those whose zinc component content exceeds 10% by mass, and they are supplied separately, but in the compounded state after being mixed by a mixer, the zinc component content The rate was about 6% by mass. Here, various and small amounts of sludge are present in the raw material, but these are raw materials that are generally not counted in detail, and are therefore described as incinerated iron dust. Powder carbon coke was used as the carbon material, and the C component content in the blended state was about 18% by mass.

  Table 2 shows the particle size distribution after the drying treatment in the blended state of the raw materials.

  The moisture content of the raw material in the blended state is about 19% by mass, and apparently pseudo particles are formed, but the pseudo particles are easily disintegrated by the drying treatment, so that most of them have a particle size of 5 mm or less. A rotary kiln was used for the reduction roasting treatment of the raw material after blending. Table 3 shows the main equipment specifications and operating conditions of the rotary kiln.

  In the same table, the amount of gas used by the fuel burner (not shown in FIG. 2) is the amount of fuel used from the air inlet (the other end) 7 of the rotary kiln to control the amount of thermal compensation in the rotary kiln furnace. The supply amount of coke oven gas supplied as gas is shown. The amount of raw material supplied is 25 dry-t / h, and the amount of reduced iron discharged is 17.5 dry-t / h. About 30% by mass of oxygen, C component, zinc component, etc. as iron oxide in the raw material Has been removed. As a result of the reduction roasting, the dezincification rate was 98.8% by mass, and the metallization rate of the reduced iron was 73.6% by mass.

  Table 4 shows the component composition of reduced iron discharged from the rotary kiln.

  The zinc component in the reduced iron is 0.1% by mass, and considering the high metallization rate, a component composition sufficiently satisfactory as a steelmaking raw material has been obtained.

1-2. Reduced iron agglomeration test Next, reduced iron that has been reduced and roasted by a rotary kiln is collected, cooled, and then tested to produce reduced iron briquettes using a double-roll briquette molding machine. The yield of agglomerates and the strength of reduced iron agglomerates were compared and evaluated. This test is a test according to a reference example of the present invention.

  FIG. 5 schematically shows the used double roll briquette molding machine. The double roll briquette molding machine has a structure in which two cylindrical molding rolls 171 are disposed horizontally adjacent to each other. Of the forming rolls 171, the left forming roll in the figure rotates clockwise, and the right forming roll rotates counterclockwise, and there are many holes called pockets 172 on the outer peripheral surfaces of both rolls. The pocket 172 is arranged so as to synchronize on the circumferential surface between both rolls. A raw material supply hopper is installed above a portion where both molding rolls 171 are adjacent to each other, and reduced iron 31 as a briquette raw material is supplied from the hopper. The reduced iron 31 is bitten from the upper side to the lower side by the rotation of the molding roll at the adjacent portion of the molding roll 171, is compression-molded in the pocket 172, and is reduced downward from the adjacent portion of the molding roll 171. It is sent out as an iron molding 18.

  The outer peripheral surfaces of the molding rolls 171 of both the molding machines are not strictly in contact with each other, and a gap of about 2 mm exists. The reduced iron as a raw material enters the gap and the pocket 172 and receives a compressive force from both molding rolls 171 to produce a briquette having a shape in which the pocket and the gap are combined. Table 5 summarizes the specifications and test conditions of the double roll briquette molding tester.

  In the test, the supply amount of reduced iron as a raw material, the roll gap distance, and the roll rotation speed were changed. FIG. 6 shows the influence of the roll gap distance and the roll rotation speed on the roll compression pressure in a briquette molding test using a double roll briquette molding machine. The relationship in the figure is a test result when the supply amount of reduced iron is 0.6 to 1.4 t / h. Here, as the roll compression pressure, a value obtained by dividing the compression force by the roll by the roll width was adopted.

Each operation amount is closely related to each other, and it is recognized that the roll compression pressure tends to decrease as the roll rotation speed increases and the roll gap increases. When producing reduced iron briquettes using dust as a raw material, the reduced iron briquettes are formed by molding at a compression pressure of about 1.96 × 10 ^{6 to} 5.88 × 10 ⁶ N / m (2 to ⁶ tf / cm). It has been found that it can be manufactured. Table 6 shows the results of the agglomeration test under the conditions where the roll rotation speed is 7 rpm and the roll gap distance is 2.6 mm.

  In the same table, the agglomerate yield was determined by classifying the reduced iron briquette-molded with a 5 mm sieve and using the following equation (2).

  Agglomerate yield = (Product amount on sieve (kg) / Supply amount to sieve (kg)) × 100 (%) (2)

  As shown in the upper part of the same table, the agglomerate yield of reduced iron was confirmed to have a high yield exceeding 80% by mass.

  Furthermore, the briquette-molded product of reduced iron was subjected to sieving classification with a 5 mm sieve, and the conveyance strength of the product on the sieve was investigated. As the transport strength of the reduced iron agglomerates, a test based on the drop strength test method defined in JIS M8711 (2000) used for the evaluation of iron ores, which are raw materials for blast furnaces, is performed, and the particle size is 5 mm. An index (+5 mm%) representing the mass ratio of the above particles was used. Table 6 also shows the drop strength index. The drop strength index showed a value close to 70%, and it was confirmed that the drop strength index had a sufficiently high strength.

2. Example 2
Further, a molding test was conducted in the case where the 5 mm sieved product of reduced iron after water cooling (dried after water cooling) and the 5 mm sieved product of reduced iron briquette (molded product) 18 were mixed. This test is a test for evaluating the moldability in the process of returning the reduced iron briquette (molded product) 18 to the front of the vibration sieve device 9 through the route indicated by B in FIG.

  The test uses a mixture of 80% by mass of reduced iron 5 mm under sieve listed in Table 2 above and 20% by mass of under sieve obtained by classifying reduced iron briquettes obtained by briquette molding test with a 5 mm sieve. I went there. The test results are also shown in the lower part of Table 6. It was confirmed that both the agglomerate yield and the drop strength were improved by mixing the reduced iron briquette with a 5 mm sieve. This is presumed to be due to the fact that there are few powders having a particle diameter of 1 mm or less in the sieved product of reduced iron briquettes.

According to the method of the present invention, after mixing carbonaceous material with high zinc granular iron-based dust and sludge, reduction roasting treatment is performed to produce reduced iron, which is cooled and then classified by sieving, Since the lower article is agglomerated by a briquette molding machine, a high-quality reduced iron agglomerate for steelmaking can be produced. Therefore, the method of the present invention is a method for producing a reduced iron agglomerate for steelmaking in which an undesirable zinc component is sufficiently removed as a component in an iron source material supplied to a steelmaking furnace such as a converter or an electric furnace. It is a technology with high practical value that can be widely applied in both fields of steel and steelmaking.

It is a figure which shows the process flow of the processing method of the conventional dusts. It is a figure which shows the process flow of the manufacturing method of the reduced iron agglomerate for steel manufacture which concerns on this invention. It is a figure which shows the relationship between the feedstock particle diameter and dezincification rate in a reduction roasting test. It is a figure which shows another process flow of the manufacturing method of the reduced iron agglomerate for steel manufacture which concerns on this invention. It is a figure which shows typically a double roll type briquette molding machine. It is a figure which shows the influence of the roll gap | interval distance and roll rotation speed which acts on the roll compression pressure in the briquette molding by a double roll type briquette molding machine.

Explanation of symbols

1: dusts, 2: coke or anthracite (carbon material), 3: belt conveyor,
4: Mixer, 5: Rotary kiln, 6: One end of rotary kiln,
7: The other end of the rotary kiln, 8: Cooling device, 9: Vibrating sieve device,
10: Sieve product (sieve reduced iron), 11: Sieve product (sieve reduced iron), 12: Sintering machine,
13: Sinter, 14: Blast furnace, 15: Supply gas in kiln, 151: Gas in kiln furnace, 16: Kiln exhaust gas, 17: Briquette molding machine, 171: Molding roll,
172: Pocket (hole), 18: Molded product, 19: Reduced iron briquette (reduced iron agglomerate), 20: Steelmaking furnace, 30: Raw material, 31: Reduced iron

Claims (4)

After mixing carbonaceous material with granular iron-based dust and sludge containing 1.0 to 10% by mass of zinc component in average composition, reduced roasting is performed to produce reduced iron. A method for producing reduced iron agglomerate for steelmaking, characterized by classifying by sieving after cooling and agglomerating the under-sieving material with a briquetting machine. The reduced iron after agglomeration by the briquette molding machine is circulated before the sieving process, and the sieved product is reduced to a reduced iron agglomerated mineral product, and the sieving material is supplied to the briquette molding machine again. method for producing a steel for reducing iron ingot Naruko according to claim 1, wherein the. A rotary kiln is used as the reduction roasting apparatus, and the method for producing reduced iron agglomerate for steel making according to claim 1 or 2 . Method for producing a steel for reducing iron ingot Naruko according to claim 1-3, characterized by using a double roll-type compression molding machine as the briquette molding machine.

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