JP2002090071A - Method for supplying molding to baking reducing furnace and rotary hearth type reducing furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably supply a molding constituted of an oxidized metal containing a moisture and a powder of a carbon to a reducing furnace and to easily recycle a dust containing the oxidized metal including the moisture or a sludge. SOLUTION: The molding is constituted of the oxidized metal containing the moisture of 10% or more, and the powder containing the carbon. The molding is supplied into the baking reducing furnace by a vibration type supply unit having a vibrating bottom plate 10 constituted at an upper surface of a water repellant resin and sidewalls 11 installed at both sides. The plate 10 preferably has an angle of -5 to -20 deg. to a horizontal plane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for supplying a compact when reducing a metal oxide by supplying a compact comprising a powder containing water to a firing type reduction furnace, and a method for supplying a compact containing water. The present invention relates to a rotary hearth type reduction furnace which is particularly suitable when a molded body composed of powder is used as a raw material.

[0002]

2. Description of the Related Art There are various processes for producing reduced iron and alloyed iron. Among them, a rotary hearth method is used as a process with high productivity. The rotary hearth method is a type of firing furnace (hereinafter referred to as a rotary furnace) in which a disc-shaped refractory hearth lacking a central portion rotates at a constant speed on rails under a fixed refractory ceiling and side walls. This process is mainly used for the reduction of metal oxide. The hearth diameter of the rotary furnace is 10 to 50 m and the width is 2 to 6
m.

[0003] A powder containing a metal oxide as a raw material is mixed with a carbon-based reducing agent, formed into a raw material compact, and supplied to a rotary furnace. Since the raw material compact is laid on the hearth and left on the hearth, it has the advantage that the raw material hardly collapses in the furnace, and there is no problem that the powdered raw material adheres to the refractory. In addition, there is an advantage that the product yield of lumps is high. In recent years, more and more examples have been implemented because of the fact that high productivity and inexpensive coal-based reducing agents and powder raw materials can be used.

Further, the rotary hearth method is also effective for the treatment of reduction and removal of impurities from the blast furnace, converter, electric furnace, and the thinner sludge in the rolling process, and is also used as a dust treatment process. This is an effective process for resource recycling.

The outline of the operation of the conventional rotary hearth method is as follows.

[0006] First, after a sufficient amount of a carbon-based reducing agent necessary for the reduction of the ore, dust, or sludge metal oxide as a raw material is sufficiently mixed, water is removed by a granulator such as a pampetizer. The pellets having a size of several to several tens of mm are produced while pouring water so as to be about 10%. If the raw material ore or the reducing agent has a large particle size, it is pulverized by a pulverizer such as a ball mill, kneaded, and granulated.

The pellets are supplied on a rotary hearth and laid in layers. The pellets laid on the hearth are rapidly heated and fired at a high temperature of around 1300 ° C. for 7 to 20 minutes. At this time, the metal oxide is reduced by the carbon mixed in the pellet, and the metal is generated. The metallization ratio after reduction depends on the metal to be reduced, but is 95% or more for iron, nickel and manganese, and 50% for chromium which is difficult to reduce.
% Or more. In addition, when processing dust generated from the steel industry, zinc mixed into dust due to the reduction reaction,
Since impurities such as lead, alkali metal, and chlorine are volatilized and removed, it is easy to recycle them into a blast furnace or an electric furnace.

As described above, in the metal reduction method using the rotary hearth and the iron treatment dust reduction method, the metal oxide and the reducing agent of the powder are pelletized, and the pellet has a strong structure. Is small, and even when pellet drying is not performed, the water content is about 8 to 11%, so that the powder easily rolls and the adhesion of powder is small. In addition, since a material whose moisture is dried to 1% or less by a dryer is generally supplied into the furnace, a simple vibratory feeder or a shuttle conveyor in which a charging position is moved is used as a pellet supplying device into the furnace. And so on.

[0009]

As described above, the reduction of metal oxide by the conventional rotary hearth method is excellent in productivity and production cost, and is a method for economically producing metal. However, in this method, it is an important operation technique to make a mixture of the raw material and the reducing agent into pellets, and a raw material having high granulation performance is selected or an expensive pulverizer is installed to pulverize the raw material well. Therefore, it is necessary to improve the granulation properties, and there has been a problem that the cost is high.

That is, when using an ore such as an iron ore as a raw material, the particle size of the raw ore is generally large.
After pulverizing to an average particle size of 10 to 50 microns, granulation was performed to produce pellets. As a result, there are drawbacks in that the equipment for the pulverizing step is expensive, that power is required for operating the pulverizer, and that maintenance costs are required due to wear of the pulverizer.

Further, in order to save the cost of pulverization, a raw material of fine powder may be used, but the selectivity of the raw material is strict and it is not a general-purpose method. Therefore, it is effective to use fine ore after wet beneficiation, use thickener dust in blast furnaces and converters, dredge sludge in scale pits in the rolling process, sedimentation sludge in the pickling process, and the like. However, even in this case, the raw material contains too much water in some cases, making granulation difficult. That is, these raw materials have a particle size of 1
As a result, in a state containing water, these tend to be sludge-like, and even after dewatering with a vacuum dehydrator or a filter press, the water content is 20 to 40.
%, And because it has too much water as it is, a step such as drying is required, and granulation with a bread-type pelletizer was not economical.

Therefore, the inventors of the present invention have disclosed in Japanese Patent Application No. 2000-1.
In 24449, as a granulation method that does not cause explosion inside the reduction furnace even in a state containing moisture, a molded product having a relatively high porosity is formed by an extrusion molding method or a compression molding method using a twin roll with a mold. And a method of reducing it in a sintering reduction furnace such as a rotary hearth. In this method, it was possible to reduce powder containing a large amount of water by 10% or more by a simple method. However, there was a problem in supplying a compact of the powder containing a large amount of water into a furnace. was there.

That is, it has been found that the following problems occur when a molded body containing 10% or more of water is supplied by using a conventional vibratory molded body supply device. Molded products with high moisture are difficult to roll because they are easy to deform,
There is a drawback that a normal type of vibrating supply device cannot be easily supplied due to the tackiness due to moisture. In addition, the powder containing moisture generated by peeling off the surface of the molded body easily adheres to the bottom plate, and when the adhesion of the powder is accumulated, the molded body does not flow on the surface of the bottom plate, so that the supply of the molded body cannot be continued for a long time. There were also problems.

[0014] As a molded body supply device other than the vibration type, there is a shuttle conveyor or the like in which a charging position is moved. However, since a molded body containing a large amount of water does not roll on the hearth, the molded body is placed on the hearth. There is a portion where the particles accumulate and a portion where there is no molded body. As a result, the distribution of the compacts on the hearth becomes non-uniform, and there is a problem that the area of the hearth cannot be used efficiently, and the productivity has deteriorated. Also, in other complicated molded product supply equipment, even if the problems of quantitative supply and uniformity of distribution of the molded product in the hearth can be solved, the surface of the molded product adheres to powder containing moisture that is powdered. Could not be resolved.

As described above, conventionally, there is a technical problem in supplying a compact made of a powdered material containing water to a sintering reduction furnace such as a rotary furnace, and a new technique for solving this problem has been proposed. Was sought.

An object of the present invention is to provide a method for stably supplying a compact of powder containing 10% or more of water into a reduction furnace and a rotary hearth type reduction furnace.

[0017]

According to the present invention, there are provided (1) to (1)
It is as 1).

(1) A molded body composed of a powder containing metal oxide containing 10% or more of water and carbon and having a negative finite angle with respect to a horizontal plane in the direction of travel of the molded body. And sintering is provided in a sintering reduction furnace by a vibratory supply device including an oscillating bottom plate having an upper surface made of a water-repellent resin and side walls provided on both sides thereof. A method for supplying a compact to a reduction furnace.

(2) The method according to (1), wherein the bottom plate has an angle of -5 to -20 degrees with respect to a horizontal plane.

(3) A vibratory feeder composed of a vibrating bottom plate and a side wall as a supply device for the compact, and an upper surface of the bottom plate that moves in the compact movement direction above the bottom plate. (1) or (2), wherein the method for supplying a compact to a sintering reduction furnace is characterized by using a compact supply device comprising a combination of a scraper having an interval of 2 mm or less.

(4) The method for supplying a compact to a firing reduction furnace according to any one of the above (1) to (3), wherein a water-repellent resin is used on the entire surface in contact with the compact.

(5) The above (1) to (4), wherein an ethylene tetrafluoride resin is used as the water-repellent resin.
The method for supplying a compact to the firing reduction furnace according to any one of the above.

(6) As a powder containing a metal oxide, use is made of dust or sludge generated from a metal manufacturing process, and the powder is formed into a firing reduction furnace according to any one of the above (1) to (5). Body supply method.

(7) A vibrating bottom plate having a negative finite angle with respect to the horizontal plane and having a top surface made of a water-repellent resin in the traveling direction of the molded body, and A rotary hearth-type reduction furnace, characterized by having a vibratory feeder comprising:

(8) The angle formed between the vibrating bottom plate made of the water-repellent resin and the horizontal plane is from -5 to -20.
(7) The rotary hearth type reduction furnace according to the above (7).

(9) A vibrating feeder comprising a vibrating bottom plate and a side wall, and a scraping plate which is movable above the bottom plate in a moving direction of the compact with a distance from the upper surface of the bottom plate being 2 mm or less. The rotary hearth-type reduction furnace according to the above (7) or (8), further comprising a molded body supply device obtained by combining the above.

(10) The above-mentioned (7) to (7), wherein the entire surface in contact with the molded body is coated with a water-repellent resin.
The rotary hearth-type reduction furnace according to any one of (9).

(11) The rotary hearth-type reduction furnace according to any one of (7) to (10), wherein the water-repellent resin is an ethylene tetrafluoride resin.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 shows an example of an apparatus for reducing a metal oxide by a sintering reduction furnace using a molded body containing a large amount of water according to the present invention. This includes a mixing tank 1 for a powdery raw material containing water, a slurry transport device 2, a dehydrating device 3, a dehydrated product conveyor device 4, a molding device 5, a molded product conveyor 6, a molded product supply device 7, a rotary furnace 8, and , Consisting of ancillary equipment. The present invention is particularly effective as a method for supplying a molded product containing water into a furnace by the rotary hearth method, but is a technique applicable to reduction furnaces other than the rotary hearth method.

First, a metal oxide powder having a high water content, generally a water content of 50% by mass or more and a raw material made of a reducing agent mainly composed of carbon are mixed in the mixing tank 1. . The solid-liquid mixture is transported to the dewatering device 3 by the slurry transport device 2, where the water content is dehydrated to about 10 to 30% to form a water-containing aggregate of the raw material mixture. Dehydration device 3
As, a dehydrating device of a type that is poured onto a circulating moving filter cloth and squeezed by a pair of squeezing rolls installed above and below the filter cloth,
A filter press or a centrifugal separator may be used, and a model in which the water content after dehydration is 10 to 30% is selected.

The raw material aggregate is sent to the molding device 5. Here, a compact having a thickness of about 20 mm or less is produced. Molding device 5
For example, a twin-roll compression molding machine (a briquette molding machine) with a mold, a molding machine of a type for extruding aggregates from a hole mold, or the like is used.

The molded powder is transferred to a molded product conveyor 6
It is sent to the compact supply device 7 installed at the material inlet of the rotary furnace 8. The compact supply device 7 is a vibratory supply device, and its detailed structure is shown in FIG. The vibratory feeder has a bottom plate 10 on which a compact is placed, and side walls 11 on both sides thereof. The vibration device 13 and the bottom plate 10 are connected by a vibration transmission unit 12.
The upper surface of the bottom plate 10 is made of a resin having water repellency. There are several types of resins having water repellency, but since the molded body supply device 7 is installed in a relatively high temperature place, a resin that can withstand a temperature of about 150 ° C. is desirable.

The reason why the bottom plate 10 is made of a resin having water repellency is as follows.

[0034] Compared to a dried molded product, a molded product containing water has an adhesive property and slips poorly on the bottom plate 10, and it is difficult to supply a stable molded product with a general vibratory feeder. It is. In particular, dust and sludge containing metal oxides generated from processes such as metal refining and rolling are formed into compacts,
This phenomenon becomes remarkable when used in a reduction furnace. These dusts and sludges are fine particles having a particle size of about 1 to 30 microns, and when the water content is 15% or more,
In particular, the adhesiveness is high.

When the water content of the molded product is about 10% or less, if the powder has a relatively large particle size, the problem of the stickiness of the molded product is not remarkable, but the molding containing the water content of 10% or more is not significant. In the body, the problem of stickiness of the molded body began to appear,
In the case of a molded body having a water content of 16% or more, it is impossible to stably supply a fixed amount with a normal vibration-type supply device. In addition, in order to supply such a viscous molded body, if the inclination angle of the vibrating bottom plate is set to be large, the molded body can be supplied, but the molded body rolls on the bottom plate. The function of the vibration-type supply device, which spreads over the entire bottom plate and supplies a constant amount without change, is impaired, and there is a problem of adhesion of peeling powder, which will be described later.

Therefore, the bottom plate 10 is made of a water-repellent resin which is not easily blended with water for the purpose of improving the slip of the molded body on the bottom plate 10. Adhesion between the water-repellent resin and the water-containing molded article can be reduced to facilitate the movement of the molded article. In addition, the effect of forming the bottom plate 10 from a resin having water repellency may prevent powder generated when supplying a molded body from adhering to the bottom plate 10. When the molded body is subjected to vibration, the surface is peeled off and powder is generated. When the water content of the molded body is low, the powder has poor adhesion and does not adhere to the surface even if the bottom plate is made of iron. However, when the molded body has a large amount of moisture, the powder is strongly adhered. With metals such as iron and aluminum, the powder adheres to the plate surface and accumulates, so that the molded body flows on the bottom plate 10. Inhibit going. By forming the surface of the bottom plate 10 with a water-repellent resin such as ethylene tetrafluoride resin, a molded body can be continuously supplied for a long time without adhering even a powder containing water.

In addition, not only the bottom plate 10 but also all the portions that come into contact with the molded body, such as the side wall 11, the powder containing moisture generated by the exfoliation of the surface of the molded body accumulates, and obstructs the flow of the molded body. Therefore, by covering the entire surface of the portion such as the side wall 11 that comes into contact with the molded body with a resin having water repellency, adhesion of the powder containing water to the side wall 11 and the like can be prevented, and the molded body can be stably supplied.

The present inventors have conducted experiments using various water-repellent resins, and as a result, it has been found that ethylene tetrafluoride resin is the most excellent as a resin having good sliding properties and high heat resistance. It was confirmed. Therefore, as the resin constituting the bottom plate 10 as the water-repellent resin, ethylene tetrafluoride resin is most desirable.

Further, the bottom plate 10 is inclined so that the compact can be supplied stably and at a high speed.
The inclination angle (the angle formed by the bottom plate with respect to the horizontal plane) differs depending on the type of the molded body and the water content, but is small in a molded body having a shape close to a sphere or a cylinder, and is large in a flat molded body. In the case of a molded article having a shape close to a sphere or a cylinder, a remarkable effect on improving the supply speed was recognized when the inclination angle exceeded -5 degrees. In the case of a flat molded body, a remarkable effect on improving the supply speed was observed when the temperature exceeded -7 degrees. However, if the angle of inclination exceeds minus 20 degrees, the molded body will
It has been found out that the upper surface of the molded product is rolled, and the function of the fixed amount supply of the molded body supply device 7 is impaired. Therefore, the inclination angle is desirably −5 degrees to −20 degrees.

Even if the above-mentioned measures are taken, a compact formed of fine particles having a particle size of several microns or less can be used.
%, There is a problem that powder accumulates on the water-repellent resin. To solve this problem, a device for scraping off the powder on the bottom plate 10 as shown in FIG. 2 is installed.

For the purpose of shaving the powder on the bottom plate 10, the scraping plate 14 made of a relatively rigid material such as metal or rubber is moved in the moving direction of the compact. The scraper 14 is a support 15
Are connected to the driving device 16, and the driving device 16 moves along the guide rail 17. When the scraping plate 14 returns, the scraping plate 14 jumps up and takes a large distance from the bottom plate 10.

Here, it is an important requirement that the distance between the scraping plate 14 and the upper surface of the bottom plate 10 be 2 mm or less. When the distance is more than 2 mm, even after the powder is exfoliated, a part of the powder remains on the bottom plate and deteriorates the flow of the molded body. Therefore, the distance between the scraping plate 14 and the upper surface of the bottom plate 10 is reduced. Is 2 mm or less is a condition of the present invention. If the scraper 14 is a substance harder than a water-repellent resin such as a metal, the scraper 1
It is desirable not to make the 4 contact the bottom plate 10. When the scraper 14 is made of a material softer than the water-repellent resin such as rubber, the scraper 14 may be brought into contact with the bottom plate 10 because the water-repellent resin does not wear.

It is effective for the operation of the reduction furnace that the supply of the compact is continued while the scraping plate 14 is moved and the bottom plate 10 is cleaned. Therefore, in order not to disturb the supply of the compact during cleaning by the scraper 14, it is effective that the relative difference between the moving speeds of the scraper 14 and the compact 10 is within 20%.

In the above-described apparatus, the supplied compact is heated in a rotary furnace 8 to a high temperature of 1200 to 1350 ° C.
The metal oxide is reduced by the carbon inside the compact. The reduced compact is discharged from the furnace, cooled in the cooler 9, and sent to the metal manufacturing process as granular reduced metal.

Although the rotary furnace shown in FIG. 3 is efficient as a reducing furnace, it can also be applied to a shaft furnace such as a rotary kiln or a cupola. However, in the case of a rotary hearth-type reduction furnace, in particular, the present invention can be used most effectively because it is necessary to disperse the molded body on the hearth and lay it down thinly.

[0046]

EXAMPLES The results of the operation of the present invention and the results of operation by a conventional method as a comparative example are shown.

In the first embodiment, the surface of the bottom plate of the vibration-type molded product supply device 7 is made of a water-repellent resin with the equipment shown in FIG.
An apparatus using ethylene tetrafluoride, a bottom plate having a width of 1 m and an inclination angle of the bottom plate of minus 8 degrees was used. In the second embodiment, the apparatus of the first embodiment is provided with a device for cleaning the bottom plate surface with a hard rubber plate every 60 seconds. The distance from the bottom plate was 2 mm. In the comparative example, the same apparatus as in Example 1 was used except that the surface of the bottom plate was a carbon steel plate. The molded body used had a cylindrical shape with a diameter of 15 mm and a length of 20 to 35 mm. The average particle diameter of the powder constituting the compact was 7 microns, and the water content was 23%.

In the comparative example, the molded body was hard to roll on the bottom plate, and the moving speed of the molded body was not increased. As a result, a feed rate of only 5.7 tons per hour was obtained. Also, 1
After only 5 minutes of feeding, powder adheres to the bottom plate,
The supply of the molded product became impossible.

On the other hand, in Example 1, the molded article flowed smoothly on the ethylene tetrafluoride resin, and the molded article was supplied stably. As a result, the movement of the molded body was smooth and 17.1 hours / hour.
A feed rate of tons was obtained. Also, during 3 hours, there was no supply failure due to the adhesion of powder on the bottom plate. At the time of the supply failure, only the strong vibration was applied, and the adhered material was peeled off, and the supply of the molded product could be continued again, and the operation of the reduction furnace was not hindered.

Also in Example 2, the movement of the compact was smooth, and a feeding speed equivalent to that of Example 1 was obtained at 18.3 tons / hour. In addition, by the device that cleans the bottom plate surface with a hard rubber plate,
The bottom plate surface was always kept clean. As a result, no supply failure occurred due to the adhesion of the powder on the bottom plate.

As described above, according to the present invention, it was possible to stably supply a compact which does not roll easily to a reduction furnace for a long time because it contains water. As a result, in the rotary hearth-type reduction furnace, the compacts could be uniformly spread on the hearth, and a good reduction operation could be performed in both the fuel consumption rate and the productivity.

[0052]

According to the present invention, a compact containing metal oxide and carbon containing 10% or more of water can be stably supplied into the reduction furnace, and the compact can be efficiently reduced. .
In particular, it is effective for a rotary hearth type reduction furnace. It is an effective means for treating dust and sludge generated in the metal smelting industry.

[Brief description of the drawings]

FIG. 1 is an external view of a vibration-type supply device used in the present invention.

FIG. 2 is an external view of another example of the vibration-type supply device used in the present invention.

FIG. 3 is a schematic view of a metal oxide reduction furnace including a rotary hearth-type reduction furnace of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mixing tank 2 Slurry transport device 3 Dehydration device 4 Dehydration material conveyor device 5 Molding device 6 Molded material conveyor 7 Molded material supply device 8 Rotary furnace 9 Cooler 10 Bottom plate 11 Side wall 12 Vibration transmission unit 13 Vibration device 14 Scratching plate 15 Support 16 Drive 17 Guide rail

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F27B 9/18 F27B 9/18 R 9/38 9/38 F27D 3/06 F27D 3/06 A // C22B 7/00 C22B 7/00 H 7/02 7/02 A (72) Inventor Tetsuharu Ibaraki Kimitsu 1 Kimitsu Works Inside Nippon Steel Corporation Kimitsu Works (72) Inventor Shoji Imura 1 Kimitsu 1 Kimitsu City New Japan F-term (reference) in Kimitsu Works 4K001 AA10 BA05 BA14 BA15 DA05 GA10 GA19 GB01 HA01 HA04 4K012 DE01 DE06 4K018 AA24 AB07 AC01 BA13 BC13 4K050 AA04 BA02 CA09 CF07 CG22 4K055 AA05 BA03 EA07

Claims (11)

[Claims] 1. A molded body composed of a powder containing metal oxide containing 10% or more of water and carbon and having a finite angle of a negative value with respect to a horizontal plane in a traveling direction of the molded body, And a sintering reduction apparatus characterized in that the sintering reduction furnace is supplied by a vibratory supply apparatus including a vibrating bottom plate having an upper surface made of a water-repellent resin and side walls provided on both sides thereof. How to supply the compact to the furnace. 2. The apparatus according to claim 1, wherein the bottom plate has an angle of -5 to -20 degrees with respect to a horizontal plane.
A method for supplying a compact to a firing reduction furnace as described in the above. 3. A molded product supply device comprising: a vibrating supply device composed of a vibrating bottom plate and a side wall; and a moving body moving in a molded body moving direction above the bottom plate, and a top surface of the bottom plate. 3. The method according to claim 1, further comprising using a compact supply device that combines a scraper with an interval of 2 mm or less. 4. The method for supplying a compact to a firing reduction furnace according to claim 1, wherein a water-repellent resin is used on the entire surface in contact with the compact. 5. The method according to claim 1, wherein an ethylene tetrafluoride resin is used as the water-repellent resin.
The method for supplying a compact to a sintering reduction furnace according to the above item. 6. The molding into a sintering reduction furnace according to claim 1, wherein dust or sludge generated from a metal production process is used as the powder containing the metal oxide. Body supply method. 7. A vibrating bottom plate having a negative finite angle with respect to a horizontal plane in the advancing direction of the molded body and having an upper surface made of a water-repellent resin and provided on both sides thereof A rotary hearth-type reduction furnace, comprising a vibratory feeder composed of side walls. 8. The rotary hearth type reduction furnace according to claim 7, wherein the angle formed between the vibrating bottom plate made of the water-repellent resin and the horizontal plane is -5 to -20 degrees. 9. A vibratory feeder comprising a vibrating bottom plate and a side wall, and a scraper plate movable above the bottom plate in a direction in which the molded body moves in a state in which a distance from the upper surface of the bottom plate is 2 mm or less. The rotary hearth-type reduction furnace according to claim 7 or 8, further comprising a molded body supply device obtained by combining: 10. The rotary hearth-type reduction furnace according to claim 7, wherein a water-repellent resin is coated on the entire surface in contact with the molded body. 11. The rotary hearth type reduction furnace according to claim 7, wherein the water-repellent resin is an ethylene tetrafluoride resin.