JP2003089823A - Converter dust recycling method for rotary hearth type reduction furnace - Google Patents

Abstract

(57) [abstract] (with correction) [PROBLEMS] A process of forming fine dust collected from converter gas and reducing and dezincing it as a raw material compact in a rotary hearth type reduction furnace. Perform efficiently. SOLUTION: The dust collected from the converter gas is in a state in which the water content is 5 to 16% by mass and the content of metallic iron is 8 to 35% by mass. And a powder containing carbon are mixed to produce a molded body. This compact is placed inside the rotary hearth reduction furnace 10,
Reduce and dezincify. At this time, an efficient reduction treatment is performed by devising a storage method, a molding method and a reduction method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recycling converter dust collected in a non-combustion type gas treatment apparatus generated in an integrated steelworks as iron raw material in a rotary hearth reduction furnace. It is a thing.

[0002]

2. Description of the Related Art In the integrated steelmaking industry using blast furnaces and converters, one steel mill produces 3 to 10 million tons of steel annually, which is a very efficient steelmaking method. In the converter, oxygen is blown to the molten pig iron and scrap produced in the blast furnace, and the temperature is raised by the heat of combustion of carbon and silicon in the pig iron to obtain molten steel having a low carbon concentration.
At this time, a gas mainly containing carbon monoxide is generated from the converter. The amount of gas is 100 Nm ³ per ton of pig iron.
About 100 g / Nm ^{3 of} this converter gas, that is, 10 kg
Iron dust of about / t-steel is mixed.

Iron dust mixed in the converter gas (hereinafter referred to as converter dust) includes coarse particles and fine particles. Coarse-grained converter dust has a particle size of 100 μm to 1 mm
The molten iron in the converter is blown away and contains 80 to 90% of metallic iron and about 10% of iron oxide. The fine-grain converter dust has a particle size of about 1 to 5 μm. This is because the heat of combustion of oxygen evaporates the molten iron in the converter, agglomerates it, and blows it away with the gas. It contains about 70% metallic iron and about 30% iron oxide. It is a thing. The fine-grain converter dust also contains zinc originating from scrap, which is also evaporated from the inside of the converter furnace. Normally, the zinc concentration varies depending on the zinc content of the scrap used, etc.
It is about 0.2 to 1%.

The converter gas is collected by a non-combustion type gas treatment device, a so-called OG device, and is used as a fuel gas for power generation and heating of steel after being collected with dust. The OG device has a Venturi scrubber type dust collector, and collects dust while sprinkling water. Converter dust in the collected water is first separated into coarse particles in a primary settling tank and poured into a thickener. In the thickener, fine converter dust is precipitated, and the thickened one is dehydrated with a dehydrator to a water content of 20 to 30%.

Since coarse-grain converter dust has a large particle size, a high metallic iron ratio, and a low zinc ratio, various recycling methods have been carried out as useful iron resources. In particular, it is recycled by using it as a raw material for a sintering machine or by replacing it with scrap in a converter.

On the other hand, however, the fine grain converter dust is 1 to 5
Since the particle size is very small (μm), the specific surface area is large and the oxidation of metallic iron during storage is severe. Because of the exothermic phenomenon that accompanies this oxidation, it is difficult to simply use fine converter dust, and there are also component problems such as zinc,
This is also an obstacle to recycling.

[0007] First, as an effective means for recycling fine converter dust, a method of supplying silicon into the hot metal after being tapped from the blast furnace to remove silicon and phosphorus in the hot metal has been used. In addition, it is partly done to select the part with less zinc and recycle it to the blast furnace via the sintering machine. Thus, various methods have been used for recycling fine converter dust. However, since the amount of fine converter dust that can be recycled is limited by the conventional methods other than the method used for the blast furnace, it is impossible to recycle all the fine converter dust only by these methods.
Therefore, in order to use a large amount of fine converter dust, it is effective to recycle it to the blast furnace.

However, the fine-grain converter dust contains zinc, and its use as it is is limited. In other words, since zinc in the fine converter dust is large,
When recycled to a blast furnace through an iron ore sinter, zinc evaporates in the high temperature part of the blast furnace and becomes zinc oxide or zinc chloride, which adheres to the furnace wall of the blast furnace. As a result, there is a problem that ore and coke in the blast furnace will not descend in the furnace.

As a measure against this problem, if fine converter dust is dezincified, it can be used in a blast furnace. For this reason, attempts have been made to use it in a blast furnace by dezincing it by the Welz kiln method or rotary hearth method. Of these, the rotary hearth method has a high dezincification rate of 90% or more, and since reduced iron can be obtained, an increasing number of examples are being used as a dezincification process. Recently, as shown in Japanese Patent Laid-Open No. 2000-34526, which is a patent filed by the present inventors, a method has been developed for increasing the strength of pellets reduced by the rotary hearth method until the pellets can be used in a blast furnace. Has come to be used in.

The rotary hearth method is a type of firing furnace in which a disc-shaped refractory hearth lacking a central portion is rotated at a constant speed under a fixed refractory ceiling and sidewalls. Is mainly used for the reduction of metal oxides and the treatment of iron-making dust. Rotary furnace reduction furnace has a hearth diameter of 1
It has a width of 0 to 50 meters and a width of 2 to 6 meters. A raw material is powder, and a rotating pan-shaped granulating device generally uses granulated spherical pellets. In order to use the fine converter dust in a rotary hearth reduction furnace, the fine converter dust alone or a mixture with other iron oxide-containing powder is used as a powder containing carbon such as powder coke. Mix to produce spherical pellets. This is calcined and reduced in a rotary hearth reduction furnace.

[0011]

The fine converter dust contains a content of 20 to 30% of water even after dehydration, and there is a problem due to the fact that it is very fine. If the moisture content of fine converter dust is reduced, the handling property and the mixing property are improved. However, in the prior art, there is only the recognition that the fine grain converter dust should be simply dried, and various problems as described later have occurred.

[0012] As disclosed in the patent of Japanese Patent Laid-Open No. 2000-54034, conventionally, the fine grain converter dust has been treated in a rotary hearth type reduction furnace. However, firstly, if the fine-grain converter dust is simply dried too much, the metallic iron reacts with the air to start oxidation and generate heat because the specific surface area is large in the fine-grain state. In particular, in the prior art, since it is important to handle powder as a powder and prevent seizure in the storage tank,
Excessively dried fine converter dust may cause a serious problem of heat generation. In severe cases, the temperature rises to around 800 ° C, which could cause a fire.

In order to prevent the heat generation problem in the use process,
There is also a method of completely oxidizing fine converter dust in advance.
However, in this case, during the oxidation treatment of metallic iron in the pretreatment for recycling, if the peaks of the fine particle converter dust are severe, the fine particle converter particles are heated to 800 ° C. or higher, and the fine particles of the fine particle converter dust are separated from each other. However, there is a problem that the average particle size increases due to the sintering reaction. Due to the sintering phenomenon, some particles become several to several tens of mm or more, and become a strong sintered mass. If this is not crushed, it cannot be mixed with other powders for granulation, and even in that case, the average particle size may become too large, and pellet granulation may be difficult. It was In particular, the deterioration of the granulation property is remarkable, and there is a problem that stable pellets of high quality cannot be produced by using sintered fine particle converter dust having a particle size of several tens of μm or more. That is, there is a technical problem in the method of completely proceeding the oxidation.

Conventionally, due to the above-mentioned problem of heat generation due to oxidation, etc., the ratio which can be used by mixing with other powder has been limited. In addition, when using the finely pulverized converter dust that is almost completely oxidized, there is a problem in that the operation of pre-oxidizing and the crushing treatment of the finely pulverized converter dust that has been burned are expensive. Further, since the dust containing the metallic iron that has been recovered is oxidized and used as a raw material, it takes a large amount of reduction energy per unit for reduction in the rotary hearth reduction furnace, which is not an economical method.

The fine converter dust has an average particle size of 1 to 5 μm, and therefore becomes clay like when it contains water, which makes it difficult to handle, which is a serious obstacle to the recycling of the fine converter dust. Was there. In other words, there is also a problem that fine converter dust is trapped inside the storage tank and causes discharge failure. As a countermeasure against this problem, if the fine converter dust is dried, the metal iron contained therein easily oxidizes, so that the problem of oxidation heat generation of the fine converter dust inside the storage tank has occurred.

Since these problems have not been solved, in the prior art, fine converter dust is mixed with other iron-containing dust, etc., in a soil using a heavy machine, and this mixture is mixed with a rotary hearth type. It was used as the raw material for the reduction furnace. However, with this method, the raw materials could not be quantitatively and stably mixed. As a result, it is possible to sufficiently stabilize the granulation of the powder and the reduction reaction in the rotary hearth reduction furnace by realizing the proper mixing ratio by mixing the raw materials in a fixed amount. It wasn't done. That is, the process of the rotary hearth reduction furnace when the fine converter dust is used as a part of the raw material is not always stable.

Further, there is no sufficient knowledge about the method of reducing fine converter dust in a rotary hearth reduction furnace, and in the prior art, pellets produced simply by mixing carbon powder and fine converter dust were used. Only the recognition that reducing at high temperature is necessary, and the reduction furnace treatment that is used efficiently and in large quantities has not been performed.

As described above, it was technically difficult to produce raw pellets that can be used in the rotary hearth method, using the fine converter dust as a raw material. Therefore, there has been a demand for a new technique for producing pellets for a rotary hearth type reduction furnace by using fine grain converter dust as a part of a raw material and reducing the pellets.

[0019]

The present invention has been made in view of these problems, and the gist thereof is as follows: (1) Dust is collected by a non-combustion type dust collector of converter gas and thickener precipitation is performed. The converter dust collected as a product has a moisture content of 5
16 mass% and the ratio of contained metallic iron is 8 to 35
In a state of mass%, after mixing the powder containing iron oxide and the powder containing carbon, a molded body is manufactured, and the molded body is reduced in a rotary hearth reduction furnace. Recycling method of converter dust for rotary hearth reduction furnace. (2) The converter dust is stored in a storage tank in a state where the water content is 5 to 16 mass% and the ratio of the contained metal iron is 8 to 35 mass%, and the converter dust is stored. The converter dust is recycled to the rotary hearth reduction furnace according to (1), which is cut out by a quantitative cutting device and mixed with a powder containing iron oxide and a powder containing carbon at a predetermined mixing ratio. Method. (3) A pan-type granulating device is provided with a converter dust collected by a non-combustion type dust collector of converter gas and collected as a thickener precipitate, and a mixture of powder containing iron oxide and powder containing carbon. To a rotary hearth type reduction furnace according to the above (1) or (2), characterized in that spherical pellets are produced using the above method and the pellets are reduced inside the rotary hearth type reduction furnace. Converter dust recycling method. (4) Spherical pellets are manufactured using a pan-type granulator after mixing and pulverizing converter dust, powder containing iron oxide and powder containing carbon, and pulverizing the powder. A method for recycling converter dust to a rotary hearth type reduction furnace as described. (5) The converter dust collected by the non-combustion type dust collector of the converter gas and collected as thickener precipitates, and the mixture of the powder containing iron oxide and the powder containing carbon were formed into a plurality of concaves on the roller. The rotary hearth type reduction furnace according to any one of (1) and (2) above, characterized in that the briquette molded body is manufactured by molding in the concave shape. Converter dust recycling method. (6) Atoms of carbon contained in a mixture of converter dust, powder containing iron oxide and powder containing carbon, and oxygen of iron, manganese, nickel, chromium, lead and zinc oxide The molar ratio is in the range of 0.5 to 1.5,
The rotary hearth type reduction furnace according to any one of (1) to (5) above, wherein the compact is present in a portion where the gas temperature during reduction is 1200 ° C. or higher for 6 minutes or longer. Converter dust recycling method. (7) Thickener precipitate is collected by a non-combustion type dust collector of converter gas in a state where the water content is 5 to 16% by mass and the ratio of contained metallic iron is 8 to 35% by mass. The converter dust collected as is stored in a storage tank in which the lower cone portion is heated and an inert gas mixed therein with an oxygen concentration of 5% or less is flowing. The converter dust recycling method for a rotary hearth type reduction furnace according to (2) above, wherein the converter dust is cut out with a feeder and mixed with other powder. (8) Per ton of converter dust stored in stock is 0.
(5) Nitrogen having an oxygen concentration of 5% or less mixed as impurities of 5 normal cubic meters / or more is flowed, and the converter dust recycling method for a rotary hearth reduction furnace according to (7) is provided.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a dust reduction process by a rotary hearth method having a pan type powder granulating apparatus for carrying out the present invention. The facilities include a fine grain converter dust storage tank 1, another powder storage tank 2, a powder coke storage tank 3, and a binder storage tank 4 for storing raw materials, and further, a powder conveyor 5, a powder crushing and mixing apparatus 6, Crushed material conveyor 7, bread type granulator 8
There is. Further, there is a rotary hearth type reduction furnace 10 which is a dust reduction device via the pellet conveyor 9, and an exhaust gas treatment device 11 and a reduced iron cooling device 12 are attached to this.

First, the pretreatment of the fine grain converter dust as a raw material will be described. The fine converter dust generated together with the converter gas was converted into wet dust from the converter dust and a slurry of water by a bench yuly scrubber, and then
After separating large particles of about 0 μm or more, dust is concentrated with a thickener and water content is 25-35% by mass with a dehydrator.
And At this time, the chemical components of the fine converter dust are about 60 to 70 mass% of metallic iron and about 20 mass% of iron oxide,
The average particle size is about 1 to 5 μm. Further, zinc concentration in the scrap used in the converter is generally 0.2 to 1% by mass due to the concentration of zinc in the fine converter dust.

The fine converter dust is dried to a water content of 5 to 16 mass%. The reason for setting the water content in the range of 5 to 16% by mass will be described in the description of the method for stocking fine grain converter dust. The method for utilizing the heat of oxidation of metallic iron is desirable for drying the fine converter dust. Any method can be used,
Air is passed through the device that rotates the cylinder to oxidize the metallic iron in the fine converter dust, or the fine converter dust is spread to the yard to oxidize the metallic iron through the air to evaporate the water by the heat of oxidation of iron. The method of making it economical is economical.

At this time, the degree of oxidation of the fine converter dust is adjusted so that the residual metallic iron is 8 to 35% by mass. As a method of knowing the degree of oxidation, a method such as measuring and controlling the rate of change in water content of fine converter dust (water evaporation amount) is used. When the ratio of metallic iron becomes too low to remove water, the water before treatment is adjusted in advance by a method such as sun drying.

When the ratio of metallic iron is 8% or less, under normal conditions, the heat of combustion of metallic iron is generated more than the heat involved in drying, so that the temperature of the fine grain converter dust becomes too high, and There is a problem that the parts are sintered and a lump that is difficult to handle is formed. Further, since the oxidation proceeds too much, there arises a problem that the reduction energy in the rotary hearth type reduction furnace which is a post-process increases. On the other hand, when the metal iron ratio after drying is 35% by mass or more, when the water content of the fine particle converter dust before drying is 25% by mass or more, the calorific value necessary for drying cannot be secured,
External energy supply is required for drying. As a result, drying requires additional equipment and energy, which is not an economical method. Therefore, as the property of the fine converter dust in the present invention, the ratio of metallic iron is 8 to 35.
It is important to be% by mass. Further, when the water content is relatively low and the metallic iron ratio exceeds 35% by mass, heat generation due to the oxidation of metallic iron in the stockpiling is severe and there is also a problem of damaging the machine. It is important to be.

Fine particle converter dust having a water content of 5 to 16 mass% and a metal iron ratio of 8 to 35 mass% is received in the fine particle converter dust storage tank 1. Since fine converter dust has an average particle size of about 1 to 5 μm, if the water content is less than 5%, dust will be generated significantly when it is unloaded from a truck or handled in the yard, which causes environmental problems. Occurs. Further, as described above, the fine converter dust having a water content of 5% by mass or less has a good contact with the air, and the heat of the metal iron oxidation heat is intense, which may cause equipment damage. Therefore, the water content is controlled to be 5% by mass or more.

Further, since the fine converter dust is fine particles, the fine converter dust containing a large amount of water is likely to be in the form of clay and is difficult to be discharged from the fine converter dust storage tank 1. . The inventors of the present invention have found that when the water content is 16% by mass or more, the phenomenon of seizure of fine converter dust inside the fine converter dust storage tank 1 frequently occurs. Therefore, the water content of the fine converter dust is set to 16% by mass or less.

In the fine particle converter dust storage tank 1,
The temperature inside the tank rises slightly due to the gradual reaction between the fine converter dust and the oxygen in the air. By this reaction,
The temperature of the fine converter dust in the fine converter dust storage tank 1 is 10 to 40 ° C. higher than the outside air temperature. As a result,
Moisture in the fine converter dust evaporates gradually. When this water vapor reaches the iron shell of the fine grain converter dust storage tank 1, dew condensation occurs here. This phenomenon also occurs in the cone portion 10 below the fine grain converter dust storage tank 1. As a result, the fine converter dust cannot be discharged from the cone portion 10.
As described above, even if the water content of the fine converter dust is 16% by mass or less, there is a problem that defective powder discharge from the cone portion 11 occurs.

In order to solve this problem, the cone portion 13 under the fine grain converter dust storage tank 1 is heated. Although any heating method may be used, it is preferable to heat with an electric heater or a steam heater. In the example of the device of FIG. 2, the heating device 14 is an electric heater. Since the purpose of the cone portion 13 is to prevent dew condensation, the heating temperature of the cone portion 13 is preferably 50 to 80 ° C.

By heating the cone portion 13, when dew condensation is prevented, water vapor that has not returned to water at this portion rises inside the fine grain converter dust storage tank 1. When the water content of the fine converter dust is small, there are few problems, but when the water content is high, this steam rises inside,
In some cases, it may accumulate on the side wall of the fine grain converter dust storage tank 1. As a result, the fine converter dust is trapped in this portion. In order to solve this problem, an inert gas is allowed to flow inside the fine grain converter dust storage tank 1. The inflow port is preferably located in the cone portion 13. In FIG. 2, which is an example of the equipment of the present invention, an inert gas is supplied from a gas supply pipe 15. By diluting the steam with an inert gas and flowing it, the steam can be well discharged to the outside of the fine grain converter dust storage tank 1.

The need for the gas to be an inert gas is also to prevent the metallic iron of the fine grain converter dust from being oxidized. Therefore, as the inert gas, nitrogen, carbon dioxide gas, etc. are preferable, but impure nitrogen having a concentration of oxygen of 5% or less, combustion exhaust gas, etc. have the same effect. Further, if the flow rate is 0.5 normal cubic meters / hour or more per ton of the fine converter dust stored in the stock, there is a sufficient water vapor discharge effect.

As other powders, blast furnace gas dust and powdered ore are put into another powder storage tank 2, powder coke as a reducing agent is put into the powder coke storage tank 3, and a binder such as bentonite is put into the binder storage tank 4. . If there are many types of raw materials, more storage tanks will be provided.

The powder stored in each storage tank is supplied to the powder conveyor 5
A fixed amount is cut out so that a predetermined ratio is obtained.
This is conveyed by the powder conveyor 5, and the powder crushing and mixing device 6
At, mix and crush. Although there are several mixing machines, a ball mill type crushing and mixing apparatus is most suitable. There is also a method of mixing powders after passing through a crushing device.

Next, the crushed and mixed powder is sent to the pan type granulator 8 by the crushed material conveyor 7. Bread granulator 8
Then, the powder with the water content adjusted to 8 to 13 mass% has a diameter of 3
Spherical raw pellets are produced by rolling on a ~ 6 meter wok pan. The diameter of the raw pellet is preferably 5 to 30 mm. To produce a stable and strong green pellet, 1 to 10 μm fine particles and 50 μm
It is important that the above coarse particles are mixed in an appropriate ratio. Therefore, the fine converter dust with a small particle size is 2
Good green pellets can be produced if they are mixed in a ratio of 0 to 80%.

As a method for producing a molded body, the roller has a plurality of concave molds, and the molding is suitable for the molding of the present invention, which is a method for manufacturing a briquette. In this molding method, the mixed powder is supplied from above the roller and pressed by the roller. At this time, the powder is compressed inside the concave mold to manufacture a molded body. A binder is generally used to maintain the strength of the molded product.

This molded product is sent to the rotary hearth type reduction furnace 10 by the pellet conveyor 9. In the rotary hearth type reduction furnace 10, the compact is calcined and reduced. Occasionally, there is a problem of explosion due to water vaporization of the molded body during heating in the rotary hearth reduction furnace 10, so after drying the molded body,
It is desirable to supply to the rotary hearth reduction furnace 10. In the rotary hearth reduction furnace 10, iron oxide, manganese oxide, chromium oxide, zinc oxide, etc. contained in the fine converter dust and other oxide powders are mixed with carbon in a high temperature furnace. Give back.

In the furnace, a reduction reaction occurs when the temperature of the compact reaches 1100 ° C. or higher. In particular, at a temperature of 1200 ° C. or higher, the reaction becomes active. The temperature inside the molded body is 110
The ambient temperature in the furnace must be 1200 ° C. or higher in order to achieve 0 ° C. or higher and the active reaction. The present inventors have made it possible to achieve a zinc removal rate of 80% or more and an iron reduction rate of 70% or more by setting the atmosphere temperature in the furnace at 1200 ° C. or more for 6 minutes or more. Clarified. Therefore, it is preferable to set the processing time so that the compact containing the fine converter dust is kept in the furnace at 1200 ° C. or higher for 6 minutes or longer.

Under the processing conditions of the rotary hearth method, it is necessary to make the ratio of the substance and carbon reduced in the rotary hearth reduction furnace 10 proper. That is, when the atomic mole ratio (carbon equivalent) of carbon to oxygen of iron, manganese, nickel, chromium, lead and zinc oxide is in the range of 0.5 to 1.5, In addition, treatment with a high reduction rate and a high dezincification rate becomes possible. When the carbon equivalent is 0.5 or less, the reduction does not proceed completely, the reduction rate of iron cannot be 70% or more, and the dezincification rate is about 60 to 80%, which is one of the objects of the present invention. Dezincification cannot be carried out sufficiently. Further, when the carbon equivalent is 1.5 or more, the carbon becomes excessive, and even after the reaction is completed, the carbon remains and inhibits the binding of the particles inside the reduced pellets. There is a problem that it becomes low and cannot be used in a blast furnace.

The compact that has been reduced in the rotary hearth type reduction furnace 10 is discharged from the furnace by a screw type discharge device. The discharged reduced compact is the reduced iron cooling device 12
Then, it is cooled and supplied to the blast furnace as a raw material to become hot metal. Since powdered coke or coal is used as the reducing agent, the sulfur content of the reduced iron is high, and therefore, a blast furnace having a desulfurization function is most desirable as a recycling destination of the reduced compact. However, the effect can also be exhibited by recycling to converters and electric furnaces. The exhaust gas is dedusted by the exhaust gas processing device 11 and is emitted to the atmosphere.

[0039]

EXAMPLES The results of carrying out the present invention will be described. Table 1 shows the results of performing a method of producing spherical pellets using fine grain converter dust having a water content of 5 to 16% by mass and a ratio of metallic iron of 8 to 35% by mass, and reducing the pellets. Show. Table 2 shows the processing results similar to the method of the present invention, but according to the prior art. The equipment is as shown in Figure 1,
The molding method is the result of using a pan-type pelletizer.

First, in the first embodiment, the treatment is performed within the range of the present invention by setting the moisture content of the fine grain converter dust to 12% and the metallic iron ratio to 21%. As a result, the fine grain converter dust storage tank 1
No metallic iron ignition phenomenon occurred inside the. Further, since the water content was appropriate, the payout operation could be carried out relatively smoothly. However, a slight seizure occurred about once every few days, so I responded by hammering. Since the reaction conditions were within the range of the present invention, granulation and reduction proceeded smoothly. As a result, a favorable product with a reduction rate of 81%, a dezincification rate of 93% and a crushing strength of 110 kg was obtained. This product could be used directly in a blast furnace.

In Example 2, which is within the scope of the present invention, fine converter dust having a relatively low water content and a relatively high metallic iron ratio is used. Since the water content was small, there was no problem in discharging the fine converter dust from the fine converter dust storage tank 1. On the other hand, for the purpose of preventing the oxidation of metallic iron, which becomes a problem when the water content is low, the airtightness of the fine grain converter dust storage tank 1 was improved, so that the metallic iron oxidation did not generate heat. Moreover, since the reducing conditions were appropriate, the reaction of the reduced pellets as a product was good, the metallization rate was 82%, the dezincification rate was 96%, and the crush strength was 133 kg, which was not a problem.

Next, the properties of the raw material fine converter dust were almost the same as in Example 1, but the carbon equivalent was 0.43, and the results of treatment with a relatively carbon-deficient blend were shown in Example 3.
In this example, although the granulation process could be carried out without any problems, it was in a state in which it could be used as a product because the carbon required for the reduction of iron oxide and zinc oxide was slightly insufficient. Was 73% and the dezincification rate was 81%, which was a result of a slight lack of reduction.

In Example 4, the lower cone portion 13 of the fine grain converter dust storage tank 1 was heated to 70 ° C. by the electric heater 14, and 97% pure nitrogen was passed through 65 normal cubic meters. is there. In addition, fine grain converter dust storage tank 1
The amount of fine converter dust stockpiles was 95 tons. In this example, although the same fine converter dust as in Example 1 was used, the fine converter dust did not adhere to the cone portion 13, and the fine converter dust 1 was cut out. There was no problem at all. Even when the outside air temperature was 10 ° C. or less, which was severe in dew condensation, the present example was able to perform the treatment without problems.

Next, the processing results of the comparative example using the same equipment as those of Examples 1 to 4 are shown below. Comparative Example 1 is an example in which the water content of the converter dust is low at 3.5% and the metal iron ratio is high at 37%. With this moisture, the reaction between air and metallic iron was vigorous, and heat was generated violently at the stage of the yard treatment before supplying to the fine grain converter dust storage tank 1, and dust was also generated violently. Furthermore, the inside of the fine grain converter dust storage tank 1 also generates a lot of heat, and the temperature inside the tank reaches 330 ° C.,
Had to urgently discharge. Therefore, the subsequent processing was impossible. In Comparative Example 2, the water content is 18%
And an example of a treatment with more water than the scope of the present invention. In this case, the fine converter dust in the fine converter dust storage tank 10 was heavily occupied, and the fine converter dust in the tank could not be discharged. Therefore, even in this example, the subsequent processing could not be performed.

The following is an example of a treatment in which the reaction conditions are outside the scope of the present invention. Comparative Example 3 is 1200 for reaction.
This is an example of a treatment in which the reaction time at a temperature of ℃ or more is as short as 5 minutes. A treatment in which the reaction temperature is 1145 ° C. and lower than 1200 ° C. is shown as Comparative Example 4. As shown in Table 2, the reduction rate and the dezincification rate of the product were low in the treatment under these conditions. Also,
The strength of the reduced pellets, which is a product, was low, and there was a problem in direct use in a blast furnace.

As described above, in the treatment of fine converter dust using the present invention, reduction treatment can be effectively performed, zinc is removed, and reduced iron having high reduction ratio and high strength is produced. We were able to. As a result, a large amount of fine converter dust could be recycled as a blast furnace raw material.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

EFFECT OF THE INVENTION By carrying out the method of the present invention, the fine converter dust obtained by collecting the converter gas containing zinc is effectively reduced by the rotary hearth reduction furnace. ,
It can be dezincified, reduced, and recycled as an iron raw material. Moreover, since zinc and lead can be removed, good quality reduced iron can be produced from fine converter dust.

[Brief description of drawings]

FIG. 1 is an example of a rotary hearth reduction furnace for implementing the present invention and its auxiliary equipment, and is an equipment configuration for treating fine converter dust with a water content of 5 to 16%.

FIG. 2 is a view showing a heating device and an inert gas blowing port of a stock tank of fine grain converter dust for carrying out the present invention.

[Explanation of symbols] 1 Fine converter dust storage tank 2 Other powder storage tanks 3 powder coke storage tank 4 binder storage tank 5 powder conveyor 6 Powder crushing mixing device 7 crushed material conveyor 8 bread granulator 9 Pellet conveyor 10 Rotary hearth reduction furnace 11 Exhaust gas treatment equipment 12 Reduced iron cooling device 13 Cone part 14 Heating device 15 gas supply pipe

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takahashi Politics             1 Kimitsu, Kimitsu-shi Mr. Nippon Steel Corporation             Tsu Steel Works F-term (reference) 4K001 AA08 AA10 AA16 AA19 AA20                       AA30 BA14 CA18 CA23 CA26                       DA06 HA01                 4K012 DE03                 4K070 AB12 AC07 AC34 CA12 CA13                       EA30

Claims (8)

[Claims] 1. The water content of converter dust collected by a non-combustion type dust collector of converter gas and collected as thickener precipitates is 5 to 16% by mass, and the ratio of contained metallic iron is 8 to 10. A characteristic is that after the powder containing iron oxide and the powder containing carbon are mixed in a state of 35% by mass, a molded body is manufactured and the molded body is reduced in a rotary hearth reduction furnace. Recycling method of converter dust for rotary hearth reduction furnace. 2. The converter dust is stored in a storage tank in a state where the water content is 5 to 16 mass% and the ratio of the contained metallic iron is 8 to 35 mass%, and the converter is concerned. 2. The converter dust for a rotary hearth type reduction furnace according to claim 1, wherein the dust is cut out by a quantitative cutting device and mixed with a powder containing iron oxide and a powder containing carbon at a predetermined mixing ratio. Recycling method. 3. A pan-type manufacturing is performed on a converter dust collected by a converter gas non-combustion type dust collector and collected as thickener precipitate, and a mixture of iron oxide-containing powder and carbon-containing powder. Spherical pellets are manufactured using a granulator,
The converter dust recycling method for a rotary hearth type reduction furnace according to claim 1 or 2, wherein the pellets are reduced inside the rotary hearth type reduction furnace. 4. The spherical pellets are manufactured by using a pan-type granulator after mixing and pulverizing the converter dust, the powder containing iron oxide and the powder containing carbon. 3. A method of recycling converter dust to a rotary hearth type reduction furnace according to 3. 5. A plurality of roller dusts are mixed with converter dust collected by a converter gas non-combustion type dust collector and collected as thickener precipitates, and a mixture of iron oxide-containing powder and carbon-containing powder. 3. The converter dust for a rotary hearth type reduction furnace according to claim 1 or 2, characterized in that the briquette compact is produced by having the concave mold of (1) and molding inside the recess. Recycling method. 6. Carbon contained in a mixture obtained by mixing converter dust, powder containing iron oxide and powder containing carbon,
The atomic mole ratio of iron, manganese, nickel, chromium, lead, and zinc oxide to oxygen is in the range of 0.5 to 1.5, and the gas temperature at the time of reduction is 1200 ° C or higher. The method of recycling converter dust to a rotary hearth type reduction furnace according to any one of claims 1 to 5, wherein the molded body is present for 6 minutes or more. 7. A thickener collected by a non-combustion type dust collector of converter gas in a state of containing water in an amount of 5 to 16% by mass and in a state of containing metallic iron in an amount of 8 to 35% by mass. The converter dust collected as a precipitate is stored in a storage tank in which the lower cone portion is heated and an inert gas mixed with oxygen concentration of 5% or less is flowing inside. The method for recycling converter dust to a rotary hearth type reduction furnace according to claim 2, wherein the converter dust is cut out with a feeder and mixed with other powder. 8. The nitrogen having an oxygen concentration of 5% or less mixed as impurities of 0.5 normal cubic meters / hour or more per ton of stored converter dust per hour is flown. Converter dust recycling method for rotary hearth reduction furnace.