JP3712944B2 - Recycling method of converter generated dust - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dust treatment method for effectively reusing dust having a high content of metallic iron generated during converter blowing, in a converter process.
[0002]
[Prior art]
Conventionally, iron powder-containing dust generated at the time of converter blowing is wet-collected and collected by a coarse-grain separator in, for example, an iron powder-containing dust having a particle size of 60 μm or more and an iron powder-containing dust having a particle size of less than 60 μm. It was. Among these, the dust containing iron powder of less than 60 μm was returned to the sintering-blast furnace process and reused. However, due to the problems of zinc regulation in the blast furnace operation and dioxin generation in the sintering process, the converter was mainly used. It is used as a coolant and iron source in the process.
In order to reuse the iron powder-containing dust of less than 60 μm separated and recovered by the coarse-grain separator as a coolant or iron source in the converter process, the recovered iron powder-containing dust of less than 60 μm is introduced into the precipitation tank and precipitated. A slurry having a water content of about 70% by weight is formed, and this is dehydrated to a water content of 20-30% by weight using a filter press to form a plate cake. Subsequently, since the obtained plate cakes are sun-dried in a piled state, drying requires 10 to 14 days, and metal iron is oxidized by oxygen in the air at the time of sun-drying, so heat of oxidation This oxidation heat promotes the drying of the plate cake and at the same time the oxidation proceeds, and the content of metallic iron in the iron powder-containing dust becomes 20% by weight or less. In addition, since the piled-up cake is appropriately piled up during drying, the plate-like cake has collapsed into powder after drying and is charged into the converter in this state. However, it is sucked by the dust collector, and the yield of charging the converter becomes low. Therefore, the iron powder-containing dust that has been pulverized is once pulverized, mixed with water and a binder, formed into briquettes with a briquette machine, and dried until the moisture content of the briquettes is 3% by weight or less. The dried briquettes are transported to the converter factory, temporarily stocked on the furnace hanger, and charged into the converter as a coolant and iron source at the required time during blowing. Here, the reason why the moisture content of the briquette is set to 3% by weight or less is to prevent a steam explosion from occurring when the briquette is charged into the converter during blowing.
[0003]
[Problems to be solved by the invention]
However, the reuse as a coolant in the conventional converter process forms briquettes from the viewpoint of safety in order to obtain a function as a coolant and to prevent spontaneous ignition of briquettes during storage. The metallic iron content in the iron powder-containing dust is regulated to 20% by weight or less. For this reason, although it is iron dust containing dust with high metal iron content originally, when recycled to a converter process, there exists a problem that it is not utilized effectively as metal iron resources. Moreover, since the collected iron powder-containing dust of less than 60 μm becomes a plate-like cake by dehydration treatment by a filter press, it takes 10 to 14 days for drying, and a large drying work area is required for that purpose. There is a problem. Furthermore, since the plate cake after drying has collapsed into a granular form, it is necessary to make it into a molded body such as briquette to be recycled to the converter. In order to charge the converter, there have been incidental processes such as strictly controlling the water content of briquettes, and management problems resulting therefrom.
The present invention has been made in view of such circumstances, and it is possible to recycle the converter-generated dust to the converter as metallic iron to improve the yield of the converter process, and to reduce the converter process dust with a short processing time. The purpose is to provide a recycling method.
[0004]
[Means for Solving the Problems]
The method for recycling converter generated dust according to the present invention in accordance with the above object is a method of collecting iron powder-containing dust generated at the time of converter blowing and performing a dehydration process using a filter press to obtain metallic iron in the iron powder-containing dust. And a recycling process step of drying and reducing to a converter step.
Iron powder-containing dust generated during converter blowing is higher in metal iron content than dust generated in other production processes. By reducing it to the furnace process, it becomes possible to reuse the iron powder-containing dust as an iron source in the converter process.
[0005]
In the method for recycling converter generated dust according to the present invention, the recycling process step.IsThe first step of wet recovery of the iron powder-containing dust generated during converter blowing, and the iron powder-containing dust having a large particle size that is easy to settle and separate from the wet recovered iron powder-containing dust by a coarse-grain separator The second step of removing the remaining iron powder-containing dust in a settling tank to form a slurry, the third step of pressing the slurry with the filter press to form a plate cake, and the filter press A fourth step of holding the shape of the plate-like cake and discharging it to a drying container, a fifth step of drying the cake in the drying container, and discharging the cake after drying from the drying container to a converter And the sixth step of chargingHave.
[0006]
The iron powder-containing dust generated at the time of blowing in the converter has an average particle size of about 100 μm and high-grained coarse dust (metal iron content of about 75 to 85% by weight) and an average due to the difference in generation mechanism. The iron powder-containing dust recovered by a wet dust collector is divided into fine dust (metal iron content of about 50 to 65% by weight) with a particle size of about 1 μm and a low metal iron content compared to coarse dust. It is in a mixed state of the coarse dust and fine dust.
Coarse dust and fine dust collected by a wet dust collector and dispersed in water are sent to the coarse separator, and the iron powder containing dust with a large particle size that is easily settled and separated by the coarse separator is removed. Removed. The removed iron powder-containing dust having a large particle diameter is directly recovered from water. Further, the water in which the remaining iron powder-containing dust is dispersed is sent to a precipitation tank, where the iron powder-containing dust is allowed to settle, and a portion of the iron powder-containing dust precipitation layer (hereinafter referred to as slurry) and supernatant. Separate into water. The slurry is transported to a slurry tank by a transport pump and stored while stirring.
[0007]
The slurry stored in the slurry tank is 40 to 20% by weight of iron powder-containing dust, which is a solid phase component, and the remaining 60 to 80% by weight is water, so it is difficult to recover in this state. Therefore, for example, the water is squeezed with a filter press to form a plate-like cake having a water content of about 15 to 20% by weight. By reducing the moisture content of the cake to about 15 to 20% by weight, the strength of the cake is greatly improved and handling becomes easy. For this reason, it becomes possible to discharge | emit the plate-shaped cake formed with the filter press, hold | maintaining a shape, and to accommodate in a drying container.
By storing the cake in the shape of a plate in the drying container, both the heat transfer area and the evaporation area of moisture can be secured at the time of drying, and it becomes possible to dry the cake-like thing in a short time. . Moreover, since it has a plate shape, direct contact between fine individual iron powder-containing dust and air can be cut off, and drying can be performed while suppressing oxidation of iron powder-containing dust by oxygen in the air. .
Since the cake is dried in a plate-like state, the cake can be easily discharged from the drying container, and the fine dust can be prevented from being oxidized during storage. Furthermore, when the cake is charged into the converter, the cake can be easily transported and charged into the converter.
[0008]
In the converter processing dust recycling method according to the present invention, in the second step, the iron powder-containing dust removed by the coarse particle separator can have a minimum particle size of 40 to 80 μm.
When the minimum particle size of the iron powder-containing dust removed by the coarse separator, that is, the classified particle size is set in the range of 40 to 80 μm, the remaining iron powder-containing dust removed by the coarse separator (iron having a particle size less than the classified particle size). Since the powder-containing dust is composed of iron powder-containing dust having a relatively small particle size, the stability of the slurry in the slurry tank (that the slurry does not separate into iron powder-containing dust and water) is improved. For this reason, the stability of the slurry can be sufficiently ensured only by stirring the slurry in the slurry tank at a relatively low rotational speed of, for example, 20 to 60 rotations / minute.
Further, in the second step, the minimum particle size of the iron powder-containing dust removed by the coarse particle separator can be set to 70 to 130 μm.
In general, as the particle size of the iron powder-containing dust increases, the specific surface area decreases, and the area of metallic iron per unit weight that comes into contact with oxygen in the air decreases. For this reason, oxidation of metallic iron in iron powder containing dust at the time of drying can be suppressed, and iron iron containing dust with large metal iron content is obtained, so that iron powder containing dust with a large particle size is used. Is advantageous. However, the stability of the slurry decreases as the particle size of the iron powder-containing dust increases. Therefore, in order to achieve both of obtaining dry iron powder-containing dust having a high metal iron content and ensuring the stability of the slurry by suppressing oxidation of the iron powder-containing dust during drying as much as possible, It was confirmed from experiments that the minimum particle size of the iron powder-containing dust removed by the particle separator, that is, the classified particle size, should be set in the range of 70 to 130 μm. Since the remaining iron powder-containing dust (iron powder-containing dust less than the classified particle size) removed by the coarse particle separator contains iron powder-containing dust having a relatively large particle size, the slurry It is necessary to ensure the stability of the slurry by stirring the slurry in the tank, for example, at a rotation speed of 40 to 80 rpm.
[0009]
In the method for recycling converter generated dust according to the present invention, it is preferable to add a binder that improves the strength of the cake after drying to the slurry in the second step.
In general, a binder has both a hydrophobic part and a hydrophilic part in the molecular structure. Therefore, when a binder is added to a slurry of iron powder-containing dust, the hydrophobic part of the binder is reduced in the iron powder-containing dust. Adsorb to the surface. Therefore, when the slurry added with the binder is pressed with a filter press to form a cake, a bond based on the entanglement of the binders adsorbed on the iron powder-containing dust surface is formed between the iron powder-containing dusts. Since the binding force based on the entanglement between the binders gradually increases as the moisture in the cake decreases, the strength of the cake increases as the drying of the cake proceeds.
[0010]
In the method for recycling converter generated dust according to the present invention, it is preferable that the cake is dried in a non-oxidizing atmosphere in the fifth step.
Since oxidation of iron powder-containing dust does not occur during drying in a non-oxidizing atmosphere, drying can be performed while maintaining a high metal iron content. Further, the cake can be dried at a high temperature by raising the drying temperature, and the drying time of the cake can be shortened.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
FIG. 1 is a process diagram of the converter generated dust recycling method according to the first embodiment of the present invention, and FIG. 2 is applied to the converter generated dust recycling method according to the first embodiment. FIG. 3 is a process diagram of a method for recycling converter-generated dust according to the second embodiment of the present invention.
As shown in FIG. 1, the recycling process method for converter generated dust according to the first embodiment of the present invention is a first step of performing wet recovery of iron powder-containing dust, and is easy to settle and separate from iron powder-containing dust. A second step of removing the iron powder-containing dust having a particle size by a coarse separator and forming a slurry of the remaining iron powder-containing dust, and a third step of forming a plate cake by dehydration from the slurry with a filter press, A recycling process step including a fourth step of discharging the plate cake into the drying container, a fifth step of drying the cake in the drying container, and a sixth step of discharging the cake from the drying container and recycling it to the converter process. have. Hereinafter, it demonstrates in detail for every process.
[0012]
First step
The iron powder-containing dust generated during the blowing of the converter has coarse particle dust (metal iron content of about 75 to 85% by weight) and an average particle size of about 1 μm due to the difference in the generation mechanism. Fine dust (metal iron content of about 50 to 65% by weight). The generated iron powder-containing dust, together with the gas such as converter gas generated at the same time, is wet via the connecting pipe that connects the exhaust port and the inlet of the wet dust collector from the exhaust port provided at the top of the converter furnace. It flows into the dust collector. In the wet dust collector, for example, water is sprayed in the form of a mist from the top, the iron powder-containing dust and gas are cooled by the sprayed water, and at the same time, the iron powder-containing dust is collected in the water and the iron powder-containing dust is collected. And gas are separated. The iron powder-containing dust collected in the sprayed water is collected together with water from a drain outlet provided at the bottom of the wet dust collector. Further, the separated gas is sent to the converter gas collector from an exhaust port provided in the wet dust collector, where the converter gas is recovered.
[0013]
Second step
The iron powder-containing dust recovered in a dispersed state in water is transported to a cyclone that is an example of a coarse separator. When the classified particle size of the cyclone is adjusted to remove the iron powder-containing dust whose minimum particle size d is in the range of 40 to 80 μm, the remainder becomes iron powder-containing dust having a particle size of less than d and is dispersed in water. Yes. Therefore, this dispersed water is transported to a sedimentation tank and stored. In the settling tank, the dust containing iron powder settles to the bottom of the settling tank as the storage time elapses, and is separated into slurry (precipitate layer portion) and supernatant water. The produced slurry is transported to a slurry tank by a transport pump. For example, a binder such as sodium silicate or lignin is added at a ratio of about 2 to 5% by weight with respect to the weight of the iron powder-containing dust, and mixed thoroughly. Adjust to slurry for filter press. Since the slurry stored in the slurry tank gradually settles with the passage of the storage time, for example, the iron powder-containing dust is constantly stirred at a stirring speed of about 40 revolutions / minute so that the iron powder-containing dust is at the bottom of the slurry tank. To prevent precipitation.
[0014]
Third step
The slurry for filter press stored in the slurry tank is supplied to the filter press by a slurry supply pump. As shown in FIG. 2, the filter press has a slurry pressing unit 11 having a number of pressing chambers 12 that are separated by a filter cloth 13 and press the slurry to form a cake 14, and a high pressure that presses the slurry into the slurry pressing unit 11. And a pump part. For example, the pressing pressure is 40-60 kg / cm² When the slurry is squeezed to form a plate-like cake 14 (for example, a length of 1200 mm, a width of 1200 mm, and a thickness of about 30 mm), the moisture content of the cake 14 obtained is about 15 to 20% by weight. It can be. For this reason, the intensity | strength for maintaining sufficient shape retention property to the cake 14 can be provided.
[0015]
Fourth step
The slurry pressing part 11 of the filter press is opened, and the plate-like cakes 14 formed one by one from each pressing chamber 12 are discharged into the drying container 21. The reason why the cake 14 is discharged into the drying container 21 is to allow the drying operation to be performed immediately after the discharge. When the pressing chamber 12 is opened, the formed cake 14 naturally falls downward while sliding on the filter cloth 13. Therefore, if a drying container 21 having an open top is installed under the slurry pressing portion 11 of the filter press, the cake 14 Can be directly stored in the drying container 21. At this time, in order to prevent the cake 14 from being damaged or deformed and to store the cake 14 in the drying container 21, for example, a cake as shown in FIG. 2 between the slurry pressing part 11 of the filter press and the drying container 21. It is preferable to install the carry-out device 10.
[0016]
As shown in FIG. 2, the cake carry-out device 10 determines the drop position of the cake 14 that has fallen naturally while sliding on the filter cloth 13 when the pressing chamber 12 provided in the slurry pressing unit 11 is opened. Guide section 15 to be guided, cake holding section 16 attached to the lower end of guide section 15 to restrain and drop cake 14 from both sides, guide section 15 and cake holding section 16 are loaded and moved in the stacking direction of compression chamber 12 It has a possible carriage 17 and a set of rails 18 provided below the slurry pressing part 11 and on which the carriage 17 travels.
[0017]
The guide portion 15 that guides the falling direction of the cake 14 that has fallen naturally is, for example, a cake outlet of the compression chamber 12 in which two upper plates (for example, a length of 500 mm, a width of 1500 mm, and a thickness of about 2 mm) are opened at the upper end side. It can comprise by arrange | positioning facing so that it may have the width | variety equivalent to the width B of this, and a lower end side may have a width | variety equivalent to the thickness H of the cake 14. FIG. As a result, the cake 14 that naturally falls from the opened compression chamber 12 and enters the guide portion 15 is gradually corrected in its dropping position when passing between the two stainless steel plates, and the tip of the cake 14 is securely held by the cake. Entering the part 16 is guaranteed.
[0018]
The cake holding part 16 is, for example, a stainless steel plate 20 (for example, a length of 1000 mm, a width of 1500 mm, and a thickness of 2 mm) provided with a porous rubber 19 made of polyurethane rubber having a thickness of about 10 to 20 mm on one surface. With the surface on which the porous rubber 19 is provided as the inner surface side, they are arranged to face each other so as to have a width that is smaller by about 5 to 10 mm than the thickness H of the cake. The cake 14 whose drop position has been corrected by the guide portion 15 and entered the cake holding portion 16 passes between the stainless steel plates 20 while compressing the porous rubber 19 on the inner surface side toward the stainless steel plate 20. At this time, the cake 14 receives a reaction force equivalent to the force of compressing the porous rubber 19 from the porous rubber 19 on both sides, and a frictional force is generated between the cake 14 and the porous rubber 19 by this reaction force. .
[0019]
Due to this frictional force, the natural falling speed of the cake 14 is reduced, and the drop impact force when the cake 14 reaches the bottom of the drying container 21 is reduced to prevent the cake 14 from being damaged or deformed. In addition, a partition plate 22 is provided inside the drying container 21 so that the cakes 14 are stored one by one with a predetermined interval (for example, about 1 to 2 times the cake thickness). As a result, it is possible to prevent contact between the cakes 14 by drying the cakes 14 performed in the next step, and to secure a heat transfer area for receiving heat and an evaporation area for evaporating water on the surface of the cake 14 as much as possible. it can. Moreover, since the guide part 15 and the cake holding | maintenance part 16 are loaded on the trolley | bogie 17 which travels on the rail 18 provided in the lamination direction of the pressing room 12 under the slurry pressing part 11, the pressing room 12 opens in order. Correspondingly, the position of the carriage 17 can be moved to carry out the cake 14. For this reason, all the cakes 14 can be discharged into the drying container 21 without breakage or deformation.
[0020]
5th process
The drying container 21 in which the cake 14 is stored is transported to a drying work place using a transporter such as a lift car and dried. Drying is performed, for example, by covering the top of the drying container 21 and supplying warm air from an air supply port provided on the lower side surface of the drying container 21 and exhausting air from an exhaust port provided on the lid. Since drying is performed while preventing oxidation of metallic iron in the iron powder-containing dust, it is preferably performed in a non-oxidizing atmosphere. For example, nitrogen gas heated to 150 to 200 ° C. is used. For this reason, the exhaust gas (nitrogen gas and water vapor) exhausted from the drying container 21 is supplied to a moisture removing device to separate the moisture into only nitrogen gas, heated to 150 to 200 ° C., and again into the drying container 21. A circulating drying method is preferred.
[0021]
When the cake 14 is dried by using hot air at high temperature, the surface layer portion of the cake 14 is rapidly dried to form a dense dry layer. For this reason, when the water inside becomes hard to evaporate and is accumulated as water vapor inside the cake 14, the explosion phenomenon occurs when the pressure of the water vapor becomes higher than the strength of the dry layer of the cake surface layer. Therefore, the temperature of the hot air used for drying is preferably 200 ° C. or less at which explosion does not occur. Moreover, since the drying time will become long when the temperature of warm air will be less than 150 degreeC, it is unpreferable.
For example, when drying the cake 14 by supplying hot air of 200 ° C. into the drying container 21, the moisture content of the cake 14 that can be charged into the converter is, for example, 10% by weight or less, preferably 8% by weight. In order to dry the cake 14 until it becomes this state, the drying time of 60 minutes or more is required. On the other hand, the cycle time when the cake 14 is formed by the filter press, that is, the time from when the slurry is injected into the pressing chamber 12 until the discharge of the cake 14 is completed is about 60 minutes. For this reason, in order to execute the filter press operation and the drying operation in a coordinated manner without waste, it is necessary to prepare two drying containers 21 in the present embodiment.
[0022]
6th process
When the drying of the cake 14 is finished in the drying container 21, the lid attached to the upper part of the drying container 21 is removed, and the cake 14 is opened, for example, by opening the openable / closable discharge door 23 provided at the lower part of the drying container 21. It discharges in the conveyance container arrange | positioned under the drying container 21. FIG. At this time, although the cake 14 falls spontaneously, it breaks, but since the binder is added, it does not easily collapse into a granular form and becomes a large lump. The dried cake 14 discharged into the transport container is sent to a scrap yard provided in the vicinity of the converter plant by means of transportation such as a dump truck, for example, and temporarily stored. It is loaded on the scrap chute using the cargo handling means, transported to the converter, and charged.
[0023]
Since the cake 14 is charged into the converter by scrap chute at the same timing as the scrap, it is performed when the inside of the converter before the hot metal charging is in a relatively high temperature state. For this reason, since the moisture in the cake 14 evaporates in a short time, if the moisture content of the cake 14 is 10% by weight or less, the cake 14 can be charged into the converter even if the moisture content of the cake 14 slightly varies. It is. Therefore, the work load for the dehydration treatment and dry storage of the cake 14 can be greatly reduced as compared with the case where the cake 14 is put into the molten steel at the time of converter refining. Since the dried cake 14 is gradually oxidized during storage in the scrap yard, the residence time in the scrap yard needs to be as short as possible. For that purpose, it is necessary to plan the recycling process of the converter generated dust in accordance with the operation process of the converter, but in this embodiment, the process time from the collection of the dust to the charging of the converter is 2 to 4 hours. Therefore, it is possible to plan the recycling process sufficiently corresponding to the operation process of the converter.
[0024]
As shown in FIG. 3, the recycling process method for converter generated dust according to the second embodiment of the present invention is a first step for wet recovery of iron powder-containing dust, and is easy to settle and separate from iron powder-containing dust. A second step of removing the iron powder-containing dust with a coarse particle separator and forming a slurry of the remaining iron powder-containing dust, a third step of forming a plate cake from the slurry with a filter press, and a plate shape It has the 4th process which discharges a cake to a drying container, the 5th process which dries a cake in a drying container, and the 6th process which discharges a cake from a drying container and recycles to a converter process. Here, since the other steps except the second step for forming the slurry are the same as those in the first embodiment, a different second step will be described.
[0025]
The iron powder-containing dust recovered in a dispersed state in water is transported to a cyclone that is an example of a coarse separator. When the classified particle size of the cyclone is adjusted to remove the iron powder-containing dust whose minimum particle size d 'is in the range of 70 to 130 μm, the remainder becomes iron powder-containing dust with a particle size of less than d ′ and is dispersed in water. are doing. Therefore, this dispersed water is transported to a sedimentation tank and stored. In the settling tank, the dust containing iron powder settles to the bottom of the settling tank as the storage time elapses, and is separated into slurry (precipitate layer portion) and supernatant water. The produced slurry is transported to a slurry tank by a transport pump. For example, a binder such as sodium silicate or lignin is added at a ratio of about 2 to 5% by weight with respect to the weight of the iron powder-containing dust, and mixed thoroughly. Adjust to slurry for filter press. Since the slurry stored in the slurry tank gradually settles with the passage of the storage time, for example, the iron powder-containing dust is constantly stirred at a stirring speed of about 60 revolutions / minute so that the iron powder-containing dust is at the bottom of the slurry tank. To prevent precipitation.
[0026]
The ratio of the coarse-grained dust and the fine-grained dust generated at the time of converter blowing is a ratio of the fine-grained dust 2 to 3 with respect to the coarse-grained dust 1, for example, with respect to 5 kg of coarse-grained dust per 1 t of converter steel. The fine dust is 10-15 kg. Since the average diameter of the coarse dust is about 100 μm, adjusting the cyclone classification diameter so that the iron powder-containing dust having a particle size of 100 μm or less is recovered will substantially reduce the coarse particle dust. Half will be collected, and the weight of the collected iron powder-containing dust having a particle size of 100 μm or less is 12.5 to 17.5 kg per 1 t of converter steel. In the case of a 300t converter, the amount of scrap used is about 10% by weight of the converter capacity, so it is 30t. Moreover, the weight of the iron powder containing dust which generate | occur | produces from this converter and is collect | recovered as an iron powder containing dust which has a particle size of 100 micrometers or less becomes 3.7-5.2t, The metallic iron contained in this iron powder containing dust The weight of is 2.7 to 3.8 t. For this reason, when the iron powder containing dust which has a particle size of 100 micrometers or less is recycled to a converter, the amount of scraps can be reduced 3 to 4t.
[0027]
As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment, For example, in order to prevent the oxidation in drying of iron powder containing dust, it heated to drying of the cake. Nitrogen gas is used, but if the oxygen content is 0.5% by volume or less, the oxidation of iron powder-containing dust can be suppressed, so the mixture of exhaust gas and nitrogen gas discharged from various industrial furnaces in the steelworks factory It is also possible to use gas or exhaust gas alone. Moreover, although the cake after drying was discharged | emitted to the conveyance container, it is also possible to discharge | emit directly to a scrap chute.
[0028]
【The invention's effect】
Claim1-5In the described method for recycling converter generated dust, the iron powder-containing dust generated during converter blowing is wet collected and dehydrated by a filter press to suppress oxidation of metallic iron in the iron powder-containing dust. Since it has a recycling process step of drying and reducing to the converter step, it is possible to improve the yield of the converter.
[0029]
In particular,thisIn the recycling method, the recycling process includes a first step in which iron powder-containing dust generated during converter blowing is wet-recovered, and iron powder having a large particle size that is easy to settle and separate from the wet-collected iron powder-containing dust. The second step of removing the contained dust with a coarse-grain separator and allowing the remaining iron powder-containing dust to settle in a sedimentation tank to form a slurry, and the third step of pressing the slurry with a filter press to form a plate-like cake A fourth step of holding the shape of the plate cake from the filter press and discharging it to the drying container, a fifth step of drying the cake in the drying container, and discharging the cake after drying from the drying container to the converter Since the iron powder-containing dust is not formed into briquettes or the like when recycled to the converter, the iron powder-containing dust can be reduced at a low cost and the processing time can be shortened. It can be recycled to the converter.
[0030]
Claim2In the recycle processing method of converter dust generated in the description, since the minimum particle size of the iron powder-containing dust removed by the coarse separator in the second step is 70 to 130 μm, oxidation of the iron powder-containing dust during cake drying is performed. Can be suppressed, and an iron powder-containing dust having a high metal iron content can be obtained. For this reason, it is possible to perform stable operation of the converter even if the scrap amount varies.
Claim3In the converter processing dust recycling method described in the second step, since the minimum particle size of the iron powder-containing dust removed by the coarse particle separator is 40 to 80 μm in the second step, the stability of the iron powder-containing dust slurry is improved. It is possible to secure enough. For this reason, it becomes possible to divert the existing iron powder containing dust recovery device to the recycling process of converter generated dust.
[0031]
Claim4In the converter processing dust recycling method described above, since the binder for improving the strength of the cake after drying is added to the slurry of the second step, the strength of the cake after drying can be improved, and the breakage can be suppressed. Therefore, the rate of pulverization during transportation and storage can be reduced, and recycling to the converter becomes easy. In addition, since the dried cake is not easily damaged, for example, it becomes possible to recycle it into the converter at the same time as scrap using a scrap chute. It can be charged directly into the inside, and the process time from dust recovery to converter charging (recycling) can be greatly reduced. For this reason, it is possible to drastically reduce work costs for drying the cake and transporting and storing the cake after drying. For example, what conventionally required 10 to 14 days from the collection of dust to the charging of the converter can be shortened to 2 to 4 hours in the present invention.
[0032]
Claim5In the converter processing dust recycling method described above, the cake is dried in a non-oxidizing atmosphere in the fifth step, so that oxidation of dust during processing can be prevented and converter generating dust having a high metal iron content. Can be stably recycled in the converter process. As a result, the converter can be operated with a stable yield.
For example, when dust in a fine-grained area is recycled to a converter, the metal iron content in the iron powder-containing dust to be recycled is conventionally 10 to 20% by weight, but in the present invention, it is about 50 to 60% by weight. Can be improved. Therefore, in the case of a 300 t converter, if the scrap ratio is 10% by weight, the scrap amount is 30 t. On the other hand, the generation rate of fine dust in the converter generated dust is about 15 kg per 1 ton of molten steel, and the generated amount is 4.5 t. Among these, since metal iron is about 2.2 to 2.7 t, the scrap amount can be reduced by about 7 to 10% by weight. Further, when half of the generated coarse dust is recycled together with the fine dust, the scrap amount can be reduced by about 10 to 13% by weight.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a process diagram of a method for recycling converter generated dust according to a first embodiment of the present invention.
FIG. 2 is a conceptual diagram of a cake carry-out device applied to a method for recycling the dust generated in the converter.
FIG. 3 is a process diagram of a converter processing dust recycling method according to a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10: Cake carrying-out apparatus, 11: Slurry pressing part, 12: Pressing chamber, 13: Filter cloth, 14: Cake, 15: Guide part, 16: Cake holding part, 17: Carriage, 18: Rail, 19: Porous rubber 20: Stainless steel plate, 21: Drying container, 22: Partition plate, 23: Discharge door

Claims (5)

A recycling process that recovers the iron powder-containing dust generated at the time of converter blowing by a wet process, dehydrates it with a filter press, suppresses the oxidation of metallic iron in the iron powder-containing dust, and dries it back to the converter process. A method for recycling converter generated dust , comprising:
A first step in which the recycling treatment step wet-collects the iron powder-containing dust generated during converter blowing,
The iron powder-containing dust having a large particle size that is easily settled and separated from the iron powder-containing dust collected by the wet process is removed by a coarse separator, and the remaining iron powder-containing dust is settled in a sedimentation tank to form a slurry. Process,
A third step of pressing the slurry with the filter press to form a plate cake;
A fourth step of maintaining the shape of the plate-like cake from the filter press and discharging it to a drying container;
A fifth step of drying the cake in the drying container;
And a sixth step of discharging the cake after drying from the drying container and charging the cake into a converter. 2. The converter according to claim 1 , wherein a minimum particle size of the iron powder-containing dust removed by the coarse-grain separator in the second step is 70 to 130 μm. Recycling method of generated dust. 2. The converter according to claim 1 , wherein a minimum particle size of the iron powder-containing dust removed by the coarse particle separator in the second step is 40 to 80 μm. Recycling method of generated dust. The recycle processing method of converter generated dust according to any one of claims 1 to 3 , wherein a binder that improves the strength of the cake after drying is added to the slurry in the second step. Recycling method of converter generated dust. The method for recycling converter generated dust according to any one of claims 1 to 4 , wherein the cake is dried in a non-oxidizing atmosphere in the fifth step. Recycling method.

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