JP2007002283A - Method and equipment for treating steel making dust - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating steel making dust by which the oxidation of metal iron contained in the steel making dust can be prevented and energy consumption attendant upon the drying of dust collected by wet process can be reduced and further the transportation and handling of the steel making dust and the dust collected by wet process accompanied with recycling can be facilitated. <P>SOLUTION: This method is the one for treating the steel making dust discharged in a step of removing impurities from pig iron. The method comprises the following steps: a drying step where the dust collected by wet process containing the steel making dust and having ≤30 mass% water content is extruded into a drying flow passage through which a combustion gas stream of 400 to 800°C is made to flow to evaporate the water in the dust collected by wet process, and the steel making dust is made to flow into the combustion gas stream; and a sorting and recovering step where the steel making dust is sorted into dust with high metal-iron content and dust with low metal-iron content having metal-iron content lower than that of the dust with high metal-iron content and recovered using a sorting and recovering apparatus disposed on the down stream side of the drying flow passage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a steelmaking dust processing method and a steelmaking dust processing apparatus, and more particularly to a steelmaking dust processing method and apparatus capable of minimizing energy consumption.

In a general steelmaking process, pig iron discharged from a blast furnace contains a large amount of carbon, and therefore it is necessary to perform a decarburization process in the converter to remove the carbon content. Specifically, pig iron discharged from the blast furnace is poured into the converter, and in some cases, iron scrap is previously charged, and then oxygen is blown into the pig iron to decarburize it.
By the way, in the oxygen blowing process of the converter, the steelmaking dust is discharged together with the exhaust gas. This steelmaking dust is a collection of fine particles containing about 40 mass% to about 50 mass% of metallic iron, and the balance of iron oxide and other impurities having an average particle diameter of about several μm to several tens of μm. It is a valuable resource in terms of inclusion. Then, the processing method for recycling this steelmaking dust to a steelmaking process is examined conventionally.

As an example of a conventional steelmaking dust treatment method, steelmaking dust collected by a wet dust collector is stored in water, and then dehydrated by a pressing operation to obtain a dehydrated cake having a water content of about 20% by mass. A method is known in which a metal iron component is oxidized by exposure to iron oxide, and then solidified by mixing a binder, and this solid content is put into a converter.
However, this treatment method has a problem that energy loss occurs in that iron reduced by the blast furnace is returned to iron oxide. Further, there is a problem that the metallic iron contained in the solid matter may ignite after molding, and the management of the solid matter becomes complicated.

As another example of a conventional method for treating steelmaking dust, a method is also known in which steelmaking dust is charged into a sintering machine to form a sintered body, and this sintered body is recharged into a blast furnace.
However, zinc contained in scrap iron is concentrated as zinc oxide in the sintered body, and zinc oxide may adversely affect the operation of the blast furnace. Therefore, there is a problem that even if iron sintered by a sintering machine is recycled, the amount is limited.

Moreover, considerable energy is required to dry the recovered steelmaking dust in a slurry state. Patent Document 1 (Japanese Patent No. 3251609) discloses a technique in which mechanical dehydration is performed until the viscosity of the slurry becomes 60 poise or less, and then the slurry is sprayed into a high-temperature combustion gas atmosphere to evaporate moisture. Yes.
Japanese Patent No. 3251609

  However, in the method described in Patent Document 1, it is necessary to manage the viscosity and temperature of the slurry so that the slurry after mechanical dehydration is always sprayed under certain conditions, which is troublesome. In addition, in order to spray the slurry, it is necessary to contain a lot of water in the slurry. In this case, it is necessary to efficiently evaporate the water by setting the spray atmosphere of the slurry to a high temperature, which increases the energy consumption of drying by spraying. There was a problem.

  The present invention has been made in view of the above circumstances, and prevents oxidation of metallic iron contained in steelmaking dust to prevent energy loss, and also reduces energy consumption accompanying drying of the dehydrated cake, It is an object of the present invention to provide a steelmaking dust processing method and a steelmaking dust processing apparatus that make it possible to easily transport and handle steelmaking dust and dehydrated cake accompanying recycling.

In order to achieve the above object, the present invention employs the following configuration.
The method for treating steelmaking dust according to the present invention is a method for treating steelmaking dust discharged in a pig iron impurity removal step, wherein the steelmaking dust is placed in a drying flow path through which a combustion gas flow of 400 ° C or higher and 800 ° C or lower flows. A drying step of extruding wet dust collection dust having a water content of 30% by mass or less containing water to evaporate water in the wet dust collection dust and flowing the steelmaking dust into the combustion gas stream; and the drying flow path The steelmaking dust is separated and recovered into a metal iron high-content dust and a metal iron low-content dust whose content of metal iron is lower than that of the metal iron high-content dust. A separate collection step.
Moreover, in the processing method of the steelmaking dust of this invention, the metal iron content rate of the said metal iron high content dust is 30 mass% or more, and the metal iron content rate of the said metal iron low content dust is less than 30 mass%. Is preferred.
In the steelmaking dust treatment method of the present invention, as the separation and recovery device, one or more cyclones connected to the downstream side of the drying flow path, and a bag filter connected to the downstream side of the cyclone. It is preferable to use it.
In the steelmaking dust treatment method of the present invention, it is preferable to return either one or both of the high metal iron content dust and the low metal iron content dust recovered in the fractional recovery step to molten pig iron.
In the steelmaking dust treatment method of the present invention, nitrogen gas having a temperature of 400 ° C. or higher and 800 ° C. or lower may be used instead of the combustion gas.

Next, the steelmaking dust processing apparatus of the present invention is a processing apparatus for processing the steelmaking dust discharged in the pig iron impurity removal step, and a drying flow path through which a combustion gas flow of 400 ° C. or higher and 800 ° C. or lower flows. A drying device provided with at least an extrusion mechanism for extruding wet dust collecting moisture containing 30% by mass or less of the steelmaking dust into the drying channel; and disposed on the downstream side of the drying channel, The steelmaking dust is provided with a metal iron high-content dust and a fraction collection device for separating and collecting the metal iron high-content dust and the metal iron low-content dust lower than the metal iron high-content dust. To do.
Moreover, in the steelmaking dust processing apparatus of this invention, the metal iron content rate of the said metal iron high content dust is 30 mass% or more, and the metal iron content rate of the said metal iron low content dust is less than 30 mass%. Is preferred.

  The wet dust collection dust in the present invention includes granular dust containing steelmaking dust having an average particle diameter of 20 μm or more and dehydrated cake containing steelmaking dust having an average particle diameter of less than 20 μm. Granular dust is obtained by collecting steelmaking dust in water and then allowing it to settle naturally in water. Further, the dehydrated cake is a cake obtained after dehydrating the supernatant liquid after sedimentation of granular dust and removing water to some extent. Furthermore, a part of the granular dust may contain a steelmaking dust having an average particle diameter of less than 20 μm, and a part of the dehydrated cake may contain a steelmaking dust having an average particle diameter of 20 μm or more.

In the present invention, by extruding the wet dust collection dust into the drying flow path and evaporating the water in the wet dust collection dust, the steelmaking dust that has been solidified by the water until then loses its binding force and becomes dusty. The Next, the steelmaking dust is transported in the form of dust to a separation and recovery device disposed on the downstream side of the drying flow path by the combustion gas flow, and is separately collected by the separation and recovery device.
The combustion gas flow used for drying the wet dust collection dust is a gas obtained by burning a fuel such as COG with air, and most of the gas components are inert gas composed of carbon dioxide and nitrogen. Therefore, even when the steelmaking dust is exposed to the combustion gas, the metal iron contained in the steelmaking dust is less likely to be oxidized, and the physical properties of the steelmaking dust hardly change before and after drying. Therefore, it becomes possible to return the steelmaking dust once made into wet dust collection dust to the original dust form again in the drying flow path.
The steelmaking dust thus returned to the dust form is classified for each average particle diameter by the separation and recovery device. A classification component having a relatively large average particle size contains a large amount of metallic iron, while a classification component having a relatively small average particle size contains a large amount of iron oxide and a small amount of metallic iron. Therefore, by separating and collecting steelmaking dust according to the content of metallic iron, the separated steelmaking dust can be returned under optimum conditions during the steelmaking process from blast furnace to converter, and the efficiency of steelmaking dust. Recycling becomes possible.
In addition, when separating steelmaking dust according to the content of metallic iron, the content of metallic iron is set to 30% by mass as a guide, and dust with a content rate of 30% by mass or more is recovered as high-metallic iron content dust. By collecting less than 30% by mass of dust as low-metal-iron-containing dust, it is easy to use properly when separating and returning to the steelmaking process.

  Further, specifically, a single or multiple-stage cyclone and a bag filter can be used as the separation and recovery device. Here, the metal iron high-content dust containing 30% by mass or more of metal iron can be recovered mainly by the first-stage cyclone, and the metal iron low-content dust containing less than 30% by mass of metal iron is 2 It is possible to collect with a cyclone and a bag filter after the stage.

In addition, when a large amount of iron scrap is required in the decarburization process, or when the silicon concentration in the pig iron is low and the heat tolerance in the decarburization process is low, the metal iron-rich dust should be returned preferentially. . Thereby, more iron can be recovered with less heat.
On the other hand, when it is not necessary to dissolve a large amount of iron scrap in the decarburization process, or when the silicon concentration in pig iron is high and the heat tolerance in the decarburization process is sufficiently high, dust containing low metal iron is preferential. It is good to send it back to. In this case, although the amount of heat for reducing iron oxide increases, it is possible to effectively change the iron content to pig iron while iron oxide serves as an oxidizing agent for silicon and carbon in pig iron.

  Furthermore, in the present invention, nitrogen may be used in place of the combustion gas, which makes it possible to reliably prevent oxidation of the steelmaking dust.

  As described above, according to the present invention, the metal iron contained in the steelmaking dust is prevented from being oxidized to prevent energy loss, and the energy consumption accompanying the drying of the wet dust collection dust is reduced, and further recycling is possible. It is possible to provide a steelmaking dust processing method and a steelmaking dust processing apparatus capable of easily transporting and handling the accompanying steelmaking dust and wet dust collecting dust.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings referred to in the following description are for explaining the configuration of the steelmaking dust processing apparatus of the present embodiment, and the size, thickness, dimensions, etc. of each part shown are the dimensions of the actual processing apparatus. The relationship may be different.

FIG. 1 shows a steelmaking dust processing apparatus 1 (hereinafter referred to as a processing apparatus) of this embodiment. The processing apparatus 1 of this embodiment is mainly applied when processing the steelmaking dust discharged | emitted with waste gas in the oxygen blowing process of a converter. The steelmaking dust contains metallic iron, iron oxide, and in some cases zinc oxide, and other impurities.
The processing apparatus 1 shown in FIG. 1 is roughly configured by a wet dust collecting dust drying apparatus A containing steelmaking dust and a dried steelmaking dust separation and recovery apparatus B.

  The drying device A includes a dryer main body 2a having a built-in drying flow channel 2, a combustion gas supply device 3 for supplying combustion gas to the dryer main body 2a, and a wet dust collecting dust from the drying flow channel 2 of the dryer main body 2a. It is comprised from the extrusion apparatus 4 (extrusion mechanism) for extruding to.

  The combustion gas supply device 3 includes a burner device 3a and a supply pipe 3b for supplying combustion gas from the burner device 3a to the dryer main body 2a. The burner device 3a is supplied with coke gas (COG) and LNG as fuel, and is also supplied with air as an oxidant, and the fuel is burned by the burner built in the burner device 3a to generate combustion gas. The The components contained in the combustion gas include a small amount of oxygen and a small amount of carbon monoxide or nitrogen oxide, but most of the components are nitrogen and carbon dioxide. From the viewpoint of these components, the combustion gas is almost inert. It can be said that it is a good gas. The temperature of the combustion gas supplied to the dryer main body 2a is preferably in the range of 400 ° C. or higher and 800 ° C. or lower, and more preferably in the range of 400 ° C. or higher and 600 ° C. or lower. If the temperature is 400 ° C. or higher, the amount of heat is sufficient, and the moisture contained in the wet dust collection dust can be completely evaporated. Further, if the temperature is 800 ° C. or lower, there is no possibility of damaging the bag filter due to the heat of combustion gas or the ignition of dust.

  Next, the dryer main body 2a is composed of a hollow cylindrical housing 2b, and the inside of the housing is a drying flow path 2. An introduction port 2c for introducing combustion gas is provided on the lower side of the housing 2b, and an exhaust port 2d for discharging combustion gas is provided on the upper side of the housing 2b. Accordingly, the dryer main body 2a is configured such that the combustion gas flow becomes an upward air flow and flows from the lower side (upstream side) of the drying flow path 2 toward the upper side (downstream side). Further, a supply pipe 3b of a combustion gas supply device is connected to the introduction port 2c, and a delivery pipe 2f for sending combustion gas containing steelmaking dust after drying to the separation recovery device B is connected to the discharge port 2d. Yes.

  Further, a rotor 2g for stirring the combustion gas flow is provided below (upstream) in the drawing of the drying flow path 2, and the combustion gas flow flows through the drying flow path 2 uniformly by the rotor 2g. It is configured. Further, a rectifying plate 2h is disposed above (downstream side) of the drying flow path 2 in the figure.

  An extrusion device 4 is attached to the housing 2 b corresponding to the midstream portion of the drying flow path 2. The extrusion device 4 may be any device that can extrude a highly viscous fluid at a constant speed. For example, a screw conveyor 4a can be used as illustrated. This screw conveyor 4a is comprised from the hollow cylinder-shaped exterior body 4b and the screw 4c rotatably attached to the inside of the exterior body 4b. An opening 4d is provided on the downstream side of the exterior body 4b, and the interior of the exterior body 4b communicates with the drying flow path 2 through the opening 4d.

A hopper 14 is attached upstream of the exterior body 4b. The hopper 14 is filled with wet dust collection dust having a water content of 30% by mass or less. The wet dust collection dust includes granular dust containing steelmaking dust having an average particle size of 20 μm or more and dehydrated cake containing steelmaking dust having an average particle size of less than 20 μm. Here, as the properties of granular dust including steelmaking dust having an average particle size of 20 μm or more, granular dust including steelmaking dust having an iron content of 90% by mass (dry dust base) or more and a moisture content of 20 to 30% by mass and an average particle size of less than 20 μm. Examples of the properties include iron content of 70% by mass (dry dust base) or more and water content of 10% by mass or less. Further, the wet dust collection dust may be a mixture of a dehydrated cake and granular dust, or may be composed only of a dehydrated cake.
Such wet dust collection dust is prepared by a wet dust collection dust preparation device (not shown) installed at a place different from the steel dust processing apparatus. That is, granular dust is prepared by collecting steelmaking dust in water and then allowing it to spontaneously settle in water. This granular dust can be collected with a coarse particle separator. Moreover, a dehydrated cake is prepared by dehydrating the supernatant liquid after the granular dust settles and removing water to some extent.
Due to the fact that wet dust collection dust is prepared through a two-step process as described above, some of the granular dust may contain steelmaking dust with an average particle size of less than 20 μm, and some of the dehydrated cake Steelmaking dust having an average particle size of 20 μm or more may be included.

Next, the sorting and collecting apparatus B will be described. The processing apparatus 1 shown in FIG. 1 includes a plurality of cyclones 5 connected to the downstream side of the dryer main body 2a and a bag filter 6 connected further downstream of the cyclone 5 as the separation and recovery apparatus B. Has been.
The cyclone 5 of the present embodiment is composed of two stages. The first-stage cyclone 5a is connected to a delivery pipe 2f extending from the dryer main body 2a, and the second-stage cyclone 5b is connected to the downstream side of the first-stage cyclone 5a. The bag filter 6 is connected to the downstream side of the second-stage cyclone 5b.

  The first-stage cyclone 5a includes a first cyclone main body 15a and a first recovery unit 15b connected to the lower side of the first cyclone main body 15a. The second-stage cyclone 5a includes a second cyclone main body 15c and a second recovery unit 15d connected to the lower side of the first cyclone main body 15c. Further, the bag filter 6 includes a filter main body 6a and a final recovery unit 6b connected to the lower side of the filter main body 6a.

  Furthermore, a storage hopper 7 and a blowing tank 8 are attached to the separation and recovery device B. The storage hopper 7 is connected downstream of each of the cyclones 5a and 5b and the collecting portions 15b, 15d and 6b of the bag filter 6, and can store steelmaking dust separated and collected by the cyclone or the like. The blowing tank 8 is connected further downstream of the storage hopper 7 so that steelmaking dust can be returned to the molten pig iron flowing in the steelmaking process from the blast furnace to the converter. The steelmaking dust may be returned at any timing as long as it is between pig iron discharged from the blast furnace and decarburization processing in the converter. The storage hopper 7 and the blowing tank 8 are preferably in an inert gas atmosphere such as nitrogen in order to prevent oxidation of the separately collected steelmaking dust.

  Moreover, in the processing apparatus 1 of this embodiment, in order to prevent the oxidation of steelmaking dust, it is desirable to completely seal the space from the extrusion apparatus 4 to the blowing tank 8 to prevent the entry of oxygen from the outside. .

  Next, the steelmaking dust processing method of the present embodiment will be described using the above processing apparatus 1 as an example. This processing method is roughly composed of a drying step of drying steelmaking dust contained in the wet dust collection dust by the drying device A and a separation and recovery step of separating and collecting the steelmaking dust by the separation and recovery device B.

  In the drying step, wet dust collection dust having a moisture content of 30% by mass or less, in which steelmaking dust is contained, is extruded into a dry flow path in which a combustion gas flow of 400 ° C. or more and 800 ° C. or less flows. This is a step of evaporating the water and flowing steelmaking dust on the combustion gas flow and sending it to the subsequent separation and recovery device.

The drying process will be described more specifically. First, in the combustion gas supply device 3, for example, coke gas is burned with air to form combustion gas. The temperature of the combustion gas at this time is preferably 400 ° C. or higher and 800 ° C. or lower, and more preferably 400 ° C. or higher and 600 ° C. or lower. The temperature of the combustion gas may be adjusted by diluting with nitrogen gas or the used combustion gas discharged from the bag filter 6 and lowering the temperature.
The temperature-adjusted combustion gas is supplied to the drying flow path 2 of the dryer main body 2a via the supply pipe 3b, and flows in the drying flow path 2 as a combustion gas flow. The flow rate of the combustion gas is preferably 400 Nm ³ / h or more and 1200 Nm ³ / h or less.

  On the other hand, the steelmaking dust discharged together with the exhaust gas in the oxygen blowing process in the converter is collected by a wet dust collector (not shown) and then sent to a wet dust collector preparation apparatus (not shown). In the wet dust collection equipment not shown, the supplied steelmaking dust slurry is naturally settled in a coarse separation tank to form granular dust, and the slurry settled in the subsequent thickener is further dehydrated. A cake. And the wet dust collection dust which consists of a mixture of a granular dust and a dewatering cake or a dewatering cake single is prepared. The prepared wet dust collection dust is sent to the screw conveyor 4a (extrusion apparatus). In addition, the wet dust collection dust in the dry flow path 2 can be sufficiently dried by setting the moisture content of the wet dust collection dust to 30% by mass or less. If the water content exceeds 30% by mass, the steelmaking dust contained in the wet dust collection dust is not sufficiently dried, which is not preferable.

  The wet dust collection dust supplied to the screw conveyor 4a is gradually pushed out to the drying flow path 2 side while being kneaded by the screw 4c. By kneading the screw 4c, the water content is further reduced by about several mass%. The extrusion speed at this time is preferably about 6 t / h or more and 15 t / h or less as the extrusion amount per unit time of the wet dust collection dust, although it depends on the flow rate of the combustion gas.

  The wet dust collection dust pushed out into the drying channel 2 is immediately evaporated by touching the high-temperature combustion gas, and the steelmaking dust that has been solidified by the water loses the binding force and becomes dusty. Then, it is lifted by the combustion gas flow that has become an ascending air current, and is directly carried on the combustion gas flow and discharged from the discharge port 2d of the dryer main body 2a.

  The combustion gas flow used for drying wet dust collection dust is a gas obtained by burning a fuel such as coke gas with air, and the majority of the gas components are inert gas consisting of carbon dioxide and nitrogen. is there. Therefore, even if the steelmaking dust is exposed to the combustion gas, the metal iron contained in the steelmaking dust is less likely to be oxidized, and the physical properties of the steelmaking dust are hardly changed by drying. Therefore, the steelmaking dust once made into wet dust collection dust is returned again to the original dust shape in the drying flow path.

  Next, in the separation and recovery step, the steelmaking dust dried in the drying step is divided into a high-metal-iron-containing dust containing 30% by mass or more of metallic iron and a low-containing metal-iron containing metal iron of less than 30% by mass. Separate and collect.

More specifically explaining the separation and recovery step, the steelmaking dust that has been dried together with the combustion gas is sent to the first-stage cyclone 5a through the delivery pipe 2f. In the first-stage cyclone 5a, only the dust having an average particle size of 30 μm or more is classified and recovered from the steel-making dust contained in the combustion gas, and the remaining steel-making dust is sent to the second-stage cyclone 5b together with the combustion gas. Steelmaking dust classified and collected by the first-stage cyclone 5a is stored in the first collection unit 15b at the lower part of the cyclone.
As for the steelmaking dust sent to the second-stage cyclone 5b, only dust having an average particle diameter of 1 μm or more and less than 30 μm is classified and recovered, and the remaining steelmaking dust is sent to the bag filter 6 together with the combustion gas. Steelmaking dust classified and collected by the second-stage cyclone 5b is stored in the second collection unit 15d at the lower part of the cyclone.
In the bag filter 6, the remaining steelmaking dust having an average particle diameter of less than 1 μm sent together with the combustion gas is separated from the combustion gas, and the combustion gas is discharged out of the system. The separated steelmaking dust is stored in the final recovery unit 6b. In addition, the value of the average particle diameter enumerated here can be suitably changed by changing the operation conditions of each of the cyclones 5a and 5b and the bag filter 6.

The steelmaking dust recovered by the first-stage cyclone 5a mainly contains about 30% by mass or more of metal iron, and can be said to be a metal iron high content dust having a relatively high content of metal iron. Since this dust contains a large amount of metallic iron, its specific gravity is relatively heavy and the average particle size is large. Therefore, most of the dust is recovered by the first-stage cyclone 5a.
On the other hand, the steelmaking dust recovered by the second-stage cyclone 5b or the bag filter 6 mainly contains metallic iron in an amount of about 0% by mass to less than 30% by mass, and the content of metallic iron is relatively low. It can be said that it is contained dust. Since this dust contains a small amount of metallic iron and contains a large amount of iron oxide, the specific gravity is relatively light and the average particle size is small, so that it is recovered by the second-stage cyclone 5b or the bag filter 6.

  Either one or both of the metal iron high-content dust and the metal iron low-content dust collected as described above is returned from the blowing tank 8 to the steel making process via the storage hopper. It is preferable that the metal iron-rich dust is preferentially returned to the pig iron when the heat tolerance in the decarburization process is low. Moreover, it is preferable to return metal iron low content dust in pig iron preferentially, when the heat tolerance in a decarburization process is high enough.

As described above, according to the steelmaking dust treatment method of the present embodiment, even when the steelmaking dust is exposed to combustion gas, the metal iron contained in the steelmaking dust is less likely to be oxidized, and the physical properties of the steelmaking dust are hardly changed by drying. Further, since it is not oxidized, the steelmaking dust once made into wet dust collection dust can be returned to the original dust form again in the drying flow path.
The steelmaking dust thus made into dust is classified for each average particle size by a separation and recovery device. The classification component having a relatively high average particle size contains a large amount of metallic iron, and the classification component having a relatively small average particle size. Contains a lot of iron oxide and less metal iron. Therefore, by separating and collecting steelmaking dust according to the content of metallic iron, the separated steelmaking dust can be returned under optimal conditions during the steelmaking process from the blast furnace to the converter. Recycling is possible.

  FIG. 2 shows another example of the steelmaking dust processing apparatus 11 of the present invention. The difference between the processing apparatus 11 shown in FIG. 2 and the processing apparatus 1 shown in FIG. 1 is the configuration of the combustion gas supply apparatus. That is, the combustion gas supply device 13 in the processing apparatus shown in FIG. 2 includes a burner device 13a, a heat exchanger 13b, and a nitrogen gas supply pipe 13c, and the heat of the combustion gas generated by the burner device 13a is The nitrogen gas is supplied to the nitrogen gas via the heat exchanger 13b so that the temperature of the nitrogen gas is 400 ° C. to 800 ° C., and this high-temperature nitrogen gas can be supplied to the drying flow path 2.

  According to the processing apparatus 11 of this example, wet dust collection dust can be dried with high-temperature pure nitrogen, oxidation of steelmaking dust can be almost completely prevented, and the yield of metallic iron can be further increased. Can do.

Examples of the present invention will be described below.
A processing experiment of steelmaking dust was performed using the processing apparatus shown in FIG.
First, COG and air were supplied to the burner device at a ratio of air / fuel ratio of 1: 1 and burned to generate combustion gas of about 400 to 600 ° C. This combustion gas was supplied to the drying channel at a flow rate of 600 Nm ³ / h. A mixture of a dehydrated cake having a moisture content of 23% by mass and a granular dust having a moisture content of 8% by mass including steelmaking dust having a particle size of 20 μm or more (dehydrated cake: granular dust = 8: 2 in terms of mass ratio) of 100 kg is extruded. / H for extrusion into the drying channel.
In the first-stage cyclone, dust having an average particle size of 65 μm or more was recovered as high-metal iron-containing dust. Further, in the second-stage cyclone, dust having an average particle diameter of 2 μm was collected as low-metal iron-containing dust. Furthermore, in the bag filter, dust having an average particle diameter of 1 μm or less was recovered as low-metal iron-containing dust.
About the collect | recovered dust, the content rate of the component of a dust, an average particle diameter, and a particle | grain of 10 micrometers or less was measured. The results are shown in Table 1.

As shown in Table 1, it can be seen that the dust of the sample 1 collected by the first-stage cyclone has a high content of metallic iron of about 43% by mass. On the other hand, the dust of Sample 2 or Sample 3 collected by the second-stage cyclone or bag filter has low metal iron contents of 0.8% by mass and 0.6% by mass, respectively, while FeO is 66. 5 mass% and 76 mass% are understood to be extremely high.
This is because dust containing a lot of metallic iron has a large average particle size and is recovered at a relatively early stage, while dust containing a lot of iron oxide is bulky and has a low specific gravity and a small average particle size. Therefore, it is thought that it was collected after the second-stage cyclone.

FIG. 1 is a schematic view showing an example of the configuration of a steelmaking dust treatment apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing another example of the configuration of the steelmaking dust processing apparatus according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 ... Processing apparatus (steel-making dust processing apparatus), 2 ... Drying flow path, 4 ... Extrusion apparatus (extrusion mechanism), A ... Drying apparatus, B ... Separation collection apparatus

Claims (7)

A method for treating steelmaking dust discharged in a pig iron impurity removal process,
Moisture in the wet dust collection dust is extruded by extruding a wet dust collection dust having a moisture content of 30% by mass or less in which the steelmaking dust is contained in a dry flow path through which a combustion gas flow of 400 ° C or higher and 800 ° C or lower flows. Evaporating and flowing the steelmaking dust into the combustion gas stream;
The steelmaking dust is separated into a high-metal-iron-containing dust and a low-metal-iron-containing dust whose metal iron content is lower than that of the high-metal iron-containing dust by a separation and recovery device disposed downstream of the drying flow path. A method for treating steelmaking dust, comprising a separation and recovery step of separating and recovering.   2. The steelmaking dust according to claim 1, wherein the metal iron content of the high metal iron content dust is 30% by mass or more, and the metal iron content of the low metal iron content dust is less than 30% by mass. Processing method.   The 1st or 2 or more cyclone connected to the downstream of the said drying flow path, and the bag filter connected with the downstream of the said cyclone are used as the said separation collection | recovery apparatus, The Claim 1 or 2 characterized by the above-mentioned. The processing method of the steelmaking dust of description.   4. The metal iron high-content dust or the metal iron low-content dust collected in the fractional collection step is returned to the molten pig iron in the molten state. 5. Steelmaking dust treatment method.   The method for treating steelmaking dust according to any one of claims 1 to 4, wherein nitrogen gas having a temperature of 400 ° C or higher and 800 ° C or lower is used instead of the combustion gas. A processing apparatus for processing steelmaking dust discharged in a pig iron impurity removal process,
A drying flow path through which a combustion gas flow of 400 ° C. or higher and 800 ° C. or lower flows, and an extrusion mechanism for extruding wet dust collecting dust containing water content of 30% by mass or less into the drying flow path are provided. Drying equipment,
Fractionation that is arranged downstream of the drying flow path and separates and collects the steelmaking dust into metal iron high content dust and metal iron low content dust whose metal iron content is lower than the metal iron high content dust A recovery device;
An apparatus for treating steelmaking dust, comprising: The steelmaking dust according to claim 6, wherein the metal iron content of the high metal iron content dust is 30% by mass or more, and the metal iron content of the low metal iron content dust is less than 30% by mass. Processing equipment.

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