JPH033732B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for treating special steel dust and sludge (hereinafter referred to as dust and sludge) generated during the manufacturing process of special steel, and particularly to a method for treating special steel dust and sludge (hereinafter referred to as dust and sludge). The present invention relates to a method for effectively recovering valuable metals by reducing and roasting them in an apparatus and feeding them into a metallurgical furnace. [Prior art] Generally, dust and sludge generated during the production of special steel contain harmful components such as Zn, Pb, and Cd, while also containing valuable metals such as Ni, Cr, and Fe. Since it is difficult to treat it directly as industrial waste, various treatment methods are being studied. As one method for this, a method has been adopted in some cases in which the dust and sludge are agglomerated and then fed into a metallurgical furnace for reuse. In addition, these dusts and sludge are reduced and melted in a special electric arc furnace to produce Fe-Ni.
- A method for producing Cr alloys is also used. [Problems with the prior art] However, the method of agglomerating the dust and sludge and putting it into a metallurgical furnace for reuse is difficult.
Since the sludge contains harmful components such as Zn, Pb, and Cd, there is a problem in that the treatment of the harmful components is costly, and the recovery rate of valuable metals is also low. Further, the method of reducing and melting dust and sludge using a special arc furnace has the problem of high costs because special equipment and expensive electrical energy are used. The present invention was made in view of the above circumstances, and
Uses simple equipment to remove harmful components from dust and sludge at a relatively low cost, and also removes Ni and Fe.
Improve the recovery rate of valuable metals by converting them into reduced metals and reusing them in metallurgical furnaces.
The purpose of the present invention is to provide a treatment method for making dust and sludge pollution-free. [Means for solving the problems] The method of the present invention that meets the above objectives uses special steel dust,
A first step in which a ring-forming agent containing a carbonaceous solid fuel necessary for reducing and roasting the sludge and a binder if necessary is added, kneaded, and then agglomerated into a predetermined size; After charging the agglomerated material thus obtained into a reduction roasting furnace, the carbonaceous fuel containing the agglomerated material is ignited to self-combust, and the combustion air is adjusted. The second step involves roasting the agglomerated material to a red-hot state, reducing and volatilizing harmful components such as Zn, Pb, and Cd, and reducing and converting valuable metals such as Ni, Cr, and Fe into metals. A third step in which the roasted agglomerates are charged into a metallurgical furnace without being reoxidized to recover valuable metals such as Ni, Cr, and Fe, and the volatiles volatilized in the second and third steps. The fourth step consists of collecting the substances by suction with a dust collector, and the carbonaceous solid fuel added to the dust and sludge is self-combusted to volatilize harmful components, and at the same time, the dust and sludge are melted in a reducing atmosphere. This method converts valuable metals into metals by reducing and roasting them without any heat loss, making it easy to recover valuable metals in metallurgical furnaces. Here, the reducing agent containing carbonaceous solid fuel in the first step is not only one consisting only of carbonaceous solid fuel, but also a reducing agent containing carbonaceous solid fuel such as Na ₂ CO ₃ , It also includes a reduction aid containing one or more of K ₂ CO ₃ , Ai powder, or ferrosilicon powder. In addition, coke, coal, etc. are mainly used as the carbonaceous solid fuel, and the amount used is at least the theoretical amount required to heat the agglomerate to a red-hot state and reduce the metal components contained therein. It is usually about 7 to 30% by weight based on dust and sludge. By the way, the above-mentioned reducing aid usually includes the above-mentioned
Na ₂ CO ₃ and K ₂ CO ₃ are used, but the amount added is normally 1 to 10% by weight based on dust and sludge, and when recovering valuable metals that are difficult to reduce, Ai powder or Preferably, ferrosilicon powder is used. Furthermore, agglomerating into a predetermined size usually means turning into briquettes or pellets, but the purpose of this is to form the treated dust into
This is done to ensure air permeability when the sludge is charged into a reduction roasting furnace. It is also possible to agglomerate by adding and kneading and granulating or agglomerating into an appropriate size. [Example] Next, with reference to the attached drawings, the processing procedure and operation of an example of the method for treating special steel dust and sludge according to the method of the present invention will be described in detail. First, a reducing agent containing a carbonaceous solid fuel necessary for reducing and roasting the special steel dust and sludge is added and kneaded, and the mixture is agglomerated using a compacting machine (not shown) (first step). This agglomerated dust,
After storing sludge 1 in a charging hopper 2, a feeder 3 attached to an opening at the bottom of the charging hopper 2 is used to charge the sludge 1 installed at the top of a reduction roasting furnace (hereinafter referred to as a roasting furnace) 4. From hopper 5 to roasting furnace 4
is filled with the agglomerated dust and sludge. This roasting furnace 4 is a multi-stage type and consists of an upper roasting zone 6 and a lower roasting zone 7. In the middle part of the roasting furnace 4, that is, at the bottom of the upper roasting zone 6, there is a grate 8 that can be opened and closed horizontally. It is designed so that the dust and sludge charged in the upper roasting zone 6 can be transferred to the lower roasting zone 7, and also has a grate 9 that can be opened and closed at the bottom of the lower roasting zone 7. The dust and sludge processed in the lower roasting zone 7 fall into the lower hopper 10. In addition, inside the upper roasting furnace body 6 and the lower roasting furnace body 7, partition plates 11 and 12 are provided, respectively.
is provided to ensure uniform roasting of dust and sludge. On the other hand, a duct 15 is connected to the top part 13 of the roasting furnace 4, and is connected to a dust collector (not shown), and has an air volume control valve 14 in the middle thereof. After charging the dust and sludge that have been agglomerated through the above steps into the roasting furnace 4 and igniting the dust and sludge in the lower part, a dust collector (not shown) is driven and the roasting furnace 4 is heated. In order to maintain a reducing atmosphere inside the kiln 4, the air volume control valve 1 is
Adjust 4. After this, the roasting progresses upwards, and the entire lower roasting zone 7 becomes a high-temperature fire layer, and when the fire layer rises to the middle of the upper roasting zone 6 through the middle fire grate 8,
After opening the grate 9 at the bottom of the furnace and allowing the roasted dust and sludge to fall into the lower hopper 10 and placing them into the sealed container 17 by operating the lower switching damper 16, the upper sealed lid of the sealed container 17 is opened. 18 is closed to cool the introduced dust and sludge. In this way, since the roasted ore, which is the roasted dust and sludge, is collected at once and charged into the sealed container 17, it is less susceptible to re-oxidation and can be charged at high temperature to the metallurgical furnace in the next process. It is easy to do. Next, after closing the grate 9 at the bottom of the furnace, the middle grate 8 is opened to transfer the agglomerated dust and sludge from the upper roasting zone 6 to the lower roasting zone 7, and then the fire The grate 8 is closed and new agglomerated dust and sludge are introduced into the upper roasting zone 6 to continue roasting. By repeating the above operations, the agglomerated dust and sludge are continuously roasted in the roasting furnace 4. Here, if the thickness of the roasting layer is too thick, the roasting speed will be slow and there is a risk of clinker formation, which will hinder continuous operation, so the thickness of the roasting layer of one stage should be 1000 mm or less to accelerate the roasting speed. It is preferable that air be appropriately introduced into the upper roasting zone 6 through the grate 8 provided at the bottom of the upper roasting zone 6.
In addition, the partition plates 11 and 12 are used to make the agglomerate layer uniform in air permeability and to ensure uniform roasting in the roasting furnace 4, but the diameter of the roasting furnace is 500 mm or less. This is not particularly necessary for small-sized reactors. Through the above steps, after charging the agglomerated material obtained in the first step into a reduction roasting furnace, the carbonaceous fuel contained in the agglomerated material is ignited and combusts by itself. By adjusting the air, the agglomerated material is roasted to a red-hot state, and harmful components such as Zn, Pb, and Cd are reduced and volatilized, and valuable metals such as Ni, Cr, and Fe are reduced and converted into metals. (second step) and keep it in a state where it will not be re-oxidized. Next, Ni reduced and metalized by the above process,
Valuable metals such as Cr and Fe are put into a metallurgical furnace to produce Ni,
Collect valuable metals such as Cr and Fe (third step). In addition, Zn, Pb, and Cd volatilized by the above process
The volatile substances are sucked into the dust collector and collected by the duct 15 provided at the top of the furnace (fourth step). In the above method, a two-stage roasting furnace is used, but the present invention is not limited to this. It is also possible to apply the method of the invention in a furnace. [Example] Next, experiments conducted to confirm the effects of the present invention will be described together with examples thereof. The top of the furnace is connected to the dust collector, and the cross section of the furnace body is 1300mm.
Square shaft furnace with mm x 1300mm and height 1400mm.
A roasting furnace was constructed with a grate installed at the bottom and middle of the furnace, with a spacing of 700 mm between the two grate, and 15 parts by weight of coke powder was added to 100 parts by weight of stainless steel electric furnace dust, which is an example of special steel dust. and 3 parts by weight of Na ₂ CO ₃ and filled with briquettes that were agglomerated into 50 mm x 40 mm x 30 mm charcoal shapes, the briquettes at the bottom of the furnace were ignited using a gas burner, and the furnace was slit. Roasting was performed while suctioning at a weak air flow rate of about 10 m ³ /min per 1 m ² of area. After this, the entire lower briquette becomes a fire layer,
When the fire layer has risen to about 2/3 of the briquettes in the upper tier, the roasted ore from the briquettes in the lower tier is discharged, then the briquettes in the upper tier are moved to the lower tier, and the briquettes in the upper tier are filled with new briquettes and roasted. The roasting was continued to perform reduction roasting of the stainless steel electric furnace dust. Next, 100 kg each of the roasted ore obtained by the above method and the briquettes before roasting were melted in a 1 ton Yale electric furnace to clarify the reduction roasting effect. The results are shown in Table 1. .

【table】

〔Effect of the invention〕

The method of the present invention is configured as described above, and when disposing of special steel dust and sludge, a predetermined amount of carbonaceous solid fuel is added and roasted before being reused in a metallurgical furnace, making it effective. In addition to making it possible to treat special steel dust and sludge to make them non-polluting, it has also become possible to easily remove harmful components and effectively recover valuable metals from special steel dust and sludge. Furthermore, since the roasting method of the present invention is carried out by a simple method that does not particularly require electric power, special steel dust and sludge can be treated at low cost.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram for explaining one embodiment of the method of the present invention. [Explanation of symbols] 1...Dust, sludge, 2...
...Charging hopper, 3... Feeder, 4... Roasting furnace, 6... Upper roasting zone, 7... Lower roasting zone, 8,
9... Grate, 11, 12... Partition plate, 15...
...Duct, 17... Sealed container.

Claims (1)

[Claims] 1. A method for treating special steel dust and sludge comprising the following steps. First step: Special steel dust and sludge are mixed with a ring agent containing a carbonaceous solid fuel necessary for reducing and roasting them, and a binder if necessary, and then agglomerated into a predetermined size. 2nd step: After charging the agglomerated material obtained in the 1st step into a reduction roasting furnace, the carbonaceous fuel contained in the agglomerated material is ignited to self-combust, and combustion air is released. By adjusting the temperature, the agglomerated material is roasted to a red-hot state, and harmful components such as Zn, Pb, and Cd are reduced and volatilized, and valuable metals such as Ni, Cr, and Fe are reduced and metalized. Third step: The agglomerated material that has been reduced and roasted in the second step is put into a metallurgical furnace without being reoxidized, and Ni,
Collect valuable metals such as Cr and Fe. Fourth step: The volatile substances volatilized in the second and third steps are collected by suction using a dust collector. 2. The method for treating special steel dust and sludge according to claim 1, wherein the reducing agent used in the first step is a carbonaceous solid fuel. 3. The method for treating special steel dust and sludge according to claim 1, wherein the reducing agent used in the first step comprises a carbonaceous solid fuel and a reducing aid. 4. The method for treating special steel dust and sludge as set forth in claim 3, wherein the reducing aid contains at least one of Na ₂ CO ₃ , K ₂ CO ₃ , AI powder, or ferrosilicon powder. . 5 Claims 1, 2, 3, 4, or 5, wherein the reduction roasting furnace used in the second step is a multistage roasting furnace composed of a plurality of roasting zones.
Method for treating special steel dust and sludge as described in Section 1.