JPH06174383A - Treating method of electric furnace dust - Google Patents

Abstract

PURPOSE:To furnish a novel treating method wherein impurity components such as Zn, Pb, Cl, etc., are removed and collected from electric furnace dust containing these components, while an iron content is returned in the form of higher purity to an electric furnace, and an exhaust gas is made harmless. CONSTITUTION:Solid carbon and ferric chloride in the form of fine powder are added to and mixed in electric furnace dust containing Zn, Pb, Cl, etc., and mixing kneading, granulation and drying are conducted. Thereafter the dust thus processed is subjected, together with an externally charged carbon material, to reduction, chlorination, volatilization and roast in a heating furnace such as a rotary kiln and thereby Zn and Pb are volatilized and removed as chloride, while an iron content is reduced. A burned material thus produced is subjected to magnetic separation and a magnetized material is supplied to an electric furnace as an electric furnace material, while a non-magnetized material is classified or sieved, so as to remove an ash content therefrom, and added to the externally charged carbon material for circulation. The chloride volatilized in an exhaust gas is led to a vertical type packing tower or the like, deposited and precipitated on a packed material and removed. Thereafter a hydrogen chloride content in the exhaust gas is removed by adsorption by blowing ferric hydroxide, limonite, iron oxide in the form of fine powder, or the like, into the exhaust gas, while the chloride thus treated is collected by a dust collector and supplied as the ferric chloride to a head for circulation.

Description

Detailed Description of the Invention

[0001]

[Necessity of this patented technology] Various kinds of large amounts of dust are generated from the steel industry, some of which are recycled to related processes, and some of which are effectively used for other purposes. However, among them, dust containing zinc, lead, etc., especially those generated in the electric furnace refining process, have not established an effective and economical utilization method, and therefore non-ferrous refining at a high cost is incurred. The reality is that the processing is outsourced to the company. However, even if all of the generated amount is not processed, a surplus occurs, and there is a big problem that immobilization or detoxification treatment of harmful components must be performed before landfill disposal. Various attempts have been made so far to recycle these electric furnace dusts. For example, Japanese Patent Laid-Open Publication Nos. 48-42909 and 48-5 are disclosed.
The number of patent applications such as “7-35644” and “Sho 58-37138” is extremely large, but there is no practical technique that can completely solve the problems described below, and the establishment of this technique is great. It can be said that they have social needs.

[0002]

2. Description of the Related Art This type of dust has a fine grain size characteristic, and in addition to Fe, which is a component contributing to iron making, is a harmful component such as Zn, Pb, and Cl.
It is characterized by containing. Therefore, it is necessary to remove these harmful components in order to circulate them in the iron refining process and to effectively utilize the iron content. The "reduction method" and the "chlorination method" are known as dry methods for removing Zn and Pb. When applying the “volatilization method”, there are the following technical problems.

[0003]

[Problems of the reduction method] Since the boiling point of metallic zinc is 907 ° C, it is theoretically possible to reduce zinc in the dust to metallic zinc under the reduction temperature conditions above this temperature to volatilize and remove it. However, since the boiling point of metallic lead is 1,620 ° C., a considerably high temperature is required to volatilize and remove both of these components at the same time. As is well known, Fe and Si
The limiting temperature for reduction firing of a substance containing O ₂ is 1,050.
It is said to be about ℃. If this temperature is exceeded, FeO-S
This is because a melt of the iO ₂ -based component is generated and mutual fusion of the charged materials occurs, which makes the operation of the reduction furnace extremely difficult. Further, in the case of the dust, the chlorine content contained acts on the adhered water or the bound water in the charging material by heating to generate hydrogen chloride, so that it is necessary to neutralize and detoxify the exhaust gas. Regarding this point alone, if limestone or quick lime is mixed in the charge, it can bond with hydrogen chloride to form calcium chloride and immobilize it. : 772 ° C.) will occur to amplify the mutual fusion of the above-mentioned charges. Due to these problems, de-Z removal of the dust by the reducing volatilization method
The n, Pb processing is extremely difficult.

[0004]

[Problems of the chlorination volatilization method] The chlorination volatilization method is a method in which metal components such as Zn and Pb are converted to chlorides and volatilized and removed. However, chlorine gas or calcium chloride is generally used as a chlorine source. There is. However, there are relatively few cases where it is applied to the raw material for steelmaking, and the existing process is the volatile volatile beret method (commonly known as the light emission method), which is applied to the removal and recovery of Cu, Zn, Pb, Au, Ag, etc. in sulfuric acid ore. The sum process is the only one. However, in this process, since calcium chloride as a chlorine source is added when granulating the raw ore, the amount of addition is limited, and therefore the amount of metal that can be volatilized is not so large. When the amount of metal to be volatilized is large, if the amount of calcium chloride is increased accordingly,
C for the same reason as described in the preceding paragraph and due to reaction with ferric oxide
The generation of the a-ferrite-based melt causes mutual fusion of the charged materials, which prevents stable operation. On the other hand, the method using chlorine gas can volatilize a larger amount of metal components than the above-mentioned method, but the cost burden of chlorine gas is still heavy even if it succeeds in efficient recycling.
This is the bottleneck to the establishment of this process.

[0005]

[Characteristics of the Patented Technology] The inventor has conducted research to overcome the problems of both processes described above, and has established rational and practical technology. The features of the present technology will be described below.

[0006]

[Principle of Zn removal and Pb control and its progress] Zn and Pb
If a reduction method is used to remove the above, high temperature is required as described above, and the difficult problems that accompany it are encountered.
Therefore, the removal of Zn and Pb is performed by chlorination volatilization. However, if calcium chloride or chlorine is used as the chlorine source, it hits the operational barrier as described above, and this must be solved. As a new technology for this purpose, we have developed a method that uses iron chloride as a chlorine source and controls the release of chlorine by the progress of iron reduction. The reduction temperature is set at 1,000 ° C. with the goal of FeO-SiO
It is below the formation temperature of the _{2 system} melt, and iron chloride becomes metallic iron while releasing chlorine as the reduction progresses, so it is stable without the above-mentioned melt of calcium chloride and the formation of Ca-ferrite system melt. Operating conditions are maintained. Zn or Pb
In order to volatilize chlorinated satisfactorily, 1.2 to 1.5 equivalents of iron chloride with respect to the components to be volatilized are necessary. Thus, from the electric furnace dust, harmful Zn and Pb are volatilized and removed as chlorides, and at the same time, Fe is reduced to metallic iron. The reduction is carried out by the combined internal and external method of carbonaceous material,
The internal carbonaceous material may be fine powdery solid carbonaceous material, but if it is 5% or less, sufficient reduction is not performed, and if it is 15% or more, the carbonaceous material is too much to make granulation work difficult or granulate. Since the strength of the product may be reduced, 5 to 15% is suitable. The exterior carbonaceous material is preferably one having a low volatile content, for example, coke, anthracite, etc., and is mixed in a proportion of 30 to 100% by weight with respect to the granulated material. The effluent is first separated by magnetic separation to recover metallic iron, which is reused as a raw material for the electric furnace. The non-magnetic tailings are subjected to classification to remove ash, and then circulated as exterior carbonaceous material.

[0007]

[Collecting Volatile Chlorides] ZnCl ₂ from which chloride volatilization was removed.
PbCl ₂ etc. can be collected by collecting it with an ordinary dust collector such as a bag filter or an electric dust collector, but in order to detoxify exhaust gas described later, lower discharge type vertical pellets such as iron ore pellets or alumina balls Use a method of collecting in a mold packing tower. That is, the volatilized chloride-containing gas is introduced into the lower part of the packed column and is brought into countercurrent contact with the descending granular packing, and the gaseous chloride contained therein is converted into a solid by the temperature decrease to the packing surface. The particulates adhering to the chloride, which had been deposited on the sol, were removed and collected using a trommel or vibrating sieve, and this was used as a raw material for crude zinc.

[0008]

[Detoxification treatment of exhaust gas] Since the exhaust gas after the collection of volatile chlorides described in the previous section contains hydrogen chloride and a small amount of chlorine, it must be detoxified. In such a case, quick lime is blown into the exhaust gas, and it reacts with this to immobilize it as calcium chloride to render it harmless. In this process, iron chloride is used as the chlorine source for volatile chloride. In conjunction with this, limonite, iron hydroxide, or active iron oxide dust, etc., are blown into the exhaust gas in the form of fine powder to be dispersed and fixed as iron chloride to render it harmless. A trace amount of hydrogen chloride which cannot be removed by this method is completely absorbed and removed by contact with an alkaline liquid such as caustic soda and lime milk.

[0009]

[Explanation of Process Flow] A process flow diagram of the method of the present invention, which has been described above, is shown in FIG. That is, powdery solid carbonaceous materials and iron chlorides are added to dust containing zinc or lead, and after granulation / drying, external carbonaceous materials are added, and roasted in a rotary he kiln to obtain a reduced calcined product. , Zinc and lead are volatilized and collected as chlorides, and the discharged fired product is cooled and then separated by magnetic separation into reduced pellets and non-magnetic substances, which are recycled to the electric furnace and classified. Etc. to separate and concentrate the carbon content and circulate it to the exterior carbonaceous material.
Finely powdered iron hydroxide, limonite or active iron oxide dust is blown into the exhaust gas to render the exhaust gas harmless and circulate the collected matter as a chlorinating agent.

[0010]

Embodiment 1 Next, an embodiment of the technology of the present invention will be described. Fine coke and ferrous chloride (industrial chemicals) were mixed with the electric furnace dust having the composition shown in Table 1 at the compounding ratio shown in Table 2, and granulated into 13 to 16 mmφ pellets with a 1 mφ dish type granulator. After that, it is dried in a box dryer, and 100 g of pellets is mixed with 100 g of coke of -5 mm and 100 mmφ × 1.
External heating type roasting furnace with a temperature zone of 50 mmL
120 min. At 0 ° C. The roasted and fired product was divided into a magnetic product and a non-magnetic product by using a magnet. The components of the magnetic substance are as shown in Table 3, and the components of the non-magnetic substance have not been analyzed, but there is no great difference in appearance from the powder coke, and it can be sufficiently recycled.

[Table 1]

[Table 2]

[Table 3]

[0011]

Example 2 After depositing / removing chloride in the exhaust gas produced by reducing and volatilizing the pellet of the electric furnace dust raw material, HCl is usually contained in an amount of 4 to 5%. Assuming this, concentrated hydrochloric acid is heated and the hydrochloric acid-containing steam that escapes is sucked together with air to obtain an HCl concentration of 5% and a flow rate of 100 cc / mi.
n. Of the ferric hydroxide produced by the precipitation method in a dry and fine powder form at 10 g / min. It was added to this at a ratio of 100%, collected after contacting with gas, and analyzed for chlorine content to calculate absorbed HCl content.
% That is, the detoxification process of the exhaust gas is almost achieved.

[0012]

Industrial Applicability As described above, the method of the present invention has a completely new principle on the technique of completely treating and effectively utilizing the electric furnace dust containing Zn, Pb, etc., which was extremely difficult by the conventional method. Was developed and put into practical use,
With the spread of the method of the present invention in the future, it is expected that the burden of dust processing, which is currently bothering electric furnace manufacturers, will be considerably reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a process flow of a method of the present invention.

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location C22B 19/30

Claims (3)

[Claims] 1. An electric furnace dust containing zinc or lead,
Granules were obtained by adding 5 to 15% of solid carbon powder and iron chloride to 1.2 to 1.5 equivalents of the amount of volatile metal.
After drying, the exterior carbonaceous material is added and the product is subjected to reduction-double firing in a rotary kiln to obtain a reduced fired product, and components such as zinc and lead are volatilized and collected as chlorides. 2. In the above-mentioned treatment method, after the reduced calcined product is cooled, it is separated by magnetic separation into reduced pellets which are magnetically adsorbed substances and non-magnetically adsorbed substances, and the non-magnetically adsorbed substances are concentrated by sieving or air classification. A treatment method that circulates this to the exterior carbon material. 3. The treatment method according to claim 1, wherein the volatile chloride is cooled, and the flue gas after being precipitated, deposited, and collected is a fine powder of dry limonite, iron hydroxide, or active iron oxide. Exhaust gas that blows dust etc. and causes hydrogen chloride contained in the exhaust gas to adsorb and react with it to produce iron chloride and detoxify the exhaust gas, and collect this product with an electric dust collector and then circulate it to iron chloride Processing method.