JP3317131B2 - Method and apparatus for recovering zinc oxide from iron-making dust containing zinc oxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for recovering zinc oxide from ironmaking dust (hereinafter simply referred to as dust) generated in an ironworks containing iron oxide as a main component and low concentration of zinc oxide (ZnO). . Hereinafter, when zinc is used, it includes zinc metal, but mainly means zinc oxide.

[0002]

2. Description of the Related Art Ironworks that produce iron from iron ore, scrap and the like generate iron-making dust containing a large amount of iron oxide. Typical examples are blast furnace dust and converter dust. The proportion of blast furnace dust and converter dust in the total amount of dust generated from steel works reaches 60% or more. The main components of blast furnace dust are carbon and iron oxide, and the main components of converter dust are iron oxide. In each case, the zinc concentration is from 0.1 to 3 wt%, and the form is mainly zinc oxide, although it contains a small amount of metallic zinc.

[0003] In an ironworks, iron and carbon are recycled as raw materials for blast furnaces in order to recover iron and carbon from ironmaking dust. However, since zinc causes walls in the blast furnace, it is necessary to strictly control the amount of zinc accumulated in the blast furnace in order to recycle it as raw material for the blast furnace while ensuring stable operation of the blast furnace. is there. At present, the amount of zinc charged into a blast furnace is limited to 0.1 kg or less per ton of pig iron.

[0004] Therefore, in an ironworks, high-concentration zinc dust and low-concentration zinc dust are separated by a dezincing facility such as a wet cyclone, and only low-concentration zinc dust is recycled as a blast furnace raw material. On the other hand, high-concentration zinc dust is landfilled, but the amount of this type of dust increases,
Dust disposal is difficult.

On the other hand, in recent years, a considerable amount of scrap has been accumulated in Japan, and from the viewpoint of effective utilization of resources, the ratio of scrap as an iron source also tends to increase in an integrated steel mill. In addition, the proportion of galvanized steel sheet in the scrap is increasing, and the amount of zinc in the raw materials in steel works tends to increase.

[0006] Recently, as described above, since the amount of zinc in raw materials at steel works tends to increase, not only landfill treatment of high-concentration zinc dust, but also active recovery of zinc, and refining of zinc for refining. A technology for recovering zinc as a raw material is being studied. In order to use it as a zinc raw material for refining, it is necessary to increase the zinc concentration as much as possible, and the currently targeted zinc concentration is 50 wt%.

[0007] In addition to the above-mentioned blast furnace manufacturers, there are so-called electric furnace manufacturers. The main components of the electric furnace dust generated here are iron oxide and zinc oxide.
-30% and 15-25% zinc oxide. Approximately 60% of the amount of electric furnace dust generated is recycled as smelting zinc raw material, but the remaining 40% is landfilled. Electric furnace dust is also used for smelting as well as blast furnace dust and converter dust. There is a demand for expanded use as a zinc raw material.

Therefore, in order to recover zinc from the above-mentioned steelworks dust and use it as a zinc raw material for refining, it is an important issue how to efficiently concentrate the zinc concentration to 50 wt% or more.

JP-A-6-145830 discloses a method for recovering zinc in ironmaking dust as described below. Hereinafter, this technique will be described with reference to the drawings.
FIG. 4 shows a process diagram of this technique.

The ironmaking dust 2 stored in the first hopper 1A is sent to the mixer 4 together with the binder in the binder hopper 3 to be mixed. The mixture of the dust 2 and the binder is sent to a pan pelletizer, granulated into pellets, cured by a rapid curing machine 6, and then dried by a drying machine 7.
Dried by.

The pellets 10 are stored in a pellet hopper 8 and fed into a molten iron pot 9 simultaneously with the molten iron 11.
The pellets 10 that are simultaneously injected with the molten iron 11
And dispersed in the molten iron 11. Ironmaking dust 2
The iron oxide therein reacts with carbon and silicon in the molten iron, is reduced to iron, and is recovered in the molten iron as iron.

Further, zinc oxide in dust is reduced and evaporated by carbon in molten iron and oxidized in air,
It becomes fine zinc oxide particles of 10 μm or less. Evaporated iron and powdered cold pellets are suspended on the molten iron surface, and are collected together with zinc oxide particles by the dust collector 13 via the dust collection duct 12.

In order to increase the concentration of zinc in the dust collected by the dust collector 13, the dust collected by the dust collector 13 is again distributed via the distributor 15 to the second hopper 1 B.
And perform the same operation as described above. As a result, the zinc concentration in the dust increases, and the zinc concentration in the dust finally collected in the hopper 1E becomes 50 wt% or more.
It is significantly concentrated compared to the zinc concentration of the original ironmaking dust of 0.1 to 3 wt%.

[0014]

The above-mentioned technology has the following problems. That is, only one dust collector 13 is disposed, and the dust containing zinc collected by this is again granulated into pellets in total, and the operation of putting the re-granulated dust into the molten iron pot is performed by dust. It repeats 2-3 times until the zinc concentration in it reaches the target value.

Therefore, when the dust treated as described above is analyzed, there is a portion where the zinc concentration is high, but if the average zinc concentration of the whole dust does not reach the target value, the zinc Even the dust in the part where the concentration has reached the target value has to be re-granulated and re-reduced in the molten iron pot, increasing the processing cost and processing time required for granulation, handling and reduction. Inviting. Further, since the amount of dust to be reprocessed increases, the equipment cost for recovering zinc also increases.

Further, since the above-mentioned processing equipment processes dust a plurality of times, large-scale equipment is required for the iron-making dust to be processed. Further, when the treated dust reaches a predetermined concentration, the equipment temporarily stops the operation, prepares a new raw material again, and starts the operation. That is, it is a batch operation, and the efficiency is not desirable.

Therefore, the present invention selectively recovers a portion having a predetermined concentration from the collected dust, processes only a portion which does not reach a predetermined concentration again, and continuously performs an operation. It is an object of the present invention to provide a method for efficiently and more economically recovering zinc from steelmaking dust and an apparatus therefor.

[0018]

Means for Solving the Problems The present inventors put iron oxide containing zinc into molten iron held in a melting furnace, reduce iron oxide and zinc oxide in the molten iron, and convert the reduced zinc into steam. It has been found that when it is converted to zinc oxide and recovered as zinc oxide, the particle size of zinc oxide is smaller than that of iron oxide, which is another component composition, and most of the particle size is 5 μm or less. Therefore,
The inventors have invented a method and an apparatus for selectively collecting dust having a particularly small particle size from dust generated in the melting furnace.

According to a first aspect of the present invention, ironmaking dust containing zinc oxide is formed as agglomerated dust, and the agglomerated dust is charged into molten iron held in a melting furnace, and iron oxide and oxidized iron in the agglomerated dust are mixed. A method for recovering zinc oxide, comprising reducing zinc in molten iron, evaporating the reduced zinc, and sucking and recovering it as zinc oxide, comprising the following steps: This is a method for recovering zinc. (A) Dust generated from the melting furnace is sucked, and zinc oxide is collected, so that dust is gradually collected from dust having a large particle diameter. (B) The content of zinc oxide in the dust is less than a predetermined content. Is recycled again as a raw material of the agglomerated dust, and (c) the dust whose zinc oxide content is not less than a predetermined content is recovered as a zinc raw material. When the above method is adopted, a portion having a low zinc concentration and a portion having a high zinc concentration can be separated and collected from dust generated from the melting furnace, and only a portion having a low zinc concentration can be recycled, and a high portion can be used as a zinc raw material as it is. And efficient zinc recovery becomes possible.

According to a second aspect, in the first aspect,
In the method for recovering zinc oxide, in the first stage, dust having a particle size of 10 μm or more is mainly recovered from dust from the melting furnace, and in the second stage, dust having a size of 5 μm or more is mainly recovered. The third stage is a method for recovering zinc oxide from iron-making dust containing zinc oxide, wherein dust of 0.1 μm or more is mainly recovered. When such a means is adopted, in the first stage, the zinc concentration is low and the particle size is 10 μm.
m or less unreduced dust powdered by thermal shock,
In the second stage, dust having a low zinc concentration of 5 to 10 μm can be recovered, and in the third stage, dust having a particle size of 5 to 0.1 μm and a zinc concentration of 50 wt% or more can be recovered,
This dust does not need to be recycled. On the other hand, it is sufficient to recycle only dust having a zinc concentration of 5 μm or more and a zinc concentration of less than 50 wt%, and efficient collection becomes possible.

A third aspect of the present invention is an apparatus for recovering zinc oxide from iron-making dust containing zinc oxide, comprising the following members. (A) an agglomerating machine for converting iron-making dust containing zinc oxide into agglomerated dust, (b) a melting furnace for adding the agglomerated dust and holding molten iron for reducing the agglomerated dust, and (c) Two or more dust collectors for classifying dust containing zinc oxide generated by reducing zinc oxide and evaporating zinc in the melting furnace, in order of increasing particle diameter in the dust. The above-described zinc recovery method can be implemented in the above-described apparatus.

According to a fourth aspect, in the third aspect,
Among the two or more dust collectors, a first dust collector is a dust collector that mainly collects dust having a particle diameter of 10 μm or more from dust from the melting furnace, and a second dust collector is a dust collector that mainly collects dust of 5 μm or more. In addition, the third dust collector is a dust collector mainly for collecting dust of 0.1 μm or more, and is a device for collecting zinc oxide from iron-made dust containing zinc oxide. In the above apparatus, dust having a zinc concentration of 50 wt% or more can be collected in the third dust collector.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows the particle size distribution of iron-making dust which is a target of the present invention. The particle size distribution in the order of blast furnace dust, converter dust, and electric furnace dust is in the direction of smaller particle size. In addition, ironmaking dust is agglomerated dust,
Put the agglomerated dust into molten iron held in a melting furnace,
3 shows a particle size distribution of dust (hereinafter referred to as reduced dust) generated when iron oxide and zinc oxide in the agglomerated dust are reduced in molten iron.

Blast furnace dust ranges from 300 to 5 μm, converter dust ranges from 100 to 1 μm, and electric furnace dust ranges from 20 to 1 μm, whereas reduced dust ranges from 5 μm to 0.1 μm.
m, and the average is about 1.5 μm. Generally, the smaller the particle size, the higher the zinc concentration. Also,
When the zinc concentration of each of the dust particles was examined, the particles having a particle size of 5 μm or less had a high zinc concentration.

In particular, with respect to the reduced dust, particles having different particle diameters were observed by a scanning electron microscope, and at the same time, identification by X-ray was performed. As a result, particles having a particle size of 5 μm or less contained much zinc oxide, and particles having a particle size exceeding 5 μm were mostly iron oxide. Quantitatively, particles having a particle size of 5 μm or less had a zinc concentration exceeding 50 wt%.

Therefore, the classification performance, that is, by installing a plurality of dust collectors having different separable particle diameters in the exhaust gas line on the exit side of the melting furnace, the reduced dusts having different zinc oxide concentrations in the generated dusts can be separately separated. It can be collected and collected. When such a method is adopted, collected dust having a higher zinc concentration is discharged out of the system and supplied to a zinc refining maker according to the target zinc concentration, and collected dust having a low zinc concentration is It is possible to perform a continuous recirculation process in which the agglomeration process is performed again and the molten product is put into the melting furnace.

From the above, when the ironmaking dust is subjected to agglomeration treatment and put into the molten iron in the melting furnace, the iron oxide in the dust is reduced in the molten iron and recovered in the molten iron. The zinc oxide in the dust is reduced and vaporized, and is discharged out of the melting furnace as zinc oxide dust. At this time, the supplied zinc-containing dust is partially powdered by thermal shock from molten iron, and discharged outside the system as relatively large particles (5 μm or more) without being reduced.

In order to improve the zinc concentration in the reduced dust, it is necessary to reduce unreduced dust having a large particle size.
Since it is difficult to completely eliminate the generation of unreacted dust, the reduced dust, which is zinc oxide, and the unreduced dust are separated and collected, and only the latter, dust having a low zinc concentration, is subjected to agglomeration treatment again. And put into a melting furnace for reduction treatment. On the other hand,
Small-diameter dust having a zinc content of a predetermined amount or more can be used as a zinc raw material that can be supplied to a smelting maker as it is.

Therefore, the present invention employs a zinc recovery method and apparatus as shown in FIG. 1 as an embodiment. Ironmaking dust 22 containing zinc oxide stored in dust hopper 21
Is sufficiently mixed in a mixer 27 together with a reducing coke 24 stored in a coke hopper 23 and a binder 26 stored in a binder hopper 25, and then, in a compactor 28, a diameter of 15 to 30 mm and a thickness of 10 mm. After being formed into briquette-like agglomerated dust having a size of about 20 mm, it is quantitatively fed into a melting furnace 31 by a quantitative feeder 30 through an intermediate hopper 29.

It is desirable that the agglomerated dust contain a reducing carbon material for reducing zinc oxide and iron oxide, for example, coke in order to increase the reduction rate. The compacting machine may be a so-called pelletizer. The melting furnace 31 may be, for example, an induction melting furnace or another heating furnace, for example, an arc heating furnace or a gas heating furnace.

The temperature inside the melting furnace is 1400-1600.
The molten iron 32 at a temperature of ℃ is held, and the agglomerated dust 33 put in has a specific gravity of 1.2 to 2.5 g / cm ^3, which is smaller than the molten iron 32, so that it is deposited in layers on the surface of the molten iron. I do. The iron oxide in the agglomerated dust is mainly reduced by the carbon in the agglomerated dust and recovered as iron in the molten iron. Zinc oxide is reduced and evaporated by carbon and the like in the agglomerated dust, and is oxidized by oxygen in the furnace to form fine zinc oxide particles of 10 μm or less, mostly 5 μm or less.

On the other hand, the zinc-containing dust in the agglomerated dust is partly powdered by the thermal shock from the molten iron and discharged out of the system without being reduced. This unreduced dust is mainly 5 μm or more. Also, some iron oxides are discharged outside the system. The dust generated from the melting furnace 31 is the furnace lid 31a.
Is collected by a first dust collector 34, a second dust collector 35, and a third dust collector 36 via a duct 31b provided in the first dust collector.

The dust is sucked by the exhaust fan 37 in the direction of the dust collector. At this time, it is desirable to make the capacity of the exhaust fan 37 sufficiently large and reduce the pressure in the melting furnace with respect to the atmospheric pressure in order to promote the evaporation of zinc. Although it can be changed according to the particle size distribution of the reduced dust, in the examples, the classification limit particle size of each is set as follows.

First dust collector; 10 μm Second dust collector; 5 μm Third dust collector; 0.1 μm That is, the first dust collector collects dust of 10 μm or more, the second dust collector collects dust from 10 μm to 5 μm, and the third dust collector Is designed to collect dust from 5 μm to 0.1 μm. Specifically, in the present embodiment, the first dust collector 34 is a normal cyclone, and the second dust collector 3
5 is a high-performance cyclone, and the third dust collector 36 is a bag filter type dust collector.

FIG. 3 shows the particle size distribution of the dust collected by each dust collector, and the collection performance almost as originally set is obtained. The components of the collected dust in each dust collector are as shown in Table 1. In this embodiment, the target zinc concentration is 5
Since it is set to 0% or more, dust collected by the third dust collector 36 is stored in the product hopper 38.

[0036]

[Table 1]

A first dust collector 34 and a second dust collector 35
Dust collected in the above, each zinc concentration is 28wt
%, 31 wt%, the target zinc concentration (50 wt%
%), It passes through the recycling line 40,
It was returned to the dust hopper 21. This recirculated dust 41
Is granulated again by the agglomerator 28 together with the dust 22 of the raw material, and is again charged into the melting furnace 31 to be reduced on the molten iron 32. The weight ratio of the dust collected by each dust collector was approximately 2: 3: 5.

In the above embodiment, the dust collected by the second dust collector 35 was returned to the dust recycling line 40 because the zinc concentration of the dust was lower than the target zinc concentration.
When the zinc concentration of the dust is higher than the target zinc concentration, the second dust collector 35
The dust discharge line can be switched at any time.

In this manner, the minimum necessary dust is recirculated, and high-concentration zinc dust can be efficiently collected. The collected dust is subjected to agglomeration treatment by the product agglomeration machine 39 and delivered to a smelting maker. The smelting maker processes the zinc oxide as a raw material to reproduce zinc.

[0040]

As described above, according to the method of the present invention, iron oxide containing zinc is agglomerated, and this agglomerated dust is put into molten iron in a melting furnace to oxidize the dust. The zinc is reduced and vaporized, and the vaporized zinc is recovered as zinc oxide. Further, at this time, in the apparatus for collecting zinc in dust, at least two dust collectors having different dust collection limits are installed to collect zinc oxide, and only the collected dust whose zinc concentration in the dust is lower than the target concentration is used. If necessary, the dust can be returned to the treated dust again to increase the zinc concentration in the dust.

On the other hand, when the zinc concentration in the dust is higher than the target concentration, it is supplied to a zinc refining manufacturer as it is. Therefore, zinc can be recovered more efficiently and more economically than in the past, especially from ironmaking dust. Further, the method of the present invention is not only the iron-making dust, iron oxide containing zinc,
That is, it goes without saying that the present invention can be applied to sintered ore and iron ore having a high zinc concentration.

[Brief description of the drawings]

FIG. 1 is a process chart of an embodiment of a method for recovering zinc in dust according to the present invention.

FIG. 2 is a diagram showing a particle size distribution of raw material dust and reactive dust.

FIG. 3 is a diagram showing a particle size distribution of dust collected by a dust collector.

FIG. 4 is a process chart showing a conventional method for recovering zinc in ironmaking dust.

[Explanation of symbols]

 21: Dust hopper 22: Raw material dust 23: Coke hopper 24: Coke 25: Binder hopper 26: Binder 27: Blender 28: Agglomerator 29: Intermediate hopper 30: Quantitative feeder 31: Melting furnace 31a: Furnace lid 31b : Duct 32: Molten iron 33: Agglomerated dust 34: First dust collector 35: Second dust collector 36: Third dust collector 37: Exhaust fan 38: Product hopper 39: Product compactor 40: Recycling line 41: Recirculated dust

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI C22B 19/34 C22B 19/34 (72) Inventor Noboru Sakamoto 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. ( 56) References JP-A-53-122604 (JP, A) JP-A-4-2734 (JP, A) JP-A-4-99231 (JP, A) JP-A-5-312485 (JP, A) Hei 7-70662 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22B 19/30 C21C 5/28 C21C 5/40 ZAB C21C 5/52 C22B 7/02 C22B 19/34

Claims (4)

(57) [Claims] An ironmaking dust containing zinc oxide is agglomerated dust, and the agglomerated dust is put into molten iron held in a melting furnace, and iron oxide and zinc oxide in the agglomerated dust are added to the molten iron. A method for recovering zinc oxide, comprising the steps of: evaporating the reduced zinc, and sucking and recovering the reduced zinc as zinc oxide, wherein the method comprises the following steps: . (A) sucking dust generated from the melting furnace, and collecting zinc oxide in order to collect zinc oxide; (b) collecting dust in a stepwise manner from dust having a large particle diameter; Certain dust is recycled again as a raw material of the agglomerated dust, and (c) dust containing zinc oxide in a predetermined content or more of the dust is recovered as a zinc raw material. 2. The method for recovering zinc oxide according to claim 1, wherein
In the stage, the particle size of the dust from the melting furnace was mainly 10 μm.
2. The method according to claim 1, wherein m or more dust is collected, the second stage mainly collects dust of 5 μm or more, and the third stage mainly collects dust of 0.1 μm or more. For recovering zinc oxide from iron-making dust containing waste zinc oxide. 3. An apparatus for recovering zinc oxide from iron-making dust containing zinc oxide, comprising: (A) an agglomerating machine for converting iron-making dust containing zinc oxide into agglomerated dust, (b) a melting furnace for adding the agglomerated dust and holding molten iron for reducing the agglomerated dust, and (c) Two or more dust collectors for classifying dust containing zinc oxide generated by reducing zinc oxide and evaporating zinc in the melting furnace, in order of increasing particle diameter in the dust. 4. A dust collector among the two or more dust collectors, wherein a first dust collector mainly collects dust having a particle size of 10 μm or more from dust from the melting furnace, and a second dust collector mainly comprises five dust collectors.
It is a dust collector that collects dust of μm or more.
4. The apparatus for recovering zinc oxide from iron-making dust containing zinc oxide according to claim 3, wherein the dust collector is a dust collector that mainly collects dust of 0.1 μm or more.