JPH09268332A - Apparatus for recognition zinc oxide from iron making dust - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recovering apparatus which continuously and efficiently recovers zinc raw materials of a high zinc concn. from iron making dust. SOLUTION: This recovering apparatus has a melting furnace 32 which is charged with the agglomerated iron making dust 22 and holds molten iron 33 for reducing the iron oxide and zinc oxide in the agglomerated iron making dust 22 and a recovering means for evaporating the reduced zinc and recovering the zinc as zinc oxide. In such a case, (a) the melting furnace 32 has an electrode device 35 for executing electric arc heating, (b) a stirring means for stirring the molten iron 33 and further (c) plural dust collectors 40, 41 for recovering the dust from the dust produced from the melting furnace 32 stepwise from the dust of larger grain sizes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recovery device for recovering zinc oxide from iron-making dust (hereinafter also simply referred to as dust) generated in an iron mill containing iron oxide as a main component and containing a low concentration of zinc oxide (ZnO). Regarding Hereinafter, the term “zinc” mainly includes zinc oxide although it includes metallic zinc.

[0002]

2. Description of the Related Art Ironmaking dust containing a large amount of iron oxide is generated from an ironworks that produces iron from iron ore, scraps and the like. Typical examples thereof include blast furnace dust and converter dust. The ratio of blast furnace dust and converter dust to the total amount of dust generated from steelworks 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. Moreover, the zinc concentration is 0.1 to 3 wt% in each case, and the form thereof is mainly zinc oxide although it contains a small amount of metallic zinc.

[0004] In ironworks, iron and carbon are recovered from ironmaking dust and are therefore recycled as raw materials for blast furnaces. However, since zinc causes a wall 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 a raw material for the blast furnace while ensuring stable operation of the blast furnace. is there. At present, the amount of zinc charged into the blast furnace is limited to 0.1 kg or less per ton of pig iron.

Therefore, in a steel mill, high-density zinc dust and low-concentration zinc dust are separated by dezincification equipment such as a wet cyclone, and only low-concentration zinc dust is recycled as a blast furnace raw material. On the other hand, although high-concentration zinc dust is landfilled, the amount of this type of dust is increasing, making it difficult to treat the dust.

On the other hand, a considerable amount of scrap has been accumulated in Japan in recent years, and the ratio of scrap as an iron source tends to increase in integrated steelworks from the viewpoint of effective utilization of resources. Moreover, the proportion of galvanized steel sheets in the scrap is increasing, and the amount of zinc in the raw materials at the ironworks tends to increase.

Recently, since the amount of zinc in the raw material in the ironworks tends to increase as described above, not only the high-concentration zinc dust is landfilled but also the zinc is positively recovered for refining. Techniques for recovering zinc as a raw material are being studied. In order to use it as a zinc raw material for refining, it is necessary to make the zinc concentration as high as possible, and the currently targeted zinc concentration is 50 wt%.

There are so-called electric furnace manufacturers in addition to the above-mentioned blast furnace manufacturers. The main components of electric furnace dust generated here are iron oxide and zinc oxide, each of which is iron oxide 20.
-30% and zinc oxide 15-25%. About 60% of the generated electric furnace dust is recycled as zinc raw material for smelting, but the remaining 40% is landfilled. Electric furnace dust is also used for smelting like blast furnace dust and converter dust. Expanded applications as a zinc raw material are desired.

[0009] Therefore, in order to recover zinc from the above-mentioned iron mill dust and use it as a zinc raw material for refining, it is an important subject how to efficiently concentrate the zinc to 50 wt% or more.

Japanese Unexamined Patent Publication No. 53-122604 discloses a method for recovering volatile components such as zinc in iron-making dust as shown in FIG. Hereinafter, this technique will be described with reference to FIG.

The reaction vessel 2 receives the reducing slag 1 discharged from the electric furnace, and the electrode 3 is inserted into this slag so that the slag does not lose its fluidity (1450-1500 ° C.).
Heat by energizing about. Coke powder and dust are previously formed into briquettes by a briquetting machine, and the briquettes are put into the reaction vessel to reduce volatile components such as zinc. At this time, the power from the electrode is adjusted to promote the above reaction,
Secure the flow of slag.

After the reaction is completed, the slag is discharged from the reaction vessel, crushed so that it can be easily used thereafter, magnetically separated, and magnetic substances such as steel are reused. Volatile components such as zinc generated by the above reaction are collected by the dust collecting hood 4 provided on the upper part of the reaction vessel and collected by the bag filter 5.

[0013]

The above-mentioned prior arts are:
It has the following problems. That is, for the slag components other than the volatile matter contained in the dust, a predetermined amount of dust is discharged from the reaction container after the treatment is finished, and the treatment is repeated. That is, since the batch type (batch type) dust processing method is used, there is a limitation in the amount of processing as compared with the continuous processing method.

Further, in order to recover the iron content in the slag, the steps of cooling → crushing → magnetic separation are required, so that thermal energy is lost and a great amount of equipment cost is required for processing, and processing time is increased. This is a very costly processing method due to its length and the like.

Further, in the above technique, the slag is stirred to accelerate the reaction, but the means is an electrode device. That is, the flow state of the slag is changed by adjusting the electric power applied to the electrode device, but at the same time, the temperature of the slag also changes when the added electric power is changed. For this reason, for example, if an attempt is made to ensure an appropriate flow state of the slag, the slag may reach a high temperature of 1500 ° C. or higher, which increases the power consumption per unit of electricity from the electrode device for dust treatment and the inner surface of the storage container. It is not an economical treatment process, as the refractory materials in 1) become heavily worn.

Further, in the above technique, volatile substances such as zinc are collected by a bag filter. However, in the case of zinc recovery from dust, if the concentration is 50% or more, it is sold to a refining manufacturer as crude zinc oxide. It is currently difficult to do so. In particular, since the iron manufacturing dust as a raw material has a low zinc concentration, it is difficult to obtain a zinc concentration of 50% or more in the volatile matter by the above-mentioned dust treatment method from the viewpoint of reaction time in the furnace. Therefore, in order to obtain a volatile matter having a zinc concentration of 50% or more, it is necessary to mix the recovered volatile matter with the raw material dust and perform the dust treatment again.

The present invention has been made in order to solve the above-mentioned problems, and zinc-containing dust is reduced and vaporized continuously and in a large amount by a simple processing device to efficiently and highly concentrate the dust. To recover zinc oxide dust.

[0018]

A first invention is a melting furnace for charging agglomerated iron-making dust and holding molten iron for reducing iron oxide and zinc oxide in the agglomerated iron-making dust. In a device for recovering zinc oxide from iron-making dust, comprising: (a) an electrode device in which the melting furnace performs electric arc heating; And a stirring means for stirring the molten iron,
Further, (b) the device for recovering zinc oxide from iron-making dust, characterized in that the recovery means comprises a plurality of dust collectors for recovering dust in stages from dust having a large particle size.

A second aspect of the invention is a device for recovering zinc oxide from iron-making dust, characterized in that the stirring means for stirring the molten iron is stirring gas blowing means provided at the bottom of the melting furnace.

In a third aspect of the invention, the stirring gas is blown into the stirring gas by 2-10 Nm ³ / h per 1 ton of molten iron by the stirring gas blowing means.
It is a device for recovering zinc oxide from iron-making dust, which is characterized by blowing.

In a fourth aspect of the invention, among the plurality of dust collectors, the first-stage dust collector mainly collects dust having a particle size of 10 μm or more from the dust from the melting furnace, and the second-stage dust collector is mainly It is a dust collector for recovering dust of 0.1 μm or more, and is a device for recovering zinc oxide from iron-making dust.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, iron-making dust containing zinc is mixed with reducing carbon such as coke powder,
Agglomerate, and the agglomerated dust is put into molten iron in the melting furnace. The charged agglomerated dust is deposited in layers in the melting furnace, receives heat from the molten iron containing hot metal in the melting furnace (iron bath with a carbon content of 2 wt% or more), and the agglomerated dust in the bottom layer. From then on, zinc in the agglomerated dust reduces zinc oxide in the dust.

That is, the zinc oxide in the dust is rapidly reduced by the adjacent carbon to generate zinc vapor, and then immediately reoxidized in the space with a high oxygen partial pressure in the upper part of the melting furnace to obtain high-concentration zinc oxide. , Recovered. On the other hand, the iron oxide in the dust is reduced and recovered as iron in the molten iron.

The slag and molten iron produced by the above dust treatment can be discharged outside the system at any time by increasing the amount thereof by a method such as tilting the melting furnace. If molten iron is present, continuous treatment is possible. The generated molten iron has only a small heat loss corresponding to the amount of heat dissipated to the outside, and almost again with its sensible heat,
As a raw material for steelmaking, it can be put into an electric furnace and reused.

In the present invention, the high temperature required for dust treatment is secured by the arc heat generated from the electrode device. The electric power input to the electrode device is necessary for external heat loss such as exhaust gas sensible heat and smelting furnace heat dissipation, and dust processing such as dust sensible heat and reduction reaction heat of zinc oxide and iron oxide. It suffices to input the same amount of heat as the amount of heat, and it can be calculated from the heat balance.

For example, the amount of heat required in the melting furnace is 700 kwh with respect to the amount of treated dust: 1 t / h, the heat loss to the outside is 2500 kwh, and a total of 3200 kwh of power should be supplied. The dimensions of the melting furnace are, for example, inner diameter x height:
2.6 m × 2.8 m, molten iron weight: 100 tons,
Dust throughput: 1 t / h.

The reduction reaction of zinc oxide in the dust occurs mainly at the interface between the molten iron and the agglomerated dust deposited on the molten iron. Therefore, if the agglomerated dust of the ironmaking dust deposited on the upper surface of the molten iron is agitated by some means to improve the mixing between the interfaces between the two, the reduction reaction rate generated at the agglomerated dust-molten iron interface is increased. As a result, an increase in the amount of dust processed can be realized.

In the present invention, as means for stirring molten iron,
A gas blowing device is installed in the melting furnace. This gas blowing device is installed at the bottom of the melting furnace to agitate the molten iron in the melting furnace from below, or installed at the top of the melting furnace to agitate the upper portion of the molten iron. As the stirring gas, an inert gas such as nitrogen or argon is mainly used.

For example, in the case of a bottom-blown gas apparatus for stirring from the bottom of molten iron, the amount varies depending on the amount of molten iron, but as a result of a stirring test, it was found that 2 to 10 Nm ³ / h is appropriate per 1 ton of molten iron. Obtained. The nozzle may have a structure in which a plurality of porous porous bricks or small diameter tubes are bundled.

As another molten iron stirring device, there is a mechanical stirring device, and by rotating a stirrer having a plurality of blades in the molten iron, a circumferential motion of the molten iron is generated and the reaction rate can be improved. As described above, the amount of heat required for the reaction and the stirring force of the molten iron can be independently adjusted by different factors, and the dust can be efficiently reduced.

Further, in the present invention, a hydraulic additive is added to iron-making dust to agglomerate. This agglomerated briquette contains about 1 to 5% of water, and when it is put into the melting furnace as it is. The heat is consumed due to the heat of vaporization and the temperature rise. Therefore, in order to improve the thermal efficiency of the entire processing apparatus, the sensible heat of the gas discharged from the melting furnace is effectively used.

Specifically, the gas discharged from the melting furnace has a temperature of about 300 ° C. or higher, and its amount is proportional to the amount of dust treated, and 10,000 Nm ³ of gas is generated per 1 t of treated dust. This gas is sent to a drying and preheating device such as a briquette that is agglomerated dust, and is indirectly or directly dried and preheated.

The dust generated from the melting furnace is
The zinc concentration is much higher than that of the agglomerated dust, which is the raw material. However, there is a portion where the agglomerated dust that is the raw material is discharged from the melting furnace as it is, and this portion usually has a particle size of 10 μm or more and has a low zinc concentration. On the other hand,
The area where reduced zinc becomes zinc oxide is usually 10 μm
And the zinc concentration is high.

Therefore, at least two or more units are installed, and the first-stage dust collector mainly collects particles having a particle size of 10 from dust from the melting furnace.
The dust collector of the second stage mainly collects dust of 0.1 μm or more. By disposing such a dust collector, the dust is separated and collected according to the zinc concentration, and the collected dust having a low zinc concentration is recycled and returned to the treated dust, and zinc in the dust is collected. The concentration can be increased to collect dust. As such a dust collector, for example, a dry cyclone is suitable.

[0035]

EXAMPLES Next, a device for recovering zinc in dust according to the present invention will be described with reference to FIG. 1, which is an example. FIG. 1 is a schematic view of a device for recovering zinc in dust according to the present invention.

The zinc-containing raw material dust 22 stored in the dust hopper 21 is thoroughly mixed in the mixer 27 with the reducing coke 24 added to the coke hopper 23 together with the binder 26 stored in the binder hopper 25. It The mixture is agglomerator 28, diameter 15
It is agglomerated into a briquette having a size of about 30 mm and a thickness of about 10 to 20 mm.

This agglomerated dust is dried and preheated 29
After being dried and preheated by the exhaust gas 39,
After being fed through the intermediate hopper 30, a fixed amount is fed into the melting furnace 32 by a fixed amount feeder 31. The melting furnace 32 contains molten iron 33 having a temperature of 1400 to 1600 ° C., and the charged briquette 34 has a specific gravity of 1.2 to
Since it is 2.5, which is smaller than that of the molten iron 33, it is deposited in layers on the surface of the molten iron.

In order to prevent the temperature of the molten iron 33 from decreasing, an electrode device 35 is installed above the melting furnace 32. An arc is generated from this electrode device 35, and heat is supplied to the melting furnace 32 by its heat. Further, at the bottom of the melting furnace, there is a bottom blowing gas device 37, from which nitrogen gas 38 is jetted to stir the molten iron, which also contributes to the improvement of the reaction rate.

The iron oxide in the dust is mainly reduced by the carbon in the briquette and recovered in the molten iron as iron. Further, zinc oxide is reduced by carbon in the dust and evaporated, and is oxidized by oxygen in the air flowing into the furnace from an air inlet provided in the upper lid of the melting furnace 32, etc. Zinc oxide particles.

On the other hand, the zinc-containing dust, which is the agglomerated raw material, is partially pulverized by the thermal shock from the molten iron 33 and discharged out of the system without being reacted. In addition, iron oxide is partly discharged from the surface of the molten iron to the outside of the system.

The zinc oxide particles, the unreacted dust and the iron content are the first dust collecting device 40 which is a dry cyclone that collects a particle size of 10 μm or more, and the dry cyclone that collects a particle size of less than 10 μm. It is collected by the second dust collector 41. The components of the dust collected by each dust collector are as shown in Table 1. In this embodiment, the target zinc concentration is set to 50% or more, so the dust collected by the second dust collector 41 is stored in the product hopper 42.

Further, since the dust collected by the first dust collector 40 is lower than the target zinc concentration, it is returned to the dust hopper 24 through the dust recycle line 45. The recirculated dust 46, together with the raw material dust 22, is agglomerated again by the agglomerating device 28, charged again into the melting furnace 32, and reduced on the molten iron 33.

In this way, the required minimum amount of dust can be recirculated, and the high-concentration zinc dust can be efficiently recovered. The collected dust is agglomerated by the agglomeration device 43 and delivered to a refining maker, and the refining maker re-produces a zinc material using this zinc oxide as a raw material.

[0044]

[Table 1]

[0045]

As described above, the device of the present invention is
Iron-making dust mainly composed of agglomerated iron oxide is charged into molten iron, iron oxide in the dust is reduced in molten iron, and recovered in molten iron, and zinc oxide in the dust is removed. It is a zinc oxide recovery device equipped with a melting furnace for reduction and vaporization, and a means for recovering zinc in dust. Furthermore, since this device is equipped with an electrode device that heats dust and molten iron to prevent the temperature of molten iron from decreasing, and a gas blowing device that agitates molten iron and promotes the reduction reaction, it is possible to obtain high-concentration zinc with high efficiency. so,
In addition, it is possible to recover with high production.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a device for recovering zinc in iron-making dust according to the present invention.

FIG. 2 is a diagram showing a conventional device for recovering zinc in dust.

[Explanation of symbols]

 21: Dust hopper 22: Raw material dust 23: Coke hopper 24: Coke 25: Binder hopper 26: Binder 27: Mixer 28: Agglomeration device 29: Drying / preheating device 30: Intermediate hopper 31: Quantitative feeder 32: Melt Furnace 33: Molten iron 34: Briquette 35: Electrode device 36: Power supply device 37: Bottom blowing gas device 38: Agitation gas 39: Exhaust gas line 40: First dust collector 41: Second dust collector 42: Product hopper 43: Lump Compounding device 44: Product dust 45: Recycle line 46: Recycled dust 47: Exhaust fan

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Claims (4)

[Claims] 1. A melting furnace for holding agglomerated iron-making dust, holding molten iron for reducing iron oxide and zinc oxide in the agglomerated iron-making dust, and vaporizing the reduced zinc. A device for recovering zinc oxide from iron-making dust, comprising: a recovering device for recovering zinc oxide, comprising: (a) an electrode device in which the melting furnace performs electric arc heating, and a stirring device for stirring the molten iron. Furthermore, (b) a device for recovering zinc oxide from iron-making dust, characterized in that the recovery means comprises a plurality of dust collectors for recovering dust from large dust particles in stages. 2. An apparatus for recovering zinc oxide from iron-making dust, wherein the stirring means for stirring the molten iron is a stirring gas blowing means provided at the bottom of the melting furnace. 3. A device for recovering zinc oxide from iron-making dust, wherein the stirring gas blowing means blows the stirring gas at 2 to 10 Nm ³ / h per 1 ton of molten iron. 4. The first stage dust collector of the plurality of dust collectors mainly collects dust having a particle size of 10 μm or more from the dust from the melting furnace, and the second stage dust collector mainly collects 0.1 μm.
The device for collecting zinc oxide from iron-making dust according to any one of claims 1 to 3, which is a dust collector for collecting the above dust.