JP3399224B2 - Recovery device for zinc oxide from steelmaking dust - Google Patents

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 dust (hereinafter referred to as iron-making dust) generated at an iron mill containing iron oxide as a main component and containing a low concentration of zinc oxide (ZnO). 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. In addition, 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.

[0003] In ironworks, iron and carbon are recovered from ironmaking dust and thus 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, dezincification equipment such as a wet cyclone separates into high-concentration zinc dust and low-concentration zinc dust, 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, in recent years, a considerable amount of scrap has been accumulated in Japan, 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 steelworks tends to increase as described above, a technique for actively recovering zinc from high-concentration zinc dust and recovering it as a zinc raw material for refining Is being considered. 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 the 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.

[0008] 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 issue how to efficiently concentrate the zinc to 50 wt% or more.

Japanese Unexamined Patent Publication (Kokai) No. 6-145830 discloses the following method for recovering zinc in iron-making dust. This technique will be described below with reference to the drawings.
FIG. 3 shows a process diagram of this technique.

Iron-making dust 2 stored in the hopper 1A
Is sent to the mixer 4 together with the binder in the binder hopper 3, mixed, pelletized by the pelletizer 5, pelletized by the pelletizer 5, cured by the rapid curing device 6, and dried by the drying device 7. The pellet 10 is put into the molten iron pan 9 at the same time as the molten iron 11, and the iron oxide in the pellet is
It reacts with carbon and silicon in the molten iron and is reduced and recovered in the molten iron as iron.

Zinc oxide in dust is reduced and vaporized by carbon in molten iron and oxidized in air to 10 μm.
The following fine zinc oxide particles are obtained. The zinc oxide particles are collected by the dust collector 13. In order to further increase the zinc concentration in the dust, the dust collected by the dust collector 13 is again subjected to the same operation as described above via the distributor 15. Thereby, the zinc concentration in the dust is concentrated to 50 wt% or more.

Further, JP-A-53-122604 discloses that the slag discharged from various metal refining furnaces and coke powder are both charged into an electric furnace or the like, and zinc existing as oxide in slag. And other metals are collected. In addition, JP-A-58
Japanese Laid-Open Patent Publication No. 185733 discloses a method of recovering zinc from steelmaking dust by charging the steelmaking dust and a reducing material into an induction reaction furnace and volatilizing and recovering metal such as zinc.

[0013]

The above-mentioned technique has the following problems. JP-A-6-145830
According to the publication, zinc is reduced in a hot metal ladle, but there is a problem that the speed of the reduction reaction is slow because the hot metal in the hot metal ladle is not particularly stirred. Further, since the hot metal ladle is not particularly equipped with a heating device, there is a problem that zinc in the ironmaking dust cannot be continuously reduced.

In the above method, it is necessary to repeat the reduction reaction 2-3 times until the zinc concentration in the dust reaches the target value. Therefore, there is also a problem that large-scale equipment is required for the iron-making dust to be processed.

Further, in the zinc reduction methods disclosed in JP-A-53-122604 and JP-A-58-185733, since high cost electric power is used, these processes are not so economical. There is no problem.

Therefore, according to the present invention, a portion of the collected dust that has reached a predetermined concentration is selectively recovered, only a portion that does not reach the predetermined concentration is processed again, and the operation is continuously performed. An object is to provide a method for efficiently recovering zinc from ironmaking dust and an apparatus for the same in a more economical manner.

[0017]

Means for Solving the Problems The inventors of the present invention charged iron-making dust containing zinc oxide into a reaction furnace equipped with a heating device and a stirring means, and reduced the iron oxide and zinc oxide in molten iron, It has been found that the reduced zinc can be vaporized and recovered as zinc oxide. Therefore, the inventors have invented a device for recovering zinc from iron-making dust more efficiently and more economically.

The first aspect of the present invention is to introduce agglomerated iron-making dust, heat the agglomerated dust to reduce it, recover the iron content into molten iron, vaporize the reduced zinc, and form zinc oxide. In the apparatus for recovering zinc oxide from iron-making dust, which comprises a reaction furnace for holding molten iron and a recovery means for recovering the zinc oxide, the reaction furnace heats agglomerated dust and the molten iron, and A device for recovering zinc oxide from iron-making dust is provided, which is provided with a means for stirring the molten iron. By providing the reactor with means for heating the agglomerated dust and the molten iron, and means for stirring the molten iron, the heat necessary for reducing the iron oxide and zinc oxide is supplied and continuously reduced. The reaction can continue. Further, by stirring the molten iron, the reduction reaction can be promoted more quickly.

A second aspect of the present invention is characterized in that the means for heating the molten iron and the means for stirring the molten iron are two or more heating burners provided in the upper part of the reactor, zinc oxide from ironmaking dust. To provide a recovery device. Since two or more heating burners using fuel are provided in the upper part of the reactor as a means for heating the molten iron and a means for stirring the molten iron,
It can process ironmaking dust more economically.

In a third aspect of the invention, the two or more heating burners are inclined at an angle of 50 to 80 degrees with respect to the radial direction on a horizontal plane with respect to the substantially circular cross section of the reactor, and with respect to the horizontal plane in a vertical cross section. A device for recovering zinc oxide from iron-making dust is provided, which is arranged at an angle of 20 to 45 degrees. The above-mentioned arrangement of the burners makes it possible to swirl the combustion gas on the molten iron surface to give a rotating motion to the iron-making dust charged therein to further promote the reduction reaction.

In a fourth aspect of the present invention, two or more dust collectors are provided as a recovery means for recovering the zinc oxide, and the first stage has a first dust collector.
Provided is a dust collector for collecting dust of 0 μm or more, and the second stage dust collector is a dust collector for collecting dust of 0.1 μm or more. The collecting means for collecting zinc oxide is composed of two or more dust collectors, the first stage is a dust collector for collecting dust of 10 μm or more, and the second stage is a dust collector for collecting dust of 0.1 μm or more. By using a dust collector, the former mainly collects dust mainly containing iron oxide, and the latter mainly collects dust having a high zinc oxide concentration, so that zinc oxide can be efficiently collected.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, iron-making dust is mixed with reducing carbon to be agglomerated, and the agglomerated dust is charged into molten iron in a reaction furnace. The charged agglomerated dust is accumulated in layers in the reaction furnace, receives heat from the hot metal in the reaction furnace, and zinc oxide is reduced by the carbon in the agglomerated dust from the lowest agglomerated dust in sequence. To be done.

This reduction reaction occurs in a high-temperature reducing atmosphere having an ambient temperature of 1000 ° C. or higher, and the reaction rate thereof is higher in a higher-temperature atmosphere. Therefore, it is essential to secure a high temperature in recovering zinc. However, when the ironmaking dust is put into the hot metal, the temperature of the molten iron decreases due to the sensible heat of the dust and the reduction reaction of zinc oxide and iron oxide. In addition, sensible heat of exhaust gas and heat radiated from the reaction furnace are added to this, and the temperature of the hot metal remarkably decreases, so it is difficult to secure a high temperature for zinc recovery if the reaction furnace is not equipped with any heating device. become.

In the present invention, a burner combustor is installed in the upper part of the reaction furnace, and a combustion gas formed by burning a fuel such as heavy oil or pulverized coal here is irradiated to the briquette of the iron-making dust to produce the iron-making steel. Supplies the heat required for dust processing. As a result, a situation where the temperature of the hot metal is lowered can be avoided, so that continuous large-scale treatment of iron-making dust becomes possible.

As the burner combustion device, a conventionally known heavy oil burner, propane burner, pulverized coal burner or the like can be used. The amount of fuel injected into the reactor is the amount of heat generated by its combustion, and is required for dust treatment such as the above-mentioned sensible heat of dust, heat of reduction reaction of zinc oxide and iron oxide, sensible heat of exhaust gas, and radiant heat of reactor It suffices if it is equal to the amount of heat, and is calculated from the heat balance.

For example, the amount of heat required for treating 1 ton of iron-making dust is about 900 Mcal from the heat balance calculation.
Is. Therefore, the fuel is heavy oil (heat value 10700 kca
1 / kg), the required amount of fuel is 170 kg, assuming that the heat generation efficiency effective for the reaction is 50%. Therefore, in this case, from the burner combustion device,
If 70 kg / h of heavy oil is injected and burned in the reaction furnace, for example, 1 ton / h of electric furnace dust can be continuously treated to recover zinc without lowering the temperature in the furnace.

As the reaction furnace for charging molten iron, any furnace such as a hot metal ladle, a ladle for tapping steel, or a dedicated ladle for treating dust may be used.

Such a reduction reaction of zinc oxide in the dust occurs mainly at the interface between the molten iron upper surface and the agglomerated dust such as briquettes and pellets deposited on the molten iron. Therefore, if the agglomerated dust of molten iron or iron-making dust deposited on the molten iron upper surface is agitated by some means to improve the mixing between the interfaces between the two, the reduction reaction rate that occurs at the agglomerated dust-molten iron interface Can be increased, and an increase in dust processing amount can be realized.

In the present invention, as means for stirring molten iron,
Further, a gas blowing device using porous brick or lance can be installed in the reaction furnace. This gas blowing device
It may be installed at the bottom of the reaction furnace to stir the molten iron in the reaction furnace from below, or may be provided at the top of the reaction furnace to stir the molten iron upper portion. As the stirring gas, an inert gas such as nitrogen or argon is mainly used.

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

Further, as a device for stirring the agglomerated dust, there is the above-mentioned burner combustion device. That is, by arranging a plurality of burner combustion devices, irradiating the agglomerated dust with the flame of the combustion gas that is formed and rotating the agglomerated dust accumulated on the upper surface of the molten iron in the circumferential direction, the molten iron and the agglomerate are agglomerated. The reduction reaction occurring at the interface of the formed dust can be improved.

According to the results of the basic test, the number of burner combustors for forming a burner flame and the installation angle required for rotating the agglomerated dust are 2-4 burner,
It was found that it is appropriate that the mounting angle θ is 50 to 80 degrees with respect to the radial direction. Fig. 2 shows the burner mounting angle. The burner structure can be determined by the viscosity of molten iron in the reaction furnace, the weight of agglomerated dust, and the cross-sectional area of the reaction furnace.

As another molten iron stirring device, there is a mechanical stirring device having a plurality of blades. By rotating the stirrer in the molten iron, the molten iron causes a circumferential motion, and the reaction speed can be improved.

When the dust produced by the reduction reaction is collected, the zinc concentration of the collected dust is much higher than that of the agglomerated dust as the raw material. However, the collected dust contains a part of the raw material dust and has a particle size of 10 μm or more, and this part has a low zinc concentration. The portion reduced to zinc oxide has a high zinc concentration, and the particle size of this portion is less than 10 μm.

Therefore, at least two or more dust collectors are provided, the first-stage dust collector collects dust having a particle size of 10 μm or more, and the second-stage dust collector has a particle size of less than 10 μm. Are collected and divided and collected according to the zinc concentration. Then, the collected dust having a low zinc concentration is returned to the treated dust,
It is desirable to recycle to increase the zinc concentration in the dust.

Further, in the present invention, a hydraulic additive is added to the ironmaking dust to agglomerate. The agglomerated dust contains about 1 to 5% of water, and if it is put into the reaction 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 reaction furnace is effectively used.

That is, the gas discharged from the reaction furnace is about 30.
The temperature is 0 ° C. or higher, and the amount thereof is proportional to the dust treatment amount, and 10,000 Nm ³ of gas is generated per 1 t of the dust treatment amount. From the viewpoint of thermal efficiency, it is desirable to send this gas to the agglomerated dust to be dried and preheated to be dried or preheated indirectly or directly.

[0038]

EXAMPLES Next, a method of recovering zinc in dust of the present invention will be described by way of examples with reference to the drawings.

The zinc-containing iron-making dust 22 stored in the dust hopper 21 is thoroughly mixed in the mixer 27 together with the reducing coke 24 stored in the coke hopper 23 and the binder 26 stored in the binder hopper 25. Then, with the agglomeration device 28, the diameter is 15 to 30 m.
m, and agglomerated into briquettes having a size of 10 to 20 mm.

This briquette is dried and preheated by the exhaust gas 38 in the drying and preheating device 29, and then is fed into the reaction furnace 32 by the fixed amount supply device 31 through the intermediate hopper 30. The molten iron 33 having a temperature of 1400 to 1600 ° C. is contained in the reaction furnace 32,
The specific gravity of the charged briquette 34 is 1.2 to 2.
Since it is 5 and smaller than molten iron, it is deposited in layers on the molten iron surface.

In order to prevent the temperature drop of the molten iron, the reaction furnace 3
On the upper part of 2, there are installed four burner combustors 35, which are inclined with respect to the radial method, from which heavy oil is injected and burned. In addition, the briquette deposited on the upper surface of the molten iron is moved by the kinetic force of the flame from the burner to improve the reaction rate. Further, at the bottom of the reaction furnace, there is a bottom blowing gas device 36, from which nitrogen gas 37 is blown in to stir the molten iron to further improve the reaction rate.

The iron oxide in the dust is mainly reduced by the carbon in the briquette and recovered as iron in the molten iron. Further, zinc oxide is reduced and evaporated by carbon in the dust, and is oxidized by oxygen in the air flowing into the furnace through an air inlet or the like provided in the upper lid of the reaction furnace 32. It becomes zinc oxide particles.
On the other hand, a part of the agglomerated raw material zinc-containing dust is pulverized by thermal shock, and is discharged to the outside of the system in an unreacted state.

These zinc oxide particles, unreacted dust and iron content are collected by a cyclone 39 which is a first dust collecting device for collecting particles having a particle size of 10 μm or more and a second dust collecting device for collecting particles having a particle size of 10 μm or less. It is collected by a cyclone 40.
The components of the dust collected by each dust collector are as shown in Table 1. In this embodiment, the target zinc concentration is 50 wt%
Because of the above settings, the dust collected by the second dust collector 40 is stored in the product hopper 41.

Further, since the dust collected by the first dust collector 39 is lower than the target zinc concentration, it is returned to the dust hopper 21 via the recycle line 44. The recirculated dust 45 is agglomerated again with the raw material dust 22 by the agglomerating device 28, is charged again into the reaction furnace 32, and is reduced on the molten iron 33.

In this way, the required minimum amount of dust can be recycled and the dust of high-concentration zinc can be efficiently collected. The collected dust is agglomerated by the agglomeration device 42 and delivered to a smelting maker, and the smelting maker processes the zinc oxide as a raw material to produce a zinc material.

[0046]

[Table 1]

[0047]

As described above, according to the present invention, the zinc-containing dust containing iron oxide as the main component is agglomerated and charged into the molten iron in the reaction furnace, and the iron oxide in the dust is melted in the molten iron. This is an apparatus for reducing and recovering in molten iron, reducing and vaporizing zinc oxide in the dust, and recovering vaporized zinc as zinc oxide.

In this apparatus, a burner combustion apparatus that heats and stirs dust and molten iron to prevent the temperature of molten iron from decreasing,
Equipped with a stirrer that stirs molten iron and two or more dust collection groups that collect dust in order from larger particle size, so high-concentration zinc can be collected with high efficiency and high productivity. Becomes

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a device for recovering zinc in dust according to the present invention.

FIG. 2 is a diagram showing a burner mounting angle of the zinc recovery apparatus according to the present invention.

FIG. 3 is a schematic view of a prior art 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: Preheating and drying device 30: Intermediate hopper 31: Fixed amount feeder 32: Reactor 33: Molten iron 34: Briquette 35: Burner combustion device 36: Bottom blowing gas device 37: stirring gas 38: Exhaust gas line 39: First dust collector 40: Second dust collector 41: Product hopper 42: Agglomeration device 43: Product dust 44: Recycle line 45: Recycled dust 46: Exhaust fan

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI // C21C 5/40 C21C 5/40 B (56) Reference JP-A-6-145830 (JP, A) JP-A-58- 185733 (JP, A) Metallurgical physics, Japan, The Japan Institute of Metals, September 30, 1964, 54-55

Claims (3)

(57) [Claims] 1. An agglomerated iron-making dust is charged, the agglomerated dust is heated and reduced, the iron content is recovered into molten iron, and the reduced zinc is vaporized to form zinc oxide. In a device for recovering zinc oxide from iron-making dust, which comprises a reactor for holding and a recovery means for recovering zinc oxide in the previous period, as the means for heating the agglomerated dust and the molten iron, and stirring the molten iron, An apparatus for recovering zinc oxide from iron-making dust, comprising two or more heating burners on the upper part of the reaction furnace. 2. The two or more heating burners are inclined at an angle of 50 to 80 degrees with respect to a radial direction on a horizontal plane with respect to a substantially circular cross section of the reactor, and 20 to 45 with respect to a horizontal plane on a vertical cross section. The apparatus for recovering zinc oxide from iron-making dust according to claim 1, characterized in that the apparatus is inclined. 3. A dust collector of two or more units is provided as a collecting means for collecting the zinc oxide, a dust collector for collecting dust of 10 μm or more is provided in the first stage, and a dust collector of the second stage is set to 0.
The zinc oxide recovery device from iron-making dust according to claim 1 or 2, wherein the dust collector is a dust collector that collects dust of 1 µm or more.