KR20130028755A - Method and apparatus for recovering metal from electric furnace dust - Google Patents

Abstract

A metal recovering method and apparatus from a converter dust which can realize metal recovery with high efficiency without causing problems such as clogging of the apparatus are obtained.
The metal recovering apparatus from the converter dust of the present invention is a metal recovering apparatus 1 (1) for recovering molten iron and zinc oxide by melting and reducing mainly electrical dust with a total mass% of chlorine and zinc of 12% , A secondary combustion chamber 5 in which an upward flow of the rising gas flow of the exhaust gas from the melting and reducing furnace 3 is 0.5 m / s or more and 2.0 m / s or less, An assembly dust collecting device 7 for collecting the assembled dust precipitated at the lower portion of the combustion chamber 5 and a fine dust collecting device 9 provided at the exhaust gas outlet side of the secondary combustion chamber 5 for recovering fine dust Respectively.

Description

[0001] METHOD AND APPARATUS FOR RECOVERING METAL FROM ELECTRIC FURNACE DUST [0002]

The present invention relates to an electric furnace for producing a steel material by using scrap, reduced iron or cast iron as a raw material and melting them to form a steel material) (Hereinafter referred to as " electric dust dust ") generated in an electric furnace (for example, an arc furnace for steelmaking) .

Converter dust generated from converters made of steel scrap as the main raw material is 2 to 7% chlorine in addition to 20 to 30% iron oxide and 10 to 30% zinc oxide. ).

A rotary kiln is widely used to recover zinc from this converter dust. In the process using such a rotary kiln, the converter dust and the reducing agent are heated in the furnace to generate a metal zinc vapor, and the zinc vapor in the exhaust gas is oxidized to form fine particles of zinc oxide, Thereby recovering zinc.

In this method, however, the reduction of iron is insufficient, and about 1 to 3% of zinc remains in the partially reduced iron oxide. It is necessary to raise the heating temperature of the raw material to the melting temperature of iron oxide or more in order to completely reduce the iron content and to achieve high efficiency of separation of zinc. However, when raising the heating temperature, it is difficult to discharge the semi-molten product from the reduction equipment have.

Separately, a process has also been proposed in which the converter dust is completely melted to recover iron powder as molten iron, and zinc is recovered as fine zinc oxide particles in the exhaust gas. Japanese Unexamined Patent Publication No. 3317137 discloses an example of a " zinc oxide recovery apparatus from steel dust " (see Patent Document 1).

In this process, part of the raw material dust supplied is scattered from the furnace as exhaust gas together with the zinc oxide fine particles without being melted and reduced.

In the "apparatus for recovering zinc oxide from iron oxide dust" disclosed in Patent Document 1, a primary dust collector 40 is provided for separating the converter dust before melting and returning it to the raw material. Further, a second dust collector 41 is provided downstream of the first dust collector to recover fine particles of zinc oxide.

Patent Document 1: Japanese Patent No. 3317137

The dust collecting device of the exhaust gas treating facility described in the above Patent Document 1 is described as, for example, a dry cyclone (dry cyclone).

However, in actual facilities, continuous operation of such a dust collecting apparatus is difficult because of high concentration of chlorine in the exhaust gas. The reason for this is as follows.

2-7% of chlorine in converter dust exists as metal chlorides such as ZnCl ₂ , NaCl, KCl, etc. At the temperature where the converter dust is melted and the iron oxide or zinc oxide is reduced, these metal chlorides are vaporized and discharged from the melting furnace together with the exhaust gas. Table 1 shows the melting point temperature and boiling point temperature of the metal chloride at atmospheric pressure.

Table 1

As can be seen from the above table, the condensation (liquefaction) and solidification of the metal chloride occur during the process of cooling the exhaust gas to remove dust, and the condensed (liquefied) or solidified metal chloride is introduced into the exhaust gas treatment facility So that the exhaust gas treatment facility is blocked.

In addition, the exhaust gas contains a high concentration of carbon monoxide (CO) gas by the metal reduction reaction in the reduction furnace, and this carbon monoxide needs to be burned by the secondary air to be carbon dioxide (CO ₂ ) have. The exhaust gas temperature becomes a high temperature exceeding 1,300 DEG C due to secondary combustion, and a gas cooling device is required. However, in Patent Document 1, there is no description about the installation of a gas cooling device, Is not possible.

An object of the present invention is to obtain a metal recovering method and apparatus from a converter dust which can realize metal recovery with high efficiency without causing problems such as clogging of the apparatus.

(1) The metal recovering method from the converter dust according to the present invention is a metal recovering method for recovering molten iron and zinc oxide from a converter dust by melting and reducing mainly the electric power dust of the converter dust having a total mass% of chlorine and zinc of 12% As a recovery method,

The assembly dust settling down to the lower portion of the secondary combustion chamber so as to have an ascending flow rate of not less than 0.5 m / s and not more than 2.0 m / s in the ascending flow rate of the exhaust gas of the melting and reducing furnace in the secondary combustion chamber of the melting- And the fine dust is recovered as a raw material for zinc smelting.

(2) The metal recovering apparatus from the converter dust according to the present invention is a metal recovering apparatus for recovering molten iron and zinc oxide by mainly reducing electric dust by the electric energy of the converter dust having a total mass% of chlorine and zinc of 12% As a recovery device,

A secondary combustion chamber in which an ascending flow rate of the rising gas flow of the exhaust gas in the melting and reducing furnace is 0.5 m / s or more and 2.0 m / s or less; and a dust collection unit And a fine dust collecting device provided on the exhaust gas outlet side of the secondary combustion chamber for collecting the fine dust.

(3) Further, the metal recovering device from the converter dust according to the present invention is a device for recovering molten iron and zinc oxide from a converter dust by melting and reducing mainly electrical dust with a total mass% of chlorine and zinc of 12% A metal recovery apparatus comprising:

A secondary combustion chamber which is provided on the exhaust gas outlet side of the secondary combustion chamber so as to provide an upward flow of the upward flow of the exhaust gas in the melting and reducing path of 0.5 m / s or more and 2.0 m / s or less; And a fine dust recovery device for recovering the dust,

Characterized in that the secondary combustion chamber is disposed above the melting and reducing furnace such that at least 50% of the area of the secondary combustion chamber overlaps with the furnace of the melting and reducing furnace when viewed in plan view.

(4) In the above-mentioned (2) or (3), the fine dust collecting apparatus may further include a multitubular gas cooler having a downflow structure for cooling the exhaust gas discharged from the secondary combustion chamber, Wherein the multitubular gas cooler is cooled until the outlet temperature of the introduced exhaust gas becomes 600 ° C or less.

By setting the outlet temperature of the exhaust gas to 600 캜 or less, the main chlorides, NaCl and KCl, can be solidified and solidified on the inner surface of the tube-type gas cooler.

In the present invention, an assembly that sinks to the lower portion of the secondary combustion chamber in such a manner that an ascending flow rate of the exhaust gas of the melting and reducing furnace in the secondary combustion chamber of the melting and reducing furnace is 0.5 m / s or more and 2.0 m / Dust is recovered and separated, and the fine dust which is not settled is recovered as a raw material for zinc smelting. Therefore, problems such as clogging of the apparatus are not caused and the metal recovery of high efficiency can be realized. Further, It is effective. The assembled dust recovered by sinking to the lower part of the secondary combustion chamber may be recycled to the raw material system.

1 is an explanatory diagram of a metal recovery device from converter dust according to Embodiment 1 of the present invention.
2 is a graph showing particle size distribution ratios and cumulative ratios of fine dusts.
3 is a graph showing particle size distribution ratios and cumulative ratios of the assembled dust.
4 is a graph showing the settling velocity of particles in a gas.
5 is an explanatory diagram of a metal recovery apparatus from a converter dust according to Embodiment 2 of the present invention.

[Embodiment 1]

A metal recovery apparatus from a converter dust according to Embodiment 1 of the present invention will be described with reference to Fig.

The metal recovering apparatus 1 from the converter dust of the present embodiment is a metal recovering apparatus for recovering molten metal and zinc oxide by mainly reducing electric dust and dust of the converter dust having a total mass% of chlorine and zinc of 12% A recovery device (1) comprising a melting and reducing furnace (3) and a secondary combustion chamber (5) in which an upward flow of the rising gas of the exhaust gas in the melting and reducing furnace (3) is 0.5 m / A coarse dust collecting device 7 for collecting the coarse dust precipitated in the lower portion of the secondary combustion chamber 5 and an exhaust port 7 of the secondary combustion chamber 5 And a fine particle dust collecting device (9) installed on the side of the dust collecting device (28) for collecting fine dust.

<Melt Reduction Furnace>

The melting and reducing furnace 3 is provided with a hopper 11 for inputting a reducing agent such as a converter dust and coke as raw materials and an electrode device 13 for preventing the temperature of the molten iron from dropping have. An arc is generated by the electrode device 13, thereby supplying heat to the melting and reducing furnace 3. A primary air inlet (15) for introducing primary air is formed in the melting and reducing furnace (3).

In the bottom of the melting and reducing furnace 3, a molten iron discharge port 17 for discharging molten iron and a slag discharge port 19 for discharging the slag are formed.

An exhaust gas outlet 21 is formed in the upper portion of the melting and reducing furnace 3. The exhaust gas outlet 21 communicates with the secondary combustion chamber 5 through the connection passage 23.

A first secondary combustion air inlet (25) for introducing secondary combustion air is formed in the connection passage (23).

<Secondary combustion chamber>

The secondary combustion chamber 5 is equipped with an exhaust gas inlet 27 through which the exhaust gas from the melt reduction path 3 flows in a lower portion thereof, and a vertical upward flow having an exhaust port 28 of the exhaust gas in an upper portion thereof. It has an upper structure. In the secondary combustion chamber 5, a second secondary combustion air inlet 29 for introducing secondary combustion air is formed.

The furnace wall of the secondary combustion chamber 5 is water-cooled (some refractory materials are also possible).

The secondary combustion chamber 5 is designed as a design guide for pyrolysis of dioxins in the gas so as to satisfy the condition of at least 2 seconds at 800 ° C or higher (internal distillation) .

An assembled dust collecting device 7 is provided in the lower portion of the secondary combustion chamber 5.

Particles in the exhaust gas flowing into the secondary combustion chamber 5 are a mixture of relatively rough assembled dust scattered by the converter dust as it is and fine dust (zinc oxide and metal chloride) precipitated by vapor phase precipitation .

In the secondary combustion chamber 5, since the flow rate of the ascending flow in the secondary combustion chamber 5 is set at a predetermined flow rate, the secondary combustion chamber 5 has a function of classifying the exhaust gas into relatively coarse dust and fine dust. In the method of setting the flow rate of the ascending current in the secondary combustion chamber 5 to a predetermined flow rate, the amount of exhaust gas flowing into the secondary combustion chamber 5 is controlled by the amount of the converter dust to be melted, the primary combustion air amount, So that the cross-sectional area of the secondary combustion chamber 5 is set to a predetermined value based on these values.

By appropriately setting the flow rate of the ascending flow of the exhaust gas in the secondary combustion chamber 5, the assembly dust mainly composed of the converter dust and the reducing agent coal powder falls to the lower portion of the secondary combustion chamber 5, The fine dust composed of metal chloride is taken out from the upper part of the secondary combustion chamber 5 by taking the air flow.

The assembled dust which has fallen to the lower portion of the secondary combustion chamber 5 is collected and separated by the assembled dust collecting device 7. On the other hand, the fine dust discharged from the upper part of the secondary combustion chamber 5 is recovered from the lower part of the multitubular gas cooler 35 or the bug filter 37.

The flow rate of the rising flow of the exhaust gas in the secondary combustion chamber 5 will be described.

FIG. 2 is a graph showing the particle diameter distribution ratio (particle diameter distribution ratio) and the cumulative proportion of fine dust mainly containing zinc oxide, wherein the abscissa represents the particle diameter (mm) and the ordinate axis on the left side represents the weight ratio %), And the vertical axis on the right side represents the weight percentage (%) of the cumulative value.

Fig. 3 is a graph showing the particle size distribution of the assembled dust containing iron oxide as a main component, wherein the abscissa represents the particle diameter (mm), the ordinate on the left side represents the weight percentage (%) of the particle size distribution, Weight ratio (%).

4 is a graph showing the settling velocity of the particles at 950 占 폚, which is a typical gas temperature in the secondary combustion chamber 5. The vertical axis represents the settling velocity (m / s) and the horizontal axis represents the particle diameter (mm) have.

According to the graph shown in Fig. 2, 90% of the weight of the fine dust is 0.1 mm or less in particle diameter. Therefore, in order to burn 90% or more of the particulate dust on the airflow without being settled and to be taken out from the upper part of the secondary combustion chamber 5, the ascending flow rate of the secondary combustion chamber 5 is set at a sedimentation rate suitable for the particle diameter of 0.1 mm good. This ascending velocity is 0.5 m / s or more from the graph of Fig.

Also, from the graph shown in Fig. 3, 90% of the weight of the assembled dust has a particle diameter of 0.22 mm or more. Therefore, in order to precipitate 90% or more of the assembled dust into the lower portion of the secondary combustion chamber 5 without scattering, it is sufficient to set the ascending flow rate to be lower than the settling velocity corresponding to the particle diameter of 0.22 mm. From the graph of Fig. 4, this speed is less than 2.0 m / s.

As a result, 90% or more of the fine dust is removed from the upper portion of the secondary combustion chamber 5 by classifying dust by gravity sedimentation in the secondary combustion chamber 5, In order to settling down to the lower portion of the secondary combustion chamber 5, the ascending flow rate in the secondary combustion chamber 5 may be set to 0.5 m / s or more and 2.0 m / s or less.

<Assembly dust collecting device>

The assembled dust collecting device 7 recovers the assembled dust accumulated in the lower portion of the secondary combustion chamber 5 in the lower portion of the secondary combustion chamber 5. [ More specifically, as shown in Fig. 1, a screw conveyor 31 provided at a lower portion of the secondary combustion chamber 5 and a dust-collecting outlet 33 for discharging the assembled dust conveyed by the screw conveyor 31 are provided . In addition to the method of continuously discharging the assembled dust collecting apparatus by a screw conveyor, a method of placing the collecting container at the lower part of the secondary combustion chamber 5 and taking out the entire container from time to time is also conceivable.

<Fine dust collecting device>

The particulate dust recovery device 9 recovers fine dust mainly composed of zinc oxide in the exhaust gas that is provided on the downstream side of the secondary combustion chamber 5 and is discharged from the secondary combustion chamber 5.

Concretely, a multi-tubular gas cooler 35 of a vertical downflow structure (vertical downflow structure) for cooling the exhaust gas flowing from the secondary combustion chamber 5 and a multi- And a bug filter 37 installed therein.

The multi-tubular gas cooler 35 has a structure in which a metal tube is installed in a water-cooled container (water-cooled container), and gas is passed through the inner surface of the tube to cool the gas. The temperature range of the multi-tube type gas cooler 35 is designed so that the inlet gas temperature is about 800 ° C. and the outlet gas temperature is not more than 600 ° C. (for example, about 400 ° C.) so that the chloride is solidified on the inner surface of the metal tube . Since most of the chlorine is preferentially bound to Na and K to form ZnCl ₂ , the outlet temperature of the multitubular gas cooler 35 does not need to be lowered to the coagulation temperature of ZnCl ₂ .

Since the multi-tubular gas cooler 35 has a vertically descending flow and a relatively high proportion of zinc oxide in the fine particles, adhesion and solidification of the chloride are not remarkable, and cleaning even when attached is easy.

The zinc oxide in the fine particles falls to the bottom of the shell-and-tube type gas cooler 35 and is recovered.

The gas discharged from the multi-tubular gas cooler 35 is cooled to 200 ° C or lower, which is capable of operating the bug filter 37 which is diluted by the atmosphere and disposed on the downstream side.

In the bug filter (37), zinc oxide in the fine particles not recovered in the multitubular gas cooler (35) is recovered.

A metal recovery method using the metal recovery apparatus 1 of the present embodiment configured as described above will be described.

In the melting and reducing furnace 3, a reducing agent such as a converter dust and coke is continuously supplied from the hopper 11. Such converter dust is heated and melted in the furnace by arc heating or resistance heating, and the metal oxide is reduced. The iron oxide in the converter dust is accumulated in the furnace as molten iron, and the zinc oxide is discharged as fine particles to the secondary combustion chamber 5 side.

The high temperature gas discharged from the melting and reducing furnace 3 includes unburned gas components such as carbon monoxide gas, reducing agent carbon powder, metal vapor and the like (unburnt burn components, metal chlorides, and scattering raw dust, etc.) in addition to the zinc oxide fine particles. The secondary combustion chamber 5 burns the unburned components in the secondary combustion chamber 5 by the secondary combustion air. As described above, the secondary combustion chamber 5 is structured to form a vertical upward flow so as to have a sufficient residence time, The dioxins in the gas are pyrolyzed.

Particles in the converter dust are a mixture of relatively coarse flyash material dust and fine dust (zinc oxide and metal chloride) due to vapor phase precipitation, and this dust is classified by the flow rate of the ascending flow in the secondary combustion chamber 5.

That is, the converter dust and the reducing dust, is dropped to the lower portion of the secondary combustion chamber 5 and is recovered in the assembly dust collecting device 7 and separated. The particulate dust taken out from the upper portion of the secondary combustion chamber 5 by the airflow is mainly composed of zinc oxide and metal chloride and is discharged to the lower portion of the multitubular gas cooler 35 on the downstream side of the secondary combustion chamber 5, 37).

As described above, according to the present embodiment, the metal can be recovered with high efficiency without causing problems such as clogging of the apparatus from the high-temperature exhaust gas from the melting and reducing furnace 3 containing the chloride of high concentration, The operation can be stabilized for a long time.

Embodiment 2

Embodiment 2 of the present invention will be described with reference to Fig. In Fig. 5, the same reference numerals are given to the same parts as those in Fig. 1 showing the first embodiment.

The metal recovering apparatus 41 from the converter dust according to the present embodiment is provided with the secondary combustion chamber 5 and the melting and reducing furnace 5 in order to return the assembled dust falling in the secondary combustion chamber 5 directly to the melting and reducing furnace 3, (3) are arranged so as to overlap when viewed in a plan view. Concretely, the secondary combustion chamber 5 is disposed on the upper portion of the melting and reducing furnace 3 so that at least 50% of the area of the secondary combustion chamber 5 in the plan view overlaps the furnace of the melting and reducing furnace 3 will be.

According to the present embodiment, since the assembled dust precipitated in the secondary combustion chamber 5 is returned directly to the melting and reducing furnace 3, It is not necessary to separately provide an assembled dust collecting device 7 for discharging the assembled dust collecting device 7 to the outside of the apparatus and returning the mixed dust collecting device 7 to the melting and reducing furnace 3 so that the structure of the apparatus is simplified and the assembled dust can be reliably recovered, This good metal recovery is realized.

[Example]

Specific basic specifications of the metal recovering device from the converter dust according to the first embodiment of Fig. 1 are shown below.

O Rated throughput dust throughput: 5ton / h

ㅇ Inner diameter: 4mφ

ㅇ Power capacity: 12MVA

ㅇ Secondary combustion chamber dimensions: 2.5mφ in inner diameter x 9m in height

ㅇ Tube type gas cooler Dimensions: tube diameter 0.3mφ x length 7m x 12

O the secondary combustion chamber exit gas temperature and: 6,500Nm ³ / hx 720 ℃

ㅇ Tube gas cooler outlet gas quantity and temperature: 6,500 Nm ³ / hx 390 ℃

Bug filter inlet gas volume and temperature: 15,000 Nm ³ / hx 180 ° C

ㅇ Yongchol recovered quantity: 1.25ton / h

ㅇ Zinc oxide (crude oxide lead) recovery: 2.0 ton / h

ㅇ ZnO in zinc ： 65 to 73%

ㅇ Continuous operation time: 3 ~ 5 days

1: Metal recovery device
3: melt reduction furnace
5: Secondary combustion chamber
7: Assembly dust collecting device
9: particle dust collector
11: hopper
13: electrode device
15: primary air inlet
17: Charge outlet
19: Slag outlet
21: Exhaust gas outlet
23:
25: First secondary combustion air inlet
27: Exhaust gas inlet
28: Outlet
29: Second secondary combustion air inlet
31: Screw conveyor
33: Assembly dust outlet
35: Multi-tube gas cooler
37: BUG FILTER
41: Metal recovery device

Claims (4)

It is possible to recover molten iron and zinc oxide by melting reduction of converter dust whose total mass percentage of chlorine and zinc is 12% or more by electric energy. As a metal recovery method from converter dust,
(Ascending flow rate) of the exhaust gas of the melting and reducing furnace in the secondary combustion chamber of the melting and reducing furnace (melting reduction furnace) is 0.5 m / s or more and 2.0 m / s or less (Dust) precipitated in the lower portion of the secondary combustion chamber is collected and separated from fine dust which does not settle, and fine dust is recovered as a raw material for zinc smelting Wherein the metal dust is recovered from the dust collector.
As a metal recovery device from converter dust which melt-reduces converter dust whose total mass% of chlorine and zinc is 12% or more mainly by electric energy, and recovers molten iron and zinc oxide,
A secondary combustion chamber in which an ascending flow rate of the rising gas flow of the exhaust gas in the melting and reducing furnace is 0.5 m / s or more and 2.0 m / s or less; and a dust collection unit And a fine dust collecting device provided on an exhaust gas outlet side of said secondary combustion chamber for collecting fine dust.
A metal recovery device from converter dust that recovers molten iron and zinc oxide by melting and reducing converter dust whose total mass% of chlorine and zinc is 12% or more by electric energy,
A secondary combustion chamber which is provided on the exhaust gas outlet side of the secondary combustion chamber so as to provide an upward flow of the upward flow of the exhaust gas in the melting and reducing path of 0.5 m / s or more and 2.0 m / s or less; And a fine dust recovery device for recovering the dust,
Wherein the secondary combustion chamber is disposed above the melting and reducing furnace such that at least 50% of the area of the secondary combustion chamber overlaps the inside of the furnace of the melting and reducing furnace in plan view.
The method according to claim 2 or 3,
Wherein the fine dust collecting device comprises a multitubular gas cooler of a downflow structure (downflow structure) for cooling the exhaust gas discharged from the secondary combustion chamber, wherein the multitubular gas cooler Is cooled until the outlet temperature of the introduced exhaust gas becomes 600 캜 or less.

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