JPH09241718A - Method for recovering zinc oxide from zinc oxide-containing dust - Google Patents

Abstract

(57) [Abstract] An object of the present invention is to efficiently recover dust having a high concentration from zinc oxide-containing dust such as iron-making dust. SOLUTION: Zinc oxide-containing dust is agglomerated, charged into a melting furnace containing molten iron, iron oxide in the dust is reduced in the molten iron and recovered in the molten iron, and In a method for recovering zinc in dust, which reduces zinc oxide to zinc and recovers vaporized zinc as zinc oxide, a reducing carbon material is mixed with the dust to form agglomerated dust, which is used in the melting furnace. The method for recovering zinc oxide from zinc oxide-containing dust is characterized in that The ratio of the carbon material for reduction to the dust,
The stoichiometric ratio of 1.5 to 1.5 required for the reduction of iron oxide and zinc oxide
It is desirable to make it 10 times. Further, in the agglomeration process of the zinc oxide-containing dust, it is desirable to mix a hydraulic additive with the dust in addition to the carbon material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering zinc oxide from zinc oxide-containing dust (hereinafter simply referred to as "dust"), and particularly to the efficient production of zinc oxide from dust (hereinafter referred to as "iron-making dust") generated in ironworks Regarding how to collect well.

[0002]

2. Description of the Related Art Blast furnace dust or converter dust containing a large amount of iron is generated from an iron mill that produces iron ore or scrap as a raw material. The ratio of blast furnace dust and converter dust to the total amount of iron dust generated from the steel mill reaches 60% or more. The main components of blast furnace dust are coke and iron oxide, and the main components of converter dust are iron oxide. In addition, the zinc concentration is 0.1 to 3 in all cases.
wt% and its form is zinc oxide.

In an iron mill, a zinc oxide (hereinafter simply referred to as zinc) component is separated from a part of the above dust and then mixed with an iron ore raw material, or a small amount of iron production dust is mixed with a sintering raw material to produce zinc. After reducing the concentration, we are recycling dust as a raw material for blast furnaces.

As described above, ironmaking dust is recycled in ironworks, but when the zinc concentration in the dust increases with an increase in the amount of scrap used, the zinc component is separated and recovered from this dust. Therefore, the dezincification equipment such as a rotary kiln cannot be used, and the use as a sintering raw material is limited, so that the amount of iron-making dust that cannot be processed increases, and the recycling cannot be promoted. Therefore, efficient recovery of zinc in the ironmaking dust is a very important issue for smooth recycling of the ironmaking dust.

What is particularly important when recycling ironmaking dust as a raw material for a blast furnace is to strictly control the amount of zinc returned to the blast furnace in order to prevent the wall from sticking to the furnace wall. At present, the amount of zinc charged into the blast furnace is controlled to be 0.1 kg or less per ton of pig iron.

The above has referred to the current state of dust generated in ironworks that manufacture steel using iron ore, scrap, etc. as a raw material by using a blast furnace and a converter. On the other hand, scrap is used as a main raw material in an electric furnace. Steel mills that produce steel also have similar problems with dust disposal.

At present, a considerable amount of scrap has been accumulated in countries that consume large amounts of iron, and in the future, from the viewpoint of promoting the recycling of resources, steel mills have no choice but to further increase the amount of scrap used. Therefore, it is expected that the amount of zinc brought into the steelworks will further increase.

The amount of dust generated in the electric furnace is about 500,000 tons per year. Of these, 60% is recycled as a zinc raw material by various methods, but the other 40% of untreated dust is currently used for landfill. However, due to environmental issues, it is expected that it will be difficult to reclaim land without treatment.

The main components of the electric furnace dust are iron oxide and zinc oxide, iron oxide 20 to 30% and zinc oxide 15 to 2, respectively.
Since it contains 5%, if this dust can be treated by some means to efficiently recover zinc together with iron at low cost, it is possible to reduce the volume of dust generated and to recycle valuable metals. As described above, efficient recovery of zinc content from ironmaking dust such as blast furnace dust, converter dust, and electric furnace dust generated from ironworks is a very important issue from the viewpoint of resource recycling.

Therefore, Japanese Patent Application Laid-Open No. 58-185733 discloses the following method for recovering zinc in dust. This will be described below with reference to the drawings. FIG. 2 is a schematic diagram showing this technique. In FIG. 2, 1 is a retort body composed of an induction type electric furnace, 1a is a tap hole, 1b is a lid plug, 2 is a lid part, 2a is a treated material supply port, 2b is a gas discharge port, 3 is a condenser, 4 is a prolong,
Reference numeral 4a is a gas outlet of prolong, 5 is an object supply hopper, 6 is a heat medium layer, 7 is an object to be processed, and 8 is liquid zinc.

According to this technique, at the start of the operation, the starting block is melted in the retort body of the induction type electric furnace 1 to be used as a heat medium, and the remaining hot water is used as a heat medium after the next time. On the heat medium 6 formed in this way,
An object to be treated 7 in which dust and coke breeze are mixed in a ratio of 7: 3 is supplied from a supply hopper 5. As a result, zinc oxide in the dust is reduced to zinc vapor, and this zinc vapor is sent together with carbon monoxide gas and carbon dioxide gas from the gas outlet 2b to the condenser 3, cooled and liquefied,
It is recovered as liquid zinc 8.

A part of the zinc that could not be liquefied in the condenser 3 is recovered as zinc powder in the prolong 4 and the exhaust gas is exhausted to the atmosphere from the gas exhaust port 4a of the prolong 4. Further, the iron oxide in the dust absorbs carbon and melts during the reduction, and is separated from the slag to become molten iron. In this way, molten iron and slag as the heat medium account for about 80% of the furnace volume.
The molten iron is recovered by tilting the furnace body when the temperature has increased to a certain degree, leaving the next heat medium in the furnace, and discharging the increased amount of hot water.

[0013]

The above-mentioned prior arts are:
It has the following problems. That is, since the agglomerated iron-making dust and the reducing coke are separately charged into the melting furnace, the reduction reaction of zinc oxide in the dust is unstable, and high-purity zinc cannot always be obtained. Further, even if the reduction reaction is performed, it takes a considerable time to complete the reaction.

Further, in the above zinc concentration method, the generation of unreacted dust mainly composed of iron oxide is inevitable in addition to zinc, so that the purity of zinc powder has an upper limit, and it is difficult to produce high-purity zinc. . Therefore, the present invention has been made to solve the above problems, and to reduce and vaporize zinc oxide-containing dust by a simple treatment method to efficiently recover high-concentration zinc oxide. It is in.

[0015]

According to the present invention, zinc oxide-containing dust having iron oxide as a main component is used as agglomerated dust, and when reducing in molten iron, the dust is mixed with a reducing carbon material. The inventors have come to the invention described below based on the finding that zinc oxide can be more efficiently reduced by charging it into molten iron as agglomerated dust.

A first aspect of the invention is to agglomerate zinc oxide-containing dust, charge it in a melting furnace containing molten iron, reduce the iron oxide in the dust in the molten iron, and recover it in the molten iron. In the method for recovering zinc in dust by reducing zinc oxide in the dust to zinc and recovering vaporized zinc as zinc oxide, a reducing carbon material is mixed with the dust to form agglomerated dust. Provided is a method for recovering zinc oxide from zinc oxide-containing dust, which comprises charging agglomerated dust into molten iron in the melting furnace.

In a second aspect of the present invention, in the above-mentioned aspect, the ratio of the carbon material for reduction to the dust is 1.5 to 10 times the stoichiometric ratio required for reducing iron oxide and zinc oxide. A method for recovering zinc oxide from zinc oxide-containing dust is provided.

A third invention is the above invention, wherein a zinc oxide-containing dust is mixed with a hydraulic additive in the agglomeration process of the zinc oxide-containing dust, and the zinc oxide-containing dust is recovered from the zinc oxide-containing dust. Provide a way.

In a fourth aspect of the present invention, when the hydraulic additive is mixed, the slag generated in the melting furnace has a basicity (CaO / SiO) of 0.5 to 1.5. Provided is a method for recovering zinc oxide from zinc oxide-containing dust, which comprises mixing a hydraulic additive.

In a fifth aspect based on the above aspect, the charging amount of the agglomerated dust is 0.
Provided is a method for recovering zinc oxide from zinc oxide-containing dust, which is characterized in that it is ² to 1.0 t / h · m ² .

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION In the above-mentioned prior art, when the iron-making dust and the reducing carbon material are separately granulated and put into the melting furnace, the dust to be reduced and the reducing carbon material are not necessarily close to each other. Because of the situation, it cannot be said that the reduction reaction of zinc oxide in the dust proceeds stably and quickly.

On the other hand, in the present invention, the zinc oxide-containing dust is mixed with the reducing carbon material to be agglomerated, and the agglomerated dust is melted iron (carbon content: 2 to 4 wt%) in the melting furnace. Added to. The charged agglomerated dust is deposited in layers in the melting furnace, receives heat from the molten iron in the melting furnace, sequentially from the lowermost agglomerated dust, by the carbon material in the agglomerated dust,
Iron oxide and zinc oxide in the dust are reduced.

That is, the zinc oxide in the dust is rapidly reduced by the adjacent carbon material 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 a high concentration of oxidation. Recovered as zinc. Therefore, according to the present invention, it is possible to achieve a dramatic increase in the amount of iron dust produced.

Here, it is necessary for the melting furnace to continue the reduction reaction which is an endothermic reaction and maintain the temperature of the molten iron at about 1500 ° C. Therefore, it is necessary to compensate for the heat. This heat may be compensated by any method, but may be induction heating, arc heating or gas heating. However, a method that is relatively simple and easy to heat is induction heating.

As the carbon material, for example, coke powder,
Petroleum coke can be used. When the ratio of the carbon material for reduction is smaller than this, the reduction reaction is delayed and the ratio of unreduced dust increases. On the contrary, even if the ratio of the carbon material for reduction is made larger than this, as a result of the surplus carbon material being mixed into the slag, the slag foams and does not contribute to the improvement of the reduction reaction.

Next, regarding the amount of carbon material added to the agglomerated dust, if the ratio of the reducing carbon material is small, the amount of the zinc oxide reducing carbon material will be insufficient, so the concentration of zinc oxide in the generated dust will be low. Suppressed. In the present invention, the ratio of the carbonaceous material contained in the dust is 1.5 which is the stoichiometric ratio required for the reduction of zinc oxide and iron oxide.
It has been confirmed that the reduction reaction proceeds rapidly and stably by setting the ratio to 10 times.

In the agglomeration process of the dust,
A hydraulic additive is added as a binder, and an additive containing CaO is used as the hydraulic additive. When dust is agglomerated with a hydraulic additive, agglomeration is easy and economical.

Although a small amount of slag components such as silica and alumina are contained in the dust, these are dissolved and formed between the unreacted agglomerated dust and the upper surface of the molten iron. When the fluidity of the generated slag deteriorates, the chance of contact between the unreacted agglomerated dust and molten iron decreases, and as a result, the reduction reaction does not proceed rapidly.

Therefore, in the present invention, an additive containing CaO is used as the hydraulic additive, and the basicity (CaO / SiO2) of the produced slag is in the range of 0.5 to 1.5, preferably Adjust to 1.0 to 1.2, and set the melting point of slag to 15
The fluidity of the slag is secured by setting the temperature to 00 ° C or less.

For example, Portland cement having a basicity of about 2 and blast furnace slag having a basicity of about 1.5 are suitable. The blending amount may be blended according to the component composition of the dust. The form of the agglomerated dust may be pellets or briquettes. Pellets produced with a normal pelletizer are relatively spherical in shape, so they are transported,
Convenient for charging.

Such a reduction reaction of zinc oxide in the dust mainly occurs at the interface between the molten iron upper surface and the agglomerated dust deposited on the molten iron. Therefore, the amount of dust charged is
It is considered that it depends on the furnace area above the molten iron where agglomerated dust accumulates. In the present invention, as a result of various dissolution tests, the proper charging speed of the agglomerated dust is 0.2-1.
The range of 0 t / h · m ² was appropriate.

When the charging rate of the agglomerated dust is further increased, unreacted agglomerated dust is gradually deposited on the molten iron upper surface, and the thickness of the agglomerated dust tends to increase. When the thickness of the agglomerated dust increases, the agglomerated dust on the top of the layer becomes
The radiant heat from the molten iron is blocked by the agglomerated dust in the lower part of the bed, and the reaction rate is suppressed and the reduction rate is reduced due to insufficient supply of heat to the agglomerated dust.

The dust generated from the melting furnace in the method of the present invention has a smaller particle size and a much higher zinc concentration than the iron-making dust which is a raw material of the agglomerated dust.
On the other hand, in the blast furnace dust, the zinc concentration is high in the small grain size portion, and the iron ore is mainly in the large grain size portion. That is, the zinc concentration is high in the portion of the ironmaking dust having a small internal particle diameter.

Therefore, the dust generated by the reduction treatment is separately collected by a dust collector having at least two units having different classification performances, and the collected dust having a low zinc concentration is recirculated, It is preferable that the dust is collected by returning it to the raw material dust to increase the zinc concentration in the dust.

[0035]

EXAMPLES Next, a method of recovering zinc in iron-making dust according to the present invention will be described with reference to an example of FIG. FIG.
FIG. 3 is a process chart of an embodiment of a method for recovering zinc in dust according to the present invention. The raw material dust 22 containing zinc stored in the dust hopper 21 is a reducing coke 24 added to the coke hopper 23 and a binder hopper 25.
After being sufficiently mixed in the mixer 27 with the binder 26 stored in the briquette machine 28 which is an agglomeration device.
Then, it is agglomerated into a briquette having a diameter of 15 to 30 mm and a thickness of 10 to 20 mm.

This briquette is charged into the induction melting furnace 31 having a melting amount of 1 ton by the constant quantity feeder 30 through the intermediate hopper 29. The induction melting furnace 31 holds therein molten iron 32 having a temperature of 1400 to 1600 ° C., and the inserted briquette 33 has a specific gravity of 1.2.
Since the amount is up to 2.5 g / cm ^3, which is smaller than that of the molten iron 32, it is deposited in layers on the molten iron surface.

The iron oxide in the briquette is mainly reduced by the carbon material in the briquette 33 and is recovered as iron in the molten iron. Further, zinc oxide is also reduced and evaporated by the carbon material in the briquette, and the upper lid 31 of the induction melting furnace 31.
Oxidized by oxygen in the air flowing into the furnace from the air inlet provided in a, etc., becomes fine zinc oxide particles of 10 μm or less, passes through the pipe 31b, and is pneumatically fed to the dust collector. On the other hand, a part of the briquette is pulverized by the thermal shock from molten iron, and is discharged out of the system together with zinc oxide in an unreacted state. In addition, iron oxide is partly discharged from the surface of the molten iron to the outside of the system.

These zinc oxide particles and unreacted agglomerated dust are collected by a first dust collecting device 34 that mainly captures dust of 10 μm or more and a second dust collecting device 35 that captures dust of less than 10 μm. Gathered. Table 1 shows the components of the dust collected by each dust collector. In this embodiment, the second
The dust collected by the dust collector 35 is stored in the product hopper 37 because the target zinc oxide concentration is set to 50% or more.

Further, since the dust collected by the first dust collector 34 is smaller than the target zinc concentration, it is returned to the dust hopper 21 via the recycle line 39. The recirculated dust 40 is agglomerated again by the agglomeration device 28 together with the raw material dust 22. The percentages of dust collected by the first and second dust collectors are 30 wt% and 70%, respectively.
wt%.

In this way, the required minimum amount of dust can be recycled and the dust of high concentration zinc can be efficiently recovered. The collected dust is agglomerated by the agglomeration device 38 and delivered to a smelting maker, and the smelting maker processes zinc oxide as a raw material to produce zinc.

[0041]

[Table 1]

[0042]

As described above, according to the present invention, zinc-containing dust generated from an iron mill is used as agglomerated dust, which is charged into molten iron in a melting furnace, and iron oxide in the dust is mixed in molten iron. It is reduced and recovered in molten iron, and zinc oxide in the dust is reduced and vaporized, and thus vaporized zinc is recovered as zinc oxide. At this time, the dust containing zinc oxide is mixed with the carbon material for reduction to agglomerate, and the agglomerated dust is charged into the molten iron in the melting furnace, whereby a high concentration of zinc can be produced with high efficiency. In addition, it is possible to recover with high productivity. In addition, since the facility for recovering zinc in the dust uses a relatively simple dust collector, the facility cost and the operating cost are economical.

[Brief description of drawings]

FIG. 1 is a process drawing of an embodiment of a method for recovering zinc oxide from dust according to the present invention.

FIG. 2 is a process diagram showing a conventional method for recovering zinc from 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: Intermediate hopper 30: Fixed amount feeder 31: Induction melting furnace 32: Molten iron 33 : Briquette 34: 1st dust collector 35: 2nd dust collector 36: Blower 37: Product hopper 38: Agglomeration device 39: Recycle line 40: Recycled dust

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number in the agency FI technical display location C22B 19/34 C22B 19/34 (72) Inventor Noboru Sakamoto 1-2-1, Marunouchi, Chiyoda-ku, Tokyo No. Nippon Steel Tube Co., Ltd.

Claims (5)

[Claims] 1. A zinc oxide-containing dust is agglomerated, charged into a melting furnace containing molten iron, the iron oxide in the dust is reduced in the molten iron and recovered in the molten iron, and in the dust. In the method for recovering zinc in dust in which zinc oxide is reduced to zinc and vaporized zinc is recovered as zinc oxide, a reducing carbon material is mixed with the dust to form agglomerated dust. The method for recovering zinc oxide from zinc oxide-containing dust, comprising: 2. The ratio of the carbon material for reduction to the dust is 1.5 to 10 times the stoichiometric ratio required for reduction of iron oxide and zinc oxide. A method for recovering zinc oxide from zinc oxide-containing dust as described. 3. The zinc oxide-containing dust according to claim 1, wherein, in the agglomeration process of the zinc oxide-containing dust, a hydraulic additive is mixed with the dust in addition to the carbon material. Of zinc oxide from water. 4. When mixing the hydraulic additive,
Basicity of slag (CaO / Si) generated in the melting furnace.
The method for recovering zinc oxide from zinc oxide-containing dust according to claim 3, wherein the hydraulic additive is mixed so that O) is in the range of 0.5 to 1.5. 5. The charging amount of the agglomerated dust is set to 0.2 to 1.0 t / h · m ² per cross sectional area of the melting furnace. The method for recovering zinc oxide from zinc oxide-containing dust as described in item 1.