JPH0790394A - Dezincification method of ferroscrap and its device - Google Patents

Abstract

PURPOSE:To continuously execute a stage for dissolving zinc by recirculating the gas in the upper part of the liquid level of an aq. ammonia soln. into the aq. soln. in the method for dissolving the zinc while blowing an oxygen-contg. gas into the aq. ammonia soln. CONSTITUTION:Ferroscrap contg. the zinc is dropped down to a lower bell from an inlet of a hopper by closing the lower bell 15 of a supplying means 11 and opening an upper bell 15 and is charged into the aq. ammonia soln. in a zinc dissolution vessel 12 of a hermetic construction by closing the upper bell and opening the lower bell. While the oxygen-contg. gas is blown through a route 17 into the aq. ammonia soln., the zinc is dissolved. Since the gas is commonly used for stirring as well, the gas is preferably blown measurably excessively. The excess gas is recycled for blowing through a gas circulating route 17 together with the evaporated ammonia. As a result, the dissolution of the zinc is rapidly and effectively executed and the high-grade ferroscrap is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating zinc from ferro-scrap mixed with galvanized steel and the like to obtain scrap of high purity suitable for recycling, and an apparatus therefor.

[0002]

2. Description of the Related Art In various fields such as automobiles, electric appliances, and building materials, galvanized steel materials are used for corrosion prevention, and the amount used is increasing year by year. for that reason,
The zinc content in ferro scrap (iron scrap) also tends to increase. When scrap containing galvanized steel is mixed in a scrap melting furnace, most of the zinc evaporates and is discharged into the exhaust gas, and is oxidized by oxygen in the exhaust gas and oxidized in the dust collected in the exhaust gas treatment system. Since it is mixed in as zinc, the dust processing cost increases.

Further, a part of zinc adheres to the cooling part of the exhaust gas treatment system and grows into an icicle-like solid, which causes troubles in the exhaust gas treatment equipment. Therefore, when using scrap mixed with galvanized steel as a raw material for steel melting, it is desired to remove zinc in advance.

A typical method for removing zinc from scrap is as follows.

(1) Method of heating scrap to evaporate zinc adhering to the surface of galvanized steel material
57-85936).

(2) A method of mechanically removing oxidized / altered zinc adhering to the surface of a galvanized steel material which cannot be removed by the heat treatment by subjecting the scrap to rapid heating and then shot blasting (JP-A-63) -96224 publication).

(3) A method of removing zinc on the surface of the galvanized steel material by heating the scrap and at the same time bringing it into contact with an oxidizing gas (JP-A-2-298225).

[0008]

In any of the above methods,
It utilizes the physical properties of zinc and iron, that is, the difference in melting point or vapor pressure.Since zinc and iron are alloyed in the process of treatment, zinc can be removed at a high dezincification rate and zinc can be efficiently removed. It is difficult to collect.

In order to solve the above-mentioned drawbacks of the conventional dezincification method, the present inventor removed zinc from ferro scrap by using an aqueous solution containing ammonia and an ammonium salt (hereinafter referred to as an ammoniacal aqueous solution), A recovery method (Japanese Patent Application No. 4-142808, hereinafter referred to as prior invention) was proposed. This method takes advantage of the fact that zinc reacts with ammonia and ammonium salts in an aqueous ammonia solution to form an amminezinc complex and dissolves easily, whereas iron is passivated and does not dissolve at all. , Step 1 of treating a ferro scrap containing zinc with an ammoniacal aqueous solution in the presence of oxygen to dissolve zinc in the scrap as an ammine zinc complex, and heating the aqueous solution obtained in step 1 to evaporate ammonia After that, the method comprises a step 2 of collecting the precipitated zinc salt.

In order to efficiently carry out this dezincification process, it is important that the dissolution reaction of zinc in step 1 is carried out quickly, and the solution is sufficiently stirred so that zinc, the ammoniacal aqueous solution and oxygen are brought into contact with each other. Need to be good. Therefore, conventionally, a method of mechanically stirring an aqueous solution using a stirrer or a method of accelerating the reaction by bubbling by blowing gas into the aqueous solution to promote the reaction has been conventionally performed.

However, in the above-mentioned dezincification process, since ferro scrap having a relatively large particle size is targeted for treatment, mechanical stirring is difficult. Bubbling by directly blowing an oxygen-containing gas into the solution is an effective method for accelerating the reaction, but in order to stir strongly, a large amount of the oxygen-containing gas must be blown, so that a large amount of gas is blown. Since ammonia in the aqueous ammonia solution volatilizes and is discharged out of the system together with the unreacted oxygen-containing gas, it is difficult to keep the ammonia content in the solution at a constant concentration. Further, since the amount of exhaust gas is large, there is a problem in that the ammonia recovery device is heavily burdened.

On the other hand, when the above-mentioned dezincification process is applied to the large-scale treatment of ferro scrap, it is necessary to enhance the treatment efficiency by making the zinc dissolution step continuous.

For example, when the valuable metal is leached from the ore by the wet method, the ore is generally crushed before the leaching.
The powdered ore can be put directly in the leaching tank, and the slurry after leaching can be continuously discharged through the transport pipe, and the continuous leaching process is easy. However, in the dezincification process of the above-mentioned prior invention, scrap having a large grain size is treated,
It is difficult to make the treatment continuous by the method of directly introducing the ferro scrap into the melting tank like the leaching of the ore. Further, since the aqueous solution used to dissolve the ferro scrap contains volatile ammonia, it is necessary to take measures against the evaporation of ammonia.

The present invention provides an improved method and an apparatus therefor capable of rapidly and efficiently dissolving zinc in carrying out dezincification treatment of zinc-containing scrap according to the above-mentioned prior invention. It is an object of the present invention to provide an apparatus capable of continuously performing the melting step of.

[0015]

SUMMARY OF THE INVENTION The subject matter of the present invention relates to a ferro-scrap dezincing method described below, an apparatus therefor, and a dezincing apparatus capable of continuous treatment.

A method of immersing a ferro scrap containing zinc in an ammoniacal aqueous solution, selectively dissolving zinc in the aqueous solution, and dezincing the zinc is performed by blowing an oxygen-containing gas into the ammoniacal aqueous solution. A method for dezincing ferro scrap, which comprises melting and recirculating a gas above the liquid surface of the aqueous solution into the ammoniacal aqueous solution and blowing the gas.

A device for immersing a ferro scrap containing zinc in an aqueous ammonia solution, selectively dissolving zinc in the aqueous solution, and dezincing zinc, the reaction container containing the aqueous ammonia solution, and the inside of the reaction container. A gas blower for blowing an oxygen-containing gas into the ammoniacal aqueous solution of
A ferro-scrap dezincing device having a gas circulation path for supplying the gas above the liquid surface of the aqueous solution to the gas blower again.

A ferro scrap that is equipped with a mechanism for preventing gas from escaping from the zinc dissolution tank and that supplies ferro scrap containing zinc to the zinc dissolution tank, and a ferro scrap that contains an ammoniacal aqueous solution and is supplied from the scrap supply means. A zinc dissolving tank for receiving the, and a scrap cleaning tank provided adjacent to the zinc dissolving tank and provided with a sprinkling means,
A scrap transfer means for transferring ferro scrap from the zinc dissolution tank to the scrap cleaning tank, a gas blower for blowing an oxygen-containing gas into the ammoniacal aqueous solution in the zinc dissolution tank, and the gas above the liquid surface of this aqueous solution is re-gassed. A ferro-scrap dezincing device having a gas circulation path for supplying to a blower.

[0019]

The present invention (the above-mentioned inventions) will be described in detail below.

Examples of the ferro-scrap containing zinc to be treated in the inventions 1 to 3 are waste materials (scraps) such as automobile bodies, electric products, and building materials using galvanized steel materials, or the waste materials are mixed. It's scrap. It is desirable that these zinc-containing scraps be, if necessary, cut into a size suitable for processing before being processed by the method or apparatus of the present invention.

The invention of (1) is made in the above-mentioned prior invention for the purpose of rapidly and efficiently dissolving zinc.

FIG. 1 shows an example of the dezincification process (example using ammonium carbonate as an ammonium salt) in the invention of this prior application.

As described above, zinc forms an ammine zinc complex and easily dissolves in an ammoniacal aqueous solution containing ammonia and an ammonium salt. That is, when zinc-containing scrap is treated with an ammoniacal aqueous solution in the presence of oxygen, zinc can be selectively dissolved according to the following formula (1), and dezinced high-quality ferro-scrap can be obtained.

Zn + 2NH ₃ + 2NH ₄ ⁺⁺ 1/2 O ₂ ═Zn (NH ₃ ) ₄ ²⁺ + H ₂ O (1) In the dezincification process shown in FIG. By absorbing gas, an ammoniacal aqueous solution containing ammonia and ammonium carbonate is prepared,
This aqueous solution is supplied to the zinc dissolution step. In the melting step, the impure scrap containing zinc is put into the melting tank containing the ammoniacal aqueous solution, the oxygen-containing gas is supplied, and the zinc is dissolved by the reaction of the above formula (1) to be dezincified. Remove the high-grade scrap from the melting tank. The zinc-dissolved leachate is sent to the crystallization step after filtration and heated to decompose the complex as shown in the following formula (2), evaporate ammonia and carbon dioxide gas, and crystallize basic zinc carbonate. . The crystallized zinc is collected through filtration and drying.

5Zn (NH ₃ ) ₄ CO ₃ + 3H ₂ O = 2ZnCO ₃ · 3Zn (OH) ₂ ↓ + 3CO ₂ ↑ + 20NH ₃ ↑ ・ (2) Evaporated ammonia and carbon dioxide gas are the steps of preparing an ammoniacal solution. Return to and reuse. Therefore, the ammoniacal aqueous solution for dissolution can be circulated and used only by replenishing the amount of carbon dioxide gas required for the production of basic zinc carbonate, and the chemical solution cost and the waste solution treatment cost can be greatly reduced.

In the invention of the prior application, the zinc is dissolved while blowing the oxygen-containing gas into the ammoniacal aqueous solution, and the gas above the liquid surface of the aqueous solution is circulated again into the ammoniacal aqueous solution and blown. Is a method for dezincing ferro scrap. As a result, it is possible to prevent the loss due to volatilization of ammonia (volatilization loss), and at the same time, since the aqueous solution is stirred by gas bubbling, good contact between oxygen and scrap and the aqueous solution is maintained, and The dissolution of zinc is promoted.

The ammoniacal aqueous solution used in the present invention is an aqueous solution in which ammonia and an ammonium salt are dissolved. As the ammonium salt, ammonium carbonate, which can be prepared by blowing ammonia and carbon dioxide gas into water, is most suitable for the industrial practice of the present invention, but other ammonium salts such as ammonium sulfate and ammonium chloride can also be used. Is. The ammonia concentration of the aqueous ammonia solution is preferably 0.1 to 10 M, the ammonium ion concentration is 0.1 to 10 M, and the pH is preferably 8 to 12.

To dissolve zinc in this ammoniacal aqueous solution, an oxidizing gas containing oxygen is required as an oxidizing agent. In order to accelerate this dissolution reaction, in the present invention, the dezincification treatment of the ferro scrap is performed while blowing the oxygen-containing gas into the ammoniacal aqueous solution.

As the oxygen-containing gas, either pure oxygen or a mixed gas of oxygen and an inert gas (for example, air) can be used.

The invention of (1) is an apparatus for carrying out the above-mentioned invention, that is, a dezincification apparatus of ferro scrap.

First, a dezincification apparatus suitable for using pure oxygen as the oxidizing gas will be described.

FIG. 2 is a diagram showing the construction of an example of such an apparatus, which is a reaction container 1 for containing an aqueous ammoniacal solution 4,
Gas blower 2 for blowing an oxygen-containing gas into this aqueous solution 4
And a gas circulation path 3. The gas blower 2 is
It is arranged in the lower part of the reaction vessel 1 so that the aqueous solution 4 can be sufficiently stirred by bubbling oxygen gas. As shown, it is preferably arranged on the bottom surface of the reaction vessel 1.

The gas circulation path 3 is a piping system for feeding the gas in the upper space of the reaction vessel 1 to the gas blower 2, and is provided with a pump 7 for circulating the gas in the middle. The gas in the circulation path 3 is pressurized so as to be able to bubble from the gas blower 2 against the water pressure of the ammoniacal aqueous solution 4.

Ferro-scrap 5 is immersed in the ammoniacal aqueous solution 4 contained in the reaction vessel 1. It is preferable that the ferro scrap is immersed in a net cage 6 (or a cage made of a perforated metal plate) through which the aqueous solution 4 can be easily distributed so that it can be easily taken out after the dezincification treatment.

Oxygen consumed by the reaction is supplied from the oxidizing gas introducing pipe 8. When pure oxygen is used as the oxidizing gas, no exhaust gas is generated, and the upper space of the reaction vessel 1 is filled with unreacted oxygen and ammonia volatilized by bubbling. All of these gases are sent to the gas blower 2 again via the gas circulation path 3. If the gas circulation path 3 is not provided, it is impossible to stir by gas bubbling without discharging the gas, but unreacted oxygen and ammonia volatilized due to bubbling are circulated again to the aqueous solution 4. By blowing in, all unreacted oxygen can be used without discharging gas, and stirring by gas bubbling can be performed without letting volatile ammonia escape to the outside of the system. Therefore, it is not necessary to provide a gas outlet in the reaction system. Ammonia blown into the aqueous solution is absorbed by it and participates in the dissolution reaction of zinc.

When the oxidizing gas to be supplied is pure oxygen, the oxygen concentration in the reaction vessel is determined by the initial oxygen concentration. Therefore, if necessary, the inert gas (air) in the reaction vessel is replaced with oxygen in advance. By doing so, the oxygen concentration of the reaction system can be adjusted.

The reaction system which does not generate such exhaust gas is
In particular, it is suitable for carrying out the dissolution reaction of zinc under conditions where the reaction temperature is high, or under conditions where the ammonia concentration of the aqueous ammonia solution is high and the vapor pressure of ammonia is high.

FIG. 3 is a diagram showing the structure of an example of a dezincing apparatus suitable for the case where a mixed gas of oxygen and an inert gas (for example, air) is used as the oxidizing gas. As in the case of the apparatus shown in FIG. 2, a reaction vessel 1 containing an ammoniacal aqueous solution 4, a gas blower 2 for blowing an oxygen-containing gas into the aqueous solution 4, and a gas circulation path 3 are provided.

The difference between this device and the device shown in FIG.
That is, the reaction vessel 1 is provided with the gas exhaust pipe 9. When a mixed gas of oxygen and an inert gas is used, if the entire amount of the gas above the liquid surface is blown into the ammoniacal aqueous solution through the gas circulation path 3, excess inert gas accumulates in the reaction system. The oxygen concentration of the system will gradually decrease, which will hinder the processing. Therefore, an amount of the inert gas equivalent to the amount introduced into the reaction vessel along with the oxygen content consumed in the zinc dissolution reaction is discharged from the gas discharge pipe 9 so that the concentration of the inert gas in the reaction system is substantially constant. It is preferable to hold at. The supply of the consumed oxygen content is performed by introducing a mixed gas (air in the illustrated example) from a path 10 connected to the gas circulation path 3.

The use of this apparatus has the advantage that air can be used as the oxidizing gas supplied to the reaction system.
However, since the gas discharged from the gas discharge pipe 9 also contains ammonia volatilized by gas bubbling, in order to recover the ammonia in the exhaust gas, the gas discharge pipe 9
It is necessary to attach an ammonia recovery device (not shown).

Gas bubbling can be performed by blowing air into the ammoniacal aqueous solution without circulating the gas, but in order to enhance the stirring, a much larger amount of air than the amount of oxygen consumed in the reaction is used. Since it is necessary to blow in ammonia, it is difficult to maintain the ammonia in the aqueous solution at a constant concentration, and the burden on the ammonia recovery device also increases. However, if the apparatus of the present invention shown in FIG. 3 or FIG. 2 is used, the oxygen-containing gas and the ammonia volatilized by bubbling are circulated in the apparatus, and the circulating gas stirs the aqueous solution. The concentration can be stabilized, and a large stirring force can be obtained without increasing the exhaust gas amount and the accompanying ammonia volatilization amount,
It becomes possible to rapidly carry out the dissolution reaction of zinc. In addition, the burden on the ammonia recovery device can be significantly reduced.

The dezincification treatment of ferro scrap with the above-mentioned ammoniacal aqueous solution is preferably carried out at a temperature of room temperature to 70 ° C. The treatment time varies depending on the temperature of the ammoniacal aqueous solution, the ammonia concentration, the amount of galvanized steel mixed in the ferro scrap, the thickness of the plating layer, etc.
Generally, 30 minutes or less is sufficient.

After the processing is completed, the net basket 6 is pulled up to take out the zinc-free scrap. The dezinced scrap can be washed and dried and recycled as high quality ferro scrap into steel melt. In addition, the aqueous solution containing the ammine zinc complex separated from the scrap crystallizes if the residual ammonia and ammonia salt concentrations in the aqueous solution are high enough to dissolve zinc according to formula (1). Before being sent to the precipitation step, it may be subjected to a dissolution treatment of zinc once or twice or more.

The invention of (1) is a dezincing apparatus for ferro scrap which can continuously carry out the zinc dissolving step in carrying out the above invention.

FIG. 4 is a diagram showing the construction of an example of such an apparatus. A scrap supply means 11, a zinc dissolution tank 12 for accommodating an ammoniacal aqueous solution and for receiving scrap fed from the scrap supply means 11, and a zinc Adjacent to the dissolution tank 12, a scrap cleaning tank 13 equipped with a sprinkling means 18, scrap transfer means 14 for transferring scrap from the zinc dissolution tank 12 to the scrap cleaning tank 13, and oxygen content in the aqueous solution in the zinc dissolution tank 12 It has a gas blower 16 for blowing gas and a gas circulation path 17 for supplying the gas above the liquid surface of the aqueous solution to the gas blower 16.

In this example, the scrap supply means 11 comprises a hopper having a mechanism capable of preventing gas from escaping from the zinc melting tank 12. The interior of the hopper is partitioned by two upper and lower partition walls to which bells 15 having an inverted funnel shape are attached, and the bell 15 is configured to open and close when the bells 15 move up and down. When sending scrap, first close the lower bell and open the upper bell to drop the scrap from the inlet of the hopper to the lower bell, then
The upper bell is closed and the lower bell is opened, and the scrap is put into the zinc melting tank 12. By using such means, it is possible to prevent the ammonia volatilized in the dissolution tank 12 from escaping to the outside at the time of sending the scrap, eliminating the volatilization loss of ammonia, and maintaining a good working environment. it can.

The zinc dissolving tank 12 has a closed structure, a solution transport pipe 19 for supplying an ammoniacal aqueous solution to the dissolving tank 12 in the upper part, and a gas blower for gas above the liquid surface of the aqueous solution. A path 26 connected to a gas circulation path 17 for supplying the gas to the tank 16 is provided, and a gas blower 16 is provided below the zinc dissolution tank 12, and an ammoniacal aqueous solution in which zinc is dissolved (this is referred to as a leachate) is recovered in zinc. Solution discharge pipe 20 for sending to the process
Is attached. Gas blower 16 is a gas circulation path
Oxygen-containing gas (pure oxygen, air, etc.) is blown into the ammoniacal aqueous solution through this gas circulation path 17, and oxygen involved in the zinc dissolution reaction is supplied to the reaction system as an oxidizing agent for zinc. It This oxygen-containing gas is
Since it also serves to stir the liquid by bubbling, it is desirable to blow it in a considerably excessive amount. Excess gas is circulated and used for blowing through the gas circulation path 17 together with the volatilized ammonia. The oxygen consumed in the zinc dissolution reaction is supplied by introducing an oxygen-containing gas from the middle of the gas circulation path 17.

It is desirable that the scrap transfer means 14 be one that allows liquid and gas to easily pass therethrough because the dissolution reaction of zinc is a reaction between solid and liquid.
A chain type conveyor or the like is suitable. Furthermore, if necessary, a plurality of net-like scrap cages or cages made of perforated metal may be attached on the conveyor or suspended under the conveyor to prevent the scrap from falling into the melting tank 12 for transfer. Means may be taken to facilitate it.

The scrap transfer means 14 is installed so as to allow the scrap to pass through the aqueous solution in the zinc dissolution tank 12, transfer it to the scrap cleaning tank 13 without being exposed to the outside of the apparatus, and pass through it. This is because the ammonia solution is attached to the scrap after the zinc dissolution treatment, so if it is exposed to the outside of the equipment before cleaning, not only will ammonia attached to the scrap volatilize and become a loss, but also the work environment. It is also a cause of deterioration. In order to avoid this, as shown in FIG. 4, it is advantageous to integrally configure the zinc dissolution tank 12 and the scrap cleaning tank 13. A sprinkler 18 is provided above the scrap cleaning tank 13.

In order to perform dezincification treatment of ferro scrap using this apparatus, an ammoniacal aqueous solution is used in the zinc dissolution tank 12
It is placed inside and ferro scrap is charged into it through the scrap supply means 11. The ferro scrap is placed on the scrap transfer means 14 (in this case, a conveyor) and passes through the ammoniacal aqueous solution, during which the oxygen-containing gas is blown through the gas circulation path 17 and the gas blower 16, and the liquid is bubbled. Therefore, the dissolution reaction of zinc proceeds rapidly.

The ferro scrap dezinced in the zinc dissolution tank 12 is sprinkled from the cleaning water pipe 21 in the scrap cleaning tank 13 by spraying means.
Ammonia and ammine zinc complex, which is washed by the washing water supplied via 18 and adheres to the scrap,
After the ammonium salt is removed, it is discharged outside the device.
As a result of this sprinkling and cleaning, the zinc dissolution tank 12 volatilizes and the cleaning tank 13 evaporates.
Ammonia gas flowing into the is also absorbed by the wash water at the same time,
To be removed. Therefore, in general, it is not necessary to install an ammonia treatment device at the scrap outlet of the scrap cleaning tank 13, but it is also possible to attach a treatment device if necessary, especially when exhaust gas regulations are strict.

Since the cleaning wastewater discharged from the cleaning wastewater discharge pipe 22 contains a low concentration of ammonia, it is desirable to use it for preparing an ammoniacal aqueous solution. If the ammonia concentration in the cleaning wastewater is low and can be reused for cleaning scraps, a part of the wastewater may be reused for cleaning scraps.

FIG. 5 is a diagram showing the configuration of another example of the apparatus for carrying out the invention of FIG. The difference from the device shown in FIG. 4 is that the scrap supply means comprises a conveyor 23 and the scrap inlet is of an open type.

The ferro scrap is placed on the conveyor 23 and continuously supplied to the zinc dissolution tank 12, drops in the dissolution tank 12 and is transferred to the scrap transfer means 14 (conveyor), and is also transferred to the ammoniacal aqueous solution. Be immersed. A buffer plate 24 is attached between the conveyor 23 and the scrap transfer means 14 (conveyor) so that scrap does not dissipate. Since the scrap inlet is an open type, a draft 25 is provided adjacent to the inlet of the melting tank 12, and the conveyor 23
By passing it through this draft 25
It is possible to prevent 12 ammonia from escaping out of the device. The gas exhausted from the draft 25 is preferably sent to an ammonia recovery device (not shown) to recover ammonia.

The oxygen-containing gas is blown into the ammoniacal aqueous solution from the gas blower 16 via the path 26 connected to the gas circulation path 17.

The apparatus shown in FIG. 5 requires the draft 25 and the ammonia recovery apparatus, but like the apparatus shown in FIG. 4, two bells attached to the partition of the hopper are opened and closed sequentially. Since no operation is required, it is easy to load scrap into the feeding and melting tank 12.

In the apparatus shown in FIGS. 4 and 5, the relationship between the length of the zinc melting tank 12 and the moving speed of the belt of the scrap transfer means 14 (conveyor) may be appropriately determined depending on the processing time.

Although the scrap transfer means 14 is basically operated continuously, it is also possible to adopt an operation method in which the operation and the primary stop are repeated depending on the necessity of adjusting the processing time. As an example of the dezincification apparatus of the invention,
It is not limited to the devices of FIGS. 4 and 5 above.

The dezincification apparatus of the present invention has a high processing efficiency because it can continuously perform dezincification processing of ferro scrap.

[0060]

Example 1 Ferro scrap with a zinc content of 0.75 wt% (shredder scrap) cut by a shredder was dezincified using pure oxygen as an oxidizing gas by using the apparatus of the present invention having the configuration shown in FIG. Processed.

First, an aqueous solution having an NH ₃ concentration of 1.0 M and an (NH ₄ ) ₂ CO ₃ concentration of 0.5 M was poured into a stainless steel reaction vessel having an internal volume of 1.5 m ^{3, and} the shredder scrap having a weight of 0.5 ton was put therein. . Gas bubbling was performed by circulating pure oxygen at a temperature of about 30 ° C. at a flow rate of 1 m ³ / min for 20 minutes. Then, the scrap was taken out and the zinc content was measured. As a result, the zinc content was 0.08% by weight, and the dezincification rate was 89%.

On the other hand, a reaction vessel having no gas circulation path and provided with a gas introduction pipe in the upper portion is used, the above-mentioned shredder scrap is put therein, pure oxygen is filled in the upper space of the vessel, and the consumed oxygen is gasified. When the scrap was processed while being supplied to the reaction vessel from the introduction pipe, the zinc content of the scrap was 0.7% by weight, and the dezincification rate was only 6.7%.

As is clear from the above results, the dezincification efficiency of ferro scrap was remarkably improved by the method of the present invention in which pure oxygen was circulated in the reaction vessel while bubbling into the treatment liquid to stir the liquid.

[0064]

Example 2 The same shredder scrap as that processed in Example 1 was dezincified using air as an oxidizing gas using the apparatus of the present invention having the configuration shown in FIG.

First, an aqueous solution having an NH ₃ concentration of 1.0 M and a (NH ₄ ) ₂ CO ₃ concentration of 0.5 M was poured into a stainless steel reaction vessel having an internal volume of 1.5 m ³ , and the above shredder scrap having a weight of 0.5 ton was put therein. . The dezincification treatment was carried out at a temperature of about 30 ° C. for 20 minutes while performing gas bubbling with a supply rate of fresh air from the air introduction pipe being 40 liter / min and an air circulation flow rate of 1 m ³ / min. After that, the scrap was taken out and the zinc content was measured. As a result, the zinc content was 0.11% by weight, and the dezincification rate was
It was 85%.

On the other hand, a reaction vessel having no gas circulation path and provided with a gas introduction pipe in the upper part is used, the shredder scrap is put therein, and 40 liters of air is put in the upper space of the container.
When the gas was introduced at a flow rate of / min through the gas introduction pipe and the exhaust gas was discharged from the reaction vessel and treated, the zinc content of the obtained scrap was 0.53% by weight, and the dezincification rate was only 29%.

Also in this case, it is apparent that the method of the present invention remarkably improves the dezincification efficiency of ferro scrap.

[0068]

Example 3 Galvanized steel scrap (ferro scrap) having a zinc content of 0.6% by weight was dezincified with an ammoniacal aqueous solution containing ammonia and ammonium carbonate using the apparatus of the present invention shown in FIG.

The length of the dissolution tank 12 of the dezincification apparatus used is 10
m, the length of the cleaning tank 13 is 5 m, the widths of the melting tank 12 and the cleaning tank 13 are both 1 m, and the scrap supply rate is 4 t / hr.
The belt moving speed of the conveyor was set to 20 m / hr. The processing time was 1.5 hours.

An ammoniacal aqueous solution having an NH ₃ concentration of 4.0 M and a (NH ₄ ) ₂ CO ₃ concentration of 2.0 M was placed in the dissolution tank 12 through a solution transport pipe 19 to 200
Dissolving tank with zinc dissolved at a flow rate of l / hr 12
The aqueous solution (leaching solution) in the inside was discharged from the solution discharge pipe 20 at the same flow rate of 200 l / hr, and the amount of the solution in the tank was maintained at a constant amount of about 10 m ³ . Pure oxygen was blown into this solution at a flow rate of 20 m ³ / hr, and the gas above the liquid surface of the aqueous solution was circulated while supplying a small amount of oxygen.

The concentration of the ammoniacal aqueous solution in the tank was almost constant, NH ₃ 1.0M, (NH ₄ ) ₂ CO ₃ 0.5M, Zn (NH ₄ ) ₄ CO ₃ 1.5M, and the liquid temperature was 40 ° C. there were. In the cleaning tank 13, water at room temperature
Water was sprinkled on the scrap at a flow rate of 0.5 m ³ / hr.

The leachate taken out from the solution discharge pipe 20 is
It is continuously sent to a perforated plate distillation column and heated to 90 to 100 ° C in the distillation column to decompose the ammine zinc complex, recover the evaporated ammonia and carbon dioxide gas, and at the same time, contain the crystallized basic zinc carbonate slurry. Was separated, washed with water and dried. As a result, basic zinc carbonate could be recovered at an average rate of 29 kg / hr.

The above continuous dezincification treatment was continued for 48 hours.
The zinc content of the obtained scrap after dezincification treatment is 0.07
The dezincification rate was 88% by weight.

[0074]

When the method of the present invention is applied to the dezincification treatment of ferro scrap containing zinc, it is possible to obtain a strong stirring force, the dissolution of zinc is carried out quickly and efficiently, and high quality ferro scrap is obtained. Can be obtained. At the same time, the loss due to the volatilization of ammonia can be eliminated or significantly reduced. This method can be easily realized by using the apparatus of the present invention, and it is also possible to further improve the dissolution efficiency by continuing the zinc dissolution step.

[Brief description of drawings]

FIG. 1 is a process diagram showing an example of a dezincification process of ferro scrap with an ammoniacal aqueous solution.

FIG. 2 is an explanatory diagram showing the configuration of an example of the dezincification apparatus of the present invention when pure oxygen is used.

FIG. 3 is an explanatory diagram showing the configuration of an example of the dezincification device of the present invention when air is used.

FIG. 4 is an explanatory diagram showing a configuration of an example of a dezincification apparatus of the present invention that continuously performs a zinc dissolving step.

FIG. 5 is an explanatory diagram showing the configuration of another example of the dezincification apparatus of the present invention that continuously performs the zinc dissolution step.

[Explanation of symbols]

1: reaction vessel, 2: gas blower, 3:
Gas circulation route, 4: Ammoniacal aqueous solution, 5: Ferroscrap, 6: Net basket, 7: Pump, 8:
Oxidizing gas introduction pipe, 9: gas discharge pipe, 10: route,
11: scrap supply means, 12: zinc melting tank
13: scrap cleaning tank, 14: scrap transfer means, 15: bell, 16: gas blower,
17: Gas circulation route, 18: Water sprinkling means, 19: Solution transport pipe, 20: Solution discharge pipe, 21: Wash water pipe,
22: Wash drainage pipe, 23: Conveyor, 24: Buffer plate, 25: Draft, 26: Route

Claims (3)

[Claims] 1. A method of immersing a ferro scrap containing zinc in an ammoniacal aqueous solution, and selectively dissolving zinc in this aqueous solution to dezincify, wherein an oxygen-containing gas is blown into the ammoniacal aqueous solution. A method for dezincing ferro scrap, characterized in that zinc is dissolved and a gas above the liquid surface of the aqueous solution is recirculated and blown into the ammoniacal aqueous solution. 2. A device for immersing a ferro scrap containing zinc in an ammoniacal aqueous solution, selectively dissolving zinc in the aqueous solution to dezincify, and a reaction container containing the ammoniacal aqueous solution and a reaction. A gas blower for blowing an oxygen-containing gas into an ammoniacal aqueous solution in a container, and a gas circulation path for supplying the gas above the liquid surface of the aqueous solution to the gas blower again, Dezincification equipment. 3. A mechanism for preventing gas from escaping from a zinc dissolution tank, a scrap supply means for supplying ferro scrap containing zinc to the zinc dissolution tank, and an ammoniacal aqueous solution contained therein, and supplied from the scrap supply means. A zinc dissolution tank that accepts ferro scrap, a scrap cleaning tank that is provided adjacent to the zinc dissolution tank and that is equipped with sprinkling means, a scrap transfer means that transfers ferro scrap from the zinc dissolution tank to the scrap cleaning tank, and a zinc dissolution tank A gas blower for blowing an oxygen-containing gas into the ammoniacal aqueous solution in the inside,
A ferro-scrap dezincing device having a gas circulation path for supplying the gas above the liquid surface of the aqueous solution to the gas blower again.