KR20080077802A - Recovery method of zinc component from electric dust and apparatus for same - Google Patents

Abstract

The present invention injects dust and concentrated sulfuric acid into a rotary reactor such as a kiln, which includes a ball mill, and reacts the dust and sulfuric acid to recover zinc components as zinc sulfate. The furnace and concentrated sulfuric acid are continuously injected, and the reaction mixture passing through the rotary reactor is received by the second hopper 40 and stored in the storage tank 60 through the second screw conveyor, and the storage tank is about 30 to 50 ° C. After storage for one or more days, the mixture was transferred to a second reactor, and then about three times the amount of water was added to the amount of the maximum dust, the mixture was kept at about 70 to 90 ° C, and stirred until the pH was 4 to 4.5. Disclosed is a method for recovering zinc sulfate, which is characterized by filtration separation.

In addition, in the method of the present invention, after reacting by a dry method in a rotary reactor in which no water or the like is added, the obtained reactant can be stored, and only zinc sulfate can be recovered from the reactant, if necessary, so that a large amount of dust is continuously treated. High yield, high purity zinc sulfate can be recovered, providing a very economical method.

Description

Recovery method of zinc component from electric dust and apparatus for same {PROCESS FOR RECOVERING ZINC COMPONENT FROM ELECTRIC ARC FURNACE DUST AND APPARATUS THEREFOR}

1 is a schematic diagram of a rotary reactor for carrying out the present invention.

The present invention relates to a method of recovering zinc as zinc sulfate by reacting dust and sulfuric acid by injecting dust and concentrated sulfuric acid into a rotary reactor, such as a kiln, which has a ball mill. More specifically, dust and concentrated sulfuric acid are continuously injected into the electric power while driving a rotary reactor containing a ball mill, the reaction mixture passing through the rotary reactor is stored in a storage tank, and stored in the storage tank for at least one day, and then reacted. The present invention relates to a method for recovering zinc sulfate and a device, which is transferred to a second reactor, stirred with water until pH reaches 4 to 4.5, and then filtered.

Zinc sulfate, which is the final product obtained in the present invention, is itself widely used as a trace inorganic nutrient source of pigments, fertilizers, feeds, and the like. When used as a fertilizer, the zinc sulfate tolerance of zinc sulfate is 0.2% or less, so zinc sulfate within this range can be easily provided. The zinc sulfate thus obtained can be reduced to zinc metal or other zinc compounds as necessary.

Conventionally, zinc sulfate has been produced by directly reacting with sulfuric acid or hydrochloric acid using zinc metal. However, since zinc metal is expensive, it is not economically advantageous to manufacture such compounds, and a method of producing them using metal zinc is not widely used. Thus, the waste is used to recover the zinc contained in the waste, thereby protecting the environment and economically advantageous. Among these wastes, it is currently advantageous to use a large amount of generated electric dust (EAF), but manufacturing with such wastes is subject to a number of constraints.

Conventionally, since electric dust cannot be used as it is, it has been disposed of through special industrial waste companies or mixed with asphalt mortar, but the soil is desolated due to various heavy metals generated in leachate, and also the solution containing heavy metals thus leached. When dried, fine powder is scattered and adversely affects the human body, and thus has emerged as a social problem.

Furnace dust is generated from scrap metals such as scrap cars due to evaporation of zinc in high temperature furnace at 1800 ℃ or in scrap cars, and its components vary depending on the type of scrap metal and the processing company. ˜35%, zinc component is about 20-35%, and other aluminum, silica, various inorganic salts, copper, magnesium salt and the like are present.

The present inventors have applied for a number of patents regarding a method for recovering zinc from dust or zinc in order to solve the above problems (see Patent Application Nos. 98-12296, 98-15857, etc.). However, in the present invention, the dust may be treated with electricity to produce an expensive metal zinc or zinc compound. However, when the zinc compound is prepared, since the iron component is contained in the electric furnace dust in an amount similar to that of zinc, When sulfuric acid or hydrochloric acid is used to react with the dust by electricity, not only zinc in the dust but also iron components are reacted together. Also, when the dust is analyzed and reacted with sulfuric acid or hydrochloric acid at an equivalent ratio of zinc content in the dust, the zinc component Zinc sulfate or zinc chloride is obtained by reaction with acid, but zinc and iron components in dust are not present independently, and are present in the form of zinc ferrite (Fe ₂ O _{3 ·} ZnO) or as an alloy oxide of iron and zinc. Due to the large amount of reaction, the reaction time is too long even in the reaction with a strong acid. Since it contains 4 to 5%, it is not possible to obtain pure zinc compound unless it is de-ironed using zinc metal or zinc oxide, and in order to de-galvanize, it is expensive to de-iron, so the final compound is zinc sulfate or zinc chloride. The method for producing zinc compound is not competitive. Particularly, in the present patent application No. 1998-39927, a reducing agent is mixed with an electric dust, and sulfuric acid is added thereto to obtain zinc sulfate and ferrous sulfate. It has been disclosed a method for producing zinc sulfate by removing ferrous iron. This method is expensive because of the high facility cost and the cost of ferrous sulfate filtration, separation process, and degassing.

In order to solve this problem, the present inventors suppress the conversion of iron components to iron sulfate or iron chloride in recovering zinc sulfate by reacting dust with strong acid such as hydrochloric acid or sulfuric acid, and selectively recovering only zinc salt. To this end, a small amount of copper sulfate or copper chloride is added to react to inhibit the formation of iron sulfate or iron chloride by the catalytic action of copper sulfate or copper chloride, and a method of recovering only zinc sulfate or zinc chloride has been applied for a patent (see Patent Publication 2001-98080). number).

However, the conventional method described above takes a long time to recover zinc contained in the dust because zinc ferrite does not react well with acid, or about 50% or more of zinc is not reacted and is discharged as it is. Since all are wet reactions can not be carried out in a batch reaction in a continuous reaction, the labor costs resulting from this is not economically satisfactory method can not be used industrially.

Thus, the present inventors have made a thorough study on a method and a device capable of rapidly reacting with dust in an electric furnace and recovering a large amount of zinc components in a continuous reaction. As a result, in order to react the dust with electricity, conc. acid), so that zinc ferrite or alloy oxides of iron and zinc can be easily dissolved. In addition, zinc in the reaction reacts with sulfuric acid to be converted to zinc sulfate, and iron is converted to iron sulfate. Since the iron sulfate reacts with the unreacted zinc component and is converted into zinc sulfate and insoluble iron oxide, it is found that zinc sulfate and insoluble matter can be easily separated by eluting and filtering zinc sulfate with water. The invention was completed.

When the dust is treated with sulfuric acid by electricity, the composition ratio of iron sulfate and zinc sulfate is generally generated in the case of dust components, that is, iron 30% and zinc 30%. In order to avoid this, only zinc having a high activity can be recovered by using an equivalent amount of sulfuric acid as an equivalent ratio to zinc content, but in reality, a large amount of iron is reacted together with zinc, and when sulfuric acid is added, iron sulfate, Since zinc sulfate is recovered at about the same level, and the solution specific gravity of iron sulfate and zinc sulfate is similar, when zinc sulfate is used as a target product, iron components are completely removed and filtered to induce high purity zinc sulfate. Because of the high cost of decarburization in the process, zinc sulfate is not competitive due to its cost share. In this way, when sulfur and zinc components in the dust react with sulfuric acid, concentrated sulfuric acid (98%) is added in a ratio of 1.4 to 1.8% by weight based on the amount of zinc in the dust to avoid simultaneous dissolution of the iron and zinc components. When added, zinc is converted to zinc sulfate, some iron is converted to iron sulfate, and the iron sulfate is converted to zinc sulfate and iron oxide (Fe ₂ O ₃ ) by reaction with undiluted zinc or zinc compounds. The addition amount of concentrated sulfuric acid is about 1.4-1.8 by weight, which is more than the equivalent ratio of sulfuric acid to zinc oxide, but as described above, the excess concentrated sulfuric acid after reacting with the zinc component is a small amount of unreacted zinc, aluminum, and lead. After reacting with copper, manganese, and the like, and the iron sulfate produced by reacting with the iron component again with unreacted zinc and the like, the iron sulfate is almost all converted to insoluble iron oxide.

In addition, zinc ferrite in dust is reacted in a concentrated sulfuric acid atmosphere to be separated into iron sulfate and zinc sulfate. Iron sulfate is converted into zinc sulfate and insoluble iron oxide [Fe ₂ O ₃ ] again by the mechanism described above.

This will be described with reference to the accompanying drawings.

1 is a schematic diagram of a rotary reactor for carrying out the present invention. In Fig. 1, reference numeral 10 denotes a first hopper, reference numeral 20 denotes a first screw conveyor, reference numeral 30 denotes a rotary reactor, reference numeral 31 denotes a concentrated sulfuric acid inlet tube, reference numeral 32 denotes an outlet for discharging a mixture of concentrated sulfuric acid and dust, 33 is a chain for rotating a rotary reactor, 34 and 34 'are rotary stirrer support wheels, 35 is a ball mill steel ball, 40 is a second hopper, 41 is an exhaust pipe, and 42 is a gas collection. A scrubber, 50 is a second screw conveyor, and 60 is a storage tank.

Electric dust is continuously introduced into the rotary reactor (kiln) 30 through the first screw conveyor 20 from the first hopper 10. Further, concentrated sulfuric acid is continuously added to the rotary stirrer at a ratio of about 1: 1.4 to 1.8 with respect to the zinc content of the electric furnace dust through the injection tube 31. At this time, the dust is continuously mixed with concentrated sulfuric acid while being ground to about 150 mesh by a ball mill. At this time, the heat of reaction rises to about 150 ° C. In addition, hydrogen chloride and other harmful gases generated by the reaction heat are absorbed and treated by the scrubber 42, and the mixed raw materials are passed to the second hopper 40 through the outlet 32, and the second conveyor screw 50 is provided. Through the storage tank 60 is collected. In this storage tank, the mixture is kept at 30 to 50 ° C. and stored (reacted) for at least one day, so that unreacted dust particles are sufficiently brought into contact with sulfuric acid to react. In this storage tank, the electric dust powder reacts sufficiently with concentrated sulfuric acid so that zinc and zinc compounds are converted to zinc sulfate, some of iron is converted to iron sulfate, and iron sulfate is again reacted with zinc compounds such as zinc or zinc oxide. To zinc sulfate and iron oxide (ie, the reaction up to this point proceeds to a dry reaction without addition of water or a solution containing water). The reaction mixture was transferred to a second reactor (not shown), and about 3 times the volume of water was added to 1 volume of the reactant, and the temperature was maintained at about 70 to 90 DEG C while stirring to bring the pH to about 4 to 4.5. Recovery reaction is terminated. The reaction mixture thus obtained is filtered through a filtration device such as a filter press to separate the zinc sulfate aqueous solution and the insoluble matter. By this reaction, 98% or more of zinc contained in the dust is eluted with zinc sulfate, and iron is eluted with 1% or less. That is, the ratio of zinc sulfate: iron sulfate is about 20: 0.4. This low iron content is due to the fact that the zinc component reacts selectively in the concentrated sulfuric acid condition than the zinc component, so the zinc component reacts selectively, and the iron sulfate produced by reacting with the iron is again the zinc or zinc component. It seems to be because it continues to react with. In addition, since only a little excess of sulfuric acid is added to the amount of zinc present in the dust, only zinc is combined first, and the excess sulfuric acid is not enough to react with the total amount of iron in the dust. It is believed that less iron is eluted.

On the other hand, about 0.5 to 2% of salts such as potassium chloride and sodium chloride in the electric dust are present. However, when concentrated sulfuric acid is added to the reactor, they react with sulfuric acid to form potassium sulfate and sodium sulfate, and hydrogen chloride or water vapor is exhausted into the gas phase. Are discharged through, and these are adsorbed and treated in a conventional manner, ie, the scrubber 42.

As described above, in the present method, the dust powder and the concentrated sulfuric acid are mixed and reacted in the ball mill type rotary reactor 30, and the mixture discharged by continuously feeding the mixture is passed through the second hopper 40, and then, the second screw conveyor. After the reaction is performed (maturated) in the storage tank through the storage tank, the second reactor is added, water is added to elute zinc sulfate, and then filtered through a filtration device such as a filter press. Can be separated. The storage time in the storage tank is not particularly limited as long as it is about 1 day or more. Therefore, it may be stored for a long time, and the stored reactant may be transferred to a second reactor as needed to add water to elute, so that the present invention can continuously recover zinc sulfate.

Hereinafter, an Example is given and this invention is demonstrated concretely. However, the present invention is not limited by these examples.

Example 1

10 kg of dust (in dust, zinc content: 26%) are placed in a rotary reactor (30) containing steel balls through the first hopper 10, while 5 kg of concentrated sulfuric acid (98%) is poured into the sulfuric acid inlet tube (31). Through a rotary reactor rotating at about 17 rpm / min through. The reaction mixture from the reactor is passed to the second hopper 40 and passed through the second screw conveyor to the storage tank 60. At this time, the generated gas is adsorbed to the scrubber 42 through the discharge pipe 41 in the upper portion of the second hopper 40, and the adsorbed gas is treated separately. Collect the reactants stored in the storage tank 60 and transfer to the second reactor, add 30 liters of water to the reactants and stir while maintaining the reaction temperature at 85 ㅁ 3 ℃ to the pH of the reactants to 4.0 to 4.5 On the filter press, zinc sulfate and insoluble matters were separated. This solidified to obtain zinc sulfate, which was dried in an oven at 250 ° C. for 3 hours, and weighed to give a weight of about 6.31 kg (yield: about 98%). In addition, the obtained zinc sulfate was analyzed and found to have an iron content of about 42 ppm.

As described above, according to the present invention, the electric dust and concentrated sulfuric acid are continuously injected into the ball mill rotary reactor through the first hopper and the sulfuric acid inlet tube, and the reaction mixture passing through the second hopper is collected in a storage tank through a screw conveyor. It reacts at -50 degreeC or more for 1 day. The reaction mixture reacted in this storage tank is transferred to a second reactor, water is added thereto to elute zinc sulfate into an aqueous solution, and zinc sulfate and insoluble matters are continuously treated with a filtering device to treat zinc sulfate continuously. It is a useful invention that can be recovered in high yield.

Claims (4)

Continuously injecting dust and concentrated sulfuric acid into the electric furnace while driving the rotary reactor 30 containing the ball mill, and receiving the reaction mixture from the second hopper 40 passing through the rotary reactor, the storage tank 60 through the second screw conveyor After the storage tank was stored at 30 to 50 ° C. for at least about 1 day, and transferred to the second reactor, about 3 times the amount of water was added to the amount of the lowest dust, and the temperature was maintained at about 70 to 90 ° C. A method of recovering zinc sulfate, characterized in that the mixture is stirred until the pH is 4 to 4.5 and then filtered. The method of claim 1, wherein the concentrated sulfuric acid is at least 98% sulfuric acid, and the amount of concentrated sulfuric acid added is about 1.4 to 1.8 times by weight based on the zinc content in the electric dust. The method according to claim 1, wherein the exhaust gas, such as hydrogen chloride gas or water vapor, which is discharged to the rotary reactor, is adsorbed and removed by using a scrubber (42) through the discharge pipe (41). A first hopper 10 for electric dust injection, a first screw conveyor for transferring the hopper from the hopper to the rotary reactor 30, a rotary reactor 30 containing steel balls, and containing a reactant from the rotary reactor A device for recovering zinc sulfate, comprising a second hopper (40) and a second screw conveyor for transporting the reaction mixture in the hopper (40) to a storage tank (60).

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