KR101503750B1 - Recovery Method of Zinc(Zn) - Google Patents

Abstract

The present invention relates to a recovery method of metal zinc comprising: a leaching process by mixing low concentration sulfuric acid from 2 to 3 mole to steel making dust passing through washing and filtration at a proportion of 1 : 2 (wt%); an aeration process to improve the purity during the leaching process; and an electrolytic process by controlling 30 voltage and 3 current at a distance of 50 mm between the electrodes from pH6 sulfuric acid zinc solution. The present invention can economically reduce the used amount of sulfuric acid and maximize the purity of the zinc to be obtained.

Description

{Recovery Method of Zinc (Zn)}

The present invention relates to a method for recovering metal zinc from steelmaking dust, and more particularly, to a method for recovering metal zinc from steelmaking dust that can maximize the purity of zinc obtained while economically reducing the amount of sulfuric acid used.

Generally, electric arc furnace (EAFD) generated by arc between graphite electrode and steel scrap in electric steelmaking furnace which melts scrap metal scrap is industrial waste containing a lot of harmful nonferrous metal, 40% zinc, 20-40% iron, about 5% lead, and chromium, cadmium, copper, tin, manganese, silica, alumina, limestone, sulfides and chlorides. This steelmaking dust is not only difficult to be landfilled due to the increasingly strong environmental regulations, but also poses the problem of treating steel dusts without landfilling due to pollution of river or soil caused by leachate containing hazardous metallic substances such as lead, copper and cadmium during landfilling Therefore, it is important to safely and economically treat steelmaking dust containing harmful heavy metals. As a result, there are various methods of saving steelmaking dust processing cost by recovering zinc from steelmaking dust and recycling it as a resource.

The pyrometallurgical method and the hydrometallurgical method are well known as the method of recovering zinc from the electric furnace steel dust. The thermal metallurgical method can separate all of the zinc from the dust, but it requires a lot of energy to introduce a reducing agent such as expensive coke and a high-temperature atmosphere, and the separation facility for separating the zinc from the steel dust is expensive Not only is it not economical, but the disadvantage here is to obtain zinc oxide which is low in purity. The wet metallurgical method is a process of obtaining zinc from ZnS, which is a primary galvanizing iron, and can obtain high purity metal zinc or coral zinc as compared with a thermal metallurgical method, but it has a disadvantage that it can not leach zinc ferrite which is a main component of steelmaking dust. In recent years, as a method of recovering zinc from steel making dust, a method of decomposing zinc ferrite particles by leaching steelmaking dust in a high-temperature acid is used. In recent years, the process of obtaining sulfuric acid and zinc from ZnS has been commercialized, and all processes are developing accordingly.

Among the methods for recovering zinc from steelmaking dust, methods for leaching and recovering using sulfuric acid have been proposed. However, since the amount of sulfuric acid is still too much, economical efficiency is low and commercialization is not realized in practice .

It is an object of the present invention to provide a method for recovering metal zinc from steelmaking dust which can maximize the purity of zinc obtained while economically reducing the amount of sulfuric acid used.

In order to achieve the above object, the present invention provides a method for recovering zinc from steelmaking dust (electric furnace dust) generated in an electric furnace steelmaking process, comprising the steps of: adding 2M to 3M (low concentration) sulfuric acid 1: 2 (% by weight); Aeration step for improving the purity during the leaching step; And a step of electrolyzing in a pH 6 zinc sulfate solution at a distance of 50 mm between the electrodes, under the control of a 30 V voltage 3A current.

Further, a method for recovering zinc from steelmaking dust (electric furnace dust) generated in an electric furnace steelmaking process, comprising: a washing step of washing and filtering the steelmaking dust; A leaching step in which 2M to 3M (low concentration) sulfuric acid is mixed and leached at a ratio of 1: 2 (weight%) to the steel making dust subjected to the washing step; A leaching-aeration process in which the leaching step is followed by leaching of 2M to 3M (low concentration) sulfuric acid at a ratio of 1: 2 (weight%) and leaching simultaneously for improving purity; And an electrolytic process in which electrolysis is carried out in a pH 6 zinc sulfate solution at a distance of 50 mm between the electrodes through the control of a 30 V voltage 3A current.

The leaching time in the leaching process is 2 hours, and is repeated at least twice.

The aeration time is characterized by 90 to 180 minutes.

The anode of the electrode is characterized by platinum or lead.

As described above, the present invention has the effect of maximizing the purity of the seed obtained while economically reducing the amount of sulfuric acid used.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims and their equivalents. Of course, such modifications are within the scope of the claims.

FIG. 1 is a graph showing the results of leaching experiments of low-concentration sulfuric acid over time in the metal zinc recovery method of the present invention,
2 is a graph showing the results of continuous leaching in the metal zinc recovery method of the present invention,
3 is a graph showing a result of a Lab Scale simulation of a YC factory in the metal zinc recovery method of the embodiment of the present invention,
FIG. 4 is a graph showing the amount of zinc electrolyzed in actual steel dust-treated water in the metal zinc recovery method of the embodiment of the present invention,
FIG. 5 is a graph showing the EDX mapping of zinc taken from an artificial zinc solution in the metal zinc recovery method of the present invention,
6 is a graph showing the concentration of zinc in the electrolyte of each electrode in the metal zinc recovery method of the embodiment of the present invention,
FIG. 7 is a graph showing the concentration of zinc in the electrolyte according to the electrode interval in the metal zinc recovery method of the present invention,
8 is a graph showing the results of iron removal in the metal zinc recovery method of the embodiment of the present invention,
9 is a process chart sequentially showing a metal zinc recovery method of an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

In addition, the terms described below are defined in consideration of the functions of the present invention, which may vary depending on the user, the intention or custom of the operator, and the like.

Therefore, it goes without saying that the definition should be based on the contents throughout this specification.

The metal zinc recovery method of the present invention comprises: a leaching step of mixing 2M to 3M (low concentration) sulfuric acid in a ratio of 1: 2 (weight%) to steel making dust subjected to washing and filtration and repeating at least twice for 2 hours; A process of aeration for 90 to 180 minutes to improve the purity during the leaching process and a process for electrolysis in a zinc sulfate solution at a pH of 6 in the form of platinum or lead, .

Further, as shown in Fig. 9, a washing process for washing and filtering the steel making dust; A leaching step in which 2M to 3M (low concentration) sulfuric acid is mixed and leached at a ratio of 1: 2 (weight%) to the steel making dust subjected to the washing step; A leaching-aeration process in which the leaching step is followed by leaching of 2M to 3M (low concentration) sulfuric acid at a ratio of 1: 2 (weight%) and leaching simultaneously for improving purity; And an electrolytic process in which the electrolytic solution is electrolyzed in a pH 6 zinc sulfate solution at a distance of 50 mm between the electrodes through the control of a 30V voltage 3A current.

In order to reduce the amount of sulfuric acid used and ensure economical efficiency, the present invention has been conducted to leach with 0.5 M, 1 M, 2 M and 3 M low-sulfuric acid. The high liquid ratio proceeded to 1: 2 according to the result of the preliminary experiment and the verification experiment which had been carried out. FIG. 1 is a graph showing the results of leaching of low-concentration sulfuric acid with time, and FIG. 2 is a graph showing the results of continuous leaching.

As the concentration of sulfuric acid increased, leaching concentration and recovery rate increased. Considering that the recovery rates of 2M and 3M are not significantly different, and the difference of sulfuric acid between 2M and 3M is about 97kg per ton, the optimum concentration of sulfuric acid is 2M.

In the continuous leaching experiment, leaching was carried out up to 4 times, but most of the zinc was leached twice. In the leaching three times and four times, a small amount of zinc was leached and the optimum leaching number was judged to be two.

During the leaching process, aeration was applied to the leaching process to increase the purity of the leached metal zinc. The aeration was performed using Air2000 of RESUN, and the flow rate was 1.8 L / min. Experimental results show that the process without aeration leached about 2300 ppm of Fe in 2 hours and almost similar after 2 hours. The aeration process was about 2.5 ppm at 30 minutes and 0.1 ppm at 2 hours. From the above results, the appropriate time for aeration is estimated to be about 2 hours.

In addition, Lab Scale simulation of the YC plant was conducted. Neutral leaching was carried out for 120 minutes, and acid leaching was carried out for 120 minutes after centrifugation for 240 minutes. In neutral leaching, recovery was less than about 10%, and most leaching occurred in acidic leaching. There were many differences from the existing experimental conditions, but there was no significant difference in the recovery rate. Considering that 15 kg of Na ₂ CO _3, 15 kg of MnO, 5 kg of B-naphthol and 8 kg of ZnO are supplied in a large amount, and the time is delayed due to the combination of neutral leaching and acid leaching, It is judged to be insufficient. 3 is a graph showing a result of a Lab Scale simulation of a YC factory.

In addition, when the graphite electrode was used, the color of the electrolyte became turbid due to the continuous elution of carbon, and the amount of zinc precipitation was significantly lower than that of the platinum electrode. When zinc electrodes were used, the zinc ions were continuously eluted, resulting in increased concentration and reduced recovery efficiency. Platinum electrode recovered from 120 minutes up to 99%, which is considered to be the most ideal electrode.

As shown in the figure, as the gap between the electrodes is narrower, the electromotive force generated between the electrodes becomes higher, and the amount of recovered zinc increases. However, when the distance between the electrodes is too narrow as compared with the recovered zinc, contact of the electrode due to the recovered zinc occurs, . Therefore, after estimating the amount of zinc recovered, the size and spacing of the electrodes should be determined.

4 is a graph showing the amount of zinc electrolytically collected in actual steelmaking dust-treated water. As a result, the recovery rate of zinc from steelmaking dust treated water can be recovered up to 88 ~ 90%. After that, if the high pH condition and the removal rate of the impurities are increased, it is considered that the electrolytic recovery of zinc of 95% or more is possible.

As shown in FIG. 5, it can be confirmed that a high amount of sulfur and iron are present in the actual steelmaking dust-treated water. According to the above results, high zinc electrolytic collection efficiency is shown. However, when the metal such as iron is present, it can be recovered. If the concentration of impurities is reduced, high purity of zinc may be exhibited.

As shown in Table 1 below, the Lab Scale experimental process and the economical evaluation of the process of the YC plant were conducted and compared. The cost of transportation, sales and administrative expenses, labor costs, financial expenses and depreciation were the same, and as a result of the economic evaluation, the Lab Scale process cost difference of 93,009,812 won / month and 4,606,984 won / month. The main cause of the difference is the consumption of unnecessary chemicals such as MnO, B-naphthol, ZnO, and NaNO ₂ compared with the conventional process. If the YC factory process is converted into the existing Lab Scale process, it will save KRW5,500,000 a year.

revenue Zinc sales unit price 235,629,108 won / month sub Total 235,629,108 won / month expenditure Cost of sales 114,583,296 yuan / month (Lab Scale process)
119,190,280 yuan / month (YC factory process) SG & A expenses $ 16,786 / month Financial expenses and
Depreciation cost 11,250,000 won / month sub Total 142,619,296 won / month (Lab Scale process)
147,226,280 yuan / month (YC factory process) Profit Revenue - Spend 93,009,812 won / month (Lab Scale process)
88,402,828 won / month (YC factory process)

6, 7, and 8, in order to determine the optimal conditions for recovery of zinc in the steelmaking dust in the leaching step, the concentration of zinc, the concentration of sulfuric acid, the number of leaching, The recovery rate was compared.

 The concentration of sulfuric acid showed a tendency to increase as the concentration increased, but 2M sulfuric acid was considered to be most appropriate considering the economical efficiency.

In the leaching step, the number of times of leaching proceeded up to 4 times, but when the second leaching was carried out, most of the zinc in the dust was leached out.

In the case of aeration for improving the purity in the aeration process, the aeration proceeded up to 12 hours, but it was confirmed that most of the iron was precipitated and removed within 2 hours.

The YC plant's process was reduced to Lab scale. As a result, there was no significant difference in the recovery rate, but it is expected to be costly in the future due to unnecessary supply of chemicals and time delay.

As shown in Fig. 4, in order to derive the optimum condition for recovery of zinc electrolytic solution in actual steel dust-treated water in the electrolytic process, the amount of zinc electrolytically collected in accordance with pH, electrolyte concentration, Were compared.

As the reaction progresses, the lowering of the pH causes the re-elution of the zinc, resulting in a lower efficiency. Thus, it has been confirmed that the zinc recovery efficiency is enhanced when the initial experiment is performed at a relatively high pH.

Through the adjustment of the interval between the electrodes and the adjustment of the voltage and current, the largest amount of zinc was recovered at 30 V and 3 A due to the deterioration of the electromotive force due to the impurities and the loss of the electrode due to the high heat at a too low or high voltage Respectively.

The use of platinum (lead) as the anode of the electrode was the most stable. When the carbon electrode or the zinc electrode was used, it was difficult to proceed the electrolytic collection smoothly due to the damage of the electrode.

Although the recovery efficiency is increased as the distance between the electrodes is closer, caution must be exercised because electrolytic collection may occur due to contact between the electrodes due to the collected zinc.

Finally, it is considered that the higher zinc recovery efficiency is obtained by increasing the initial pH in the electrolyte and reducing the concentration of impurities to a minimum.

Table 2 shows the optimum conditions for extracting metallic zinc with high purity by reducing the amount of sulfuric acid used during the leaching process and the electrolytic process.

Conditions Values spit
Out
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tablet High liquid fee 1: 2 Sulfuric acid concentration 2M Leaching time 2 hr Number of leaching Episode 2 Aeration time 2 hr I'm
year
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tablet PH at electrolysis pH 6 Voltage 30V electric current 3A Spacing of electrodes 50mm anode Platinum (lead) cathode zinc

Claims (5)

A method for recovering zinc from steelmaking dust (electric furnace dust) generated in an electric furnace steelmaking process,
A leaching step in which 2M to 3M (low concentration) sulfuric acid is mixed in a ratio of 1: 2 (weight%) to steel making dust subjected to washing and filtration and leaching time is 2 hours and leaching is repeated at least twice;
An aeration process for improving the purity during the leaching process; And
wherein the electrolytic solution is electrolyzed in a pH 6 zinc sulfate solution at a distance of 50 mm between the electrodes through adjustment of a 30V voltage 3A current. delete The method according to claim 1,
And the aeration time is from 90 minutes to 180 minutes. The method according to claim 1,
Wherein the anode of the electrode is platinum or lead. A method for recovering zinc from steelmaking dust (electric furnace dust) generated in an electric furnace steelmaking process,
A washing step of washing and filtering the steel making dust;
A leaching step in which 2M to 3M (low concentration) sulfuric acid is mixed and leached at a ratio of 1: 2 (weight%) to the steel making dust subjected to the washing step;
A leaching-aeration process in which the leaching step is followed by leaching of 2M to 3M (low concentration) sulfuric acid at a ratio of 1: 2 (weight%) and leaching simultaneously for improving purity; And
wherein the electrolytic process is electrolyzed in a pH 6 zinc sulfate solution at a distance of 50 mm between the electrodes under the control of a 30V voltage 3A current.

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