Method for recycling fluorine from copper smelting flue gas

Abstract

The present application relates to the technical field of wastewater treatment, and specifically discloses a method for recycling fluorine from copper smelting flue gas, which comprises the following steps: adding water glass with a certain concentration into flue gas scrubbing liquid in a certain proportion, obtaining waste acid original solution by power wave scrubber, adding potassium permanganate into the waste acid original solution, obtaining transformation slag and post-transformation liquid, adding water and alkaline compounds into the transformation slag for hydrolysis, obtaining neutralization liquid, adding oxidizing agent and reducing agent into the neutralization liquid, obtaining purification slag and post-purification liquid, obtaining crude potassium fluoride crystal by concentrating and crystallizing the post-purification liquid, and obtaining refined potassium fluoride crystal and post-recrystallization liquid by recrystallizing the crude potassium fluoride crystal. The method can recycle most of the fluorine-containing pollutants in the copper smelting flue gas, and convert them into potassium fluoride, an important industrial product, which not only solves the corrosion of fluorine to process equipment and the pollution to the environment, but also greatly improves the economic benefits of enterprises.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wastewater treatment, and particularly relates to a method for recycling fluorine from copper smelting flue gas. BACKGROUND

[0002] Fluorine in copper ore is mainly fluorite, fluorite, sericite and phosphate ore. In the smelting process, part of the fluorine enters the smelting slag as silicon tetrafluoride, and the rest of the fluorine enters the flue gas as hydrogen fluoride gas, which enters the acid making system after the waste heat boiler and the electric bag dust collector, and brings great harm to the acid making system. Moreover, if the fluorine cannot be removed in time in the early stage of acid making, the fluorine will transfer to the rear end of the device and cause serious consequences. The main performance is the corrosion of the porcelain ring, porcelain tile, catalyst and other materials containing silicon dioxide in the equipment, and the corrosion of the metal material.

[0003] The traditional method for purifying fluorine in flue gas is to add water glass in the acid making purification process to fix the fluorine in the flue gas in the form of sodium fluorosilicate into waste acid, and then to neutralize and remove the fluorine by adding lime milk solution. Since sodium fluorosilicate will react with alkali, the fluorine fixed in the water glass will be redissolved into waste water, and then calcium fluoride will be generated by using fluorine ions and calcium ions to precipitate and remove most of the fluorine.

[0004] However, although the above process can remove most of the fluorine in the waste water, it prolongs the fluorine removal process, generates a large amount of fluorine-containing waste residue, increases the difficulty of subsequent treatment of the waste residue, and the fluorine is not used in a valuable way, so we need to propose a method for recycling fluorine from copper smelting flue gas to solve the above problems, so that the fluorine in the flue gas can be recycled and utilized. SUMMARY

[0005] The purpose of the present application is to provide a method for recycling fluorine from copper smelting flue gas, which can effectively recycle and utilize the fluorine in the flue gas to solve the problems raised in the background art.

[0006] To achieve the above purpose, the present application adopts the following technical scheme:

[0007] A method for recycling fluorine from copper smelting flue gas, comprising the following steps:

[0008] S1, mixing a water glass solution with a content of 10%-40% with a flue gas washing liquid to obtain a mixed washing liquid, and sending the mixed washing liquid into a dynamic wave scrubber to wash the flue gas to obtain a fluorine-containing waste acid stock solution;

[0009] S2, determining the total content of sodium fluorosilicate in the waste acid stock solution, and determining the amount of potassium permanganate required for reaction with sodium fluorosilicate according to the total content;

[0010] S3, the waste acid stock solution and potassium permanganate after precision filtration are mixed and heated, and fully mixed and uniformly reacted;

[0011] S4, after the reaction is completed, the reaction solution is allowed to stand for 10-30 min, and then filtered and washed to obtain a transformation residue and a post-transformation liquid;

[0012] S5, the transformation residue is dissolved with water, mixed and heated, and an alkaline compound is added to fully mix and uniformly react, and a neutralization liquid is obtained after the reaction is completed;

[0013] S6, an oxidizing agent and a reducing agent are added to the neutralization liquid to remove excess manganese ions and permanganate ions in the solution, and the purified residue and the post-purification liquid are obtained after the reaction is completed and hot filtration;

[0014] S7, the post-purification liquid is concentrated and crystallized, filtered and washed to obtain a crude crystalline potassium fluoride solid and a post-crystallization liquid;

[0015] S8, after recrystallization of the crude crystalline potassium fluoride solid, a refined crystalline potassium fluoride solid and a post-recrystallization liquid are obtained.

[0016] Preferably, in step S1, the mass fraction of the water glass solution in the mixed washing liquid is 1%-2%, and the dynamic wave scrubber is a foam zone formed by high-speed reverse collision of gas-liquid two-phase to realize removal of pollutants in the flue gas. After washing treatment by the dynamic wave scrubber, the residual fluoride content in the flue gas is less than or equal to 1 mg / Nm 3 .

[0017] Preferably, in step S2, the molar ratio of the amount of potassium permanganate added to the sodium fluosilicate content in the waste acid stock solution is 2-6:1.

[0018] Preferably, in step S3, the heating and mixing reaction conditions of the waste acid stock solution and potassium permanganate are as follows: the reaction temperature is 75-95℃, and the reaction time is 6-15 h.

[0019] Preferably, in step S4, the reaction liquid after standing is subjected to solid-liquid separation by a solid-liquid separation device to obtain a separation solid and a separation liquid. The separation solid is washed with deionized water for multiple times until no impurities required to be removed are detected in the separation solid. Finally, the washed separation solid is dried to obtain a transformation residue, and the separation liquids washed multiple times are mixed together to form a post-transformation liquid, which is subjected to treatment in a wastewater treatment system.

[0020] Preferably, in step S5, the alkaline compound is set to one or more of potassium hydroxide, potassium carbonate and potassium bicarbonate, and the amount of the alkaline compound is 1.2-1.8 times the amount of the alkaline compound required for the reaction with fluosilicate.

[0021] Preferably, when the transformation slag is dissolved with water, the transformation slag is first added into a proper amount of water, stirred to dissolve completely, then the water solution containing the transformation slag is heated to 70-100 DEG C, and then the alkaline compound is slowly added to carry out neutralization reaction, the neutralization reaction time is 2-5h, the liquid-solid ratio is 10-20:1, the reaction end point pH is 9-11, and the reaction needs constant stirring to ensure sufficient reaction.

[0022] Preferably, in step S6, the oxidizing agent is one or both of potassium permanganate and sodium permanganate, and the reducing agent is formic acid.

[0023] Preferably, the oxidizing agent and the reducing agent are added in the following way: a small amount of oxidizing agent is first added to convert the residual manganese ions in the solution into manganese dioxide precipitate, when the solution color changes from colorless to purple red, it indicates that the permanganate is excessive and the manganese ions in the solution are completely precipitated, at this time, the reducing agent is slowly added to convert the excessive permanganate into manganese dioxide precipitate, when the solution color changes from purple red to colorless, it indicates that the permanganate in the solution is completely converted into manganese dioxide precipitate, and the reaction reaches the end point.

[0024] Preferably, in step S7, when the purified solution is concentrated and crystallized, the mass of the concentrated solution is 5%-10% of the mass before concentration, and the crystallization temperature is greater than 45 DEG C.

[0025] Compared with the prior art, the method for recycling fluorine from copper smelting flue gas has the following advantages:

[0026] 1. In the method, water glass with a certain concentration is added into the flue gas washing liquid in a certain proportion, the waste acid stock solution is obtained by washing the flue gas through a dynamic wave scrubber, potassium permanganate is added into the waste acid stock solution, and the mixture is uniformly heated and stirred, then the transformation slag and the transformed liquid are obtained after standing, the transformation slag is hydrolyzed by adding water and an alkaline compound to obtain a neutralization liquid, an oxidizing agent and a reducing agent are added into the neutralization liquid to precipitate excessive permanganate and manganese ions in the solution, the purified slag and the purified liquid are obtained, and the crude potassium fluoride crystal is obtained after the purified liquid is concentrated and crystallized, then the crude potassium fluoride crystal is recrystallized to obtain refined potassium fluoride crystal and recrystallized liquid.

[0027] 2. The method utilizes the existing wastewater treatment process equipment, improves the medicament adding structure in the existing wastewater treatment process, reduces the calcium ion adding amount, and reduces the system fouling degree, so that the fluorine in the flue gas is recycled and utilized. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 A flow chart of the present application. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. The specific embodiments described herein are only used to explain the present application, and are not used to limit the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application. Embodiment 1

[0030] The present application provides a method for recycling fluorine from copper smelting flue gas as shown in the following steps: Figure 1

[0031] S1, a water glass solution with a content of 10%-40% is mixed with a flue gas washing liquid to obtain a mixed washing liquid, and the mixed washing liquid is sent into a dynamic wave scrubber to wash the flue gas to obtain a fluorine-containing waste acid stock solution;

[0032] The mass fraction of the water glass solution in the mixed washing liquid is 1%-2%, and the dynamic wave scrubber utilizes the high-speed reverse collision of gas-liquid two phases to form a turbulent foam zone, so that the pollutants in the flue gas are removed. After washing treatment by the dynamic wave scrubber, the residual fluoride content in the flue gas is less than or equal to 1 mg / Nm 3 .

[0033] S2, the total content of sodium fluorosilicate in the waste acid stock solution is determined, and the amount of potassium permanganate required for reaction with sodium fluorosilicate is determined according to the total content; the molar ratio of the amount of potassium permanganate to the content of sodium fluorosilicate in the waste acid stock solution is 2-6:1.

[0034] S3, the waste acid stock solution and potassium permanganate after precision filtration are mixed and heated, and are fully mixed and uniformly reacted; the waste acid stock solution and potassium permanganate are mixed and reacted under the following conditions: the reaction temperature is 75-95℃, and the reaction time is 6-15h.

[0035] S4, after the reaction is completed, the reaction liquid is filtered and washed after standing for 10-30min to obtain a transformed slag and a transformed liquid;

[0036] The reaction liquid after standing is subjected to solid-liquid separation by a solid-liquid separation device to obtain separated solids and separated liquid, the separated solids are washed with deionized water for multiple times until no impurities required to be removed are detected in the separated solids, and finally the washed separated solids are dried to obtain the transformed slag, and the separated liquid washed multiple times is mixed together to form the transformed liquid, which is sent into a waste water treatment system for treatment. ​

[0037] S5, dissolving the transformation slag with water, mixing and heating, and adding an alkaline compound to fully mix and react, obtaining a neutralized solution after the reaction is completed;

[0038] The alkaline compound is set as one or more of potassium hydroxide, potassium carbonate and potassium bicarbonate, and the amount of the alkaline compound is 1.2-1.8 times the theoretical amount required for the reaction with fluorosilicate.

[0039] When the transformation slag is dissolved with water, the transformation slag is first added to an appropriate amount of water, stirred to fully dissolve, and then the aqueous solution containing the transformation slag is heated to 70-100℃, and then the alkaline compound is slowly added to perform the neutralization reaction. The neutralization reaction time is 2-5h, the liquid-solid ratio is 10-20:1, and the reaction endpoint pH is 9-11. Constant stirring is required during the reaction to ensure full reaction.

[0040] S6, adding an oxidizing agent and a reducing agent to the neutralized solution to remove excess manganese ions and permanganate ions in the solution, and filtering the purified slag and the purified solution while hot after the reaction is completed;

[0041] The oxidizing agent is set as one or both of potassium permanganate and sodium permanganate; the reducing agent is set as formic acid. The addition method of the oxidizing agent and the reducing agent is: first add a small amount of oxidizing agent to convert the residual manganese ions in the solution into manganese dioxide precipitate, when the color of the solution changes from colorless to purple red (the color of permanganate itself), it means that the permanganate is excessive, and the manganese ions in the solution are completely precipitated, at this time, slowly add the reducing agent to convert the excess permanganate into manganese dioxide precipitate, when the color of the solution changes from purple red to colorless, it means that the permanganate in the solution is completely converted into manganese dioxide precipitate, and the reaction reaches the endpoint.

[0042] S7, concentrating and crystallizing the purified solution, filtering and washing to obtain crude crystalline potassium fluoride solid and a crystallized solution; when the purified solution is concentrated and crystallized, the mass of the concentrated solution is 5%-10% of the mass before concentration, and the crystallization temperature is greater than 45℃. If the crystallization temperature is lower than 45℃, potassium fluoride will be precipitated in the form of dihydrate potassium fluoride.

[0043] S8, after recrystallizing the crude crystalline potassium fluoride solid, refined crystalline potassium fluoride solid and a recrystallized solution are obtained. Example 2

[0044] According to the method provided in Example 1, the first verification of actually recovering fluorine from copper smelting flue gas is verified, and the verification results are as follows:

[0045] 1. Detect the content of fluorine (F), sulfur (S) and nitrogen (N) in the flue gas mixed washing solution, and the detection results are shown in the following table:

[0046] Category F S N Content (mg / L) 23.45 136.26 26.84

[0047] 2. The water glass solution with a content of 10% is mixed with the flue gas scrubbing solution to obtain a mixed scrubbing solution, and the mixed scrubbing solution is sent into the dynamic wave scrubber to scrub the flue gas, to obtain a fluorine-containing waste acid stock solution, and the content of fluorine (F) in the waste acid stock solution is 23.06 mg / L, indicating that 98% of fluorine in the flue gas scrubbing solution can be extracted by the dynamic wave scrubber;

[0048] 3. Potassium permanganate is added to the waste acid stock solution, and the molar ratio of the content of fluorine sodium silicate in the waste acid stock solution to the addition amount of potassium permanganate is 6:1, so that the waste acid stock solution and the potassium permanganate are subjected to a heating and mixing reaction, the reaction temperature is 75°C, the reaction time is 15 h, and after standing for 10-30 min, filtration and washing are performed to obtain a transformed slag and a transformed liquid, the transformed liquid is sent to a waste water treatment system for treatment, and the content of fluorine in the transformed slag is detected to be 22.76 mg / L, and the recovery rate of fluorine is 98.7%.

[0049] 4. The transformed slag is dissolved with water, mixed and heated to 70°C, and potassium hydroxide is added and fully mixed and uniformly reacted, the reaction time is 5 h, and the liquid-solid ratio is 10:1, and after the reaction is completed, a neutralized liquid is obtained, potassium permanganate and formic acid are added to the neutralized liquid to remove excess manganese ions and permanganate ions in the solution, and after the reaction is completed, the hot filtration is performed to obtain a purified slag and a purified liquid, the purified slag is sent to a manganese dioxide refining process, the content of fluorine in the purified liquid is detected to be 22.44 mg / L, and the recovery rate of fluorine is 98.6%.

[0050] 5. The purified liquid is concentrated and crystallized, the crystallization temperature is 50°C, and filtration and washing are performed to obtain a crude crystalline potassium fluoride solid and a crystallized liquid, and then the crude crystalline potassium fluoride solid is subjected to recrystallization to obtain a refined crystalline potassium fluoride solid and a recrystallized liquid, the content of fluorine in the refined crystalline potassium fluoride solid is detected to be 22.1 mg / L, and the recovery rate of fluorine is 98.5%.

[0051] It is verified that by using the method, 98% of fluorine can be recovered from the copper smelting flue gas, and converted into potassium fluoride, an important industrial product, which not only solves the corrosion of fluorine to process equipment and pollution to the environment, but also greatly improves the economic benefit of enterprises. Example 3

[0052] According to the method provided in Example 1, a second verification of the actual recovery of fluorine from the copper smelting flue gas is carried out, and the verification results are as follows:

[0053] 1. The content of fluorine (F), sulfur (S) and nitrogen (N) in the flue gas mixed scrubbing liquid is detected, and the detection results are shown in the following table:

[0054] Category F S N Content (mg / L) 26.6 142.26 28.43

[0055] 2. The water glass solution with a content of 25% is mixed with the flue gas scrubbing solution to obtain a mixed scrubbing solution, and the mixed scrubbing solution is sent into the dynamic wave scrubber to scrub the flue gas to obtain a fluorine-containing waste acid stock solution, and the content of fluorine (F) in the waste acid stock solution is 25.96 mg / L, indicating that 97.6% of fluorine in the flue gas scrubbing solution can be extracted by the dynamic wave scrubber;

[0056] 3. Potassium permanganate is added to the waste acid stock solution, and the molar ratio of the content of fluorine sodium silicate in the waste acid stock solution to the addition amount of potassium permanganate is 3:1, so that the waste acid stock solution and the potassium permanganate are subjected to a heating and mixing reaction, the reaction temperature is 83°C, the reaction time is 10 h, and after standing for 10-30 min, filtration and washing are performed to obtain a transformed slag and a transformed liquid, the transformed liquid is sent to a waste water treatment system for treatment, and the content of fluorine in the transformed slag is 25.52 mg / L, and the recovery rate of fluorine is 98.3%.

[0057] 4. The transformed slag is dissolved with water, mixed and heated to 85°C, and potassium carbonate is added and fully mixed and uniformly reacted, the reaction time is 3 h, and the liquid-solid ratio is 15:1, and after the reaction is completed, a neutralized liquid is obtained, sodium permanganate and formic acid are added to the neutralized liquid to remove excess manganese ions and permanganate ions in the solution, and after the reaction is completed, the hot filtration is performed to obtain a purified slag and a purified liquid, the purified slag is sent to a manganese dioxide refining process, the content of fluorine in the purified liquid is 25.16 mg / L, and the recovery rate of fluorine is 98.6%.

[0058] 5. The purified liquid is concentrated and crystallized, the crystallization temperature is 60°C, and filtration and washing are performed to obtain a crude crystalline potassium fluoride solid and a crystallized liquid, and then the crude crystalline potassium fluoride solid is subjected to recrystallization to obtain a refined crystalline potassium fluoride solid and a recrystallized liquid, the content of fluorine in the refined crystalline potassium fluoride solid is 24.8 mg / L, and the recovery rate of fluorine is 98.56%.

[0059] It is verified that by using the method, 98% of fluorine can be recovered from the copper smelting flue gas and converted into potassium fluoride, an important industrial product, which not only solves the corrosion of fluorine to process equipment and pollution to the environment, but also greatly improves the economic benefit of enterprises. Example 4

[0060] According to the method provided in Example 1, a third verification of the actual recovery of fluorine from the copper smelting flue gas is carried out, and the verification results are as follows:

[0061] 1. The content of fluorine (F), sulfur (S) and nitrogen (N) in the flue gas mixed scrubbing solution is detected, and the detection results are shown in the following table:

[0062] Category F S N Content (mg / L) 25.89 139.68 26.23

[0063] 2. A 40% water glass solution was mixed with a flue gas scrubber to obtain a mixed scrubbing liquid, which was then fed into a power wave scrubber to scrub the flue gas, thereby obtaining a fluorine-containing waste acid stock solution. The fluorine (F) content in the waste acid stock solution was 25.44 mg / L, indicating that 98.3% of the fluorine could be extracted from the flue gas scrubbing liquid by the power wave scrubber.

[0064] 3. Potassium permanganate was added to the waste acid stock solution in an amount corresponding to a molar ratio of 2:1 to the sodium fluorosilicate content in the waste acid stock solution. The waste acid stock solution and potassium permanganate were heated and mixed to react at a reaction temperature of 95° C. for 6.5 h. After standing for 10-30 min, the mixture was filtered and washed to obtain a transformation slag and a transformation liquid. The transformation liquid was treated in a wastewater treatment system. The fluorine content in the transformation slag was detected to be 24.98 mg / L, and the fluorine recovery rate was 98.2%.

[0065] 4. Dissolve the transformation slag in water, mix and heat to 100°C, and add potassium bicarbonate to fully mix and react uniformly. The reaction time is 2 hours, and the liquid-solid ratio is 20:1. After the reaction is completed, obtain a neutralized solution. Add potassium permanganate, sodium permanganate and formic acid to the neutralized solution to remove excess manganese ions and permanganate ions in the solution. After the reaction is completed, filter while hot to obtain purified slag and purified liquid. The purified slag is sent to the manganese dioxide refining process. The fluorine content in the purified liquid is detected to be 24.5 mg / L, and the fluorine recovery rate is 98.1%.

[0066] 5. The purified liquid was concentrated and crystallized at a crystallization temperature of 65°C. The crude crystalline potassium fluoride solid and the crystallized liquid were obtained by filtration and washing. The crude crystalline potassium fluoride solid was then recrystallized to obtain refined crystalline potassium fluoride solid and the recrystallized liquid. The fluorine content in the refined crystalline potassium fluoride solid was detected to be 23.98 mg / L, and the fluorine recovery rate was 97.9%.

[0067] Verification has shown that this method can recover 97.9% of fluorine from copper smelting flue gas and convert it into potassium fluoride, an important industrial product. This not only solves the corrosion of fluorine to process equipment and pollution to the environment, but also greatly improves the economic benefits of the enterprise.

[0068] In summary, a certain concentration of water glass is added to the flue gas scrubbing liquid in a certain proportion, and the waste acid stock solution is obtained by the dynamic wave scrubber for flue gas washing. Potassium permanganate is added to the waste acid stock solution, and it is fully mixed, heated and stirred uniformly. After standing, the transformation slag and the transformed liquid are obtained. The transformation slag is added to water and an alkaline compound to hydrolyze under heating, and the neutralized liquid is obtained. Oxidizing agent and reducing agent are added to the neutralized liquid to precipitate excess permanganate and manganese ions in the solution, and the purified slag and the purified liquid are obtained. After concentration and crystallization, the purified liquid obtains crude potassium fluoride crystals. The crude potassium fluoride crystals are recrystallized to obtain refined potassium fluoride crystals and recrystallized liquid. This method can recover most of the fluorine-containing pollutants in the copper smelting flue gas and convert them into important industrial product potassium fluoride. This method not only solves the corrosion of fluorine on process equipment and pollution on the environment, but also greatly improves the economic benefit of enterprises. This method uses existing wastewater treatment process equipment, improves the reagent adding structure in the existing wastewater treatment process, reduces the amount of calcium ions added, and reduces the degree of system fouling. The fluorine in the flue gas is recycled and utilized as a resource.

[0069] Finally, it should be noted that: the above only for the preferred embodiments of the present application, and not for limiting the present application, although the foregoing detailed description of the present application is made with reference to the foregoing embodiments, for those skilled in the art, it still can be modified to the technical solutions recorded in the foregoing embodiments, or equivalent replacement of some technical features, within the spirit and principles of the present application, any modification, equivalent replacement, improvement, etc. should be included in the protection scope of the present application.

Claims

1. A method for resource recovery of fluorine from copper smelting flue gas, characterized by: The steps include: S1. A water glass solution having a content of 10% to 40% is mixed with a flue gas scrubbing liquid to obtain a mixed scrubbing liquid, and the mixed scrubbing liquid is fed into a power wave scrubber to scrub the flue gas to obtain a fluorine-containing waste acid stock solution; S2, determine the total content of sodium fluorosilicate in the waste acid stock solution, and determine the amount of potassium permanganate required for reacting with the sodium fluorosilicate according to the total content; S3, mixing and heating the waste acid solution that has been precisely filtered and potassium permanganate, and fully mixing and reacting; S4, after the reaction is completed, let it stand for 10-30 minutes, then filter and wash to obtain the transformation residue and the transformation liquid; S5. Dissolve the transformation slag in water, mix and heat, and add an alkaline compound to mix and react thoroughly, and obtain a neutralized solution after the reaction is completed; S6. Adding an oxidizing agent and a reducing agent to the neutralized solution to remove excess manganese ions and permanganate ions in the solution. After the reaction is completed, filtering while hot to obtain purified residue and purified liquid; The oxidizing agent is set to one or both of potassium permanganate and sodium permanganate; the reducing agent is set to formic acid; S7, concentrating and crystallizing the purified liquid, filtering and washing to obtain crude crystalline potassium fluoride solid and crystallized liquid; S8. Recrystallize the crude crystalline potassium fluoride solid to obtain refined crystalline potassium fluoride solid and recrystallized liquid.

2. The method for recovering fluorine from copper smelting flue gas according to claim 1, characterized in that: In step S1, the mass fraction of the water glass solution in the mixed washing liquid is 1%-2%. The dynamic wave scrubber uses the high-speed reverse collision of gas and liquid phases to form a turbulent foam zone, thereby removing pollutants from the flue gas. After the dynamic wave scrubber is washed, the remaining fluoride content in the flue gas is less than or equal to 1 mg / Nm 3 .

3. The method for recovering fluorine from copper smelting flue gas according to claim 2, characterized in that: In step S2, the molar ratio of the amount of potassium permanganate added to the content of sodium fluorosilicate in the waste acid stock solution is 2-6:

1.

4. The method for recovering fluorine from copper smelting flue gas according to claim 3, characterized in that: In step S3, the conditions for the heating and mixing reaction of the waste acid stock solution and potassium permanganate are: reaction temperature of 75-95° C., and reaction time of 6-15 h.

5. The method for recovering fluorine from copper smelting flue gas according to claim 4, characterized in that: In step S4, the reaction liquid after standing is separated into solid and liquid by a solid-liquid separation device to obtain a separated solid and a separated liquid. The separated solid is washed multiple times with deionized water until no impurities to be removed are detected in the separated solid. Finally, the washed separated solid is dried to obtain a transformation residue. The separated liquids washed multiple times are mixed together to form a transformed liquid, which enters the wastewater treatment system for treatment.

6. The method for recovering fluorine from copper smelting flue gas according to claim 5, characterized in that: In step S5, the alkaline compound is set to one or more of potassium hydroxide, potassium carbonate and potassium bicarbonate, and the amount of the alkaline compound is 1.2-1.8 times the amount of the alkaline compound theoretically required for the reaction with fluorosilicate.

7. The method for recovering fluorine from copper smelting flue gas according to claim 6, characterized in that: When the transformation slag is dissolved in water, the transformation slag is first added to an appropriate amount of water and stirred to fully dissolve it. The aqueous solution containing the transformation slag is then heated to 70-100° C., and then an alkaline compound is slowly added to carry out a neutralization reaction. The neutralization reaction time is 2-5 hours, the liquid-solid ratio is 10-20:1, and the reaction end point pH is 9-11. Continuous stirring is required during the reaction process to ensure sufficient reaction.

8. The method for recovering fluorine from copper smelting flue gas according to claim 7, characterized in that: The oxidizing agent and reducing agent are added in the following manner: a small amount of oxidizing agent is first added to convert the residual manganese ions in the solution into manganese dioxide precipitates; when the color of the solution changes from colorless to purple-red, it indicates that there is excess permanganate and the manganese ions in the solution are completely precipitated; at this time, the reducing agent is slowly added to convert the excess permanganate into manganese dioxide precipitates; when the color of the solution suddenly changes from purple-red to colorless, it indicates that all the permanganate in the solution is converted into manganese dioxide precipitates and the reaction reaches the end point.

9. The method for recovering fluorine from copper smelting flue gas according to claim 8, characterized in that: In step S7, when the purified liquid is concentrated and crystallized, the mass of the concentrated solution is 5%-10% of the mass before concentration, and the crystallization temperature is greater than 45°C.

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