A high-chlorine copper soot dechlorination pretreatment method

Abstract

The present application belongs to the technical field of wet dechlorination and desulfurization pretreatment, and particularly relates to a high-chlorine copper soot dechlorination pretreatment method, which comprises the following steps: 1) after copper soot is sequentially subjected to screening and grinding, the copper soot is mixed and stirred with a first additive, leached, filtered and washed to obtain a first filtrate and a first filter residue; 2) soda ash is added to the first filtrate, and the mixture is reacted, filtered and washed to obtain a zinc-containing residue and a second filtrate; dilute sulfuric acid and a second additive are added to the first filter residue, and the mixture is reacted, filtered and washed to obtain a third filtrate and a lead-tin residue; soda ash is added to the third filtrate, and the mixture is reacted, washed and filtered to obtain a fourth filtrate and a copper-containing residue; 3) the second filtrate and the fourth filtrate are evaporated and crystallized to obtain condensed water and a mixed product of sodium chloride and sodium sulfate. The present application uses high-chlorine copper-containing soot as raw material, realizes dechlorination and desulfurization pretreatment, and can obtain a zinc-containing residue, a lead-tin residue, a copper-containing residue and products of sodium chloride and sodium sulfate in stages.

Description

Technical Field

[0001] This invention belongs to the technical field of wet dechlorination and desulfurization pretreatment, specifically relating to a method for dechlorination pretreatment of high-chlorinated copper flue dust. Background Technology

[0002] Currently, my country's non-ferrous metals industry generates approximately 300 million tons of solid waste annually, including smelting flue dust, with a cumulative stockpile of 250 million tons. However, less than 100 million tons are comprehensively utilized, resulting in a utilization rate of only 22%-35%. The metallurgical industry produces large quantities of flue dust containing various metals such as copper, zinc, lead, and tin. Improper handling can cause serious environmental pollution and even endanger human health. At the same time, this flue dust containing valuable metals is also a valuable resource; recycling and utilizing it can create economic value, alleviate the resource crisis, and reduce environmental damage.

[0003] Due to the complex composition and significant fluctuations in phase composition of the flue dust produced during copper smelting, it is currently difficult to establish a unified and standardized processing technology for the comprehensive recovery and resource utilization of valuable metals from copper smelting flue dust. Generally speaking, the comprehensive utilization and processing of copper smelting flue dust resources can be divided into three categories: pyrometallurgical, semi-wet, and fully wet processes.

[0004] Pyrochemical treatment

[0005] Early copper smelting flue dust treatment primarily employed pyrometallurgical processes. Besides rotary kilns, pyrometallurgical treatment of copper smelting flue dust could also be carried out in reverberatory furnaces and electric arc furnaces. Furthermore, to comprehensively recover valuable metals from the flue dust, pyrometallurgical copper plants would also directly return the smelting flue dust to the smelting system. This not only reduced the copper smelting system's raw material processing capacity but also increased the impurity content of the feedstock, decreasing the furnace's processing capacity. Moreover, the cyclical accumulation of impurities such as As and Zn directly impacted the quality of the final product.

[0006] Semi-wet processing

[0007] The "semi-wet process" for treating copper smelting flue dust refers to a process that combines pyrometallurgical and wet methods, which is also one of the main processes for treating copper smelting flue dust at present.

[0008] (1) Copper smelting flue dust from rotary kiln reduction roasting-leaching process undergoes reduction roasting in a rotary kiln. Under conditions such as a temperature of 1150-1200℃, a coke powder ratio of 40%-50%, and a charge residence time of 4.3-4.6h, 96-97% of Zn, 82-85% of Pb, and 90-100% of Cd in the flue dust volatilize and accumulate in the secondary flue dust. Moreover, the enrichment multiple of Pb and Zn can reach 3-3.5 times the original content, and Cd can reach 3.5-4 times the original content. The kiln slag can be sent to the copper system for further copper recovery.

[0009] Good results can be obtained by leaching secondary flue dust with dilute acid. Under the conditions of 5 g / L H₂SO₄ final acid, leaching temperature of 70℃, solid-liquid ratio of 1 / 5 (g / ml), and leaching time of 1-2 hours, the leaching rates of valuable elements after two-stage leaching are: Zn 88%-90%, Cd 80%-82%, and Cu 30%-32%. The leaching rates of As and Fe are 47%-50% and 12%-14%, respectively. The leaching residue can be reduced and smelted to produce crude lead alloy for further recovery of Pb / Bi.

[0010] (2) Sulfation roasting-leaching process

[0011] Copper smelting ash is mixed with concentrated sulfuric acid and sulfatated at 350–450°C. As is volatilized and removed as As₂O₃, which is then collected and recovered by the rotary kiln flue gas. The roasted sand is then leached in water to transfer metals such as Cu and Cd into the aqueous solution. Cu is then extracted using solvent extraction, Fe is removed by oxidation and neutralization, and Cd is precipitated by Zn powder replacement to recover Cu and Cd in stages. Finally, the solution is purified and then evaporated and crystallized to produce zinc sulfate heptahydrate to recover Zn.

[0012] (3) Leaching-blast furnace reduction smelting process

[0013] Given that valuable metals such as Cu, Zn, Pb, and Bi in copper smelting flue dust mainly exist in the form of oxides or sulfates, and that Cu and Zn sulfates are readily soluble in water, while their oxides are readily soluble in dilute sulfuric acid, and that Pb and Bi sulfates or oxides are poorly soluble in water or dilute sulfuric acid, preliminary separation of Cu and Zn from Pb and Bi can be achieved through water leaching or dilute sulfuric acid leaching. This constitutes the theoretical basis of the leaching-blast furnace smelting process.

[0014] The main chemical reactions that occur during the dilute sulfuric acid leaching process of copper smelting ash are:

[0015] CuO + H₂SO₄ = CuSO₄ + H₂O

[0016] CdO + H₂SO₄ = CdSO₄ + H₂O

[0017] PbO + H₂SO₄ = PbSO₄↓ + H₂O

[0018] FeO + H₂SO₄ = FeSO₄ + H₂O

[0019] Bi2O3+2H2SO4=2Bi(OH)SO4↓+H2O

[0020] The leachate, after purification, can separate and extract Cu and Zn, and produce sponge-like Cd. The leaching residue, after washing and drying, is then reduced and smelted in a blast furnace to produce Pb / Bi alloys, which can be further refined to obtain electrolytic Pb and refined Bi. This process has a short flow rate and a high overall recovery rate of various valuable metals, making it suitable for copper smelting ash with high Pb and Zn content.

[0021] wet processing

[0022] The recovery of valuable metal phosphorus (Pb) from copper smelting flue dust primarily employs pyrometallurgical processes, such as reduction smelting in a closed blast furnace to produce Pb / Bi alloys. Alternatively, hydrometallurgical processes can also be used to recover Pb.

[0023] In the leaching-carbonate conversion process, copper smelting flue dust is first leached, and then zinc sulfate heptahydrate is produced from the leachate. The Pb-rich leaching residue undergoes a series of processes including carbonation conversion, dissolution with nitric acid or fluorosilicic acid, and lead precipitation with sulfuric acid, ultimately producing tribasic lead sulfate (P-1) as the final product. Among these processes, carbonation conversion is crucial. Through carbonation conversion, Pb in the Pb-rich residue is transformed from lead sulfate to lead carbonate. The main chemical reactions occurring in each process are as follows:

[0024] PbSO4+(NH4)CO3=PbCO3↓+(NH4)SO4

[0025] PbCO3+H2SiF6=PbSiF6+H2O+CO2↑

[0026] PbSiF6 + H2SO4 = PbSO4↓ + H2SiF6

[0027] The outstanding advantages of the above process are low pollution and low energy consumption, but the Pb recovery rate of this process is relatively low.

[0028] For the high-chlorine copper ash generated during the pyrometallurgical smelting of copper-containing hazardous solid waste, Zn mainly exists as ZnCl, ZnSO4, and ZnO, while Cu mainly exists as CuS, CuSO4, and CuO. To improve the comprehensive utilization level of resources and increase the utilization of secondary resources.

[0029] Therefore, it is of great significance to develop a dechlorination pretreatment process for high-chlorine copper flue dust. Summary of the Invention

[0030] To address the shortcomings of existing technologies, this invention provides a method for dechlorination pretreatment of high-chlorinated copper flue dust.

[0031] The technical solution provided by this invention is as follows:

[0032] A method for dechlorination pretreatment of high-chlorinated copper flue dust includes the following steps:

[0033] 1) After copper ash is sieved and ground in sequence, it is mixed and stirred with the first additive, then water is added and leached in a leaching tank, then filtered and washed to obtain the first filtrate and the first filter residue.

[0034] 2) Add soda ash to the first filtrate obtained in step 1) and react in the first reaction tank, then filter and wash to obtain zinc-containing slag and second filtrate;

[0035] Add dilute sulfuric acid and a second additive to the first filter residue obtained in step 1), react in the second reaction tank, then filter and wash to obtain the third filtrate and lead-tin slag. Add soda ash to the third filtrate, react in the third reaction tank, then wash and filter to obtain the fourth filtrate and copper-containing slag.

[0036] 3) Evaporate and crystallize the second filtrate to obtain condensate and a mixed product of sodium chloride and sodium sulfate;

[0037] The fourth filtrate is evaporated and crystallized to obtain condensate and a mixed product of sodium chloride and sodium sulfate;

[0038] The first additive is added in a proportion of 0.05-0.15 wt%, and the first additive comprises the following components in weight percentage: sodium pyrophosphate 20-55%, sodium hexametaphosphate 15-45%, sodium polyacrylate 15-35%, and polyvinyl alcohol 5-18%;

[0039] The addition ratio of the second additive is 0.02-0.1 wt%, and the second additive includes the following components in weight percentage: 20-55% high carbon fatty alcohol, 12-45% ethylene oxide polymer, 10-35% sodium dodecyl sulfate, 10-25% methyl pentanol, 2-10% cellulose derivative, and 3-8% polyacrylamide.

[0040] Based on the above technical solution, this invention uses high-chlorine copper-containing flue ash as raw material, and by adding auxiliary materials and additives such as sodium hydroxide and sodium carbonate, achieves the purpose of dechlorination and desulfurization pretreatment, and can obtain zinc-containing slag, lead-tin slag, copper-containing slag, and sodium chloride and sodium sulfate products in stages. The copper-containing slag can be used as a raw material for copper smelting, while the zinc-containing slag and lead-tin slag can be sold externally.

[0041] In the first additive:

[0042] Sodium pyrophosphate acts as an emulsifying and dispersing agent;

[0043] Sodium hexametaphosphate acts to prevent the agglomeration of broken particles and maintain the stability of the dispersion; the dispersant is also a surfactant.

[0044] Sodium polyacrylate acts as a chelating agent for metal ions, provides an alkaline buffer, disperses dirt in water, and prevents dirt from re-attaching and depositing on fabrics. Industrial-grade sodium polyacrylate products can be purchased from Zhengzhou Guanda Chemical Products Co., Ltd.

[0045] Polyvinyl alcohol can act as a stabilizer, mainly due to its molecular structure and hydrophilic properties. Polyvinyl alcohol products can be purchased from Ningxia Dadi Circular Development Co., Ltd.

[0046] In the second additive:

[0047] Higher carbon fatty alcohols are used as surfactants and can be purchased from Jiangsu Shengtai Chemical Technology Co., Ltd. as fatty C18-16 alcohol products.

[0048] The role of ethylene oxide polymers is as a non-inorganic compound surfactant and as a reaction catalyst under alkaline conditions. PEG-4000 ethylene oxide condensate products can be purchased from Nantong Hongshen Chemical Co., Ltd.

[0049] Sodium dodecyl sulfate functions as an anionic surfactant.

[0050] Methylpentanol is used as a diluent for surfactants.

[0051] Cellulose derivatives are used as gelling agents and stabilizers. Carboxymethyl cellulose products can be purchased from Sichuan Lanyang Daily Chemical Co., Ltd.

[0052] Polyacrylamide is used for flocculation and drag reduction, effectively reducing the frictional resistance of fluids. It can be purchased from Wujiang Yongjia Chemical Co., Ltd., which offers a series of polyacrylamide (PAM) products.

[0053] Furthermore, the condensate obtained from the evaporation and crystallization of the second filtrate and / or the condensate obtained from the evaporation and crystallization of the fourth filtrate are recycled to the second reaction tank.

[0054] Based on the above technical solution, condensate can be recycled and reused.

[0055] Specifically, in step 1), grind to ≤325 mesh.

[0056] Specifically, in step 1), the temperature in the leaching tank is 55-70℃, the residence time is 0.5-2.4h, and the liquid-to-solid ratio is (2.5-5):1.

[0057] Specifically, in step 2), the temperature in the first reaction tank is 75-93℃, the reaction time is 1.0-2.5h, the pH value is 7-9.5, and the excess coefficient of added soda ash is 1.05-1.2.

[0058] The main reactions in the first reaction tank include:

[0059] ZnCl₂ + Na₂CO₃ = ZnCO₃↓ + NaCl

[0060] ZnSO4 + Na2CO3 = ZnCO3↓ + NaSO4

[0061] Specifically, in step 2), the temperature in the second reaction tank is 65-85℃, the reaction time is 1.5-3.5h, and the pH endpoint value is controlled to be 4.2-6.3 by gradually adding dilute sulfuric acid, with a liquid-to-solid ratio of (2-5):1.

[0062] The main reactions in the second reaction tank include:

[0063] CuS + H₂SO₄ = CuSO₄ + H₂S↑

[0064] CuO + H₂SO₄ → CuSO₄ + H₂O

[0065] The lead and tin slag in copper ash do not react or react in small amounts, thus directly entering the lead-tin slag.

[0066] Specifically, in step 2), the temperature in the third reaction tank is 73-95℃, the reaction time is 1.0-2.5h, and the pH endpoint value is controlled to be 8.5-9.1 by gradually adding soda ash.

[0067] The main reactions in the third reaction tank include:

[0068] CuSO4+2Na2CO3+H2O==Cu2(OH)2CO3↓+2Na2SO4+CO2↑

[0069] This invention employs a wet process, which has the advantages of high leaching rate and minimal environmental impact. The process is simple and easy to control, has low energy consumption, and allows for the classification of waste liquid and residue for resource utilization. Combined with pyrometallurgical processes, it offers significant economic and social benefits and promising application prospects. Attached Figure Description

[0070] Figure 1 This is a flowchart of the dechlorination pretreatment method for high-chlorinated copper flue dust provided by the present invention. Detailed Implementation

[0071] The principles and features of the present invention are described below. The embodiments given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0072] Example 1:

[0073] The present invention uses high-chlorinated copper ash as raw material, which is screened to remove impurities and ground to ≤325 mesh. It is then mixed and stirred evenly with a first additive at a dosage of 0.08%. The main components of the first additive are 45% sodium pyrophosphate, 25% sodium hexametaphosphate, 20% sodium polyacrylate, and 10% polyvinyl alcohol. Water and the mixture are prepared at a liquid-to-solid ratio of 3.5 and sent to a leaching tank. The temperature at the outlet is controlled at 65°C, and the residence time is controlled at 1.5 hours. After leaching, the mixture is filtered and washed. The filter residue is sent to a second reaction tank, and the filtrate is sent to a first reaction tank. The temperature in the first reaction tank is controlled at 82°C, the reaction time is 1.5 hours, and the pH value is 8.9. Soda ash is added to the first reaction tank. The excess coefficient is ≤1.08. After the reaction endpoint, the residue is filtered and washed, and the filtrate is sent for evaporation and crystallization. The filter residue is zinc-containing slag and can be sold. The filter residue after filtration and washing from the leaching tank and the condensate from evaporation and crystallization are sent to the second reaction tank. The temperature of the second reaction tank is controlled at 75℃, the reaction time is 2.5h, the liquid-solid ratio is 3.5, and dilute sulfuric acid is gradually added to participate in the chemical reaction. The endpoint pH value is controlled at 5.2. At the same time, a second additive is added, with an addition of 0.04%. The main components of the second additive are 30% high carbon fatty alcohol, 22% ethylene oxide polymer, 20% sodium dodecyl sulfate, 15% methyl pentanol, 8% cellulose derivative, and 5% polyacrylamide. Upon reaching the reaction endpoint, the mixture is filtered and washed. The filter residue, being lead-tin slag, is available for sale. The filtrate is sent to a third reaction tank, where the temperature is controlled at 84℃ and the reaction time is 1.5 hours. The pH is adjusted by adding soda ash, with the final pH controlled at 8.9. After precipitation, the mixture is filtered and washed. The filter residue is used as a raw material for copper smelting and is available for sale. The filtrate is sent for evaporation and crystallization to produce sodium chloride and sodium sulfate, which are also available for sale. The chlorine and sulfur removed from the high-chlorine flue dust account for 95.3% and 92.4% of the soluble chlorine and sulfur in the raw materials, respectively. The zinc slag contains 88.43% zinc carbonate, and the copper slag contains 83.23% basic copper carbonate.

[0074] Example 2:

[0075] The present invention uses high-chlorinated copper ash as raw material, which is screened to remove impurities and ground to ≤325 mesh. It is then mixed and stirred evenly with a first additive at a dosage of 0.12%. The main components of the first additive are 40% sodium pyrophosphate, 35% sodium hexametaphosphate, 15% sodium polyacrylate, and 10% polyvinyl alcohol. Water and the mixture are prepared at a liquid-to-solid ratio of 3 and sent to a leaching tank. The temperature at the outlet is controlled at 68°C, and the residence time is controlled at 2.4 hours. After leaching, the mixture is filtered and washed. The filter residue is sent to a second reaction tank, and the filtrate is sent to a first reaction tank. The temperature in the first reaction tank is controlled at 90°C, the reaction time is 2.2 hours, and the pH value is 8.8. Soda ash is added to the first reaction tank. The excess alkali coefficient is ≤1.05. After the reaction endpoint, the solution is filtered and washed, and the filtrate is sent for evaporation and crystallization. The filter residue is zinc-containing slag and can be sold. The filter residue after filtration and washing from the leaching tank and the condensate from evaporation and crystallization are sent to the second reaction tank. The temperature of the second reaction tank is controlled at 82℃, the reaction time is 3 hours, the liquid-to-solid ratio is 4, and dilute sulfuric acid is gradually added to participate in the chemical reaction. The final pH value is controlled at 4.6. At the same time, a second additive is added at a concentration of 0.08%. The main components of the second additive are 40% high carbon fatty alcohol, 25% ethylene oxide polymer, 10% sodium dodecyl sulfate, 18% methyl pentanol, 4% cellulose derivative, and 3% polyacrylamide. Upon reaching the reaction endpoint, the mixture is filtered and washed. The filter residue, being lead-tin slag, is available for sale. The filtrate is sent to a third reaction tank, where the temperature is controlled at 84℃ and the reaction time is 2.5 hours. The pH is adjusted by adding soda ash, reaching a final pH of 8.8. After precipitation, the mixture is filtered and washed. The filter residue is used as a raw material for copper smelting and is available for sale. The filtrate is sent for evaporation and crystallization to produce sodium chloride and sodium sulfate, which are also available for sale. The chlorine and sulfur removed from the high-chlorine flue dust account for 94.64% and 93.26% of the soluble chlorine and sulfur in the raw materials, respectively. The zinc slag contains 89.34% zinc carbonate, and the copper slag contains 84.83% basic copper carbonate.

[0076] Example 3:

[0077] The present invention uses high-chlorinated copper ash as raw material, which is screened to remove impurities and ground to ≤325 mesh. It is then mixed and stirred evenly with a first additive at a dosage of 0.1%. The main components of the first additive are 30% sodium pyrophosphate, 40% sodium hexametaphosphate, 25% sodium polyacrylate, and 5% polyvinyl alcohol. Water and the mixture are prepared at a liquid-to-solid ratio of 4 and sent to a leaching tank. The temperature at the outlet is controlled at 63°C, and the residence time is controlled at 1.8 hours. After leaching, the mixture is filtered and washed. The filter residue is sent to a second reaction tank, and the filtrate is sent to a first reaction tank. The temperature in the first reaction tank is controlled at 86°C, the reaction time is 2 hours, and the pH value is 9.1. Soda ash is added to the first reaction tank. The reaction coefficient is ≤1.06. After the reaction endpoint, the residue is filtered and washed. The filtrate is sent for evaporation and crystallization. The filter residue is zinc-containing slag and can be sold. The filter residue after filtration and washing from the leaching tank and the condensate from evaporation and crystallization are sent to the second reaction tank. The temperature of the second reaction tank is controlled at 80℃, the reaction time is 2.0h, and the liquid-to-solid ratio is 4. Dilute sulfuric acid is gradually added to participate in the chemical reaction, and the final pH value is controlled at 5.5. At the same time, a second additive is added at a concentration of 0.03%. The main components of the second additive are 25% high-carbon fatty alcohol, 30% ethylene oxide polymer, 12% sodium dodecyl sulfate, 20% methyl pentanol, 9% cellulose derivative, and 4% polyacrylamide. After reaching the reaction endpoint, the residue is filtered and washed. The filter residue is lead-tin slag and can be sold. The filtrate is sent to the third reaction tank. The temperature of the third reaction tank is controlled at 90℃, and the reaction time is 2h. The pH value is adjusted by adding soda ash, and the final pH value is controlled at 9.0. After precipitation, the residue is filtered and washed. The filter residue is used as a raw material for copper smelting and can be sold. The filtrate is sent for evaporation and crystallization to produce sodium chloride and sodium sulfate products, which can also be sold. The chlorine and sulfur removed from the high-chlorine flue dust accounted for 91.32% and 92.64% of the soluble chlorine and sulfur in the raw materials, respectively. The zinc carbonate content in the zinc slag reached 89.54%, and the basic copper carbonate content in the copper slag reached 81.47%.

[0078] Comparative Example 1

[0079] The present invention uses high-chlorinated copper ash as raw material, which is screened to remove impurities and ground to ≤325 mesh. It is then mixed and stirred evenly with a first additive at a dosage of 0.1%. The main components of the first additive are 60% sodium pyrophosphate and 40% sodium hexametaphosphate. Water and the mixture are prepared at a liquid-to-solid ratio of 4 and sent to a leaching tank. The temperature at the outlet of the tank is controlled at 64°C, and the residence time is controlled at 1.5 hours. After leaching, the mixture is filtered and washed. The filter residue is sent to a second reaction tank, and the filtrate is sent to a first reaction tank. The temperature in the first reaction tank is controlled at 85°C, the reaction time is 1.8 hours, and the pH value is 9.0. Soda ash is added to the first reaction tank. The auxiliary material, with an excess coefficient of soda ash ≤1.05, is added. After the reaction endpoint, the mixture is filtered and washed. The filtrate is sent for evaporation and crystallization, and the filter residue is zinc-containing slag, which can be sold. The filter residue after filtration and washing from the leaching tank, along with the condensate from evaporation and crystallization, is sent to the second reaction tank. The temperature of the second reaction tank is controlled at 82℃, the reaction time is 1.8 hours, and the liquid-to-solid ratio is 3.8. Dilute sulfuric acid is gradually added to participate in the chemical reaction, controlling the endpoint pH value to 5.5. At the same time, a second additive is added at a concentration of 0.03%, the main components of which are 45% higher carbon fatty alcohols and 55% ethylene oxide polymers. After reaching the reaction endpoint, the mixture is filtered and washed. The filter residue is lead-tin slag, which can be sold. The filtrate is sent to the third reaction tank, with the temperature controlled at 89℃ and the reaction time being 2 hours. The pH value is adjusted by adding soda ash, controlling the endpoint pH value to 9.0. After precipitation, the mixture is filtered and washed. The filter residue is used as a raw material for copper smelting and can be sold. The filtrate is sent to evaporation and crystallization to produce sodium chloride and sodium sulfate products, which can also be sold. The chlorine and sulfur removed from the high-chlorine flue dust accounted for 82.34% and 88.31% of the soluble chlorine and sulfur in the raw materials, respectively. The zinc carbonate content in the zinc slag reached 81.53%, and the basic copper carbonate content in the copper slag reached 76.62%. It is evident that changes in the first and second additives have a significant impact on the effect.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for dechlorination pretreatment of high-chlorinated copper flue dust, characterized in that, Includes the following steps: 1) After copper ash is sieved and ground in sequence, it is mixed and stirred with the first additive, then water is added and leached in a leaching tank, then filtered and washed to obtain the first filtrate and the first filter residue. 2) Add soda ash to the first filtrate obtained in step 1) and react in the first reaction tank with a pH of 7-9.

5. Then filter and wash to obtain zinc slag and second filtrate. Add dilute sulfuric acid and a second additive to the first filter residue obtained in step 1), and react in the second reaction tank, controlling the pH endpoint value range of 4.2-6.

3. Then filter and wash to obtain the third filtrate and lead-tin slag. Add soda ash to the third filtrate, and react in the third reaction tank, controlling the pH endpoint value range of 8.5-9.

1. Then wash and filter to obtain the fourth filtrate and copper-containing slag. 3) Evaporate and crystallize the second filtrate to obtain condensate and a mixed product of sodium chloride and sodium sulfate; The fourth filtrate is evaporated and crystallized to obtain condensate and a mixed product of sodium chloride and sodium sulfate; The first additive is added in a proportion of 0.05-0.15 wt%, and the first additive comprises the following components in weight percentage: sodium pyrophosphate 20-55%, sodium hexametaphosphate 15-45%, sodium polyacrylate 15-35%, and polyvinyl alcohol 5-18%; The addition ratio of the second additive is 0.02-0.1 wt%, and the second additive includes the following components in weight percentage: 20-55% high carbon fatty alcohol, 12-45% ethylene oxide polymer, 10-35% sodium dodecyl sulfate, 10-25% methyl pentanol, 2-10% cellulose derivative, and 3-8% polyacrylamide.

2. The method for dechlorination pretreatment of high-chlorinated copper flue dust according to claim 1, characterized in that: The condensate obtained from the evaporation and crystallization of the second filtrate and / or the condensate obtained from the evaporation and crystallization of the fourth filtrate are recycled to the second reaction tank.

3. The method for dechlorination pretreatment of high-chlorinated copper flue dust according to claim 1, characterized in that: In step 1), grind to ≤325 mesh.

4. The method for dechlorination pretreatment of high-chlorinated copper flue dust according to any one of claims 1 to 3, characterized in that: In step 1), the temperature in the leaching tank is 55-70℃, the residence time is 0.5-2.4h, and the liquid-to-solid ratio is (2.5-5):

1.

5. The method for dechlorination pretreatment of high-chlorinated copper flue dust according to any one of claims 1 to 3, characterized in that: In step 2), the temperature in the first reaction tank is 75-93℃, the reaction time is 1.0-2.5h, and the excess coefficient of added soda ash is 1.05-1.

2.

6. The method for dechlorination pretreatment of high-chlorinated copper flue dust according to any one of claims 1 to 3, characterized in that: In step 2), the temperature in the second reaction tank is 65-85℃, the reaction time is 1.5-3.5h, and dilute sulfuric acid is added gradually, with a liquid-to-solid ratio of (2-5):

1.

7. The method for dechlorination pretreatment of high-chlorinated copper flue dust according to any one of claims 1 to 3, characterized in that: In step 2), the temperature in the third reaction tank is 73-95℃, and the reaction time is 1.0-2.5h, by gradually adding soda ash.

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