Method for recovering copper from copper smelting soot step by step

Abstract

The invention discloses a method for recovering copper from copper smelting soot step by step, which is characterized in that selective extraction and high-grade enrichment of copper phases with different occurrence forms are realized on the premise that an original sales system of associated metals such as lead, bismuth and the like is not obviously interfered by constructing a leaching-reselection cross-coupled multi-stage separation system. According to the method, the difference of physical and chemical characteristics is taken as a separation basis, five steps of first-stage medium acid water leaching, primary filter pressing, shaking table reselection, second-stage strong acid leaching and secondary filter pressing are sequentially executed, and the synergistic effect of gradient dissociation and directional enrichment is formed.

Description

Technical Field

[0001] This invention belongs to the field of metallurgy and resource recycling technology, and specifically relates to a method for stepwise recovery of copper from copper smelting flue dust. Background Technology

[0002] In the copper pyrometallurgical industry, the flue gas generated during the smelting and blowing processes, after being captured by electrostatic precipitators or baghouse dust collectors, forms copper smelting ash with a complex composition. This ash is not only rich in copper but also contains various valuable metals such as lead, zinc, antimony, and bismuth. If it is directly returned to the main smelting system, it will lead to a significant increase in the impurity load of the furnace charge, with volatile components continuously accumulating in the circulation loop, thereby inducing a series of problems such as flue gas duct nodules, system blockages, and environmental pollution. It will also adversely affect the physicochemical properties of the copper anode plates obtained from subsequent pyrometallurgical refining. Therefore, how to efficiently and selectively recover copper resources from copper smelting ash has become a key link in improving the comprehensive utilization efficiency of resources, reducing environmental risks, and ensuring the stable operation of the main process.

[0003] To address these needs, current industrial practices primarily employ two technical approaches: one is direct remelting, which, while simple to operate, fails to resolve the issue of impurity accumulation; the other is dominated by hydrometallurgy, particularly the atmospheric pressure acidic two-stage countercurrent leaching process. This process, by controlling the acidity gradient, preferentially dissolves the easily leached copper sulfate phase in the flue dust and partially extracts the copper oxide phase under enhanced conditions in the second stage, thus achieving partial copper recovery. However, these methods are essentially limited to the single dimension of dissolution-extraction, and are ineffective in treating the insoluble copper phase existing in the form of copper sulfide ferrites. This results in a large amount of copper remaining in the final leaching residue, with the overall copper recovery rate generally remaining between 60% and 70%, leading to significant resource loss. A few studies have attempted to introduce gravity separation processes to enrich copper mineral particles, but traditional gravity separation is usually placed after strong acid leaching or coupled with a high-acid system, which results in the equipment being exposed to a corrosive environment for a long time, with poor stability. Furthermore, strong acid conditions can quickly dissolve a variety of metal components, destroy the differences in surface electrical properties and density of particles, and induce severe mud formation, which greatly weakens the selectivity and separation accuracy of the gravity separation process.

[0004] However, with increasingly stringent clean production standards in copper smelting and ever-increasing demands for the economic viability of resource recovery, the inherent structural contradictions in the principles of the aforementioned existing technologies are becoming increasingly apparent. Specifically, to improve the overall copper recovery rate, it is necessary to enhance the extraction capacity of the sparingly soluble copper oxide phase and even the copper sulfide ferrite phase, which often relies on increasing the acidity of the system. However, a strong acid environment inevitably accelerates the co-dissolution of non-target metals (such as lead and bismuth) and alters the physicochemical properties of solid particles, causing them to lose the density and surface property differences required for gravity separation, thus limiting the application scope of physical enrichment methods. Furthermore, if gravity separation is performed after strong acid leaching, not only does the concentrate grade decrease significantly, but equipment corrosion also intensifies, making long-term stable operation difficult. Conversely, if gravity separation is performed before leaching, the failure to remove easily soluble components leads to particle agglomeration and surface hydration effects, which also interfere with the separation effect. Therefore, existing technologies exhibit an irreconcilable inherent conflict between "chemical leaching depth" and "physical separation efficiency"—strengthening leaching sacrifices the separation basis, while retaining separation conditions restricts leaching efficiency, making synergistic optimization difficult. This fundamental contradiction directly leads to the lack of differentiated recovery pathways for copper phases in different occurrence forms in copper smelting flue dust, making it difficult to obtain high-grade copper concentrate, resulting in high copper content in tailings and limited resource utilization efficiency.

[0005] US Patent Application No. 5032175A discloses a method for removing impurities from copper-containing flue dust. Water is added to the flue dust to produce a slurry containing approximately 10 to 30% by weight of flue dust solids. The slurry is then subjected to gravity separation to obtain a heavy concentrate fraction containing at least 35% by weight of copper and a light tailings fraction containing most of the impurity compounds. Both the heavy concentrate and light tailings fractions undergo solid / liquid separation. The flue dust targeted by this method is typically alkaline, unlike copper smelting flue dust, and the copper in the flue dust is primarily insoluble cuprous oxide. In this case, acid leaching is unnecessary; gravity separation is sufficient to easily separate out the heavier copper phase.

[0006] Chinese invention patent application CN113416849A describes adding copper sulfate solution as a weighting agent to the slurry of copper smelting flue dust to separate copper particles from other components due to their relative gravity. A slurry pump is used to pump the material into a hydrocyclone, where fine, lightweight impurities are pre-separated. The coarser, heavier particles are then separated by a shaking table separation unit, effectively recovering copper from the copper smelting flue dust. However, this method only employs gravity separation and does not address how to effectively recover the copper phase in the liquid. Furthermore, continuously adding copper sulfate as a weighting agent to copper smelting flue dust that already contains copper sulfate can quickly lead to supersaturation and dissolution of the copper sulfate phase in the solution. This dissolved copper sulfate phase has extremely small particle sizes and is usually discharged with the tailings, resulting in copper loss.

[0007] Taking Jinguang Copper Industry Branch, a subsidiary of Tongling Nonferrous Metals Group, as an example, the company produces more than 5,000 tons of copper smelting flue dust annually, including flue dust from the Auschwitz furnace converter and the Auschwitz electric field. Its copper leaching rate is only 60% to 70%, and the copper content in the leaching residue is 5% to 8%. After comprehensively pricing copper, lead, and bismuth, it is sold externally. Although this method can bring short-term benefits, due to the limitations of the processing technology, the copper-based resources in the leaching residue cannot be further effectively recovered.

[0008] Therefore, how to construct a stepwise recovery strategy that can take into account the occurrence characteristics of different copper phases, prioritize the separation of easily soluble components under mild conditions to protect the subsequent physical sorting environment, and then specifically treat the insoluble phase, so as to achieve the dual goals of high recovery rate and high concentrate grade simultaneously without significantly interfering with the sale of associated metals such as lead and bismuth, has become a core technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0009] This invention provides a method for the stepwise recovery of copper from copper smelting flue dust. The method constructs a multi-stage separation system with leaching and gravity separation cross-coupling, achieving selective extraction and high-grade enrichment of copper phases in different occurrence forms without significantly interfering with the existing sales system of associated metals such as lead and bismuth. Based on differences in physicochemical properties, the method sequentially performs five steps: a first-stage medium-acid water leaching, a first-stage pressure filtration, a shaking gravity separation, a second-stage strong acid leaching, and a second-stage pressure filtration, forming a technical path that synergistically combines gradient dissociation and directional enrichment.

[0010] The technical solution adopted in this invention is: a method for stepwise recovery of copper from copper smelting flue dust, comprising the following steps:

[0011] S1: Acidic water leaching stage: Copper smelting ash is added to deionized water and stirred and pulped under normal temperature and pressure conditions. The solid-liquid mass ratio of the slurry is controlled at 1:4 to obtain a water leaching slurry with a pulping concentration of 20-25%. Under these conditions, the natural pH value of the slurry system is maintained between 3 and 4, which promotes the selective dissolution of the easily soluble copper sulfate phase, while the copper sulfide ferrate phase and some copper oxide phase remain in a stable solid state.

[0012] S2: Primary filtration: The water-leached slurry obtained in S1 is subjected to solid-liquid separation using a plate and frame filter press to obtain primary filtrate and primary filter residue; the primary filtrate is rich in free copper ions, and its copper mainly comes from the dissolution products of the original copper sulfate phase in the flue ash, which can be directly introduced into the subsequent extraction process; the primary filter residue contains undissolved copper sulfide ferrite particles, encapsulated copper oxide phase and a small amount of residual copper sulfate phase, and its surface is not corroded by strong acid, retaining the density difference and hydrophobic properties of the original particles;

[0013] S3: Shaking Table Gravity Separation: The primary filter residue obtained in S2 is re-adjusted to a suitable fluidity and fed into a shaking table gravity separation device for separation. Under the combined action of the reciprocating motion of the shaking table surface and the transverse water flow, effective separation is achieved based on the difference in particle density. Among them, the higher density copper sulfide ferrite particles and the copper minerals they encapsulate are enriched at the concentrate end, forming the shaking table concentrate; the lower density siliceous aluminum gangue and fine mud are discharged with the tailings, forming the shaking table tailings. After the shaking table concentrate is dewatered by a ceramic filter, solid material with a moisture content of less than 8% is obtained, which can be directly returned to the main copper smelting process as a high-grade copper raw material. The water obtained from filtration is recycled to step S1, forming an internal water circulation system.

[0014] S4: Second-stage strong acid leaching: The tailings obtained from the shaking table in S3 are placed in an acid-resistant reaction tank, and concentrated sulfuric acid is added to adjust the acidity of the system to 25 g / L. At the same time, the solid-liquid mass ratio of the slurry is controlled at 1:4 to obtain an acid leaching slurry with a slurry concentration of 20-25%. Under this strong acid condition, the pH value of the slurry drops to between 1 and 2, which promotes the protonation and dissolution of the residual copper oxide phase, which is converted into soluble copper ions and enters the liquid phase. The copper sulfide ferrite phase has been preferentially enriched and removed in step S3, so it does not participate in this stage of reaction.

[0015] S5: Secondary Filtration: The acid leaching slurry obtained in S4 is subjected to a second solid-liquid separation using a plate and frame filter press to obtain secondary filtrate and secondary filter residue. The secondary filtrate contains copper ions generated by the dissociation of the copper oxide phase and can be directly incorporated into the extraction system for copper recovery. The secondary filter residue mainly consists of lead and bismuth sulfates and aluminosilicate gangue, with a significantly reduced copper content that meets external sales standards, allowing the existing integrated lead and bismuth sales model to continue.

[0016] Furthermore, the stirring time in step S1 is 30-60 minutes to ensure that the easily soluble components are fully diffused into the liquid phase, while avoiding excessive stirring that could cause particle breakage or mud formation; the operating parameters of the shaking table in step S3 include a stroke range of 12-18 mm, a stroke frequency of 280-320 times / minute, and a feed concentration controlled within the range of 15-20% by mass to ensure the stability of separation efficiency and concentrate grade; the acid leaching reaction time in step S4 is 90-120 minutes to ensure complete dissolution of the copper oxide phase and to prevent significant co-dissolution of lead and bismuth.

[0017] In a preferred embodiment of the present invention, the copper smelting flue dust is derived from the product of the electrostatic precipitator system of a converter or auger furnace, with an original copper grade between 11-12% by mass, a lead grade between 5-27% by mass, and a bismuth grade between 1.7-2.8% by mass. After processing by the method of the present invention, the copper grade of the final shaker concentrate is not less than 49%, and the copper recovery rate is not less than 31%; the copper grade of the second-stage leaching residue is not higher than 3.8%, and the overall copper recovery rate is not less than 85%.

[0018] The primary and secondary filtrates are transported to the copper extraction process separately to avoid cross-contamination of impurities caused by mixing copper solutions from different sources; the shaker concentrate and secondary filter residue are disposed of separately as high-value copper raw materials and lead-bismuth slag, respectively, to maintain the existing resource recovery model.

[0019] The method described in this invention effectively removes the easily soluble copper sulfate phase by pre-leaching with medium-acid water, eliminating its interference with the subsequent gravity separation process. Simultaneously, it preserves the original physical properties of the primary filter residue particles, providing a good foundation for gravity separation. Then, shaking table gravity separation precisely captures the insoluble but high-density copper sulfide ferrite phase, achieving high-grade copper enrichment. Finally, strong acid leaching is applied to the gravity separation tailings to specifically extract the residual copper oxide phase, thus completing the stepwise and differentiated recovery of the three main copper occurrence forms. This process route completely avoids the problems of particle mud formation, equipment corrosion, and co-dissolution of non-target metals caused by traditional strong acid leaching. It also overcomes the defect of separation failure caused by strong acid pretreatment after gravity separation, fundamentally solving the structural contradiction between "chemical leaching depth" and "physical separation efficiency."

[0020] The reaction vessels used in steps S1 and S4 are mechanically stirred tanks lined with acid-resistant rubber or polypropylene to ensure structural integrity during long-term operation. The filter press uses reinforced polypropylene plates and frames, and the sealing surfaces are coated with fluororubber to adapt to medium to strong acid conditions. The shaking table is made of high-molecular composite wear-resistant material, with a specific groove structure on the surface to optimize the stratification effect, and is equipped with an automatic ore discharge device to maintain the stability of continuous operation.

[0021] The method of this invention is applicable to all resource utilization scenarios of copper-containing smelting flue dust, especially suitable for industrial sites with high lead and bismuth content that need to maintain their independent pricing system. Its core technology lies in the reconstruction of process sequence and precise matching of operating conditions, rather than the performance improvement of a single unit operation. Therefore, it has significant system integration advantages and engineering feasibility. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the present invention. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings.

[0024] A method for stepwise recovery of copper from copper smelting flue dust is disclosed. The technical solution utilizes a multi-stage separation system with leaching and gravity separation cross-coupling. This system achieves selective extraction and high-grade enrichment of copper phases in different occurrence forms without significantly interfering with the existing sales system of associated metals such as lead and bismuth. The method uses differences in physicochemical properties as the basis for separation, sequentially executing five defined steps: a first-stage medium-acid water leaching, a first-stage pressure filtration, a shaking gravity separation, a second-stage strong acid leaching, and a second-stage pressure filtration. This forms a technical path that synergistically combines gradient dissociation and directional enrichment.

[0025] In the specific implementation process, the first step is the S1 stage: a medium-acid water leaching operation. Copper smelting flue dust from the converter or Auerbach furnace electrostatic precipitator system is added to deionized water and stirred and slurried under normal temperature and pressure conditions. The solid-liquid mass ratio of the slurry is controlled at 1:4, maintaining the slurry concentration within the range of 20% to 25% by mass. Under these conditions, the natural pH value of the slurry system is stable between 3 and 4, promoting the selective dissolution of the readily soluble copper sulfate phase in the flue dust into the liquid phase, while the copper sulfide ferrate phase and some copper oxide phase, due to their high thermodynamic stability, remain in a solid state without significant dissolution. The stirring time is controlled between 30 and 60 minutes to ensure that the readily soluble components fully diffuse into the liquid phase, while avoiding excessive stirring that could cause particle breakage or mud formation, thus preserving the original physical morphology of the particles required for subsequent gravity separation.

[0026] The subsequent step is S2: primary filter press operation. The water-leached slurry obtained in S1 is introduced into a plate and frame filter press for solid-liquid separation. The filter press used is a reinforced polypropylene plate and frame filter with fluororubber coating on the sealing surfaces to meet the long-term operating requirements under medium-acid conditions. After filtration, primary filtrate and primary filter residue are obtained. The primary filtrate is rich in free copper ions, mainly derived from the dissolution products of the primary copper sulfate phase in the flue dust, and can be directly transported to the copper extraction process for further purification. The primary filter residue contains undissolved copper sulfide ferrite particles, encapsulated copper oxide phase, and a small amount of residual copper sulfate phase. Because this filter residue has not been eroded by strong acid, its surface physical properties are fully preserved, including particle density differences and hydrophobicity, providing a good material basis for subsequent gravity separation operations.

[0027] Next, S3: shaking table gravity separation operation is performed. The primary filter residue obtained in S2 is re-slurryed, and deionized water is used to adjust it to a suitable fluidity, with the feed concentration controlled within the range of 15% to 20% by mass. This slurry is then fed into the shaking table gravity separation equipment for separation. The shaking table surface is made of a high-polymer composite wear-resistant material, with a specific groove structure to optimize particle stratification, and is equipped with an automatic discharge device to maintain continuous operation stability. The operating parameters of the shaking table are set to a stroke range of 12 mm to 18 mm and a stroke frequency of 280 to 320 times per minute. Under the combined action of the reciprocating motion of the shaking table surface and the transverse water flow, effective separation is achieved based on the difference in particle density. Among them, the higher density copper sulfide ferrite particles and the copper minerals they encapsulate settle faster and are enriched at the concentrate end, forming the shaking table concentrate; the lower density silicate gangue and fine mud are discharged with the tailings, forming the shaking table tailings. After dewatering by a ceramic filter, the shaker concentrate yields a solid material with a moisture content of less than 8%, which can be directly returned to the main copper smelting process as a high-grade copper raw material. The filtered water is recycled to step S1, forming an internal water circulation system and reducing fresh water consumption.

[0028] The subsequent S4 stage involves a two-stage strong acid leaching operation. The tailings from the shaking table obtained in S3 are placed in an acid-resistant reaction tank lined with acid-resistant rubber or polypropylene, providing excellent corrosion resistance. Concentrated sulfuric acid is added to the tank to adjust the system acidity to 25 g / L, while maintaining the slurry solid-liquid mass ratio at 1:4, keeping the slurry concentration between 20% and 25% by mass. Under these strong acid conditions, the slurry pH drops to between 1 and 2, promoting the protonation reaction of the residual copper oxide phase, converting it into soluble copper ions that enter the liquid phase. Since the copper sulfide ferrite phase has already been preferentially enriched and removed in step S3, it does not participate in this stage of the reaction, thus avoiding the release of hydrogen sulfide or metal co-dissolution problems that may be caused by sulfide decomposition under strong acid conditions. The acid leaching reaction time is controlled between 90 and 120 minutes to ensure complete dissolution of the copper oxide phase, while inhibiting significant co-dissolution of associated metals such as lead and bismuth, ensuring that they remain in the slag in solid form.

[0029] Finally, the S5 operation is performed: secondary filtration. The acid-leached slurry obtained in S4 is introduced into another plate and frame filter press for a second solid-liquid separation. This filter press also uses reinforced polypropylene plates and frames and fluororubber sealing structures to adapt to strong acid conditions. After filtration, secondary filtrate and secondary filter residue are obtained. The secondary filtrate contains copper ions generated from the dissociation of the copper oxide phase, and its impurity content is low. It can be directly incorporated into the copper extraction system for copper recovery without additional purification steps. The secondary filter residue mainly consists of lead and bismuth sulfates and aluminosilicate gangue. Its copper content is significantly reduced, and after testing, it meets the standards for external sale. The original lead and bismuth sales model can continue, without affecting the existing resource recovery economic model.

[0030] Throughout the process, primary and secondary filtrates are transported independently to the copper extraction process to avoid cross-contamination caused by mixing copper solutions from different sources. Shaking table concentrate and secondary filter residue are also disposed of independently as high-value copper raw materials and lead-bismuth slag, respectively, ensuring clear product flow and controllable quality. All reaction vessels, filter presses, and gravity separators are material-adapted to their respective operating conditions to ensure long-term stable system operation.

[0031] Furthermore, the reaction vessels used in steps S1 and S4 are all mechanically stirred tanks lined with acid-resistant rubber or polypropylene, and the stirring blades are made of titanium alloy or Hastelloy to resist corrosion from acidic media. The filter cloth of the filter press is made of polyester monofilament fabric with a pore size of 20 micrometers, balancing filtration efficiency and cake removal performance. The feed pump for the shaking table is a diaphragm metering pump, with flow rate accuracy controlled within ±2% to ensure stable feed concentration. The entire system is equipped with an online pH monitor and an automatic acidity replenishment device to achieve closed-loop control of process parameters.

[0032] Example 1 uses copper smelting flue dust collected by the converter electrostatic precipitator system of Anhui Jinguan Copper Industry Co., Ltd. as raw material. The original copper grade of the flue dust is 11.5%, the lead grade is 22.3%, and the bismuth grade is 2.1%. It is processed according to the above method. The results are shown in Table 1.

[0033] Table 1. Copper recovery results in Example 1

[0034]

[0035] The results show that by combining leaching and gravity separation processes, a copper concentrate with a copper grade of up to 53.93% can be obtained, and the copper recovery rate of gravity separation can reach 40.10%. The copper grade of the second-stage leaching residue is only 1.61%, which is very effective.

[0036] Furthermore, considering the impact of this process on the normal on-site pricing and sales of lead and bismuth, lead and bismuth analyses were performed on the products at each stage, and the results are shown in Table 2.

[0037] Table 2. Results of lead and bismuth recovery in Example 1

[0038]

[0039] The results showed that lead and bismuth were still mostly present in the leaching residue, and the shaking table gravity separation had minimal impact on the sale of lead and bismuth from the leaching residue in the original leaching process.

[0040] Comparative Example 1: The existing process is a two-stage leaching countercurrent process. During the first stage of leaching, the pH value drops to 1.5~2.5. The copper recovery results are shown in Table 3.

[0041] Table 3 Copper recovery results of Comparative Example 1

[0042]

[0043] The results showed that the copper leaching rate was 62.58% using the traditional two-stage countercurrent leaching process, and the copper grade of the two-stage leaching residue was as high as 7.50%.

[0044] Comparative Example 2: The reselection operation location in Example 1 was changed to the rear end of the two-stage leaching operation, while the rest of the process remained unchanged. The experimental results are shown in Table 4.

[0045] Table 4. Copper recovery results of Comparative Example 2

[0046]

[0047] The results showed that changing the gravity separation operation to the end of the two-stage leaching operation increased the leaching rate of the two-stage leaching, but the copper grade of the gravity separation concentrate obtained after subsequent gravity separation decreased significantly, to only 24.67%, and the copper content of the final tailings was significantly higher than that in Example 1. Moreover, after long-term use, obvious erosion was visible on the bed surface.

[0048] Example 2 uses flue dust from the electric arc furnace of the copper smelting plant of Anhui Huijinlong Copper Industry Co., Ltd. as raw material. The raw flue dust ore contains 11.40% copper, 5.52% lead, and 1.71% bismuth. The results are shown in Table 5.

[0049] Table 5. Copper recovery results in Example 2

[0050]

[0051] The results show that by combining leaching and gravity separation processes, a copper concentrate with a copper grade of up to 49.88% can be obtained, and the copper recovery rate of gravity separation can reach 31.72%. The copper grade of the second-stage leaching residue is only 3.74%, which is very effective.

[0052] Considering the impact of this process on the normal on-site pricing and sales of lead and bismuth, lead and bismuth analyses were performed on the products at each stage, and the results are shown in Table 6.

[0053] Table 6. Results of lead and bismuth recovery in Example 2

[0054]

[0055] The results showed that lead and bismuth were still mostly present in the leaching residue, and the shaking table gravity separation had minimal impact on the sale of lead and bismuth from the leaching residue in the original leaching process.

[0056] Comparative Example 3: The existing process is a two-stage leaching countercurrent process. During the first stage of leaching, the pH value drops to 1.0~2.0. The copper recovery results are shown in Table 7.

[0057] Table 7 Copper recovery results of Comparative Example 1

[0058]

[0059] The results showed that the copper leaching rate was 60.05% using the traditional two-stage countercurrent leaching process, and the copper grade of the two-stage leaching residue was as high as 7.30%.

[0060] Comparative Example 4: One stage of the leaching process in Example 2 was replaced with strong acid leaching, with a pH value of 1.0~2.0, and the rest of the process remained unchanged. The experimental results are shown in Table 8.

[0061] Table 8 Copper recovery results of Comparative Example 2

[0062]

[0063] The results showed that changing the first-stage leaching operation to strong acid leaching increased the leaching rate of the first-stage leaching, but the copper grade of the gravity concentrate obtained after subsequent gravity separation decreased significantly, to only 11.37%, and the copper content of the final tailings was significantly higher than that in Example 2. Moreover, after long-term use, obvious erosion was visible on the bed surface.

[0064] In contrast, this invention achieves efficient graded recovery of copper by reconstructing the process sequence and precisely matching conditions, while ensuring that lead and bismuth are not lost.

[0065] Regarding material balance, taking the treatment of 1000 kg of flue ash as an example: In step S1, approximately 2.1 kg of copper (corresponding to the copper sulfate phase) is dissolved and enters the primary filtrate; the primary filter residue contains 98 kg of copper; after shaking table gravity separation, the shaking table concentrate yields approximately 220 kg, containing 112.6 kg of copper (grade 51.2%), with a copper recovery of 32.5%; the shaking table tailings are approximately 780 kg, containing 32 kg of copper (grade 4.1%); after strong acid leaching in step S4, approximately 28.5 kg of copper is dissolved and enters the secondary filtrate, with the secondary filter residue containing 3.5 kg of copper (grade 3.5%). The total recovered copper is 2.1 + 112.6 × (32.5 / 100) + 28.5 ≈ 97.8 kg, with a recovery rate of 86.7%, consistent with the measured data.

[0066] This invention is applicable to all resource recovery scenarios for copper-containing smelting ash, especially suitable for industrial sites with high lead and bismuth content. Its core technology lies in the restructuring of the process sequence: first, medium-acid water leaching removes the easily soluble copper phase to protect the characteristics of the gravity separation material; then, gravity separation enriches the high-density, insoluble copper phase; finally, strong acid leaching is applied to the tailings to remove residual copper oxide. These three steps form a logically rigorous progressive relationship. This approach completely avoids the problems of particle mud formation, accelerated equipment corrosion, and co-dissolution of non-target metals caused by traditional strong acid leaching. It also overcomes the defect of separation failure caused by strong acid pretreatment after gravity separation, fundamentally resolving the structural contradiction between "chemical leaching depth" and "physical separation efficiency."

[0067] All operations can be completed at ambient temperature and pressure, requiring no additional heating or pressurization equipment, significantly reducing energy consumption. The water circulation system design further reduces wastewater discharge, meeting clean production requirements. The process flow is highly modular, easily integrated with existing smelter infrastructure, and possesses good engineering feasibility and economic viability.

[0068] Those skilled in the art should understand that the protection scheme of the present invention is not limited to the above embodiments, and various arrangements, combinations and transformations can be made on the basis of the above embodiments. Without departing from the spirit of the present invention, all transformations made to the present invention fall within the protection scope of the present invention.

Claims

1. A method for stepwise recovery of copper from copper smelter dust, characterized in that, The method comprises the following steps: S1: one-stage acid water leaching: copper smelting ash is added into deionized water, and is stirred and slurried under normal temperature and pressure, and the solid-liquid mass ratio of the slurry is controlled to be 1:4, so that a water leaching slurry with a slurry concentration of 20-25% is obtained; under this condition, the natural pH value of the slurry system is maintained between 3-4, so as to promote selective dissolution of the easily soluble copper sulfate phase, and the copper sulfide ferrite phase and part of the oxidized copper phase remain in a stable solid state; S2: first-stage pressure filtration: the water leaching slurry obtained in S1 is subjected to solid-liquid separation through a plate-and-frame filter press, so that a first-stage filtrate and a first-stage filter residue are obtained; the first-stage filtrate is rich in free copper ions, and the copper mainly comes from the dissolution product of the primary copper sulfate phase in the ash; the first-stage filter residue contains undissolved copper sulfide ferrite particles, wrapped oxidized copper phase and a small amount of residual copper sulfate phase; S3: table reselection: the first-stage filter residue obtained in S2 is re-slurried to a slurry state with appropriate fluidity, and is sent to a table reselection device for separation operation; under the combined action of reciprocating motion of the table bed and transverse water flow, effective separation is realized based on the density difference of the particles; wherein, the copper sulfide ferrite particles and the copper minerals wrapped therein with higher density are enriched in a concentrate end to form a table concentrate; the siliceous and aluminous gangue and fine mud with lower density are discharged with tail flow to form a table tailing; the table concentrate is dehydrated to obtain a solid material with a water content of less than 8%; S4: second-stage strong acid leaching: the table tailing obtained in S3 is placed in an acid-resistant reaction tank, concentrated sulfuric acid is added to adjust the acidity of the system to 25 g / L, and the solid-liquid mass ratio of the slurry is controlled to be 1:4, so that a acid leaching slurry with a slurry concentration of 20-25% is obtained; under this strong acid condition, the pH value of the slurry is reduced to 1-2, so as to promote protonation and dissolution of the residual oxidized copper phase to convert into soluble copper ions into the liquid phase; S5: second-stage pressure filtration: the acid leaching slurry obtained in S4 is subjected to second-stage solid-liquid separation through a plate-and-frame filter press, so that a second-stage filtrate and a second-stage filter residue are obtained; the second-stage filtrate contains copper ions produced by dissociation of the oxidized copper phase; the main components of the second-stage filter residue are lead, bismuth sulfates and silicate gangue.

2. The process for the stepwise recovery of copper from copper smelter dust according to claim 1, characterized in that, The stirring time in the S1 step is 30-60 minutes; the operation parameters of the table in the S3 step include a stroke range of 12-18 mm, a stroke frequency of 280-320 times / min, and a feed concentration controlled in the range of 15-20% by mass fraction; the acid leaching reaction time in the S4 step is 90-120 minutes.

3. The process for the stepwise recovery of copper from copper smelter dust according to claim 1, characterized in that, In the S3 step, the table concentrate is dehydrated through a ceramic filter; the water obtained by dehydration and filtration is used for the S1 step to form an internal water circulation system.

4. The process for the stepwise recovery of copper from copper smelter dust according to claim 1, characterized in that, The reaction vessels used in the S1 and S4 steps are mechanical stirring tanks lined with acid-resistant rubber or polypropylene material; the filter press equipment used in the S2 and S5 steps adopts a reinforced polypropylene plate frame, and the sealing surface is coated with fluororubber; the bed surface of the table used in the S3 step is made of high-molecular composite wear-resistant material, and is provided with a specific groove structure and is equipped with an automatic ore discharge device.

5. The process for the stepwise recovery of copper from copper smelter dust according to claim 1, characterized in that, The primary filtrate and the secondary filtrate are independently delivered to a copper extraction process; the shaking table concentrate is returned to a copper smelting main process as a high-grade copper raw material; and the secondary filtration residue is sold as a lead and bismuth valuation residue.

6. The process for the stepwise recovery of copper from copper smelter dust according to claim 1, characterized in that, The copper smelting ash is derived from a converter or an electric precipitator system of an oxygen converter, and has an original copper grade of 11%-12% by mass, a lead grade of 5%-27% by mass, and a bismuth grade of 1.7%-2.8% by mass.

7. The process for the stepwise recovery of copper from copper smelter dust according to claim 1, characterized in that, After the method, the shaking table concentrate has a copper grade of not less than 49% and a copper recovery rate of not less than 31%; and the secondary filtration residue has a copper grade of not more than 3.8% and a comprehensive copper recovery rate of not less than 85%.

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