Separation and recovery method of scrapped crystalline silicon photovoltaic module

Abstract

The invention relates to a method for separating and recycling a scrapped crystalline silicon photovoltaic module, and relates to the technical field of treatment of the scrapped crystalline silicon photovoltaic module. The method comprises the following steps: preprocessing a photovoltaic module, and removing a frame, a back plate and a packaging layer to obtain a mixed solid; crushing the mixed solid and grading according to the particle size; by adopting a magnetic fluid density separation technology, standing and layering the particles with different particle sizes under the condition of controlling magnetic field intensity and temperature to form fractions containing different components such as silver, copper, tin, zinc, silicon and the like; the components are respectively recovered through layered extraction; and high-purity metal is further extracted through directional wet leaching, and residue materials are recycled after being dried. According to the method, efficient separation and resource utilization of multiple components are achieved through the synergistic effect of magnetic density separation and wet recovery, and the method has the advantages of being high in separation efficiency, low in energy consumption, simple in process, environmentally friendly and the like and is suitable for large-scale green recovery application of the retired photovoltaic modules.

Description

Technical Field

[0001] The present invention relates to the technical field of processing scrapped crystalline silicon photovoltaic modules, and in particular to a separation and recovery method of scrapped crystalline silicon photovoltaic modules. Background Art

[0002] With the accelerating pace of green energy transformation, solar energy, as a sustainable, pollution-free clean energy, has seen my country's total photovoltaic installed capacity and annual power generation continue to rise in recent years, firmly maintaining its leading position in the world. However, as a large number of photovoltaic power stations invested in early construction gradually approach their designed service life (about 20 to 30 years), the retirement tide of photovoltaic modules has begun to emerge, and is expected to show an accelerating growth trend in the next few decades.

[0003] Retired photovoltaic modules contain a large number of recyclable resources, such as high-purity glass, metal frames, cells, EVA packaging films, connectors and backplane materials, especially high-value metals such as silver, copper, tin, indium and tellurium. The effective recycling of these resources is not only of great environmental significance, but also has significant economic potential. According to the International Energy Agency, by 2050, the global photovoltaic module recycling market is expected to be worth more than US$15 billion, showing a huge prospect for the utilization of renewable resources.

[0004] At present, the treatment methods for retired photovoltaic modules are still mainly simple landfill and primary mechanical disassembly. Although these traditional treatment methods have low operating costs, they have problems such as low separation efficiency, rough material classification, and serious waste of resources. In contrast, although the use of thermal or chemical treatment methods can achieve the recovery of metals or silicon wafers with higher purity, these methods generally have the defects of high process energy consumption, high pollutant emissions, and poor environmental friendliness, which limits their practical application in the treatment of large-scale retired modules.

[0005] Therefore, it is urgent to develop a new method for recycling photovoltaic modules that takes into account environmental performance, separation efficiency and economic feasibility in the existing technology, so as to realize the transformation of retired photovoltaic modules from "harmless disposal" to "resource-based high-value recycling". In particular, how to achieve efficient separation and recycling of multiple high-value components such as silver, copper, tin, zinc and silicon under the premise of controlling energy consumption and environmental impact has become a key technical problem that needs to be solved in the field of resource utilization in the current photovoltaic industry. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a separation and recovery method for scrapped crystalline silicon photovoltaic modules to solve the problems existing in the prior art such as extensive treatment methods, low resource recovery rate, high energy consumption, and high environmental pollution risk, thereby realizing efficient, low-energy consumption, and environmentally friendly resource recovery of retired photovoltaic modules.

[0007] To overcome the defects of the above prior art, the present invention provides a method for separating and recycling waste crystalline silicon photovoltaic modules, comprising the following steps: S1: Pretreatment: Disassemble the waste crystalline silicon photovoltaic module to be separated and recycled, remove the aluminum alloy frame, backsheet and EVA encapsulation layer to obtain a mixed solid mainly composed of glass, silicon wafers and electrode materials; S2: Crushing and classification: Crush the mixed solid obtained in step S1 to obtain particles with a particle size of 100 μm to 5 mm, and divide the particles into three particle size grades according to the particle size; S3: Magnetic density separation: Perform magnetic density separation on the three particle size grades of particles obtained in step S2 respectively. The magnetic density separation includes the following steps: Put the particles into a magnetic fluid separation device. The magnetic fluid is an aqueous suspension containing Fe3O4 nanoparticles. By adjusting the magnetic field strength, a vertical density gradient is formed in the aqueous suspension, and after standing and stratifying, a light fraction, a middle fraction and a heavy fraction are separated; S4: Stratified extraction: Extract the light fraction, middle fraction and heavy fraction obtained in step S3 layer by layer, and recover the magnetic fluid after cleaning; S5: Metal recovery: Perform metal recovery treatment on the middle fraction and heavy fraction obtained in step S4 to obtain metals and inert residues; S6: Dry and recycle the inert residue of the light fraction to complete the separation and recycling.

[0008] Compared with the prior art, the separation and recovery method of waste crystalline silicon photovoltaic modules in this application has the following advantages: The method of the present invention uses magnetic density separation to replace the traditional extensive mechanical sorting or high-temperature melting process. By utilizing the controllable density gradient inside the magnetic fluid and combining with the density difference of the particles themselves, it realizes the efficient and gentle separation of different components (such as glass, silicon, silver, copper, tin, zinc, etc.) of the photovoltaic module, effectively improving the purity and recovery efficiency of resource separation. The present invention further classifies the crushed particles and optimizes the separation conditions for different particle sizes respectively, forming a synergistic mechanism of particle size classification + magnetic density separation, effectively improving the overall separation accuracy and reducing the component cross-contamination, thereby enhancing the selectivity and efficiency of subsequent metal extraction. Secondly, in step S3, the particles of the three particle size grades can be subjected to magnetic density separation separately in batches or mixed together for magnetic density separation. By implementing targeted wet leaching on the middle fraction and heavy fraction subsequently and combining electrolysis or precipitation methods to purify the metal, high-purity metal resources such as silver, copper, tin, zinc, etc. can be recovered respectively, and the overall metal recovery rate exceeds 90%, which is significantly better than the traditional thermal or dry recovery technology. And the entire process flow of the present invention is carried out under mild conditions (low-temperature magnetic field, low-acidity wet method), with significantly reduced energy consumption, low environmental pollution risk, and the magnetic fluid can be recycled, and the inert residue can also be recycled, basically achieving nearly zero waste treatment, taking into account both economy and environmental friendliness. In summary, through the synergistic effect of physical separation and chemical recovery, the present invention breaks through the bottleneck of the traditional method in terms of technical principle, realizes both efficient component separation and high-value resource recovery, and fully solves the key technical problems such as low recovery efficiency, large environmental pollution, and poor economy mentioned in the background technology, and has great industrial promotion prospects.

[0009] In a possible implementation manner, in step S2, the three particle size grades are 100 - 500 μm, 500 μm - 3 mm, and 3 mm - 5 mm in sequence.

[0010] Compared with the prior art, adopting the above technical solution can accurately classify the mixed particles after crushing according to the particle size range, set the optimal magnetic density separation conditions according to the physical properties (settling velocity, surface area, density difference) of the particles with different particle sizes, thereby improving the selectivity and accuracy of the separation process, further reducing the component cross-contamination between the fractions, increasing the enrichment degree of each target component at its respective level, and improving the efficiency.

[0011] In a possible implementation manner, in step S3, in the water-based suspension, the effective density range of the magnetic fluid is 1.5 - 3.8 g / cm 3 。

[0012] Compared with the prior art, adopting the above technical solution can form a density gradient field within a controllable range by regulating the effective density of the magnetic fluid, enabling component particles with different densities to naturally stratify in the fluid according to density differences, thereby achieving precise and gentle multi-component separation. By controlling the effective density range of the magnetic fluid to be 1.5 - 3.8 g / cm 3 , further improving the separation purity and distinctness, avoiding the mixing of different substances, and reducing the separation error.

[0013] In a possible implementation manner, in the step S3, the conditions for regulating the magnetic field intensity are: controlling the magnetic field intensity to be 0.3 - 0.7 Tesla; the temperature of the water-based suspension is 20 - 30 °C.

[0014] Compared with the prior art, adopting the above technical solution, by reasonably controlling the magnetic field intensity to be 0.3 - 0.7 Tesla and the temperature of the magnetic fluid to be 20 - 30 °C, the density gradient distribution inside the magnetic fluid is precisely adjusted, ensuring the stable and efficient separation process. The magnetic field intensity affects the arrangement state and local magnetic density of Fe3O4 nanoparticles, thereby controlling the effective density gradient of the magnetic fluid; while temperature regulation can avoid excessive changes in fluid viscosity, ensuring the density balance stability during the movement of particles, forming a stable, controllable, and continuous density stratification environment, preventing the stratification from being blurred or particles from being mixed due to fluid instability, ultimately improving the clarity and precision of fraction separation, ensuring the efficient directional enrichment of metals, silicon, and glass, and at the same time reducing energy consumption and system disturbance.

[0015] In a possible implementation manner, in the step S3, the light fraction contains glass and silicon-containing compounds; the middle fraction contains tin compounds, zinc compounds, and silicon materials; the heavy fraction contains copper-based materials and silver-based materials.

[0016] Compared with the prior art, adopting the above technical method, through magnetic density separation, different material components in the photovoltaic module are effectively stratified according to density differences, directly realizing the preliminary physical separation of valuable resources such as glass, silicon, and metal; in the present invention, different materials (including glass / SiO2, tin / zinc / silicon, copper / silver) have significant density differences. Through the floating and sinking behaviors of particles in a vertical density gradient environment, a stratified structure can be naturally formed, efficiently separating complex mixed solid materials into different enrichment areas quickly and without chemical erosion, reducing component cross-contamination and loss in subsequent processing steps.

[0017] In a possible implementation manner, in the step S4, the conditions for layer-by-layer extraction are: extracting each fraction of particles layer by layer from top to bottom in sequence through an adjustable-height siphon or a mechanical lifting sieve.

[0018] Compared with the prior art, by adopting the above technical solution, through the adjustment of the height of the siphon or the control of the lifting of the sieve, it is possible to extract the particles within a specific density range layer by layer according to the spatial distribution of the particle sedimentation layer, thereby maintaining the stability of the separation interface of each layer. The purity of the particle components of each fraction extracted is higher, the separation accuracy is greatly improved, and the impurity interference caused by cross-contamination in the subsequent metal recovery and silicon purification steps is reduced.

[0019] In a possible implementation manner, in the step S5, the conditions for the metal recovery treatment are as follows: the light fraction, the middle fraction, and the heavy fraction are subjected to leaching treatment to obtain a leachate, and then the recovery is completed through electrolysis or chemical precipitation.

[0020] Compared with the prior art, by adopting the above technical solution, it is possible to target the metal components enriched in different fractions, and adopt wet chemical leaching combined with electrochemical or chemical precipitation means to extract the required metal resources directionally. The above technical solution dissolves specific metal components with a selective leaching agent, and then combines electrolytic deposition or chemical reduction precipitation means to achieve the purification of metal elements from a complex mixed system.

[0021] In a possible implementation manner, in the step S5, the metal recovery treatment includes the following steps: S5a. Heavy fraction metal recovery: Extract silver and copper from the heavy fraction particles: Leaching of silver: Use a mixed solution of hydrochloric acid and citric acid, and leach at 50 - 80 °C for 1 - 2 hours; Leaching of copper: Use a mixed solution of dilute sulfuric acid and hydrogen peroxide, and leach at 30 - 70 °C for 1 - 2 hours; S5b: Middle fraction metal recovery: Extract tin, zinc, and silicon from the middle fraction particles: Leaching of tin and zinc: Use an acetic acid or oxalic acid buffer solution with a pH value of 4 - 6, and leach at 40 - 60 °C for 1 - 2 hours; Purification of silicon: Etch the surface oxide layer of the leached silicon particles with 5% - 10% hydrofluoric acid, wash with deionized water, and dry.

[0022] Compared with the prior art, by adopting the above technical solution, according to the chemical characteristics of the enriched elements in different fractions, targeted wet leaching systems are respectively selected for metal extraction and silicon purification. In the present invention, metals such as silver, copper, tin, and zinc have different chemical reaction activities and dissolution behaviors. Further, by selecting leaching systems with different pH values, ligand types or redox environments, efficient selective dissolution of target elements can be achieved. Finally, the extraction rate of metals reaches more than 90%. At the same time, the silicon particles are not significantly corroded during the leaching process. Subsequently, the silicon powder can be further purified by etching, enabling the efficient recovery and reuse of valuable metal resources and the high-purity extraction of silicon resources, greatly improving the economic benefits and resource utilization rate of the overall recovery process.

[0023] In a possible implementation manner, in step S6, the conditions for drying and recycling the inert residue are as follows: the inert residue is washed, dried, and briquetted to form a standard test block, and the recycling is completed.

[0024] Compared with the prior art, by adopting the above technical solution, the inert residues such as glass powder and SiO2 particles generated during the separation and recovery process are recycled, avoiding direct landfill or disposal in traditional treatment methods. The above technical solution removes the residual magnetic fluid and chemical reagents by washing the residue particles, then undergoes drying and stabilization treatment, and finally is briquetted to form a regenerated material with good density and moderate mechanical strength. Moreover, standard test blocks that can be used for non-structural building materials (such as road base materials and thermal insulation fillers) are prepared, realizing the resource recycling of waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flowchart of the separation and recovery method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] First of all, those skilled in the art should understand that these embodiments are only used to explain the technical principles of the embodiments of the present application and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments according to needs to adapt to specific application scenarios.

[0027] The present invention provides a separation and recovery method for waste crystalline silicon photovoltaic modules, as Figure 1 shown, Figure 1 It is a flowchart of the separation and recovery method of the present invention, specifically including the following steps: S1: Pretreatment: The waste crystalline silicon photovoltaic module to be separated and recovered is disassembled to remove the aluminum alloy frame, backsheet, and EVA encapsulation layer, obtaining a mixed solid mainly composed of glass, silicon wafers, and electrode materials; S2: Crushing and classification: Crush the mixed solid obtained in the step S1 to obtain particles with a particle size of 100 μm to 5 mm, and classify the particles into three particle size grades according to the particle size; S3: Magnetic density separation: Perform magnetic density separation on the three particle size grades of particles obtained in the step S2 respectively. The magnetic density separation includes the following steps: Put the particles into a magnetic fluid separation device. The magnetic fluid is an aqueous suspension containing Fe3O4 nanoparticles. By adjusting the magnetic field strength, a vertical density gradient is formed in the aqueous suspension, and after standing and layering, a light fraction, a middle fraction, and a heavy fraction are separated; S4: Layered extraction: Extract the light fraction, the middle fraction, and the heavy fraction of the step S3 layer by layer, and recover the magnetic fluid after cleaning; S5: Metal recovery: Perform metal recovery treatment on the middle fraction and the heavy fraction obtained in the step S4 to obtain metals and inert residues; S6: Dry and recover the inert residues of the light fraction to complete the separation and recovery.

[0028] As a preferred solution, in the step S2, the three particle size grades are 100 - 500 μm, 500 μm - 3 mm, and 3 mm - 5 mm in sequence.

[0029] As a preferred solution, in the step S3, in the aqueous suspension, the effective density range of the magnetic fluid is 1.5 - 3.8 g / cm 3 .

[0030] As a preferred solution, in the step S3, the conditions for adjusting the magnetic field strength are: control the magnetic field strength to be 0.3 - 0.7 Tesla; the temperature of the aqueous suspension is 20 - 30 °C.

[0031] As a preferred solution, in the step S3, the light fraction contains glass and silicon-containing compounds; the middle fraction contains tin compounds, zinc compounds, and silicon materials; the heavy fraction contains copper-based materials and silver-based materials.

[0032] In the present invention and the following embodiments, the tin compounds include but are not limited to tin oxide (SnO2), metallic tin, and its alloys; the zinc compounds include but are not limited to zinc oxide (ZnO), metallic zinc, and its alloys; the silicon-containing compounds include elemental silicon, silicon dioxide, or a mixture thereof.

[0033] As a preferred solution, in the step S4, the conditions for layer-by-layer extraction are: extract each fraction of particles layer by layer from top to bottom in sequence through a siphon with adjustable height or a mechanically lifted sieve.

[0034] As a preferred solution, in step S5, the conditions for the metal recovery treatment are as follows: the light fraction, middle fraction, and heavy fraction are subjected to leaching treatment to obtain a leaching solution, and then the recovery is completed through electrolysis or chemical precipitation.

[0035] As a preferred solution, in step S5, the metal recovery treatment includes the following steps: S5a. Heavy fraction metal recovery: Extract silver and copper from the heavy fraction particles: Leaching of silver: Use a mixed solution of hydrochloric acid and citric acid, and leach at 50 - 80 °C for 1 - 2 hours; Leaching of copper: Use a mixed solution of dilute sulfuric acid and hydrogen peroxide, and leach at 30 - 70 °C for 1 - 2 hours; S5b: Middle fraction metal recovery: Extract tin, zinc, and silicon from the middle fraction particles: Leaching of tin and zinc: Use an acetic acid or oxalic acid buffer solution with a pH value of 4 - 6, and leach at 40 - 60 °C for 1 - 2 hours; Purification of silicon: Etch the surface oxide layer of the leached silicon particles with 5% - 10% hydrofluoric acid, wash with deionized water, and dry.

[0036] As a preferred solution, in step S6, the conditions for drying and recycling the inert residue are as follows: the inert residue is washed, dried, and briquetted to form a standard test block to complete the recycling.

[0037] The present invention effectively improves the recovery efficiency and purity of waste crystalline silicon photovoltaic modules through the magnetic density separation technology. The process is simple, environmentally friendly, and has low energy consumption, with significant economic and environmental benefits, and is suitable for large-scale industrial applications. Specifically, it is manifested as follows: improving the resource recovery rate, especially the recovery efficiency of precious metals such as silver, copper, tin, and zinc reaching over 90%; the process flow is simple and easy to control, reducing the environmental pollution risk in traditional thermal and chemical treatment methods; the energy consumption is low, the overall treatment cost is reduced, effectively improving the economic benefits; the high-purity metals obtained by recycling can be re-invested in the industrial chain to achieve closed-loop recycling of resources, significantly reducing the production cost of new materials; the non-metallic particle residues can be reused as building materials, almost achieving zero discharge of waste, and significantly improving the environmental benefits.

[0038] Adopting the technical solution of the present invention can achieve the efficient separation and resource recovery of multi-component materials in waste crystalline silicon photovoltaic modules, significantly improve the extraction efficiency of valuable metals such as silver, copper, tin, zinc and silicon, minimize material waste to the greatest extent, and avoid the drawbacks of traditional high-energy-consuming and highly polluting treatment processes. It has the advantages of environmental friendliness, low operating cost, strong process controllability, etc. In the present invention, the coupled design of magnetic density separation and wet extraction realizes the coordinated improvement of separation accuracy and metal recovery rate, provides a practical technical support for the green circular utilization of photovoltaic modules, and has good industrial application prospects.

[0039] The following are specific examples with combined specific data to further expand the above technical solutions of the present invention: Example 1: Efficient recovery of all-component metals (particle size about 1 mm) This example provides a method for separating and recycling waste crystalline silicon photovoltaic modules, which is used for separating and recycling all-component metals efficiently. The method includes the following steps: S1: Pretreatment Disassemble the retired crystalline silicon photovoltaic module, remove the aluminum alloy frame, backplane and junction box, and use the hot air softening method to strip the EVA encapsulation layer to obtain a mixed solid mainly composed of glass, silicon wafers and electrode materials.

[0040] S2: Crushing and classification Process the mixed solid through a mechanical crushing device and screen it into three particle size grades of 100–500 μm, 500 μm–3 mm, and 3–5 mm according to the particle size to obtain mixed particles with an average particle size of about 1 mm; S3: Magnetic density separation Put the mixed particles in step S2 into a magnetic fluid separation device containing Fe3O4 nanoparticles. The effective density of the magnetic fluid is 2.8 g / cm 3 , adjust the magnetic field strength to 0.6 Tesla, the temperature to 25 °C, and let it stand for stratification for 45 minutes. The separated products are: Light fraction (upper layer): mainly glass fragments and silica; Middle fraction (middle layer): rich in tin, zinc, and silicon particles; Heavy fraction (lower layer): enriched with copper wire fragments and silver solder joints.

[0041] S4: Stratified extraction Use a mechanical lifting screen to extract the fraction particles layer by layer from top to bottom. After cleaning, the magnetic fluid is recycled.

[0042] S5: Metal recovery S5a. Treatment of heavy fraction: Silver leaching: For the heavy fraction, use 10% HCl + 0.1 mol / L citric acid solution (pH≈1.5), leach at 60 °C for 2 hours, and the silver dissolution rate is 93.1%; after the leaching solution is subjected to chlorination precipitation, it is electrolytically purified, and the purity of silver powder > 99.9%.

[0043] Copper leaching: For the heavy fraction, use 0.5 mol / L H2SO4 + 5% H2O2, leach at 60 °C for 1 hour, and the copper recovery rate is 90.5%; the cathode electrowinning voltage is 0.4–0.6 V, and the copper purity > 99.5%.

[0044] S5b. Middle fraction treatment: Tin / zinc leaching: In the middle fraction, tin and zinc exist in the form of SnO2 and ZnO particles respectively. Use an acetic acid buffer solution with pH = 5.2, leach at 50 °C for 2 hours, and the extraction rates of tin and zinc are 89.2% and 85.7% respectively.

[0045] Silicon purification: The residue of the middle fraction is etched with 5% hydrofluoric acid for 15 minutes to remove the oxide layer, rinsed with deionized water and dried, and the silicon purity is 98.5%.

[0046] S6: Residue treatment The glass and SiO2 in the light fraction are de-liquored and dried after magnetic fluid rinsing, and then formed into high-pressure compacts (pressure 15 MPa), with a compressive strength of 3 MPa, and used as non-load-bearing building fillers.

[0047] Example 1 demonstrates an efficient recovery method for waste crystalline silicon photovoltaic modules with a full-component mixed particle size (about 1 mm). Through the synergistic effect of magnetic density separation and directional leaching processes, high-value recovery of multiple metals is achieved. In the pretreatment stage, the EVA layer is peeled off by the hot air softening method to ensure the complete dissociation of glass, silicon wafers, and electrode materials; after crushing and grading, the mixed particles are directly processed to avoid efficiency losses caused by complex screening; in the magnetic density separation step, 2.8 g / cm 3Magnetic fluid and a 0.6 T magnetic field were used to accurately separate light fractions (glass / SiO2), middle fractions (SnO2 / ZnO / silicon), and heavy fractions (Cu / Ag) within 45 minutes. For the heavy fraction, silver was leached using a hydrochloric acid-citric acid system (60 °C, 2 h) with a recovery rate of 93.1%, and the purity after electrolysis was >99.9%. Copper was simultaneously leached using a dilute sulfuric acid-hydrogen peroxide system with a recovery rate of 90.5%, and the purity of electrowon copper was >99.5%. Tin (89.2%) and zinc (85.7%) were selectively extracted from the middle fraction using a pH = 5.2 acetic acid buffer solution, and silicon particles were purified to 98.5% through etching with 5% hydrofluoric acid. The glass residue of the light fraction achieved a compressive strength of 3 MPa after high-pressure briquetting (15 MPa), realizing its utilization as building materials. This solution had low comprehensive energy consumption, a metal recovery rate exceeding 90%, and a residue utilization rate >99%, verifying the feasibility of mixed particle size treatment and providing an efficient and low-cost solution for large-scale module recycling.

[0048] Example 2: This example provides a method for separating and recycling waste crystalline silicon photovoltaic modules, which separates and recycles particles in the 500 μm–3 mm particle size range. The method includes the following steps: S1: Pretreatment The retired crystalline silicon photovoltaic modules were disassembled, the aluminum alloy frames, backsheets, and junction boxes were removed, and the EVA encapsulation layer was peeled off using the hot air softening method to obtain a mixed solid mainly composed of glass, silicon wafers, and electrode materials.

[0049] S2: Crushing and classification The mixed solid was processed using a mechanical crushing device to obtain particles with an average particle size of approximately 1 mm, which were screened into three particle size ranges: 100–500 μm, 500 μm–3 mm, and 3–5 mm (in this example, the 500 μm–3 mm particle size range particles after crushing and screening were selected).

[0050] S3: Magnetic density separation The 500 μm–3 mm particle size range particles were put into a magnetic fluid separation device containing Fe3O4 nanoparticles. The density of the magnetic fluid was 2.3 g / cm 3 , the magnetic field strength was 0.4 tesla, and after standing for 30 minutes, three layers of fractions were produced: Light fraction (upper layer): glass and finely crushed silicon powder; Middle fraction (middle layer): Zn, Sn, Si mixed particles; Heavy fraction (lower layer): copper and silver debris.

[0051] S4: Layered extraction An adjustable siphon was used to extract each fraction layer by layer.

[0052] S5: Metal recovery S5a. Heavy fraction treatment: Silver leaching: Use 10% HCl + 0.1 mol / L citric acid for the heavy fraction, leach at 60 °C for 1.5 hours, and the silver extraction rate is 91.8%; after AgCl precipitation, ammonia complexation electrolysis is carried out.

[0053] Copper leaching: Use 0.25 mol / L H2SO4 + 2% H2O2 for the heavy fraction, leach at 45 °C for 1 hour, and the copper recovery rate is 88.4%; high-purity copper is obtained by electrolysis.

[0054] S5b. Medium fraction treatment: Tin / zinc leaching: Use pH = 5.0 acetic acid-oxalic acid buffer solution for the medium fraction, leach at 55 °C for 1 hour, and the extraction rates of Sn and Zn are 86.9% and 82.5% respectively.

[0055] Silicon purification: Immerse the residue of the medium fraction in 5% hydrofluoric acid for 15 minutes, and the silicon purity is 97.9%.

[0056] S6: Residue treatment For the light fraction glass powder, remove impurities through a high-frequency vibrating screen, dry it with hot air (moisture content < 1%), and then press it into blocks for use as road base materials.

[0057] Example 2 optimizes the recovery process for medium-sized (500 μm–3 mm) particles. Through classification treatment and parameter adaptation, the metal separation accuracy is significantly improved: In this example, after pretreatment, the 500 μm–3 mm particle size fraction is selected by screening, and the magnetic density separation uses 2.3 g / cm 3 Magnetic fluid and a 0.4 T magnetic field to separate the light fraction (glass / silica powder), medium fraction (Zn / Sn / Si), and heavy fraction (Cu / Ag debris) within 30 minutes; for the silver in the heavy fraction, use the hydrochloric acid-citric acid system (60 °C, 1.5 h) for leaching, and the extraction rate is 91.8%; for copper, use 0.25 mol / L H2SO4 + 2% H2O2 for leaching (45 °C, 1 h), and the recovery rate is 88.4%. For the medium fraction, extract tin (86.9%) and zinc (82.5%) through a pH = 5.0 acetic acid-oxalic acid buffer solution (55 °C, 1 h), and the silicon purity reaches 97.9% after treatment with 5% hydrofluoric acid. The light fraction glass powder is dried and pressed into blocks for use as road base materials, with a moisture content < 1% and a density uniformity of ±5%; this solution reduces energy consumption, the recovery rates of copper and silver both exceed 88%, and the silicon purity meets the photovoltaic reuse standard, which is suitable for large-scale treatment of medium-sized components and has the advantages of both efficiency and economy.

[0058] Example 3: S1: Pretreatment The retired crystalline silicon photovoltaic modules are disassembled, the aluminum alloy frames, backsheets and junction boxes are removed, and the EVA encapsulation layer is peeled off by the hot air softening method to obtain a mixed solid mainly composed of glass, silicon wafers and electrode materials.

[0059] S2: Crushing and classification The mixed solid is processed by mechanical crushing equipment to obtain particles with an average particle size of about 1 mm, and sieved into three particle size grades of 100–500 μm, 500 μm–3 mm, and 3–5 mm according to the particle size (in this embodiment, the 100–500 μm fine particles obtained by sieving are selected).

[0060] S3: Magnetic density separation The particles are put into a magnetic fluid separation device containing Fe3O4 nanoparticles, the density of the magnetic fluid is 2.0 g / cm 3 , the magnetic field strength is 0.3 Tesla, and after standing for 30 minutes, the following are separated out: Light fraction (upper layer): glass and SiO2; Medium fraction (middle layer): silicon and trace amounts of Sn and Zn; Heavy fraction (lower layer): Ag / Cu alloy microparticles.

[0061] S4: Layered extraction Mechanical screen layered extraction, the recovery rate of the magnetic fluid > 95%.

[0062] S5: Metal recovery S5a. Treatment of the heavy fraction: Silver leaching: 1 mol / L NH4Cl solution (pH = 8) is used, stirred at room temperature for 1.5 hours, and the silver recovery rate is 91.2%; after AgCl precipitation, it is reduced and purified.

[0063] Copper leaching: A mixed solution of nitric acid + acetic acid is used, leached at room temperature for 2 hours, and the copper recovery rate is 91.3%; high-purity copper is obtained by electrolysis.

[0064] S5b. Treatment of the medium fraction: Tin / zinc leaching: The medium fraction is treated with a sodium oxalate buffer system (pH = 5.5), leached at 55 °C for 1 hour, and the extraction rates of Sn and Zn are 88.1% and 84.6% respectively.

[0065] Silicon purification: The residue of the medium fraction is subjected to dry air classification + surface polishing, and the silicon purity is 99.5%.

[0066] S6: Residue treatment The light fraction glass and SiO2 particles are pressed into blocks with a compressive strength of 3.5 MPa and used as non-structural building materials.

[0067] This embodiment focuses on the component recovery of fine-grained (100–500 μm) particles. Through low-density magnetic fluid and fine leaching process, the problem of micron-scale metal recovery has been overcome. After screening, the fine particles in this embodiment are treated with 2.0 g / cm 3 magnetic fluid and a 0.3 T magnetic field, and the light fraction (glass / SiO2), middle fraction (Si / Sn / Zn), and heavy fraction (Ag / Cu alloy particles) are separated within 30 minutes. For micron-scale silver and copper particles, this embodiment uses 1 mol / L NH4Cl complex leaching (pH = 8, room temperature, 1.5 h), with a silver recovery rate of 91.2%; a nitric acid-acetic acid mixed solution leaches copper at room temperature for 2 hours, with a recovery rate of 91.3%; the middle fraction extracts tin (88.1%) and zinc (84.6%) through a sodium oxalate buffer system (pH = 5.5, 55 °C, 1 h), and the purity of silicon reaches 99.5% after dry air classification and polishing, with an oxygen content <200 ppm, which can be directly used for monocrystalline silicon preparation; the compressive strength of the light fraction glass briquette is 3.5 MPa, which is better than the conventional building material standard. This solution has low energy consumption, and both the silicon purity and metal recovery rate reach new highs, especially suitable for the recovery of micron-scale complex components, providing a technical model for high-value resource regeneration.

[0068] Through the above embodiments, it is further proved that the present invention provides a method for recycling waste crystalline silicon photovoltaic modules based on the synergistic effect of magnetic density separation and directional leaching. The core principle of the present invention is: by regulating the density gradient and magnetic field strength of Fe3O4 magnetic fluid, different density metal and non-metal components are accurately separated, and combined with specific leaching processes to achieve the efficient extraction of multiple metals; the technical advantages of the present invention are reflected in three aspects: First, the process efficiency is significantly improved. The combination of mixed particle size treatment (Example 1) and classification optimization (Examples 2 and 3) results in silver and copper recovery rates both exceeding 90%, and the silicon purity reaches 98.5%–99.5%, which is more than 30% more efficient than traditional incineration or acid bath methods; Second, the environmental friendliness is outstanding: the method of the present invention adopts a closed-loop resource utilization design, with a building material utilization rate of glass residue >99%, a 70% reduction in hydrofluoric acid consumption, and no heavy metal waste liquid discharge; Third, the economic cost is greatly reduced. In the present invention, the magnetic fluid can be recycled, and the comprehensive energy consumption is greatly reduced compared with the existing technology. The present invention effectively solves the problems of high metal mixing degree, low separation efficiency, and serious secondary pollution in traditional recovery processes, providing a technical solution with high efficiency, environmental protection, and economy for the large-scale retirement treatment of photovoltaic modules.

[0069] In the description of the present application, the descriptions with reference to terms such as "one embodiment", "some embodiments", "in this embodiment", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0070] As described above, it is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A separation and recovery method for waste crystalline silicon photovoltaic modules, characterized in that, It includes the following steps: S1： Pretreatment: Disassemble the waste crystalline silicon photovoltaic modules to be separated and recycled, remove the aluminum alloy frames, backsheets and EVA encapsulation layers to obtain a mixed solid mainly composed of glass, silicon wafers and electrode materials; S2: Crushing and classification: Crush the mixed solid obtained in step S1 to obtain particles with a particle size of 100 μm to 5 mm, and divide the particles into three particle size grades according to the particle size; S3: Magnetic density separation: Perform magnetic density separation on the three particle size grades of particles obtained in step S2 respectively. The magnetic density separation includes the following steps: Put the particles into a magnetic fluid separation device. The magnetic fluid is an aqueous suspension containing Fe3O4 nanoparticles. By adjusting the magnetic field strength, a vertical density gradient is formed in the aqueous suspension, and after standing and layering, a light fraction, a middle fraction and a heavy fraction are separated; S4: Layered extraction: Extract the light fraction, middle fraction and heavy fraction in step S3 layer by layer, and recover the magnetic fluid after washing; S5: Metal recovery: Perform metal recovery treatment on the middle fraction and heavy fraction obtained in step S4 to obtain metals and inert residues; S6: Dry and recycle the inert residue of the light fraction to complete the separation and recovery.

2. The separation and recovery method of the scrapped crystalline silicon photovoltaic module according to claim 1, wherein, In step S2, the three particle size grades are 100 - 500 μm, 500 μm - 3 mm, and 3 mm - 5 mm in sequence.

3. The separation and recovery method of the scrapped crystalline silicon photovoltaic module according to claim 1, characterized in that In the step S3, in the water-based suspension, the effective density range of the magnetic fluid is 1.5 to 3.8 g / cm 3 .

4. The separation and recycling method of the scrapped crystalline silicon photovoltaic module according to claim 1, wherein In step S3, the conditions for adjusting the magnetic field strength are: control the magnetic field strength to be 0.3 - 0.7 Tesla; the temperature of the aqueous suspension is 20 - 30 °C.

5. The separation and recovery method of the scrapped crystalline silicon photovoltaic module according to claim 1, characterized in that, In step S3, the light fraction contains glass and silicon-containing compounds; the middle fraction contains tin compounds, zinc compounds and silicon materials; the heavy fraction contains copper-based materials and silver-based materials.

6. The separation and recovery method of the scrapped crystalline silicon photovoltaic module according to claim 1, wherein In step S4, the conditions for layer-by-layer extraction are: Extract the fraction particles layer by layer from top to bottom in sequence through a siphon with adjustable height or a mechanically lifted sieve.

7. The separation and recovery method of the scrapped crystalline silicon photovoltaic module according to claim 1, characterized in that, In step S5, the conditions for the metal recovery treatment are: Leach the light fraction, middle fraction and heavy fraction to obtain a leachate, and then complete the recovery through electrolysis or chemical precipitation.

8. The separation and recovery method of the scrapped crystalline silicon photovoltaic module according to claim 7, wherein, In step S5, the metal recovery treatment includes the following steps: S5a. Heavy fraction metal recovery: Extract silver and copper from the heavy fraction particles: Leaching of silver: Use a mixed solution of hydrochloric acid and citric acid, and leach at 50 - 80 °C for 1 - 2 hours; Leaching of copper: Use a mixed solution of dilute sulfuric acid and hydrogen peroxide, and leach at 30 - 70 °C for 1 - 2 hours; S5b: Middle fraction metal recovery: Extract tin, zinc and silicon from the middle fraction particles: Leaching of tin and zinc: Use an acetic acid or oxalic acid buffer solution with a pH value of 4 - 6, and leach at 40 - 60 °C for 1 - 2 hours; Purification of silicon: Etch the surface oxide layer of the leached silicon particles with 5% - 10% hydrofluoric acid, and wash and dry with deionized water.

9. The separation and recovery method of the scrapped crystalline silicon photovoltaic module according to claim 1, characterized in that, In step S6, the conditions for drying and recycling the inert residue are: Wash, dry and compact the inert residue to make a standard test block to complete the recovery.

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