A method for recycling silver and aluminum from waste crystalline silicon photovoltaic modules using molten salt

Abstract

This invention belongs to the field of photovoltaic waste resource recycling technology, and discloses a method for recovering silver and aluminum from waste crystalline silicon photovoltaic modules using molten salt. The method includes: pre-treating the waste crystalline silicon photovoltaic modules to obtain solar cells; immersing the solar cells in a continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system to obtain solar cells coated with molten salt; heat-treating the solar cells coated with molten salt to obtain a separated mixture; mixing the separated mixture with water, and subjecting it to ultrasonic vibration, filtration, and airflow separation to obtain a mixture of silicon wafers and silver-aluminum solid metal. This invention, based on a continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system for recovering silver and aluminum from waste crystalline silicon photovoltaic modules, features a simple process, low wastewater and waste gas volume, and simple and safe operation.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic waste resource recycling technology, and more specifically, relates to a method for recycling silver and aluminum from waste crystalline silicon photovoltaic modules using molten salt. Background Technology

[0002] With the rapid development of the global photovoltaic industry, the number of retired photovoltaic modules has increased dramatically. Statistics show that by 2030, the global volume of retired photovoltaic modules will exceed 10 million tons, containing large amounts of valuable metals (silver, aluminum, copper, etc.) and high-purity silicon wafers. Traditional methods for recycling retired photovoltaic modules mainly include mechanical crushing, heat treatment, and acid leaching, which have the following problems: 1. Mechanical crushing cannot effectively separate silicon wafers from silver and aluminum; 2. The heat treatment process generates toxic gases from the combustion of the packaging material, polluting the environment; 3. Acid leaching uses a large amount of strong acid (such as nitric acid, hydrochloric acid, etc.), has a long process flow, and generates nitrogen oxide gas and a large amount of wastewater.

[0003] Therefore, it is essential to develop a simple process that produces less wastewater and waste gas and is easy and safe to operate for recycling silver and aluminum from waste crystalline silicon photovoltaic modules. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for recovering silver and aluminum from waste crystalline silicon photovoltaic modules using molten salt. This invention utilizes a continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system to recover silver and aluminum from waste crystalline silicon photovoltaic modules, featuring a simple process, low wastewater and waste gas volume, and easy and safe operation.

[0005] To achieve the above objectives, the present invention provides a method for recovering silver and aluminum from waste crystalline silicon photovoltaic modules using molten salt, the method comprising the following steps: S1: Preprocessing Waste crystalline silicon photovoltaic modules are pretreated to obtain solar cells; S2: Molten salt immersion Potassium nitrate, sodium nitrate, and magnesium oxide with a particle size of 0.1-50 μm are ground and mixed in the corundum ball mill jar of a planetary ball mill under nitrogen protection and in a sealed environment for 30-120 min to obtain a premixed powder. After heating the premixed powder to 200-300℃, continuous mechanical stirring is performed to ensure that magnesium oxide is uniformly suspended in sodium nitrate-potassium nitrate binary molten salt, thus obtaining a continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system. The battery cell, which is placed in a porous mesh basket, is immersed in the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixture for 1-3 minutes, and the immersion temperature is maintained at 200-300℃, so that the surface of the removed battery cell is completely covered by the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixture, and a battery cell with molten salt attached is obtained. Based on the total weight of the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system, the content of potassium nitrate is 40-60 wt%, the content of sodium nitrate is 30-50 wt%, and the content of magnesium oxide is 5-15 wt%. The mass ratio of the battery cell to the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system is 1:(2-5). S3: Etching Separation The battery cell coated with molten salt is removed from the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixture, and the salt is drained for 2-5 seconds. Within 20-60 seconds, it is transferred to a muffle furnace for heat treatment at a temperature of 300-450℃ for 5-10 minutes to obtain a separated mixture. The separated mixture is then mixed with water, subjected to ultrasonic vibration, and filtered to obtain filter residue and filtrate. The filter residue is placed in a vertical airflow separation device, and the airflow velocity is controlled at 3-8 m / s. By utilizing the difference in suspension velocity between silicon wafers and silver-aluminum mixed solid metal in the airflow, silicon wafers and silver-aluminum mixed solid metal are obtained respectively.

[0006] According to the present invention, preferably, the pretreatment includes the following steps: Component disassembly: The frame, junction box and front glass of the waste crystalline silicon photovoltaic module are disassembled and removed to obtain the disassembled module; Component cutting: The disassembled components are cut into cutting blocks; Backplate peeling: The cutting block is heated, and the backplate on the heated cutting block is peeled off using a hot knife to obtain the battery layer containing adhesive film. N-Methylpyrrolidone Immersion: The battery layer containing the adhesive film is immersed in NMP to remove residual adhesive film, stirred, and then washed with water and dried to obtain the battery cell.

[0007] According to the present invention, preferably, in the component disassembly: The removed frame is recycled as an aluminum source; The disassembled junction boxes are recycled as plastic waste.

[0008] In this invention, the equipment used for disassembling the components includes a hydraulic disassembly machine and a glass removal machine.

[0009] According to the present invention, preferably, in the component cutting: the size of the cutting block is (4-5) cm × (4-5) cm. More preferably, it is 5 cm × 5 cm or 4 cm × 4 cm. During cutting, care should be taken to ensure the regularity of the cutting block to avoid irregular shapes affecting subsequent processing.

[0010] In this invention, the equipment used to cut the component is a cutting machine.

[0011] According to the present invention, preferably, in the backsheet peeling process: the cutting block is heated to 110-180°C. The adhesive film between the backsheet and the battery on the heated cutting block is cut using a hot blade, thereby achieving the peeling and removal of the backsheet, ensuring the integrity of the backsheet, improving recycling efficiency, and obtaining a battery layer containing the adhesive film.

[0012] According to the present invention, preferably, in the N-methylpyrrolidone immersion: The adhesive-containing battery layer is immersed in NMP at a temperature of 80-100℃ for 10-30 minutes. The stirring rate is 20-60 r / min (in order to accelerate the dissolution and removal of residual EVA film on the battery layer containing the adhesive film). The method further includes distilling the NMP after soaking the adhesive-containing battery layer to recover the NMP for reuse; the washing and drying process includes: using deionized water to remove the residual NMP on the battery cell after removing the adhesive film, and placing it in a drying oven to dry at 105°C for 20-60 minutes to make the surface of the battery cell free of water; as a preferred embodiment, the distillation temperature for the N-methylpyrrolidone after soaking the adhesive-containing battery layer is 202°C (the boiling point of N-methylpyrrolidone).

[0013] In this invention, the purity of the N-methylpyrrolidone is ≥99.5%. When the adhesive-containing battery layer is immersed in N-methylpyrrolidone, it is necessary to ensure that the N-methylpyrrolidone completely submerges the adhesive-containing battery layer.

[0014] According to the present invention, preferably, in step S2: Nitrogen protection reduces the oxygen content in the corundum grinding jar of the sealed planetary ball mill to ≤5%; The ball-to-material mass ratio in the corundum ball mill jar is 5:1-10:1, and the filling rate is 30-50%. The balls used in planetary ball mills are corundum grinding balls with a diameter of 5-10mm; The planetary ball mill has a revolution speed of 200-400 r / min and a rotation speed of 400-800 r / min. The equipment used for continuous mechanical stirring is a top-mounted paddle stirrer or magnetic stirrer, with the stirring speed controlled at 200-400 r / min.

[0015] According to the present invention, preferably, the ultrasonic oscillation time is 0.5-3 min, more preferably 1 min.

[0016] According to the present invention, preferably, the method further includes silver-aluminum separation: (1) The silver-aluminum mixed solid metal is mixed with an aqueous sodium hydroxide solution, stirred, and filtered to obtain silver wire and an alkaline solution containing sodium aluminate; (2) Wash the silver wire with water to remove the alkaline salts adhering to the surface of the silver wire; (3) Carbon dioxide is introduced into the alkaline solution containing sodium aluminate until the pH of the solution system is 7.5-8.5, preferably 8, to generate aluminum hydroxide precipitate, which is then filtered, washed and calcined to obtain aluminum oxide powder.

[0017] According to the present invention, preferably, in step (1): The sodium hydroxide aqueous solution has a mass fraction of 16-30 wt%, preferably 20 wt%. The liquid-solid mass ratio of the silver-aluminum mixed solid metal to the sodium hydroxide aqueous solution is 2:1-8:1, preferably 4:1; The stirring temperature is 50-80℃, the stirring speed is 80-120 r / min, and the stirring time is 30-60 min.

[0018] According to the present invention, preferably, in step (3): Carbon dioxide is introduced into the alkaline solution containing sodium aluminate at an inlet rate of 0.8-1.5 L / min, preferably 1.0 L / min; The calcination temperature is 900-1200℃, preferably 950℃, and the time is 1-2h, preferably 1h.

[0019] The beneficial effects of the technical solution of this invention are as follows: This invention recovers silver and aluminum from waste crystalline silicon photovoltaic modules based on a continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system. It features a simple process, low wastewater and waste gas volume, and simple and safe operation. Specifically: The molten salt etching mechanism of this invention is as follows: at high temperature, nitrate ions (NO3) in molten nitrate... - The corrosion effect on the interface between the silver grid lines and aluminum layer (or aluminum electrode) in the solar cell and the silicon wafer destroys the interface between the silver grid lines / aluminum layer and the silicon wafer, thereby causing the silver grid lines to peel off from the silicon wafer surface and the aluminum layer to separate from the silicon wafer.

[0020] The method of this invention is simple: after physical disassembly, the battery cells are obtained, and the battery cells can be separated and recovered by molten salt etching, ultrasonication, gas separation and alkali dissolution, which is suitable for large-scale industrial production.

[0021] The method of this invention produces less wastewater and waste gas: acid leaching produces a large amount of acid and alkali wastewater, while this invention produces only a small amount of alkali solution and rinsing wastewater, resulting in a lower wastewater volume than acid leaching; compared with heat treatment, heat treatment produces a large amount of waste gas due to the decomposition of the backplate and EVA adhesive, while this invention only produces a small amount of waste gas during the etching process.

[0022] The method of this invention is simple and safe to operate: Compared with immersing the battery cells in the system for a long time to separate the metal, this invention first immerses the battery cells in the ternary mixed system for a short time, and then etches the battery cells with molten salt attached. It does not require the battery cells to be kept in a high-temperature molten salt environment continuously, which makes them easy to remove, reduces the safety risks of high-temperature operation, and has lower requirements for production equipment.

[0023] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0024] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings.

[0025] Figure 1 The diagram shows a process flow diagram of a method for recycling silver and aluminum from waste crystalline silicon photovoltaic modules using molten salt, as provided by the present invention.

[0026] Figure 2 The image shows a physical picture of the silver wire recovered as a product of a method for recycling silver and aluminum from waste crystalline silicon photovoltaic modules using molten salt, as provided in Embodiment 1 of the present invention.

[0027] Figure 3 The image shows a physical photograph of a method for recovering silver and aluminum from waste crystalline silicon photovoltaic modules using molten salt, as provided in Embodiment 1 of the present invention. Detailed Implementation

[0028] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0029] The following embodiments: The waste crystalline silicon photovoltaic modules come from retired waste crystalline silicon photovoltaic modules from LONGi Green Energy.

[0030] Example 1

[0031] This embodiment provides a method for recovering silver and aluminum from waste crystalline silicon photovoltaic modules using molten salt, such as... Figure 1As shown, the method includes the following steps: S1: Preprocessing Component disassembly: A hydraulic disassembly machine is used to disassemble and remove the frame and junction box of the waste crystalline silicon photovoltaic module, and a glass removal machine is used to remove the front glass to obtain the disassembled module; the disassembled frame, junction box and front glass are recycled. Component cutting: The disassembled components (i.e., photovoltaic module laminates) are cut into 5cm×5cm pieces; Backsheet peeling: The cutting block is heated to 160°C, and the adhesive film between the backsheet and the battery is cut on the heated cutting block using a hot blade, thereby peeling off the backsheet. This ensures the integrity of the backsheet, improves recycling efficiency, and yields a battery layer containing adhesive film. N-Methylpyrrolidone Immersion: The battery layer containing the adhesive film is immersed in NMP (purity ≥99.5%) at 100°C for 20 minutes to remove the residual adhesive film. During this period, continuous stirring is performed (speed 40 r / min). After the removal, the residual NMP on the battery cell after the adhesive film is removed is washed away with deionized water. Then, it is placed in a drying oven and dried at 105°C for 40 minutes to obtain a battery cell with an aqueous surface.

[0032] S2: Molten salt immersion

[0033] Potassium nitrate, sodium nitrate, and magnesium oxide with a particle size of 10 μm were ground and mixed in the corundum ball mill jar of a planetary ball mill under nitrogen protection for 100 min, so that magnesium oxide was evenly distributed in the powders of potassium nitrate and sodium nitrate, resulting in a premixed powder. The nitrogen protection was maintained to reduce the oxygen content in the corundum ball mill jar to ≤5%, the ball-to-material mass ratio in the corundum ball mill jar was 8:1, and the filling rate was 30%. Corundum grinding balls with a diameter of 5 mm were used in the planetary ball mill. The planetary ball mill's revolution speed was 400 r / min, and its rotation speed was 800 r / min. After heating the premixed powder to 250°C, continuous mechanical stirring is performed to achieve solid-liquid suspension, ensuring that magnesium oxide is uniformly suspended in the sodium nitrate-potassium nitrate binary molten salt, thus obtaining a continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system; wherein, the equipment used for continuous mechanical stirring is a magnetic stirrer, and the stirring speed is controlled at 200 r / min; The battery cell is placed in a porous mesh basket, and then the battery cell placed in the porous mesh basket is immersed in the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system for 3 minutes, with the immersion temperature maintained at 250°C, so that the surface of the removed battery cell is completely covered by the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system, resulting in a battery cell with molten salt attached. Based on the total weight of the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system, the content of potassium nitrate is 50 wt%, the content of sodium nitrate is 40 wt%, and the content of magnesium oxide is 10 wt%. The mass ratio of the battery cell to the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixture is 1:3.

[0034] S3: Etching Separation

[0035] The battery cell with molten salt attached is removed from the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixture system, the salt is drained for 2 seconds, and then transferred to a muffle furnace for heat treatment within 30 seconds (to separate the silver grid lines and aluminum layer of the battery cell from the silicon wafer). The heat treatment temperature is 450°C and the heat treatment holding time is 7 minutes to obtain a separated mixture. The separated mixture is mixed with water (using water to cool the separated mixture), subjected to ultrasonic vibration (to remove silver wires and sheet-like aluminum aggregates from the battery cells) for 2 minutes, and filtered to obtain filter residue and filtrate; The filter residue is placed in a vertical airflow separation device, and the airflow velocity is controlled at 5 m / s. By utilizing the difference in suspension velocity between silicon wafers and silver-aluminum mixed solid metal in the airflow, silicon wafers and silver-aluminum mixed solid metal are obtained respectively.

[0036] S4: Silver-aluminum separation

[0037] (1) The silver-aluminum mixed solid metal was mixed with 20wt% sodium hydroxide aqueous solution (liquid-solid mass ratio of 2:1), stirred (70℃, 120r / min, 50min), and filtered to obtain silver wire and an alkaline solution containing sodium aluminate; (2) Wash the silver wire with water to remove the alkaline salts adhering to the surface of the silver wire; (3) Carbon dioxide is introduced into the alkaline solution containing sodium aluminate at an inlet rate of 1.0 L / min until the pH value of the solution system is 7.5, generating aluminum hydroxide precipitate, which is then filtered, washed and calcined (calcined at 950℃ for 1 h) to obtain alumina powder.

[0038] Example 2

[0039] This embodiment provides a method for recovering silver and aluminum from waste crystalline silicon photovoltaic modules using molten salt, such as... Figure 1 As shown, the method includes the following steps: S1: Preprocessing Component disassembly: A hydraulic disassembly machine is used to disassemble and remove the frame and junction box of the waste crystalline silicon photovoltaic module, and a glass removal machine is used to remove the front glass to obtain the disassembled module; the disassembled frame, junction box and front glass are recycled. Component cutting: The disassembled components (i.e., photovoltaic module laminates) are cut into 4cm×4cm pieces; Backsheet peeling: The cutting block is heated to 180°C, and the adhesive film between the backsheet and the battery is cut on the heated cutting block using a hot blade, thereby peeling off the backsheet. This ensures the integrity of the backsheet, improves recycling efficiency, and yields a battery layer containing adhesive film. N-Methylpyrrolidone Immersion: The battery layer containing the adhesive film is immersed in NMP (purity ≥99.5%) at 90°C for 30 min to remove the residual adhesive film. During this period, continuous stirring is performed (speed 60 r / min). After the removal, the residual NMP on the battery cell after the adhesive film is removed is washed away with deionized water. Then, it is placed in a drying oven and dried at 105°C for 40 min to obtain a battery cell with an aqueous surface.

[0040] S2: Molten salt immersion

[0041] Potassium nitrate, sodium nitrate, and magnesium oxide with a particle size of 2 μm were ground and mixed in the corundum ball mill jar of a planetary ball mill under nitrogen protection for 120 min, so that magnesium oxide was evenly distributed in the powders of potassium nitrate and sodium nitrate, resulting in a premixed powder. The nitrogen protection was maintained to reduce the oxygen content in the corundum ball mill jar to ≤5%, the ball-to-material mass ratio in the corundum ball mill jar was 10:1, and the filling rate was 40%. Corundum grinding balls with a diameter of 8 mm were used in the planetary ball mill. The planetary ball mill's revolution speed was 300 r / min, and its rotation speed was 800 r / min. After heating the premixed powder to 250°C, continuous mechanical stirring is performed to achieve solid-liquid suspension, ensuring that magnesium oxide is uniformly suspended in the sodium nitrate-potassium nitrate binary molten salt, thus obtaining a continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system; wherein, the equipment used for continuous mechanical stirring is a magnetic stirrer, and the stirring speed is controlled at 300 r / min; The battery cell is placed in a porous mesh basket, and then the battery cell placed in the porous mesh basket is immersed in the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system for 3 minutes, with the immersion temperature maintained at 300°C, so that the surface of the removed battery cell is completely covered by the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system, thus obtaining a battery cell with molten salt attached. Based on the total weight of the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system, the content of potassium nitrate is 50 wt%, the content of sodium nitrate is 35 wt%, and the content of magnesium oxide is 15 wt%. The mass ratio of the battery cell to the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixture is 1:5.

[0042] S3: Etching Separation

[0043] The battery cell with molten salt attached is removed from the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixture system, the salt is drained for 5 seconds, and then transferred to a muffle furnace for heat treatment within 60 seconds (to separate the silver grid lines and aluminum layer of the battery cell from the silicon wafer). The heat treatment temperature is 400°C and the heat treatment holding time is 10 minutes to obtain a separated mixture. The separated mixture is mixed with water (using water to cool the separated mixture), subjected to ultrasonic vibration (to remove silver wires and sheet-like aluminum aggregates from the battery cells) for 1 minute, and filtered to obtain filter residue and filtrate; The filter residue is placed in a vertical airflow separation device, and the airflow velocity is controlled at 8 m / s. By utilizing the difference in suspension velocity between silicon wafers and silver-aluminum mixed solid metal in the airflow, silicon wafers and silver-aluminum mixed solid metal are obtained respectively.

[0044] S4: Silver-aluminum separation

[0045] (1) The silver-aluminum mixed solid metal was mixed with 30wt% sodium hydroxide aqueous solution (liquid-solid mass ratio of 4:1), stirred (80℃, 100r / min, 60min), and filtered to obtain silver wire and an alkaline solution containing sodium aluminate; (2) Wash the silver wire with water to remove the alkaline salts adhering to the surface of the silver wire; (3) Carbon dioxide is introduced into the alkaline solution containing sodium aluminate at an inlet rate of 1.0 L / min until the pH value of the solution system is 8, aluminum hydroxide precipitate is generated, and then filtered, washed and calcined (calcined at 1000℃ for 1 h) to obtain alumina powder.

[0046] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for recovering silver and aluminum from waste crystalline silicon photovoltaic modules using molten salt, characterized in that, The method includes the following steps: S1: Preprocessing Waste crystalline silicon photovoltaic modules are pretreated to obtain solar cells; S2: Molten salt immersion Potassium nitrate, sodium nitrate, and magnesium oxide with a particle size of 0.1-50 μm are ground and mixed in the corundum ball mill jar of a planetary ball mill under nitrogen protection and in a sealed environment for 30-120 min to obtain a premixed powder. After heating the premixed powder to 200-300℃, continuous mechanical stirring is performed to ensure that magnesium oxide is uniformly suspended in sodium nitrate-potassium nitrate binary molten salt, thus obtaining a continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system. The battery cell, which is placed in a porous mesh basket, is immersed in the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixture for 1-3 minutes, and the immersion temperature is maintained at 200-300℃, so that the surface of the removed battery cell is completely covered by the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixture, and a battery cell with molten salt attached is obtained. Based on the total weight of the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system, the content of potassium nitrate is 40-60 wt%, the content of sodium nitrate is 30-50 wt%, and the content of magnesium oxide is 5-15 wt%. The mass ratio of the battery cell to the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixed system is 1:(2-5). S3: Etching Separation The battery cell coated with molten salt is removed from the continuously stirred sodium nitrate-potassium nitrate molten salt-magnesium oxide mixture, and the salt is drained for 2-5 seconds. Within 20-60 seconds, it is transferred to a muffle furnace for heat treatment at a temperature of 300-450℃ for 5-10 minutes to obtain a separated mixture. The separated mixture is then mixed with water, subjected to ultrasonic vibration, and filtered to obtain filter residue and filtrate. The filter residue is placed in a vertical airflow separation device, and the airflow velocity is controlled at 3-8 m / s. By utilizing the difference in suspension velocity between silicon wafers and silver-aluminum mixed solid metal in the airflow, silicon wafers and silver-aluminum mixed solid metal are obtained respectively.

2. The method for recovering silver and aluminum from waste crystalline silicon photovoltaic modules using molten salt according to claim 1, wherein, The preprocessing includes the following steps: Component disassembly: The frame, junction box and front glass of the waste crystalline silicon photovoltaic module are disassembled and removed to obtain the disassembled module; Component cutting: The disassembled components are cut into cutting blocks; Backplate peeling: The cutting block is heated, and the backplate on the heated cutting block is peeled off using a hot knife to obtain the battery layer containing adhesive film. N-Methylpyrrolidone Immersion: The battery layer containing the adhesive film is immersed in NMP to remove residual adhesive film, stirred, and then washed with water and dried to obtain the battery cell.

3. The method for recovering silver and aluminum from waste crystalline silicon photovoltaic modules using molten salt according to claim 2, wherein, In the component disassembly: The removed frame is recycled as an aluminum source; The junction boxes removed during disassembly will be recycled as plastic waste. In the component cutting: the size of the cutting block is (4-5)cm × (4-5)cm; In the backplate peeling process: the cutting block is heated to 110-180°C; In the N-methylpyrrolidone immersion: The adhesive-containing battery layer is immersed in NMP at a temperature of 80-100℃ for 10-30 minutes. The stirring rate is 20-60 r / min; The method further includes distilling the NMP after soaking the adhesive film battery layer to recover the NMP for reuse. The washing and drying process includes: using deionized water to remove residual NMP from the battery cells after removing the adhesive film, and then placing them in a drying oven at 105°C for 20-60 minutes to dry the surface of the battery cells until they are free of water.

4. The method for recovering silver and aluminum from waste crystalline silicon photovoltaic modules using molten salt according to claim 1, wherein, In step S2: Nitrogen protection reduces the oxygen content in the corundum grinding jar of the sealed planetary ball mill to ≤5%; The ball-to-material mass ratio in the corundum ball mill jar is 5:1-10:1, and the filling rate is 30-50%. The balls used in planetary ball mills are corundum grinding balls with a diameter of 5-10mm; The planetary ball mill has a revolution speed of 200-400 r / min and a rotation speed of 400-800 r / min. The equipment used for continuous mechanical stirring is a top-mounted paddle stirrer or magnetic stirrer, with the stirring speed controlled at 200-400 r / min.

5. The method for recovering silver and aluminum from waste crystalline silicon photovoltaic modules using molten salt according to claim 1, wherein, The duration of the ultrasonic oscillation is 0.5-3 minutes.

6. The method for recovering silver and aluminum from waste crystalline silicon photovoltaic modules using molten salt according to claim 1, wherein, The method also includes silver-aluminum separation: (1) The silver-aluminum mixed solid metal is mixed with an aqueous sodium hydroxide solution, stirred, and filtered to obtain silver wire and an alkaline solution containing sodium aluminate; (2) Wash the silver wire with water; (3) Carbon dioxide is introduced into the alkaline solution containing sodium aluminate until the pH of the solution system is 7.5-8.5, aluminum hydroxide precipitate is generated, and the precipitate is then filtered, washed and calcined to obtain aluminum oxide powder.

7. The method for recovering silver and aluminum from waste crystalline silicon photovoltaic modules using molten salt according to claim 6, wherein, In step (1): The sodium hydroxide aqueous solution has a mass fraction of 16-30 wt%. The liquid-solid mass ratio of the silver-aluminum mixed solid metal to the sodium hydroxide aqueous solution is 2:1-8:1; The stirring temperature is 50-80℃, the stirring speed is 80-120 r / min, and the stirring time is 30-60 min; In step (3): Carbon dioxide is introduced into the alkaline solution containing sodium aluminate at an inlet rate of 0.8-1.5 L / min; The calcination temperature is 900-1200℃, and the time is 1-2 hours.

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