A system for separating and purifying silver and silicon in waste solar silicon wafer

Abstract

The utility model discloses a kind of separation and purification systems of silver and silicon in waste solar silicon wafer, belong to photovoltaic module recycling technical field, system includes silicon wafer processing unit, silver deposition purification unit, waste gas processing unit, wastewater treatment unit and control system.Silicon wafer processing unit contains soaking basket, sulfuric acid tank, nitric acid tank and pure water tank, for removing base metal, dissolving silver and washing silicon wafer;Silver deposition purification unit contains reaction kettle, stirrer, reducing agent dosing device, filtering device and silver ingot equipment, for precipitating, reducing silver nitrate solution and smelting silver ingot.Waste gas processing unit contains lye spray tower and activated carbon adsorption tank, wastewater treatment unit contains heavy metal precipitation tank and silver recovery resin tower.Each unit is connected by pipeline, and control system realizes full-process automation.The system can efficiently separate and purify silver and silicon in waste solar silicon wafer, realize resource recycling, with good environmental protection and economic benefits.

Description

Technical Field

[0001] This utility model relates to the field of photovoltaic module recycling technology, and in particular to a system for separating and purifying silver and silicon in waste solar silicon wafers, which is suitable for industrial-scale batch processing of broken silicon wafers and simultaneous recovery of high-purity silver ingots and silicon powder. Background Technology

[0002] With the rapid development of the photovoltaic industry, the recycling and disposal of waste photovoltaic modules has become an important issue. Among photovoltaic modules, the solar cells (including the silicon substrate and silver paste electrodes) are the core recycling target. Current technologies typically dismantle waste modules into fragmented solar cells or powder through pyrolysis, grinding, and pulverization. However, the subsequent extraction of silver and the recycling of silicon materials still face many technical challenges.

[0003] Currently, the recycling process for used photovoltaic modules faces the following problems:

[0004] Insufficient batch processing capacity: Existing technologies are mostly for laboratory or small-scale processing, relying on manual operation (such as manual soaking and material transfer), making it difficult to achieve continuous and industrialized processing of silicon wafers in the ton range or above.

[0005] Purity control is difficult: Fragmented silicon wafers are often mixed with base metals such as iron, copper, and aluminum, as well as glass fragments. However, the existing washing and reaction processes are not standardized, resulting in low purity of recovered silicon powder (impurity content greater than 1%) and insufficient purity of silver ingots (usually less than 99.5%), which seriously affects the value of secondary utilization.

[0006] Poor equipment adaptability: The particle size of silicon wafer fragments varies greatly (from micron-sized powder to millimeter-sized fragments). The filters of existing equipment are fixed and cannot be adapted to materials of different shapes, which can easily lead to material leakage or blockage.

[0007] Low level of automation: The addition of reaction solution, material transfer, solid-liquid separation and other processes rely on manual intervention, which is not only inefficient (the processing cycle of a single ton of material is more than 48 hours), but also poses a risk of contact with chemical reagents and is not environmentally friendly.

[0008] Therefore, there is an urgent need to develop an integrated and automated industrial production line to solve the above problems, achieve efficient separation of silicon wafers, precise extraction of silver, and high-purity recovery of silicon powder, thereby improving resource utilization and economic benefits. Utility Model Content

[0009] The purpose of this invention is to provide a system for separating and purifying silver and silicon in waste solar silicon wafers, so as to achieve efficient extraction of high-purity silver ingots and high-purity broken solar cells from batches of broken solar cells.

[0010] To achieve the above objectives, this utility model provides the following solution:

[0011] A system for separating and purifying silver and silicon from waste solar silicon wafers includes a silicon wafer processing unit, a silver immersion purification unit, and a control system. The silicon wafer processing unit includes a silicon wafer acid washing device, an immersion basket, and a gantry frame. The silicon wafer acid washing device includes a sulfuric acid tank, a primary pure water tank, a nitric acid tank, and a secondary pure water tank arranged sequentially. Each tank is connected by corrosion-resistant pipes, and automatic valves are installed on the corrosion-resistant pipes. Each tank is equipped with an automatic liquid addition and discharge pump group. The immersion basket is vertically connected to the gantry frame, which travels above each tank. The silver immersion purification unit includes a silver immersion purification chamber, a filtration device, and a silver ingot casting device. The silver immersion purification chamber is equipped with a reaction vessel, a stirrer, and a reducing agent dosing device. The reducing agent dosing device is connected to the reaction vessel via pipeline. The stirrer is fixed above the reaction vessel, and its stirring blades extend into the reaction vessel.

[0012] Furthermore, the basket body of the soaking basket is made of acid and alkali resistant titanium alloy, and filter screens are detachably installed on all four sides and the bottom, with the mesh size of the filter screens ranging from 10 to 200 meshes.

[0013] Furthermore, the silver and silicon separation and purification system for waste solar silicon wafers also includes a waste gas treatment unit, which comprises an alkaline spray tower and an activated carbon adsorption tank to treat NO. X SO2 and volatile organic compounds.

[0014] Furthermore, the silicon wafer acid washing equipment is located in the silicon wafer purification chamber, and the top of the silicon wafer purification chamber and the silver immersion purification chamber are covered with a fully enclosed gas collection hood, which is connected to the waste gas treatment unit through a waste gas collection pipe.

[0015] Furthermore, the system for separating and purifying silver and silicon in waste solar silicon wafers also includes a wastewater treatment unit, which includes a heavy metal precipitation tank and a silver recovery resin tower. Heavy metals are precipitated by adding lime milk and Na2S, and the resin tower adsorbs residual silver ions.

[0016] Compared with the prior art, the present invention discloses at least the following beneficial effects:

[0017] This utility model relates to a system for separating and purifying silver and silicon in waste solar silicon wafers. It can efficiently separate and purify silver and silicon in waste solar silicon wafers, realize resource recycling, and has good environmental protection and economic benefits. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of the silver and silicon separation and purification system for waste solar silicon wafers according to this utility model;

[0020] Figure 2 This is a schematic diagram of the structure of the silicon wafer washing equipment in the separation and purification system of this utility model;

[0021] Figure 3 This is a process flow diagram of the method for separating and purifying silver and silicon in waste solar silicon wafers according to this utility model.

[0022] Figure 4 This is a flowchart of the S2 multi-stage reaction and washing process in the method for separating and purifying silver and silicon from waste solar silicon wafers according to this utility model.

[0023] In the diagram: 1. Silicon wafer purification chamber; 2. Waste gas collection pipe; 3. Two-stage purification system; 4. Pure silicon wafer collection box; 5. Silicon wafer acid washing equipment; 6. Pure water tower; 7. Air compressor unit; 8. Filtration device; 9. Silver ingot casting equipment; 10. Heavy metal precipitation tank; 11. Silver immersion purification chamber; 12. Immersion basket; 13. Gantry frame; 14. Sulfuric acid tank; 15. Primary pure water tank; 16. Corrosion-resistant pipe; 17. Nitric acid tank; 18. Secondary pure water tank; 19. Silver nitrate secondary precious liquid pump set; 20. Silver nitrate solution pump set; 21. Sulfuric acid washing wastewater pump set; 22. Sulfuric acid pretreatment wastewater pump set. Detailed Implementation

[0024] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0025] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Reference Figure 1 and Figure 2 As shown, this embodiment provides a system for separating and purifying silver and silicon in waste solar silicon wafers, including a silicon wafer processing unit, a silver immersion purification unit, a waste gas treatment unit, a wastewater treatment unit, and a control system. The silicon wafer processing unit, the silver immersion purification unit, the waste gas treatment unit, and the wastewater treatment unit are connected in series through pipelines, and the control system is communicatively connected to the other units.

[0027] In this embodiment of the invention, the silicon wafer processing unit includes a silicon wafer pickling device 5, an immersion basket 12, and a gantry frame 13, all located within the silicon wafer purification chamber 1, as well as a belt conveyor, a crushing device, and a drying device. Specifically, the silicon wafer pickling device 5 adopts a multi-stage reaction tank structure, including four chemical reaction tanks connected in series: a sulfuric acid tank 14, a primary pure water tank 15, a nitric acid tank 17, and a secondary pure water tank 18. The sulfuric acid tank 14 and the nitric acid tank 17 are connected by corrosion-resistant pipes 16, with automatic valves installed on the pipes. Each tank is equipped with an automatic liquid addition and drainage pump group. The chemical reaction tanks, made of titanium alloy, are resistant to strong acid corrosion. Through the pipes and automatic valves at the bottom of the tanks, the flow of the reaction liquid to the wastewater treatment unit or its recycling can be controlled. The automatic liquid addition and drainage pump groups enable fully automatic liquid replenishment, drainage, and multiple cyclic immersion, improving processing efficiency and automation. The gantry frame 13 has a traveling mechanism at its bottom, which travels above the chemical reaction tanks. The immersion basket 12 has a lifting ring at its top, connecting to the gantry for automatic transfer.

[0028] In one specific embodiment, the top of the soaking basket 12 is equipped with a dedicated lifting ring (made of acid and alkali resistant titanium alloy), which is directly connected to the overhead crane hook of the gantry frame via a mechanical lock, achieving stable load transfer and 360° rotation transport. The gantry frame 13 is a U-shaped truss structure, including two vertical gantry frames and a crossbeam. Vertical slide rails are provided on the inner sides of the two vertical gantry frames. Guide shoe rollers or sliders are installed on the side walls of the soaking basket 12 and embedded in the guide rails to ensure no skewing during the lifting process. The soaking basket 12 is connected to the lifting mechanism via the dedicated lifting ring. The lifting mechanism is connected to the middle of the crossbeam of the gantry frame 13 and includes an electric winch and a lifting chain or wire rope. One end of the lifting chain or wire rope is fixed to a drum, and the other end is connected to the dedicated lifting ring. The electric winch controls the torque output through a reducer. The loaded soaking basket 12 is automatically transferred between the four chemical reaction tanks via the gantry frame 13 with the above-described structure.

[0029] In one specific embodiment, the soaking basket 12 is made of acid and alkali resistant titanium alloy to avoid chemical reaction with the reaction solution. Replaceable filters are provided around the basket and at the bottom. The mesh size of the filters is between 10 and 200 to accommodate silicon silver materials of different particle sizes. For example, a 10-mesh filter is used to process millimeter-sized fragments, and a 200-mesh filter is used to process micron-sized powders.

[0030] In one specific embodiment, the four tanks—sulfuric acid tank 14, primary pure water tank 15, nitric acid tank 17, and secondary pure water tank 18—are all made of titanium alloy, which is resistant to strong acid corrosion. The volume of a single tank can be customized from 1 to 5 m³. 3 Each tank is equipped with an automatic liquid addition and drainage pump set, which can preset the liquid addition volume and reaction time to achieve fully automatic liquid replenishment, drainage, and multiple cyclic soaking. Figure 2As shown, sulfuric acid tank 14 is externally connected to sulfuric acid pretreatment wastewater pump group 22, primary pure water tank 15 is externally connected to sulfuric acid washing wastewater pump group 21, nitric acid tank 17 is externally connected to silver nitrate solution pump group 20, and secondary pure water tank 18 is externally connected to silver nitrate secondary precious solution pump group 19. Sulfuric acid pretreatment wastewater pump group 22 is used to automatically add 5%–20% dilute sulfuric acid solution to sulfuric acid tank 14 during the base metal removal stage and to discharge wastewater containing base metal sulfates after the reaction. The sulfuric acid washing wastewater pump set 21 is used to inject pure water into the primary pure water tank 15 during the primary washing stage to wash away residual acid, and to discharge wastewater containing sulfate / acid residue; the silver nitrate solution pump set 20 is used to inject 10% to 30% dilute nitric acid solution into the nitric acid tank 17 during the silver dissolution / precious solution collection stage, and to pump the silver nitrate solution after silver dissolution to the silver precipitation purification chamber 11; the silver nitrate secondary precious solution pump set 19 is used to inject pure water into the secondary pure water tank 18 for final washing during the deep washing / precious solution recovery stage, and to collect the washing water containing trace amounts of silver and recycle it to the nitric acid tank 17 for reuse.

[0031] In one specific embodiment, a belt conveyor is located behind the secondary pure water tank 18 to receive the crushed silicon wafers after secondary washing, transport them to the external pure silicon wafer collection box 4, and then transfer them to the crushing area and drying area via forklifts or other transfer machinery.

[0032] In this embodiment of the present invention, the silver immersion purification unit includes a reaction vessel, a stirrer and a reducing agent dosing device disposed in the silver immersion purification chamber 11, as well as a filter device 8 and a silver ingot casting equipment 9 located outside the silver immersion purification chamber 11.

[0033] In one specific embodiment, the reactor adopts a titanium alloy liner + 316L stainless steel composite structure, with a volume of 1-5m³. 3 Customizable, resistant to silver nitrate corrosion, used for the precipitation and reduction of silver nitrate solutions. A stirrer with a mechanical seal is installed on top of the reactor, with an adjustable speed of 50-200 rpm. The stirring blades extend deep into the reactor and are made of PTFE-coated titanium alloy to prevent metal contamination. The reactor integrates a temperature sensor (PT100 type) and a pH online monitoring probe, transmitting data to the control system in real time. In this embodiment, the reactor receives the precious silver nitrate solution pumped from nitric acid tank 17, and is prepared according to a preset ratio (e.g., Cl-:Ag). + Adding sodium chloride solution at a ratio of 1.1:1 produces silver chloride precipitate. In practical applications, the reaction conditions are controlled as follows: temperature 20–40℃, pH 3–4, stirring speed 80 rpm, and reaction time 1–2 hours.

[0034] In one specific embodiment, the reducing agent dosing device employs a dual-tank design, including a main tank and a backup tank. For example, the main tank can store hydrazine hydrate solution (80% concentration), and the backup tank can store glucose solution (40% concentration), supporting the switching of different reducing agents. A diaphragm metering pump is installed on the pipeline connecting the reducing agent dosing device to the reactor. The flow rate error of the diaphragm metering pump is ±1%, and the dosing amount is controlled by the control system. In practical applications, the reducing agent is quantitatively injected into the silver chloride precipitate in the reactor, and the reaction is carried out at 60–80°C for 2–3 hours to generate elemental silver powder. It is important to periodically and automatically clean the pipeline to prevent crystallization and blockage.

[0035] In one specific embodiment, the reducing agent added to the reactor can be one or more of hydrazine hydrate, glucose, zinc wire, and vitamin C.

[0036] In one specific embodiment, the filter device 8 is connected to the outlet end of the reactor and receives the slurry (silver chloride precipitate or silver powder mixture) discharged from the reactor through a pipeline. It is used to separate the silver chloride precipitate (precipitation stage) or elemental silver powder (reduction stage) from the liquid phase. The outlet end of the filter device 8 is connected to a wastewater treatment unit. The filter device 8 can be a plate filter press, with the filter plates made of reinforced polypropylene (PP) and a filtration area of ​​10–50 m². 2 It has a pressure resistance of 0.6MPa, a hollow filter plate design, supports backwashing with washing water, and a residual impurity removal rate of >99%.

[0037] In one specific embodiment, the silver ingot casting equipment 9 receives silver powder from the filter device 8, mixes it with borax (0.5%–1%), and loads it into a graphite crucible. After melting, it is cast and cooled to obtain silver ingots. The silver ingot casting equipment 9 includes a medium-frequency induction furnace, a graphite crucible, and a borax feeder. The medium-frequency induction furnace has a power of 50–200 kW, a frequency of 1000–2500 Hz, and a temperature control accuracy of ±5℃. The graphite crucible has a purity ≥99.9% and a volume of 5–20 L, and is equipped with an automatic casting robot. The borax feeder uses vibratory feeding, adding borax at 0.5%–1% of the silver powder weight. In practical applications, the silver powder and borax are mixed and melted, with temperature gradient control: 600℃ to remove volatiles → 1000℃ to melt → 1100℃ to hold for impurity removal, and then cast into 15 kg standard silver ingots (purity ≥99.9%), with batch numbers laser-engraved on the surface.

[0038] In one specific embodiment, the system of this utility model further includes a pure water tower 6, which is connected to a filter device 8 to provide pure water for the washing stage in the silver ingot extraction process. This pure water is used to wash the reduced elemental silver powder, bringing it to neutral and ensuring the purity and quality of the silver ingot. The stable water supply from the pure water tower 6 ensures the washing effect of the entire separation and purification process, effectively removing impurities and improving the purity of the silver ingot. Simultaneously, the pure water tower 6 can also provide high-purity pure water to the silicon wafer acid washing equipment 5 for various washing steps. The pure water tower 6 utilizes advanced water treatment technologies, such as reverse osmosis and ion exchange, to ensure that the produced pure water meets process requirements, has low conductivity, and minimal impurities. In the preliminary washing step, the pure water tower 6 supplies pure water to the primary pure water tank 15 to wash away residual sulfuric acid and soluble salts on the surface of the broken silicon wafers in the soaking basket 12. In the secondary washing step, the pure water tower 6 supplies pure water to the secondary pure water tank 18, washing the silicon wafers multiple times until the pH of the washing water is close to neutral, ensuring that there is no nitric acid residue on the silicon wafers.

[0039] In one specific embodiment, the system of this utility model further includes an air compressor unit 7, which is mainly used to provide power support to realize automatic material transfer and normal equipment operation. During the material loading stage, the compressed air generated by the air compressor unit 7 can be used to drive the pneumatic device of the gantry frame 13, realizing the precise lifting and transfer of the soaking basket 12, accurately delivering the soaking basket 12 containing silicon wafer fragments into each reaction tank. During the multi-stage reaction and washing process, the air compressor unit 7 provides power to the stirring device in the reaction tank, driving the stirrer with compressed air to fully mix the reaction liquid and materials, accelerating the chemical reaction and improving reaction efficiency and uniformity. In addition, the air compressor unit 7 can also provide an air source for the filtration device 8, used to purge the filter cake during the filtration process, improving the filtration effect and the dryness of the filter cake. In the smelting stage of silver ingot extraction, the air compressor unit 7 can provide compressed air to the cooling system of the medium-frequency furnace to cool the furnace body, ensuring the stable operation of the smelting process and extending the service life of the equipment. With the stable air supply from air compressor unit 7, the entire separation and purification system is automated and the equipment operates efficiently, improving production efficiency and safety.

[0040] In this embodiment of the invention, the waste gas treatment unit includes a negative pressure collection system and a two-stage purification system 3. The negative pressure collection system includes a fully enclosed gas collection hood covering the top of the reaction vessel and the silicon wafer pickling equipment 5, as well as a waste gas collection pipe 2 and a centrifugal fan located above the fully enclosed gas collection hood. The waste gas collection pipe 2 can be made of fiberglass, which is resistant to acid and alkali corrosion. The centrifugal fan maintains the negative pressure of the system to ensure that the waste gas does not escape. The two-stage purification system 3 includes a primary alkaline spray tower and a secondary activated carbon adsorption tank.

[0041] In one specific embodiment, the primary alkaline spray tower adopts... The tower body is made of fiberglass reinforced plastic (FRP) and filled with PP Pall ring packing. The spray solution is a 10% NaOH solution with a circulation flow rate of 5 m³ / h. 3 / h, neutralize NO X Acidic gases such as SO2.

[0042] In one specific embodiment, the secondary activated carbon adsorption tank is equipped with a double-layer honeycomb activated carbon filter bed with a thickness of about 0.5m, which adsorbs hydrazine vapor and volatile organic compounds, and the clogging status is monitored by a differential pressure sensor.

[0043] In one specific embodiment, an online monitoring instrument is installed on the exhaust pipe of the exhaust gas treatment unit, for example, measuring NO with a range of 0-500 ppm. X Sensors. It should be understood that in practical applications, monitoring thresholds are set according to established emission standards, for example, NO... X Concentration ≤100mg / m 3 Particulate matter ≤20mg / m³ 3 .

[0044] In this embodiment of the invention, the wastewater treatment unit includes a heavy metal precipitation tank 10, a silver recovery resin tower, and a reverse osmosis module. The heavy metal precipitation tank 10 adopts a combined structure of a reaction tank and an inclined plate sedimentation tank. Lime slurry (Ca(OH)2) and Na2S solution are added to the tank, and the pH is controlled to be 9-10 to precipitate heavy metal sulfides. The silver recovery resin tower is loaded with thiol-based chelating resin (exchange capacity ≥2.0 mmol / g), with an adsorption flow rate of 2 BV / h. After saturation, it is desorbed with 5% HNO3, and the enriched solution is returned to the nitric acid tank 17 for recycling. The reverse osmosis module has a built-in spiral wound RO membrane (desalination rate ≥98%). The permeate is reused in the pure water tank, and the concentrate enters the evaporator crystallizer.

[0045] In practical applications, sulfates containing base metals such as iron, copper, and aluminum (concentration 200–500 mg / L) are collected in heavy metal precipitation tank 10. The pH is adjusted to 9–10 by adding lime slurry (Ca(OH)2) and sodium sulfide (Na2S), generating heavy metal sulfide precipitates. After separation in an inclined plate sedimentation tank, the sludge is dewatered by a plate and frame filter press (moisture content ≤60%), and the hazardous waste is sent to a specialized treatment center. Waste containing residual sulfuric acid and salts (pH = 1.5–2.5) is neutralized in a pH adjustment tank, then suspended solids are removed in a coagulation sedimentation tank (SS ≤ 50 mg / L), followed by deep treatment through a reverse osmosis membrane unit (desalination rate ≥ 98%). The permeate is reused in a pure water tank (reuse rate ≥ 70%), and the concentrated water undergoes solidification treatment in an evaporator crystallizer. Waste containing trace amounts of silver ions (5–50 mg / L) is pumped into a silver recovery resin tower. The tower is loaded with thiol-based chelating resin (exchange capacity ≥2.0 mmol / g). After adsorbing silver ions, it is desorbed with 5% nitric acid. The enriched solution is returned to the nitric acid tank 17 for recycling, achieving zero waste of silver resources.

[0046] In this embodiment of the utility model, the control system integrates a PLC, a human-machine interface (HMI), and sensors (liquid level, temperature, pH value) to control parameters such as the transfer sequence of the soaking basket 12, the start and stop of the pump group, the valve opening and closing, and the reaction time, so as to realize unmanned operation of the entire process.

[0047] Reference Figure 3 and Figure 4 As shown, this embodiment also provides a method for separating and purifying silver and silicon in waste solar silicon wafers. Using the silver and silicon separation and purification system for waste solar silicon wafers described in the above embodiment, the method includes the following steps:

[0048] S1. Material loading:

[0049] A ton-sized batch of crushed silicon wafers (containing silver) is loaded into the soaking basket 12, and a filter screen with a matching mesh size is selected according to the particle size of the material. For example, a 20-mesh filter screen can be used for fragments of 1–5 mm; a 100-mesh filter screen can be used for powder smaller than 1 mm. The titanium soaking basket 12 is made of acid and alkali resistant titanium alloy to avoid chemical reaction with the reaction solution. Replaceable filter screens are installed around the basket and at the bottom, and a lifting ring is provided at the top to connect to the gantry frame 13 for automatic transfer.

[0050] S2, multi-stage reaction and washing:

[0051] S201, Base metal removal: The soaking basket 12 is transferred from the gantry frame 13 to the sulfuric acid tank 14. 5% to 20% dilute sulfuric acid is added through the automatic pump group, and the soaking time is 2 to 4 hours (temperature 20 to 50℃) to remove base metals such as iron, copper, and aluminum (the reaction generates sulfate solution). The solution in the sulfuric acid tank 14 is sent to the nitric acid tank 17 through the inter-tank connecting valve.

[0052] S202, Preliminary washing: The soaking basket 12 is transferred to the primary pure water tank 15, and pure water is injected by the pump unit. Soak for 30-60 minutes to wash away residual sulfuric acid and soluble salts. The wastewater is discharged through the bottom pipe.

[0053] S203, silver dissolution: Transfer the soaking basket 12 to the nitric acid tank 17, add 10% to 30% dilute nitric acid by the pump group, soak for 3 to 6 hours (temperature 30 to 60℃), the elemental silver reacts to form silver nitrate solution (precious solution), the silicon wafer does not dissolve and remains in the basket;

[0054] S204. Secondary washing: Transfer the soaking basket 12 to the secondary pure water tank 18, and wash with pure water multiple times (2 to 3 times) until the pH value of the washing water is close to neutral (6 to 7) to ensure that there is no nitric acid residue on the silicon wafer.

[0055] S3, Silicon Wafer Recycling:

[0056] The pure silicon wafers in the soaking basket 12 are fed into the drying equipment by a belt conveyor. After drying (moisture content <0.5%), they are collected, packaged, and crushed into silicon powder by a crushing equipment and sold as pure silicon powder.

[0057] S4. Silver ingot extraction:

[0058] S401, Silver precipitation: Silver nitrate solution is pumped to the reactor, sodium chloride solution is added in proportion, stirred to generate white silver chloride precipitate, and filtered after standing.

[0059] S402, Reduction: Add a strong reducing agent to silver chloride precipitate, react to produce elemental silver powder, filter and wash until neutral;

[0060] S403, Smelting: Elemental silver powder is placed in a graphite crucible, a small amount of borax is added (for impurity removal and melting), and heated in a medium-frequency furnace to 1000-1100℃ to melt. After cooling, silver ingots with a purity ≥99.9% are obtained.

[0061] S5, Cyclic Control:

[0062] Each step is linked through the control system. For example, the reaction time and liquid addition amount of sulfuric acid tank 14 and nitric acid tank 17 are automatically adjusted according to the amount of material. In the silver precipitation process, the amount of reducing agent added is matched with the concentration of silver nitrate in real time to ensure that the reaction is complete.

[0063] The silver and silicon separation and purification system disclosed in the above embodiments integrates multiple functional units to achieve efficient and environmentally friendly separation and purification of silver and silicon from waste solar silicon wafers. The immersion basket 12 in the silicon wafer processing unit is made of acid and alkali resistant titanium alloy and equipped with a detachable filter screen, adaptable to silicon wafer materials of different particle sizes, effectively avoiding leakage or clogging problems, and improving the flexibility and adaptability of material processing. The sulfuric acid tank 14 and nitric acid tank 17 are used to remove base metals and dissolve silver. Their automated liquid addition and discharge pump sets can precisely control the addition and discharge of reaction solutions, ensuring the stability and consistency of reaction conditions, thereby improving the recovery efficiency and purity of silver and silicon. In the silver precipitation purification unit, the reaction vessel, stirrer, and reducing agent dosing device work together to achieve the precipitation and reduction of silver nitrate solution and the generation of silver powder. Temperature sensors and pH online monitoring probes inside the reaction vessel monitor the reaction process in real time, ensuring precise control of reaction conditions and further improving the purity of silver recovery. The waste gas treatment unit and wastewater treatment unit effectively treat waste gas and wastewater respectively, reducing environmental pollution and meeting environmental protection requirements. Simultaneously, the wastewater treatment unit enables water resource recycling, reducing production costs. The entire system is automated by a control system, achieving fully unmanned operation, improving production efficiency, reducing labor costs, and minimizing the risk of chemical reagent contact, thus enhancing operational safety. The purification method, through its unique structural design and process flow, achieves efficient, environmentally friendly, and high-purity silver-silicon separation and purification. The collaborative work of each unit in the system automates and continuously purifies the entire process, significantly improving processing efficiency and capacity. In summary, the structural and methodological innovations of this invention not only solve the problems of insufficient batch processing capacity, difficulty in purity control, poor equipment adaptability, and low automation in existing technologies, but also improve production efficiency, reduce labor costs, and enhance resource utilization and economic benefits through full-process automated control, providing an efficient, environmentally friendly, and economical solution for the recycling and processing of waste solar silicon wafers.

[0064] In the description of this utility model, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0065] The embodiments described above are merely preferred embodiments of the present utility model and are not intended to limit the scope of the present utility model. Various modifications and improvements made to the technical solutions of the present utility model by those skilled in the art without departing from the spirit of the present utility model should fall within the protection scope defined by the claims of the present utility model.

Claims

1. A system for separating and purifying silver and silicon from waste solar silicon wafers, characterized in that, The system includes a silicon wafer processing unit, a silver immersion purification unit, and a control system. The silicon wafer processing unit includes a silicon wafer pickling equipment (5), an immersion basket (12), and a gantry frame (13). The silicon wafer pickling equipment (5) includes a sulfuric acid tank (14), a primary pure water tank (15), a nitric acid tank (17), and a secondary pure water tank (18) arranged sequentially. Each tank is connected by a corrosion-resistant pipe (16), and an automatic valve is provided on the corrosion-resistant pipe (16). Each tank is equipped with an automatic liquid filling and draining system. Liquid pump assembly; the soaking basket (12) can be lifted and connected to the gantry frame (13), the gantry frame (13) travels above each tank; the silver immersion purification unit includes a silver immersion purification chamber (11), a filter device (8) and a silver ingot casting device (9), the silver immersion purification chamber (11) is equipped with a reaction vessel, a stirrer and a reducing agent dosing device, the reducing agent dosing device is connected to the reaction vessel pipeline, the stirrer is fixed above the reaction vessel and its stirring blades extend into the reaction vessel.

2. The system for separating and purifying silver and silicon in waste solar silicon wafers according to claim 1, characterized in that, The soaking basket (12) is made of acid and alkali resistant titanium alloy, and a filter screen is detachably installed on all four sides and the bottom. The mesh size of the filter screen ranges from 10 mesh to 200 mesh.

3. The system for separating and purifying silver and silicon in waste solar silicon wafers according to claim 1, characterized in that, It also includes a waste gas treatment unit, which comprises an alkaline spray tower and an activated carbon adsorption tank, for treating NO. X SO2 and volatile organic compounds.

4. The system for separating and purifying silver and silicon in waste solar silicon wafers according to claim 3, characterized in that, The silicon wafer pickling equipment (5) is located in the silicon wafer purification chamber (1). The top of the silicon wafer purification chamber (1) and the silver immersion purification chamber (11) are covered with a fully enclosed gas collection hood and connected to the waste gas treatment unit through the waste gas collection pipe (2).

5. The system for separating and purifying silver and silicon in waste solar silicon wafers according to claim 1, characterized in that, It also includes a wastewater treatment unit, which includes a heavy metal precipitation tank (10) and a silver recovery resin tower. Heavy metals are precipitated by adding lime milk and Na2S, and the resin tower adsorbs residual silver ions.

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