Separation and purification system and method for silver and silicon in waste solar silicon wafer

Abstract

The invention discloses a system and a method for separating and purifying silver and silicon in a waste solar silicon wafer, and belongs to the technical field of photovoltaic module recovery, and the system comprises a silicon wafer treatment unit, a silver deposition purification unit, a waste gas treatment unit, a wastewater treatment unit and a control system. The silicon wafer processing unit comprises a soaking basket, a sulfuric acid tank, a nitric acid tank and a pure water tank and is used for removing base metals, dissolving silver and washing silicon wafers; the silver precipitation and purification unit comprises a reaction kettle, a stirrer, a reducing agent adding device, a filtering device and silver ingot casting equipment and is used for precipitating and reducing a silver nitrate solution and smelting silver ingots. The waste gas treatment unit comprises an alkali liquor spray tower and an activated carbon adsorption tank, and the wastewater treatment unit comprises a heavy metal sedimentation tank and a silver recovery resin tower. All the units are connected in series through pipelines, and the control system achieves full-process automation. The system can efficiently separate and purify silver and silicon in the waste solar silicon wafer, realizes resource recycling, and has good environmental protection property and economic benefit.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic module recycling, and particularly relates to a system and method for separating and purifying silver and silicon from waste solar silicon wafers, which is suitable for industrialized batch processing of broken silicon wafers and simultaneously recycling high-purity silver ingots and silicon powder. BACKGROUND

[0002] With the rapid development of the photovoltaic industry, the recycling of waste photovoltaic modules has become an important issue. In photovoltaic modules, cell pieces (containing silicon substrates and silver paste electrodes) are the core recycling objects. The existing technology usually disassembles waste modules into broken cell pieces or broken cell powder through pyrolysis, grinding and other means, but the subsequent extraction of silver elements and recycling of silicon materials still face many technical challenges.

[0003] Currently, the recycling process of waste photovoltaic modules has the following problems:

[0004] Insufficient batch processing capacity: the existing technology is mostly for laboratory or small-scale processing, relying on manual operation (such as manual soaking and transferring materials), making it difficult to achieve continuous and industrialized processing of tons of broken silicon wafers.

[0005] Difficulty in controlling purity: broken silicon wafers often contain base metals such as iron, copper and aluminum, as well as glass debris, and the existing washing and reaction process is not standardized, resulting in low purity of the recycled silicon powder (impurity content greater than 1%) and insufficient purity of the silver ingots (usually less than 99.5%), which seriously affects the secondary utilization value.

[0006] Poor equipment adaptability: the particle size of broken silicon wafers varies greatly (from micron-level powder to millimeter-level fragments), and the filter screen of existing equipment is fixed, which cannot adapt to different forms of materials, and is prone to leakage or clogging problems.

[0007] Low degree of automation: the addition of reaction liquid, the transfer of materials, and the separation of solid and liquid rely on manual intervention, which not only has low efficiency (the processing period of a single ton of material is more than 48 hours), but also has the risk of chemical reagent contact, and has poor environmental protection.

[0008] Therefore, it is urgent to develop an integrated and automated industrial production line to solve the above problems and achieve efficient separation of broken silicon wafers, precise extraction of silver, and high-purity recycling of silicon powder, thereby improving resource utilization and economic efficiency. SUMMARY

[0009] The purpose of the present application is to provide a system and method for separating and purifying silver and silicon from waste solar silicon wafers, which can efficiently extract high-purity silver ingots and high-purity broken cell pieces from batch broken cell pieces.

[0010] To achieve the above purpose, the present application provides the following solutions:

[0011] The utility model provides a kind of silver and silicon separation and purification system in waste solar silicon wafer, including silicon wafer processing unit, silver deposition purification unit and control system;The silicon wafer processing unit includes silicon wafer pickling equipment, soaking basket and gantry carriage, the silicon wafer pickling equipment includes the sulfuric acid tank, primary water tank, nitric acid tank and secondary water tank arranged successively, each tank body is communicated by corrosion-resistant pipeline, and automatic valve is equipped on corrosion-resistant pipeline, and each tank body is configured with automatic liquid adding and discharging pump group;The soaking basket can be lifted and is connected on the gantry carriage, and the gantry carriage walks above each tank body;The silver deposition purification unit includes silver deposition purification chamber, filter device and silver ingot equipment, reaction kettle, agitator and reducing agent adding device are arranged in the silver deposition purification chamber, the reducing agent adding device is connected with the pipeline of reaction kettle, and the agitator is fixed on the top of reaction kettle, and its stirring paddle is inserted into reaction kettle.

[0012] Further, the basket body of the soaking basket is made of acid and alkali resistant titanium alloy material, and a filter screen is detachably mounted on the periphery and the bottom of the basket body, and the mesh size of the filter screen ranges from 10 mesh to 200 mesh.

[0013] Further, the silver and silicon separation and purification system in waste solar silicon wafer further includes a waste gas treatment unit, the waste gas treatment unit includes an alkali liquor spray tower and an activated carbon adsorption tank, and NO X , SO2 and organic volatile substances are treated.

[0014] Further, the silicon wafer pickling equipment is arranged in a silicon wafer purification chamber, and the top of the silicon wafer purification chamber and the silver deposition purification chamber is covered with a full-closed gas collecting hood, and the waste gas collecting pipe is connected to the waste gas treatment unit.

[0015] Further, the silver and silicon separation and purification system in waste solar silicon wafer further includes a waste water treatment unit, the waste water treatment unit includes a heavy metal precipitation tank and a silver recovery resin tower, and the heavy metals are precipitated by adding lime milk and Na2S, and the residual silver ions are adsorbed by the resin tower.

[0016] A method for separating and purifying silver and silicon in waste solar silicon wafer, using the silver and silicon separation and purification system in waste solar silicon wafer according to any one of the above, the method comprising the following steps:

[0017] Step S1, loading the broken battery pieces into the soaking basket and selecting a matching filter screen to obtain a loaded material;

[0018] Step S2, removing the base metals in the sulfuric acid tank and performing preliminary washing to obtain a silicon-silver material after preliminary washing;

[0019] Step S3, dissolving silver in the nitric acid tank to obtain a silver nitrate solution and a pure silicon wafer;

[0020] Step S4, the pure silicon wafer is washed with pure water and dried to obtain pure silicon powder;

[0021] Step S5, the silver nitrate solution is precipitated, reduced and smelted to obtain silver ingot.

[0022] Further, in step S2, the reaction conditions for removing base metals in the sulfuric acid tank are 5% to 20% dilute sulfuric acid soaking for 2 to 4 hours, and the temperature is 20 to 50°C.

[0023] Further, in step S3, the reaction conditions for dissolving silver in the nitric acid tank are 10% to 30% dilute nitric acid soaking for 3 to 6 hours, and the temperature is 30 to 60°C.

[0024] Further, in step S5, a reducing agent is added to the silver nitrate solution to generate elemental silver powder, and the reducing agent is one or more of hydrazine hydrate, glucose, zinc wire and vitamin C.

[0025] Further, in step S5, 0.5% to 1% borax is added to the silver ingot casting equipment for smelting treatment, and the smelting temperature is 1000 to 1100°C.

[0026] Compared with the prior art, the present application at least discloses the following beneficial effects:

[0027] The silver and silicon separation and purification system for waste solar silicon wafers can efficiently separate and purify silver and silicon in waste solar silicon wafers, realize resource recycling, and has good environmental protection and economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0029] Figure 1 The structure diagram of the silver and silicon separation and purification system for waste solar silicon wafers of the present application;

[0030] Figure 2 The structure diagram of the acid washing equipment for broken silicon wafers in the separation and purification system of the present application;

[0031] Figure 3 The process flow chart of the silver and silicon separation and purification method for waste solar silicon wafers of the present application;

[0032] Figure 4The flow chart of S2 multistage reaction and washing in the method for separating and purifying silver and silicon in waste solar silicon wafer.

[0033] In the figure: 1, silicon wafer purification chamber; 2, waste gas collection pipe; 3, two-stage purification system; 4, pure silicon wafer collection box; 5, silicon wafer pickling equipment; 6, pure water tower; 7, air compressor unit; 8, filtering device; 9, silver ingot equipment; 10, heavy metal precipitation tank; 11, silver precipitation purification chamber; 12, soaking basket; 13, gantry frame; 14, sulfuric acid tank; 15, first-stage pure water tank; 16, corrosion-resistant pipeline; 17, nitric acid tank; 18, second-stage pure water tank; 19, silver nitrate secondary noble liquid pump set; 20, silver nitrate solution pump set; 21, sulfuric acid washing wastewater pump set; 22, sulfuric acid pretreatment wastewater pump set. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0035] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Referring to Figure 1 and Figure 2 The present embodiment provides a system for separating and purifying silver and silicon in waste solar silicon wafer, which comprises a silicon wafer processing unit, a silver precipitation purification unit, a waste gas processing unit, a wastewater processing unit and a control system. The silicon wafer processing unit, the silver precipitation purification unit, the waste gas processing unit and the wastewater processing unit are connected in series through pipelines, and the control system is in communication connection with the other units.

[0037] In the embodiment of the present application, the silicon wafer processing unit includes a silicon wafer pickling device 5, a soaking basket 12 and a gantry frame 13 arranged in the silicon wafer purification chamber 1, and 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, namely a sulfuric acid tank 14, a first-stage pure water tank 15, a nitric acid tank 17 and a second-stage pure water tank 18. The sulfuric acid tank 14 and the nitric acid tank 17 are connected through a corrosion-resistant pipeline 16, and an automatic valve is installed on the pipeline. An automatic liquid feeding and discharging pump set is arranged in each tank body. The chemical reaction tank is made of titanium alloy material and can resist strong acid corrosion. Through the pipeline connected to the bottom of the tank body and the automatic valve, the reaction liquid can be controlled to flow to the wastewater treatment unit or be recycled. Through the automatic liquid feeding and discharging pump set, automatic liquid feeding, discharging and multiple cycle soaking are realized, and the processing efficiency and automation degree are improved. The gantry frame 13 is provided with a walking mechanism at the bottom and walks above the chemical reaction tank. The soaking basket 12 is provided with a lifting ring at the top and is connected with the gantry to realize automatic transfer.

[0038] In a specific embodiment, the top of the soaking basket 12 is provided with a special lifting ring (made of acid and alkali resistant titanium alloy), which is directly connected with the crane hook of the gantry frame through mechanical lock buckle, to realize stable load transmission and 360° rotary transfer function. The gantry frame 13 is a type of truss structure, including two vertical gantry frames and a cross beam. Vertical sliding rails are arranged on the inner sides of the two vertical gantry frames. The side wall of the soaking basket 12 is provided with guide shoe rollers or sliding blocks embedded in the sliding rails, to ensure no deflection during lifting. The soaking basket 12 is connected with the lifting mechanism through the special lifting ring. The lifting mechanism is connected in the middle of the cross beam of the gantry frame 13 and includes an electric hoist, a lifting chain or a steel wire rope, and a special lifting ring. One end of the lifting chain or the steel wire rope is fixed with a winding drum, and the other end is connected with the special lifting ring. The electric hoist controls the torque output through a speed reducer. The loaded soaking basket 12 is automatically transferred between the four chemical reaction tanks through the gantry frame 13 with the above structure.

[0039] In a specific embodiment, the soaking basket 12 is made of acid and alkali resistant titanium alloy to avoid chemical reaction with the reaction liquid. Replaceable filter screens are arranged on the periphery and the bottom of the basket body, and the mesh number of the filter screens is between 10 and 200, to adapt to silicon silver materials with different particle sizes. For example, 10-mesh filter screens are used for processing millimeter-level fragments, and 200-mesh filter screens are used for processing micron-level powders.

[0040] In a specific embodiment, the materials of the four tank bodies of the sulfuric acid tank 14, the first-stage pure water tank 15, the nitric acid tank 17 and the second-stage pure water tank 18 are titanium alloy resistant to strong acid corrosion. The single-tank volume can be customized to be 1-5 m 3 Each tank body is provided with an automatic liquid feeding and discharging pump set, which can preset the liquid feeding amount and reaction time, realize automatic liquid feeding, discharging and multiple cycle soaking. Figure 2As shown, the sulfuric acid tank 14 is connected to the sulfuric acid pretreatment wastewater pump set 22, the first-stage pure water tank 15 is connected to the sulfuric acid washing wastewater pump set 21, the nitric acid tank 17 is connected to the silver nitrate solution pump set 20, and the second-stage pure water tank 18 is connected to the silver nitrate secondary noble liquid pump set 19. The sulfuric acid pretreatment wastewater pump set 22 is used to automatically add 5% to 20% dilute sulfuric acid solution to the sulfuric acid tank 14 in the base metal removal stage and to discharge the base metal-containing sulfuric acid salt wastewater after the reaction. The sulfuric acid washing wastewater pump set 21 is used to inject pure water to wash the residual acid liquid in the first-stage pure water tank 15 in the primary washing stage and to discharge the sulfuric acid salt / acid residual-containing wastewater. The silver nitrate solution pump set 20 is used to inject 10% to 30% dilute nitric acid solution to the nitric acid tank 17 in the silver dissolution / noble liquid collection stage and to pump the silver nitrate solution after the silver is dissolved to the silver deposition purification chamber 11. The silver nitrate secondary noble liquid pump set 19 is used to inject pure water to the second-stage pure water tank 18 for final washing in the deep washing / noble liquid recovery stage and to collect the washing water containing trace silver and recycle it to the nitric acid tank 17 for reuse.

[0041] In a specific embodiment, a belt conveyor is arranged behind the second-stage pure water tank 18 to receive the crushed silicon wafers after the secondary washing, convey them to an external pure silicon wafer collection box 4, and transfer them to the crushing area and the drying area by a forklift or other transfer machinery.

[0042] In the embodiment of the present application, the silver deposition purification unit includes a reaction kettle, a stirrer, and a reducing agent feeding device arranged in the silver deposition purification chamber 11, and a filter device 8 and a silver ingot casting device 9 arranged outside the silver deposition purification chamber 11.

[0043] In a specific embodiment, the reaction kettle adopts a titanium alloy lining + 316L stainless steel composite structure, has a volume of 1 to 5 m 3 It can be customized and is resistant to silver nitrate corrosion and is used for the precipitation and reduction of silver nitrate solution. The reaction kettle is provided with a stirrer at the top, the stirrer adopts a mechanical seal, has a rotating speed of 50 to 200 rpm, and the stirring paddle is made of polytetrafluoroethylene-coated titanium alloy material to avoid metal contamination. The reaction kettle is integrated with a temperature sensor (PT100 type) and a pH online monitoring probe to transmit data to the control system in real time. In the embodiment, the reaction kettle receives the silver nitrate noble liquid pumped from the nitric acid tank 17, adds sodium chloride solution according to a preset ratio (for example, Cl-:Ag + = 1.1:1), and generates silver chloride precipitation. In actual application, the reaction conditions are controlled as follows: temperature 20 to 40℃, pH = 3 to 4, stirring speed 80 rpm, and reaction time 1 to 2 hours.

[0044] In one embodiment, the reducing agent feeding device adopts a double-tank design, including a main tank and a standby tank, for example, the main tank can store hydrazine hydrate solution (concentration 80%), and the standby tank can store glucose solution (concentration 40%), supporting switching of different reducing agents. A diaphragm metering pump is installed on the pipeline connecting the reducing agent feeding device and the reactor, the flow error of the diaphragm metering pump is ±1%, and the feeding amount is controlled by the control system. In actual application, the reducing agent is quantitatively injected into the silver chloride precipitate in the reactor, and the elemental silver powder is generated after reacting at 60-80°C for 2-3 hours. It is noted that the pipeline is periodically automatically cleaned to prevent crystallization blockage.

[0045] In one embodiment, the reducing agent fed into the reactor can be one or more of hydrazine hydrate, glucose, zinc wire, and vitamin C.

[0046] In one embodiment, the filtering device 8 is connected to the outlet end of the reactor, receives the slurry (silver chloride precipitate or silver powder mixture) discharged from the reactor through a pipeline, separates the silver chloride precipitate (precipitation stage) or elemental silver powder (reduction stage) from the liquid phase, and the outlet end of the filtering device 8 is connected to a wastewater treatment unit. The filtering device 8 can be a plate filter press, the filter plate material is reinforced polypropylene (PP), the filtering area is 10-50 m 2 , the pressure resistance is 0.6 MPa, the filter plate is designed to be hollow, supporting reverse washing of washing water, and the removal rate of residual impurities is >99%.

[0047] In one embodiment, the silver ingot casting equipment 9 receives the silver powder delivered by the filtering device 8, mixes the silver powder with borax (0.5%-1%) and then loads the mixture into a graphite crucible, melts and casts, and cools to obtain silver ingots. The silver ingot casting equipment 9 includes a medium-frequency induction furnace, a graphite crucible, and a borax feeder. The power of the medium-frequency induction furnace is 50-200 kW, the frequency is 1000-2500 Hz, and the temperature control accuracy is ±5°C; the purity of the graphite crucible is ≥99.9%, the volume is 5-20 L, and an automatic casting robot is provided; the borax feeder adopts vibration feeding, and borax is added at a rate of 0.5%-1% of the weight of the silver powder. In actual application, the silver powder is mixed with borax and then melted, the temperature gradient control is as follows: 600°C to remove volatile matter→1000°C to melt→1100°C to remove impurities, and then cast into 15 kg standard silver ingots (purity ≥99.9%), and the surface is laser engraved with batch number.

[0048] In one embodiment, the system of the present application further comprises a pure water tower 6, which is connected to the filtering device 8 and provides pure water for the washing process in the silver ingot extraction process, for washing the reduced elemental silver powder to neutralize it and ensure the purity and quality of the silver ingot. The stable water supply through the pure water tower 6 ensures the washing effect of the entire separation and purification process, effectively removes impurities and improves the purity of the silver ingot. At the same time, the pure water tower 6 can also provide high-purity pure water for the silicon wafer pickling equipment 5 for each washing step. The pure water tower 6 uses advanced water treatment technologies such as reverse osmosis and ion exchange to ensure that the output pure water meets the process requirements, has low conductivity and contains very little impurities. In the preliminary washing step, the pure water tower 6 supplies pure water to the first-stage pure water tank 15 for washing away the sulfuric acid and soluble salts remaining on the surface of the crushed silicon wafer in the soaking basket 12; in the secondary washing step, the pure water tower 6 supplies pure water to the second-stage pure water tank 18 for washing the silicon wafer multiple times until the pH value of the washing water approaches neutral to ensure that the silicon wafer has no nitric acid residue.

[0049] In one embodiment, the system of the present application further comprises an air compressor unit 7, which in this embodiment is mainly used to provide power support to realize automatic transfer of materials and normal operation of the equipment. 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 carriage 13 to realize accurate hoisting and transfer of the soaking basket 12, and accurately send the soaking basket 12 containing crushed silicon wafers into each reaction tank. During the multi-stage reaction and washing process, the air compressor unit 7 provides power for the stirring device inside the reaction tank, drives the stirrer through compressed air to make the reaction liquid and the material fully mixed, accelerate the chemical reaction, and improve the reaction efficiency and uniformity. In addition, the air compressor unit 7 can also provide air source for the filtering device 8 to blow the filter cake during the filtering process, improve the filtering effect and the drying degree of the filter cake. During the smelting stage of the silver ingot extraction, the air compressor unit 7 can provide compressed air for the cooling system of the intermediate frequency furnace to cool the furnace body, ensure the stable progress of the smelting process, and prolong the service life of the equipment. Through the stable air supply of the air compressor unit 7, the automatic operation of the entire separation and purification system and the efficient operation of the equipment are realized, and the production efficiency and safety are improved.

[0050] In the embodiment of the present application, the waste gas treatment unit comprises a negative pressure collection system and a two-stage purification system 3. The negative pressure collection system comprises a fully enclosed gas collection hood covering the top of the reaction kettle and the silicon wafer pickling equipment 5, 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 glass steel pipe, which has the effect of resisting acid and alkali corrosion, and 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 comprises a first-stage lye spray tower and a second-stage activated carbon adsorption tank.

[0051] In one embodiment, the first-stage lye spray tower uses a Glass steel tower, filled with PP Paul ring filler layer, spray liquid is 10% NaOH solution, circulation flow is 5m 3 / h, neutralize NO X , SO2 and other acid gases.

[0052] In one embodiment, a double-layer honeycomb activated carbon filter bed is arranged in the secondary activated carbon adsorption tank, with a thickness of about 0.5m, to adsorb hydrazine vapor and organic volatile substances, and a differential pressure sensor is arranged to monitor the clogging state.

[0053] In one embodiment, a gas discharge pipe of the exhaust gas treatment unit is provided with an online monitor, such as a NO X sensor with a measuring range of 0-500ppm. It should be understood that, in actual application, the monitoring threshold is set according to the set emission standard, for example, NO X concentration≤100mg / m 3 , and particulate matter≤20mg / m 3 .

[0054] In the embodiment, the wastewater treatment unit comprises a heavy metal precipitation tank 10, a silver recovery resin tower and a reverse osmosis module. The heavy metal precipitation tank 10 has a combined structure of a reaction tank and a inclined plate sedimentation tank, and lime milk (Ca(OH)2) and Na2S solution are added into the tank to control pH=9-10 to precipitate heavy metal sulfides. The silver recovery resin tower is loaded with mercaptan-based chelating resin (exchange capacity≥2.0mmol / g), and the adsorption flow rate is 2BV / h. After saturation, 5% HNO3 is used for desorption, and the enriched liquid is returned to the nitric acid tank 17 for circulation. The reverse osmosis module is built-in with a roll-type RO membrane (desalination rate≥98%), and the produced water is returned to the pure water tank, and the concentrated water enters the evaporation crystallizer.

[0055] In actual application, the wastewater containing iron, copper, aluminum and other base metal sulfates (concentration 200-500mg / L) flows into the heavy metal precipitation tank 10. By adding lime milk (Ca(OH)2) and sodium sulfide (Na2S), the pH is adjusted to 9-10 to generate heavy metal sulfide precipitates, which are separated by the 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 professional treatment center. The residual sulfuric acid and salts (pH=1.5-2.5) enter the pH adjustment tank for neutralization, and then the suspended solids (SS≤50mg / L) are removed by the coagulation sedimentation tank, and then the wastewater is treated by the reverse osmosis membrane module (desalination rate≥98%) for deep treatment. The produced water is returned to the pure water tank (reuse rate≥70%), and the concentrated water enters the evaporation crystallizer for solidification treatment. The wastewater containing trace silver ions (5-50mg / L) is pumped into the silver recovery resin tower. The tower is loaded with mercaptan-based chelating resin (exchange capacity≥2.0mmol / g), and after adsorbing silver ions, 5% nitric acid is used for desorption. The enriched liquid is returned to the nitric acid tank 17 for recycling, realizing zero waste of silver resources.

[0056] In the embodiment of the present application, the control system integrates PLC, human-machine interface (HMI) and sensors (liquid level, temperature, pH value), controls the parameters such as the transfer timing of the soaking basket 12, the start and stop of the pump group, the opening and closing of the valve, the reaction time, and realizes the unmanned operation of the whole process.

[0057] Referring to Figure 3 and Figure 4 It is shown that the embodiment also provides a method for separating and purifying silver and silicon from waste solar silicon wafers, using the separation and purification system of silver and silicon from waste solar silicon wafers described in the above embodiment. The method comprises the following steps:

[0058] S1, material loading:

[0059] Tons of crushed silicon wafers (containing silver) are 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, for 1-5mm fragments, a 20-mesh filter screen can be selected; for powders less than 1mm, a 100-mesh filter screen can be selected. The basket body of 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 arranged around the basket body and at the bottom, and a lifting ring is arranged at the top to connect with the gantry frame 13, realizing automatic transfer.

[0060] S2, multi-stage reaction and washing:

[0061] S201, removal of base metals: the soaking basket 12 is transferred from the gantry frame 13 to the sulfuric acid tank 14, 5%-20% dilute sulfuric acid is added through the automatic pump group, and soaked for 2-4 hours (temperature 20-50℃), to remove iron, copper, aluminum and other base metals (reaction generates sulfate solution), and the body solution of the sulfuric acid tank 14 is sent to the nitric acid tank 17 through the interconnecting valve of the tank body;

[0062] S202, preliminary washing: the soaking basket 12 is transferred to the first-stage pure water tank 15, the pump group injects pure water, and the residual sulfuric acid and soluble salt are washed away by soaking for 30-60 minutes, and the waste water is discharged through the bottom pipeline;

[0063] S203, silver dissolution: the soaking basket 12 is transferred to the nitric acid tank 17, 10%-30% dilute nitric acid is added through the pump group, and soaked for 3-6 hours (temperature 30-60℃), to generate silver nitrate solution (noble liquid) by the reaction of silver single element, and the silicon wafers are not dissolved and remain in the basket;

[0064] S204, secondary washing: the soaking basket 12 is transferred to the second-stage pure water tank 18, and pure water is injected multiple times (2-3 times) for washing, until the pH value of the washing water approaches neutral (6-7), to ensure that the silicon wafers have no residual nitric acid.

[0065] S3, silicon wafer recovery:

[0066] The pure silicon pieces in the soaking basket 12 are sent into the drying equipment by the belt conveyor, and after drying (moisture content <0.5%), they are collected, packaged and crushed into silicon powder by the crushing equipment, which is sold as pure silicon powder.

[0067] S4, silver ingot extraction:

[0068] S401, silver deposition: the silver nitrate noble liquid is delivered to the reaction kettle by the pump set, and the sodium chloride solution is added in proportion, and the silver chloride white precipitate is generated by stirring, and after standing, it is separated by filtration;

[0069] S402, reduction: strong reducing agent is added to the silver chloride precipitate to generate elemental silver powder, which is filtered and washed to neutral;

[0070] S403, smelting: the elemental silver powder is loaded into a graphite crucible, a small amount of borax (impurity removal flux) is added, and it is heated to 1000-1100℃ in a medium frequency furnace to melt, and after cooling, silver ingots with a purity of ≥99.9% are obtained.

[0071] S5, cycle control:

[0072] Each step is linked through the control system, such as the reaction time and liquid addition amount of the sulfuric acid tank 14 and the nitric acid tank 17, which are automatically adjusted according to the material quantity, the reducing agent addition amount in the silver deposition link is matched with the silver nitrate concentration in real time, and the reaction is fully ensured.

[0073] The separation and purification system for silver and silicon in waste solar silicon wafers disclosed in the above embodiments realizes efficient and environmentally friendly separation and purification of silver and silicon from waste solar silicon wafers by integrating multiple functional units. The soaking basket 12 in the silicon wafer processing unit is made of acid and alkali resistant titanium alloy material and is equipped with a detachable filter screen, which can adapt to silicon wafer materials of different particle sizes, effectively avoiding material leakage or clogging problems, and improving the flexibility and adaptability of material processing. The sulfuric acid tank 14 and the nitric acid tank 17 are used to remove base metals and dissolve silver, and the automatic liquid adding and discharging pump set can accurately control the addition and discharge of the reaction liquid, ensuring the stability and consistency of the reaction conditions, thereby improving the recovery efficiency and purity of silver and silicon. The reaction kettle, stirrer and reducing agent feeding device in the silver deposition and purification unit work cooperatively to realize the precipitation, reduction and generation of silver powder of silver nitrate solution, and the temperature sensor and pH online monitoring probe in the reaction kettle monitor the reaction process in real time, ensuring accurate control of the reaction conditions and further improving the recovery purity of silver. The waste gas treatment unit and the waste water treatment unit effectively treat waste gas and waste water respectively, reducing environmental pollution and meeting environmental protection requirements. At the same time, the waste water treatment unit can also realize the recycling of water resources, reducing production costs. The entire system is automatically managed by the control system, realizing unmanned operation of the whole process, improving production efficiency, reducing labor costs, reducing chemical reagent contact risk, and improving operation safety. The purification method realizes efficient, environmentally friendly and high-purity silver and silicon separation and purification effect through its unique structural design and process flow, and the cooperative work of each unit in the system makes the whole separation and purification process automatic and continuous, significantly improving the processing efficiency and capacity. In summary, the innovation in structure and method of the present application not only solves the problems of insufficient batch processing capacity, difficult purity control, poor equipment adaptability and low automation in the prior art, but also improves production efficiency, reduces labor costs, improves resource utilization and economic benefits through full-process automation control, providing an efficient, environmentally friendly and economic solution for the recycling of waste solar silicon wafers.

[0074] In the description of the present application, it should be understood that the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0075] The above described embodiments are only to illustrate the preferred modes of the present application, and are not intended to limit the scope of the present application. Any modification and improvement made by those skilled in the art to the technical solutions of the present application without departing from the design spirit of the present application shall fall within the protection scope of the present application as defined by the claims.

Claims

1. A system for separating and purifying silver and silicon in waste solar silicon wafers, characterized in that, The application relates to a silver recovery device for recovering silver from waste batteries, which comprises a silicon wafer processing unit, a silver deposition purification unit and a control system; the silicon wafer processing unit comprises a silicon wafer pickling device (5), a soaking basket (12) and a gantry frame (13), the silicon wafer pickling device (5) comprises a sulfuric acid tank (14), a first-stage pure water tank (15), a nitric acid tank (17) and a second-stage pure water tank (18) which are sequentially arranged, the tank bodies are communicated through corrosion-resistant pipelines (16), automatic valves are arranged on the corrosion-resistant pipelines (16), and an automatic liquid feeding and discharging pump group is arranged for each tank body; the soaking basket (12) is liftably connected to the gantry frame (13), and the gantry frame (13) walks above the tank bodies; the silver deposition purification unit comprises a silver deposition purification chamber (11), a filtering device (8) and a silver ingot casting device (9), a reaction kettle, a stirrer and a reducing agent feeding device are arranged in the silver deposition purification chamber (11), the reducing agent feeding device is connected with a pipeline of the reaction kettle, and the stirrer is fixed above the reaction kettle and has stirring blades extending into the reaction kettle.

2. The system for separating and purifying silver and silicon from waste solar silicon wafer according to claim 1, wherein, The basket body of the soaking basket (12) is made of acid and alkali resistant titanium alloy material, and filter screens are detachably arranged on the periphery and the bottom of the basket body; the mesh number of the filter screens ranges from 10 meshes to 200 meshes.

3. The system for separating and purifying silver and silicon from waste solar silicon wafer according to claim 1, characterized in that, Also included is an exhaust gas treatment unit comprising a caustic spray tower and an activated carbon adsorption tank to treat NO X , SO2, and organic volatiles.

4. The system for separating and purifying silver and silicon in waste and old solar silicon wafer according to claim 3, characterized in that, The silicon wafer pickling device (5) is arranged in a silicon wafer purification chamber (1), the top of the silicon wafer purification chamber (1) and the top of the silver deposition purification chamber (11) are covered with a full-closed gas collecting cover, and the full-closed gas collecting cover is communicated with a waste gas treatment unit through a waste gas collecting pipe (2).

5. The system for separating and purifying silver and silicon from waste solar silicon wafer according to claim 1, wherein, The application further comprises a waste water treatment unit, which comprises a heavy metal precipitation tank (10) and a silver recovery resin tower, and the heavy metal is precipitated by adding lime milk and Na2S, and the silver ion residue is adsorbed by the resin tower.

6. A method for separating and purifying silver and silicon in a waste solar silicon wafer, using the system for separating and purifying silver and silicon in a waste solar silicon wafer according to any one of claims 1 to 5, characterized in that, The application further comprises the following steps: Step S1, loading the broken battery pieces into the soaking basket (12) and selecting matching filter screens to obtain loaded materials; Step S2, removing the base metals in the loaded materials in the sulfuric acid tank (14) and performing primary washing to obtain silicon silver materials after primary washing; Step S3, performing silver dissolving treatment on the silicon silver materials after primary washing in the nitric acid tank (17) to obtain a silver nitrate solution and pure silicon pieces; Step S4, performing pure water washing and drying treatment on the pure silicon pieces to obtain pure silicon powder; Step S5, performing precipitation, reduction and smelting treatment on the silver nitrate solution to obtain silver ingots.

7. The method for separating and purifying silver and silicon from waste solar silicon wafer according to claim 6, characterized in that, In step S2, the reaction conditions for removing the base metals in the sulfuric acid tank (14) are 5%-20% dilute sulfuric acid soaking for 2-4 hours and a temperature of 20-50 DEG C. 8.The method for separating and purifying silver and silicon from waste solar silicon wafer according to claim 6, characterized in that, In step S3, the reaction conditions for performing silver dissolving treatment in the nitric acid tank (17) are 10%-30% dilute nitric acid soaking for 3-6 hours and a temperature of 30-60 DEG C. 9.The method for separating and purifying silver and silicon from waste solar silicon wafer according to claim 6, characterized in that, In step S5, a reducing agent is added to reduce the silver nitrate solution to generate elemental silver powder, and the reducing agent is one or more of hydrazine hydrate, glucose, zinc wire and vitamin C.

10. The method for separating and purifying silver and silicon from waste solar silicon wafer according to claim 6, characterized in that, In step S5, 0.5%-1% borax is added to the silver ingot casting device (9) for smelting treatment, and the smelting temperature is 1000-1100 DEG C.

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