Photovoltaic module recovery method and system

Abstract

The invention belongs to the technical field of photovoltaic module recovery, and particularly discloses a photovoltaic module recovery method and system.The method comprises the steps that a photovoltaic module with a frame removed is placed in a supercritical reaction kettle, CO2 gas is introduced, treatment is conducted for 30 minutes at the temperature of 50-65 DEG C, and the swelling rate of an EVA adhesive film is made to be larger than or equal to 40%; then milling and stripping the back plate in a partitioned manner, scanning the EVA layer by laser, and realizing lossless stripping of the front glass through a thermal expansion coefficient difference; the stripped EVA layer is decomposed through a 250 DEG C low-temperature pyrolyzing furnace and then enters a 500 DEG C high-temperature section for residue cracking; 2 mol / L ethanolamine solution is adopted for leaching silver at the temperature of 80 DEG C, industrial flue gas containing 10% of CO2 is introduced into the leachate, Ag2CO3 sediment is generated, and carbon sequestration is achieved; removing the antireflection layer by using a mixed solution of 5% HF and 10% HNO3 to obtain a silicon material with the purity of more than 99.9%; and filtering the reacted mixed liquid to form filtrate, and regenerating through a rectifying tower. According to the method, efficient recovery of the photovoltaic module can be realized, fluoride emission is reduced, and meanwhile, the metal recovery rate and the resource recycling rate are increased.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic module recycling technology, and in particular to a method and system for recycling photovoltaic modules. Background Technology

[0002] With the rapid development of the photovoltaic industry, the recycling of photovoltaic modules has gradually become a critical issue that urgently needs to be addressed. However, existing photovoltaic module recycling technologies face many challenges in practical applications, with these technical bottlenecks mainly concentrated in key stages such as mechanical separation, pyrolysis, and chemical leaching.

[0003] In the mechanical separation stage, traditional recycling methods rely on physical forces, such as cutting, grinding, and squeezing, to separate the frame, glass, and backsheet of photovoltaic modules. This method is usually difficult to process broken photovoltaic modules and the processing speed is relatively slow, making it difficult to meet the needs of large-scale recycling.

[0004] In the pyrolysis process, existing technologies typically employ high-temperature pyrolysis exceeding 500°C. These high-temperature conditions release large amounts of harmful gases, especially fluorides, such as CF4, with emissions exceeding 200 ppm, causing severe environmental pollution. Furthermore, high-temperature pyrolysis leads to insufficient metal recovery rates; for example, silver leaching rates are below 85%, further limiting the economic and environmental viability of the recycling process.

[0005] In the chemical leaching stage, existing technologies mostly employ acid extraction for silver. This process generates wastewater with high concentrations of chemical oxygen demand (COD), typically exceeding 5000 mg / L. Furthermore, commonly used amine complexing agents suffer significant losses during recycling, with a recycling loss rate exceeding 30%. This not only increases recovery costs but also reduces the sustainability of the process.

[0006] In summary, existing photovoltaic module recycling technologies suffer from inefficiencies, severe environmental pollution, and excessively high costs in key processes such as mechanical stripping, pyrolysis, and chemical leaching. These problems significantly hinder the further development and widespread application of photovoltaic module recycling technologies. Therefore, it is necessary to develop an efficient, environmentally friendly, and economical photovoltaic module recycling technology. Summary of the Invention

[0007] The purpose of this invention is to provide a photovoltaic module recycling method and system to solve the aforementioned technical problems existing in the prior art.

[0008] To achieve the above objectives, in one aspect, the present invention provides a method for recycling photovoltaic modules, comprising the following steps: placing the photovoltaic module with its frame removed in a supercritical reactor, introducing CO2 gas, and treating it at 50℃~65℃ for 30 minutes to achieve an EVA film swelling rate ≥40%; performing partitioned milling and peeling off the backsheet from the pretreated photovoltaic module; laser scanning the EVA layer to achieve non-destructive peeling of the front glass through the difference in thermal expansion coefficients; and first decomposing the EVA layer in a 250℃ low-temperature pyrolysis furnace before proceeding with the recycling process. The pyrolysis residue at 500℃ is controlled to have fluoride emissions <20ppm; silver is leached at 80℃ using a 2mol / L ethanolamine solution with a leaching rate ≥98.5%; industrial flue gas containing 10% CO2 is introduced into the leachate to generate Ag2CO3 precipitate, achieving carbon sequestration; the antireflective layer is removed using a mixture of 5% HF and 10% HNO3 to obtain silicon material with a purity >99.9%; the mixture after filtration forms a filtrate, which is then regenerated via a distillation column; the amine complexing agent is recycled 10 times with a loss of <8%.

[0009] The photovoltaic module recycling method disclosed in the above technical solution achieves efficient recycling of photovoltaic modules through steps such as supercritical CO2 treatment, partition milling, laser stripping, stepped pyrolysis and CO2 mineralization, significantly reducing fluoride emissions, while improving metal recovery rate and resource recycling rate.

[0010] To further optimize the solution, in step S1, the critical pressure for supercritical CO2 treatment is 7.38 MPa, and the CO2 purity is >99.5%. This step ensures that the EVA film swelling rate is ≥40% by precisely controlling the pressure and purity of supercritical CO2, thereby improving the peeling efficiency.

[0011] Further optimization of the scheme: In step S2, a three-stage pressure roller group is used for multi-stage partition milling. The milling cutter group is equipped with staggered carbide cutters, the rotation speed is 2000rpm±5%, and the milling force is controlled at 200N±10N to ensure that the back glass removal rate is >99.5%.

[0012] To further optimize the scheme, in step S3, a 1064nm fiber laser is used to scan the back side of the EVA layer with an energy density of 15J / cm². 2 With a pulse width of 10 ns, the front glass is peeled off non-destructively using the difference in thermal expansion coefficients. This step achieves non-destructive peeling of the front glass through laser parameter optimization, with an integrity rate of >99.9%, avoiding high-temperature contamination.

[0013] To further optimize the scheme, in step S4, the low-temperature pyrolysis is divided into two stages: a low-temperature stage (200℃~380℃) prioritizes the decomposition of EVA; and a high-temperature stage (500℃~600℃) treats the residue, reducing fluoride emissions by 90%. In this step, the two-stage pyrolysis controls fluoride emissions to <20ppm, with the low-temperature stage prioritizing EVA decomposition and the high-temperature stage treating the residue. This two-stage pyrolysis reduces fluoride emissions by 90%, balancing efficiency and environmental protection.

[0014] To further optimize the scheme, in step S5, the pH of the ethanolamine solution is 9±0.2, and the redox potential is controlled between +200mV and +300mV. By controlling the pH and redox potential of the ethanolamine solution, the silver leaching rate is ≥98.5%, while reducing the COD value of the wastewater.

[0015] Further optimization of the scheme resulted in an industrial flue gas flow rate of 2 L / min, a carbon utilization rate of >95%, and a carbon sequestration capacity of 1.2 kg CO2 / kg residue (each kilogram of residue can sequester 1.2 kg of carbon dioxide).

[0016] On the other hand, the present invention also provides a photovoltaic module recycling system for implementing the photovoltaic module recycling method described in any of the above claims. The recycling system includes: a supercritical reactor for CO2 swelling of EVA film, equipped with a pressure sensor and a temperature controller; a multi-stage milling device including a three-stage pressure roller assembly and staggered cemented carbide cutting tools; a laser stripping device including a 1064nm fiber laser, an energy density adjustment module, and a pulse width adjustment module; a stepped pyrolysis furnace including a low-temperature section and a high-temperature section, equipped with a nitrogen atmosphere control system and a fluoride emission monitoring device; a CO2 mineralization reactor integrating a flue gas inlet and a high-purity CO2 injection interface, equipped with a precipitation separation device; and a solvent regeneration device including a distillation column and a condenser for the recycling of amine complexing agents. This system adopts an integrated design, with the supercritical reactor, milling device, and laser stripping modules working collaboratively, significantly improving the overall recovery rate and environmental friendliness.

[0017] The scheme was further optimized so that the oxygen content in the low-temperature section of the stepped pyrolysis furnace is <50ppm, and the fluoride emission in the high-temperature section is <20ppm. The stepped pyrolysis furnace further reduces pollution through dual control of oxygen content in the low-temperature section and fluoride emissions in the high-temperature section.

[0018] To further optimize the design, the multi-stage partitioned milling device is equipped with a force sensor and a speed controller. This combination ensures process stability and accuracy while reducing tool wear.

[0019] As can be seen from the above, the photovoltaic module recycling method and system provided in this application achieves efficient recycling of photovoltaic modules through steps such as supercritical CO2 treatment, partition milling, laser stripping, stepped pyrolysis and CO2 mineralization. At the same time, it significantly reduces fluoride emissions and chemical oxygen demand, improves metal recovery rate and resource recycling rate, and has the advantages of efficient recycling, environmental protection and emission reduction and resource recycling. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart of the photovoltaic module recycling method according to Embodiment 1 of the present invention;

[0022] Figure 2 This is a block diagram of the photovoltaic module recycling system of Embodiment 2 of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Example 1

[0026] Reference Figure 1 As shown in Embodiment 1 of this application, a photovoltaic module recycling method is provided, including the following steps: S1, supercritical CO2 treatment; S2, back layer stripping; S3, front glass layer removal; S4, low-temperature pyrolysis; S5, selective metal recovery and CO2 mineralization; S6, silicon material purification and resource recycling.

[0027] In the supercritical CO2 treatment step, the photovoltaic modules with their frames removed are placed in a supercritical reactor, CO2 gas is introduced, and the reactor is treated at 50℃~65℃ for 30 minutes to achieve a swelling rate of ≥40% for the EVA film. The supercritical CO2 treatment can be achieved by adjusting the temperature and pressure, and the treatment time can be adjusted according to the thickness of the EVA film. As a preferred embodiment, the reactor can be equipped with a stirring device to improve mass transfer efficiency.

[0028] In the backsheet peeling step, the pre-treated photovoltaic module is subjected to section milling and the backsheet is peeled off. In one specific embodiment, milling can be performed mechanically or by laser; section processing helps improve peeling accuracy. Further optimization can be achieved by adjusting the milling parameters according to the characteristics of the backsheet material.

[0029] In the front glass layer removal step, a laser scans the EVA layer, achieving non-destructive peeling of the front glass through the difference in thermal expansion coefficients. For example, laser parameters, including wavelength, energy density, and pulse width, are adjustable, and the scanning path can be helical or grid-type. As a result, the glass peeling integrity rate can reach over 99%.

[0030] In the low-temperature pyrolysis step, the stripped EVA layer is first decomposed in a 250°C low-temperature pyrolysis furnace, and then enters a 500°C high-temperature section to pyrolyze the residue. The pyrolysis temperature can be controlled in stages, with the low-temperature section preferentially decomposing organic matter and the high-temperature section treating inorganic residue. In one specific embodiment, the pyrolysis furnace can be equipped with an exhaust gas treatment system to control fluoride emissions.

[0031] In the selective metal recovery and CO2 mineralization step, silver is leached using a 2 mol / L ethanolamine solution at 80°C, achieving a leaching rate of ≥98.5%. Industrial flue gas containing 10% CO2 is then introduced into the leachate to generate Ag2CO3 precipitate. The leaching conditions, including temperature, pH, and redox potential, can be precisely controlled. Further optimization could be achieved by integrating a gas distribution device into the mineralization reactor to improve carbon sequestration efficiency.

[0032] In the silicon material purification and resource recycling process, a mixture of 5% HF and 10% HNO3 is used to remove the antireflective layer, yielding silicon material with a purity >99.9%. The mixture after filtration forms a filtrate, which is then regenerated via a distillation column. For example, the acid ratio can be adjusted according to the degree of silicon wafer contamination, and the distillation column can be equipped with multi-stage condensation to improve solvent recovery.

[0033] This embodiment reduces the difficulty of mechanical separation through supercritical CO2 pretreatment, achieves non-destructive separation of modules using partitioned milling and laser exfoliation, controls pollutant emissions through stepped pyrolysis, improves metal recovery rate by combining selective leaching and CO2 mineralization, and finally regenerates silicon material through acid washing purification. Compared with existing technologies, this method solves the problems of low mechanical separation efficiency, severe pyrolysis pollution, and high chemical leaching costs, achieving efficient and environmentally friendly recycling of photovoltaic modules. In one specific embodiment, EVA film swelling treatment improves exfoliation efficiency, low-temperature pyrolysis reduces fluoride emissions, the ethanolamine leaching system reduces wastewater COD, and solvent recycling reduces reagent consumption.

[0034] Further optimization of the scheme resulted in a supercritical CO2 treatment step with a critical pressure of 7.38 MPa and a CO2 purity of >99.5%.

[0035] In one specific embodiment, the critical pressure of 7.38 MPa refers to the minimum pressure required for CO2 to reach a supercritical state. This pressure range ensures that CO2 maintains stable supercritical fluid characteristics within a temperature range of 50°C to 65°C. The requirement of CO2 purity >99.5% is achieved through a two-stage distillation unit. The first stage uses -20°C low-temperature condensation to remove moisture, and the second stage uses molecular sieves to adsorb residual organic matter. As a preferred implementation, pressure control employs a PID closed-loop system. By comparing pressure sensor data with the set value in real time, the opening of the intake valve is adjusted to control pressure fluctuations within ±0.05 MPa. In a further optimized scheme, CO2 purity detection uses an online infrared spectrometer, automatically sampling and analyzing every 15 minutes. When the detected value falls below 99.5%, an alarm is triggered and a backup gas source switching device is activated.

[0036] Therefore, by precisely controlling the critical pressure and CO2 purity, the swelling efficiency of the EVA film can be significantly improved. Experimental data shows that when the pressure deviates from 7.38 MPa ± 0.5 MPa, the EVA swelling rate decreases by 12% to 15%; while CO2 purity below 99.5% leads to the formation of a barrier layer of organic impurities on the EVA surface, reducing swelling uniformity by 23%. This embodiment effectively solves the problem of incomplete film peeling caused by unstable supercritical parameters in traditional recycling methods, while avoiding the risk of contamination of subsequent metal recycling processes by impurity gases.

[0037] The scheme was further optimized by using a three-stage pressure roller group for multi-stage partition milling. The milling cutter group was equipped with staggered carbide cutters, the rotation speed was 2000rpm±5%, and the milling force was controlled at 200N±10N to ensure that the back glass removal rate was >99.5%.

[0038] In one specific embodiment, the three-stage pressing roller assembly consists of three independently controlled roller pressing units, each equipped with a pressure sensor and a displacement compensation mechanism. The staggered carbide cutting tools are made of tungsten-cobalt alloy, with a rake angle of 15°±2° and a clearance angle of 8°±1°. The tool spacing is dynamically adjusted according to the size of the photovoltaic module. Speed ​​control is achieved through closed-loop feedback via a variable frequency motor, and the milling force is adjusted in real time via a hydraulic servo system. As a preferred embodiment, the first-stage roller assembly uses rough milling, the second stage performs transition milling, and the third stage completes the finish milling operation, with the milling depths distributed in a 4:3:3 ratio.

[0039] Therefore, this embodiment effectively solves the problems of slow processing speed and difficulty in handling broken components in traditional mechanical separation through multi-stage partitioned milling and precise mechanical control. The three-stage pressure roller group's graded operation mode can adapt to backsheet materials of different thicknesses, the staggered tool layout reduces cutting vibration, and the coordinated control of rotation speed and milling force ensures peeling accuracy. Compared with the single mechanical cutting method described in the background art, this solution increases the backsheet glass removal rate from less than 90% to over 99.5%, while improving milling efficiency by approximately 40%, and can handle broken components. Through the interlocking protection of the force sensor and speed controller, tool wear is reduced by 30%, achieving a highly efficient and stable mechanical separation process.

[0040] Further optimization of the scheme involved using a 1064nm fiber laser to scan the back of the EVA layer, achieving an energy density of 15J / cm². 2 With a pulse width of 10ns, the non-destructive peeling of the front glass is achieved through the difference in thermal expansion coefficients.

[0041] In one specific embodiment, the 1064nm fiber laser is a near-infrared laser, whose wavelength can effectively penetrate the EVA film without being excessively absorbed. Energy density: 15 J / cm². 2 The settings are based on the thermal decomposition threshold of the EVA film and the thermal stability of the glass. This parameter ensures that the film expands sufficiently under heat while avoiding thermal damage to the glass layer. The 10ns pulse width enables instantaneous energy deposition, promoting rapid separation of the EVA layer from the glass interface through thermal shock. The difference in thermal expansion coefficients is utilized because the volume expansion rate of the EVA film after heating (approximately 8%) is much higher than that of glass (approximately 0.5%), resulting in shear stress sufficient to destroy the interfacial adhesion. As a preferred implementation, the laser scanning path can adopt a helical trajectory, with a scanning interval set to 0.5mm and a scanning speed controlled at 10mm / s to ensure uniform peeling.

[0042] To address this, this embodiment achieves interface separation by precisely controlling laser parameters and utilizing the differences in material thermophysical properties. Compared to existing mechanical peeling technologies, it avoids the risk of glass breakage, increasing the peeling integrity rate to over 99.9%. Compared to traditional high-temperature pyrolysis methods, the operating temperature is reduced by over 200°C, and fluoride emissions are reduced by 90%. The non-contact nature of laser processing allows it to adapt to component breakage conditions, increasing processing efficiency by 3 times and eliminating tool wear issues. The peeling mechanism achieved through the difference in thermal expansion coefficients fundamentally solves the problem of glass breakage caused by mechanical force transmission.

[0043] The scheme was further optimized, and the low-temperature pyrolysis was divided into two stages: the low-temperature stage was 200℃~380℃, which preferentially decomposed EVA; the high-temperature stage was 500℃~600℃, which treated the residue and reduced fluoride emissions by 90%.

[0044] In one specific embodiment, the low-temperature zone is set to a temperature range of 200℃ to 380℃. This temperature range ensures the complete decomposition of the EVA film while preventing the excessive release of fluorides caused by high temperatures. The high-temperature zone is set to a temperature range of 500℃ to 600℃, primarily used to treat the residue after EVA decomposition. By precisely controlling the upper temperature limit, the formation of fluorides can be effectively suppressed. As a preferred implementation, the low-temperature zone can employ a gradient heating mode, for example, increasing from 200℃ to 380℃ at a rate of 5℃ / min to ensure the gradual decomposition of EVA. The high-temperature zone can employ isothermal control, for example, maintaining it at 550℃ ± 10℃ to achieve complete pyrolysis of the residue. Further optimization of the scheme achieves fluoride emission reduction through a two-stage temperature synergy: the low-temperature zone reduces the formation of fluoride precursors, while the high-temperature zone reduces fluoride emission concentrations through thermodynamic control.

[0045] Therefore, this embodiment solves the problem of high fluoride emissions in traditional high-temperature pyrolysis processes by using staged temperature control. Specifically, the low-temperature stage prioritizes the decomposition of EVA, avoiding the co-pyrolysis reaction between organic matter and fluorides, thus reducing fluoride formation at the source; the high-temperature stage treats the residue within a limited temperature range, effectively inhibiting the secondary formation of fluorides. Compared with existing technologies, this scheme reduces fluoride emissions from over 200 ppm in traditional processes to a 90% reduction while ensuring complete EVA decomposition, significantly improving the environmental friendliness of the process. Furthermore, the two-stage temperature control also helps maintain metal recovery rates, avoiding the adverse effects of high temperatures on the recovery of metals such as silver.

[0046] To further optimize the process, during the leaching of silver with ethanolamine solution, the pH of the solution was controlled at 9±0.2, and the redox potential was controlled at +200mV to +300mV.

[0047] In one specific embodiment, precise pH control is achieved through an online pH meter and an automatic dosing system, with fine adjustments made using sodium hydroxide or hydrochloric acid. Redox potential regulation is accomplished by adding an oxidizing agent or a reducing agent, such as hydrogen peroxide as the oxidizing agent and sodium sulfite as the reducing agent. As a preferred embodiment, an ORP sensor is used in conjunction with a metering pump for coordinated control to ensure the potential stability of the reaction system.

[0048] To address this, the leaching selectivity of silver can be significantly improved through the synergistic control of pH and redox potential. In a weakly alkaline environment, ethanolamine achieves optimal complexation ability for silver, while the redox potential inhibits the dissolution of impurity metals. Therefore, compared to the acid-based silver extraction process in existing technologies, this method avoids the generation of high-COD wastewater, and the loss rate of the amine complexing agent is reduced to below 8%. In one specific embodiment, pH stability reduces the decomposition of the amine complexing agent, while potential control reduces the occurrence of side reactions, thereby achieving higher metal recovery rates and lower operating costs.

[0049] To further optimize the solution, this application proposes a technical solution for controlling the industrial flue gas flow rate at 2 L / min, where the carbon utilization rate exceeds 95% and the carbon sequestration reaches 1.2 kg CO2 / kg residue. In one specific embodiment, the industrial flue gas enters the reaction system through a pipeline at a constant flow rate, with the flow rate controlled by a mass flow meter linked to a regulating valve. As a preferred embodiment, the flue gas distributor adopts a perforated plate structure with a pore size of 3 mm and an opening rate of 30%, ensuring uniform airflow distribution. The carbon sequestration process is controlled in real time at the reaction endpoint by an online pH monitor; when the pH drops to 7.2, the gas flow is stopped, and the precipitate is separated by a plate and frame filter press.

[0050] At the technical implementation level, the flow rate control module includes a buffer tank and a pressure stabilizing device, maintaining the operating pressure at 0.15MPa±5%. The flue gas pretreatment unit is equipped with a particulate filter with a filtration accuracy of 5μm to prevent nozzle clogging. Carbon utilization is continuously monitored using an NDIR infrared analyzer to measure the CO3 concentration in the exhaust gas, with a data acquisition frequency of 1 time / second. The mineralization reactor is made of 316L stainless steel and is designed with flow guide baffles, with the mixing time controlled at 8–10 minutes. The sedimentation separation zone is equipped with an inclined plate settling device with a settling velocity of 0.8m / h, and the clarified liquid is recycled to the leaching process.

[0051] This embodiment optimizes gas-liquid mass transfer efficiency by precisely controlling the reaction gas flow rate, ensuring sufficient contact between CO2 and the ethanolamine leachate. This solves the problem of incomplete silver precipitation caused by uneven gas distribution in traditional processes, while simultaneously achieving efficient CO2 fixation in industrial flue gas. Compared to the COD exceeding the standard problem in the background technology, this method reduces the COD value of the post-reaction liquid to below 800 mg / L, and reduces the loss of the amine complexing agent per cycle to 2.3%. XRD analysis of the mineralized product shows it to be pure-phase Ag2CO2 with a purity of 99.7%, and the silver recovery rate is increased to 98.8%.

[0052] Example 2

[0053] Reference Figure 2 As shown in Embodiment 2 of this application, a photovoltaic module recycling system is proposed to implement the photovoltaic module recycling method described in Embodiment 1. The system includes a supercritical reactor, a multi-stage milling device, a laser stripping device, a stepped pyrolysis furnace, a CO2 mineralization reactor, and a solvent regeneration device. The supercritical reactor is used for CO2 swelling of EVA film and is equipped with a pressure sensor and a temperature controller. The multi-stage milling device includes a three-stage pressure roller assembly and staggered carbide cutting tools. The laser stripping device includes a 1064nm fiber laser, an energy density adjustment module, and a pulse width adjustment module. The stepped pyrolysis furnace includes a low-temperature section and a high-temperature section and is equipped with a nitrogen atmosphere control system and a fluoride emission monitoring device. The CO2 mineralization reactor integrates a flue gas inlet and a high-purity CO2 injection interface and is equipped with a precipitation separation device. The solvent regeneration device includes a distillation column and a condenser for the recycling of the amine complexing agent.

[0054] The pressure sensor for the supercritical reactor can be a piezoresistive or capacitive sensor, and the temperature controller can employ a PID control algorithm. The three-stage pressure roller assembly of the multi-stage zone milling device can be driven by hydraulic or servo motors, and the staggered cemented carbide cutting tools can be made of tungsten-cobalt or titanium-based alloys. The energy density adjustment module of the laser ablation device can be implemented using an acousto-optic modulator, and the pulse width adjustment module can employ electro-optic modulation technology. The nitrogen atmosphere control system of the stepped pyrolysis furnace can be controlled by a mass flow meter and an oxygen analyzer working in tandem. The precipitation separation device of the CO2 mineralization reactor can be centrifugal separation or membrane filtration. The distillation column of the solvent regeneration device can be a packed column or a plate column structure, and the condenser can be a shell-and-tube or plate heat exchanger.

[0055] This photovoltaic module recycling system, through its integrated equipment configuration, solves the problems of low mechanical separation efficiency, high pyrolysis pollution, and high chemical leaching costs in existing technologies. A supercritical reactor achieves efficient swelling of the EVA film, a multi-stage milling device ensures a high removal rate of the back glass, and a laser stripping device achieves non-destructive separation of the front glass. A stepped pyrolysis furnace significantly reduces fluoride emissions through segmented temperature control, a CO2 mineralization reactor simultaneously achieves metal recovery and carbon sequestration, and a solvent regeneration device effectively reduces the loss of amine complexing agents. The coordinated operation of all modules in the system significantly improves environmental performance and economic efficiency while ensuring recycling efficiency.

[0056] Further optimization of the scheme resulted in oxygen content of <50ppm in the low-temperature section and fluoride emissions of <20ppm in the high-temperature section of the stepped pyrolysis furnace.

[0057] In the stepped pyrolysis furnace, oxygen content control in the low-temperature section is achieved through a nitrogen atmosphere control system. Specifically, a mass flow meter is used to precisely adjust the nitrogen injection rate, in conjunction with a real-time oxygen sensor for monitoring. Fluoride emissions control in the high-temperature section is achieved through a two-stage treatment: firstly, an alkaline spray tower is installed at the outlet of the high-temperature section of the pyrolysis furnace, using a 10% NaOH solution to neutralize acidic gases; secondly, an activated carbon adsorption device is installed to adsorb residual fluorides. The oxygen sensor is a zirconia type, with a detection accuracy of ±1 ppm; the liquid-to-gas ratio of the alkaline spray tower is controlled at 3 L / m³. 3 The velocity in the empty tower is 1.2 m / s.

[0058] In one specific embodiment, the oxygen content in the low-temperature section is controlled by the following method: an airlock device is installed at the feed inlet of the pyrolysis furnace, employing a double-gate alternating opening and closing structure, with nitrogen gas introduced in the gap to maintain a slight positive pressure; the furnace body adopts a double-shell design, with nitrogen gas introduced into the interlayer as a protective gas. In the high-temperature fluoride treatment, the spray tower adopts a cross-flow design, with a packing layer height of 1.5m, using polypropylene Pall ring packing; the activated carbon adsorption device is equipped with two sets of parallel tanks for easy alternating regeneration, with a carbon layer thickness of 0.8m and an empty bed contact time of 2 seconds.

[0059] Therefore, this embodiment effectively solves the technical problem of excessive fluoride emissions in traditional pyrolysis processes by precisely controlling pyrolysis environmental parameters. The low-temperature, low-oxygen environment prevents the formation of dioxins during EVA pyrolysis, while emission control in the high-temperature stage reduces fluoride concentration from the conventional 200 ppm to below 20 ppm. Compared with the high-temperature pyrolysis process mentioned in the background art, the technical route of staged temperature control combined with end-of-pipe treatment reduces harmful gas emissions by 90% while ensuring pyrolysis efficiency, without requiring additional energy consumption for exhaust gas treatment.

[0060] The design was further optimized by equipping the multi-level partition milling device with a force sensor and a speed controller.

[0061] A force sensor is used to monitor the milling force in real time during the milling process, with the milling force controlled within the range of 200N ± 10N. A speed controller is used to precisely adjust the speed of the milling cutter assembly, with the speed controlled within the range of 2000rpm ± 5%. The force sensor can be a strain gauge or piezoelectric sensor, mounted on the support structure of the milling device or the tool clamping area. The speed controller can be a variable frequency speed control or a servo control system, forming a closed-loop control with the milling motor. As a preferred embodiment, the force sensor and speed controller can be integrated into the same control unit to achieve coordinated adjustment of milling parameters.

[0062] In one specific embodiment, the mechanical parameters during the milling process can be precisely controlled through the coordinated action of a force sensor and a speed controller. The force sensor provides real-time feedback of milling force data, and when the milling force exceeds the set range, the speed controller adjusts the milling cutter speed accordingly to maintain a stable milling state. This ensures a back glass removal rate >99.5% while preventing tool wear or component damage due to excessive milling force. Compared to existing technologies, this embodiment solves the problems of slow processing speed and difficulty in precise control during mechanical separation, achieving efficient and stable milling operations.

[0063] Compared with the prior art, the embodiments of the present invention disclose at least the following beneficial effects:

[0064] This invention achieves efficient, environmentally friendly, and resource-recycling recycling of photovoltaic modules through innovative methods and system structures. A supercritical reactor utilizes precise pressure and temperature control to efficiently swell the EVA film, reducing the difficulty of mechanical separation. A multi-stage, zoned milling device achieves high-precision backsheet peeling through optimized tool configuration and parameter control, improving processing efficiency and reducing tool wear. A laser peeling device utilizes the difference in thermal expansion coefficients to achieve non-destructive peeling of the front glass, reducing pollution and improving glass integrity. A stepped pyrolysis furnace effectively reduces fluoride emissions through segmented temperature control, while simultaneously achieving EVA decomposition and residue treatment. A CO2 mineralization reactor, combined with industrial flue gas, achieves efficient silver recovery and carbon sequestration, reducing greenhouse gas emissions. A solvent regeneration device achieves the recycling of amine complexing agents through distillation and condensation, reducing costs and improving sustainability. The synergistic effect of these structures solves the efficiency, pollution, and cost problems of traditional recycling technologies, providing an efficient and environmentally friendly technical solution for the large-scale recycling of photovoltaic modules.

[0065] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "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, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0066] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for recycling photovoltaic modules, characterized in that, Includes the following steps: Step S1, Supercritical CO2 treatment: Place the photovoltaic module with the frame removed in a supercritical reactor, introduce CO2 gas, and treat it at 50℃~65℃ for 30 minutes to make the swelling rate of EVA film ≥40%. Step S2, Backside Layer Peeling: The pre-treated photovoltaic module is milled in sections and the backsheet is peeled off; Step S3, front glass layer removal: Laser scanning of the EVA layer, achieving non-destructive peeling of the front glass through the difference in thermal expansion coefficients; Step S4, Low-temperature pyrolysis: The stripped EVA layer is first decomposed in a 250℃ low-temperature pyrolysis furnace, and then enters a 500℃ high-temperature section to crack the residue, while controlling the emission of fluorides. Step S5, Selective Metal Recovery and CO2 Mineralization: Silver is leached at 80°C using a 2 mol / L ethanolamine solution; industrial flue gas containing 10% CO2 is introduced into the leachate to generate Ag2CO3 precipitate, thus achieving carbon sequestration; Step S6, Silicon Material Purification and Resource Recycling: The antireflective layer is removed using a mixture of 5% HF and 10% HNO3 to obtain silicon material with a purity > 99.9%; the mixture after the reaction is filtered to form a filtrate, which is then regenerated by a distillation column.

2. The photovoltaic module recycling method according to claim 1, characterized in that, In step S1, the critical pressure for supercritical CO2 treatment is 7.38 MPa, and the CO2 purity is >99.5%.

3. The photovoltaic module recycling method according to claim 1, characterized in that, In step S2, a three-stage pressure roller group is used for multi-stage partition milling. The milling cutter group is equipped with staggered carbide cutters, the rotation speed is 2000rpm±5%, and the milling force is controlled at 200N±10N to ensure that the back glass removal rate is >99.5%.

4. The photovoltaic module recycling method according to claim 1, characterized in that, In step S3, a 1064nm fiber laser is used to scan the back side of the EVA layer with an energy density of 15J / cm². 2 With a pulse width of 10ns, the non-destructive peeling of the front glass is achieved through the difference in thermal expansion coefficients.

5. The photovoltaic module recycling method according to claim 1, characterized in that, In step S4, the low-temperature pyrolysis is divided into two stages: the low-temperature stage is 200℃~380℃, which preferentially decomposes EVA; the high-temperature stage is 500℃~600℃, which treats the residue and reduces fluoride emissions by 90%.

6. The photovoltaic module recycling method according to claim 1, characterized in that, In step S5, the pH of the ethanolamine solution is 9±0.2, and the redox potential is controlled between +200mV and +300mV.

7. The photovoltaic module recycling method according to claim 1, characterized in that, In step S5, the flow rate of the industrial flue gas is 2L / min, the carbon utilization rate is >95%, and the carbon sequestration is 1.2kg CO2 / kg residue.

8. A photovoltaic module recycling system for implementing the photovoltaic module recycling method according to any one of claims 1 to 7, characterized in that, include: Supercritical reactor for CO2 swelling of EVA film, equipped with pressure sensor and temperature controller; A multi-stage partitioned milling device, comprising a three-stage pressure roller group and staggered carbide cutting tools; The laser ablation device includes a 1064nm fiber laser, an energy density adjustment module, and a pulse width adjustment module; The stepped pyrolysis furnace includes a low-temperature section and a high-temperature section, and is equipped with a nitrogen atmosphere control system and a fluoride emission monitoring device. The CO2 mineralization reactor integrates a flue gas inlet and a high-purity CO2 injection interface, and is equipped with a precipitation separation device. Solvent regeneration unit, including distillation column and condenser, for the recycling of amine complexing agents.

9. The photovoltaic module recycling system according to claim 8, characterized in that, The oxygen content in the low-temperature section of the stepped pyrolysis furnace is <50ppm, and the fluoride emission in the high-temperature section is <20ppm.

10. The photovoltaic module recycling system according to claim 8, characterized in that, The multi-level partition milling device is equipped with a force sensor and a speed controller.

Images