Low-energy consumption resource recycling method for photovoltaic modules

Abstract

This invention discloses a low-energy-consumption resource recycling method for photovoltaic modules, comprising a step of gradient heating treatment of the photovoltaic panel for sequentially peeling off the glass and backsheet to recover the solar silicon cells. The gradient heating treatment includes the following operations: First, heating a double-glass photovoltaic panel at 300~600 ℃ for 30s~4min, stopping heating, and quickly peeling off one side of the glass; or heating a single-glass photovoltaic panel at 100~200 ℃ for 10s~1min, stopping heating, and quickly peeling off the backsheet; Second, continuing to heat the photovoltaic panel treated in the first step at 400~700 ℃ for 10s~2min, stopping heating, and quickly peeling off the remaining side of the glass to obtain structurally intact solar silicon cells. The recycling method of this invention adopts a stepped short-time heating and peeling treatment, which effectively separates the glass, backsheet, and solar silicon cells of the photovoltaic panel while significantly shortening the processing time, greatly reducing separation energy consumption. Combined with the cleaning treatment of a green organic composite solution, it successfully recovers clean and intact solar silicon cells, which is conducive to promoting the green and circular development of the photovoltaic industry.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic module recycling technology, specifically a method for low-energy dismantling and resource recycling of photovoltaic modules. Background Technology

[0003] The current disposal of retired photovoltaic (PV) modules faces technical challenges such as low material separation efficiency, high silicon wafer breakage rate, difficulty in treating fluorine-containing pollutants, and insufficient economic viability. The core bottleneck in PV module recycling lies in the difficulty of obtaining high-value, intact silicon wafers economically and environmentally. Specifically: 1. Physical methods (such as mechanical crushing and high-pressure jet grinding) can achieve preliminary separation of materials such as glass and aluminum frames, but they do not adequately protect the integrity of silicon wafers, inevitably leading to severe breakage of brittle silicon solar cells. Furthermore, they cannot effectively separate fluorine-containing backsheets, resulting in the loss of high-value-added materials.

[0004] 2. Pyrolysis methods (such as low-temperature pyrolysis and high-temperature incineration) rely on external heating for a long time. Due to poor heat conduction efficiency and uneven temperature distribution, energy utilization is low. At the same time, the thermal decomposition of the backplate will release toxic gases such as hydrogen fluoride (HF), posing significant environmental risks.

[0005] 3. Although chemical methods (such as acid leaching and solvent dissolution) can extract valuable metals such as silver and silicon, they require the use of strong acids (such as nitric acid) or organic solvents (such as acetone), which produce fluorine-containing or toxic waste liquids. Furthermore, the treatment cost accounts for a high proportion of the total recycling cost, and they cannot solve the problem of silicon wafer breakage during the dismantling stage.

[0006] Despite numerous research institutions and enterprises exploring synergistic solutions using multiple technologies, several technical drawbacks remain, including poor process compatibility, lack of standardization, and low resource utilization levels. Furthermore, the high proportion of small-scale, workshop-style recycling further increases environmental pressure, and issues such as insufficient purity of recycled silicon and significant silver loss are prominent. Therefore, overcoming the economic constraints and pollution control limitations imposed by the high energy consumption, high cost, and secondary pollution of conventional recycling processes is the core challenge for the industrialization of photovoltaic module recycling, and also an inevitable trend and urgent need to achieve a truly closed-loop photovoltaic industry and high-value resource utilization. Summary of the Invention

[0007] This invention addresses the problems of high energy consumption, high cost, easy breakage of silicon solar cells, and secondary pollution in the recycling process of photovoltaic modules. It proposes a low-energy dismantling and resource recycling method for photovoltaic modules. By using stepped short-time heating and peeling treatment of photovoltaic panels, the method can achieve efficient separation of glass, backsheet, and solar silicon solar cells of photovoltaic panels while significantly reducing heating energy consumption and avoiding pyrolysis pollution. Combined with cleaning with green composite organic solvents, clean and intact solar silicon solar cells can be recovered, which can also reduce secondary pollution and promote the green and circular development of the photovoltaic industry.

[0008] To achieve the above objectives, the present invention provides a low-energy-consumption resource recycling method for photovoltaic modules, comprising the step of performing gradient heating treatment on the photovoltaic panel for stripping the glass and backsheet to recover the solar silicon cells. The gradient heating treatment includes the following operations: The first step is to heat the double-glass photovoltaic panel at 300~600 ℃ for 30s~4min, then stop heating and quickly peel off one side of the glass; or heat the single-glass photovoltaic panel at 100~200 ℃ for 10s~1min, then stop heating and quickly peel off the back panel. The second step involves continuing to heat the photovoltaic panel after the first step at 400~700 ℃ for 10 s~2 min, then stopping the heating and quickly peeling off the remaining glass to obtain a structurally complete solar silicon cell.

[0009] This invention utilizes instantaneous heating and impact treatment to rapidly soften (rather than thermally decompose) the EVA adhesive layer to a viscous flow state within a very short time, drastically reducing interfacial adhesion. Immediate mechanical peeling is then performed, achieving low-damage and efficient separation of the glass, backsheet, and solar cell with complete solar silicon cells under low energy consumption. This overturns the traditional pyrolysis process, which relies on prolonged heating to thermally decompose EVA for separation. It transforms the separation mechanism from traditional chemical decomposition to physical softening, significantly reducing separation energy consumption and fundamentally avoiding thermal stress cracking of the silicon wafer and the generation of pyrolysis pollutants caused by prolonged heating. For example, for single-glass modules with fluorinated backsheets, the first step involves short-term heating at a lower temperature of 100-200°C, effectively softening the EVA and reducing backsheet adhesion, while preventing high-temperature decomposition of fluoropolymers and reducing the release of toxic gases such as hydrogen fluoride, thus achieving an environmentally friendly peeling process.

[0010] As a limitation of the above technical solution, the heating operation in both the first and second steps adopts the method of heating one side of the photovoltaic panel.

[0011] By heating one side of the photovoltaic panel and peeling off only the side that is being heated, effective separation and recycling can be achieved while significantly reducing heating energy consumption. After each heating step is stopped, the glass or backsheet on the directly heated side is quickly peeled off.

[0012] As a limitation of the above technical solution, the photovoltaic panel subjected to heat treatment is a whole photovoltaic panel.

[0013] As a limitation of the above technical solution, the stripping operation adopts a physical mechanical stripping method.

[0014] Mechanical peeling methods can employ various physical operation techniques, specifically: Initial separation operation: First, use tools such as scrapers, spatulas or skimmers to cut along the joint between the glass, backsheet or battery cell and the encapsulation adhesive layer, and break the interface adhesion by prying, scraping or cutting to form an initial separation gap; Subsequently, depending on the material and size of the component to be peeled off, one or more of the following methods are used for peeling: adsorption, clamping, and pushing. Auxiliary measures: During the stripping process, compressed air blowing and brush cleaning can be used to remove debris and residue generated during the stripping process in a timely manner to prevent them from interfering with subsequent operations.

[0015] As a limitation of the above technical solution, before the photovoltaic panel is subjected to gradient heating treatment, the photovoltaic module is first physically disassembled into an aluminum frame, junction box and photovoltaic panel.

[0016] As a limitation of the above technical solution, a hydraulic device is used to apply pressure to the aluminum frame to disassemble the aluminum frame; then, a knife-like device is used to cut into the silicone layer of the junction box, and the junction box is separated by prying and cutting.

[0017] The recycling method of the present invention can separate the glass, backsheet and solar silicon cells without crushing the photovoltaic module, ensuring that each component is efficiently and completely recycled and reused.

[0018] As an optimization of the above technical solution, the recycling method also includes a cleaning step of cleaning the solar silicon cell with a green composite organic solvent after obtaining the solar silicon cell to remove the residual EVA adhesive layer on the surface, so as to obtain a clean and complete solar silicon cell; preferably, the cleaning temperature is 40~70 ℃, the cleaning time is 10~30 min, and the cleaning step is supplemented by ultrasonic or mechanical stirring.

[0019] After obtaining solar silicon cells through gradient instantaneous heating and mechanical stripping, the cells can be further cleaned using green composite organic solvents. Because the softened state of EVA after heating is conducive to solvent penetration and diffusion, it creates key interface conditions for cleaning with green solvents, which can quickly and thoroughly remove the residual EVA adhesive layer on the surface, thereby obtaining clean and complete solar silicon cells and realizing a green recycling process.

[0020] As an optimization of the above technical solution, the green composite organic solvent includes a first component and a second component. The first component is selected from one of terpene solvents, carbonate solvents, or bio-based ester solvents; the second component is selected from one of ionic liquids, organic alcohol solvents, or polar aprotic solvents; the volume ratio of the first component to the second component is 1:4 to 4:1.

[0021] As an optimization of the above technical solution, the green composite organic solvent may be selected from any of the following combinations: (1) A mixed solvent of limonene and dimethyl carbonate, wherein the volume ratio of limonene to dimethyl carbonate is 1:1 to 3:1; (2) A mixed solvent of limonene and acetic choline solution, wherein the mass fraction of acetic choline solution is 60%~80% and the volume ratio of limonene to acetic choline solution is 3:1~1:1; (3) A mixed solvent of dimethyl carbonate and ethanol, wherein the volume ratio of dimethyl carbonate to ethanol is 2:1 to 1:2; (4) A mixed solvent of ethyl lactate and N-methylpyrrolidone, wherein the volume ratio of ethyl lactate to N-methylpyrrolidone is 3:1 to 1:1.

[0022] The green composite organic solvent used is a biodegradable and low-toxicity compound solvent, which opens up a clean and efficient recycling path for the recycling and reuse of battery cells, including low-damage stripping, green cleaning, and high-value recycling.

[0023] As an optimization of the above technical solution, the clean and intact solar silicon cells can be directly used as fully functional power generation units for the maintenance and repair of photovoltaic modules or the assembly of distributed power generation systems. They can also be used as high-quality raw materials for crushing and hydrometallurgical processing to recover silicon materials and precious metals such as silver and copper. Specifically, the recovered clean and intact solar silicon cells undergo electrical performance testing, and are sorted and targeted for resource recovery based on their photoelectric conversion efficiency retention rate (η): (A) Cells with η≥80% are directly used as fully functional power generation units for the maintenance and repair of photovoltaic modules or the assembly of distributed power generation systems; (B) Cells with η<80% are used as high-quality raw materials for crushing and hydrometallurgical processing to recover silicon materials and precious metals such as silver and copper.

[0024] Among them, the photoelectric conversion efficiency retention rate (η) = (the actual photoelectric conversion efficiency of the recycled cell / the nominal photoelectric conversion efficiency of the same type of cell) × 100%. Attached Figure Description

[0025] Figure 1 Basic structure of photovoltaic modules.

[0026] Figure 2 The glass obtained by separation in Example 1 of the present invention.

[0027] Figure 3 The battery cell and solder strip obtained by separating them in Example 1 of the present invention.

[0028] Figure 4 The battery cell, solder strip, and backplate obtained by separating the components in Embodiment 2 of the present invention.

[0029] Figure 5Comparative Example 2 uses existing pyrolysis methods to process the solar cells, solder ribbons, and backsheets obtained from the separation of single-glass photovoltaic modules. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods; the raw materials or test materials used are typical products purchased from the market, unless otherwise specified. The quantitative experiments in the following examples and comparative examples were all repeated three times, and the results were averaged.

[0032] like Figure 1 As shown, the structure of a photovoltaic (PV) module typically includes an aluminum frame, junction box, glass, solar silicon cells, a backsheet, and EVA encapsulation film. PV modules are divided into double-glass and single-glass modules. Double-glass PV modules generally consist of a backsheet glass, solar silicon cells, and glass layered and bonded together using EVA encapsulation film. Single-glass PV modules generally consist of a backsheet, solar silicon cells, and glass layered and bonded together using EVA encapsulation film. The solar silicon cells consist of multiple cells welded together at high temperatures using solder ribbons. The junction box is bonded to the back of the PV panel (all components except the aluminum frame and junction box are collectively referred to as the PV panel) via a silicone layer; that is, the junction box is bonded to the backsheet glass or one side of the backsheet. The aluminum frame surrounds the PV module, and the edges of the PV module are fitted into pre-set grooves in the aluminum frame and fixed with adhesive.

[0033] Low-energy resource recycling of photovoltaic modules involves first physically disassembling them into aluminum frames, junction boxes, and photovoltaic panels. Hydraulic devices can be used to apply pressure to the aluminum frames, causing them to detach under pressure. Then, blade-like tools are used to cut into the silicone layer of the junction box, separating it through prying and cutting. Hydraulic devices can include hydraulically driven frame removers, hydraulically assisted peeling devices, hydraulic crushing and sorting machines, portable hydraulic disassembly tools, and hydraulic-mechanical composite disassembly systems.

[0034] Then, the photovoltaic panels undergo gradient heating treatment, which specifically includes the following operations: The first step is to heat the double-glass photovoltaic panel at 300~600 ℃ for 30s~4 min, then stop heating and quickly peel off one side of the glass; or heat the single-glass photovoltaic panel at 100~200 ℃ for 10s~1 min, then stop heating and quickly peel off the back panel. The second step involves continuing to heat the photovoltaic panel after the first step at 400~700 ℃ for 10 s~2 min, then stopping the heating and quickly peeling off the remaining glass to obtain a structurally complete solar silicon cell.

[0035] For double-glass photovoltaic panels, the first step is to peel off one side of the glass, and the second step is to peel off the remaining glass on the other side. For single-glass photovoltaic panels, the first step is to peel off the backsheet, and the second step is to peel off the glass on the remaining side. The EVA adhesive layer covering the solar cell and any other encapsulation materials that may be attached are peeled off at the same time as the glass or backsheet, ultimately obtaining a complete solar silicon solar cell.

[0036] In the gradient heating process for photovoltaic panels, both heating steps involve placing the photovoltaic panel inside a heating device for single-sided heating. This heating device can include an oven, infrared heating, or a furnace. The photovoltaic panel is placed inside the heating device, and by designing the heat source direction, single-sided heating is achieved, softening the EVA adhesive layer. Then, the glass, backsheet, and solar cells are peeled off using mechanical forces such as scrapers, spatulas, or suction cups. The resulting solar silicon cells are then cleaned using a green composite organic solvent to obtain clean and intact cells.

[0037] The applicability of the above-mentioned recycling method mainly depends on whether the following two key technical conditions are met: 1. Structural integrity requirements: The basic integrity of the multi-layer composite structure of "glass / EVA / cell / EVA / backsheet (or glass)" must be maintained. The layers are not completely separated, and the interface softening and peeling can be achieved through the above-mentioned gradient heating.

[0038] 2. Operability requirements: The dimensions should facilitate single-sided heating and subsequent mechanical peeling operations. Generally, the size of any side of the fragment should not be less than 5 cm to ensure that the heating equipment (such as an infrared heater or hot air gun) can effectively heat the specific surface; the operator or robot arm should be able to grasp and fix it, and perform peeling actions such as prying with a scraper or adsorption with a suction cup.

[0039] Therefore, the recycling method of the present invention is particularly applicable to whole photovoltaic modules, and can also be used for photovoltaic modules that are in fragmented form (referring to irregularly sized blocks formed by mechanical cutting, breaking or fracture during the dismantling or pre-processing of photovoltaic modules).

[0040] Inapplicable situations are when photovoltaic modules are crushed into granules (e.g., side length less than 2 cm) or powder, their laminated structure is completely destroyed, making effective directional heating and layer-by-layer peeling impossible. In such cases, they can be processed separately using physical sorting methods such as sieving and wind separation.

[0041] Example 1

[0042] Resource recycling of double-glass photovoltaic modules.

[0043] First, take the double-glass photovoltaic panel with the aluminum frame and junction box already disassembled, and cut it into 10 cm × 10 cm pieces (cutting is done for laboratory convenience; in actual applications, cutting is not necessary). Clean the surface dust. Place the double-glass photovoltaic panel in an oven and heat one side of the glass by adjusting the direction of the hot air (400 ℃) outlet and maintain this temperature for 2 minutes. After stopping heating, quickly peel off the heated glass side mechanically using a spatula inserted and pried. Figure 2 The glass plate shown.

[0044] The second step involves placing the double-glass photovoltaic panel, with one side of the glass already peeled off, back into the oven. The heat source temperature (500 ℃) and direction are adjusted to heat the other glass side, and this temperature is maintained for 1 minute. After stopping heating, the glass, solar silicon cells, and solder ribbons are quickly peeled off to obtain the desired result. Figure 3 The battery cells shown.

[0045] After the photovoltaic panel undergoes gradient heat treatment, the separated solar silicon cells (excluding solder strips) are taken whole or fragmented and placed in a mixed solvent of limonene:dimethyl carbonate = 2:1 (volume ratio) at 60°C. o Ultrasonic cleaning was performed at C for 15 minutes. After cleaning, the solar cells were removed, rinsed with anhydrous ethanol, and dried. The residual EVA on the surface of the solar cells was completely removed, resulting in clean, intact solar silicon solar cells with no geometric damage.

[0046] The aforementioned green cleaning process completely eliminates the blurring caused by EVA residue on the surface of the solar cells, and the surface texture of the silicon wafers is clearly visible, providing an ideal interface for subsequent direct photoelectric performance testing or high-value recycling.

[0047] Example 2

[0048] Resource recycling of single-glass photovoltaic modules.

[0049] The first step is to cut the single-glass photovoltaic panel, which has already had its aluminum frame and junction box disassembled, into 10 cm × 10 cm pieces (cutting is done for laboratory convenience; in actual applications, cutting is not necessary), and clean the surface dust. Place the single-glass photovoltaic panel in an oven and heat the back panel side by adjusting the direction of the hot air (150 ℃) outlet, maintaining this temperature stably for 30 seconds. After stopping heating, quickly use a spatula to pry the back panel off mechanically, or use a suction cup to remove it, thus obtaining the desired result. Figure 4 The back panel shown.

[0050] Subsequently, the single-glass photovoltaic panel with the backsheet removed (at this point, the structure is: glass / EVA / cell) was placed in an oven, and the heat source temperature (500 ℃) and direction were adjusted to heat the glass surface, maintaining this temperature stably for 1 minute. After heating was stopped, the glass was quickly peeled off from the EVA / cell as a whole to obtain a structurally complete solar silicon cell.

[0051] The third step involves placing the obtained solar silicon cell in a mixed solvent of limonene and 70% choline acetate solution (volume ratio 2:1) and performing ultrasonic-assisted cleaning at 50 °C for 20 minutes. After cleaning, the cell is removed, rinsed with anhydrous ethanol, and dried. This step completely removes residual EVA from the cell surface, resulting in a clean, intact solar silicon cell with no geometrical damage.

[0052] Comparative Example 1

[0053] In summary, the low-energy-consumption resource recycling method for photovoltaic modules of this invention has pioneered a collaborative process chain of EVA softening through gradient instantaneous heating, mechanical stripping, and green composite solvent cleaning. This achieves efficient and low-damage recycling of intact solar silicon cells. Compared with traditional physical and pyrolysis methods, it not only significantly reduces separation energy consumption and avoids pyrolysis waste gas pollution, but also achieves low-energy consumption and greening of the separation process. Furthermore, by outputting high-value intermediate products, it creates a brand-new high-value model for the entire photovoltaic module recycling industry, demonstrating outstanding industrial application potential and market value.

[0054] Taking the existing pyrolysis method for treating double-glass photovoltaic modules as an example for comparison, referring to the common pyrolysis process in the industry: the photovoltaic panel is placed in a pyrolysis furnace and slowly heated to the target temperature (usually 450~500 ℃) at a rate of 5~10 ℃ / min, and kept at this temperature for more than 30 minutes to allow the EVA encapsulation adhesive layer to be fully pyrolyzed and carbonized. Then it is naturally cooled to room temperature, and then mechanical separation is attempted.

[0055] The first step is to take the double-glass photovoltaic panel with the aluminum frame and junction box already disassembled, cut it into 10 cm × 10 cm pieces, and clean the surface dust. Place the photovoltaic panel in a pyrolysis furnace and heat it from room temperature to 480°C at a rate of 5°C / min, and maintain the temperature at 480°C for 60 min. Then turn off the heat source and let it cool down with the furnace to below 80°C before taking it out.

[0056] The second step involves cooling the glass and then peeling it off using tools. Because the EVA has undergone pyrolysis and carbonization and has been exposed to high temperatures for an extended period, the peeled solar silicon cells are severely shattered and bent; all fragments are collected.

[0057] The third step involves immersing the collected battery cell fragments in the same mixed solvent as described above (limonene: dimethyl carbonate = 2:1), ultrasonically cleaning them at 60 °C for 20 min, and then rinsing and drying them with anhydrous ethanol.

[0058] Compare the processing energy consumption and processing results of Example 1 and Comparative Example 1.

[0059] The EVA removal rate was determined using a gravimetric method, reflecting the effectiveness of the cleaning step in removing the EVA adhesive layer. The specific procedure is as follows: (a) Calibration experiment of reference net weight (M0) This experiment was conducted to determine the mass of the solar cells when they were clean and free of residue, providing a denominator for subsequent calculations. At least three structurally intact solar cells were randomly selected from samples of the same batch that underwent the same gradient heating pretreatment as a baseline group; the mass of each solar cell before cleaning was measured and recorded as M. 1−ref The sample was placed in a 1:1 mixture of ethyl lactate and N-methylpyrrolidone and ultrasonically cleaned at 80 °C for 60 minutes. It was then rinsed with anhydrous ethanol and dried at 120 °C. After cleaning, the sample was thoroughly dried and weighed. The cleaning-drying-weighing cycle was repeated until the mass change of each sample between two consecutive weighings was less than 0.5 mg (i.e., constant weight was achieved). The arithmetic mean of the final constant weight values ​​of all reference group samples was calculated, and this mean was defined as the reference net weight M0 of the batch of solar cells.

[0060] (II) Removal rate (R) test experiment of the cleaning process to be tested This experiment was used to evaluate the single-cycle cleaning efficiency of the green solvent formulation of this invention. A new test sample was taken from the same batch, and its mass before cleaning was recorded as M1. This sample was then treated using the same cleaning process (limonene:dimethyl carbonate = 2:1, cleaning at 60°C for 20 min). After the process, the sample was thoroughly dried and its mass was recorded as M2. The removal rate was calculated as follows: The removal rate R of residual EVA by this cleaning process was calculated according to the following formula: .

[0061] Molecules (M1-M2): The measured mass reduction caused by this cleaning, i.e., the mass of EVA removed.

[0062] Denominator (M1-M0): The initial theoretical total mass of residual EVA on the surface of the test sample, calculated based on independent benchmark experiments.

[0063] Ratio (R): The percentage of the mass removed in this cleaning process relative to the initial theoretical total mass, i.e., the removal rate.

[0064] Method for determining total processing energy consumption: An electricity meter was used to directly measure the electrical energy consumed by the heating equipment (such as an oven or pyrolysis furnace) throughout the entire processing cycle (from the start of heating to the end of the set program). For Example 1, the total processing time was the sum of the first heating step (2 minutes) and the second heating step (1 minute) (excluding intermittent operation time); for Comparative Example 1, the total processing time was the entire process of heating from room temperature to 480 °C and holding at that temperature for 60 minutes. All measured energy consumption figures have deducted the equipment's standby base power consumption.

[0065] The comparison results between Example 1 and Comparative Example 1 are shown in Table 1 below.

[0066] Table 1. Comparison of processing energy consumption and processing results between Example 1 and Comparative Example 1

[0067] Conclusion: As shown in Table 1, under the premise of using the exact same green composite organic solvent for cleaning, this invention, through gradient instantaneous heating, demonstrates an overwhelming advantage over traditional pyrolysis processes in three core indicators: energy consumption (reduced by more than 76%), battery integrity (from fragments to intact), and the cleanliness of the final product (from >50% residue to >99% removal). This proves that the technical route of this invention, which replaces decomposition with softening, not only achieves low-energy stripping but, more importantly, creates an ideal interface that traditional methods cannot achieve for subsequent efficient green cleaning, forming a truly synergistic high-value recycling path.

[0068] Comparative Example 2 The existing pyrolysis method for treating single-glass photovoltaic modules is used as an example for comparison.

[0069] The first step involves cutting the single-glass photovoltaic panel, which has already had its aluminum frame and junction box removed, into 10 cm × 10 cm pieces and cleaning off the surface dust. The photovoltaic panel is then placed in a conventional pyrolysis furnace and heated to 480 ℃ at a rate of 5 ℃ / min, held at that temperature for 60 minutes, and then cooled with the furnace.

[0070] The second step, after cooling, is to attempt to peel off the backing plate. However, the backing plate becomes brittle due to the high temperature and adheres to the carbonized EVA, making complete peeling difficult. Figure 5 As shown.

[0071] The third step involved continuing to attempt to peel off the battery cells, which were severely fractured due to prolonged thermal stress.

[0072] Results: Traditional pyrolysis methods for processing single-glass modules also suffer from difficulties in backsheet separation and extremely low cell integrity, which contrasts sharply with the efficient and complete recycling effect of Embodiment 2 of this invention.

[0073] Comparative Example 3 To verify the effect of different solvents on the cleaning effect after gradient heating treatment.

[0074] In the first step, all experimental samples came from the same batch of double-glass photovoltaic modules. After disassembling the frame and junction box using the same steps, they were cut into 10 cm × 10 cm sizes. All samples first underwent the gradient heating treatment, the core of this invention: first, heating at 400℃ for 2 minutes to peel off one side of the glass, and then heating at 500℃ for 1 minute to peel off the other side of the glass, completing the mechanical separation of the glass from the solar cells and obtaining structurally intact solar silicon solar cells as the objects to be cleaned.

[0075] The second step involved placing all grouped samples in different solvents and performing ultrasonic-assisted cleaning at 60°C for 20 minutes.

[0076] The third step is to observe and record the cleaning effect, and the results are shown in Table 2 below.

[0077] The EVA removal rate was determined by gravimetric method, as above.

[0078] Cell integrity retention rate: This refers to the percentage of cell area without any new cracks or damage, calculated after cleaning and drying.

[0079] Qualitative observation of surface cleanliness: Record the surface condition under the naked eye and optical microscope.

[0080] Table 2. Cleaning effect of different solvents on residual EVA on solar silicon cells

[0081] Evidence of the synergistic effect of compounding: Compared with groups A and B and C, the cleaning efficiency of a single component (even a green solvent) is significantly lower than that of the compounding system, i.e., the EVA removal rate. This proves that the cleaning effect is synergistically enhanced by the compounding of solvents, thereby efficiently removing EVA.

[0082] Different composite organic solvent systems in groups D, E, and F all achieved excellent cleaning results with EVA removal rates >96%, significantly outperforming other green compound solutions (groups G and H). This demonstrates that the gradient heating softening combined with the green composite organic solvent recovery process creates an ideal recovery interface. All solvent systems used meet the core requirements of biodegradability and low toxicity, while also far exceeding the efficiency of traditional hazardous solvents (such as acetone and xylene), perfectly supporting the demand for both green practices and high-value utilization.

[0083] Comparative Example 4 To verify the effect of different heat treatment methods on solvent cleaning effect.

[0084] The first step involved taking retired double-glass photovoltaic modules from the same batch, removing the aluminum frames and junction boxes, and uniformly cutting them into 10cm × 10cm samples. Surface dust was then cleaned. The samples were randomly divided into three groups: Experimental Group 1: Gradient heating treatment according to the present invention was adopted. First, the sample was placed in a heating device, and one side of the glass was heated at 400°C for 2 minutes. After heating was stopped, the glass side was immediately peeled off with a tool. Then, the other side of the glass was heated at 500°C for 1 minute. After heating was stopped, the glass side was immediately peeled off to obtain a complete solar silicon cell.

[0085] Experimental Group 2: Traditional pyrolysis process was used. The sample was placed in a temperature-controlled pyrolysis furnace and heated from room temperature to 480°C at a rate of 5°C / min, and held at 480°C for 60 min to allow the EVA to be fully pyrolyzed and carbonized. The heat source was then turned off and the sample was cooled to below 80°C in the furnace before being removed. After cooling, the glass was peeled off and fragments of the solar silicon cell that were severely broken and bent due to prolonged high-temperature thermal stress were collected.

[0086] Experimental Group 3: Verifying the key influence of heating conditions on the final physical morphology of EVA. The sample was placed in a heating device and heated uniformly in a single stage: continuously heated at 280℃ (below the lower limit of this invention) for 10 min (significantly longer than the time specified in this invention). Under these conditions, the EVA softened as a whole, and the glass was then completely peeled off from the solar cell (the two remained bonded by the softened EVA). Subsequently, the bonded solar cell was carefully separated from the glass, yielding a solar silicon cell with a basically intact structure but a surface covered with a layer of softened EVA.

[0087] In the second step, experimental groups 1-3 adopted the same cleaning scheme, using a mixed solvent of limonene and dimethyl carbonate in a volume ratio of 2:1, and ultrasonically assisted cleaning at 60°C for 20 min. After cleaning, all groups were rinsed with anhydrous ethanol and dried under the same conditions.

[0088] Results of Experiment 1: After gradient heating, the EVA adhesive layer softened and remained intact, with a clear interface with the solar cell. After the above-mentioned unified cleaning, the EVA removal rate was >99%, the solar cell surface was clean, and the silicon wafer texture and metal grid lines were clearly visible.

[0089] Analysis revealed that instantaneous gradient heating rapidly brought EVA to a viscous flow state, achieving physical softening and interfacial debonding while largely preserving its polymer chain structure. In this state, EVA is easily penetrated, swollen, and peeled off by subsequent green solvents.

[0090] Results of Experiment Group 2: After prolonged high-temperature pyrolysis, the EVA adhesive layer carbonized into a black, hard residue that adhered tightly to the surface and interface of the battery cell fragments. After the aforementioned unified cleaning, most of the carbonized residue remained stubbornly attached. Image analysis showed that its surface coverage was >50%, indicating an extremely low equivalent EVA removal rate.

[0091] Traditional pyrolysis completely thermochemically decomposes and carbonizes EVA, destroying its molecular structure and forming chemically stable and physically tightly adhered carbonaceous residue. In this state, the substance is almost unresponsive to the same green solvent, leading to cleaning failure.

[0092] Results of Experiment Group 3: After a single-stage long-term heating at 280℃ for 10 minutes, the EVA adhesive layer transformed into a viscous, thick gel-like substance, with an blurred interface with the battery cell and physical embedding. After the above-mentioned uniform cleaning, a layer of gel-like residue still covered the surface, and the EVA removal rate was only about 70%.

[0093] While unoptimized low-temperature, long-term heating softens EVA and enables mechanical exfoliation, it fails to transform it into a form conducive to solvent action. This condition leads to uneven heating of EVA, resulting in partial thermal aging and localized cross-linking, forming a dense and highly adhesive viscoelastic gel. In this state, the EVA molecular chains are not sufficiently relaxed, resulting in low internal porosity and hindering effective solvent penetration and swelling, leading to incomplete cleaning.

[0094] Table 3. Effects of different heat treatment methods on solvent cleaning effect

[0095] Experimental conclusion: The instantaneous gradient heating softening treatment employed in this invention, compared to traditional long-term pyrolysis, produces a drastically different state in EVA, fundamentally determining its subsequent cleaning requirements. Furthermore, the gradient heating method of this invention is not merely for achieving interlayer separation; its core function is to transform EVA into a physical form that is easily and efficiently removed by subsequent green solvents, thus achieving synergy and continuity in the softening-stripping-cleaning process chain. This is both the intrinsic reason for the qualitative leap in the final recycling effect (intact, clean battery cells) compared to traditional pyrolysis, and the key mechanism behind its significant advancement.

[0096] In summary, the instantaneous heating shock treatment of this invention has significant advantages over traditional pyrolysis processes in terms of short processing time, low energy consumption, and high-efficiency separation. Combined with the cleaning of green composite organic solvents, clean and intact solar silicon cells are obtained, laying the foundation for subsequent high-value-added pathways. This forms a complete, green, and economical recycling process system with advantages for industrial promotion and is of great significance for the development and research of sustainable resource utilization technologies in the photovoltaic industry.

[0097] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for low-energy resource recycling of photovoltaic modules, characterized in that, The process includes a gradient heating treatment of the photovoltaic panel for peeling off the glass and recycling the solar silicon cells from the backsheet. This gradient heating treatment includes the following operations: The first step is to heat the double-glass photovoltaic panel at 300~600 ℃ for 30s~4min, then stop heating and quickly peel off one side of the glass; or heat the single-glass photovoltaic panel at 100~200 ℃ for 10s~1min, then stop heating and quickly peel off the back panel. The second step involves continuing to heat the photovoltaic panel after the first step at 400~700 ℃ for 10 s~2 min, then stopping the heating and quickly peeling off the remaining glass to obtain a structurally complete solar silicon cell.

2. The method for low-energy resource recycling of photovoltaic modules according to claim 1, characterized in that: Both the first and second heating operations involve heating one side of the photovoltaic panel.

3. The method for low-energy resource recycling of photovoltaic modules according to claim 1, characterized in that: The photovoltaic panel that has undergone heat treatment is a whole photovoltaic panel.

4. The method for low-energy resource recycling of photovoltaic modules according to claim 1, characterized in that: The stripping operation employs physical mechanical stripping methods.

5. The method for low-energy resource recycling of photovoltaic modules according to claim 1, characterized in that: Before the photovoltaic panel undergoes gradient heating treatment, the photovoltaic module is physically disassembled into an aluminum frame, junction box, and photovoltaic panel.

6. The method for low-energy resource recycling of photovoltaic modules according to claim 5, characterized in that: A hydraulic device is used to apply pressure to the aluminum frame to disassemble it; then, a knife-like tool is used to cut into the silicone layer of the junction box, and the junction box is separated by prying and cutting.

7. The method for low-energy resource recycling of photovoltaic modules according to claim 1, characterized in that, The method also includes a cleaning step after obtaining the solar silicon cell, using a green composite organic solvent to clean the solar silicon cell and remove the residual EVA adhesive layer on the surface, so as to obtain a clean and complete solar silicon cell; preferably, the cleaning temperature is 40~70 ℃, the cleaning time is 10~30 min, and the cleaning step is supplemented by ultrasonic or mechanical stirring.

8. The method for low-energy resource recycling of photovoltaic modules according to claim 7, characterized in that, The green composite organic solvent includes a first component and a second component. The first component is selected from one of terpene solvents, carbonate solvents, or bio-based ester solvents. The second component is selected from one of ionic liquids, organic alcohol solvents, or polar aprotic solvents. The volume ratio of the first component to the second component is 1:4 to 4:

1.

9. The method for low-energy resource recycling of photovoltaic modules according to claim 8, characterized in that, The green composite organic solvent may be selected from any of the following combinations: (1) A mixed solvent of limonene and dimethyl carbonate, wherein the volume ratio of limonene to dimethyl carbonate is 1:1 to 3:1; (2) A mixed solvent of limonene and acetic choline solution, wherein the mass fraction of acetic choline solution is 60%~80% and the volume ratio of limonene to acetic choline solution is 3:1~1:1; (3) A mixed solvent of dimethyl carbonate and ethanol, wherein the volume ratio of dimethyl carbonate to ethanol is 2:1 to 1:2; (4) A mixed solvent of ethyl lactate and N-methylpyrrolidone, wherein the volume ratio of ethyl lactate to N-methylpyrrolidone is 3:1 to 1:

1.

10. The method for low-energy resource recycling of photovoltaic modules according to any one of claims 1 to 9, characterized in that: The clean and intact solar silicon cells can be directly used as fully functional power generation units for the maintenance and repair of photovoltaic modules or the assembly of distributed power generation systems. They can also be used as high-quality raw materials for crushing and hydrometallurgical processing to recover silicon materials and precious metals such as silver and copper.

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