Method for recycling EVA (ethylene vinyl acetate) and silver of waste photovoltaic panel laminated part

Abstract

The invention discloses a method for recycling EVA and silver of a waste photovoltaic panel laminated piece, which comprises the following steps: S1, removing an aluminum frame and a junction box, and stripping a back plate; s2, EVA on the back of the laminated part is removed; s3, EVA on the front face of the laminated piece is removed; and S4, recovering the silver electrode of the silicon battery piece. The invention provides the method for accurately controlling the EVA (Ethylene Vinyl Acetate) at the front part and the back part of the photovoltaic laminated piece to be cleanly and quickly separated and separating the silver electrode on the silicon battery piece by using laser as a main process, chemical reagents are not needed in the whole process, crushing and sorting are not needed, and the silver with high additional value and the complete silicon battery piece are obtained; the method has the characteristic of efficient and accurate utilization of energy. According to the method, the non-destructive rapid recovery of EVA is realized, and meanwhile, a silver recovery method with low environmental influence is adopted, so that great convenience is provided for subsequent efficient remanufacturing, and considerable circular economic benefits can be brought.

Description

Technical Field

[0001] The invention belongs to the technical field of photovoltaic panel component recycling, and in particular relates to a method for recycling EVA and silver of waste photovoltaic panel laminates. Background Art

[0002] After the aluminum alloy frame is removed from the currently retired conventional photovoltaic modules, the front to the bottom of the photoelectric conversion module is: tempered glass, upper EVA film, silicon cell, back EVA film and backboard. At present, the treatment method of EVA in photovoltaic modules mainly adopts heat treatment and chemical dissolution methods to directly remove or weaken its adhesion. In addition, there are also cold treatment methods, such as CN117816699 A mentions the treatment method of using liquid nitrogen immersion modification. EVA pyrolysis treatment usually produces volatile oil and gas components, which requires further use of tail gas combustion and filtration purification facilities, while simple hot knife heating separation brings about the problem of EVA residue on glass and silicon cells. The crushing method used after liquid nitrogen treatment faces the difficulties of component screening, valuable material silicon, and glass regeneration enrichment rate improvement. The chemical treatment method of EVA has shifted from the early high environmental impact organic reagents such as trichloroethylene, toluene, and hexane to inorganic reagents such as KOH-ethanol and nitric acid, but it still faces the problem of reagent recycling and waste liquid treatment. The above methods all use the method of decomposing or destroying the molecular structure of EVA to achieve the purpose of separation, and fail to efficiently recycle EVA.

[0003] The recovery method of silver in photovoltaic modules usually uses nitric acid, sulfuric acid, methanesulfonic acid and other methods to dissolve the silver on the silicon cell, and then further electrolytically refine it. In the public patent CN 117339981 A, low-melting-point NaOH-KOH is used to etch the silicon cell for a very short time to directly obtain silver. This method is an efficient and simple technology in the wet process. The latest public patent CN 118326166 A uses citric acid, lactic acid, tartaric acid, malic acid, acetic acid and other low-environmental-impact reagents to extract silver. The article Recovery of Silver From Waste Crystalline Silicon Photovoltaic Cells by Wire Explosion proposes a physical decomposition method of extracting silver by wire explosion using a 15 kV voltage, but the silver extraction rate is low and needs to be continuously optimized. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for recycling EVA and silver from waste photovoltaic panel laminates.

[0005] The method for recycling EVA and silver from waste photovoltaic panel laminates of the present invention comprises the following steps: S1. Remove the aluminum frame and junction box, and peel off the back panel; S2. Remove the EVA from the back of the laminate; S3. Removing the EVA on the front side of the laminate; S4. Recycle the silver electrodes of silicon cells.

[0006] The specific steps of S1 are: using a frame remover to remove the aluminum frame and junction box to obtain a photovoltaic panel laminate, and then using a hot air gun to heat and soften the back panel and remove it. The air outlet of the hot air gun is arranged in a multi-air outlet rectangular array, the temperature of the hot air gun is 500°C, and when using the hot air gun, the gun muzzle is 5 cm away from the back panel.

[0007] The frame removal machine comprises an upper frame and a lower frame, the photovoltaic panel laminate is placed between the upper frame and the lower frame, the upper frame is provided with a suction cup and a blade, the lower frame is provided with a swing rod and a frame shovel, the blade is used to remove the junction box, and the frame shovel is used to remove the aluminum frame.

[0008] The specific steps of S2 are: using a pulsed fiber laser to heat the transparent EVA bonded to the photovoltaic cell panel on the back of the laminate, and when the EVA becomes soft and does not bubble, and the color of the silicon cell does not deepen, the EVA with greatly weakened bonding strength is peeled off.

[0009] The energy density range of the pulsed fiber laser is 0.2 MW / cm 2 -2 MW / cm 2 , the pulse width was set to 4 ns, the frequency range was 20 kHz-500 kHz, and the scanning speed was set to 1 m / s.

[0010] The specific steps of S3 are: using a Q-switched Nd:YAG pulse laser to heat the EVA adhesive layer bonded to the glass plate on the front side of the laminate, when the bonding force between the glass plate-EVA adhesive layer-silicon cell is reduced to the point where the glass plate becomes loose, using a scraper to peel off the EVA film on the glass plate in the step support.

[0011] The laminate is placed on the upper step and upper slope of the step support, the width of the upper step matches the thickness of the silicon cell, the glass plate and the EVA film are located outside the upper step, and a buffer is installed on the lower step.

[0012] The wavelength of the Q-switched Nd:YAG pulse laser is 500 nm-800 nm, and the energy density is 0.5 J / cm 2 -0.7 J / cm 2 , scanning speed is 10-30 mm / s.

[0013] The specific steps of S4 are: washing the silicon cell with pure water and placing it horizontally in a pure water tank, with the highest water level not higher than 1 mm above the cell surface, setting an XY gantry mechanism above the tank, locating the position of the silver electrode in combination with an image recognition system, scanning the silver electrode with an infrared continuous laser to make the silver electrode fall off the silicon cell, and recovering the silver particles or silver powder that fall off in the tank with a vacuum filter.

[0014] The infrared continuous laser has a wavelength of 1070±5 nm and an average power of 75 W.

[0015] The beneficial effect of the present invention is that the present invention provides a method for accurately controlling the clean and rapid separation of the front and back EVA of photovoltaic laminates and separating the silver electrodes on silicon cells with laser as the main process. The whole process does not require chemical reagents or crushing and sorting, and obtains high-value-added silver and complete silicon cells, which has the characteristics of efficient and accurate energy utilization. The non-destructive and rapid recovery of EVA is achieved, and a silver recovery method with low environmental impact is adopted, which provides great convenience for the subsequent efficient remanufacturing of photovoltaic panels and can bring considerable circular economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a flow chart of recycling EVA and silver from waste photovoltaic panel laminates.

[0017] Figure 2 It is a structural schematic diagram of the frame dismantling machine of the present invention.

[0018] Figure 3 It is a structural schematic diagram of an upper frame in a frame removal machine of the present invention.

[0019] Figure 4 It is a structural schematic diagram of the lower frame in the frame removal machine of the present invention.

[0020] Figure 5 It is a structural schematic diagram of the step support of the present invention.

[0021] Figure 6 It is a schematic diagram of the internal structure of the step support of the present invention.

[0022] Reference numerals: Peeling back plate 1; removing EVA from the back of laminate 2; removing EVA from the front of laminate 3; recovering silver electrode of silicon cell 4; de-framing machine 5; upper frame 6; lower frame 7; photovoltaic panel 8; upper support plate 9; suction cup 10; blade 11; silicone remover box 12; lower support plate 13; turntable 14; frame shovel 15; guide groove 16; limit column 17; swing rod 18; step support 19; upper inclined surface 20; upper step 21; lower step 22, scraper 23; inlet 24; rotating shaft 25. DETAILED DESCRIPTION

[0023] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0024] like Figure 1 As shown, the method for recycling EVA and silver from waste photovoltaic panel laminates of the present invention comprises the following steps: S1. Remove the aluminum frame and junction box, and peel off the back panel; use a frame remover to remove the aluminum frame and junction box to obtain a photovoltaic panel laminate, and then use an industrial robot or a hot air gun to heat and soften the back panel. The air outlet of the hot air gun is arranged in a multi-air outlet rectangular array, so that hot air can be blown to various positions of the back panel at the same time, and the back panel can be softened quickly. The temperature of the hot air gun is 500°C. When using the hot air gun, the muzzle is vertical to the back panel and 5 cm away from the back panel. The heating area is controlled within 10 seconds, and then the back panel is peeled off with pliers, leaving a laminate with EVA on the back.

[0025] The use of a hot air gun to heat and remove the back panel is mainly based on the physical principle of high temperature softening. Then when the mechanical force applied is greater than the bonding force, the back panel can be peeled off.

[0026] S2. Remove the EVA on the back of the laminate; use a pulsed fiber laser to heat the transparent EVA on the back of the laminate bonded to the photovoltaic panel. The energy density of the pulsed fiber laser is in the range of 0.2 MW / cm 2 -2 MW / cm 2 , the pulse width is set to 4 ns, the frequency range is 20 kHz-500 kHz, and the scanning speed is set to 1 m / s. When the EVA becomes soft and does not bubble, and the color of the silicon battery cell does not darken, the heating is ended, and the entire EVA film with greatly weakened adhesion is removed manually or with an automatic scraper device and recycled.

[0027] S3. Remove the EVA on the front side of the laminate; the laminate is placed on a step support 19, the step support 19 includes an upper step 21, an upper inclined surface 20 and a lower step 22, the laminate is placed on the upper step 21 and the upper inclined surface 20, the width of the upper step 21 matches the thickness of the silicon cell, the glass plate and the EVA film are located outside the upper step 21, and a buffer is installed on the lower step 22, the buffer is a spring or a cushion of flexible material.

[0028] The EVA film layer of the laminate bonded to the glass plate on the front side was heated by a Q-switched Nd:YAG pulsed laser with a wavelength of 500 nm-800 nm and an energy density of 0.5 J / cm 2 -0.7 J / cm 2, the scanning speed is 10-30 mm / s. When the laser is irradiated, the heat is concentrated on the contact adhesive layer between the silicon cell and EVA through the glass, generating thermal expansion, thermal vibration and photochemical effects, destroying the covalent bond between the vinyl group in the EVA film and the surface of the adherend, and separating the EVA from the silicon cell. When the bonding force is reduced to the point where the glass plate becomes loose, the glass plate and the EVA film will separate from the silicon cell and the upper step 21, and fall along the lower slope to the lower step 22. Since the surface of the lower step 22 is equipped with a buffer, the glass plate will be buffered when it slides down, so that the glass plate will not be damaged. A scraper is also provided in the step support, and the EVA film on the glass plate is removed by the scraper during the falling process.

[0029] The advantage of removing the EVA film by heating the EVA with a laser is that the heat is precisely concentrated on the silicon cell sheet at the bottom, so that the EVA and the silicon cell sheet separate at the contact part, unlike other heating methods that diffusely heat the entire area outside the contact layer.

[0030] S4. Recover the silver electrode of the silicon cell. Wash the silicon cell from which the glass plate has been separated with pure water and place it horizontally in a pure water tank. The highest water level is not higher than 1 mm above the surface of the cell. An XY gantry mechanism is set above the tank. The XY gantry mechanism is equipped with an image recognition system and an infrared continuous laser. The image recognition system is used to locate the position of the silver electrode. The infrared continuous laser is used to scan the silver electrode on the silicon cell. The wavelength of the infrared continuous laser is 1070 ± 5 nm and the average power is 75W. The silver electrode is made to fall off the silicon cell. The silicon cell that has been separated from the silver electrode is washed again in the tank. Finally, the silver particles or silver powder that have fallen off in the tank are recovered by a vacuum filter.

[0031] Infrared continuous laser is used to separate the silver electrode because silver reflects infrared, making it difficult for heat to concentrate on the silver in large quantities. If other types of lasers are used, ablation will occur, causing the silicon cell contacting the silver to fall off, affecting the purity of the collected silver.

[0032] The following is an introduction to the structure of the frame removal machine and its specific working process. Figure 2-Figure 5As shown, the frame removal machine includes an upper frame 6 and a lower frame 7. The upper frame 6 is located above the lower frame 7, and the height of the legs of the upper frame 6 is higher than that of the lower frame 7. The top of the upper frame 6 is an upper support plate 9. Two suction cups 10 are arranged at intervals on the lower surface of the upper support plate 9. The suction cups 10 are installed on the upper support plate 9 through a telescopic rod or a hydraulic cylinder. A silicone remover box 12 is installed between the two suction cups 10. Acetic acid or acetone is placed in the silicone remover box 12. Inward nozzles are installed on the four sides of the bottom of the silicone remover box 12 for spraying silicone remover on the silicone between the junction box and the back plate. The length and width of the silicone remover box 12 are greater than the length and width of the junction box. The silicone remover box 12 is installed on the lower surface of the upper support plate 9 through a telescopic rod. A blade 11 is arranged on one side of the silicone remover box 12. The blade 11 is installed on the lower surface of the upper support plate 9 through a hydraulic cylinder and a telescopic rod. The hydraulic cylinder is vertically installed on the lower surface of the upper support plate 9. The piston of the hydraulic cylinder is connected to the telescopic rod. The telescopic rod is horizontally arranged, and the free end of the telescopic rod is fixedly connected to the blade 11. The tip of the blade 11 faces the silicone remover box 12.

[0033] First, use the nozzle on the silicone remover box 12 to spray acetic acid or acetone to the bottom edge of the junction box. When the silicone at the bottom of the junction box softens, use the blade 11 to scrape off the junction box.

[0034] A collecting bucket is placed on one side of the lower frame 7 to collect the scraped junction boxes.

[0035] A lower support plate 13 is arranged on the top of the lower frame 7, a turntable 14 is installed in the middle of the lower support plate 13, the bottom of the turntable 14 is connected to the motor, and four rotating shafts arranged in a circular array are arranged on the top edge of the turntable 14. The bottom of each rotating shaft is connected to the turntable through a bearing, and the top of each rotating shaft is connected to a swing rod 18 through a bearing. The four swing rods 18 extend to the four sides of the lower support plate 13 respectively, and the four swing rods 18 are symmetrically arranged in pairs. A frame shovel 15 is installed on the free end of each swing rod 18 through a rotating shaft. The cross section of the frame shovel 15 is a right triangle, and the blade of the frame shovel 15 is located at the top outer end. Guide grooves 16 are arranged on both sides of each swing rod 18, that is, the swing rod 18 is located in the guide grooves 16. When the motor is started, the motor drives one end of the four swing rods 18 to make a circular motion through the turntable, and the other end of the four swing rods 18 drives the frame shovel 15 to move along the guide groove 16, so that the laminate placed above it can be de-framed. Limiting columns 17 are provided at the four corners of the top of the lower frame 7 . The height of the limiting columns 17 is the same as the highest height of the frame shovel 15 . The limiting columns 17 are used to limit the placement height of the laminate without affecting the movement of the frame shovel 15 .

[0036] The process of removing the aluminum frame and junction box from the laminate using a de-framing machine is as follows.

[0037] First, place the waste photovoltaic panel on the limit column 17 between the upper frame 6 and the lower frame 7, so that the junction box corresponds to the silicone remover box 12, start the suction cup 10 to suck the back plate of the waste photovoltaic panel to prevent it from moving, and then use the nozzle in the silicone remover box 12 to spray acetic acid or acetone on the bottom of the junction box. After a while, when the silicone softens, move the blade 11, use the blade 11 to scrape off the junction box, and send the junction box to a collection bucket on one side. Then start the motor, and use the turntable 14 to make the four swing rods 18 start to swing. The four swing rods 18 move outward along their respective guide grooves 16 in turn, so that the frame shovel 15 scrapes off the aluminum frames on the four sides of the laminate.

[0038] The following describes the process of removing the EVA film on the glass plate by a scraper on a step support. Figure 5-Figure 6 As shown, an entrance is provided between the lower inclined surface of the step support 19 and the upper step 21, and a scraper 23 is installed at the entrance. The scraper 23 is triangular, and the blade of the scraper 23 is located at the entrance. When the glass plate-EVA film-silicon cell is placed on the upper step 21, and the EVA film layer bonded to the glass plate on the front side of the laminate is irradiated by the Q-switched Nd:YAG pulse laser, the scraper 23 is located between the glass plate and the EVA film. The glass plate drives the EVA film to descend, and the scraper 23 separates the two. The EVA film enters the interior of the step support 19 through the entrance 24 and contacts the rotating shaft 25. A motor is connected to one end of the rotating shaft 25, and the motor drives the rotating shaft 25 to rotate. When the EVA film contacts the rotating shaft, the EVA film is wound around the rotating shaft 25, thereby separating the glass plate and the EVA film.

[0039] Example 1

[0040] Use an automatic frame removal machine to remove the aluminum frame and junction box of the waste photovoltaic laminate. Heat the laminate backsheet with a hot air gun and peel off the backsheet with pliers; The energy density of the pulsed fiber laser was set to 0.6 MW / cm 2 , the frequency was set to 500 kHz, the back of the laminate was scanned at a speed of 1 m / s, and after completion, the EVA was peeled off with a scraper; The laminate was placed vertically on a step support and the wavelength of the Q-switched Nd:YAG pulse laser was set to 530 nm and the energy density to 0.7 J / cm 2 , the scanning speed is 25 mm / s. When the glass becomes loose, the glass plate and the EVA film are separated from the upper step and fall on the lower step. Then the EVA film on the glass plate is peeled off with an automatic scraper device; After the silicon cell was cleaned with pure water, it was placed horizontally in a pure water tank with the water level 0.5 mm above the cell surface. An XY gantry mechanism was set above the tank. The silver electrode on the silicon cell was scanned by infrared continuous laser. The wavelength of the infrared continuous laser was 1070 nm and the average power was 75 W. After the silver on the silicon cell fell off, the silicon cell that had been separated from the silver electrode was cleaned again in the tank, and finally the silver that fell off in the tank was recovered by a vacuum filter. Quantitative analysis using energy dispersive X-ray spectroscopy found that the silver remaining on the silicon cell was less than 1%, that is, more than 99% of the silver had been recovered.

[0041] Example 2

[0042] The difference between the recycling method of this embodiment and the above-mentioned embodiment 1 is that:

[0043] During the EVA recovery process on the back of the laminate, the energy density of the pulsed fiber laser was set at 0.2 MW / cm 2 , the frequency is set to 500 kHz, the scanning speed is 1 m / s, and after completion, the EVA is peeled off with a scraper. Its characteristic is that as the energy density decreases, dark powder is not easy to be produced on the EVA and silicon battery sheet.

[0044] Example 3

[0045] The difference between the recycling method of this embodiment and the above-mentioned embodiment 1 is that: During the EVA recovery process on the back of the laminate, the energy density of the pulsed fiber laser was set at 1.0 MW / cm 2 , the frequency is set to 20 kHz, the scanning speed is 1 m / s. After completion, the EVA is peeled off with a scraper combined with tweezers. Its characteristics are that after increasing the energy density and reducing the frequency, almost no powder is generated in the EVA and silicon battery sheets, but the peeling force applied becomes larger.

[0046] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0047] Although the above embodiments have been shown and described, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those of ordinary skill in the art are all within the scope of protection of the present invention.

Claims

1. A method for recycling EVA and silver from waste photovoltaic panel laminates, characterized in that: The following steps are involved: S1. Remove the aluminum frame and junction box, and peel off the back panel; S2. Remove the EVA from the back of the laminate; S3. Removing the EVA on the front side of the laminate; S4. Recycle the silver electrodes of silicon cells.

2. The method for recycling EVA and silver from waste photovoltaic panel laminates according to claim 1, characterized in that: The specific steps of S1 are: using a frame remover to remove the aluminum frame and the junction box to obtain a photovoltaic panel laminate, and then using a hot air gun to heat and soften the back panel and remove it. The air outlet of the hot air gun is arranged in a multi-air outlet rectangular array, and the size of the multi-air outlet matches the size of the back panel. The temperature of the hot air gun is 500°C, and the muzzle is 5 cm away from the back panel.

3. The method for recycling EVA and silver from waste photovoltaic panel laminates according to claim 2, characterized in that: The frame removal machine comprises an upper frame and a lower frame, the photovoltaic panel laminate is placed between the upper frame and the lower frame, the upper frame is provided with a suction cup and a blade, the lower frame is provided with a swing rod and a frame shovel, the blade is used to remove the junction box, and the frame shovel is used to remove the aluminum frame.

4. The method for recycling EVA and silver from waste photovoltaic panel laminates according to claim 1, characterized in that: The specific steps of S2 are: using a pulsed fiber laser to heat the transparent EVA bonded to the photovoltaic cell panel on the back of the laminate, and when the EVA becomes soft and does not bubble and the color of the silicon cell does not deepen, the EVA is peeled off.

5. The method for recycling EVA and silver from waste photovoltaic panel laminates according to claim 4, characterized in that: The energy density range of the pulsed fiber laser is 0.2 MW / cm 2 -2 MW / cm 2 , the pulse width was set to 4 ns, the frequency range was 20 kHz-500 kHz, and the scanning speed was set to 1 m / s.

6. The method for recycling EVA and silver from waste photovoltaic panel laminates according to claim 1, characterized in that: The specific steps of S3 are: using a Q-switched Nd:YAG pulse laser to heat the EVA adhesive layer of the glass plate bonded to the front side of the laminate placed on the step support, and removing the EVA film on the glass plate with a scraper in the step support.

7. The method for recycling EVA and silver from waste photovoltaic panel laminates according to claim 6, characterized in that: The laminate is placed on the upper step and upper slope of the step support, the width of the upper step matches the thickness of the silicon cell, the glass plate and the EVA film are located outside the upper step, and a buffer is installed on the lower step.

8. The method for recycling EVA and silver from waste photovoltaic panel laminates according to claim 6, characterized in that: The wavelength of the Q-switched Nd:YAG pulse laser is 500 nm-800 nm, and the energy density is 0.5 J / cm 2 -0.7 J / cm 2 , scanning speed is 10-30 mm / s.

9. The method for recycling EVA and silver from waste photovoltaic panel laminates according to claim 1, characterized in that: The specific steps of S4 are: washing the silicon cell with pure water and placing it horizontally in a pure water tank, with the highest water level not higher than 1 mm above the cell surface, setting an XY gantry mechanism above the tank, locating the position of the silver electrode in combination with an image recognition system, scanning the silver electrode with an infrared continuous laser to make the silver electrode fall off the silicon cell, and recovering the silver particles or silver powder that fall off in the tank with a vacuum filter.

10. The method for recycling EVA and silver from waste photovoltaic panel laminates according to claim 8, characterized in that: The infrared continuous laser has a wavelength of 1070±5 nm and an average power of 75 W.

Images