Waste photovoltaic panel pyrolysis nondestructive recovery system and method

Abstract

The invention provides a waste photovoltaic panel pyrolysis nondestructive recovery system and method, and relates to the technical field of photovoltaic panel pyrolysis, the system comprises a pretreatment unit, a mechanical treatment unit and a chemical treatment unit, the pretreatment unit is used for dismounting an aluminum frame, a junction box and a back plate on a waste photovoltaic panel; the mechanical treatment unit comprises a low-temperature pyrolyzing furnace and a cutting machine which are connected with each other, the low-temperature pyrolyzing furnace is connected with the pretreatment unit and is used for softening an EVA adhesive film on the waste photovoltaic panel, and the cutting machine is used for cutting the softened EVA adhesive film so as to separate a glass sheet from a battery piece; the chemical treatment unit comprises an acid-base treatment module and an electrochemical recovery module which are connected, the acid-base treatment module is connected with the cutting machine and used for recovering aluminum back electrodes on the battery pieces, and the electrochemical recovery module is used for electrolyzing and recovering silver electrodes on the battery pieces to obtain silicon wafers. According to the invention, nondestructive recovery of the silicon wafer can be realized, the recovered silicon wafer can be directly reused for photovoltaic panel production, and the production cost of the photovoltaic panel is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic panel pyrolysis, and in particular to a system and method for non-destructive pyrolysis recovery of waste photovoltaic panels. Background Art

[0002] Photovoltaic modules typically consist of an aluminum frame, junction box, tempered glass, EVA-coated crystalline silicon cells, and a TPT backsheet. After retirement, the glass, aluminum, silver, and silicon components within these modules offer significant recycling value. However, the recycling process often presents the challenge of delaminating the modules, specifically removing the EVA film.

[0003] In order to achieve the stripping of EVA film, the relevant technologies mainly use physical separation method, chemical solvent method and thermal decomposition method. Among them, the thermal decomposition method has the advantages of high recovery efficiency, high material purity, and suitability for industrial production compared with the other two methods. However, this method usually requires the waste photovoltaic panels to be crushed before thermal decomposition, which is not conducive to the complete recovery of silicon wafers, and increases the cost of using recycled silicon wafers to re-produce photovoltaic panels. Summary of the Invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0005] To this end, an embodiment of one aspect of the present invention proposes a pyrolysis and lossless recycling system for waste photovoltaic panels. The pyrolysis and lossless recycling system for waste photovoltaic panels can achieve lossless recycling of silicon wafers. The recycled silicon wafers can be directly reused in photovoltaic panel production, reducing the production cost of photovoltaic panels.

[0006] Another embodiment of the present invention provides a method for lossless recycling of waste photovoltaic panels by pyrolysis.

[0007] According to an embodiment of the present invention, a pyrolysis and lossless recovery system for waste photovoltaic panels includes a pretreatment unit, a mechanical treatment unit and a chemical treatment unit. The pretreatment unit is used to remove the aluminum frame, junction box and backboard on the waste photovoltaic panels; the mechanical treatment unit includes a connected low-temperature pyrolysis furnace and a cutting machine, the low-temperature pyrolysis furnace is connected to the pretreatment unit and is used to soften the EVA film on the waste photovoltaic panels, and the cutting machine is used to cut the softened EVA film to separate the glass sheet from the battery sheet; the chemical treatment unit includes a connected acid-base treatment module and an electrochemical recovery module, the acid-base treatment module is connected to the cutting machine, the acid-base treatment module is used to recover the aluminum back electrode on the battery sheet, and the electrochemical recovery module is used to electrolytically recover the silver electrode on the battery sheet to obtain silicon wafers.

[0008] According to the waste photovoltaic panel pyrolysis lossless recycling system of the embodiment of the present invention, the pre-treatment unit receives the recycled waste photovoltaic panels and first removes the aluminum frame, junction box and back panel on the waste photovoltaic panels, so that the remaining parts of the waste photovoltaic panels can enter the mechanical processing unit for further processing. In the mechanical processing unit, the low-temperature pyrolysis furnace can soften the EVA film on the remaining parts of the waste photovoltaic panels, and the cutting machine can separate the complete glass sheets from the battery sheets by cutting the softened EVA film. At this time, the separated complete glass sheets are recycled and reused, and the complete battery sheets are continued to be sent to the chemical treatment unit, and under the action of the alkali solution in the acid-base treatment module The aluminum back electrode on the battery cell is dissolved and then recovered by precipitation through an acidification process. After this operation, an intermediate product of the battery cell is obtained. The intermediate product is placed in an electrochemical recovery module for electrolytic recovery of the silver electrode to obtain a complete silicon wafer. That is to say, the present invention combines pyrolysis stratification and chemical treatment technology to remove the back panel and glass while keeping the photovoltaic panel intact, and clean up the aluminum back electrode, silver wire and other attachments on the recovered battery cell to achieve lossless recovery of the silicon wafer. Therefore, compared with related technologies, the present invention can achieve lossless recovery of silicon wafers, and the recovered silicon wafers can be directly reused in photovoltaic panel production, reducing the production cost of photovoltaic panels.

[0009] In some embodiments, the pretreatment unit includes a disassembly machine and a mechanical stripping machine connected to each other. The disassembly machine is used to remove the aluminum frame and junction box on the waste photovoltaic panels. The mechanical stripping machine is connected to the low-temperature pyrolysis furnace and is used to strip the backboard on the waste photovoltaic panels.

[0010] In some embodiments, the low-temperature pyrolysis furnace is provided with a heat source inlet, which is adapted to communicate with a flue of a coal-fired power plant so that the flue gas of the coal-fired power plant provides a heat source for the low-temperature pyrolysis furnace.

[0011] In some embodiments, the recovery system also includes a flue gas mixer, which is provided with a high-temperature flue gas inlet, a low-temperature flue gas inlet and a flue gas outlet. The high-temperature flue gas inlet is connected to the flue between the economizer and the denitrification system of the coal-fired power plant, the low-temperature flue gas inlet is connected to the flue between the air preheater and the electrostatic precipitator system of the coal-fired power plant, and the flue gas outlet is connected to the heat source inlet.

[0012] In some embodiments, the mechanical processing unit is provided with a pyrolysis gas outlet, and the pyrolysis gas outlet is used to discharge the pyrolysis gas in the low-temperature pyrolysis furnace and the cutting machine;

[0013] The recovery system further includes a gas purification unit, which is in communication with the pyrolysis gas outlet to purify the pyrolysis gas.

[0014] In some embodiments, the gas purification unit includes a cyclone dust collector, an activated carbon adsorption tower, and a defluorination module connected in sequence, wherein the cyclone dust collector is connected to the pyrolysis gas outlet and is used to filter dust in the pyrolysis gas, the activated carbon adsorption tower is used to adsorb adsorbable impurities in the pyrolysis gas, and the defluorination module is used to remove fluorides in the pyrolysis gas to obtain purified combustible gas;

[0015] The defluorination module is suitable for being connected to the boiler furnace of a coal-fired power plant so as to introduce the combustible gas for combustion assistance.

[0016] In some embodiments, the chemical treatment unit further includes a solvent stripping module, which is connected between the acid-base treatment module and the electrochemical recovery module. The solvent stripping module is provided with an organic solvent for dissolving residual EVA film on the battery cell.

[0017] In some embodiments, the recycling system also includes a silicon wafer post-processing unit, which includes a connected polishing machine and a silicon wafer detection module. The polishing machine is connected to the electrochemical recovery module and is used to polish the silicon wafer surface. The silicon wafer detection module is used to detect the performance of the polished silicon wafer.

[0018] According to an embodiment of the present invention, a method for non-destructive pyrolysis recovery of waste photovoltaic panels comprises the following steps:

[0019] Pre-processing: remove the aluminum frame, junction box and back panel from the waste photovoltaic panels;

[0020] Pyrolysis: softening the EVA film on the remaining part of the waste photovoltaic panel at the set pyrolysis temperature in a low-temperature pyrolysis furnace;

[0021] Splitting: A cutting machine cuts the softened EVA film to separate the glass sheets from the remaining cells in the waste photovoltaic panels and recycle the glass sheets;

[0022] After removing the aluminum back electrode, the cell is placed in an acid-base treatment module, and the aluminum back electrode on the cell is dissolved in an alkaline solution and precipitated and recovered after acidification to obtain an intermediate product;

[0023] Electrolysis: In the electrochemical recovery module, the silver electrode on the intermediate product is electrolytically recovered to obtain silicon wafers.

[0024] The technical advantages of the method for lossless pyrolysis recovery of waste photovoltaic panels according to an embodiment of the present invention are the same as the technical advantages of the above-mentioned system for lossless pyrolysis recovery of waste photovoltaic panels, and will not be repeated here.

[0025] In some embodiments, during the pyrolysis operation, the low-temperature pyrolysis furnace is provided with a heat source by flue gas from a coal-fired power plant.

[0026] Furthermore, during the pyrolysis operation, the set pyrolysis temperature of the low-temperature pyrolysis furnace is 200-300°C;

[0027] The pyrolysis time of the waste photovoltaic panels in the low-temperature pyrolysis furnace is 0.5 to 2 hours.

[0028] In some embodiments, the recycling method further comprises:

[0029] Pyrolysis gas treatment, wherein the pyrolysis gas generated in the pyrolysis operation and the splitting operation is passed into a gas purification unit, and the gas purification unit sequentially filters the pyrolysis gas for dust removal, adsorbs impurities, and removes fluorides to obtain purified combustible gas;

[0030] Reuse the combustible gas and pass it into the boiler furnace of a coal-fired power plant to assist combustion.

[0031] In some embodiments, between the aluminum back electrode removal operation and the electrolysis operation, the recycling method further includes secondary adhesive removal, placing the battery cell in a solvent stripping module, and using an organic solvent to dissolve the residual EVA adhesive film on the battery cell.

[0032] Furthermore, in the secondary debonding operation, the organic solvent used by the solvent stripping module to dissolve the residual EVA film is tetrahydrofuran or toluene solution;

[0033] The dissolution temperature of the solvent stripping module is 50-70°C;

[0034] The dissolution time of the battery cell in the solvent stripping module is 1 to 2 hours.

[0035] In some embodiments, after the electrolysis operation, the recovery method further comprises:

[0036] Polishing: polishing the surface of the silicon wafer by a polishing machine;

[0037] Testing: Place the polished silicon wafer in the silicon wafer testing module to test the various properties of the silicon wafer.

[0038] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 2 is a schematic structural diagram of a system for pyrolysis and lossless recycling of waste photovoltaic panels according to an embodiment of the present invention.

[0040] Figure 2 The figure is a flow chart of a method for lossless pyrolysis recovery of waste photovoltaic panels according to an embodiment of the present invention.

[0041] Reference numerals:

[0042] 1. Pre-processing unit;

[0043] 2. Mechanical processing unit; 21. Heat source inlet;

[0044] 3. Chemical treatment unit;

[0045] 4. Flue gas mixer; 41. High-temperature flue gas inlet; 42. Low-temperature flue gas inlet; 43. Flue gas outlet;

[0046] 5. Boiler;

[0047] 6. Flue gas treatment system; 61. Economizer; 62. Denitrification unit; 63. Air preheater; 64. Electrostatic precipitator unit;

[0048] 7. Gas purification unit;

[0049] 8. Silicon wafer post-processing unit. DETAILED DESCRIPTION

[0050] The 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.

[0051] like Figure 1 As shown, a waste photovoltaic panel pyrolysis lossless recovery system according to an embodiment of the present invention includes a pretreatment unit 1, a mechanical treatment unit 2 and a chemical treatment unit 3. The pretreatment unit 1 is used to remove the aluminum frame, junction box and backboard on the waste photovoltaic panel; the mechanical treatment unit 2 includes a connected low-temperature pyrolysis furnace and a cutting machine, the low-temperature pyrolysis furnace is connected to the pretreatment unit 1 and is used to soften the EVA film on the waste photovoltaic panel, and the cutting machine is used to cut the softened EVA film to separate the glass sheet from the battery sheet; the chemical treatment unit 3 includes a connected acid-base treatment module and an electrochemical recovery module, the acid-base treatment module is connected to the cutting machine, the acid-base treatment module is used to recover the aluminum back electrode on the battery sheet, and the electrochemical recovery module is used to electrolytically recover the silver electrode on the battery sheet to obtain silicon wafers.

[0052] According to the waste photovoltaic panel pyrolysis lossless recycling system of the embodiment of the present invention, the pre-treatment unit 1 receives the recycled waste photovoltaic panels and first removes the aluminum frame, junction box and back panel on the waste photovoltaic panels, so that the remaining parts of the waste photovoltaic panels can enter the mechanical processing unit 2 for further processing. In the mechanical processing unit 2, the low-temperature pyrolysis furnace can soften the EVA film on the remaining parts of the waste photovoltaic panels, and the cutting machine can separate the complete glass sheets from the battery sheets by cutting the softened EVA film. At this time, the separated complete glass sheets are recycled and reused, and the complete battery sheets are continued to be sent to the chemical treatment unit 3, and the alkali solution in the acid-base treatment module is used as the catalyst. Under the use, the aluminum back electrode on the battery cell is dissolved, and then recovered by precipitation through an acidification process. After this operation, an intermediate product of the battery cell is obtained, and the intermediate product is placed in an electrochemical recovery module for electrolytic recovery of the silver electrode to obtain a complete silicon wafer. That is to say, the present invention combines pyrolysis stratification and chemical treatment technology to remove the back panel and glass while keeping the photovoltaic panel intact, and clean up the aluminum back electrode, silver wire and other attachments on the recycled battery cell to achieve lossless recovery of the silicon wafer. Therefore, compared with related technologies, the present invention can achieve lossless recovery of silicon wafers, and the recovered silicon wafers can be directly reused in photovoltaic panel production, reducing the production cost of photovoltaic panels.

[0053] It should be noted that the "remaining parts of waste photovoltaic panels" are the glass cell sandwich structure, or the structure formed by the glass layer, EVA film layer and cell layer adhered in sequence.

[0054] In addition, in the related technology, the "physical method" is to disassemble the photovoltaic modules mechanically or manually to separate the aluminum frame, junction box, battery cells and other components. This method is environmentally friendly and can be used on a large scale, but the recycling energy consumption is high, and the purity of the material obtained after separation is low; the "chemical solvent method" is to use chemical solvents to remove packaging materials such as EVA. This method can obtain complete silicon wafers and glass, and the recovery rate is high, but the reaction time is long and the process is complicated, which is not conducive to large-scale production. In comparison, the "thermal decomposition method" is to decompose organic matter such as EVA by heating to separate glass and battery cells. This method has high recovery efficiency, high material purity, is convenient and fast, and is suitable for industrial production. Therefore, the present invention is based on the "thermal decomposition method" and combined with chemical treatment technology for design. It can perform low-temperature pyrolysis without crushing the waste photovoltaic panels, and then achieve complete recovery of silicon wafers through corresponding chemical treatment, which is conducive to the direct use of recycled silicon wafers to re-produce photovoltaic panels in the later stage.

[0055] like Figure 1 As shown, in some embodiments, the pretreatment unit 1 includes a disassembly machine and a mechanical stripping machine connected to each other. The disassembly machine is used to remove the aluminum frame and junction box on the waste photovoltaic panels. The mechanical stripping machine is connected to the low-temperature pyrolysis furnace and is used to strip the back panel on the waste photovoltaic panels.

[0056] It can be understood that through the cooperation of the dismantling machine and the mechanical stripping machine, the aluminum frame, junction box and backboard on the waste photovoltaic panels can be removed, and the backboard is removed by the mechanical stripping machine before pyrolysis. At the same time, low-temperature pyrolysis is used to decompose the remaining parts of the waste photovoltaic panels, which reduces the generation of HF pollutants during the pyrolysis process. Compared with the high-temperature pyrolysis method used in related technologies, the generation ratio of HF pollutants is reduced by more than 80%.

[0057] like Figure 1 As shown, in some embodiments, the low-temperature pyrolysis furnace is provided with a heat source inlet 21, which is adapted to be connected to a flue of a coal-fired power plant so that the flue gas of the coal-fired power plant provides a heat source for the low-temperature pyrolysis furnace.

[0058] It is understandable that the flue gas from coal-fired power plants provides heat for the pyrolysis of photovoltaic panels in the low-temperature pyrolysis furnace, which saves the energy consumption of pyrolysis of photovoltaic panels and reduces the cost of recycling waste photovoltaic panels.

[0059] Specifically, the inner cavity of the low-temperature pyrolysis furnace can be coated with heating tubes, which are connected to the end of the flue of the coal-fired power plant away from the heat source inlet 21, so as to heat the inner cavity of the low-temperature pyrolysis furnace with the help of the heat exchange effect of the flue gas introduced into the heating tubes, thereby realizing the pyrolysis of the photovoltaic panels in the low-temperature pyrolysis furnace. That is to say, the photovoltaic panels in the low-temperature pyrolysis furnace can exchange heat with the heat source (i.e., flue gas) without contact.

[0060] like Figure 1 As shown, in some embodiments, the recovery system also includes a flue gas mixer 4, which is provided with a high-temperature flue gas inlet 41, a low-temperature flue gas inlet 42 and a flue gas outlet 43. The high-temperature flue gas inlet 41 is connected to the flue between the economizer 61 and the denitrification unit 62 of the coal-fired power plant, the low-temperature flue gas inlet 42 is connected to the flue between the air preheater 63 and the electrostatic precipitator system of the coal-fired power plant, and the flue gas outlet 43 is connected to the heat source inlet 21.

[0061] It can be understood that since the flue gas temperature in the flue between the economizer 61 and the denitrification unit 62 of the coal-fired power plant is closer to the flue gas temperature generated by the furnace of the boiler 5 of the coal-fired power plant than the flue gas temperature in the flue between the air preheater 63 and the electrostatic precipitator system of the coal-fired power plant, the temperature of the flue gas in the flue at the outlet of the economizer 61 is higher than the temperature of the flue gas in the flue at the outlet of the air preheater 63. The use of the flue gas mixer 4 can achieve the mixing of the flue gases taken from the aforementioned two flues in the required proportion, which is conducive to flexibly adjusting the flue gas temperature according to the actual pyrolysis temperature requirements of the photovoltaic panels to meet the pyrolysis requirements, thereby further improving the applicability of the system.

[0062] Specifically, the coal-fired power plant includes a boiler 5 and a flue gas treatment system 6. The flue gas treatment system 6 generally includes an economizer 61, a denitrification unit 62, an air preheater 63 and an electrostatic precipitator unit 64 connected in sequence, and the exhaust gas outlet of the furnace of the boiler 5 is connected to the economizer 61, which can realize the treatment of the flue gas of the coal-fired power plant.

[0063] Furthermore, the cutting machine is a hot knife cutting machine.

[0064] It is understandable that the use of a hot knife cutting machine can ensure that the temperature of the cutting tool is not lower than the temperature of the softened EVA film, so as to effectively avoid heat exchange between the cutting tool and the softened EVA film, which may easily affect the softening of the EVA film and cause the glass sheet and battery sheet to be unable to be separated smoothly.

[0065] like Figure 1 As shown, in some embodiments, the mechanical processing unit 2 is provided with a pyrolysis gas outlet, which is used to discharge the pyrolysis gas in the low-temperature pyrolysis furnace and the cutting machine.

[0066] The recovery system further includes a gas purification unit 7 , which is connected to the pyrolysis gas outlet to purify the pyrolysis gas.

[0067] It is understandable that the gas purification unit 7 can purify the pyrolysis gas generated by the pyrolysis of the photovoltaic panels to reduce environmental pollution and improve the environmental friendliness of the system.

[0068] like Figure 1 As shown, in some embodiments, the gas purification unit 7 includes a cyclone dust collector, an activated carbon adsorption tower and a defluorination module connected in sequence, the cyclone dust collector is connected to the pyrolysis gas outlet and is used to filter dust in the pyrolysis gas, the activated carbon adsorption tower is used to adsorb adsorbable impurities in the pyrolysis gas, and the defluorination module is used to remove fluorides in the pyrolysis gas to obtain purified combustible gas.

[0069] The defluorination module is suitable for being connected to the furnace of the boiler 5 of the coal-fired power plant so as to introduce combustible gas to assist combustion.

[0070] It can be understood that the pyrolysis gas (or tail gas) generated by the pyrolysis of the photovoltaic panels is purified by the gas purification unit 7 in cooperation with the flue gas treatment system 6 of the coal-fired power plant, and the SCR and wet desulfurization systems of the coal-fired power plant can be directly utilized, avoiding the construction of new tail gas purification facilities and reducing investment costs. At the same time, since the combustible gas generated by the pyrolysis of the photovoltaic panels is introduced into the furnace of the boiler 5 for combustion assistance, the calorific value of the pyrolysis of the photovoltaic panels can also be fully utilized.

[0071] like Figure 1 As shown, in some embodiments, the chemical treatment unit 3 also includes a solvent stripping module, which is connected between the acid-base treatment module and the electrochemical recovery module. The solvent stripping module is provided with an organic solvent for dissolving the residual EVA film on the battery cell to further remove the residual EVA film on the battery cell and ensure the quality of battery cell recovery.

[0072] like Figure 1As shown, in some embodiments, the recycling system also includes a silicon wafer post-processing unit 8, which includes a connected polishing machine and a silicon wafer detection module. The polishing machine is connected to the electrochemical recovery module and is used to polish the surface of the silicon wafer. The silicon wafer detection module is used to detect the performance of the polished silicon wafer, such as determining the conversion efficiency of the silicon wafer.

[0073] It is understandable that the silicon wafer post-processing unit 8 can be used to process the recycled silicon wafers so that the recycled silicon wafers with qualified performance can be directly used in photovoltaic panel production, thereby reducing the defective rate of photovoltaic panels and saving production costs.

[0074] like Figure 2 As shown, a method for non-destructive pyrolysis recovery of waste photovoltaic panels according to an embodiment of the present invention comprises the following steps:

[0075] Step S1, pre-processing, removing the aluminum frame, junction box and back plate from the waste photovoltaic panels;

[0076] Step S2, pyrolysis, softening the EVA film on the remaining portion of the waste photovoltaic panel at a set pyrolysis temperature in a low-temperature pyrolysis furnace;

[0077] Step S3: splitting, using a cutting machine to cut the softened EVA film to separate the glass sheets from the remaining parts of the waste photovoltaic panels and the battery sheets, and then recovering the glass sheets;

[0078] Step S4, removing the aluminum back electrode, placing the cell in an acid-base treatment module, dissolving the aluminum back electrode on the cell in an alkaline solution and acidifying and then precipitating and recovering to obtain an intermediate product;

[0079] Step S5: electrolysis, in which the silver electrode on the intermediate product is electrolytically recovered in an electrochemical recovery module to obtain a silicon wafer.

[0080] The technical advantages of the method for lossless pyrolysis recovery of waste photovoltaic panels according to an embodiment of the present invention are the same as the technical advantages of the above-mentioned system for lossless pyrolysis recovery of waste photovoltaic panels, and will not be repeated here.

[0081] Furthermore, in step S2, the low-temperature pyrolysis furnace is provided with a heat source by the flue gas of a coal-fired power plant.

[0082] Furthermore, in step S2, the set pyrolysis temperature of the low-temperature pyrolysis furnace is 200-300°C;

[0083] The pyrolysis time of waste photovoltaic panels in a low-temperature pyrolysis furnace is 0.5 to 2 hours.

[0084] like Figure 2 As shown, in some embodiments, the recycling method further comprises:

[0085] Step S2', pyrolysis gas treatment, the pyrolysis gas generated in the pyrolysis operation and the splitting operation is passed into the gas purification unit 7, and the gas purification unit 7 sequentially filters the pyrolysis gas for dust removal, adsorbs impurities, and removes fluorides to obtain purified combustible gas;

[0086] Step S2″, reuse, and pass the combustible gas into the furnace of the boiler 5 of the coal-fired power plant to assist combustion.

[0087] like Figure 2 As shown, in some embodiments, between step S4 and step S5, the recycling method further includes step S4', secondary debonding, placing the battery cell in a solvent stripping module, and using an organic solvent to dissolve the residual EVA film on the battery cell.

[0088] Furthermore, in step S4', the organic solvent used by the solvent stripping module to dissolve the residual EVA film is tetrahydrofuran or toluene solution;

[0089] The dissolution temperature of the solvent stripping module is 50-70°C;

[0090] The dissolution time of the battery cell in the solvent stripping module is 1 to 2 hours.

[0091] like Figure 2 As shown, in some embodiments, after step S5, the recycling method further includes:

[0092] Step S6, polishing, polishing the surface of the silicon wafer by a polishing machine;

[0093] Step S7: testing: placing the polished silicon wafer in a silicon wafer testing module to test various properties of the silicon wafer.

[0094] Therefore, in some embodiments of the present invention, the method for lossless pyrolysis recovery of waste photovoltaic panels includes step S1, step S2, step S3, step S4 and step S5; in other embodiments, the method for lossless pyrolysis recovery of waste photovoltaic panels includes step S1, step S2, step S2', step S2", step S3, step S4 and step S5. It should be noted that in this embodiment, step S2' and step S2" and step S3 are two processes after step S2, that is, the two processes are performed in parallel; in still other embodiments, the method for lossless pyrolysis recovery of waste photovoltaic panels includes step S1, step S2, step S3, step S4 and step S5. Step S2', step S2", step S3, step S4, S4' and step S5. Similarly, in this embodiment, step S2' and step S2" and step S3 are two processes after step S2, that is, the two processes are carried out in parallel; in some further embodiments, the method for lossless pyrolysis recovery of waste photovoltaic panels includes step S1, step S2, step S2', step S2", step S3, step S4, S4', step S5, step S6 and step S7. Similarly, in this embodiment, step S2' and step S2" and step S3 are two processes after step S2, that is, the two processes are carried out in parallel. That is to say, the method for lossless pyrolysis recovery of waste photovoltaic panels of the present invention can be the aforementioned four methods respectively.

[0095] The present invention is further described below through specific examples.

[0096] Example 1

[0097] A method for non-destructive recycling of waste photovoltaic panels by pyrolysis, based on the above system, comprises the following steps:

[0098] 1) The recovered complete waste photovoltaic panels are sent to the pre-processing unit 1, after the aluminum frame and junction box are removed, the back sheet layer is removed by a mechanical stripping machine;

[0099] 2) The complete single-piece glass and cell interlayer are sent to a low-temperature pyrolysis furnace. At the same time, high-temperature flue gas of about 450°C from the flue of the outlet section of the economizer 61 of the coal-fired power plant and low-temperature flue gas of about 150°C from the flue of the outlet section of the air preheater 63 are mixed in a flue gas mixer 4 at a ratio of 1:1 and then sent to the low-temperature pyrolysis furnace. The temperature in the furnace is maintained at 250°C. The glass cell interlayer reacts in the low-temperature pyrolysis furnace for 1 hour, and the EVA film softens. The film layer is cut with a hot knife to separate the glass layer for recycling. During this process, the EVA and backsheet residues will also decompose at low temperature, generating a small amount of pyrolysis gas and fluorine-containing harmful gases. The aforementioned gases (excluding the flue gas) are sent to the gas purification unit 7 for purification;

[0100] 3) The cell is sent to the chemical treatment unit 3. The cell first enters the acid-base treatment module, where the aluminum back electrode is dissolved under the action of alkaline solution. It is then precipitated and recovered through an acidification process. Then, in the solvent stripping module, the cell reacts in tetrahydrofuran at 60°C for 1.5 hours to dissolve the residual EVA film. Finally, in the electrochemical recovery module, the silver electrode is recovered by electrolysis to obtain a complete silicon wafer;

[0101] 4) The silicon wafers in step 3) above are further sent to the silicon wafer post-processing unit 8, where they are polished to restore the surface smoothness of the silicon wafers and then recycled after the efficiency of the silicon wafers is determined by the silicon wafer detection module.

[0102] In addition, in the above step 2), the pyrolysis gas entering the gas purification unit 7 is first removed from the dust and adsorbable impurities in the pyrolysis gas under the action of the cyclone dust collector and the activated carbon adsorption tower, and then the fluoride is removed by the defluorination module, and finally the purified combustible gas is transported to the furnace of the boiler 5 for combustion.

[0103] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0104] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0105] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0106] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0107] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" 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 expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0108] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A waste photovoltaic panel pyrolysis lossless recovery system, characterized in that: include: A pre-processing unit, which is used to remove the aluminum frame, junction box and back plate from the waste photovoltaic panels; A mechanical processing unit, comprising a low-temperature pyrolysis furnace and a cutting machine connected thereto. The low-temperature pyrolysis furnace is connected to the pretreatment unit and is used to soften the EVA film on the waste photovoltaic panels. The cutting machine is used to cut the softened EVA film to separate the glass sheets from the battery sheets. A chemical treatment unit, comprising an acid-base treatment module and an electrochemical recovery module connected to each other, wherein the acid-base treatment module is connected to the cutting machine, the acid-base treatment module is used to recover the aluminum back electrode on the battery cell, and the electrochemical recovery module is used to electrolytically recover the silver electrode on the battery cell to obtain silicon wafers.

2. The waste photovoltaic panel pyrolysis lossless recovery system according to claim 1 is characterized in that: The low-temperature pyrolysis furnace is provided with a heat source inlet, which is suitable for communicating with the flue of a coal-fired power plant so that the flue gas of the coal-fired power plant can provide a heat source for the low-temperature pyrolysis furnace.

3. The waste photovoltaic panel pyrolysis lossless recovery system according to claim 2, characterized in that: It also includes a flue gas mixer, which is provided with a high-temperature flue gas inlet, a low-temperature flue gas inlet and a flue gas outlet. The high-temperature flue gas inlet is connected to the flue between the economizer and the denitrification system of the coal-fired power plant, the low-temperature flue gas inlet is connected to the flue between the air preheater and the electrostatic precipitator system of the coal-fired power plant, and the flue gas outlet is connected to the heat source inlet.

4. The waste photovoltaic panel pyrolysis lossless recovery system according to claim 1, characterized in that: The mechanical processing unit is provided with a pyrolysis gas outlet, and the pyrolysis gas outlet is used to discharge the pyrolysis gas in the low-temperature pyrolysis furnace and the cutting machine; The recovery system further includes a gas purification unit, which is in communication with the pyrolysis gas outlet to purify the pyrolysis gas.

5. The waste photovoltaic panel pyrolysis lossless recovery system according to claim 4 is characterized in that: The gas purification unit includes a cyclone dust collector, an activated carbon adsorption tower and a defluorination module connected in sequence, the cyclone dust collector is connected to the pyrolysis gas outlet and is used to filter dust in the pyrolysis gas, the activated carbon adsorption tower is used to adsorb adsorbable impurities in the pyrolysis gas, and the defluorination module is used to remove fluorides in the pyrolysis gas to obtain purified combustible gas; The defluorination module is suitable for being connected to the boiler furnace of a coal-fired power plant so as to introduce the combustible gas for combustion assistance.

6. The waste photovoltaic panel pyrolysis lossless recovery system according to claim 1, characterized in that: The chemical treatment unit further includes a solvent stripping module, which is connected between the acid-base treatment module and the electrochemical recovery module. The solvent stripping module is provided with an organic solvent for dissolving residual EVA film on the battery cell.

7. The waste photovoltaic panel pyrolysis lossless recovery system according to claim 1, characterized in that: It also includes a silicon wafer post-processing unit, which includes a polishing machine and a silicon wafer detection module connected to each other. The polishing machine is connected to the electrochemical recovery module and is used to polish the surface of the silicon wafer. The silicon wafer detection module is used to detect the performance of the polished silicon wafer.

8. A method for non-destructive recycling of waste photovoltaic panels by pyrolysis, characterized in that: The recovery method comprises the following steps: Pre-processing: remove the aluminum frame, junction box and back panel from the waste photovoltaic panels; Pyrolysis: softening the EVA film on the remaining part of the waste photovoltaic panel at the set pyrolysis temperature in a low-temperature pyrolysis furnace; Splitting: A cutting machine cuts the softened EVA film to separate the glass sheets from the remaining cells in the waste photovoltaic panels and recycle the glass sheets; After removing the aluminum back electrode, the cell is placed in an acid-base treatment module, and the aluminum back electrode on the cell is dissolved in an alkaline solution and precipitated and recovered after acidification to obtain an intermediate product; Electrolysis: In the electrochemical recovery module, the silver electrode on the intermediate product is electrolytically recovered to obtain silicon wafers.

9. The method for non-destructive recycling of waste photovoltaic panels by pyrolysis according to claim 8, characterized in that: During the pyrolysis operation, the low-temperature pyrolysis furnace is provided with heat source by flue gas from a coal-fired power plant.

10. The method for non-destructive recycling of waste photovoltaic panels by pyrolysis according to claim 8 or 9, characterized in that: After the electrolysis operation, the recovery method further comprises: Polishing: polishing the surface of the silicon wafer by a polishing machine; Testing: Place the polished silicon wafer in the silicon wafer testing module to test the various properties of the silicon wafer.

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