Method and system for recycling waste photovoltaic backboards

Abstract

The invention relates to the technical field of waste photovoltaic back plate recovery, in particular to a waste photovoltaic back plate recovery method and system. The method comprises the following steps: (1) contacting the waste photovoltaic backboard with a solvent I, and carrying out first dissolution to obtain a liquid-phase component I and a solid-phase component I; (2) finely filtering the liquid-phase component I to obtain a liquid-phase component I'and filter residues; (3) contacting the liquid-phase component I'with a solvent II, and carrying out first reverse analysis to obtain a liquid-phase component II and a solid-phase component II; (4) contacting the solid-phase component I with a solvent III for secondary dissolution to obtain a liquid-phase component III and a solid-phase component III; and (5) contacting the liquid-phase component III with a solvent IV, and carrying out second reverse analysis to obtain a liquid-phase component IV and a solid-phase component IV. According to the recycling method of the waste photovoltaic backboard, the separation efficiency and the recycling rate of PVDF and PET can be remarkably improved, titanium dioxide can be recycled, and waste of titanium dioxide is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of waste photovoltaic back panel recycling, and in particular to a waste photovoltaic back panel recycling method and system. Background Art

[0002] Photovoltaic backsheet is a photovoltaic packaging material located on the back of the solar cell module. It is mainly used to protect the solar cell module in the outdoor environment. It can resist the erosion of environmental factors such as light, humidity and heat on packaging films, solar cells and other materials, and play a role in weather-resistant insulation protection. The extensive use, iteration and update of solar cells have produced a large number of waste photovoltaic backsheets, which will have adverse effects on the environment. The main components of waste photovoltaic backsheets include PVDF (polyvinyl chloride), PET (polyethylene terephthalate), titanium dioxide and polymer film. Recovering the above components from the above-mentioned waste photovoltaic backsheets is of great significance to the efficient recycling of photovoltaic backsheets.

[0003] At present, some technical routes have been developed for the recycling of waste photovoltaic backplanes. CN115945497A discloses a method for stripping the backplane of a photovoltaic module. CN103752190A discloses a method for recycling and reusing waste polyvinylidene fluoride flat membranes. At 40°C, the PVDF flat membrane is soaked in NMP for 10 hours to achieve the dissolution and recovery of PVDF.

[0004] Although these methods can separate and recycle PVDF and PET from waste photovoltaic backplanes, the above separation and recycling methods and systems generally have the problems of low separation efficiency and long dissolution time, and titanium dioxide is not recycled, resulting in a waste of resources. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems existing in the prior art of long process flow, low separation efficiency, long dissolution time, high energy consumption, and inability to effectively separate titanium dioxide in the recycling process of waste photovoltaic back panels, and to provide a method and system for recycling waste photovoltaic back panels.

[0006] In order to achieve the above object, a first aspect of the present invention provides a method for recycling waste photovoltaic backsheets, wherein the method comprises the following steps:

[0007] (1) contacting a waste photovoltaic backsheet with a solvent I to perform a first dissolution to obtain a liquid phase component I and a solid phase component I; wherein the waste photovoltaic backsheet comprises PVDF, PET, TiO2 and a polymer film; the solvent I is selected from at least two of dimethyl sulfoxide, N-methylpyrrolidone and N-formylmorpholine; wherein the liquid phase component I comprises PVDF, solvent I and TiO2;

[0008] (2) finely filtering the liquid component I to obtain a liquid component I' and a filter residue, wherein the filter residue is TiO2;

[0009] (3) contacting the liquid phase component I' with a solvent II, performing a first reverse analysis, and obtaining a liquid phase component II and a solid phase component II; wherein the solvent II is selected from one or more of water, ethanol, and toluene; and the solid phase component II is PVDF;

[0010] (4) contacting the solid phase component I with a solvent III for a second dissolution to obtain a liquid phase component III and a solid phase component III; wherein the solvent III is selected from one or more of trifluoroacetic acid, hexafluoroisopropanol, o-chlorophenol, and chloroform, and the solid phase component III is a polymer film;

[0011] (5) contacting the liquid phase component III with a solvent IV and performing a second reverse analysis to obtain a liquid phase component IV and a solid phase component IV; wherein the solvent IV is selected from one or more of water, ethanol, and toluene, and the solid phase component IV is PET.

[0012] The second aspect of the present invention provides a recycling system for waste photovoltaic backplanes, wherein the recycling system includes a PVDF dissolution device 1, a fine filtration device 2, a PVDF decomposition device 3, a PET dissolution device 4 and a PET decomposition device 5; wherein the PVDF dissolution device 1 is connected to the fine filtration device 2 and the PET dissolution device 5 respectively, the fine filtration device 2 is connected to the PVDF decomposition device 3, and the PET dissolution device 4 is connected to the PET decomposition device 5.

[0013] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0014] 1) The method for recycling waste photovoltaic backsheets provided in the present invention uses solvent I to selectively dissolve PVDF, uses solvent II to reversely analyze PVDF, uses solvent III to dissolve PET, and uses solvent IV to reversely analyze PET, which can significantly improve the separation efficiency and recovery rate of PVDF and PET;

[0015] 2) In the method for recycling waste photovoltaic backsheets provided in the present invention, solvent I, solvent II, solvent III and solvent IV are all green solvents with good environmental performance;

[0016] 3) The method for recycling waste photovoltaic backsheets provided in the present invention realizes effective recovery of solvent I and solvent II wrapped in PVDF by freeze drying, so that the purity of PVDF is ≥95%; and realizes effective recovery of solvent III and solvent IV wrapped in PET by vacuum drying, so that the purity of PET is ≥95%;

[0017] 4) The method for recycling waste photovoltaic backsheets provided in the present invention can achieve efficient recovery of titanium dioxide and avoid waste of titanium dioxide;

[0018] 5) The method for recycling waste photovoltaic backsheets provided in the present invention solves the problems existing in the prior art such as long separation process, high energy consumption, low separation efficiency, incomplete product recovery, etc., and fills the technical gap of efficiently recycling waste photovoltaic backsheets using organic solvents. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic structural diagram of a waste photovoltaic back panel recycling system provided in the present invention.

[0020] Description of Reference Numerals

[0021] 1. PVDF dissolution device 2. Fine filtration device 3. PVDF reverse analysis device

[0022] 4. PET dissolution device 5. PET reverse analysis device 6. First solid-liquid separation device

[0023] 7, second solid-liquid separation device 8, third solid-liquid separation device 9, fourth solid-liquid separation device

[0024] 10. Roasting device 11. Freeze drying device 12. Vacuum drying device

[0025] 13. Distillation tower I 14. Distillation tower II DETAILED DESCRIPTION

[0026] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0027] A first aspect of the present invention provides a method for recycling waste photovoltaic backsheets, wherein the method comprises the following steps:

[0028] (1) contacting a waste photovoltaic backsheet with a solvent I to perform a first dissolution to obtain a liquid phase component I and a solid phase component I; wherein the waste photovoltaic backsheet comprises PVDF, PET, TiO2 and a polymer film; the solvent I is selected from at least two of dimethyl sulfoxide, N-methylpyrrolidone and N-formylmorpholine; and the liquid phase component I comprises PVDF, the solvent I and TiO2;

[0029] (2) finely filtering the liquid component I to obtain a liquid component I' and a filter residue, wherein the filter residue is TiO2;

[0030] (3) contacting the liquid phase component I' with a solvent II, performing a first reverse analysis, and obtaining a liquid phase component II and a solid phase component II; wherein the solvent II is selected from one or more of water, ethanol, and toluene; and the solid phase component II is PVDF;

[0031] (4) contacting the solid phase component I with a solvent III for a second dissolution to obtain a liquid phase component III and a solid phase component III; wherein the solvent III is selected from one or more of trifluoroacetic acid, hexafluoroisopropanol, o-chlorophenol, and chloroform, and the solid phase component III is a polymer film;

[0032] (5) contacting the liquid phase component III with a solvent IV and performing a second reverse analysis to obtain a liquid phase component IV and a solid phase component IV; wherein the solvent IV is selected from one or more of water, ethanol, and toluene, and the solid phase component IV is PET.

[0033] Among them, in the present invention, the inventors have found through research that PVDF can be separated from waste photovoltaic backboards by utilizing the selective solubility of solvent I, and PVDF dissolved in solvent I can be slowly precipitated by utilizing solvent II; PET can be separated from waste photovoltaic backboards by utilizing the selective solubility of solvent III, and PET dissolved in solvent III can be slowly precipitated by utilizing solvent IV; TiO2 and polymer films can be separated from waste photovoltaic backboards by filtration by utilizing the insolubility of TiO2 and polymer films and the particle size difference between the two.

[0034] In step (1):

[0035] In one embodiment of the present invention, based on the total mass of the waste photovoltaic backboard, the content of PET in the waste photovoltaic backboard is 60-85wt%, the content of PVDF is 5-15wt%, the content of TiO2 is 2-10wt%, and the content of polymer film is 10-30wt%.

[0036] Among them, in the present invention, the main components of the waste photovoltaic back sheet are PVDF, PET and nano-level TiO2. In addition, it also contains some polymer films that play a bonding role.

[0037] In one embodiment of the present invention, the particle size of the waste photovoltaic backsheet is 0.5-3 cm, preferably 0.8-2.5 cm.

[0038] In the present invention, the polymer film can be broken into small flakes as the waste photovoltaic backsheet is broken. Breaking the waste photovoltaic backsheet can accelerate the dissolution rate on the one hand, and control the particle size of the polymer film on the other hand, so as to achieve the separation of TiO2 and the polymer film through the particle size difference.

[0039] In one embodiment of the present invention, the solvent I is dimethyl sulfoxide and N-methyl pyrrolidone, wherein the mass ratio of dimethyl sulfoxide to N-methyl pyrrolidone is 1:0.01-1.5, preferably 1:0.6-1.2.

[0040] Among them, in the present invention, solvent I can selectively dissolve PVDF, but does not dissolve PET. The waste photovoltaic backsheet is contacted with solvent I, PVDF can be separated from the waste photovoltaic backsheet to obtain a liquid phase component I containing PVDF. The inventors of the present invention have found through research that compared with using dimethyl sulfoxide, N-methylpyrrolidone, and N-formylmorpholine alone, using a mixed solution of at least two of dimethyl sulfoxide, N-methylpyrrolidone, and N-formylmorpholine to dissolve the waste photovoltaic backsheet can greatly increase the dissolution rate and shorten the dissolution time.

[0041] In one embodiment of the present invention, the mass ratio of the waste photovoltaic backsheet to the solvent I is 1:5-20, preferably 1:1:7-12.

[0042] In one embodiment of the present invention, the operating conditions of the first dissolution include: the first dissolution temperature is 70-120°C, preferably 85-95°C; the first dissolution pressure is 0.05-0.5MPa, preferably 0.1-0.3MPa; the first dissolution time is 10-100min, preferably 30-60min.

[0043] In one embodiment of the present invention, after the first dissolution is completed, a first solid-liquid separation is performed to obtain a liquid component I and a solid component I; wherein the liquid component I includes PVDF, solvent I and TiO2.

[0044] Among them, in the present invention, the TiO2 in the waste photovoltaic backplane is nanoparticles, and the polymer film is tiny flakes. During the first solid-liquid separation, PVDF is dissolved in solvent I, most of the solvent I and nano-scale TiO2 enter the liquid phase to form a liquid phase component I, and PET and the polymer film carry part of the solvent I into the solid phase to form a solid phase component I.

[0045] In step (2):

[0046] In one embodiment of the present invention, the fine filtration is performed in a filter with a pore size of ≤100 nm, preferably ≤50 nm.

[0047] Among them, in the present invention, nano-scale TiO2 can be basically completely separated from the liquid phase component I through fine filtration, thereby realizing the recovery of TiO2.

[0048] In one embodiment of the present invention, the step (2) further comprises: calcining the filter residue to obtain recovered TiO2.

[0049] In the present invention, some solvent I still remains on the surface of the filter residue obtained by fine filtration, and the filter residue is calcined to remove the solvent I and obtain high-purity recovered TiO2. The calcination temperature can be 500-1000°C and the calcination time can be 2-6h.

[0050] In step (3):

[0051] In one embodiment of the present invention, the solvent II is water, preferably deionized water. In the present invention, the solvent II is added to the liquid component I', and under the action of the solvent II, PVDF can be precipitated from the liquid component I', thereby separating PVDF.

[0052] In one embodiment of the present invention, the mass ratio of the liquid component I' to the solvent II is 1:1-5, preferably 1:2-3.

[0053] In one embodiment of the present invention, the operating conditions of the first inversion include: the first inversion temperature is 50-90°C, preferably 60-80°C; the first inversion pressure is 0.05-0.5MPa, preferably 0.1-0.3MPa; the first inversion time is 20-80min, preferably 40-60min.

[0054] In one embodiment of the present invention, after the first reverse analysis is completed, a second solid-liquid separation is performed to obtain a liquid phase component II and a wet solid phase component II'; wherein the liquid phase component II includes solvent I and solvent II.

[0055] In one embodiment of the present invention, the wet solid phase component II' is freeze-dried to obtain a solid phase component II and a freeze-dried liquid.

[0056] Among them, in the present invention, the solvent I and the solvent II wrapped on the PVDF particles can be separated by freeze drying to obtain PVDF particles with a purity of ≥95%.

[0057] In one embodiment of the present invention, the freeze-drying operating conditions include: freeze-drying temperature of -115°C to -90°C, preferably -105°C to -100°C; freeze-drying pressure of 0.2-0.8MPa, preferably 0.4-0.6MPa; freeze-drying time of 12-14h, preferably 24-36h.

[0058] In one embodiment of the present invention, the liquid phase component II and / or the freeze-dried liquid are distilled to recover the solvent I and the solvent II. In the present invention, the recovered solvent I can be returned to step (1), and the recovered solvent II can be returned to step (2) for repeated use.

[0059] In step (4):

[0060] In one embodiment of the present invention, the solvent III is trifluoroacetic acid and / or hexafluoroisopropanol, preferably trifluoroacetic acid and hexafluoroisopropanol; wherein the weight ratio of trifluoroacetic acid to hexafluoroisopropanol is 1:0.1-2, preferably 1:0.5-1.5.

[0061] Among them, in the present invention, the solvent III can dissolve the PET in the solid phase component I, so that the PET can be separated from the solid phase component I to obtain the liquid phase component III containing PET and the solvent III, and the solid phase component III containing the polymer film. Compared with a single solvent, when the solvent III is a mixed solvent, the solvent III has a better dissolving effect on PET, which can further improve the recovery rate of PET.

[0062] In one embodiment of the present invention, the mass ratio of the solid phase component I to the solvent III is 1:5-25, preferably 1:10-15.

[0063] In one embodiment of the present invention, the operating conditions of the second dissolution include: the second dissolution temperature is 25-120°C, preferably 30-55°C; the second dissolution pressure is 0.05-0.5MPa, preferably 0.1-0.3MPa; the second dissolution time is 10-100min, preferably 30-60min.

[0064] In one embodiment of the present invention, after the second dissolution is completed, a third solid-liquid separation is performed to obtain a liquid phase component III and a solid phase component III.

[0065] Among them, in the present invention, after the third solid-liquid separation, the separated solid phase component III contains a small amount of liquid, and the solid phase component III can be dried according to actual needs.

[0066] In step (5):

[0067] In one embodiment of the present invention, the solvent IV is water, preferably deionized water. In the present invention, the solvent IV is added to the liquid phase component III, and under the action of the solvent IV, PET can be precipitated from the liquid phase component III, thereby separating PET particles.

[0068] In one embodiment of the present invention, the mass ratio of the liquid component III to the solvent IV is 1:1-5, preferably 1:2-3.

[0069] In one embodiment of the present invention, the operating conditions of the second reverse analysis include: the second reverse analysis temperature is 25-90°C, preferably 30-55°C; the second reverse analysis pressure is 0.05-0.5MPa, preferably 0.1-0.3MPa; the second reverse analysis time is 20-80min, preferably 40-60min.

[0070] In one embodiment of the present invention, after the second reverse analysis is completed, a fourth solid-liquid separation is performed to obtain a liquid phase component IV and a wet solid phase component IV'. The liquid phase component IV includes solvent III and solvent IV.

[0071] In one embodiment of the present invention, the wet solid phase component IV' is vacuum dried to obtain a solid phase component IV and a vacuum dried liquid.

[0072] Among them, in the present invention, the solvent III and the solvent IV wrapped on the wet PET particles can be separated through vacuum drying to obtain PET particles with a purity of ≥95%.

[0073] In one embodiment of the present invention, the liquid phase component IV and / or the vacuum dried liquid are distilled to recover solvent III and solvent IV. In the present invention, the recovered solvent III can be returned to step (3), and the recovered solvent IV can be returned to step (4) for reuse.

[0074] The second aspect of the present invention provides a recycling system for waste photovoltaic backplanes, wherein the recycling system includes a PVDF dissolution device 1, a fine filtration device 2, a PVDF decomposition device 3, a PET dissolution device 4 and a PET decomposition device 5; wherein the PVDF dissolution device 1 is connected to the fine filtration device 2 and the PET dissolution device 4 respectively, the fine filtration device 2 is connected to the PVDF decomposition device 3, and the PET dissolution device 4 is connected to the PET decomposition device 5.

[0075] In a preferred embodiment of the present invention, the recovery system also includes a first solid-liquid separation device 6, a second solid-liquid separation device 7, a third solid-liquid separation device 8 and a fourth solid-liquid separation device 9; wherein the first solid-liquid separation device 6 is connected to the PVDF dissolution device 1, the fine filtration device 2 and the PET dissolution device 4, respectively, the second solid-liquid separation device 7 is connected to the PVDF reverse analysis device 3, the third solid-liquid separation device 8 is connected to the PET dissolution device 4 and the PET reverse analysis device 5; the fourth solid-liquid separation device 9 is connected to the PET reverse analysis device 5.

[0076] In a preferred embodiment of the present invention, the recovery system further comprises a roasting device 10 , wherein the roasting device 10 is connected to the fine filtering device 3 .

[0077] In a preferred embodiment of the present invention, the recovery system also includes a freeze-drying device 11, a vacuum drying device 12, a distillation tower I13 and a distillation tower II14; wherein the freeze-drying device 11 is respectively connected to the second solid-liquid separation device 7 and the distillation tower I13, and the distillation tower I13 is also respectively connected to the PVDF dissolution device 1 and the PVDF decomposition device 3; the vacuum drying device 12 is connected to the fourth solid-liquid separation device 9 and the distillation tower II14, and the distillation tower II14 is also respectively connected to the PET dissolution device 4 and the PET decomposition device 5.

[0078] Among them, in the present invention, the waste photovoltaic backsheet and solvent I are contacted in a PVDF dissolution device to perform a first dissolution, and the solvent I selectively dissolves the PVDF in the waste photovoltaic backsheet, and then is transported to a first solid-liquid separation device for a first solid-liquid separation to obtain a liquid phase component I containing PVDF, solvent I and TiO2, and a solid phase component I containing PET, a small amount of solvent I and an insoluble polymer film.

[0079] The obtained liquid phase component I is transported to a fine filtering device for fine filtering to obtain a filter residue containing TiO2 and a liquid phase component I' containing PVDF and solvent I. The obtained filter residue is transported to a roasting device for roasting to obtain recovered TiO2.

[0080] The obtained liquid phase component I' is transported to a PVDF reverse analysis device, and the liquid phase component I' and the solvent II are contacted in a PVDF reverse analysis device to perform a first reverse analysis, and PVDF is precipitated from the liquid phase component I under the action of the solvent II, and then transported to a second solid-liquid separation device for a second solid-liquid separation to obtain a liquid phase component II and a wet solid phase component II'; the obtained wet solid phase component II' is transported to a freeze drying device for freeze drying to obtain a solid phase component II and a freeze-dried liquid;

[0081] The obtained liquid component II and freeze-dried liquid are transported to the distillation tower I for distillation to recover the solvent I and the solvent II; the recovered solvent I is condensed by the condensation device I and then returned to the PVDF dissolution device for recycling, and the recovered solvent II is condensed by the condensation device I and then returned to the PVDF reverse analysis device for recycling.

[0082] The obtained solid phase component I is contacted with the solvent III in a PET dissolution device to perform a second dissolution, and the PET in the solid phase component I is dissolved in the solvent III. The solid phase component I is then transported to a third solid-liquid separation device to perform a third solid-liquid separation to obtain a liquid phase component III and a solid phase component III.

[0083] The obtained liquid phase component III and solvent IV are contacted in a PVDF reverse analysis device to perform a second reverse analysis. Under the action of solvent IV, PET is precipitated from the liquid phase component III, and then transported to a fourth solid-liquid separation device for a fourth solid-liquid separation to obtain a liquid phase component IV and a wet solid phase component IV';

[0084] The obtained wet solid phase component IV' is transported to a vacuum drying device for vacuum drying to obtain a solid phase component IV and a vacuum drying liquid; the obtained liquid phase component IV and the vacuum drying liquid are transported to a distillation tower II for distillation to recover solvent III and solvent IV; the recovered solvent III is condensed by a condensation device II and then returned to the PET dissolution device for recycling, and the recovered solvent IV is condensed by a condensation device II and then returned to the PET reverse analysis device for recycling.

[0085] In a preferred embodiment of the present invention, the system further comprises a pre-treatment unit, wherein the pre-treatment unit comprises a cleaning device, a drying device and a crushing device.

[0086] In a preferred embodiment of the present invention, the present invention does not specifically limit the PVDF dissolving device, the fine filtering device, the PVDF reverse analysis device, the PET dissolving device and the PET reverse analysis device, the first solid-liquid separation device, the second solid-liquid separation device, the third solid-liquid separation device, the fourth solid-liquid separation device, the roasting device, the freeze-drying device, the vacuum drying device, the distillation tower I, the distillation tower II, the cleaning device, the drying device and the crushing device, and can be specifically selected according to actual needs.

[0087] Among them, the present invention needs to be particularly characterized in that the first solid-liquid separation device, the second solid-liquid separation device, the third solid-liquid separation device and the fourth solid-liquid separation device can be the same intermittently used device or multiple different devices. Similarly, the distillation tower I and the distillation tower II can be the same intermittently used device or multiple different devices.

[0088] The present invention will be described in detail by way of examples. The waste photovoltaic back sheet is cleaned, dried and crushed to a particle size of 1-2 cm. By elemental analysis and subtraction method, the content of PET in the waste photovoltaic back sheet is 80 wt%, the content of PVDF is 5 wt%, the content of TiO2 is 2 wt%, and the content of polymer film is 13 wt%.

[0089] The PVDF dissolving device and the PET dissolving device are countercurrent leaching devices with stirring and heating functions, the PVDF decomposition device and the PET decomposition device are stirrers with heating functions, the first solid-liquid separation device, the second solid-liquid separation device, the third solid-liquid separation device and the fourth solid-liquid separation device are the same, all of which are filters with a mesh pore size of less than 1 mm, and the fine filtration device is a filter with a mesh pore size of less than 50 nm.

[0090] Example 1

[0091] (1) contacting 500 g of waste photovoltaic backsheet with 5000 g of solvent I (a mixed liquid of dimethyl sulfoxide and N-methylpyrrolidone, with a mass ratio of 1:1) in a PVDF dissolution device, performing a first dissolution at 90° C. and 0.1 MPa, stirring for 50 min, and then transporting the mixture to a first solid-liquid separation device for a first solid-liquid separation, thereby obtaining a liquid phase component I and a solid phase component I;

[0092] (2) transporting the obtained liquid phase component I to a fine filtering device for fine filtering to obtain filter residue and liquid phase component I'; calcining the obtained filter residue at 800°C for 4h to obtain recovered TiO2; wherein the mass of the recovered TiO2 is 9.9g and the purity is 99.7%;

[0093] (3) contacting the obtained liquid phase component I' with deionized water in a PVDF reverse analysis device, performing a first reverse analysis at 70°C and 0.1 MPa, and transporting it to a second solid-liquid separation device for a second solid-liquid separation after 50 minutes to obtain a liquid phase component II and a wet solid phase component II'; wherein the mass ratio of the liquid phase component I' to the deionized water is 1:3;

[0094] The obtained wet solid phase component II' was transported to a freeze dryer and dried at -104°C and 0.5 MPa for 24 hours to obtain a solid phase component II and a freeze-dried liquid; wherein the solid phase component II was PVDF white particles with a mass of 24.8 g and a purity of 99.6%;

[0095] The obtained liquid phase component II and the freeze-dried liquid are transported to a continuous distillation tower I for distillation to recover dimethyl sulfoxide, N-methylpyrrolidone and water; the recovered dimethyl sulfoxide and N-methylpyrrolidone are condensed by a condensing device and returned to step (1) for recycling, and the recovered water is condensed by a condensing device and returned to step (2) for recycling;

[0096] (4) contacting the obtained solid phase component I with solvent III (a mixture of trifluoroacetic acid and hexafluoroisopropanol, with a mass ratio of 1:1) in a PET dissolution device, performing a second dissolution at 40° C. and 0.1 MPa, stirring for 50 min, and then transferring to a third solid-liquid separator for a third solid-liquid separation to obtain a liquid phase component III and a solid phase component III; wherein the mass ratio of the solid phase component I to the solvent III is 1:10, and the solid phase component III is a white polymer film with a mass of 65.7 g;

[0097] (5) contacting the obtained liquid phase component III with deionized water in a PET reverse analysis device, performing a second reverse analysis at 40° C. and 0.1 MPa, and transporting it to a fourth solid-liquid separation device for a fourth solid-liquid separation after 50 minutes to obtain a liquid phase component IV and a wet solid phase component IV′; wherein the mass ratio of the liquid phase component III to the deionized water is 1:3;

[0098] The obtained wet solid phase component IV' was transported to a vacuum drying oven and vacuum dried at 80°C and 200 mbar for 24 hours to obtain a solid phase component IV and a vacuum dried liquid; the solid phase component IV was PET white particles with a mass of 398.5 g and a purity of 99.5%;

[0099] The obtained liquid phase component IV and the vacuum dried liquid are transported to a continuous distillation tower II for distillation to recover trifluoroacetic acid, hexafluoroisopropanol and water; the recovered trifluoroacetic acid and hexafluoroisopropanol are condensed by a condensing device and returned to step (3) for recycling, and the recovered water is condensed by a condensing device and returned to step (4) for recycling.

[0100] Example 2

[0101] The method is the same as Example 1, except that: in step (1), solvent I is a mixed liquid of dimethyl sulfoxide and N-formylmorpholine, and the mass ratio of dimethyl sulfoxide to N-formylmorpholine is 1:0.2; the first dissolution is carried out at 95° C. and 0.1 MPa, and after stirring for 80 minutes, the mixture is transported to a first solid-liquid separation device for a first solid-liquid separation.

[0102] Among them, the separated recycled TiO2 has a mass of 9.7g and a purity of 99.3%; the separated PVDF is white particles with a mass of 24.2g and a purity of 98.9%; the separated polymer film is white with a mass of 66.6g; the separated PET is white particles with a mass of 397.9g and a purity of 99.3%.

[0103] Example 3

[0104] The same as Example 1, except that in step (3), the mixed solution of trifluoroacetic acid and hexafluoroisopropanol is replaced by trifluoroacetic acid in equal amounts.

[0105] Among them, the separated recycled TiO2 has a mass of 9.9g and a purity of 99.5%; the separated PVDF is white particles with a mass of 24.5g and a purity of 99.6%; the separated polymer film is white with a mass of 83.8g; the separated PET is white particles with a mass of 383.5g and a purity of 99.4%.

[0106] By comparing Example 1 with Example 3, it can be seen that the mixed solution of trifluoroacetic acid and hexafluoroisopropanol has a better dissolving effect on PET than trifluoroacetic acid. When trifluoroacetic acid is used alone to dissolve solid phase component I, under the same operating conditions, part of the PET is not fully dissolved. In the third solid-liquid separation, the undissolved PET enters the solid phase component III together with the polymer film, resulting in a slightly higher yield of the polymer film and a slightly lower yield of PET.

[0107] Comparative Example 1

[0108] The same as Example 1, except that: in step (1), the mixed solution of dimethyl sulfoxide and N-methylpyrrolidone is replaced with N-methylpyrrolidone in equal amounts, the first dissolution is carried out at 90° C. and 0.1 MPa, and after stirring for 3 hours, it is transported to the first solid-liquid separation device for the first solid-liquid separation to obtain liquid component I and solid component I.

[0109] Among them, the separated recycled TiO2 has a mass of 9.9g and a purity of 99.6%; the separated PVDF is white particles with a mass of 21.2g and a purity of 99.6%; the separated polymer film is white with a mass of 66.1g; the separated PET is white particles with a mass of 397.5g and a purity of 99.5%.

[0110] Among them, by comparing Example 1 and Comparative Example 1, it can be seen that under the same conditions, the recovery amount of PVDF when using N-methyl pyrrolidone alone as solvent I is slightly less than the recovery amount of PVDF when using a mixed solution of dimethyl sulfoxide and N-methyl pyrrolidone as solvent I, and the recovery effects of the two are basically equivalent. However, the dissolution time required in Comparative Example 1 is significantly longer, more than three times that in Example 1. It can be seen that the mixed use of dimethyl sulfoxide and N-methyl pyrrolidone can not only significantly increase the dissolution rate of PVDF, shorten the dissolution time, but also improve the dissolution effect of PVDF and increase the recovery rate of PVDF.

[0111] Comparative Example 2

[0112] The same as Example 1, except that: in step (2), the obtained wet solid phase component II' is transported to a vacuum drying oven and vacuum dried at 100°C, 200 mbar for 24 hours to obtain a solid phase component II and a vacuum-dried liquid; the obtained liquid phase component II and the vacuum-dried liquid obtained in step (2) are sent to a continuous distillation tower for distillation.

[0113] Among them, the separated recycled TiO2 has a mass of 9.9g and a purity of 99.6%; the separated PVDF is pink porous particles with a mass of 26.9g and a purity of 92.4%; the separated polymer membrane is white with a mass of 66.3g; the separated PET is white particles with a mass of 397.3g and a purity of 99.5%.

[0114] Among them, the mass of PVDF recovered in Comparative Example 3 is relatively large, indicating that vacuum drying cannot effectively remove the dimethyl sulfoxide and N-methyl pyrrolidone with large viscosity and high boiling point wrapped in PVDF particles. The recovered PVDF is pink, indicating that PVDF has been decomposed. This is because the boiling points of dimethyl sulfoxide and N-methyl pyrrolidone are relatively high. In order to obtain a better drying effect, the processing time of vacuum drying is relatively long. Dimethyl sulfoxide and N-methyl pyrrolidone are acidic in themselves. During the long vacuum drying process, dimethyl sulfoxide and N-methyl pyrrolidone will slowly react with PVDF, causing PVDF to change color.

[0115] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for recycling waste photovoltaic backsheets, characterized in that: The method comprises the following steps: (1) contacting a waste photovoltaic backsheet with a solvent I to perform a first dissolution to obtain a liquid phase component I and a solid phase component I; wherein the waste photovoltaic backsheet comprises PVDF, PET, TiO2 and a polymer film; the solvent I is selected from at least two of dimethyl sulfoxide, N-methylpyrrolidone and N-formylmorpholine; wherein the liquid phase component I comprises PVDF, solvent I and TiO2; (2) finely filtering the liquid component I to obtain a liquid component I' and a filter residue, wherein the filter residue is TiO2; (3) contacting the liquid phase component I' with a solvent II, performing a first reverse analysis, and obtaining a liquid phase component II and a solid phase component II; wherein the solvent II is selected from one or more of water, ethanol, and toluene; and the solid phase component II is PVDF; (4) contacting the solid phase component I with a solvent III for a second dissolution to obtain a liquid phase component III and a solid phase component III; wherein the solvent III is selected from one or more of trifluoroacetic acid, hexafluoroisopropanol, o-chlorophenol, and chloroform; and the solid phase component III is a polymer film; (5) contacting the liquid phase component III with a solvent IV and performing a second reverse analysis to obtain a liquid phase component IV and a solid phase component IV; wherein the solvent IV is selected from one or more of water, ethanol, and toluene, and the solid phase component IV is PET.

2. The recycling method according to claim 1, wherein: Based on the total mass of the waste photovoltaic backsheet, the waste photovoltaic backsheet has a PET content of 60-85wt%, a PVDF content of 5-15wt%, a TiO2 content of 2-10wt%, and a polymer film content of 10-30wt%; Preferably, the solvent I is dimethyl sulfoxide and N-methylpyrrolidone; further preferably, the mass ratio of dimethyl sulfoxide to N-methylpyrrolidone is 1:0.01-1.5, preferably 1:0.6-1.2; Preferably, the mass ratio of the waste photovoltaic backsheet to the solvent I is 1:5-20, preferably 1:7-12; Preferably, the operating conditions of the first dissolution include: a first dissolution temperature of 70-120°C, preferably 85-95°C; a first dissolution pressure of 0.05-0.5MPa, preferably 0.1-0.3MPa; a first dissolution time of 10-100min, preferably 30-60min; Preferably, after the first dissolution is completed, a first solid-liquid separation is performed to obtain a liquid phase component I and a solid phase component I.

3. The recovery method according to claim 1 or 2, wherein: The fine filtration is carried out in a filter with a pore size of ≤100 nm, preferably ≤50 nm; Preferably, the step (2) further comprises: roasting the filter residue to obtain recovered TiO2.

4. The recovery method according to any one of claims 1 to 3, wherein: The solvent II is water, preferably deionized water; Preferably, the mass ratio of the liquid component I' to the solvent II is 1:1-5, preferably 1:2-3; Preferably, the operating conditions of the first reverse analysis include: the first reverse analysis temperature is 50-90°C, preferably 60-80°C; the first reverse analysis pressure is 0.05-0.5MPa, preferably 0.1-0.3MPa; the first reverse analysis time is 20-80min, preferably 40-60min.

5. The recovery method according to any one of claims 1 to 4, wherein: After the first reverse analysis is completed, a second solid-liquid separation is performed to obtain a liquid phase component II and a wet solid phase component II'; wherein the liquid phase component II includes solvent I and solvent II; Preferably, the wet solid phase component II' is freeze-dried to obtain a solid phase component II and a freeze-dried liquid; Preferably, the freeze-drying operating conditions include: freeze-drying temperature of -115°C to -90°C, preferably -105°C to -100°C; freeze-drying pressure of 0.2-0.8MPa, preferably 0.4-0.6MPa; freeze-drying time of 12-14h, preferably 24-36h; Preferably, the liquid component II and / or the freeze-dried liquid are distilled to recover the solvent I and the solvent II.

6. The recovery method according to any one of claims 1 to 5, wherein: The solvent III is trifluoroacetic acid and / or hexafluoroisopropanol, preferably trifluoroacetic acid and hexafluoroisopropanol; Further preferably, the mass ratio of trifluoroacetic acid to hexafluoroisopropanol is 1:0.1-2, preferably 1:0.5-1.5; Preferably, the mass ratio of the solid phase component I to the solvent III is 1:5-25, preferably 1:10-15; Preferably, the operating conditions of the second dissolution include: the second dissolution temperature is 25-120°C, preferably 30-55°C; the second dissolution pressure is 0.05-0.5MPa, preferably 0.1-0.3MPa; the second dissolution time is 10-100min, preferably 30-60min; Preferably, after the second dissolution is completed, a third solid-liquid separation is performed to obtain a liquid phase component III and a solid phase component III.

7. The recovery method according to any one of claims 1 to 6, wherein: The solvent IV is water, preferably deionized water; Preferably, the mass ratio of the liquid component III to the solvent IV is 1:1-5, preferably 1:2-3; Preferably, the operating conditions of the second reverse analysis include: the second reverse analysis temperature is 25-90°C, preferably 30-55°C; the second reverse analysis pressure is 0.05-0.5MPa, preferably 0.1-0.3MPa; the second reverse analysis time is 20-80min, preferably 40-60min.

8. The recovery method according to any one of claims 1 to 7, wherein: After the second reverse analysis is completed, a fourth solid-liquid separation is performed to obtain a liquid phase component IV and a wet solid phase component IV'; Preferably, the wet solid phase component IV' is vacuum dried to obtain a solid phase component IV and a vacuum dried liquid; Preferably, the liquid phase component IV and / or the vacuum dried liquid are distilled to recover the solvent III and the solvent IV.

9. A recycling system for waste photovoltaic backsheets, characterized in that: The recovery system comprises a PVDF dissolving device (1), a fine filtering device (2), a PVDF reverse analysis device (3), a PET dissolving device (4) and a PET reverse analysis device (5); The PVDF dissolving device (1) is connected to the fine filtering device (2) and the PET dissolving device (5) respectively, the fine filtering device (2) is connected to the PVDF reverse analysis device (3), and the PET dissolving device (4) is connected to the PET reverse analysis device (5).

10. The recycling system according to claim 9, wherein: The system further comprises a first solid-liquid separation device (6), a second solid-liquid separation device (7), a third solid-liquid separation device (8) and a fourth solid-liquid separation device (9); The first solid-liquid separation device (6) is connected to the PVDF dissolving device (1), the fine filtering device (2) and the PET dissolving device (4) respectively; the second solid-liquid separation device (7) is connected to the PVDF reverse precipitating device (3); the third solid-liquid separation device (8) is connected to the PET dissolving device (4) and the PET reverse precipitating device (5); the fourth solid-liquid separation device (9) is connected to the PET reverse precipitating device (5); Preferably, the system further comprises a roasting device (10), wherein the roasting device (10) is connected to the fine filtering device (2); Preferably, the recovery system further comprises a freeze drying device (11), a vacuum drying device (12), a distillation tower I (13) and a distillation tower II (14); wherein the freeze drying device (11) is connected to the second solid-liquid separation device (7) and the distillation tower I (13), respectively, and the distillation tower I (13) is also connected to the PVDF dissolution device (1) and the PVDF decomposition device (3), respectively; the vacuum drying device (12) is connected to the fourth solid-liquid separation device (9) and the distillation tower II (14), and the distillation tower II (14) is also connected to the PET dissolution device (4) and the PET decomposition device (5), respectively.

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