Method for recycling waste photovoltaic module cells with a green solvent and recycling materials

Abstract

The present invention belongs to the technical field of photovoltaic module recycling, and particularly relates to a method for recycling waste photovoltaic module cells with a green solvent and a recycling material. The method comprises the steps of: 1) placing the front side of the waste photovoltaic module face down and heating it to 150-180 °C to peel off the glass; 2) removing the backsheet to obtain a module containing only the front EVA layer, the silicon wafer and the back EVA layer; 3) placing the module in the inner container, pouring in anhydrous ethanol, and heating and reacting at 150-180 °C for 0.80-1.2 hours to separate the back EVA layer from the silicon wafer, obtaining the back EVA layer and the remaining module; 4) placing the remaining module in the inner container, adding an aqueous sodium carbonate solution with a concentration of 0.2-0.8 mol / L, and heating and reacting at 180-220 °C for 5 hours to separate the front EVA layer from the silicon wafer, obtaining the front EVA layer and the silicon wafer. The present invention can simply, conveniently and efficiently separate the EVA in the module and recycle the cells.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic module recycling, and particularly relates to a method for recycling waste photovoltaic module cells with a green solvent and a recycling material. Background Art

[0002] The service life of photovoltaic modules is usually 20 - 25 years, which means that a large number of waste photovoltaic modules will gradually enter the scrapping period in the next few years. Waste photovoltaic modules contain a large amount of valuable materials such as high-purity silicon, silver, and aluminum. If they cannot be effectively recycled, it will not only cause waste of resources but also pollute the environment. Therefore, developing efficient and environmentally friendly recycling technologies has important economic and environmental significance. Traditional methods for recycling photovoltaic modules mainly include mechanical treatment, heat treatment, and chemical treatment. Mechanical treatment usually includes crushing and screening, but this method cannot effectively separate high-purity cells; heat treatment methods involve high-temperature incineration, which not only consumes a large amount of energy but also produces harmful gases and a large amount of carbon emissions. Although chemical treatment methods can achieve a relatively high recovery rate, they usually use strong acids, strong bases, or organic solvents, resulting in environmental pollution and operation safety problems.

[0003] Currently, the treatment methods for photovoltaic modules mainly include physical methods, mechanical methods, and pyrolysis methods. Physical methods effectively recycle glass, aluminum frames, plastics, and silicon materials through means such as mechanical separation, crushing, and screening. The advantages are simple operation and mature technology, but there are limitations in the recovery of dust, noise, and high-purity materials. Mechanical methods combine means such as crushing, screening, and magnetic separation to process large-scale photovoltaic modules. Although equipment improvement has improved the separation efficiency and purity, it is prone to secondary pollution and has poor separation effects on composite materials. Pyrolysis methods use high temperatures to separate organic and inorganic substances and recover high-purity metals and silicon, but high-temperature conditions will produce harmful gases and waste gases, and have high energy consumption and high equipment costs, limiting large-scale applications. In contrast, ethanol and sodium carbonate have significant environmental protection advantages as green solvent methods for treating photovoltaic modules. Ethanol can dissolve and separate the EVA on the upper and lower surfaces, recover the cells and metal electrodes in the module. The treatment process is mild and does not produce harmful gases. Ethanol can be recycled, reducing the treatment cost and environmental burden. Sodium carbonate is used to decompose and remove the encapsulation material, releasing the cells and glass. The operation is simple, the treatment efficiency is high, and there is no harmful gas emission, which is more environmentally friendly. Generally speaking, compared with traditional methods, the ethanol and sodium carbonate green solvent method has obvious advantages in terms of environmental protection, treatment efficiency, and cost-effectiveness. At the same time, after treatment with ethanol and sodium carbonate, the EVA will not swell and can be used for non-destructive recovery of silicon wafers. Summary of the Invention

[0004] To address the deficiencies of the prior art, the present invention provides a method and recycling materials for recovering used photovoltaic module cells using green solvents. The present invention uses ethanol and sodium carbonate solution as green solvents to efficiently separate the EVA on the upper and lower surfaces of photovoltaic modules and recover the cells and other valuable materials therein, so as to achieve environmentally friendly and economical material reuse. The present invention can simply, conveniently and efficiently separate the EVA in the module and recover the cells.

[0005] The technical solutions provided by the present invention are as follows:

[0006] A method for recovering used photovoltaic module cells using green solvents, comprising the following steps:

[0007] 1) Place the front side of the used photovoltaic module face down on a heating table, heat it to 115 - 125 °C, and peel off the glass after heating;

[0008] 2) Continue to peel off the backplane from the module obtained in step 1) to obtain a module containing only the front EVA layer (i.e., the upper surface EVA), silicon wafers, and the back EVA layer (i.e., the lower surface EVA);

[0009] 3) Place the module obtained in step 2) into an inner container, pour in anhydrous ethanol, and heat and react at 150 - 180 °C for 0.80 - 1.2 hours. The back EVA layer is separated from the silicon wafers to obtain the back EVA layer and the remaining module;

[0010] 4) Place the remaining module obtained in step 3) into an inner container, add an aqueous sodium carbonate solution with a concentration of 0.2 - 0.8 mol / L, and heat and react at 180 - 220 °C for 5 hours. The front EVA layer is separated from the silicon wafers to obtain the front EVA layer and the silicon wafers.

[0011] In the above technical solutions:

[0012] By using anhydrous ethanol and heating at a relatively low temperature, the back EVA can be separated without swelling the EVA and avoiding damage to the silicon wafers;

[0013] By using an aqueous sodium carbonate solution and heating at a relatively low temperature, the front EVA layer can be separated.

[0014] Specifically, in step 1), heat to 180 °C.

[0015] Specifically, in step 3), pour in anhydrous ethanol until the module is submerged.

[0016] Specifically, in step 3), heat and react at 200 °C for 1 hour.

[0017] Further, after step 3), rinse and wash the remaining module, naturally dry the excess water, and then proceed to the next step.

[0018] Specifically, in step 4), an aqueous sodium carbonate solution is added until the remaining components are submerged.

[0019] Specifically, in step 4), the concentration of the aqueous sodium carbonate solution is 0.3 mol / L.

[0020] Specifically, in step 4), the reaction is heated at 200 °C for 5 hours.

[0021] Further, in step 4), the front EVA film is taken out and filtered to obtain a pure silicon wafer.

[0022] The present invention also provides a recycled material separated according to the above method.

[0023] Specifically, the recycled silicon wafer is a whole silicon wafer.

[0024] In the above technical solution, during the chemical immersion process, the EVA will not swell and the silicon wafer will not be corroded, so the silicon wafer will not be broken.

[0025] Specifically, the recycled silicon wafer has a complete silver grid line or aluminum electrode.

[0026] In the above technical solution, neither the physical disassembly nor the chemical immersion step will corrode the silver grid line or...

[0027] Advantages of the present invention:

[0028] 1) The chemical solvents used in the present invention are all green and pollution-free solvents, which have little impact on the natural environment;

[0029] 2) The chemical solvents used in the present invention can be recycled repeatedly, greatly reducing the cost during the recycling process;

[0030] 3) The advantage of the present invention compared with the prior art is that most of the existing methods for separating EVA films remove the EVA film by pyrolysis at about 500 °C. Since a relatively high temperature is reached during the recycling process and some toxic gases are generated. Therefore, the pyrolysis recycling of solar cells has too high energy consumption requirements and certain environmental pollution;

[0031] 4) This method uses wet method to separate EVA in photovoltaic modules, and has good effect on purifying solar cells. It not only avoids the environmental pollution caused by pyrolyzing EVA, but also recycles and reuses silicon wafers, turning waste into treasure, improving economic value and having strong practicability. Description of the Drawings

[0032] Figure 1 It is a composition structure diagram of a photovoltaic module in the embodiment.

[0033] Figure 2It is a diagram of the remaining components after separating the back EVA layer in Example 1, where part a is the black component, and part b is the black lower surface EVA film and aluminum electrode.

[0034] Figure 3 It is a diagram of the silicon wafers recovered in Example 1.

[0035] Figure 4 It is a diagram of the white upper surface EVA film silicon wafers recovered in Example 1.

[0036] Figure 5 It is a cross-sectional SEM diagram of the component before treatment in Example 1.

[0037] Figure 6 It is a cross-sectional EDS diagram of the component before treatment in Example 1. Detailed implementation mode

[0038] The principles and features of the present invention will be described below. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0039] Unless otherwise specified, the test methods used in the invention examples are all conventional methods; the materials, reagents, etc. used, unless otherwise specified, are reagents and materials that can be obtained from commercial channels.

[0040] Example 1

[0041] A method for recycling waste photovoltaic module battery wafers by a green solvent method, comprising the following steps:

[0042] (1) Cutting the photovoltaic panel.

[0043] Remove the aluminum frame and junction box from the retired photovoltaic panel, place the remaining photovoltaic panel in an open space, and slowly cut several 2×2 cm components with a angle grinder.

[0044] (2) Pyrolyzing the glass.

[0045] Place the cut component on a heating table at 180 °C and manually peel off the glass on the component, etc.

[0046] (3) Preparation of ethanol-separated lower surface EVA

[0047] ① Weigh the anhydrous ethanol solution (concentration: analytical pure) with a measuring cylinder. The solid-liquid ratio of the peeled component to anhydrous ethanol is 1:15 g / mL. Add it to a tetrafluoroethylene inner liner, and place the tetrafluoroethylene inner liner into a hydrothermal autoclave with a pressure less than 3 Mpa.

[0048] ② Preferably, place the hydrothermal autoclave in an oven and keep it at 200 °C for 1 hour.

[0049] Take out the hydrothermal reactor after the reaction in step ② is completed, open the Teflon inner liner, and take out the components with tweezers.

[0050] Wash the taken-out components and place them on a petri dish. The petri dish should contain the EVA film on the lower surface and the 1×1 cm components.

[0051] (4) Preparation of separating the upper surface EVA with sodium carbonate aqueous solution

[0052] ① Use a spatula to take out 1.59 g of solid from anhydrous sodium carbonate.

[0053] ② Place 1.59 g of anhydrous sodium carbonate solid in a beaker and make up the volume to the mark in a 50 mL volumetric flask.

[0054] ③ Put the 1×1 cm components processed in step (3) into the Teflon inner liner again.

[0055] ④ Pour 25 mL of the sodium carbonate liquid made up to the mark in ② into the inner liner.

[0056] ⑤ Put the inner liner processed in ④ into a hydrothermal reactor with a pressure less than 3 Mpa.

[0057] ⑥ Preferably, put the hydrothermal reactor into an oven and keep it at 200 °C for 5 hours.

[0058] ⑦ Take out the hydrothermal reactor after the reaction in step ⑥ is completed, open the Teflon inner liner, and take out the components with tweezers.

[0059] ⑧ The components taken out with tweezers in step ⑦ are the upper EVA film, the remaining sodium carbonate liquid in the inner liner and the detached battery wafers.

[0060] (5) Recycling of battery wafers

[0061] ① Pour the liquid and battery wafers in the Teflon inner liner in step (4) into a beaker.

[0062] ② Pour the mixture in the beaker in ① into a Buchner funnel.

[0063] ③ Connect the Buchner funnel in ② to a suction filtration device and start suction filtration.

[0064] ④ Pour out the liquid after suction filtration, and the battery wafers are obtained in the filter paper to complete the recycling.

[0065] Through the above steps, the EVA films on the upper and lower surfaces and the battery wafers in the photovoltaic module are obtained.

[0066] Figure 1 It is the composition structure diagram of the photovoltaic module.

[0067] Figure 2It is a diagram of the remaining components after separating the back EVA layer in Example 1, where part a is the black component and part b is the black lower-surface EVA film. The cracks were caused by manual handling of the glass. It can be seen that except for these cracks, there are no cracks caused by EVA swelling. Additionally, the lower-surface EVA film is black, and according to analysis, it should be black due to the presence of aluminum.

[0068] Figure 3 It is the silicon wafer recovered in Example 1. It can be seen that one side is white and the other side is black.

[0069] Figure 4 It is the white upper-surface EVA film silicon wafer recovered in Example 1.

[0070] Figure 5 It is the cross-sectional SEM of the component before treatment. Figure 6 It is the cross-sectional EDS diagram of the component before treatment. The middle spherical object in each diagram is aluminum, and ethanol acts on this area to achieve the separation of the lower-surface EVA.

[0071] Through Figure 2 , 3 , 4, 5, 6, it can be seen that the separated upper-surface EVA film and lower-surface EVA film show different colors due to different compositions on the film surface, which is caused by aluminum. Therefore, the mechanism of separating the lower-surface EVA film with absolute ethanol is different from that of separating the upper-surface EVA film with sodium carbonate aqueous solution.

[0072] Example 2

[0073] The method for recycling waste photovoltaic module cells refers to Example 1, with the difference that only absolute ethanol is used for separating each EVA layer. The results show that although the back EVA layer can be separated, the front EVA layer cannot be separated.

[0074] Example 3

[0075] The method for recycling waste photovoltaic module cells refers to Example 1, with the difference that sodium carbonate aqueous solution is directly used for separating each EVA layer. The results show that although the front EVA layer can be separated, the back EVA layer cannot be separated.

[0076] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for recycling waste photovoltaic module cells using green solvents, characterized in that: The following steps are involved: 1) Place the front side of the waste photovoltaic module facing down on a heating table, heat it to 150-180°C, and peel off the glass after heating; 2) further peeling off the assembly obtained in step 1) to remove the back plate, so as to obtain an assembly containing only the front EVA layer, the silicon wafer and the back EVA layer; 3) placing the component obtained in step 2) in an inner container, pouring in anhydrous ethanol, heating and reacting at 150-180° C. for 0.80-1.2 hours, separating the back EVA layer from the silicon wafer, and obtaining the back EVA layer and the remaining components; 4) placing the remaining components obtained in step 3) in an inner container, adding a sodium carbonate aqueous solution with a concentration of 0.2 to 0.8 mol / L, heating and reacting at 180 to 220° C. for 5 hours, separating the front EVA layer from the silicon wafer, and obtaining the front EVA layer and the silicon wafer; The silicon wafer has aluminum electrodes.

2. The method for recycling waste photovoltaic module cells with green solvent according to claim 1, characterized in that: In step 1), heating is performed to 180°C.

3. The method for recycling waste photovoltaic module cells with green solvent according to claim 1, characterized in that: In step 3), anhydrous ethanol is poured into the immersion component.

4. The method for recycling waste photovoltaic module cells with green solvent according to claim 1, characterized in that: In step 3), the reaction was heated at 180° C. for 1 hour.

5. The method for recycling waste photovoltaic module cells with green solvent according to claim 1, characterized in that: In step 4), an aqueous solution of sodium carbonate is added to submerge the remaining components.

6. The method for recycling waste photovoltaic module cells with green solvents according to claim 1, characterized in that: In step 4), the concentration of the sodium carbonate aqueous solution is 0.3 mol / L.

7. The method for recycling waste photovoltaic module cells with green solvent according to any one of claims 1 to 6, characterized in that: In step 4), the reaction was heated at 200° C. for 5 hours.

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