Method for separating glass and adhesive film of waste photovoltaic module by using recyclable green solvent

Abstract

The invention belongs to the technical field of photovoltaic module recovery, and particularly relates to a method for separating glass and an adhesive film of a waste photovoltaic module by using a recyclable green solvent. The method comprises the following steps: 1) disassembling and cutting a waste photovoltaic module; 2) washing the assembly with an absolute ethyl alcohol solution; 3) putting the assembly into an inner container, pouring a citric acid aqueous solution, and carrying out a heating reaction at 180-200 DEG C for 0.80-1.2 h to obtain an assembly composed of the back EVA adhesive film and the back plate, an assembly composed of the front EVA adhesive film and the silicon wafer, and tempered glass; and 4) separating the assembly from the toughened glass to respectively obtain the glass and each residual assembly. According to the method, the citric acid aqueous solution is adopted, through low-temperature heating, the glass can be separated from the front EVA, meanwhile, the back EVA can be separated from the silicon wafer, the EVA cannot be swelled, and the silicon wafer and metal on the surface of the silicon wafer cannot be damaged.

Description

Technical Field

[0001] The invention belongs to the technical field of photovoltaic module recycling, and in particular relates to a method for separating waste photovoltaic module glass and adhesive film using a recyclable green solvent. Background Art

[0002] The service life of photovoltaic modules is generally 20 to 25 years, which means that a large number of waste photovoltaic modules will be gradually scrapped 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 recycled efficiently, it will not only cause a waste of resources, but also have a negative impact on the environment. Therefore, the development of efficient and environmentally friendly recycling technology has important economic and environmental significance.

[0003] Traditional photovoltaic module recycling methods mainly include mechanical treatment, thermal treatment and chemical treatment. Mechanical treatment usually includes crushing and screening, but it cannot efficiently separate high-purity cells; thermal treatment involves high-temperature incineration, which not only consumes a lot of energy, but also produces harmful gases and a large amount of carbon emissions. Although chemical treatment methods have a higher recovery rate, they usually require the use of strong acids, strong alkalis or organic solvents, which pose environmental pollution and operational safety risks.

[0004] At present, the recycling and processing methods of photovoltaic modules mainly include physical method, mechanical method and pyrolysis method. The physical method effectively recycles glass, aluminum frame, plastic and silicon materials through mechanical separation, crushing and screening. The advantages are simple operation and mature process, but there are limitations of dust, noise and high-purity material recycling. The mechanical method combines crushing, screening and magnetic separation technologies to process large-scale photovoltaic modules. Although equipment improvements have improved separation efficiency and purity, it is easy to produce secondary pollution and has poor separation effect on composite materials. The pyrolysis method uses high temperature to separate organic and inorganic substances and recover high-purity metals and silicon materials, but high-temperature operation will produce harmful gases and waste gas, and high energy consumption and high equipment cost limit its large-scale application.

[0005] In the technical exploration of photovoltaic module recycling and treatment, it is necessary to comprehensively consider efficiency, environmental protection and economic costs in order to achieve the healthy and sustainable development of the photovoltaic industry. In contrast, citric acid solution has significant environmental advantages as a green solvent method for treating photovoltaic modules. The citric acid aqueous solution separates the EVA on the back and the encapsulated tempered glass, and recycles the glass in the module. The treatment process is gentle and does not produce harmful gases. Citric acid can be recycled more often, reducing treatment costs and environmental burdens. It is simple to operate, has high treatment efficiency and no harmful gas emissions, and is more environmentally friendly. Overall, compared with traditional methods, the ethanol and sodium carbonate green solvent method has obvious advantages in environmental protection, treatment efficiency and cost-effectiveness. At the same time, citric acid treatment will not cause EVA to swell, and can be used for non-destructive recovery of silicon wafers. Summary of the invention

[0006] To address the deficiencies of the prior art, the present invention provides a method for separating waste photovoltaic module glass and adhesive film using a recyclable green solvent. The present invention uses citric acid solution as a green solvent to efficiently separate the EVA and glass on the back of the photovoltaic module, and to recover the adhesive film and other valuable materials therein, so as to achieve environmentally friendly and economical material recycling. The present invention can simply, conveniently and efficiently separate the EVA in the module and recover the module glass.

[0007] The technical solution provided by the present invention is as follows:

[0008] A method for separating waste photovoltaic module glass and adhesive film by using a recyclable green solvent comprises the following steps:

[0009] 1) Dismantle the waste photovoltaic modules and cut them with an angle grinder;

[0010] 2) washing the assembly obtained in step 1) with an anhydrous ethanol solution to obtain a small photovoltaic assembly without an aluminum frame and a junction box;

[0011] 3) placing the component obtained in step 2) in an inner container, pouring in a citric acid aqueous solution, and heating the reaction at 180-200° C. for 0.80-1.2 hours to obtain a component consisting of a back EVA film and a back plate, a component consisting of a front EVA film and a silicon wafer, and a tempered glass;

[0012] 4) Separating the components obtained in step 3) from the tempered glass to obtain the glass and the remaining components respectively.

[0013] In the above technical solution:

[0014] By using citric acid aqueous solution and heating at a relatively low temperature, the glass and the front EVA can be separated, and the back EVA and the silicon wafer can be separated at the same time, without swelling the EVA and damaging the silicon wafer and the metal on the surface of the silicon wafer.

[0015] In the above technical solution, the bonding between the front EVA film and the tempered glass fails after step 3). If the two are not directly separated after the treatment of step 3), they can be separated by a slight separation operation.

[0016] Specifically, in step 3), the concentration of the citric acid aqueous solution is 1.4 mol / L to 1.6 mol / L.

[0017] Specifically, in step 3): pour the citric acid aqueous solution into the submerged component.

[0018] Specifically, in step 3), the reaction is heated at 180° C. for 1 hour.

[0019] Specifically, in step 3), the separated back EVA layer is a complete EVA film.

[0020] Specifically, in step 3), the remaining components are rinsed and the excess water is naturally dried, and then step 4) is performed.

[0021] Specifically, in step 4): the recovered silicon wafer has silver grid lines.

[0022] Specifically, in step 4), the silicon wafers in the remaining components are whole silicon wafers.

[0023] In the above technical solution, during the chemical immersion process, EVA will not swell and the silicon wafer will not be corroded, so the silicon wafer will not be broken.

[0024] In the above technical solution, neither the physical splitting nor the chemical immersion steps will corrode the silver grid lines.

[0025] Furthermore, the method further comprises step 5) which can be repeated multiple times: recovering the citric acid aqueous solution and repeating steps 1) to 4).

[0026] In the above technical solution, the citric acid aqueous solution can be reused. For example, after being reused 10 times, the concentration of the citric acid aqueous solution remains at 80% to 90%, and the volume remains at about 90%.

[0027] The invention also provides a silicon wafer separated according to the method.

[0028] Beneficial effects of the present invention:

[0029] 1) The chemical solvents used in the present invention are all green and pollution-free solvents, which have little impact on the natural environment;

[0030] 2) The chemical solvent used in the present invention can be recycled repeatedly, which greatly reduces the cost in the recycling process;

[0031] 3) The advantage of the present invention over the prior art is that the existing methods for separating EVA films mostly remove the EVA films by pyrolysis at about 500°C, which reaches a relatively high temperature during the recycling process and produces some toxic gases. The present invention can avoid the problem of excessive energy consumption and certain environmental pollution caused by pyrolysis recycling of battery cells;

[0032] 4) This method uses a wet method to separate the EVA in the photovoltaic module, and has a good effect in purifying the battery cells. It not only avoids the environmental pollution caused by the pyrolysis of EVA, but also can recycle and reuse the silicon wafers, turning waste into treasure, improving the economic value, and has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a composition structure diagram of the photovoltaic module in Example 1.

[0034] Figure 2 This is a diagram of the remaining components after the back EVA layer is separated in Example 1, wherein the left part is the assembly of the front EVA film and the silicon wafer, and the right part is the assembly of the back EVA film and the back panel.

[0035] Figure 3 This is a picture of the glass recovered in Example 1.

[0036] Figure 4 This is a cross-sectional SEM image of the component before processing.

[0037] Figure 5 This is the cross-sectional EDS image of the component before processing. DETAILED DESCRIPTION

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

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

[0040] Example 1

[0041] A method for recycling waste photovoltaic module cells by a green solvent method comprises the following steps:

[0042] 1) Cutting photovoltaic panels

[0043] Remove the aluminum frame and junction box from the retired photovoltaic panels, place the remaining photovoltaic panels on an open space, and use an angle grinder to slowly cut several 2×2cm components.

[0044] 2) Separate the back EVA layer with citric acid

[0045] ① Use a medicine spoon to take out 28.8 g of solid from the anhydrous citric acid solid.

[0046] ② Place 28.8 g of anhydrous citric acid solid in a beaker and dilute to volume in a 100 mL volumetric flask.

[0047] ③ Place the 2×2 cm component processed in step 1) into a tetrafluoroethylene liner.

[0048] ④ Pour 25mL of citric acid liquid prepared in ② into the inner container.

[0049] ⑤Put the inner container after treatment in ④ into a hydrothermal kettle with a pressure less than 3Mpa.

[0050] ⑥ Preferably, the hydrothermal kettle is placed in an oven and kept at 200° C. for 1 hour.

[0051] ⑦ Take out the hydrothermal reactor after the reaction in step ⑥, open the tetrafluoroethylene liner, and take out the components with tweezers.

[0052] ⑧Step ⑦ Use tweezers to remove and manually separate the EVA on the back to obtain the remaining components, with citric acid liquid remaining in the liner.

[0053] The separated components were washed and placed on a culture dish containing a 2×2 cm component consisting of a back EVA film and a back plate, and a 2×2 cm component consisting of a front EVA film and a silicon wafer.

[0054] 3) Recycling component glass

[0055] ① Introduce the liquid in the tetrafluoroethylene liner and the battery cells in step 2) into the beaker.

[0056] ② Use tweezers to pick up the glass on the component.

[0057] Through the above steps, a photovoltaic module with front EVA film and silicon wafer, a photovoltaic module with back EVA film and backboard, and tempered glass are obtained. The photovoltaic module with front EVA film and silicon wafer can be further separated by other technologies.

[0058] Figure 1 It is a composition structure diagram of the photovoltaic module in Example 1.

[0059] Figure 2 This is a diagram of the remaining components after the back EVA layer is separated in Example 1, where the left part is the assembly of the front EVA film and the silicon wafer, and the right part is the assembly of the back EVA film and the back plate. The cracks are cracks or fragments caused by manual peeling. In addition to these cracks, there are no cracks caused by EVA swelling.

[0060] Figure 3 This is the glass recovered in Example 1, which is mainly transparent.

[0061] Figure 4 This is a cross-sectional SEM of the component before treatment.

[0062] Figure 5 This is the cross-sectional EDS image of the module before processing. The sphere in the middle of the image is aluminum. The mechanism of action of citric acid is to destroy the chemical bond between the aluminum on the solar cell and the EVA film on the back, thus causing the EVA film on the back to fall off from the solar cell.

[0063] Example 2

[0064] The method for recycling waste photovoltaic module cells refers to Example 1, except that only anhydrous ethanol is used to separate the EVA layers. The results show that although the silicon wafer and the back EVA layer can be separated, and the silicon wafer and the front EVA layer can be separated, the ethanol is almost consumed after one use.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for separating waste photovoltaic module glass and adhesive film using a recyclable green solvent, characterized in that: The following steps are involved: 1) Dismantle the waste photovoltaic modules and cut them with an angle grinder; 2) washing the assembly obtained in step 1) with an anhydrous ethanol solution to obtain a small photovoltaic assembly without an aluminum frame and a junction box; 3) placing the component obtained in step 2) in an inner container, pouring in a citric acid aqueous solution, and heating the reaction at 180-200° C. for 0.80-1.2 hours to obtain a component consisting of a back EVA film and a back plate, a component consisting of a front EVA film and a silicon wafer, and a tempered glass; 4) Separating the components obtained in step 3) from the tempered glass to obtain the glass and the remaining components respectively.

2. The method for separating waste photovoltaic module glass and adhesive film by using a recyclable green solvent according to claim 1, characterized in that: In step 3), the concentration of the citric acid aqueous solution is 1.4 mol / L to 1.6 mol / L.

3. The method for separating waste photovoltaic module glass and adhesive film by using a recyclable green solvent according to claim 1, characterized in that: In step 3), pour the citric acid aqueous solution into the submerged components.

4. The method for separating waste photovoltaic module glass and adhesive film by using a recyclable 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 separating waste photovoltaic module glass and adhesive film by using a recyclable green solvent according to claim 1, characterized in that: In step 3), the separated back EVA layer is a complete EVA film.

6. The method for separating waste photovoltaic module glass and adhesive film by using a recyclable green solvent according to claim 1, characterized in that: In step 3), the remaining components are rinsed and the excess water is dried naturally, and then step 4) is performed.

7. The method for separating waste photovoltaic module glass and adhesive film by using a recyclable green solvent according to claim 1, characterized in that: In step 4): the silicon wafers in the remaining components are whole silicon wafers.

8. The method for separating waste photovoltaic module glass and adhesive film by using a recyclable green solvent according to claim 1, characterized in that: In step 4): the recovered silicon wafer has silver grid lines.

9. The method for separating waste photovoltaic module glass and adhesive film by recyclable green solvent according to any one of claims 1 to 8, characterized in that: The method further comprises step 5) which can be repeated multiple times: recovering the citric acid aqueous solution and repeating steps 1) to 4).

10. A silicon wafer separated by the method according to any one of claims 1 to 9.

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