Method for recovering silver from waste crystalline silicon photovoltaic module by green solvent hydrothermal method

Abstract

The invention belongs to the technical field of photovoltaic module recovery, and particularly relates to a method for recovering silver from a waste crystalline silicon photovoltaic module through a green solvent hydrothermal method. The method comprises the following steps: 1) cutting a waste photovoltaic module to obtain small photovoltaic modules without aluminum frames and junction boxes; 2) washing the assembly obtained in the step 1) with an absolute ethyl alcohol solution; (3) putting the assembly obtained in the step (2) into an inner container, pouring a sodium phosphate aqueous solution, carrying out heating reaction at 180-200 DEG C for 0.80-1.2 hours, and separating the front EVA layer from the silicon wafer to obtain the front EVA layer adhered with the silver grid line and the residual assembly; and 4) separating the silver grid line from the EVA layer, and recovering to obtain the silver grid line. Based on the sodium phosphate solution, most of silver grid lines (silicon silver) on the solar cell can be recycled.

Description

Technical Field

[0001] The invention belongs to the technical field of photovoltaic module recycling, and in particular relates to a method for recycling silver from waste crystalline silicon photovoltaic modules by a green solvent hydrothermal method. Background Art

[0002] The service life of photovoltaic modules is generally set at 20 to 25 years, which indicates that a large number of waste photovoltaic modules will enter the retirement stage in the next few years. These modules contain a lot of high-value materials such as silicon, silver, and aluminum. If they cannot be effectively recycled, it will not only be a huge waste, but also bring significant negative impacts to the ecological environment.

[0003] Traditionally, the recycling methods of photovoltaic modules are divided into three categories: mechanical treatment, thermal treatment and chemical treatment. Although mechanical treatment can achieve basic crushing and screening, it is difficult to extract high-purity cells; thermal treatment involves high-temperature incineration, which consumes huge energy and is accompanied by harmful gas emissions, increasing the carbon footprint; although chemical treatment has high recycling efficiency, it relies on strong acids, strong alkalis or organic solvents, which poses environmental pollution and operational safety risks.

[0004] Although there are many recycling methods such as physical, mechanical and pyrolysis, they all have their own limitations in terms of efficiency, environmental protection and economic cost. Although the physical method is mature, it is difficult to guarantee the recovery of high-purity materials; although the mechanical method has made progress in processing large-scale components, the problems of secondary pollution and separation of composite materials still need to be solved; although the pyrolysis method can recover high-purity metals and silicon, its high-temperature operation, high energy consumption and high equipment cost limit its wide application. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a method for recovering silver from waste crystalline silicon photovoltaic modules by a green solvent hydrothermal method. The method is based on a sodium phosphate solution, and through a mild treatment process, the EVA film is effectively separated, and most of the silver grid lines (silicon silver) on the solar cell can be recovered. The use of sodium phosphate not only reduces the processing cost, but also significantly reduces the environmental burden. The whole process is simple to operate, efficient, and has no harmful gas emissions throughout the process, which is extremely friendly to the environment. Compared with traditional methods, the sodium phosphate green solvent method shows obvious advantages in environmental protection, processing efficiency and cost-effectiveness.

[0006] The technical solution provided by the present invention is as follows:

[0007] A method for recovering silver from waste crystalline silicon photovoltaic modules by a green solvent hydrothermal method comprises the following steps:

[0008] 1) Cutting the waste photovoltaic modules to obtain small photovoltaic modules without aluminum frames and junction boxes;

[0009] 2) washing the component obtained in step 1) with an anhydrous ethanol solution;

[0010] 3) placing the component obtained in step 2) in an inner container, pouring in a sodium phosphate aqueous solution, heating and reacting at 180-200° C. for 0.80-1.2 hours, separating the front EVA layer from the silicon wafer, and obtaining a front EVA layer with silver grid lines attached thereto and the remaining components;

[0011] 4) Separating the silver grid wire from the EVA layer and recovering the silver grid wire.

[0012] In the above technical solution, sodium phosphate aqueous solution is used and heated at a relatively low temperature, which has the following effects:

[0013] Silicon nitride can be etched to separate the front EVA from the silicon wafer. Since the silver paste is brushed on the silicon nitride surface, the silver grid line is automatically separated from the silicon wafer.

[0014] The silver grid line will not be corroded during the chemical immersion process;

[0015] The chemical immersion process does not corrode or swell EVA, thus avoiding damage to the silicon wafer;

[0016] The aluminum back electrode can be etched to achieve the effect of etching aluminum and recovering silver;

[0017] Silicon nitride can be etched to separate the EVA surface from the silicon wafer.

[0018] Among them, sodium phosphate does not corrode EVA, which is an effect that treatment solutions such as sodium carbonate do not have. At the same time, sodium phosphate has a stronger etching effect on silicon nitride than sodium carbonate.

[0019] In step 4), physical separation can be used to separate the silver grid lines from the EVA layer.

[0020] Based on the above technical solution, neither the physical splitting nor the chemical immersion steps will corrode the silver grid lines.

[0021] Specifically, in step 3), pour the sodium phosphate aqueous solution into the submerged component.

[0022] Specifically, in step 3), the reaction is heated at 180°C or 200°C.

[0023] Specifically, in step 3), the reaction is heated for 1 h.

[0024] Specifically, in step 3), the weight percentage concentration of the sodium phosphate aqueous solution is 28 to 29.5 g / mL.

[0025] Specifically, step 3) also includes the following steps: recovering the sodium phosphate aqueous solution after the reaction.

[0026] Furthermore, after step 3), the remaining components are rinsed and the excess water is dried naturally before proceeding to the next step.

[0027] Furthermore, the method further comprises step 5): repeating steps 1) to 4), wherein step 2) in the repetition is performed using the recovered sodium phosphate aqueous solution.

[0028] Specifically: Step 4) The recovered silver grid lines are complete silver grid lines.

[0029] Specifically: in step 1), an angle grinder is used for cutting.

[0030] Beneficial effects of the present invention:

[0031] 1) The chemical solvents used in the present invention are all green and pollution-free solvents;

[0032] 2) The chemical solvent used in the present invention can be recycled repeatedly, which greatly reduces the cost in the recycling process;

[0033] 3) Compared with the prior art, the present invention has the advantage that the existing methods for separating silicon and silver mostly use nitric acid to remove the EVA film by soaking at about 70°C. Since highly oxidizing and volatile acids are used in the recovery process, some toxic gases will be generated. Therefore, the use of nitric acid to recover silicon and silver on the battery cell requires too much solvent oxidation, and there will be a certain loss of metal silver, as well as a certain amount of pollution to the environment. The technical solution of the present invention does not have this problem;

[0034] 4) The present invention uses a wet method to separate EVA (with silver grid lines adhered) in photovoltaic modules, and has a good effect of purifying silver grid lines. It not only avoids the pollution of the environment caused by dissolving silver with nitric acid, but also recycles and reuses silicon wafers, and has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural diagram of the photovoltaic module.

[0036] Figure 2 These are the SEM and EDS images of the front EVA film separated in Example 1.

[0037] Figure 3 This is a diagram of the assembly of the front EVA film and the silver grid line separated in Example 1. 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 examples are conventional methods; the materials and reagents used are commercially available reagents and materials unless otherwise specified.

[0040] Example 1

[0041] A method for recovering silver from waste crystalline silicon photovoltaic modules by a green solvent hydrothermal 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) Preparation of positive surface EVA for sodium phosphate separation

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

[0046] ② Place 28.8 g of anhydrous sodium phosphate solid in a beaker and make up 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 sodium phosphate liquid prepared in ② into the inner tank.

[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] ⑧The component removed with tweezers in step ⑦ is the positive EVA film, and the remaining sodium phosphate liquid and remaining components are in the liner.

[0053] The removed component is washed and placed on a culture dish, wherein there is an EVA film (with silver grid lines attached) on the front surface and a 2×2 cm component. The silver grid lines can be separated from the EVA by mechanical peeling, such as manual peeling.

[0054] 3) Recycling components

[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 component.

[0057] Figure 1It is a structural diagram of the photovoltaic module.

[0058] Figure 2 The following are SEM and EDS images of the front EVA film separated in Example 1. From the elements, it can be seen that the silver grid lines are attached to the film.

[0059] Figure 3 This is a diagram of the assembly of the front EVA film and the silver grid line separated in Example 1.

[0060] pass Figure 2 , 3 It can be seen that the front EVA film (with silver grid lines attached) can be separated.

[0061] Example 2

[0062] Referring to Example 1, the difference is that only anhydrous ethanol is used to separate the EVA layers. The results show that although the back EVA layer can be separated, the front EVA layer cannot be separated.

[0063] Example 3

[0064] Referring to Example 1, the difference is that sodium carbonate aqueous solution is directly used to separate each EVA layer. The results show that although the front EVA layer can be separated, the back EVA layer cannot be separated, and the EVA will be corroded. It is not corrosion, but the surface of the front EVA will undergo saponification reaction after being treated with sodium phosphate, and the film will become white and rough.

[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 recovering silver from waste crystalline silicon photovoltaic modules by a green solvent hydrothermal method, characterized in that: The following steps are involved: 1) Cutting the waste photovoltaic modules to obtain small photovoltaic modules without aluminum frames and junction boxes; 2) washing the component obtained in step 1) with an anhydrous ethanol solution; 3) placing the component obtained in step 2) in an inner container, pouring in a sodium phosphate aqueous solution, heating and reacting at 180-200° C. for 0.80-1.2 hours, separating the front EVA layer from the silicon wafer, and obtaining a front EVA layer with silver grid lines attached thereto and the remaining components; 4) Separating the silver grid wire from the EVA layer and recovering the silver grid wire.

2. The method for recovering silver from waste crystalline silicon photovoltaic modules by a green solvent hydrothermal method according to claim 1, characterized in that: In step 3), pour the sodium phosphate aqueous solution into the submerged component.

3. The method for recovering silver from waste crystalline silicon photovoltaic modules by a green solvent hydrothermal method according to claim 1, characterized in that: In step 3), the reaction is heated at 180°C or 200°C.

4. The method for recovering silver from waste crystalline silicon photovoltaic modules by a green solvent hydrothermal method according to claim 1, characterized in that: In step 3), the reaction was heated for 1 h.

5. The method for recovering silver from waste crystalline silicon photovoltaic modules by a green solvent hydrothermal method according to claim 1, characterized in that: In step 3), the weight percentage concentration of the sodium phosphate aqueous solution is 28-29.5 g / mL.

6. The method for recovering silver from waste crystalline silicon photovoltaic modules by a green solvent hydrothermal method according to claim 1, characterized in that: The step 3) also includes the following steps: recovering the sodium phosphate aqueous solution after the reaction.

7. The method for recovering silver from waste crystalline silicon photovoltaic modules by a green solvent hydrothermal method according to claim 6, characterized in that: The method further comprises step 5): repeating steps 1) to 4), wherein step 2) in the repetition is performed using the recovered sodium phosphate aqueous solution.

8. The method for recovering silver from waste crystalline silicon photovoltaic modules by a green solvent hydrothermal method according to claim 1, characterized in that: Step 4) The silver grid lines are recovered to be complete silver grid lines.

9. The method for recovering silver from waste crystalline silicon photovoltaic modules by a green solvent hydrothermal method according to claim 1, characterized in that: In step 1), an angle grinder is used for cutting.

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