A method for treating carbon contamination and EVA on the surface of a waste solar photovoltaic silicon wafer during recycling

Abstract

The application discloses a kind of waste solar photovoltaic silicon wafer recycling silicon wafer surface carbon pollution and EVA processing method, comprising the following steps: (1) the high-temperature heat treatment of waste solar photovoltaic panel assembly is placed in deionized water, normal temperature ultrasonic cleaning, drying;(2) then be placed in organic solvent, ultrasonic treatment;(3) the silicon wafer obtained after ultrasonic treatment is placed in deionized water, cleaning, recycling;The step (2) organic solvent is: polyether amine or dimethylformamide and butyl butyl hydroxy benzoate or glycol ethyl ether acetate composition.The application adopts the synergistic combination of polar solvent and permeability organic solvent, under the action of ultrasonic wave, EVA residue is dissolved efficiently and the peeling of surface carbon is promoted.

Description

Technical Field

[0001] This invention belongs to the field of solar silicon wafer recycling, specifically relating to a method for treating carbon contamination and residual EVA on the surface of waste solar photovoltaic silicon wafers during recycling. Background Technology

[0002] Photovoltaic products have a lifespan of 20 to 25 years. Since 2020, my country's solar photovoltaic products have begun to be scrapped one after another. It is predicted that photovoltaic solar modules will enter a period of large-scale scrapping in 2025, and a continuous peak period of scrapping will be reached around 2030.

[0003] A crucial step in the recycling of solar photovoltaic (PV) panels is the removal of EVA (ethylene-vinyl acetate copolymer). The photovoltaic silicon wafers with soldered leads are bonded with EVA to tempered glass on both sides, or tempered glass on one side and an organic backsheet on the other, forming a photovoltaic layer. This layer is then laminated, and junction boxes, frames, etc., are installed to form the solar PV module. EVA is a hot-melt adhesive that covers the entire PV panel, accounting for approximately 5% of the total weight of the module. High-temperature heat treatment utilizes the property of EVA to decompose at high temperatures, thus removing it. Because high-temperature heat treatment is easy to implement, relatively low-cost, and more adaptable than any chemical treatment method, it is widely used in the industry.

[0004] Existing chemical solvents such as trichloroethylene, o-dichlorobenzene, benzene, and toluene can dissolve EVA, but this process is time-consuming, often only causing swelling rather than complete dissolution. Firstly, the time required is long, ranging from 3-4 days to over a week, making it suitable only for laboratory settings and unsuitable for industrial production. Secondly, numerous production experiments have demonstrated that single or mixed organic solvents cannot achieve complete dissolution. Thirdly, there are no effective strategies to address the environmental issues associated with the large-scale use of organic solvents. Therefore, solvent removal of EVA is far less direct and efficient than high-temperature pyrolysis in large-scale industrial production.

[0005] High-temperature heat treatment to remove EVA has two disadvantages regarding the purity of recycled silicon wafers: EVA residue and carbon contamination on the silicon wafer surface. Through continuous exploration, this invention provides a reliable and effective method to remove EVA residue and carbon contamination from the silicon wafer surface. Summary of the Invention

[0006] The purpose of this invention is to remove EVA residue and carbon deposits generated during the high-temperature heat treatment process of waste solar photovoltaic panel modules.

[0007] A method for treating carbon contamination and EVA on the surface of waste solar photovoltaic silicon wafers during recycling includes the following steps: (1) Immerse the waste solar photovoltaic panel components after high-temperature heat treatment in deionized water, clean them with ultrasonic cleaning at room temperature, and dry them; (2) Then immerse it in an organic solvent and sonicate it; (3) The silicon wafers obtained after ultrasonic treatment are cleaned and recycled in deionized water; The organic solvent in step (2) is composed of polyetheramine or dimethylformamide and butyl butyl paraben or ethylene glycol ethyl ether acetate.

[0008] Preferably, the organic solvent is composed of polyetheramine and butylparaben.

[0009] Preferably, the volume ratio of polyetheramine or dimethylformamide to butylparaben or ethylene glycol ethyl ether acetate is (5.0-6.5):(3.5-5).

[0010] Preferably, the ultrasonic cleaning time in step (1) is 10-20 min and the power is 600-1000 W.

[0011] Preferably, the ultrasonic treatment in step (2) is performed at a temperature of 40-60°C for 30-60 minutes and a power of 400-800W.

[0012] Preferably, the cleaning in step (3) is ultrasonic cleaning.

[0013] Preferably, the ultrasonic cleaning is performed at room temperature for 10–20 minutes and with a power of 600–1000W.

[0014] Preferably, the drying temperature in step (1) is 120°C and the drying time is 30 min.

[0015] Advantages of this invention: This invention employs a synergistic combination of polar solvents and penetrating organic solvents to efficiently dissolve EVA residues and promote the stripping of surface carbon under ultrasonic action, effectively ensuring the purity of recycled silicon wafers. Attached Figure Description

[0016] Figure 1 This is a 100x microscope image of the surface of a silicon wafer after high-temperature heat treatment.

[0017] Figure 2 This is a 200x microscope image of the surface of a silicon wafer after high-temperature heat treatment.

[0018] Figure 3 This is a photograph of a silicon wafer after organic solvent treatment according to the present invention, taken under a 100x microscope.

[0019] Figure 4This is a photograph of a silicon wafer after organic solvent treatment according to the present invention, taken under a 200x microscope. Detailed Implementation

[0020] The present invention will be further described below with reference to implementation examples, but the scope of protection of the present invention is not limited to these embodiments.

[0021] Example 1 A method for treating carbon contamination and EVA on the surface of waste solar photovoltaic silicon wafers during recycling includes the following steps: (1) Immerse the waste solar photovoltaic panel components that have undergone high-temperature heat treatment in deionized water, at room temperature, under the condition of 600W power, ultrasonically clean for 20 minutes, and bake at 120℃ for 30 minutes. (2) Then immerse it in an organic solvent of polyetheramine and butylparaben in a volume ratio of 5.0:3.5 and sonicate it at 50°C and 400W for 60 min. (3) The silicon wafers obtained after ultrasonic treatment were cleaned in deionized water at room temperature for 20 minutes under a power of 600W and then recycled.

[0022] Waste solar photovoltaic panels that have undergone high-temperature heat treatment and those processed using the same method were compared under 100x and 200x microscopes. Figure 1 , Figure 3 and Figure 2 , Figure 4 The comparison shows that after treatment by the method of the present invention, the surface is clearly visible under 100x and 200x microscopes, and the EVA residue and carbon stains are thoroughly cleaned.

[0023] Example 2 A method for treating carbon contamination and EVA on the surface of waste solar photovoltaic silicon wafers during recycling includes the following steps: (1) Immerse the waste solar photovoltaic panel components that have undergone high-temperature heat treatment in deionized water, at room temperature, under the condition of 1000W power, ultrasonically clean for 10 minutes, and bake at 120℃ for 30 minutes. (2) Then immerse it in an organic solvent of polyetheramine and ethylene glycol ethyl ether acetate in a volume ratio of 6.0:4.0, and sonicate it for 60 min at 60°C and 600W. (3) The silicon wafers obtained after ultrasonic treatment are cleaned in deionized water at room temperature for 10 minutes under a power of 1000W and then recycled.

[0024] Example 3 A method for treating carbon contamination and EVA on the surface of waste solar photovoltaic silicon wafers during recycling includes the following steps: (1) Immerse the waste solar photovoltaic panel components that have undergone high-temperature heat treatment in deionized water, at room temperature, under the condition of 800W power, ultrasonically clean for 15 minutes, and bake at 120℃ for 30 minutes. (2) Then immerse it in an organic solvent of dimethylformamide and butylparaben in a volume ratio of 6.5:3.5, and sonicate it for 30 min at 40°C and 800W. (3) The silicon wafers obtained after ultrasonic treatment are cleaned in deionized water at room temperature for 15 minutes under a power of 800W and then recycled.

[0025] Example 4 A method for treating carbon contamination and EVA on the surface of waste solar photovoltaic silicon wafers during recycling includes the following steps: (1) Immerse the waste solar photovoltaic panel components that have undergone high-temperature heat treatment in deionized water, at room temperature, under the condition of 700W power, ultrasonically clean for 17 minutes, and bake at 120℃ for 30 minutes. (2) Then immerse it in an organic solvent of dimethylformamide and ethylene glycol ethyl ether acetate in a volume ratio of 5.5:5, and sonicate it for 50 min at 55°C and 700W. (3) The silicon wafers obtained after ultrasonic treatment were cleaned in deionized water at room temperature for 17 minutes under a power of 650W and then recycled.

Claims

1. A method for treating carbon contamination and EVA on the surface of waste solar photovoltaic silicon wafers during recycling, characterized in that, Includes the following steps: (1) Immerse the waste solar photovoltaic panel components after high-temperature heat treatment in deionized water, clean them with ultrasonic cleaning at room temperature, and dry them; (2) Then immerse it in an organic solvent and sonicate it; (3) The silicon wafers obtained after ultrasonic treatment are cleaned and recycled in deionized water; The organic solvent in step (2) consists of component A and component B, wherein component A is polyetheramine or dimethylformamide, and component B is butylparaben or ethylene glycol ethyl ether acetate.

2. The method for treating carbon contamination and EVA on the surface of waste solar photovoltaic silicon wafers in the recycling of waste solar photovoltaic silicon wafers according to claim 1, characterized in that, The organic solvent is composed of polyetheramine and butyl p-hydroxybenzoate.

3. The method for treating carbon contamination and EVA on the surface of waste solar photovoltaic silicon wafers in the recycling of waste solar photovoltaic silicon wafers according to claim 1, characterized in that, The volume ratio of polyetheramine or dimethylformamide to butylparaben or ethylene glycol ethyl ether acetate is (5.0-6.5):(3.5-5).

4. The method for treating carbon contamination and EVA on the surface of waste solar photovoltaic silicon wafers in the recycling of waste solar photovoltaic silicon wafers according to claim 1, characterized in that, The ultrasonic cleaning time in step (1) is 10-20 minutes, and the power is 600-1000W.

5. The method for treating carbon contamination and EVA on the surface of waste solar photovoltaic silicon wafers in the recycling of waste solar photovoltaic silicon wafers according to claim 1, characterized in that, The ultrasonic treatment in step (2) is performed at a temperature of 40-60℃ for 30-60 minutes and a power of 400-800W.

6. The method for treating carbon contamination and EVA on the surface of waste solar photovoltaic silicon wafers in the recycling of waste solar photovoltaic silicon wafers according to claim 4, characterized in that, The cleaning in step (3) is ultrasonic cleaning.

7. The method for treating carbon contamination and EVA on the surface of waste solar photovoltaic silicon wafers in the recycling of waste solar photovoltaic silicon wafers according to claim 5, characterized in that, The ultrasonic cleaning is performed at room temperature for 10–20 minutes and at a power of 600–1000W.

8. The method for treating carbon contamination and EVA on the surface of waste solar photovoltaic silicon wafers in the recycling of waste solar photovoltaic silicon wafers according to claim 6, characterized in that, The drying temperature in step (1) is 120°C and the drying time is 30 minutes.

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