Silicon wafer surface carbon dirt and EVA treatment method in waste solar photovoltaic silicon wafer recovery

Abstract

The invention discloses a silicon wafer surface carbon dirt and EVA treatment method in waste solar photovoltaic silicon wafer recovery, which comprises the following steps: (1) placing a waste solar photovoltaic panel assembly subjected to high-temperature heat treatment in deionized water, and carrying out normal-temperature ultrasonic cleaning and drying; (2) then putting into an organic solvent, and carrying out ultrasonic treatment; (3) putting the silicon wafer obtained after ultrasonic treatment into deionized water, cleaning and recycling; the organic solvent in the step (2) is composed of polyether amine or dimethylformamide and butyl p-hydroxybenzoate or ethylene glycol monoethyl ether acetate. According to the method, the polar solvent and the permeable organic solvent are synergistically combined, EVA residues are efficiently dissolved under the action of ultrasonic waves, and stripping of carbon on the surface is promoted.

Description

Technical Field

[0001] The invention belongs to the field of solar silicon wafer recycling, and in particular relates to a method for treating carbon pollution and residual EVA on the surface of waste solar photovoltaic silicon wafers during recycling. Background Art

[0002] Over the past decade, my country has achieved remarkable results in the promotion and use of green energy. For solar photovoltaic power generation alone, the cumulative installed capacity has reached 609.5GW by the end of 2023, with a compound annual growth rate of more than 50%. The China Photovoltaic Industry Association predicts that my country's solar photovoltaic installed capacity will continue to maintain a high growth rate before 2050, and the scale of photovoltaic power generation will leap from the "GW era" to the "TW era" in the future.

[0003] The lifespan of photovoltaic products is 20 to 25 years. Starting from 2020, my country's solar photovoltaics have begun to be scrapped one after another. It is predicted that photovoltaic solar panels will begin to enter a large-scale scrapping period in 2025, and will usher in a peak period of continuous scrapping after around 2030.

[0004] The recycling of solar photovoltaic panel components is a project that benefits both the country and the people. It not only disposes of mountains of industrial waste, but also recycles industrial products such as glass, aluminum, copper, silver, and silicon, making them brand new and put back into the recycling system of industrial production.

[0005] There is an important link in the recycling process of solar photovoltaic panel components - EVA (ethylene-vinyl acetate copolymer) removal. The photovoltaic silicon wafer with welded leads is bonded to tempered glass on both sides with EVA or to tempered glass on one side and organic backplane on the other side to form a photovoltaic layer. Through lamination, junction boxes, frames, etc. are installed to form solar photovoltaic components. EVA is a hot melt adhesive that covers the entire photovoltaic panel and accounts for about 5%W of the entire photovoltaic panel component. High-temperature heat treatment method uses the property of EVA to decompose at high temperatures to achieve the purpose of removing EVA. Because high-temperature heat treatment is easy to implement, low cost, and more adaptable than any chemical treatment method, it is widely used in the industry.

[0006] Existing chemical solvents such as trichloroethylene, o-dichlorobenzene, benzene, toluene, etc. are capable of dissolving EVA, but it takes a long time for chemical solvents to dissolve EVA, and most of the time they only achieve swelling but not dissolution. First, the time is long, ranging from 3-4 days to more than a week, which is only suitable for laboratories and cannot meet the requirements of industrial production at all; second, a large number of production experiments have confirmed that a single or mixed organic solvent cannot achieve a state of complete dissolution; third, there is no effective response strategy for the environmental issues involved in the large-scale use of organic solvents. Therefore, solvent removal of EVA is far less direct and efficient than high-temperature pyrolysis in industrial-scale production.

[0007] High-temperature heat treatment to remove EVA has two unfavorable hidden dangers for the purity of silicon wafer recovery: EVA residue and carbon contamination on the surface of silicon wafer. Through continuous exploration of these two hidden dangers, the present invention provides a reliable and effective method for removing EVA residue and carbon contamination on the surface of silicon wafer. Summary of the invention

[0008] The purpose of the present invention is to remove EVA residue and carbon deposit pollution generated by high-temperature heat treatment during the recycling process of waste solar photovoltaic panel components.

[0009] A method for treating carbon pollution and EVA on the surface of waste solar photovoltaic silicon wafers during recycling, comprising the following steps: (1) Immerse the waste solar photovoltaic panel components after high-temperature heat treatment in deionized water, perform ultrasonic cleaning at room temperature, and dry; (2) then immersing it in an organic solvent and subjecting it to ultrasonic treatment; (3) The silicon wafer obtained after ultrasonic treatment is washed in deionized water and recycled; The organic solvent in step (2) is composed of polyetheramine or dimethylformamide and butyl p-hydroxybenzoate or ethylene glycol ethyl ether acetate.

[0010] Preferably, the organic solvent is composed of polyetheramine and butylparaben.

[0011] Preferably, the volume ratio of polyetheramine or dimethylformamide to butyl p-hydroxybenzoate or ethylene glycol ethyl ether acetate is: (5.0-6.5): (3.5-5).

[0012] Preferably, the ultrasonic cleaning time in step (1) is 10 to 20 minutes and the power is 600 to 1000W.

[0013] Preferably, the temperature of the ultrasonic treatment in step (2) is 40-60°C, the time is 30-60min, and the power is 400-800W.

[0014] Preferably, the cleaning in step (3) is ultrasonic cleaning.

[0015] Preferably, the ultrasonic cleaning is performed at room temperature, for 10 to 20 minutes, at a power of 600 to 1000W.

[0016] Preferably, the drying temperature in step (1) is 120° C. and the drying time is 30 min.

[0017] Advantages of the present invention: The present invention adopts a synergistic combination of a polar solvent and a permeable organic solvent to efficiently dissolve EVA residues and promote the stripping of surface carbon under the action of ultrasound, thereby effectively ensuring the recovery purity of the silicon wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a 100x microscope image of the silicon wafer surface after high-temperature heat treatment.

[0019] Figure 2 This is a 200x microscope image of the silicon wafer surface after high-temperature heat treatment.

[0020] Figure 3 This is a photo of the silicon wafer after organic solvent treatment of the present invention, a 100x microscope picture.

[0021] Figure 4 This is a photo of the silicon wafer after organic solvent treatment of the present invention, a 200x microscope picture. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with implementation examples, but the protection scope of the present invention is not limited to these embodiments.

[0023] Example 1 A method for treating carbon pollution and EVA on the surface of waste solar photovoltaic silicon wafers during recycling, comprising the following steps: (1) Immerse the waste solar photovoltaic panel components that have been subjected to high-temperature heat treatment in deionized water, ultrasonically clean them for 20 minutes at room temperature and at a power of 600 W, and bake them at 120°C for 30 minutes; (2) then immersed in an organic solvent of polyetheramine and butyl paraben solution in a volume ratio of 5.0:3.5, and ultrasonically treated at 50°C and 400W for 60 minutes; (3) The silicon wafer obtained after ultrasonic treatment was cleaned in deionized water at room temperature and a power of 600 W for 20 min and then recycled.

[0024] The waste solar photovoltaic panel components that have been treated with high temperature heat treatment and those that have been treated with the above process were compared under a microscope with 100 and 200 times magnification. Figure 1 , Figure 3 and Figure 2 , Figure 4 It can be seen from the comparison that after the treatment method of the present invention, it is clearly visible under a 100x and 200x microscope, the surface is clean, and the EVA residue and carbon stains are thoroughly cleaned.

[0025] Example 2 A method for treating carbon pollution and EVA on the surface of waste solar photovoltaic silicon wafers during recycling, comprising the following steps: (1) Immerse the waste solar photovoltaic panel components that have been subjected to high-temperature heat treatment in deionized water, ultrasonically clean them for 10 minutes at room temperature and at a power of 1000 W, and bake them at 120°C for 30 minutes; (2) then immersed in an organic solvent of polyetheramine and ethylene glycol ethyl ether acetate in a volume ratio of 6.0:4.0, and ultrasonically treated at 60°C and 600W for 60 minutes; (3) The silicon wafer obtained after ultrasonic treatment was cleaned in deionized water at room temperature and a power of 1000 W for 10 min and then recycled.

[0026] Example 3 A method for treating carbon pollution and EVA on the surface of waste solar photovoltaic silicon wafers during recycling, comprising the following steps: (1) Immerse the waste solar photovoltaic panel components that have been subjected to high-temperature heat treatment in deionized water, ultrasonically clean them for 15 minutes at room temperature and at a power of 800 W, and bake them at 120°C for 30 minutes; (2) then immersed in an organic solvent of dimethylformamide and butyl paraben in a volume ratio of 6.5:3.5, and ultrasonically treated at 40°C and 800W for 30 min; (3) The silicon wafer obtained after ultrasonic treatment was cleaned in deionized water at room temperature and a power of 800 W for 15 min and then recycled.

[0027] Example 4 A method for treating carbon pollution and EVA on the surface of waste solar photovoltaic silicon wafers during recycling, comprising the following steps: (1) Immerse the waste solar photovoltaic panel components that have been subjected to high-temperature heat treatment in deionized water, ultrasonically clean them for 17 minutes at room temperature and at a power of 700 W, and bake them at 120°C for 30 minutes; (2) then immersed in an organic solvent of dimethylformamide and ethylene glycol ethyl ether acetate in a volume ratio of 5.5:5, and ultrasonically treated at 55°C and 700W for 50min; (3) The silicon wafer obtained after ultrasonic treatment was cleaned in deionized water at room temperature and a power of 650 W for 17 min and then recycled.

Claims

1. A method for treating carbon pollution and EVA on the surface of waste solar photovoltaic silicon wafers during recycling, characterized in that: The following steps are involved: (1) Immerse the waste solar photovoltaic panel components after high-temperature heat treatment in deionized water, perform ultrasonic cleaning at room temperature, and dry; (2) then immersing it in an organic solvent and subjecting it to ultrasonic treatment; (3) The silicon wafer obtained after ultrasonic treatment is washed in deionized water and recycled; The organic solvent in step (2) is composed of polyetheramine or dimethylformamide and butyl p-hydroxybenzoate or ethylene glycol ethyl ether acetate.

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

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

5. The method for treating carbon pollution and EVA on the surface of silicon wafers in recycling waste solar photovoltaic silicon wafers according to claim 1, characterized in that: The temperature of the ultrasonic treatment in step (2) is 40-60°C, the time is 30-60min, and the power is 400-800W.

6. The method for treating carbon pollution and EVA on the surface of silicon wafers in recycling 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 pollution and EVA on the surface of silicon wafers in recycling waste solar photovoltaic silicon wafers according to claim 5, characterized in that: The temperature of the ultrasonic cleaning is room temperature, the time is 10 to 20 minutes, and the power is 600 to 1000W.

8. The method for treating carbon pollution and EVA on the surface of silicon wafers in recycling 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 min.

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