A method for delaminating EVA adhesive film in decommissioned photovoltaic modules

Abstract

The present application relates to a kind of EVA adhesive film delamination separation method in decommissioned photovoltaic module, belong to the field of organic chemical industry and secondary resource efficient recycling field.The decommissioned photovoltaic module is placed in waste organic solvent and is dissolved delamination treatment, photovoltaic module can be delaminated;The waste organic solvent includes gamma-butyrolactone and N-methyl pyrrolidone, wherein, the mass ratio of gamma-butyrolactone is 3~30wt%, and the mass ratio of N-methyl pyrrolidone is 70~97wt%.The method is simple, makes the decommissioned photovoltaic module fast delamination, and can avoid the battery piece broken and dispersed to adhere on the surface of EVA, so as to recycle and reuse, and use low toxicity waste organic solvent, reduce cost, can be recycled, avoid the defects such as pollution environment.

Description

Technical Field

[0001] This invention relates to a method for the layered separation of EVA film in decommissioned photovoltaic modules, belonging to the fields of organic chemical engineering and efficient recycling of secondary resources. Background Technology

[0002] Solar photovoltaic (PV) is one of the few renewable energy sources with great potential to gradually replace fossil fuels to meet the ever-growing global energy demand. The average lifespan of PV modules is 25 years, and as installed capacity increases, the number of retired PV modules will also increase, with over 80% being crystalline silicon PV modules. Crystalline silicon PV modules contain aluminum, copper, silver, silicon, and glass. Recycling these materials can generate economic revenue and replace virgin production materials, reducing energy investment.

[0003] Therefore, separating photovoltaic modules has significant economic value. However, the recycling of retired photovoltaic modules currently suffers from problems such as low processing efficiency, low recycling output, high costs, and adverse environmental impacts, thus preventing the formation of commercial-scale photovoltaic recycling.

[0004] The recycling process of crystalline silicon photovoltaic modules includes: frame disassembly, delamination (removal of EVA), material sorting and recycling, and hydrometallurgy. Delamination is a key research focus, with existing methods including thermal delamination, chemical delamination, and mechanical delamination. Thermal delamination involves high-temperature pyrolysis of the photovoltaic module to achieve delamination. While it can achieve clean separation of solar cells and module glass and recover high-purity materials, it has high energy consumption, low throughput, and emits toxic gases (fluorine-containing gases). Mechanical delamination involves crushing the photovoltaic module and sorting the mixture. This method has low processing costs and high throughput, but it is insufficient in controlling toxic element pollution and generates significant dust and noise. In recent years, chemical delamination has become a research hotspot due to its lower energy consumption and ability to obtain high-purity materials. Developing green, efficient, inexpensive, and readily available solvents to achieve EVA delamination is of great research significance. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of this invention is to provide a method for separating the EVA film in retired photovoltaic modules. This method not only achieves efficient separation of retired photovoltaic modules, but also avoids the breakage and dispersion of the cells attached to the EVA surface, which is more conducive to the subsequent recycling of components and has great economic benefits.

[0006] To achieve the above objectives, a first aspect of the present invention provides a method for separating the layered EVA film in a decommissioned photovoltaic module, the method comprising: The photovoltaic modules can be separated into layers by placing them in waste organic solvents for dissolution and stratification. The waste organic solvent contains γ-butyrolactone and N-methylpyrrolidone, wherein the mass percentage of γ-butyrolactone is 3~30wt% and the mass percentage of N-methylpyrrolidone is 70~97wt%.

[0007] In crystalline silicon photovoltaic modules, the EVA encapsulant film is an organic polymer material with side chains containing ester groups. Its molecular formula is... .

[0008] Traditional organic solvent-based layering treatments of EVA films often result in poor solubility, leading to swelling and ultimately cell breakage and dispersion. The innovation of this invention lies in using a waste organic solvent containing N-methylpyrrolidone and γ-butyrolactone to dissolve the EVA film. On one hand, N-methylpyrrolidone acts as a solvent, dissolving and de-adhesive the EVA film in the photovoltaic module, facilitating the gradual separation of the backsheet and glass from the film. On the other hand, the γ-butyrolactone in the waste organic solvent acts as a promoter, accelerating the chemical decomposition of the EVA film and thus promoting rapid dissolution by N-methylpyrrolidone. This prevents swelling and avoids cell breakage and dispersion, facilitating subsequent recycling. Furthermore, this invention uses a low-cost waste solvent, significantly reducing solvent costs while maintaining effective dissolution. The dissolution process also largely preserves the solvent's composition, ensuring uninterrupted recycling.

[0009] In a preferred embodiment, the mass percentage of γ-butyrolactone in the waste organic solvent is 3-15 wt%, and the mass percentage of N-methylpyrrolidone is 80-95 wt%. When the mass percentages of γ-butyrolactone and N-methylpyrrolidone are within this range, the separation efficiency of the EVA membrane can be higher.

[0010] In a preferred embodiment, the waste organic solvent also contains propylene glycol methyl ether acetate, N-methylbutyramide, and ethylene glycol monobutyl ether.

[0011] In a preferred embodiment, the waste organic solvent contains γ-butyrolactone at a mass ratio of 3-15 wt%, N-methylpyrrolidone at a mass ratio of 80-95 wt%, propylene glycol methyl ether acetate at a mass ratio of 0.5-7 wt%, N-methylsuccinamide at a mass ratio of 0.2-3 wt%, and ethylene glycol monobutyl ether at a mass ratio of 0.8-2 wt%.

[0012] In a preferred embodiment, the mass percentage of γ-butyrolactone in the waste organic solvent is 3-10 wt%.

[0013] In a preferred embodiment, the temperature for the dissolution and delamination treatment is 90~130℃, and the time is 0.5~1.5h. By combining the waste organic solvent and thermal field enhancement process provided in this application with the dissolution and delamination treatment of decommissioned photovoltaic modules, the glass, backsheet, and solar cells can be efficiently separated from the decommissioned photovoltaic modules.

[0014] In a more preferred embodiment, the dissolution and layering treatment is carried out at a temperature of 100-130°C for 0.5-1 hour. Increasing the temperature promotes the dissolution of the photovoltaic module by the solvent, but a faster dissolution rate can be achieved at 100-130°C. Simultaneously, within this temperature range, both high separation efficiency and cell breakage and dispersion are ensured. Furthermore, although the glass separation rate in the EVA film increases with soaking time, it hardly changes after 1 hour of soaking.

[0015] In a preferred embodiment, the liquid-to-solid ratio of the dissolution and stratification process is (5~15) mL:1g.

[0016] In a more preferred embodiment, the liquid-to-solid ratio of the dissolution and stratification process is (5~8) mL:1g. To a certain extent, when the stratification time is the same, the glass separation rate increases with the increase of the liquid-to-solid ratio. However, when the solvent is sufficient to submerge the photovoltaic module, further increases in the liquid-to-solid ratio have no significant impact on the glass separation rate, and an excessively high liquid-to-solid ratio will lead to an increase in waste liquid, which is not conducive to subsequent recycling and recovery. Therefore, a liquid-to-solid ratio of (5~8) mL:1g is preferred.

[0017] In a preferred embodiment, the waste organic solvent comes from waste panel cleaning agent generated during the panel cleaning process in the electronics industry panel production process.

[0018] Compared with the prior art, the present invention has at least the following advantages: (1) This invention is the first to use waste organic solvents containing N-methylpyrrolidone and γ-butyrolactone to treat retired photovoltaic modules, causing the photovoltaic modules to separate into layers. This allows for the efficient separation of glass, backsheet, and cells from the retired photovoltaic modules, realizing the recovery of valuable components from the retired photovoltaic modules and laying the foundation for their further full resource utilization. It is also beneficial to environmental protection. At the same time, this invention uses a thermal field enhancement process, which further improves the separation efficiency of the EVA film by heating the dissolution and layering process.

[0019] (2) The present invention uses N-methylpyrrolidone (NMP) solvent as solvent. Compared with traditional organic solvents such as benzene, toluene and trichloroethylene, it avoids high toxicity and is more conducive to large-scale application. On the other hand, it ensures the layering effect. Furthermore, in the presence of γ-butyrolactone, it promotes the chemical decomposition of EVA film, which is conducive to the rapid dissolution of NMP, avoids swelling, and can obtain complete battery cells.

[0020] (3) In the process of dissolving photovoltaic modules, the present invention uses low-value waste solvents, which reduces costs by using waste solvents to treat waste, and greatly reduces the cost of solvents while ensuring the dissolution effect. At the same time, the dissolution process hardly changes the composition of the solvent itself and does not affect its original recycling process.

[0021] (4) The dissolution and separation method of the present invention uses inexpensive and low-toxic solvents, which solves the problem of high cost and high toxicity of chemical dissolution and has great application prospects. Attached Figure Description

[0022] Figure 1 This is the XRD pattern of the glass before EVA film delamination in retired photovoltaic modules; Figure 2 This is the XRD pattern of the solar cells before the EVA film of the retired photovoltaic module is delaminated; Figure 3 This is a state diagram of the solar cells obtained after the EVA film of the photovoltaic module has been layered. Detailed Implementation

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments. Obviously, the embodiments described below are only a part of the embodiments, and all other embodiments obtained by those skilled in the art without creative effort are still within the scope of protection of the present invention.

[0025] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0026] Test case This invention grinds the glass layer and cell layer of retired photovoltaic modules to a density suitable for passing through a 150-200 mesh sieve, and uses X-ray fluorescence diffraction to analyze the elemental content of the cell layer and glass layer. The main components are shown in Tables 1 and 2. This invention also provides XRD patterns of the glass and cell layers before EVA film delamination in retired photovoltaic modules, respectively. Figure 1 and Figure 2 .

[0027]

[0028]

[0029] As shown in Table 1, the main element of the solar cell is Si, with a content of 94.54%. As shown in Table 2, the main components of the glass are SiO2, Na2O and CaO, with contents of 69.93wt%, 16.15wt% and 8.47wt%, respectively.

[0030] The content of waste organic solvents was tested and analyzed using gas chromatography-mass spectrometry (GCMS). The specific results are shown in Table 3.

[0031]

[0032] Example 1 Waste organic solvents were used to dissolve and separate retired photovoltaic modules (photovoltaic module fragments with a size of 2cm×2cm) at 110℃, and the time required to achieve 100% glass separation rate under different solid-liquid ratios was recorded.

[0033] When the liquid-to-solid ratio is 15 mL: 1 g, the time required for the glass separation rate to reach 100% is 45 min, and the solar cells do not show any signs of breakage or dispersion. When the liquid-to-solid ratio is 10 mL: 1 g, the time required for the glass separation rate to reach 100% is 45 min, and the solar cells do not show any signs of breakage or dispersion. When the liquid-to-solid ratio is 8 mL: 1 g, the time required for the glass separation rate to reach 100% is 45 min, and the solar cells do not show any signs of breakage or dispersion. When the liquid-to-solid ratio is 5 mL: 1 g, the time required for the glass separation rate to reach 100% is 55 min, and the solar cells do not show any signs of breakage or dispersion.

[0034] This invention provides, exemplarily, a state diagram of the solar cell obtained after the EVA film of a photovoltaic module has delaminated when the solid-liquid ratio is 10 mL: 1 g, as shown in the following figure. Figure 3 As can be seen from the figure, after the retired photovoltaic modules were treated with EVA film layering, the resulting battery cells had a complete structure and did not show any breakage or dispersion.

[0035] Example 2 Waste organic solvents were used to dissolve and separate retired photovoltaic modules (photovoltaic module fragments with a size of 2cm×2cm) under a solid-liquid ratio of 8mL:1g. The time taken to achieve 100% glass separation rate at the specified temperature was recorded.

[0036] When the dissolution and stratification treatment temperature is 90℃, the time required to achieve 100% glass separation rate is 90 minutes, and the solar cells do not show any signs of breakage or dispersion. When the dissolution and stratification treatment temperature is 100℃, the time required to achieve 100% glass separation rate is 60 minutes, and the solar cells do not show signs of breakage or dispersion. When the dissolution and stratification treatment temperature is 120℃, the time required to achieve 100% glass separation rate is 40 minutes, and the solar cells do not show any signs of breakage or dispersion. When the dissolution and stratification treatment temperature is 130℃, the time required to achieve 100% glass separation rate is 30 minutes, and the solar cells do not show any signs of breakage or dispersion.

[0037] Example 3 To simulate the effect of waste organic solvents on the separation of EVA film in decommissioned photovoltaic modules, the inventors used N-methylpyrrolidone (NMP) and γ-butyrolactone to prepare organic solvents with NMP mass ratios of 72%, 77%, 82%, 87%, 92%, and 97% (water was added to the prepared solutions to more closely resemble waste organic solvents, mainly because waste organic solvents also contain 0.5~5wt% water). The decommissioned photovoltaic modules were then immersed in the solutions with a liquid-to-solid ratio of 8mL:1g, a temperature of 110℃, and photovoltaic module fragments of 2cm×2cm. The change data for obtaining a glass separation rate of 100% are shown in Table 4.

[0038]

[0039] As can be seen from Table 4, the presence of γ-butyrolactone can effectively prevent swelling and obtain complete battery cells. Furthermore, setting the contents of N-methylpyrrolidone and γ-butyrolactone within the range of this invention can ensure a faster separation rate.

[0040] Comparative Example 1 Prepare organic solvent A, which contains 92.8 wt% N-methylpyrrolidone, 4.6 wt% propylene glycol methyl ether acetate, 1.5 wt% N-methylsuccinamide, and 1.1 wt% ethylene glycol monobutyl ether.

[0041] Organic solvent A was used to dissolve and separate retired photovoltaic modules (photovoltaic module fragments with a size of 2cm×2cm) at 110℃ with a solid-liquid ratio of 8mL:1g. The time required to achieve 100% glass separation rate was 50min, but the solar cells broke.

[0042] Comparative Example 2 Prepare organic solvent B, which contains 65 wt% N-methylpyrrolidone, 4.6 wt% propylene glycol methyl ether acetate, 27.8 wt% γ-butyrolactone, 1.5 wt% N-methylsuccinamide, and 1.1 wt% ethylene glycol monobutyl ether.

[0043] Organic solvent B was used to dissolve and separate retired photovoltaic modules (photovoltaic module fragments with a size of 2cm×2cm) at 110℃ with a solid-liquid ratio of 8mL:1g. The time required to achieve 100% glass separation rate was 100min, and no breakage or dispersion of the solar cells was observed.

[0044] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for separating the layered EVA film in a decommissioned photovoltaic module, characterized in that: The method includes: The photovoltaic modules can be separated into layers by placing them in waste organic solvents for dissolution and stratification. The waste organic solvent contains γ-butyrolactone, N-methylpyrrolidone, propylene glycol methyl ether acetate, N-methylsuccinamide and ethylene glycol monobutyl ether; In the waste organic solvent, γ-butyrolactone accounts for 3-15 wt% by mass, N-methylpyrrolidone accounts for 80-95 wt% by mass, propylene glycol methyl ether acetate accounts for 0.5-7 wt% by mass, N-methylsuccinamide accounts for 0.2-3 wt% by mass, and ethylene glycol monobutyl ether accounts for 0.8-2 wt% by mass. The liquid-to-solid ratio of the dissolution and stratification process is (5~15) mL:1g.

2. The method for separating the EVA film in a decommissioned photovoltaic module according to claim 1, characterized in that: The temperature for the dissolution and layering treatment is 90~130℃, and the time is 0.5~1.5h.

3. The method for separating the EVA film in a decommissioned photovoltaic module according to claim 1, characterized in that: The temperature for the dissolution and layering process is 100~130℃, and the time is 0.5~1h.

4. The method for separating the EVA film in a decommissioned photovoltaic module according to claim 1, characterized in that: The liquid-to-solid ratio of the dissolution and stratification process is (5~8) mL:1g.

Images