Layered separation method of EVA (Ethylene Vinyl Acetate) adhesive film in retired photovoltaic module

Abstract

The invention relates to a layering separation method of an EVA (Ethylene Vinyl Acetate) adhesive film in a retired photovoltaic module, belonging to the field of organic chemical industry and the field of efficient cyclic utilization of secondary resources. The decommissioned photovoltaic module is placed in the waste organic solvent to be subjected to dissolution layering treatment, and then the photovoltaic module can be layered; the waste organic solvent contains gamma-butyrolactone and N-methyl pyrrolidone, the mass ratio of the gamma-butyrolactone is 3-30 wt%, and the mass ratio of the N-methyl pyrrolidone is 70-97 wt%. The method is simple in process, enables the retired photovoltaic module to be quickly layered, can avoid the situation that battery pieces attached to the EVA surface are broken and dispersed so as to be recycled, uses the low-toxicity waste organic solvent, reduces the cost, can be recycled, and avoids the defects of environmental pollution and the like.

Description

Technical Field

[0001] The invention relates to a layered separation method of an EVA film in a retired photovoltaic module, and belongs to the field of organic chemical industry and the field of efficient recycling of secondary resources. Background Art

[0002] Solar photovoltaics is one of the few renewable energy sources with great potential. It will gradually replace fossil fuels to meet the growing global energy demand. The average life of photovoltaic modules is 25 years. As the installed capacity grows, the number of retired photovoltaic modules will also grow, of which more than 80% are crystalline silicon photovoltaic modules. Crystalline silicon photovoltaics contain aluminum, copper, silver, silicon and glass. If these materials are recycled, they can create economic income, replace original production materials, and reduce energy investment.

[0003] Therefore, separating photovoltaic modules has great economic value. However, at present, the recycling of retired photovoltaic modules has problems such as low processing efficiency, low recycling yield, high cost and adverse impact on the environment, so commercial-scale photovoltaic recycling has not yet been formed.

[0004] The recycling process of crystalline silicon photovoltaic modules is: frame disassembly, stratification (removal of EVA), material sorting and recycling, and hydrometallurgy. Among them, the stratification method is the focus of research. There are three existing stratification methods: thermal stratification, chemical stratification, and mechanical stratification. The thermal stratification method is to stratify the photovoltaic modules by high-temperature pyrolysis. Although it can achieve clean separation of solar cells and module glass and recover high-purity materials, it has high energy consumption, low processing capacity, and emits toxic gases (fluorine-containing gases); mechanical stratification is to sort the mixture after crushing the photovoltaic modules. This method has low processing costs and high processing capacity, but it is insufficient in controlling the pollution of toxic elements and will also produce serious dust and noise; in recent years, due to its advantages such as low energy consumption and the ability to obtain high-purity materials, the chemical stratification method has become a research hotspot. The research and development of green, efficient, cheap and easily available solvents to achieve EVA stratification has a high research significance. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a method for stratifying and separating EVA films in retired photovoltaic modules, which not only realizes the efficient stratification of retired photovoltaic modules, but also can avoid the breakage and dispersion of battery cells attached to the surface of EVA, which is more conducive to the subsequent component recovery and has great economic benefits.

[0006] In order to achieve the above object, the first aspect of the present invention is to provide a method for separating the EVA film in a retired photovoltaic module by layers, the method comprising: The retired photovoltaic modules are placed in waste organic solvents for dissolution and stratification treatment, so that the photovoltaic modules can be stratified; The waste organic solvent contains γ-butyrolactone and N-methylpyrrolidone, wherein the mass proportion of γ-butyrolactone is 3-30wt% and the mass proportion of N-methylpyrrolidone is 70-97wt%.

[0007] The EVA film in the crystalline silicon photovoltaic module is an organic polymer material, and the side chain is a group containing an ester group. The molecular formula is .

[0008] When the traditional organic solvent is used to treat the EVA film in layers, the solubility of the organic solvent with the EVA film is poor, and swelling will occur, which will cause the battery cells to break and disperse. The innovation of the present invention is to use waste organic solvents containing N-methylpyrrolidone and γ-butyrolactone to dissolve the EVA film. On the one hand, N-methylpyrrolidone is used as a solvent to dissolve the EVA film in the photovoltaic module and lose its viscosity, which is convenient for the backplane and glass to be gradually separated from the EVA film. On the other hand, the γ-butyrolactone contained in the waste organic solvent is used as a promoter to promote the chemical decomposition of the EVA film, which is conducive to the rapid dissolution of the EVA film by N-methylpyrrolidone, thereby avoiding the swelling effect, avoiding the battery cells attached to the surface of the EVA from breaking and dispersing, and being more conducive to subsequent recycling. Furthermore, the present invention uses waste solvents with lower value, which greatly reduces the use cost of the solvent 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.

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

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

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

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

[0013] In a preferred solution, the temperature of the dissolution and stratification treatment is 90-130°C and the time is 0.5-1.5 hours. The dissolution and stratification treatment of retired photovoltaic modules using the waste organic solvent and thermal field strengthening process provided in this application can efficiently separate the glass, backplane and battery cells from retired photovoltaic modules.

[0014] In a more preferred solution, the temperature of the dissolution and stratification treatment is 100-130°C and the time is 0.5-1h. Increasing the temperature can promote the dissolution of the solvent to the photovoltaic module, but a faster dissolution rate can be achieved at 100-130°C. At the same time, within this temperature range, it can not only ensure high separation efficiency but also avoid the breakage and dispersion of the battery cells. Furthermore, although the separation rate of the glass in the EVA film increases with the increase of the immersion time, the glass separation rate hardly changes after immersion for 1 hour.

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

[0016] In a more preferred solution, the liquid-to-solid ratio of the dissolution and stratification treatment is (5-8) mL: 1 g. To a certain extent, when the stratification treatment 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, the continued increase of the liquid-to-solid ratio has no obvious effect on the glass separation rate. Moreover, too large a liquid-to-solid ratio will lead to an increase in the amount of waste liquid, which is not conducive to subsequent recycling and recovery. Therefore, the preferred liquid-to-solid ratio is (5-8) mL: 1 g.

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

[0018] Compared with the prior art, the present invention has at least the following advantages: (1) The present invention is the first to use waste organic solvents containing N-methylpyrrolidone and γ-butyrolactone to treat retired photovoltaic modules, so that the photovoltaic modules can be layered, so as to efficiently separate the glass, backplane and battery cells from the retired photovoltaic modules, thereby realizing the recovery of valuable components of retired photovoltaic modules, laying the foundation for their further full resource utilization, and being beneficial to environmental protection. At the same time, the present invention adopts a thermal field enhancement process, and 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 a 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 stratification effect. Furthermore, in the presence of γ-butyrolactone, it promotes the chemical decomposition of the EVA film, which is conducive to the rapid dissolution of NMP, avoids the occurrence of swelling, and can obtain a complete battery cell.

[0020] (3) The present invention uses waste solvents of lower value in the process of dissolving photovoltaic modules, uses waste solvents to treat waste, reduces costs, and greatly reduces the cost of using 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 a cheap, low-toxic solvent, which solves the long-standing problem of high cost and high toxicity of chemical dissolution and has great application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the XRD pattern of the glass before delamination of EVA film on retired photovoltaic modules; Figure 2 This is the XRD spectrum of the cell before EVA film delamination of retired photovoltaic modules; Figure 3 This is a state diagram of the battery cell obtained after the EVA film of the photovoltaic module is delaminated. DETAILED DESCRIPTION

[0023] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0024] The present invention is further described below in conjunction with specific embodiments, but the protection scope 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 professionals in this field without creative work still belong to the protection scope of the present invention.

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

[0026] Test Case The present invention grinds the glass layer and the battery layer of the retired photovoltaic module to pass through a 150-200 mesh sieve, and uses X-ray fluorescence diffraction to analyze the element content in the battery layer and the glass layer. The main components are shown in Table 1 and Table 2. At the same time, the present invention provides the XRD spectrum of the glass before the EVA film delamination in the retired photovoltaic module and the XRD spectrum of the battery before the EVA film delamination in the retired photovoltaic module, which are shown in Table 1 and Table 2, respectively. Figure 1 and Figure 2 .

[0027]

[0028]

[0029] It can be seen from Table 1 that the main element of the cell is Si, and its content is 94.54%; it can be seen from Table 2 that the main components of the glass are SiO2, Na2O and CaO, and their contents are 69.93wt%, 16.15wt% and 8.47wt% respectively.

[0030] The content of waste organic solvents was tested and analyzed by 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 stratify retired photovoltaic modules (the size of photovoltaic module fragments was 2cm×2cm) at 110°C, and the time required for the glass separation rate to reach 100% under different solid-liquid ratios was recorded.

[0033] When the liquid-to-solid ratio was 15 mL: 1 g, the time required for the glass separation rate to reach 100% was 45 min, and the cell did not break or disperse; When the liquid-to-solid ratio was 10mL:1g, the time required for the glass separation rate to reach 100% was 45min, and the cell did not break or disperse; When the liquid-to-solid ratio was 8 mL:1 g, the time required for the glass separation rate to reach 100% was 45 min, and the cell did not break or disperse; When the liquid-to-solid ratio was 5mL:1g, the time required for the glass separation rate to reach 100% was 55min, and the battery cells did not break or disperse.

[0034] The present invention provides, by way of example, a state diagram of a cell obtained after delamination of the EVA film of a photovoltaic module when the solid-liquid ratio is 10 mL: 1 g, as shown in FIG. Figure 3 ,It can be seen from the figure that after the retired photovoltaic modules are subjected to EVA film layering treatment, the obtained cell structure is complete without any breakage or dispersion.

[0035] Example 2 Waste organic solvents were used to dissolve and stratify retired photovoltaic modules (the size of photovoltaic module fragments was 2cm×2cm) at a solid-liquid ratio of 8mL:1g, and the time required for the glass separation rate to reach 100% at the recorded temperature.

[0036] When the dissolution and delamination treatment temperature is 90°C, the time required for the glass separation rate to reach 100% is 90 minutes, and the battery cells do not break or disperse; When the dissolution and delamination treatment temperature is 100°C, the time required for the glass separation rate to reach 100% is 60 minutes, and the battery cells do not break or disperse; When the dissolution and delamination treatment temperature is 120°C, the time required for the glass separation rate to reach 100% is 40 minutes, and the battery cells do not break or disperse; When the dissolution and delamination treatment temperature is 130°C, the time required for the glass separation rate to reach 100% is 30 minutes, and the battery cells do not show breakage or dispersion.

[0037] Example 3 In order to simulate the delamination and separation effect of waste organic solvents on EVA films in retired photovoltaic modules, the inventors used N-methylpyrrolidone (NMP) and γ-butyrolactone to prepare organic solvents with mass proportions of N-methylpyrrolidone (NMP) of 72%, 77%, 82%, 87%, 92%, and 97%, respectively (in order to be closer to the waste organic solvent, water was added to the prepared solution, mainly because the waste organic solvent also contains 0.5~5wt% of water). The retired photovoltaic modules were immersed in the liquid-to-solid ratio of 8mL:1g, the temperature was 110℃, the size of the photovoltaic module fragments was 2cm×2cm, and the change data of the time required for the glass separation rate to reach 100% are shown in Table 4.

[0038]

[0039] It can be seen from Table 4 that in the presence of γ-butyrolactone, swelling can be effectively avoided to obtain a complete battery cell, and setting the contents of N-methylpyrrolidone and γ-butyrolactone within the range of the present invention can ensure a faster separation rate.

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

[0041] Organic solvent A was used to dissolve and stratify retired photovoltaic modules (the size of photovoltaic module fragments was 2cm×2cm) at 110°C, with a solid-liquid ratio of 8mL:1g. The time required for the glass separation rate to reach 100% was 50min, but the battery cells were broken.

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

[0043] The retired photovoltaic modules (the size of photovoltaic module fragments is 2cm×2cm) were dissolved and stratified at 110°C using organic solvent B, with a solid-liquid ratio of 8mL:1g. The time required for the glass separation rate to reach 100% was 100min, and the battery cells did not show any breakage or dispersion.

[0044] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for separating the EVA film from retired photovoltaic modules, characterized in that: The method includes: The retired photovoltaic modules are placed in waste organic solvents for dissolution and stratification treatment, so that the photovoltaic modules can be stratified; The waste organic solvent contains γ-butyrolactone and N-methylpyrrolidone, wherein the mass proportion of γ-butyrolactone is 3-30wt% and the mass proportion of N-methylpyrrolidone is 70-97wt%.

2. The method for separating the EVA film from the retired photovoltaic module according to claim 1, characterized in that: In the waste organic solvent, the mass proportion of γ-butyrolactone is 3-15wt%, and the mass proportion of N-methylpyrrolidone is 80-95wt%.

3. The method for separating the EVA film from retired photovoltaic modules according to claim 1, characterized in that: The waste organic solvent also contains propylene glycol methyl ether acetate, N-methylsuccinamide and ethylene glycol monobutyl ether.

4. The method for separating the EVA film from the retired photovoltaic module according to claim 3, characterized in that: In the waste organic solvent, the mass proportion of γ-butyrolactone is 3-15wt%, the mass proportion of N-methylpyrrolidone is 80-95wt%, the mass proportion of propylene glycol methyl ether acetate is 0.5-7wt%, the mass proportion of N-methylsuccinamide is 0.2-3wt%, and the mass proportion of ethylene glycol monobutyl ether is 0.8-2wt%.

5. The method for separating the EVA film from the retired photovoltaic modules according to any one of claims 1 to 4, characterized in that: The temperature of the dissolution and stratification treatment is 90-130° C. and the time is 0.5-1.5 h.

6. The method for separating the EVA film from the retired photovoltaic module according to claim 5, characterized in that: The temperature of the dissolution and stratification treatment is 100-130° C., and the time is 0.5-1 h.

7. A method for separating the EVA film from retired photovoltaic modules according to any one of claims 1 to 4, characterized in that: The liquid-to-solid ratio of the dissolution and stratification treatment is (5-15) mL: 1 g.

8. The method for separating the EVA film from the retired photovoltaic module according to claim 7, characterized in that: The liquid-to-solid ratio of the dissolution and stratification treatment is (5-8) mL:1 g.

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