Method for dissociating and recycling retired photovoltaic module by combining green solvent and pyrolysis

Abstract

The invention provides application of an ethyl lactate solution in separation and recovery of a decommissioned photovoltaic module and a dissociation and recovery method of the decommissioned photovoltaic module, and belongs to the technical field of photovoltaic module recovery. The invention provides a green solvent and pyrolysis combined dissociation and recovery method for an out-of-service photovoltaic module. An aluminum outer frame, a junction box and glass of the out-of-service photovoltaic module are dismantled through a dismantling process; performing layered dissociation on the residual photovoltaic laminated structure by adopting an ethyl lactate solution, separating the back plate and removing an aged and damaged fluorine film on the outermost layer of the back plate on the premise of not damaging a core structure to obtain a semi-finished product of the back plate; and the battery piece and the EVA adhesive layer adhered to the battery piece are subjected to heat treatment in the presence of calcium oxide, so that the separation of the battery piece and the EVA adhesive layer and the enrichment of the calcium-containing mixed material are realized, and the pure battery piece is obtained. The recycling efficiency of the photovoltaic module is remarkably improved, the energy consumption is reduced, the environmental pollution is reduced, and a new thought is provided for resource recycling of the photovoltaic module.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of recycling of photovoltaic modules, in particular to a method for disintegration and recycling of decommissioned photovoltaic modules by using green solvent and pyrolysis. BACKGROUND

[0002] Current photovoltaic module recycling mainly adopts three technical routes of physical method, chemical method and thermal treatment method, each with its own characteristics: the physical method has simple process, low equipment cost and no significant chemical pollution risk, but it is easy to cause the battery piece and glass to be broken, the purity of the recycled material is low, and it may cause dust pollution; the chemical method can realize complete separation of materials and high-purity recycling, and has high-value utilization potential, but it faces problems such as high solvent cost, large waste liquid treatment cost, long cycle, and chemical pollution and safety hazards; the thermal treatment method has good separation effect, is suitable for large-scale treatment and has high purity of recycled materials, but it has disadvantages such as high energy consumption, release of toxic gases such as HF / CO, need for a tail gas treatment system and complex process. In addition, the imbalance between recycling cost and economic value restricts the large-scale development of technology, especially the EVA adhesive layer and the back plate (such as TPT back plate) are difficult to recycle and utilize efficiently, which has become a key problem that needs to be broken through in the current technology and industry. SUMMARY

[0003] Therefore, in order to solve the technical problems of long cycle of the chemical method used in the current decommissioned photovoltaic module, high energy consumption of the thermal treatment method, easy secondary pollution and low recycling yield, the present application provides the application of ethyl lactate solution in separating and recycling decommissioned photovoltaic modules and a method for disintegration and recycling of decommissioned photovoltaic modules by using green solvent and pyrolysis. Ethyl lactate is used to separate and recycle the semi-finished back plate in the decommissioned photovoltaic module efficiently, environmentally and with low energy consumption. The use of calcium oxide can efficiently remove the EVA adhesive layer and recycle the battery piece at a lower temperature, significantly reducing the energy consumption and carbon dioxide emissions in the recycling process, and having good environmental protection. Not only can the recycling efficiency and product added value be improved, but also the environmental pollution risk can be effectively reduced.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical solutions: In a first aspect, the present application provides the application of ethyl lactate solution in separating and recycling decommissioned photovoltaic modules.

[0005] Preferably, the use concentration of the ethyl lactate solution is 8.3-8.6 mol / L, the temperature is 75-100℃, the treatment time is 30-60 min and the solid-liquid ratio is greater than or equal to 1:10.

[0006] Preferably, the use concentration of the ethyl lactate solution is 8.5 mol / L, the temperature is 100℃, the treatment time is 30 min and the solid-liquid ratio is 1:10.

[0007] In a second aspect, the application provides a method for decomposing and recycling a decommissioned photovoltaic module by combining a green solvent with pyrolysis, comprising the following steps: Step (1), removing the aluminum outer frame, junction box and glass of the decommissioned photovoltaic module through a disassembly process; Step (2), using an ethyl lactate solution to separate the remaining photovoltaic laminated structure layer by layer, separating out the back plate and removing the outermost aging damaged fluorine film of the back plate without damaging the core structure, to obtain a semi-finished back plate; Step (3), the cell piece and the EVA adhesive layer adhered to the cell piece are subjected to heat treatment in the presence of calcium oxide, to realize the separation of the cell piece and the EVA adhesive layer and the enrichment of the calcium-containing mixture (CaO and CaCO3), and to obtain a pure cell piece.

[0008] Preferably, the use concentration of the ethyl lactate solution is 8.3-8.6 mol / L, the temperature is 75-100℃, the treatment time is 30-60 min, and the solid-liquid ratio is greater than or equal to 1:10.

[0009] Preferably, the use concentration of the ethyl lactate solution is 8.5 mol / L, the temperature is 100℃, the treatment time is 30 min, and the solid-liquid ratio is 1:10.

[0010] Preferably, in step (3), the heat treatment conditions are as follows: the heat treatment temperature is 400℃, and the heat treatment time is 20-30 min.

[0011] Preferably, the heat treatment time is 20 min.

[0012] Preferably, it further comprises step (4), recycling: the ethyl lactate solution and the calcium oxide can be recycled and reused.

[0013] Preferably, after the extracted part of the solid pyrolysis residue is subjected to a reduction treatment, it becomes a product mainly containing CaO, which is then put into the pyrolysis cycle again to improve the overall resource utilization efficiency.

[0014] Compared with the prior art, the application has the following beneficial effects: (1) The semi-finished back plate can be completely recycled: by using the green solvent ethyl lactate solution, the application can efficiently separate and recycle the semi-finished back plate (such as a TPT back plate) in the decommissioned photovoltaic module, while the traditional pure pyrolysis method or pure chemical method can only partially recycle and easily damage the structure of the back plate, reducing the recycling efficiency.

[0015] (2) Improve the economic value of recycling: the ethyl lactate solution has a selective treatment and removal effect on the TPT backboard. The outermost layer of the backboard (the side exposed to the environment) has been completely removed, while the inner layer of the fluorine film (the side in contact with the EVA adhesive layer) is intact. The obtained semi-finished backboard is a PVF-PET composite structure, which can be used as a complete finished product after one-time film spraying or coating, and has high economic value.

[0016] (3) Low energy consumption and environmental protection: after treatment with ethyl lactate, only the EVA adhesive layer is left to bond the battery piece together, but according to the principle of "like dissolves like", ethyl lactate can swell EVA and reduce its adhesion to the battery piece, so that the EVA adhesive layer can be completely removed at a lower heat treatment temperature in the subsequent pyrolysis process. Compared with the traditional pure pyrolysis method, the present application uses ethyl lactate solution combined with calcium oxide (CaO) as an alkaline catalytic adsorbent for pyrolysis treatment. The calcium oxide (CaO) can efficiently remove the EVA adhesive layer at a lower temperature (400℃), and recover the battery pieces and other metal materials in the photovoltaic module, significantly reducing the energy consumption and carbon dioxide emissions during the recycling process, and having good environmental protection.

[0017] (4) Recyclable green solvent and catalytic adsorbent: ethyl lactate solution as a green solvent can be recycled after precipitation and filtration. It can maintain good solubility after being used for several times (not less than four times), and the upper layer of the solvent can be used after standing for several hours, avoiding the environmental pollution problem of using harmful solvents in traditional chemical methods. The recycling and reuse of the solvent reduces waste and cost. Calcium oxide can also be recycled. Specifically, part of the solid pyrolysis residue (calcium-containing mixture) can be reduced by calcination to produce a product mainly containing CaO, which can be used again in the pyrolysis cycle to improve the overall resource utilization efficiency.

[0018] (5) Reduce the emission of waste gas and waste water: compared with the traditional pure pyrolysis method, the combination of low-temperature pyrolysis and green solvent treatment in the present application effectively reduces the emission of waste gas and the generation of waste water. In the pyrolysis process, since the backboard has been completely removed in the ethyl lactate step, and under the condition of alkaline catalytic adsorbent calcium oxide, there will be no fluorine-containing organic gas, and the emission of CO2 will be greatly reduced, which meets the requirements of green recycling and sustainable development.

[0019] Through the above improvements, the present application provides a more efficient, environmentally friendly and economic photovoltaic module recycling technology, which promotes the technical progress in the field of photovoltaic recycling. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1The flow diagram of the recycling process using ethyl lactate solution as a green solvent combined with pyrolysis.

[0021] Figure 2 The influence of different experimental factors on the separation rate, wherein a) the influence of solvent type on the separation rate at 75℃ for 60min; b) the influence of molar concentration on the separation rate at 100℃; c) the influence of treatment temperature on the separation rate at 98% EL for 60min; d) the influence of treatment time on the separation rate; Figure 3 The treatment performance of ethyl lactate (EL), wherein (a) samples of different areas; (b) samples reused 4 times; Figure 4 The FTIR and TG characteristic diagrams of EVA before and after ethyl lactate (EL) treatment, (a) FTIR and (b) TG; Figure 5 The FTIR and TG characteristic diagrams of TPT backplane before and after ethyl lactate (EL) treatment, (a) FTIR and (b) TG; Figure 6 The results of heat treatment under different temperature conditions, (a) without additives; (b) with CaO powder; Figure 7 The morphology characteristics and element enrichment distribution of the battery piece after heat treatment: (a) and (c) the back of the battery piece without adding CaO; (b) and (d) the back of the battery piece with CaO; (e) the front of the battery piece without adding CaO; (f) the front of the battery piece with CaO; Figure 8 The XRD characteristics of CaO before and after heat treatment. DETAILED DESCRIPTION

[0022] The technical solutions of the present application will be described in detail below in combination with specific embodiments.

[0023] Example 1 As shown in Figure 1 , first, the aluminum outer frame, junction box and glass of the retired photovoltaic module are removed by mechanical means through an automatic machine tool to obtain a retired photovoltaic module containing glass (residual), EVA, silicon-based battery piece and backplane. Then Figure 2 The influence of different experimental factors, such as solvent type, concentration, treatment temperature and treatment time, on the separation rate is shown. As Figure 2 shown in (a) of the figure, ethyl lactate is exemplarily shown to have a better separation effect than other solvents, such as γ-valerolactone, under the same treatment conditions of 75℃ for 60min, which can completely remove the residual glass and backplane. Figure 2(b) - (d) shown in the middle, (b) respectively tested 4 mol / L and 8.5 mol / L (i.e. mass fraction of 98%). The results show that the best conditions for ethyl lactate (EL) treatment are: concentration of 8.5 mol / L, treatment temperature of 100℃, time of 30 minutes, and solid-liquid ratio of 1:10. After treatment, efficient separation of glass, battery pieces and TPT backplane is successfully achieved.

[0024] In addition, Figure 3 (a) shown in the middle, under the same optimal conditions, complete separation of the backplane can be achieved regardless of the size of the component sample. Figure 3 The results shown in (b) indicate that, under the condition of keeping the volume of ethyl lactate (EL) fixed, the solvent can be continuously used for the delamination treatment of four batches of retired photovoltaic modules, and the separation effect is stable, with a backplane separation rate of 100%. The treated ethyl lactate (EL) is milky white (the original reagent is colorless and transparent), and PVF particles or other solid suspensions can be effectively removed through simple precipitation and filtration operations, restoring its basic physical properties and separation ability, and it can still be used for subsequent treatment processes. The above results show that ethyl lactate (EL) has excellent delamination efficiency and recyclable performance.

[0025] Through Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TG) tests, the efficient separation effect of ethyl lactate solvent on EVA adhesive layer and backplane at high temperature is verified. Figure 4 The FTIR spectral analysis shown in (a) indicates that the EVA before and after treatment with ethyl lactate (EL) is basically consistent in the main characteristic absorption peak position and intensity, and no new functional group is introduced or significant change in the original structure is observed. Figure 4 The thermogravimetric analysis results shown in (b) indicate that the EVA before and after treatment with ethyl lactate (EL) is basically consistent in thermal decomposition behavior, and the difference between the two in terms of initial decomposition temperature, weight loss rate and carbon residue rate is not obvious. The main decomposition stage is concentrated between 280-500℃, which indicates that the thermal stability of EVA is not decreased or the composition is not changed during the treatment with ethyl lactate (EL). The above results further show that ethyl lactate (EL) does not destroy the EVA structure or introduce new pyrolysis reaction paths in the delamination process, and its mechanism is mainly physical penetration and interface peeling, which is suitable for green treatment of different types of EVA adhesive layer, and verifies that EL has good preservation of EVA structure while achieving delamination.

[0026] As Figure 5The FTIR and TG profiles of the TPT backplane shown in (a) and (b) show that the characteristic peaks of the PVF layer on the outside of the TPT backplane after ethyl lactate (EL) treatment disappear, exposing the typical absorption peaks of the underlying PET, indicating that the aged PVF is selectively dissolved. In contrast, the inside PVF is not affected and remains structurally stable, presumably because it is more dense and difficult for ethyl lactate (EL) to penetrate. The limited identification of PVF signals in the spectrum may be due to the thinness of the film layer and the overlap with the PET peaks. Thermogravimetric analysis shows that the pyrolysis behavior of the TPT before and after ethyl lactate (EL) treatment is similar, but the residual carbon after treatment is reduced, further verifying that the outer PVF has been effectively removed, and EL exhibits good layering selectivity.

[0027] Then, the remaining photovoltaic module (including the cell and the EVA adhesive layer adhered to the cell) is placed in a horizontal pyrolysis furnace and a certain amount of CaO powder is added, and heat treatment is carried out in the presence of the basic catalytic adsorbent CaO, the treatment conditions are 400°C and the treatment time is 30 minutes, to achieve efficient separation of the cell-EVA adhesive layer and enrichment of the calcium-containing mixture (CaO and CaCO3), and obtain pure cells.

[0028] Example 2 The photovoltaic module (only the cell and the EVA adhesive layer) treated by the automatic equipment and ethyl lactate (EL) is placed in a tube furnace for pyrolysis. During the pyrolysis process, calcium oxide (CaO) catalyst is added, and the experimental conditions are: pyrolysis temperature 400°C, treatment time 20 minutes. The experimental results can prove that the CaO catalyst can effectively remove the EVA adhesive layer, and the surface of the silicon wafer is smooth and almost no residue. Specifically, Figure 6 The results shown in (a) and (b) show that without catalysis, heating to 500°C is required to basically remove the adhesive, but with a large amount of carbonized residue, affecting the quality of the recovered material (such as Figure 6 (a) shown). After the introduction of CaO (mass ratio 2:1), the heat treatment temperature can be reduced to 400°C to achieve complete removal of the adhesive layer, and there is no obvious coke adhesion (such as Figure 6 (b) shown). CaO reduces the EVA cracking temperature by promoting the β-elimination reaction, and at the same time adsorbs acidic gases to inhibit coke formation, improving the cleaning and separation effect. Although there is slight clumping, there is no chemical combination with the cell, and it is easy to peel off, verifying the feasibility of CaO-assisted heat treatment in low-temperature and efficient removal of the adhesive layer.

[0029] Through scanning electron microscope (SEM) analysis, it is verified that there is no obvious carbonized residue on the surface of the cell after pyrolysis, and the purity of the recovered silicon wafer is high. Specifically, SEM-EDS analysis is performed on the CaO and non-CaO samples treated at 400°C for 20 minutes (such as Figure 7(a)-(f)). The results showed that the surfaces of the cells with CaO were smooth and without obvious residue on both sides; while the group without CaO showed a large number of micron-sized protrusions and gel-like residues, presumably incompletely decomposed EVA. EDS analysis further confirmed that the group without CaO had higher C and O contents, indicating significant organic residues, while the group with CaO showed decreased C and O and increased Si, indicating improved surface cleanliness and sufficient exposure of the silicon substrate. No Ca was detected, indicating that CaO did not introduce calcium contamination. In high-magnification images, the crystal structure of the SiO2 antireflective film was visible on the surface of the CaO-added sample, further demonstrating that organic residues interfered with the observation of the microstructure.

[0030] In summary, CaO can significantly improve EVA removal efficiency, enhance surface cleanliness, and does not introduce impurities for contamination.

[0031] XRD analysis results (such as) Figure 8 The results showed that CaO exhibited typical cubic crystal characteristic peaks before heat treatment, indicating its high purity. After co-heat treatment with the EVA adhesive layer, although CaO characteristic peaks still dominated, a CaCO3 diffraction peak appeared at 2θ≈29.4°, indicating that some CaO reacted with pyrolysis products to form CaCO3. After a second calcination treatment, the CaCO3 peak completely disappeared, while the CaO peak recovered, indicating that CaO can be regenerated at high temperatures. These results reveal the phase transition path and recyclability of CaO during heat treatment, verifying its potential for repeated use as a desorbent.

[0032] In summary, this invention achieves efficient recycling of decommissioned photovoltaic modules through a combined use of green solvents and pyrolysis technology. Specifically: First, components such as the aluminum frame, junction box, and glass are automatically disassembled and separated. Then, ethyl lactate is used to decompose the laminated structure into layers, selectively removing the aged and damaged fluorine film on the outermost layer of the backsheet while retaining the inner fluorine film to obtain a higher-value semi-finished backsheet. Further, the remaining components are heat-treated under alkaline catalyst calcium oxide-assisted catalytic pyrolysis conditions. CaO is used to promote the decomposition of the EVA adhesive layer, reducing the pyrolysis temperature to 400°C to significantly reduce energy consumption. This achieves efficient separation of the battery cells and the EVA adhesive layer, as well as enrichment of calcium-containing mixtures. At the same time, the ethyl lactate solvent and calcium oxide catalyst can be recycled, making the overall process both environmentally friendly and economical.

[0033] The above description is merely a preferred embodiment of the present invention. However, the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention should be covered within the scope of protection of the present invention.

Claims

1. Use of ethyl lactate solution in separating and recycling retired photovoltaic modules.

2. Use according to claim 1, characterized in that, The use concentration of the ethyl lactate solution is 8.3-8.6 mol / L, the temperature is 75-100℃, the treatment time is 30-60 min, and the solid-liquid ratio is greater than or equal to 1:

10.

3. Use according to claim 2, characterized in that, The use concentration of the ethyl lactate solution is 8.5 mol / L, the temperature is 100℃, the treatment time is 30 min, and the solid-liquid ratio is 1:

10.

4. A method for decommissioned photovoltaic module disassembly and recycling by using green solvent in combination with pyrolysis, characterized in that, The method comprises the following steps: Step (1), disassembling the aluminum outer frame, junction box and glass of the retired photovoltaic module through a disassembling process; Step (2), separating the remaining photovoltaic laminated structure by using the ethyl lactate solution, and separating the back plate and removing the outermost aging damaged fluorine film of the back plate without damaging the core structure to obtain a semi-finished back plate; Step (3), the cell piece and the EVA adhesive layer adhered to the cell piece are subjected to heat treatment in the presence of calcium oxide to realize the separation of the cell piece and the EVA adhesive layer and the enrichment of the calcium-containing mixture, and obtain a pure cell piece.

5. The method of claim 4, wherein the green solvent is used in combination with pyrolysis. The use concentration of the ethyl lactate solution is 8.3-8.6 mol / L, the temperature is 75-100℃, the treatment time is 30-60 min, and the solid-liquid ratio is greater than or equal to 1:

10.

6. The method of claim 5, wherein the green solvent is used in combination with pyrolysis. The use concentration of the ethyl lactate solution is 8.5 mol / L, the temperature is 100℃, the treatment time is 30 min, and the solid-liquid ratio is 1:

10.

7. The method of claim 4, wherein the green solvent is used in combination with pyrolysis to decompose and recover the decomposed components of the decomposed PV module. In step (3), the heat treatment conditions are as follows: the heat treatment temperature is 400℃, and the heat treatment time is 20-30 min.

8. The method of claim 7, wherein the green solvent is used in combination with pyrolysis. The heat treatment time is 20 min.

9. The method of claim 4, wherein the green solvent is used in combination with pyrolysis for decommissioned photovoltaic module disassembly and recycling. Further comprising step (4), recycling: the ethyl lactate solution and the calcium oxide can be recycled and reused.

10. A method for decommissioning and recycling of photovoltaic modules using a green solvent in combination with pyrolysis according to any one of claims 4-9, characterized in that, After the extracted part of the solid pyrolysis residue is subjected to reduction treatment, it becomes a product mainly containing CaO, which is then put into the pyrolysis cycle again to improve the overall resource utilization efficiency.

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