A new method for separating and recycling retired photovoltaic modules

Abstract

The present invention belongs to the field of harmless disposal and resource recovery of retired photovoltaic modules, and relates to a new method for separating and recycling photovoltaic modules. The present invention provides a method for separating and recycling retired photovoltaic modules, the method comprising: first, removing the additional structure and completely peeling off the backplane and glass layer in sequence through a heat treatment method to obtain a crystalline silicon cell layer with sealing material adhered to both the upper and lower surfaces; then, subjecting the obtained crystalline silicon cell layer with sealing material adhered to both the upper and lower surfaces to a cryogenic treatment at -190 to -20°C to split the crystalline silicon cell layer. Since the metal in the crystalline silicon cell layer undergoes severe contraction at low temperatures, the split surface is enriched with metal, thereby facilitating the subsequent purification and recovery of the metal. The method of the present invention avoids the problems of difficult separation and purification caused by crushing and mixing, can effectively shorten the solvent recovery time, and improve the purity of metal separation.

Description

Technical Field

[0001] The present invention relates to the field of harmless disposal and resource recovery of retired photovoltaic modules, and in particular to a new process for separating and recycling photovoltaic modules using heat treatment and deep cooling as dual auxiliary methods. Background Art

[0002] Photovoltaic power generation is a new energy technology that converts solar energy into electrical energy. The basic structure of a photovoltaic module includes a crystalline silicon cell layer, an organic packaging layer, a cover glass, a back panel, an outer frame and a junction box. Among them, the cover glass, the back panel and the solar cell are all bonded together through an organic packaging layer.

[0003] The International Renewable Energy Agency predicts that by 2050, the global volume of scrapped photovoltaic panels will reach a staggering 78 million tons, with China accounting for over 20 million tons. Traditional waste disposal methods such as incineration and landfilling not only result in significant resource waste but also cause serious environmental pollution. Therefore, recycling retired photovoltaic panels can effectively alleviate ecological pressures and achieve resource recycling.

[0004] Existing strategies for disassembling and recycling photovoltaic modules often utilize pyrolysis (which can cause environmental pollution), crushing, cryogenic grinding, and cryogenic physics techniques to produce mixed particle (silicon particles, backplane polymer particles, EVA particles, etc.) battery powder. However, mixed particle battery powder is difficult to extract directly and often requires subsequent screening processes (such as vibration and electrostatic screening), which affects the purity of the recycled material.

[0005] In response to the above problems, there is an urgent need for a method with stable process and simple equipment operation to separate various materials (silicon, aluminum, silver, polymer, glass, etc.) of photovoltaic modules to achieve value-added utilization. Summary of the Invention

[0006] In response to the above-mentioned defects, the present invention provides a new method for separating and recycling retired photovoltaic module materials. Through a series of heat treatment methods, after removing the junction box, aluminum frame, and completely peeling off the polymer backplane and glass, crystalline silicon cell wafers with EVA film on both sides (EVA / Si / EVA three-layer structure) are obtained; then the EVA / Si / EVA layered structure cell wafer is cryogenically treated by a cryogenic method (such as liquid nitrogen immersion), so that the metal silicon (Si) cell layer (containing a variety of metals, mainly silicon) is effectively split, so that the metal (silicon, aluminum, silver, indium, gallium and other metals) can be completely exposed to facilitate subsequent solvent purification and recovery (increase the contact area), avoid the problems of difficult separation and purification caused by crushing and mixing, can effectively shorten the solvent recovery time, and improve the metal separation purity.

[0007] The technical solution of the present invention:

[0008] The first technical problem to be solved by the present invention is to provide a method for separating and recycling retired photovoltaic modules, wherein the retired photovoltaic modules include an additional structure and a laminate, wherein the additional structure includes a junction box and a frame, and the laminate includes a glass layer, a first sealing material layer, a crystalline silicon cell layer, a second sealing material layer, and a backsheet;

[0009] The separation and recovery method includes: first, removing the additional structure in sequence and completely peeling off the back plate and the glass layer through a heat treatment method to obtain a crystalline silicon cell layer with sealing materials adhered to the upper and lower surfaces; then subjecting the obtained crystalline silicon cell layer with sealing materials adhered to the upper and lower surfaces to a deep cold treatment at -190 to -20°C to split the crystalline silicon cell layer. Since the metal in the crystalline silicon cell layer shrinks severely at low temperatures, the split surface is enriched with metal (the metal is mainly silicon, and also includes aluminum, silver, indium or gallium, etc.), thereby facilitating the subsequent purification and recovery of the metal.

[0010] Furthermore, the separation and recovery method comprises the following steps:

[0011] 1) removing the additional structure of the retired photovoltaic module through heat treatment to obtain a complete laminate;

[0012] 2) The obtained laminate is subjected to heat treatment to soften the backsheet, and the softened backsheet is completely peeled off using a tool to obtain a recycled polymer backsheet material;

[0013] 3) The remaining components containing the glass layer and the crystalline silicon cell layer continue to be heat treated to peel the crystalline silicon cell layer from the glass surface to obtain a complete glass material and a crystalline silicon cell layer with sealing material adhered to the upper and lower surfaces;

[0014] 4) The crystalline silicon cell layer with sealing material adhered to the upper and lower surfaces is cut into regular cell pieces, and then the regularly shaped cell pieces are cryogenically treated at -190 to -20°C. After the cryogenic treatment, the crystalline silicon cell pieces are split apart. Since the metal in the crystalline silicon cell piece shrinks severely at low temperatures, the metal in the crystalline silicon cell piece is completely exposed.

[0015] 5) Recover metal materials by solvent dissolution recovery method.

[0016] Furthermore, in step 4), the cryogenic treatment is performed by the following methods: liquid nitrogen quenching, liquid helium quenching, dry ice acetone quenching, or dry ice acetonitrile quenching.

[0017] Furthermore, in step 5), the metal is aluminum, silicon, silver, indium or gallium.

[0018] Furthermore, in step 5), the solvent in the solvent dissolution recovery method includes: NaOH, HF, HNO3, H2SO4, H3PO4, H2SiF6, KOH, NH3 or Br2 solvents.

[0019] Furthermore, in step 1) to step 3), the heat treatment temperature is 100 to 250° C., and the heat treatment time is 0.1 to 2 hours.

[0020] Furthermore, the above recycling method also includes: step 2) the obtained polymer backplane material is graded and used directly, or reused with high added value.

[0021] Furthermore, the above recycling method further comprises: step 3) the obtained glass material is subjected to classification treatment and used directly, or recycled and reused.

[0022] The second technical problem to be solved by the present invention is to provide a method for improving the purity of recovered metals obtained in the recycling of retired photovoltaic modules. The method is as follows: first, the additional structure is removed in sequence by a heat treatment method, and the back panel and glass layer are completely peeled off to obtain a crystalline silicon cell layer with sealing materials adhered to the upper and lower surfaces; then the obtained crystalline silicon cell layer is subjected to a deep-freezing treatment at -190 to -20°C to split the metal silicon cell layer, so that the metal can be completely exposed. Due to the increased contact area, the purity of the recovered metal is improved through subsequent solvent purification and recovery methods.

[0023] Beneficial effects of the present invention:

[0024] The present invention adopts heat treatment to assist disassembly to obtain battery laminates adhered with sealing layer materials (such as EVA films), and effectively separates the battery cells through cutting and direct cryogenic treatment (such as liquid nitrogen treatment); by utilizing the severe shrinkage of metals at low temperatures, the metal materials (silicon, aluminum, silver, indium, gallium and other metals) can be completely exposed, thereby facilitating subsequent solvent purification and recovery (increasing the contact area), avoiding the problems of difficult separation and purification caused by crushing and mixing, and can effectively shorten the solvent recovery time and improve the purity of metal separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 1 is a process flow chart of an embodiment of the present invention.

[0026] Figure 2 This is a scanning electron photograph of the cross-section of the cell with the silicon layer effectively separated after deep cryogenic treatment in step 5) of Example 1 of the present invention (the two samples obtained after quenching are respectively recorded as the upper sample and the lower sample) ( Figure 2 a and Figure 2 d) and energy spectrum analysis results ( Figure 2 b, c-upper layer samples, Figure 2 e, f - lower layer samples).

[0027] Figure 3 This is a scanning electron photo of the surface of the upper layer sample where the silicon layer effectively separates the cell in Example 1 of the present invention ( Figure 3a) and energy spectrum analysis results ( Figure 3 bf). DETAILED DESCRIPTION

[0028] The present invention effectively removes the junction box and aluminum frame in the retired photovoltaic module through a series of heat treatment methods, and then completely peels off the back plate and glass material; finally, the EVA / Si / EVA layered structure battery cell is directly cryogenically treated (such as liquid nitrogen treatment) to effectively separate the battery cell from the silicon layer; using the split battery cell, the metal material (silicon, aluminum, silver, indium, gallium and other metals) can be completely exposed to facilitate subsequent solvent purification and recovery (increase the contact area), avoid the problems of difficult separation and purification caused by crushing and mixing, can effectively shorten the solvent recovery time, and improve the purity of metal separation.

[0029] The following further describes specific embodiments of the present invention in conjunction with the embodiments, but the present invention is not limited to the described scope of implementation.

[0030] Example 1

[0031] A method for high-efficiency recycling of retired photovoltaic modules using heat treatment and cryogenic dual-assisted separation, comprising the following steps:

[0032] 1) Place the complete photovoltaic module on a heating platform at 100°C for 1 hour, remove the aluminum frame and junction box, and obtain a complete photovoltaic laminate;

[0033] 2) Adjust the temperature of the heating platform to 200°C, treat for 0.5 hours, and use a cutter to peel off the softened backsheet layer. The peeled backsheet can be graded for use or recycled for high-value utilization;

[0034] 3) Adjust the heating platform temperature to 180°C and process for 1 hour to peel the crystalline silicon cell layer from the glass surface. The resulting intact glass can be used for grading or recycling, and the resulting cell layer with the EVA film can be processed later.

[0035] 4) Remove the battery layer with EVA film from the heating platform and cut it along the battery array to obtain 24 pieces of 20*10cm 2 Battery cells;

[0036] 5) Soak all cells together in liquid nitrogen for 5 minutes. The metals therein will shrink severely due to the low temperature and thus separate effectively. This step can completely expose the metals (such as silicon, aluminum, silver, indium or gallium). Figure 2-3 As shown in the figure, it is convenient for subsequent solvent purification and recovery (increasing the contact area), thereby avoiding the problems of difficult separation and purification caused by crushing and mixing used in the prior art, and can effectively shorten the solvent recovery time and improve the purity of metal separation;

[0037] 6) The cell after cryogenic treatment in step 5) is immersed in a high-concentration oxidizing acid (a mixture of concentrated hydrochloric acid and concentrated nitric acid in a volume ratio of 3:1) for recovery and release, thereby obtaining a metallic silicon material with a high purity (about 85%). The obtained metallic silicon can be graded for use or recycled for high-value utilization;

[0038] 7) Alternatively, aluminum (Al) is dissolved, recovered, and released through a solvent NaOH solution to obtain a metallic aluminum material with a relatively high purity (90%), which can be graded for use or recycled for high-value utilization.

[0039] Comparative Example 1

[0040] The specific steps for recycling retired photovoltaic modules without cryogenic treatment are as follows:

[0041] 1) Place the complete photovoltaic module on a heating platform at 100°C for 1 hour, remove the aluminum frame and junction box, and obtain a complete photovoltaic laminate;

[0042] 2) Adjust the temperature of the heating platform to 200°C, treat for 0.5 hours, and use a cutter to peel off the softened backsheet layer. The peeled backsheet can be graded for use or recycled for high-value utilization;

[0043] 3) Adjust the heating platform temperature to 180°C and process for 1 hour to peel the crystalline silicon cell layer from the glass surface. The resulting intact glass can be used for grading or recycling, and the resulting cell layer with the EVA film can be processed later.

[0044] 4) The battery layer with the EVA film is removed from the heating platform and directly crushed to obtain metal and EVA mixed particles;

[0045] 5) treating the mixed particles by high-concentration oxidizing acid leaching to obtain a metallic silicon material with a purity of approximately 60%;

[0046] 6) Alternatively, the mixed particles are treated with a solvent such as NaOH solution to obtain a metallic aluminum material with a purity of approximately 65%.

[0047] Example 2

[0048] A method for high-efficiency recycling of retired photovoltaic modules using heat treatment and cryogenic dual-assisted separation, comprising the following steps:

[0049] 1) Place the complete photovoltaic module on a heating platform at 200°C for 0.1 hour, remove the aluminum frame and junction box, and obtain a complete photovoltaic laminate;

[0050] 2) Adjust the temperature of the heating platform to 150°C and treat for 2 hours. Use a cutter to peel off the softened backsheet layer. The peeled backsheet can be graded for use or recycled for high-value utilization;

[0051] 3) Adjust the heating platform temperature to 250°C and process for 0.1 hour to peel the crystalline silicon cell layer from the glass surface. The resulting intact glass can be used for grading or recycling, and the cell layer with the EVA film is obtained for subsequent processing;

[0052] 4) Remove the battery layer with EVA film from the heating platform and cut it along the battery array to obtain 48 pieces of 10*10cm 2 Battery cells;

[0053] 5) Soak all cells together in dry ice acetone for 30 minutes. The metal will shrink severely due to the low temperature and thus be effectively separated. This step can completely expose the metal material ( Figure 2-3 The following figure shows the structure of the solvent (shown) which is convenient for subsequent solvent purification and recovery (increasing the contact area), avoiding the problems of difficult separation and purification caused by crushing and mixing, effectively shortening the solvent recovery time, and improving the purity of metal separation;

[0054] 6) Silicon (Si) metal is dissolved, recovered and released through high-concentration oxidative acid leaching to obtain metallic silicon material with high purity (about 85%), which can be graded for use or recycled for high-value utilization;

[0055] 7) Recover and release metallic aluminum through HNO3 dissolution to obtain metallic aluminum material with high purity (95%), which can be graded for use or recycled for high value utilization;

[0056] 8) Through the technical route of "chlorination precipitation-ammonia dissolution-hydrazine hydrate reduction", efficient separation and recovery of Ag is achieved, with a recovery efficiency of more than 95%.

[0057] Example 3

[0058] A method for high-efficiency recycling of retired photovoltaic modules using heat treatment and cryogenic dual-assisted separation, comprising the following steps:

[0059] 1) Place the complete photovoltaic module on a heating platform at 100°C for 2 hours, remove the aluminum frame and junction box, and obtain a complete photovoltaic laminate;

[0060] 2) Adjust the temperature of the heating platform to 250°C and treat for 0.2 hours. Use a cutter to peel off the softened backsheet layer. The peeled backsheet can be graded for use or recycled for high-value utilization;

[0061] 3) Adjust the heating platform temperature to 160°C and process for 0.5 hours to peel the crystalline silicon cell layer from the glass surface. The resulting intact glass can be used for grading or recycling, and the cell layer with the EVA film is obtained for subsequent processing;

[0062] 4) Remove the battery layer with EVA film from the heating platform and cut it along the battery array to obtain 60 pieces of 8*10cm 2 Battery cells;

[0063] 5) All cells are immersed in dry ice acetonitrile for 90 minutes. The metal layer shrinks severely due to the low temperature and is effectively separated. This step can completely expose the metal material (silicon, aluminum, silver, indium, gallium and other metals) (as shown in Figure 2-3), facilitating subsequent solvent purification and recovery (increasing the contact area), avoiding the problems of separation and purification caused by crushing and mixing, effectively shortening the solvent recovery time, and improving the purity of metal separation;

[0064] 6) Silicon (Si) metal is dissolved, recovered and released through high-concentration oxidative acid leaching to obtain metallic silicon material with high purity (about 85%), which can be graded for use or recycled for high-value utilization;

[0065] 7) Recover and release metallic aluminum through HNO3 dissolution to obtain metallic aluminum material with high purity (95%), which can be graded for use or recycled for high value utilization;

[0066] 8) Through the NaOH technical route, efficient separation and recovery of Ag was achieved, with a recovery efficiency of over 95%. SEM sample preparation and characterization process:

[0067] In step 5) of Example 1, the cell is effectively separated from the silicon layer by deep cooling to obtain two samples (distinguished by upper and lower samples respectively); the upper and lower samples are characterized by cross-section using SEM-EDS, and the SEM images are as follows: Figure 2 As shown. It can be observed that the battery layer can be mainly based on a multi-layer structure (such as Figure 2 a, d). EDS (energy dispersive spectrum analysis) can further distinguish the constituent elements of the layered structure. The cross section is mainly composed of silicon (Si) and aluminum (Al), and the crack surface is mainly composed of silicon (Si) ( Figure 2 b, e), aluminum (Al) element can also be observed in the cross section.

[0068] Subsequently, the surface microstructure and elemental composition of the crack surface were observed by SEM-EDS. The results of the upper and lower surfaces were similar, so only the results of the upper sample were used as an example to show and illustrate the specific results. Figure 3 As shown. Figure 3 It can be found in a that there is a detailed linear groove structure on the crack surface. Through EDS analysis, it is found that the elements on the crack surface are mainly Si ( Figure 3 b), and a small amount of Al( Figure 3 c), Gallium (Ga) element ( Figure 3 f), the linear groove structure is mainly composed of silver (Ag) (Figure 3d), indium (In) ( Figure 3 e); It can be seen that the method of the present invention can effectively recover various metal materials.

Claims

1. A method for separating and recycling retired photovoltaic modules, wherein the retired photovoltaic modules include an additional structure and a laminate, wherein the additional structure includes a junction box and a frame, and the laminate includes a glass layer, a first sealing material layer, a crystalline silicon cell layer, a second sealing material layer, and a backsheet; characterized in that: The separation and recovery method comprises the following steps: 1) removing the additional structure of the retired photovoltaic modules through heat treatment to obtain a complete laminate; 2) The obtained laminate is subjected to heat treatment to soften the backsheet, and the softened backsheet is completely peeled off using a tool to obtain a recycled polymer backsheet material; 3) The remaining components containing the glass layer and the crystalline silicon cell layer continue to undergo heat treatment to peel the crystalline silicon cell layer from the glass surface, obtaining a complete glass material and a crystalline silicon cell layer with sealing material adhered to the upper and lower surfaces; 4) The crystalline silicon cell layer with sealing material on both the upper and lower surfaces is cut into regular cell pieces, and then the regularly shaped cell pieces are cryogenically treated at -190 to -20°C. After the cryogenic treatment, the crystalline silicon cell pieces are split apart. Since the metal in the crystalline silicon cell piece shrinks at low temperature, the metal in the crystalline silicon cell piece is completely exposed. 5) Recover aluminum, silicon, silver, indium or gallium using solvent dissolution recovery method; In step 4), the cryogenic treatment is carried out as follows: quenching with dry ice and acetone for 30 minutes or quenching with dry ice and acetonitrile for 90 minutes; cutting the regular battery cells into 10×10 cm 2 or 8×10cm 2 ; In step 5), the solvent in the solvent dissolution recovery method is one or more of: NaOH, HNO3, a high-concentration oxidizing acid mixed with concentrated hydrochloric acid and concentrated nitric acid in a volume ratio of 3:

1.

2. The method for separating and recycling retired photovoltaic modules according to claim 1, characterized in that: In steps 1) to 3), the heat treatment temperature is 100 to 250° C., and the heat treatment time is 0.1 to 2 hours.

3. A method for separating and recycling retired photovoltaic modules according to any one of claims 1 to 2, characterized in that: The recycling method further comprises the following steps: Step 2) the obtained polymer backplane material is subjected to classification treatment and used directly, or reused with high added value.

4. A method for separating and recycling retired photovoltaic modules according to any one of claims 1 to 2, characterized in that: The recycling method further comprises the following steps: Step 3) the obtained glass material is subjected to classification treatment and used directly, or recycled and reused.

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