Method for recovering copper and tin from waste photovoltaic panels

Abstract

This application provides a method for recovering copper and tin from waste photovoltaic panels, belonging to the field of solid waste separation and recycling technology. The method includes: providing photovoltaic solder strip; subjecting the photovoltaic solder strip to a first heat treatment at a first temperature to obtain a heat-treated photovoltaic solder strip; placing the heat-treated photovoltaic solder strip in an inorganic salt solution and cooling it to room temperature to obtain a pre-treated photovoltaic solder strip; subjecting the pre-treated photovoltaic solder strip to a second heat treatment at a second temperature to achieve solid-liquid separation, obtaining solid copper and liquid tin; where 100℃ ≤ first temperature < tin melting point temperature; and tin melting point temperature < second temperature < copper melting point temperature. The method for recovering copper and tin provided by this application can improve the purity of the recovered copper.

Description

Technical Field

[0001] This application belongs to the field of solid waste separation and recycling technology, and more specifically, it relates to a method for recycling copper and tin from waste photovoltaic panels. Background Technology

[0002] The lifespan of photovoltaic (PV) panels is generally 15-20 years. With the rapid development of the PV industry, the resource recycling of waste PV panels has gradually become a research topic. The solder strips in PV panels are tin-plated copper strips, with a copper content generally higher than 80 wt% and a tin content generally not less than 15 wt%, possessing significant recycling value.

[0003] Copper and tin have significantly different melting points. They can be separated by heating to create a solid-liquid two-phase system. However, because molten tin easily adheres to the copper surface, the purity of the recovered copper is relatively low. To address this issue, existing technologies typically employ high-temperature chlorination or vacuum distillation.

[0004] The invention patent with publication number CN118957275A utilizes the differences in volatilization temperatures of various metal chlorides to convert molten tin into volatile tin chloride through a high-temperature chlorination reaction, thereby purifying metallic copper. However, this process requires the chlorination reaction to be carried out at temperatures above 1000℃, placing high demands on the equipment and requiring multiple cooling and separation steps, thus limiting its large-scale industrial application due to equipment and cost constraints.

[0005] Vacuum distillation technology separates copper and tin by controlling temperature and vacuum levels, allowing molten tin to evaporate as metal vapor. However, the vacuum distillation process requires maintaining extremely low vacuum levels, placing very high demands on equipment sealing, resulting in expensive equipment and high costs for industrial applications. Summary of the Invention

[0006] In view of the above problems, this application provides a method for recycling copper and tin from waste photovoltaic panels, thereby solving or at least alleviating one or more of the above-mentioned problems and other problems existing in the prior art.

[0007] This application provides a method for recycling copper and tin from waste photovoltaic panels, including:

[0008] Provide photovoltaic welding strips;

[0009] The photovoltaic ribbon is subjected to a first heat treatment at a first temperature to obtain a heat-treated photovoltaic ribbon.

[0010] The heat-treated photovoltaic ribbon was placed in an inorganic salt solution and cooled to room temperature to obtain a pretreated photovoltaic ribbon.

[0011] The pretreated photovoltaic ribbon is subjected to a second heating treatment at a second temperature to separate solid and liquid, resulting in solid copper and liquid tin.

[0012] 100℃≤first temperature<tin melting point temperature;

[0013] The melting point of tin is less than the second temperature, which is less than the melting point of copper.

[0014] In one embodiment, the first temperature is 150~200°C.

[0015] In one embodiment, the second temperature is 350~400°C.

[0016] In one embodiment, the first heat treatment time is 5 to 10 minutes.

[0017] In one embodiment, the first heat treatment and the second heat treatment are each performed independently in an inert atmosphere.

[0018] In one embodiment, the concentration of the inorganic salt solution is 5wt% to 20wt%.

[0019] In one embodiment, the solute in the inorganic salt solution includes ammonium chloride.

[0020] In one embodiment, the solute further includes at least one of sodium chloride and potassium chloride.

[0021] In one embodiment, the ammonium chloride accounts for 10% to 20% of the weight of the solute.

[0022] In one embodiment, the solid-liquid separation is performed under vibration conditions.

[0023] The beneficial effects of the embodiments of this application are as follows:

[0024] Unlike existing high-temperature chlorination or vacuum distillation processes, the recovery method described in this application requires no complex equipment, effectively reducing costs. This application solves the problem of low copper purity caused by molten tin easily adhering to the copper surface through the synergistic effect of two-stage heating treatment and rapid cooling with an inorganic salt solution. Specifically, this application utilizes the difference in thermal expansion coefficients between copper and tin. Through the first heating treatment and rapid cooling with an inorganic salt solution, stress is introduced at the interface between the tin layer and the copper substrate of the photovoltaic solder ribbon. During the second heating treatment, the tin layer melts, releasing the interfacial stress and promoting the molten tin to overcome the wetting and adsorption forces with the copper surface. This allows the molten tin to easily detach from the copper surface, thereby improving the purity of the recovered copper. Detailed Implementation

[0025] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0026] It should be understood that, unless the context clearly indicates otherwise, the terms “comprising,” “including,” or “having” as used herein refer to the presence of an element, but do not exclude the presence or addition of one or more other elements. Furthermore, as used herein, “comprising” and / or “including” indicate the presence of shapes, numbers, steps, operations, members, elements, and / or combinations thereof, and do not exclude the presence or addition of one or more other shapes, numbers, operations, elements, and / or combinations thereof.

[0027] In this application, the numerical range indicated by "~" refers to the range of values ​​specified as the lower and upper limits, respectively, before or after the term. When multiple values ​​for the upper or lower limit of any numerical range are mentioned, the range disclosed in this application can be understood as a range with any one of the mentioned upper limits as its upper limit and any one of the mentioned lower limits as its lower limit.

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the following will be illustrated through embodiments.

[0029] One embodiment of this application provides a method for recycling copper and tin from waste photovoltaic panels, including the following steps:

[0030] S1. Provide photovoltaic welding ribbon;

[0031] S2. The photovoltaic solder ribbon is subjected to a first heat treatment at a first temperature (100℃≤first temperature<tin melting point temperature) to obtain the heat-treated photovoltaic solder ribbon;

[0032] S3. Place the heat-treated photovoltaic ribbon in an inorganic salt solution and cool it to room temperature to obtain the pretreated photovoltaic ribbon.

[0033] S4. The pretreated photovoltaic solder ribbon is subjected to a second heating treatment at a second temperature (tin melting point temperature < second temperature < copper melting point temperature) to separate solid and liquid, and obtain solid copper and liquid tin.

[0034] In this embodiment, photovoltaic solder strips are obtained by disassembling waste photovoltaic panels, separating battery cells, and peeling solder strips. The photovoltaic solder strips undergo a first heat treatment within a temperature range of 100°C or higher and below the melting point of tin (232°C), utilizing the difference in thermal expansion coefficients between copper and tin (copper's thermal expansion coefficient is approximately 17 × 10⁻⁶). -6At ℃, the coefficient of thermal expansion of tin is approximately 22 × 10⁻⁶. -6 A thermal mismatch strain is introduced at the copper-tin interface ( / ℃). The heat-treated photovoltaic solder ribbon is then rapidly cooled by immersing it in an inorganic salt solution. The cooling contraction accumulates residual stress at the copper-tin interface, potentially leading to microscopic defects such as cracks. Finally, a second heating process is performed at a temperature range greater than the melting point of tin but less than the melting point of copper (1085℃), melting the tin layer. This releases the accumulated residual stress at the copper-tin interface, allowing the molten tin to overcome the wetting and adsorption forces on the copper surface. Under gravity or slight external force, the molten tin separates from the solid copper, yielding high-purity recycled copper.

[0035] In one embodiment of this application, the first temperature is 150~200℃ and the first heating treatment time is 5~10min.

[0036] In this embodiment, controlling the first heating temperature at 150~200℃ and the heating time at 5~10min can further improve the purity of the recovered copper. Within this range, the copper-tin interface has better thermal mismatch strain, which can better promote the molten tin to overcome the wetting and adsorption forces with the copper surface.

[0037] In one embodiment of this application, the second temperature is 350~400°C.

[0038] In this embodiment, controlling the second temperature between 350 and 400°C further improves the purity of the recovered copper. Within this temperature range, tin is ensured to melt fully, giving the molten tin better fluidity and making it easier to detach from the copper surface, thus further improving the purity of the recovered copper. Furthermore, within this temperature range, excessive energy consumption is avoided, reducing recycling costs and balancing energy utilization with recycling efficiency, thereby improving the economics of the method for recovering copper and tin from waste photovoltaic panels.

[0039] In one embodiment of this application, the first heat treatment and the second heat treatment are each carried out independently in an inert atmosphere.

[0040] In this embodiment, the first heat treatment is performed in an inert atmosphere to prevent the tin metal from being oxidized, ensuring that the process of generating stress due to thermal expansion differences is not interfered with by oxidation; the second heat treatment is performed in an inert atmosphere to ensure that the molten tin is not oxidized and to maintain the good fluidity of the molten tin. The inert atmosphere can be formed by inert gases commonly used in the art, such as, but not limited to, nitrogen and argon.

[0041] In one embodiment of this application, the concentration of the inorganic salt solution is 5wt% to 20wt%.

[0042] In this embodiment, controlling the concentration of the inorganic salt solution between 5 wt% and 20 wt% can further improve the purity of the recovered copper. Within this concentration range, the inorganic salt solution possesses suitable cooling capacity, fully utilizing the difference in thermal expansion between copper and tin to further increase the interfacial stress between them. This avoids the increased costs and subsequent processing difficulties that may result from excessively high concentrations, while also preventing the problem of poor cooling effects from excessively low concentrations. The inorganic salt solution can form a salt film during the cooling process, and its solute is preferably a chloride.

[0043] In one embodiment of this application, the chloride includes at least one of sodium chloride, potassium chloride, and ammonium chloride.

[0044] In this embodiment, ammonium chloride has a synergistic effect with sodium chloride and / or potassium chloride. On the one hand, their combination can prevent tin oxidation by forming a salt film; on the other hand, during the second heating process, ammonium chloride can decompose to generate reducing gas, which effectively prevents copper and tin from oxidizing at high temperatures, while also cleaning the metal surface and further ensuring the fluidity of the molten tin, thereby further improving the purity of the recovered copper. Preferably, ammonium chloride accounts for 10% to 20% of the chloride weight.

[0045] In one embodiment of this application, solid-liquid separation is performed under vibration conditions.

[0046] In this embodiment, by using vibration-assisted solid-liquid separation, the static equilibrium that may exist between the solid and liquid can be broken, further enhancing the fluidity of the molten tin and making it easier for it to detach from the solid copper surface. The vibration can be mechanical or ultrasonic.

[0047] The present application will now be described in detail with reference to preferred embodiments and comparative examples. The preferred embodiments described below according to the present application can be modified in various ways, and therefore the scope of the present application should not be construed as limited to the preferred embodiments described in detail below. Preferred embodiments are provided to help those skilled in the art to more readily understand the present application.

[0048] Example 1

[0049] A method for recycling copper and tin from waste photovoltaic panels includes the following steps:

[0050] S1. Disassemble waste photovoltaic panels, separate battery cells, and peel off the solder strips to obtain photovoltaic solder strips;

[0051] S2. The photovoltaic welding strip is heated at 100°C for 10 minutes under an argon atmosphere to obtain the heat-treated photovoltaic welding strip.

[0052] S3. The heat-treated photovoltaic ribbon is placed in a 5wt% potassium chloride solution and cooled to room temperature to obtain the pretreated photovoltaic ribbon.

[0053] S4. The pretreated photovoltaic ribbon is heated at 350°C under an argon atmosphere, and mechanical vibration (frequency 5Hz) is used to assist in solid-liquid separation to obtain solid copper and liquid tin.

[0054] After washing the surface of the solid copper with water, the surface of the solid copper was analyzed by XRF spectrometer, and the copper content was found to be 98.38 wt%.

[0055] Example 2

[0056] A method for recycling copper and tin from waste photovoltaic panels includes the following steps:

[0057] S1. Disassemble waste photovoltaic panels, separate battery cells, and peel off the solder strips to obtain photovoltaic solder strips;

[0058] S2. The photovoltaic welding strip is heated at 220°C for 5 minutes under an argon atmosphere to obtain the heat-treated photovoltaic welding strip.

[0059] S3. The heat-treated photovoltaic ribbon is placed in a 20wt% sodium chloride solution and cooled to room temperature to obtain the pretreated photovoltaic ribbon.

[0060] S4. The pretreated photovoltaic ribbon is heated at 400°C under an argon atmosphere, and mechanical vibration (frequency 5Hz) is used to assist in solid-liquid separation to obtain solid copper and liquid tin.

[0061] After washing the surface of the solid copper with water, the surface of the solid copper was analyzed by XRF spectrometer, and the copper content was found to be 98.84 wt%.

[0062] Example 3

[0063] A method for recycling copper and tin from waste photovoltaic panels includes the following steps:

[0064] S1. Disassemble waste photovoltaic panels, separate battery cells, and peel off the solder strips to obtain photovoltaic solder strips;

[0065] S2. The photovoltaic welding strip is heated at 100°C for 5 minutes under an argon atmosphere to obtain the heat-treated photovoltaic welding strip.

[0066] S3. The heat-treated photovoltaic ribbon is placed in a 20wt% sodium chloride solution and cooled to room temperature to obtain the pretreated photovoltaic ribbon.

[0067] S4. The pretreated photovoltaic ribbon is heated at 400°C under an argon atmosphere, and mechanical vibration (frequency 5Hz) is used to assist in solid-liquid separation to obtain solid copper and liquid tin.

[0068] After washing the surface of the solid copper with water, the surface of the solid copper was analyzed by XRF spectrometer, and the copper content was found to be 98.57 wt%.

[0069] Example 4

[0070] A method for recycling copper and tin from waste photovoltaic panels includes the following steps:

[0071] S1. Disassemble waste photovoltaic panels, separate battery cells, and peel off the solder strips to obtain photovoltaic solder strips;

[0072] S2. The photovoltaic welding strip is heated at 150°C for 5 minutes under an argon atmosphere to obtain the heat-treated photovoltaic welding strip.

[0073] S3. The heat-treated photovoltaic ribbon is placed in a 20wt% sodium chloride solution and cooled to room temperature to obtain the pretreated photovoltaic ribbon.

[0074] S4. The pretreated photovoltaic ribbon is heated at 400°C under an argon atmosphere, and mechanical vibration (frequency 5Hz) is used to assist in solid-liquid separation to obtain solid copper and liquid tin.

[0075] After washing the surface of the solid copper with water, the surface of the solid copper was analyzed by XRF spectrometry, and the copper content was found to be 99.23 wt%.

[0076] Example 5

[0077] A method for recycling copper and tin from waste photovoltaic panels includes the following steps:

[0078] S1. Disassemble waste photovoltaic panels, separate battery cells, and peel off the solder strips to obtain photovoltaic solder strips;

[0079] S2. The photovoltaic welding strip is heated at 200°C for 5 minutes under an argon atmosphere to obtain the heat-treated photovoltaic welding strip.

[0080] S3. The heat-treated photovoltaic ribbon is placed in a 20wt% sodium chloride solution and cooled to room temperature to obtain the pretreated photovoltaic ribbon.

[0081] S4. The pretreated photovoltaic ribbon is heated at 400°C under an argon atmosphere, and mechanical vibration (frequency 5Hz) is used to assist in solid-liquid separation to obtain solid copper and liquid tin.

[0082] After washing the surface of the solid copper with water, the surface of the solid copper was analyzed by XRF spectrometer, and the copper content was found to be 99.48 wt%.

[0083] Example 6

[0084] A method for recycling copper and tin from waste photovoltaic panels includes the following steps:

[0085] S1. Disassemble waste photovoltaic panels, separate battery cells, and peel off the solder strips to obtain photovoltaic solder strips;

[0086] S2. The photovoltaic welding strip is heated at 200°C for 5 minutes under an argon atmosphere to obtain the heat-treated photovoltaic welding strip.

[0087] S3. The heat-treated photovoltaic ribbon is placed in a 20wt% ammonium chloride solution and cooled to room temperature to obtain the pretreated photovoltaic ribbon.

[0088] S4. The pretreated photovoltaic ribbon is heated at 400°C under an argon atmosphere, and mechanical vibration (frequency 5Hz) is used to assist in solid-liquid separation to obtain solid copper and liquid tin.

[0089] After washing the surface of the solid copper with water, the surface of the solid copper was analyzed by XRF spectrometer, and the copper content was found to be 99.37 wt%.

[0090] Example 7

[0091] A method for recycling copper and tin from waste photovoltaic panels includes the following steps:

[0092] S1. Disassemble waste photovoltaic panels, separate battery cells, and peel off the solder strips to obtain photovoltaic solder strips;

[0093] S2. The photovoltaic welding strip is heated at 200°C for 5 minutes under an argon atmosphere to obtain the heat-treated photovoltaic welding strip.

[0094] S3. The heat-treated photovoltaic ribbon is placed in a 20wt% inorganic salt solution (solutes include sodium chloride and ammonium chloride, with a weight ratio of sodium chloride to ammonium chloride of 9:1) and cooled to room temperature to obtain the pretreated photovoltaic ribbon.

[0095] S4. The pretreated photovoltaic ribbon is heated at 400°C under an argon atmosphere, and mechanical vibration (frequency 5Hz) is used to assist in solid-liquid separation to obtain solid copper and liquid tin.

[0096] After washing the surface of the solid copper with water, the surface of the solid copper was analyzed by XRF spectrometer, and the copper content was found to be 99.65 wt%.

[0097] Example 8

[0098] A method for recycling copper and tin from waste photovoltaic panels includes the following steps:

[0099] S1. Disassemble waste photovoltaic panels, separate battery cells, and peel off the solder strips to obtain photovoltaic solder strips;

[0100] S2. The photovoltaic welding strip is heated at 200°C for 5 minutes under an argon atmosphere to obtain the heat-treated photovoltaic welding strip.

[0101] S3. The heat-treated photovoltaic ribbon is placed in a 20wt% inorganic salt solution (solutes include sodium chloride and ammonium chloride, with a weight ratio of sodium chloride to ammonium chloride of 8:2) and cooled to room temperature to obtain the pretreated photovoltaic ribbon.

[0102] S4. The pretreated photovoltaic ribbon is heated at 400°C under an argon atmosphere, and mechanical vibration (frequency 5Hz) is used to assist in solid-liquid separation to obtain solid copper and liquid tin.

[0103] After washing the surface of the solid copper with water, the surface of the solid copper was analyzed by XRF spectrometer, and the copper content was found to be 99.84 wt%.

[0104] Comparative Example 1

[0105] A method for recycling copper and tin from waste photovoltaic panels includes the following steps:

[0106] S1. Disassemble waste photovoltaic panels, separate battery cells, and peel off the solder strips to obtain photovoltaic solder strips;

[0107] S2. The photovoltaic welding strip is heated at 80°C for 10 minutes under an argon atmosphere to obtain the heat-treated photovoltaic welding strip.

[0108] S3. The heat-treated photovoltaic ribbon is placed in a 5wt% potassium chloride solution and cooled to room temperature to obtain the pretreated photovoltaic ribbon.

[0109] S4. The pretreated photovoltaic ribbon is heated at 350°C under an argon atmosphere, and mechanical vibration (frequency 5Hz) is used to assist in solid-liquid separation to obtain solid copper and liquid tin.

[0110] After washing the surface of the solid copper with water, the surface of the solid copper was analyzed by XRF spectrometer, and the copper content was found to be 96.63 wt%.

[0111] Comparative Example 2

[0112] A method for recycling copper and tin from waste photovoltaic panels includes the following steps:

[0113] S1. Disassemble waste photovoltaic panels, separate battery cells, and peel off the solder strips to obtain photovoltaic solder strips;

[0114] S2. The photovoltaic solder ribbon is heated at 350°C under an argon atmosphere, and mechanical vibration (frequency 5Hz) is used to assist in solid-liquid separation to obtain solid copper and liquid tin.

[0115] After washing the surface of the solid copper with water, the surface of the solid copper was analyzed by XRF spectrometry, and the copper content was found to be 92.71 wt%.

[0116] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for recovering copper and tin from waste photovoltaic panels, characterized by, include: Provide photovoltaic welding strips; The photovoltaic ribbon is subjected to a first heat treatment at a first temperature to obtain a heat-treated photovoltaic ribbon. The heat-treated photovoltaic ribbon is placed in an inorganic salt solution and cooled to room temperature to obtain a pretreated photovoltaic ribbon. The solute in the inorganic salt solution includes at least one of sodium chloride and potassium chloride and ammonium chloride. The pretreated photovoltaic ribbon is subjected to a second heating treatment at a second temperature to separate solid and liquid, resulting in solid copper and liquid tin. 100℃≤first temperature<tin melting point temperature; The melting point of tin is less than the second temperature, which is less than the melting point of copper.

2. A method of recovering copper and tin from waste photovoltaic panels according to claim 1, characterized in that, The first temperature is 150~200℃.

3. The method for recycling copper and tin from waste photovoltaic panels as described in claim 1, characterized in that, The second temperature is 350~400℃.

4. The method for recovering copper and tin from waste photovoltaic panels according to claim 1, characterized in that, The first heating treatment lasts for 5 to 10 minutes.

5. A method of recovering copper and tin from waste photovoltaic panels according to claim 1, characterized in that, The first heat treatment and the second heat treatment are each carried out independently in an inert atmosphere.

6. A method of recovering copper and tin from waste photovoltaic panels according to claim 1, characterized in that, The concentration of the inorganic salt solution is 5wt%~20wt%.

7. A method of recovering copper and tin from waste photovoltaic panels according to claim 1, characterized in that, The ammonium chloride accounts for 10% to 20% of the weight of the solute.

8. The method for recycling copper and tin from waste photovoltaic panels as described in claim 1, characterized in that, The solid-liquid separation is carried out under vibration conditions.