A method for recycling and reusing waste photovoltaic welding ribbon

Abstract

This invention provides a method for recycling and reusing waste photovoltaic solder ribbon. The method includes: mechanically dismantling or thermally decomposing waste solar panels to obtain photovoltaic solder ribbon; pre-oxidizing the photovoltaic solder ribbon under an oxidizing atmosphere to obtain oxidized photovoltaic solder ribbon; immersing the oxidized photovoltaic solder ribbon in an alkaline solution and then filtering to obtain high-purity copper ribbon and primary filtrate; condensing and precipitating the primary filtrate to obtain high-purity sodium stannate and secondary filtrate; performing preliminary electroplating on the secondary filtrate under low pressure to obtain high-purity lead and an electrolytic mixture; and then performing secondary electroplating on the electrolytic mixture under high voltage to obtain high-purity tin. Compared with the traditional acid leaching + oxidant oxidation method, this invention has advantages such as environmental friendliness, short process, low energy consumption, and high recovery rate.

Description

Technical Field

[0001] This invention relates to the field of recycling valuable copper, tin and lead metals from waste photovoltaic panels, and particularly to a method for recycling and reusing waste photovoltaic solder strips. Background Technology

[0002] With the continuous development of the global economy, energy consumption is increasing, and the depletion of fossil fuels has become a primary problem facing us today. Among the many renewable energy sources, solar energy, with its advantages of abundant resources and no environmental pollution, has broad development prospects. Currently, solar panels are mainly divided into three types: crystalline silicon solar panels, thin-film solar panels, and new types of solar panels. Among them, crystalline silicon solar panels occupy about 80% of the market share due to their high conversion efficiency and low cost. Currently, the lifespan of solar cells on the market is 20-30 years. After this period, the conversion efficiency of solar cells drops sharply. Based on an estimated 25-year service life, my country will begin to enter a period of intensive scrapping around 2025, resulting in a large number of discarded solar panels in the near future.

[0003] Photovoltaic solder ribbons in crystalline silicon solar panels primarily function as current collectors and conductors. Their main components are valuable and potentially hazardous elements such as copper, tin, and lead. This makes the recycling of the large quantities of photovoltaic solder ribbons from discarded solar panels a pressing issue: on the one hand, they contain significant amounts of valuable metals, making them highly valuable for recycling; on the other hand, they contain large amounts of the heavy metal lead, posing a serious threat to the environment. Therefore, the full recycling and utilization of photovoltaic solder ribbons from discarded photovoltaic modules has significant economic and environmental implications.

[0004] However, existing methods have drawbacks such as being difficult to operate, environmentally unfriendly, and having complex processes. Therefore, it is necessary to develop a comprehensive method for recycling photovoltaic welding ribbon that is low-cost, easy to operate, environmentally friendly, and has a short process. Summary of the Invention

[0005] The purpose of this invention is to provide a method for recycling and reusing waste photovoltaic welding ribbon. The copper, lead, and tin metals recovered by this invention have high purity. The preparation method has the advantages of abundant raw materials, low cost, simple operation, time saving, and no environmental pollution.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a method for recycling and reusing waste photovoltaic welding ribbon, the method comprising:

[0008] Waste solar panels are mechanically dismantled or thermally decomposed to obtain photovoltaic ribbons;

[0009] The photovoltaic ribbon is pre-oxidized under an oxidizing atmosphere to obtain an oxidized photovoltaic ribbon.

[0010] The oxidized photovoltaic ribbon was immersed in an alkaline solution and then filtered to obtain a high-purity copper ribbon and a primary filtrate.

[0011] The primary filtrate is condensed to precipitate and then filtered to obtain high-purity sodium stannate and a secondary filtrate.

[0012] The secondary filtrate is subjected to preliminary electroplating under low pressure to obtain a mixture of high-purity lead and electrolytic solution; then the electrolytic solution is subjected to secondary electroplating under high voltage to obtain high-purity tin.

[0013] Furthermore, the pre-oxidation temperature is 300–700°C, and the pre-oxidation time is 5–180 min.

[0014] Further, the alkaline solution is at least one of sodium hydroxide and potassium hydroxide; the mass concentration of the alkaline solution is 1 wt.% to 70 wt.%, the temperature of the alkaline solution is 20 to 200°C, and the immersion time is 30 to 180 min. Further, the temperature of condensation is 0 to 30°C.

[0015] Furthermore, the voltage of the initial electroplating is 0.5 to 1.4V, and the temperature of the initial electroplating is 20 to 100°C.

[0016] Furthermore, the voltage of the secondary electroplating is 1.0 to 2.0V, and the temperature of the secondary electroplating is 20 to 100°C.

[0017] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0018] This invention provides a method for recycling and reusing waste photovoltaic solder ribbon. Using waste photovoltaic solder ribbon as raw material, the method employs high-temperature selective pre-oxidation of lead and tin on the surface of the solder ribbon. The oxides of lead and tin on the surface are removed by alkaline leaching to obtain pure copper ribbon. The filtrate is condensed and filtered to obtain sodium stannate. The leachate is then electroplated to obtain pure lead and pure tin. The copper, lead, and tin recovered by this invention have high purity (purity ≥ 99%). Compared with traditional methods, the preparation method of this invention has the following advantages: (1) the oxidant is air or other oxidizing atmosphere, which is inexpensive and readily available; (2) the reagents are simple and readily available, without toxic or harmful reagents; (3) compared with traditional recycling, the recovery purity is high and the operation process is short; (4) the generation of toxic and harmful waste liquid is avoided; and (5) the full component recovery of the solder ribbon is achieved. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart illustrating a method for recycling and reusing waste photovoltaic welding ribbon, as provided in an embodiment of the present invention.

[0021] Figure 2 Photographs of copper, lead, and tin recovered in an embodiment of the present invention. Detailed Implementation

[0022] The present invention will be described in detail below with reference to specific embodiments and examples, thereby making the advantages and various effects of the present invention more clearly apparent. Those skilled in the art should understand that these specific embodiments and examples are for illustrative purposes only and are not intended to limit the present invention.

[0023] Throughout this specification, unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of any conflict, this specification shall prevail.

[0024] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be obtained by purchasing them from the market or by existing methods.

[0025] The technical solution of this application embodiment is to solve the above-mentioned technical problems, and the general idea is as follows:

[0026] This invention provides a method for recycling and reusing waste photovoltaic welding ribbon, such as... Figure 1 As shown, the method includes:

[0027] Step S1: Mechanically dismantle or thermally decompose the waste solar panels to obtain photovoltaic ribbon;

[0028] In step S1

[0029] As a specific implementation method, the mechanical disassembly can be carried out by mechanical crushing and screening to initially separate the various components of the solar panel.

[0030] In one specific implementation, the thermal decomposition involves heating the battery to 400-500°C at a rate of 18-22°C / min and holding at that temperature for 40-50 minutes. The thermal decomposition is carried out in a muffle furnace, with the solar panel placed inside the furnace with the glass facing down and the back panel facing up.

[0031] Step S2: Pre-oxidize the photovoltaic ribbon under an oxidizing atmosphere to obtain an oxidized photovoltaic ribbon;

[0032] In step S2

[0033] In the pre-oxidation reaction, the pre-oxidation temperature is 300–700°C, and the pre-oxidation time is 5–180 min (preferably 30–150 min).

[0034] The pre-oxidation reaction is carried out in a high-temperature furnace.

[0035] In the pre-oxidation reaction, the lead and tin on the solder strip surface are oxidized through high-temperature oxidation. If the temperature is below 300℃ and the time is less than 5 minutes, the lead-tin coating on the solder strip surface cannot be oxidized. If the temperature is above 700℃ and the time is greater than 180 minutes, it will lead to the oxidation of the copper strip inside the solder strip, which is not conducive to the complete recovery of the solder strip components.

[0036] Step S3: Immerse the oxidized photovoltaic ribbon in an alkaline solution, then filter to obtain a high-purity copper ribbon and a primary filtrate;

[0037] In step S3

[0038] The alkaline solution is at least one of sodium hydroxide and potassium hydroxide;

[0039] The alkaline solution has a mass concentration of 1 wt.% to 70 wt.%, a temperature of 20 to 200°C, and an immersion time of 30 to 180 minutes. If the alkali is weak, the concentration is below 1 wt.%, the temperature is below 20°C, and the immersion time is less than 30 minutes, the lead-tin coating on the solder strip surface cannot be leached out. If the concentration is above 70 wt.%, the temperature is above 200°C, and the immersion time is greater than 180 minutes, it will lead to partial leaching of copper from inside the solder strip and waste of excessive alkali solution.

[0040] Preferably, the mass concentration of the alkaline solution is 1 wt.% to 30 wt.%, the temperature of the alkaline solution is 20 to 200°C, and the immersion time is 60 to 120 min.

[0041] In one specific implementation, the alkaline leaching reaction is carried out in a beaker; in other implementations, other containers may be used.

[0042] Step S4: The primary filtrate is condensed to precipitate and filtered to obtain high-purity sodium stannate and secondary filtrate;

[0043] In step S4, during the condensation and precipitation process, the condensation temperature is 0–30°C. If the temperature is higher than 30°C, the precipitation time of sodium stannate in the solution will increase.

[0044] Step S5: The secondary filtrate is subjected to preliminary electroplating under low pressure to obtain a high-purity lead and electrolytic mixture; then the electrolytic mixture is subjected to secondary electroplating under high voltage to obtain high-purity tin.

[0045] In step S5

[0046] In the initial electroplating process, the electrolysis voltage is 0.5–1.4V. If the voltage is higher than 1.4V, co-deposition of lead and tin will occur. If the voltage is lower than 0.5V, lead cannot be deposited.

[0047] During the secondary electroplating process, the electrolysis voltage is 1.0–2.0V. If the voltage is higher than 2.0V, severe H2 deposition will occur. If the voltage is lower than 1.0V, tin cannot be deposited.

[0048] The following will provide a detailed description of a method for recycling and reusing waste photovoltaic welding ribbon, based on embodiments and experimental data.

[0049] Example 1: A method for recycling and reusing waste photovoltaic welding ribbon

[0050] 1. Photovoltaic ribbon is obtained by pyrolyzing waste solar panels.

[0051] 2. Next, the photovoltaic solder ribbon is subjected to high-temperature pre-oxidation under air conditions to obtain an oxidized solder ribbon with a lead-tin alloy oxide coating on the surface. The pre-oxidation temperature is 700℃ and the pre-oxidation time is 60min to completely oxidize the lead-tin coating on its surface.

[0052] 3. The oxidized photovoltaic ribbon is leached in a concentrated alkaline solution, and the copper ribbon and primary filtrate are obtained by filtration. The concentrated alkaline solution is 30 wt.% NaOH, the leaching time is 60 min, and the alkaline solution temperature is 50℃.

[0053] 4. The primary filtrate is condensed, precipitated, and filtered to obtain high-purity sodium stannate and a secondary filtrate. The condensation temperature is 10℃.

[0054] 5. The secondary filtrate is subjected to preliminary electrolysis to recover pure lead, wherein the electrolysis voltage is 1.0V and the temperature is 80℃. After lead no longer deposits, the electrolysis voltage is increased, and electrolysis is continued to recover pure tin, wherein the electrolysis voltage is 1.4V and the temperature is 80℃. The recovery rates of copper, lead, and tin obtained in this embodiment of the invention are determined.

[0055] Example 2: A method for recycling and reusing waste photovoltaic welding ribbon

[0056] 1. Photovoltaic ribbon is obtained by pyrolyzing waste solar panels.

[0057] 2. Next, the solder ribbon is subjected to high-temperature oxidation under air conditions to obtain an oxidized solder ribbon with a lead-tin alloy oxide coating on the surface. The pre-oxidation temperature is 400℃ and the pre-oxidation time is 150min to ensure that the lead-tin coating on the surface is completely oxidized.

[0058] 3. The oxidized photovoltaic ribbon is immersed in a concentrated alkaline solution, and the copper ribbon and primary filtrate are obtained by filtration. The concentrated alkali is 10 wt.% NaOH, the immersion time is 80 min, and the alkaline solution temperature is 60℃.

[0059] 4. The primary filtrate is condensed, precipitated, and filtered to obtain high-purity sodium stannate and a secondary filtrate. The condensation temperature is 20℃.

[0060] 5. The secondary filtrate is subjected to preliminary electrolysis to recover pure lead, wherein the electrolysis voltage is 0.8V and the temperature is 90℃. After lead no longer deposits, the electrolysis voltage is increased, and electrolysis is continued to recover pure tin, wherein the electrolysis voltage is 1.6V and the temperature is 90℃. The recovery rates of copper, lead, and tin obtained in this embodiment of the invention are determined.

[0061] Example 3: A method for recycling and reusing waste photovoltaic welding ribbon

[0062] 1. Photovoltaic ribbon is obtained by pyrolyzing waste solar panels.

[0063] 2. Next, the solder ribbon is subjected to high-temperature oxidation under air conditions to obtain an oxidized solder ribbon with a lead-tin alloy oxide coating on the surface. The pre-oxidation temperature is 300℃ and the pre-oxidation time is 30min to ensure that the lead-tin coating on the surface is completely oxidized.

[0064] 3. The oxidized photovoltaic ribbon is immersed in a concentrated alkaline solution, and the copper ribbon and primary filtrate are obtained by filtration. The concentrated alkali is 1 wt.% KOH, the immersion time is 120 min, and the alkaline solution temperature is 20℃.

[0065] 4. The primary filtrate is condensed, precipitated, and filtered to obtain high-purity sodium stannate and a secondary filtrate. The condensation temperature is 25℃.

[0066] 5. The secondary filtrate is subjected to preliminary electrolysis to recover pure lead, wherein the electrolysis voltage is 0.6V and the temperature is 50℃. After lead no longer deposits, the electrolysis voltage is increased, and electrolysis is continued to recover pure tin, wherein the electrolysis voltage is 1.2V and the temperature is 50℃. The recovery rates of copper, lead, and tin obtained in this embodiment of the invention are determined.

[0067] Comparative Example 1

[0068] This comparative example uses a traditional acid leaching + oxidant oxidation method. The specific steps are as follows: 5M HNO3 is used to completely dissolve the solder strip, and LIX84-I is used to extract copper. H2SO4 is added to the copper-containing extract for a two-step extraction to obtain a copper sulfate solution, which is then electrorefined to obtain elemental copper. 5M NaOH is added to the primary raffinate, and the mixture is filtered at room temperature to obtain a lead-containing precipitate. Sodium sulfide is added to the filtrate to form a PbS precipitate, which is further filtered to recover the lead.

[0069] In this method, copper recovery rate is 95%, while lead recovery rate is only 93%. The entire process involves the use of large amounts of toxic acid and alkali reagents. The recovered lead exists in the form of oxides and salts, which have low value, and tin is not recovered in the waste liquid.

[0070] Experiment Example 1, Performance Measurement

[0071] The statistics of each embodiment and each comparative example are shown in Table 1;

[0072] Table 1

[0073]

[0074]

[0075] The data in Table 1 shows that:

[0076] Comparative Example 1 uses the traditional acid leaching + oxidant oxidation method, with a recovery rate as low as 93-95%. It has the disadvantages of being toxic and harmful, having a complex process, low recovery rate, and low added value of the recovered products.

[0077] In Examples 1-3, the copper, lead and tin recovered by the present invention have high purity (purity ≥ 99%). The preparation method has the advantages of abundant raw materials, low cost, simple operation process, time saving and no pollution to the environment.

[0078] Finally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0079] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0080] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for recycling and reusing waste photovoltaic welding ribbon, characterized in that, The method includes: Waste solar panels are mechanically dismantled or thermally decomposed to obtain photovoltaic ribbons; The photovoltaic ribbon is pre-oxidized under an oxidizing atmosphere to obtain an oxidized photovoltaic ribbon. The oxidized photovoltaic ribbon was immersed in an alkaline solution and then filtered to obtain a high-purity copper ribbon and a primary filtrate. The primary filtrate is condensed to precipitate and then filtered to obtain high-purity sodium stannate and a secondary filtrate. The secondary filtrate is subjected to preliminary electroplating under low pressure to obtain a mixture of high-purity lead and electrolytic solution; then the electrolytic solution is subjected to secondary electroplating under high voltage to obtain high-purity tin. The pre-oxidation temperature is 300–700 °C, the pre-oxidation time is 5–180 min, the alkaline solution is at least one of sodium hydroxide and potassium hydroxide; the mass concentration of the alkaline solution is 1 wt.%–70 wt.%, the temperature of the alkaline solution is 20–200 °C, the immersion time in the alkaline solution is 30–180 min, the condensation temperature is 0–30 °C, the voltage of the initial electroplating is 0.5–1.4 V, the temperature of the initial electroplating is 20–100 °C, the voltage of the secondary electroplating is 1.0–2.0 V, and the temperature of the secondary electroplating is 20–100 °C.

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