Separation and recovery method for valuable metal in retired photovoltaic module solder strip

Abstract

The invention discloses a method for separating and recycling valuable metals in a retired photovoltaic module solder strip, which comprises the following steps: firstly, carrying out mechanical disassembly and thermal decomposition on a retired photovoltaic module, separating the solder strip and removing organic matters; then, a chlorinating agent is added, the temperature is controlled to range from 300 DEG C to 500 DEG C under the low-oxygen condition for a chlorination reaction, and the tin-lead alloy on the surface of the welding strip is converted into metal chloride and volatile gas with the low volatilization temperature. And through staged heating, tin chloride and lead chloride are collected at 600-700 DEG C and 800-900 DEG C respectively in sequence, residual solid copper is separated through a physical method, and metal copper is obtained. And the collected tin chloride and lead chloride are subjected to reduction or distillation treatment, and metal tin and lead are recovered. Through the temperature control volatilization and selective condensation technology, low-temperature efficient separation and recovery of valuable metal in the solder strip are achieved, the method has the advantages of being easy to operate, low in energy consumption and good in environmental protection property, and a new solution is provided for high-value utilization of waste resources in the photovoltaic industry.

Description

Technical Field

[0001] The present invention relates to the technical field of metal separation and recovery, and in particular to a method for separating and recovering valuable metals in welding strips of retired photovoltaic modules. Background Art

[0002] With the rapid development of the photovoltaic industry, the recycling of a large number of discarded photovoltaic components has gradually become a key issue. These components contain a variety of materials such as glass, aluminum frames, silicon wafers, and solder strips. Among them, solder strips have significant recycling value because they are rich in valuable metals such as copper, tin, and lead. However, the current recycling technology for valuable metals in solder strips still has some limitations.

[0003] The soldering ribbon in the photovoltaic module uses copper as the main base material, and its copper content is usually higher than 80% (wt%), and the surface is coated with a low-melting-point lead-tin alloy, which is used for current convergence and conduction between the cells. However, in the existing recycling process, the soldering ribbon often undergoes high-temperature treatment. During this process, the metal components in the soldering ribbon are very easy to oxidize, forming a complex mixture of metal oxides and metal elements. This chemical change greatly increases the difficulty of recycling and separation, resulting in resource waste and environmental pollution. In addition, the lead and tin contained in the photovoltaic soldering ribbon not only have high economic value, but also contain heavy metal lead, which poses a potential threat to the environment and human health. Therefore, how to effectively separate and recycle these valuable metals during the recycling process while reducing the impact of harmful substances on the environment is a key issue that needs to be urgently solved in the current field of photovoltaic module recycling.

[0004] Existing recycling technologies mainly include mechanical disassembly and chemical treatment. Mechanical disassembly methods are usually unable to efficiently separate different components, and the recovery rate of valuable metals in the welding strips is low; while chemical treatment methods can separate metal components, they often require high-energy-consuming processes or use highly corrosive chemical reagents, which can easily cause secondary pollution to the environment. Therefore, it is urgent to develop an efficient, environmentally friendly and economically feasible recycling process to achieve the separation and recovery of valuable metals in the welding strips of waste photovoltaic modules.

[0005] At present, although existing patents disclose some methods for separating and recovering valuable metals from photovoltaic module welding strips, they also have the following problems:

[0006] The problem of metal complexity in welding rods after aerobic pyrolysis: Pyrolysis treatment in an aerobic environment has been used to recover metal materials in photovoltaic welding strips (as described in the Chinese patent application with application number CN202411250455.9). This method oxidizes the welding strip through high-temperature pyrolysis to form a complex mixture of metal oxides and metal elements, and then uses a chlorination reaction and step-by-step cooling method to separate the metal. However, this process requires high temperature (above 1000°C) and multi-step cooling and separation, which is complicated to operate. At the same time, the formation of metal oxides may reduce the recovery efficiency. In addition, the oxidation process has high equipment requirements and may increase energy consumption, limiting its feasibility of large-scale industrial application.

[0007] Application limitations of vacuum distillation technology: A Chinese patent application with application number CN202410249724.3 proposes a method for separating copper, silver, tin and lead in solder strips using vacuum distillation technology. By controlling the temperature and vacuum degree, tin-lead alloy, pure copper and crude silver are separated. However, the process has the following limitations: First, the vacuum distillation process needs to maintain an extremely low vacuum degree (5–30Pa), and the equipment sealing requirements are extremely high; secondly, this method has strict requirements on the temperature control of separation (up to 1300–1400°C), and the energy consumption is significantly increased; in addition, the purity of crude silver and metallic tin is low, and subsequent treatment is still required to increase the recovery value. These problems increase the complexity of the process and the overall cost.

[0008] Environmental issues of alkali leaching and electroplating technology: The Chinese patent application with application number CN202311245588.2 describes a method for recovering metals from photovoltaic ribbons by alkali leaching and electroplating. Although the technical process is relatively simple, there are the following problems: First, the efficiency of alkali leaching is significantly limited by the concentration and temperature of the solution. High temperature and high concentration conditions may cause excessive dissolution of some copper or incomplete reaction; second, the electroplating process requires multi-step electrolysis, which consumes a lot of energy; in addition, the treatment and reuse of filtrate and electrolyte may bring potential environmental risks, especially in industrial-scale production. How to control waste liquid discharge is still a challenge to be solved.

[0009] In summary, the current photovoltaic ribbon recycling technology mainly faces the following common problems: First, the recycling process is complex and difficult to operate, especially the high dependence on multiple steps of high temperature, vacuum and other conditions; second, the balance between recycling efficiency and metal purity has not been fully resolved, and some processes are difficult to take into account the needs of efficient separation and low cost; third, environmental protection and sustainability need to be further improved. Therefore, a more efficient, simple and environmentally friendly recycling process is urgently needed to meet the needs of sustainable development of the photovoltaic industry. Summary of the invention

[0010] The technical problem to be solved by the present invention is to provide a method for separating and recovering valuable metals in welding strips of retired photovoltaic modules, so as to solve the problems of low separation efficiency, low recovery rate, complex operation and environmental pollution existing in conventional methods in the prior art.

[0011] In order to overcome the above defects of the prior art, the present invention provides a method for separating and recovering valuable metals in retired photovoltaic module welding strips, comprising the following steps:

[0012] S1: Thermal decomposition: After pretreatment, the solder strip is placed in a low-oxygen environment for thermal decomposition to decompose the organic matter in the solder strip while avoiding oxidation of copper, tin and lead;

[0013] S2: Chlorination reaction: add a chlorinating agent to the thermally decomposed solder strip, wherein the chlorinating agent is ammonium chloride, and mix the solder strip and the chlorinating agent in a mass ratio of 1:1 to 2:1, and heat under low oxygen conditions (oxygen concentration ≤ 1ppm) for chlorination reaction, the temperature is set to 300℃-500℃, the protective gas is argon or nitrogen, and the reaction time is 0.5h-2h. After the chlorination reaction, the tin and lead in the solder strip are converted into volatile chlorides, while copper does not react with the chlorinating agent and remains in a solid state;

[0014] S3: volatilization and collection in stages: by gradually increasing the temperature, the reaction pressure is ≤0.5atm, the solder strip treated in step S2 is heated to 600°C-700°C to volatilize and collect tin chloride, and then further heated to 800°C-900°C to volatilize and collect lead chloride;

[0015] S4: copper separation: physically separating the non-volatile solid residue in the solder strip after the treatment in step S3 to obtain metallic copper;

[0016] Metal chloride treatment: The tin chloride and lead chloride collected in step S3 are recovered to obtain tin and lead metals.

[0017] Compared with the prior art, the present invention discloses a method for separating and recovering valuable metals in the welding strips of retired photovoltaic modules, which has the following advantages: high separation efficiency: through the technology of chlorination reaction and phased volatilization, the volatility characteristics of tin and lead are combined with the high melting point characteristics of copper, so as to realize the efficient separation of tin, lead and copper; low energy consumption and good environmental protection: the chlorination reaction is carried out in a low-oxygen environment, so as to avoid the oxidation of metals and the formation of complex oxides, reduce the difficulty of subsequent separation and the pollution to the environment, and the operating temperature of the whole process (300℃-500℃) is relatively low, so as to reduce energy consumption; the process is simple and has strong applicability: through temperature control and physical separation methods, the complex equipment requirements and multi-step processing procedures are reduced, so as to be suitable for industrial large-scale production; efficient resource recovery: through temperature control in a low-pressure environment, the chloride forms of tin and lead are volatilized and collected in stages at a relatively low temperature (600℃-900℃), and the copper is separated separately in a high-purity form, so that the metal finally recovered has high purity. The method of the present invention changes the complex multi-step chemical reaction in the prior art into a single chlorination reaction combined with a staged volatilization method, directly utilizes the low-temperature volatilization characteristics of metal chlorides to achieve efficient separation, avoids the complex problem of metal oxidation caused by aerobic pyrolysis, and makes the volatility difference between tin and lead the core separation point by accurately controlling the temperature gradient. Combined with low pressure or low oxygen conditions, the volatilization of metal chlorides is promoted and metal oxidation and impurity formation are minimized. The high energy consumption, complex process and environmental pollution problems mentioned in the background technology can be avoided, and the simplified process flow and environmentally friendly operation method of the present invention have been effectively solved, thereby significantly improving the industrial applicability.

[0018] In a possible implementation, the solder strip pretreatment includes: preparing retired photovoltaic modules, and mechanically disassembling them to separate solder strips, where the solder strips contain copper, tin, and lead.

[0019] Compared with the prior art, the above technical solution is used to pre-treat retired photovoltaic modules through a mechanical disassembly method, and the solder strips in the modules are separated from the glass, backplane, EVA film and other components. The pure solder strips obtained by separation contain a higher proportion of copper, tin and lead, which reduces the interference of non-metallic impurities, making the subsequent chlorination reaction more efficient and more selective, not only reducing the energy consumption of subsequent processes, but also avoiding the loss of valuable metals or the reduction of recovery rate due to impurity interference, and finally achieving efficient separation and recovery of valuable metals in the solder strips. This method directly solves the problems of impurity interference and low recovery efficiency mentioned in the background technology, and significantly improves the efficiency and environmental protection of the separation process.

[0020] In a possible implementation, in step S2, the chlorinating agent is ammonium chloride, and the mass ratio of the welding strip to the chlorinating agent is (1-2):1.

[0021] Compared with the prior art, the above technical solution adopts ammonium chloride (NH4Cl) as a chlorinating agent in the chlorination reaction, and the hydrogen chloride gas generated by its decomposition can react with tin and lead in the solder strip at a lower temperature to form tin chloride and lead chloride with a lower volatilization temperature. At the same time, copper metal remains in a solid state due to its chemical inertness and does not participate in the reaction. The mass ratio of the solder strip to the chlorinating agent is in the range of (1-2): 1, which ensures the sufficiency of the reaction and will not cause incomplete reaction due to too little chlorinating agent. Excess ammonium chloride is decomposed into hydrogen chloride and ammonia gas, which are easy to discharge, and will not increase the difficulty of separating other substances and subsequent metal chlorides due to excessive amount.

[0022] In a possible implementation manner, in step S2, the heating time for the chlorination reaction is 0.5h-2h.

[0023] Compared with the prior art, the above technical scheme optimizes the chlorination reaction time to 0.5h-2h, thereby solving the problems of low metal conversion rate, high impurities and high energy consumption often seen in the prior art. By controlling the time range, the generation and volatilization of tin chloride and lead chloride can reach an ideal state, which can ensure the full separation of metals without increasing the burden on equipment or wasting materials due to too long a time. The recovery efficiency and metal purity are significantly improved, while the recovery cost and environmental burden are reduced, providing a reliable guarantee for the industrial recovery of valuable metals in welding strips.

[0024] In a possible implementation, in step S2, the heating chlorination reaction is carried out in a low oxygen environment with an oxygen concentration of ≤1 ppm.

[0025] Compared with the prior art, the above technical solution avoids the oxidation problem of valuable metals in the soldering strip by carrying out the chlorination reaction in a vacuum or low-oxygen environment, effectively solving the shortcomings of the prior art of difficult separation, low efficiency and high cost of tin-lead alloy and tin-lead oxide. The vacuum or low-oxygen conditions can provide a better chemical environment for the reaction between the metal and the chlorinating agent, so that tin, lead and copper can be efficiently separated and recovered, while avoiding the separation complexity problem caused by the formation of metal oxides in traditional technologies, ultimately improving resource utilization efficiency and process economy.

[0026] In a possible implementation, in step S3, the purity of the metallic copper is ≥98%.

[0027] In a possible implementation, in step S3, the tin chloride and lead chloride are passed into a condenser after being collected, thereby obtaining solid tin chloride and lead chloride; in the actual operation process, the pressure and temperature are adjusted during the heating process to selectively volatilize tin chloride (SnCl2) and lead chloride (PbCl2). Since the volatilization temperature of tin chloride (SnCl2) is relatively low, about 600°C-700°C, it can be heated to this temperature range first, and the volatilized tin chloride will condense in the condensing device. Subsequently, the temperature continues to rise to 800°C-900°C to volatilize lead chloride (PbCl2). The volatilization temperature of lead chloride is relatively high, so a higher temperature is required to volatilize, but it is still lower than the melting point of copper, and the volatilized lead chloride will be collected at the farther end of the condensing device.

[0028] Compared with the prior art, the above technical solution is adopted and arranged in this way, by controlling the heating temperature, the condenser temperature zone and the low-pressure environment, the selective volatilization and condensation collection of tin chloride and lead chloride at a relatively low temperature is achieved, and the metal mixing problem caused by the overlapping volatilization temperatures in the traditional technology is avoided. The precise staged volatilization process and condensation strategy of the above implementation method enable tin chloride and lead chloride to be condensed into solids in different areas, thereby simplifying the subsequent processing steps, improving the resource utilization efficiency, and finally realizing environmentally friendly, economical and efficient metal separation and recovery.

[0029] In a possible implementation, in step S4, the recycling treatment condition is: reducing or distilling the collected tin chloride and lead chloride to obtain metallic tin and lead with a purity of ≥90%.

[0030] Compared with the prior art, the above technical solution can efficiently reduce the metal components in tin chloride and lead chloride to elemental tin and lead by selecting appropriate reducing agents or distillation conditions, while byproducts (such as HCl or ammonia) do not pollute metal chlorides, and environmental pollution is reduced by capturing and recycling. The low-temperature treatment conditions of the reduction method reduce energy consumption, while the distillation method uses the temperature difference characteristics to achieve the separation of volatile chlorides and metal purification. Compared with the prior art, it overcomes the waste liquid treatment problem in hydrometallurgy and the high cost problem of vacuum distillation process, and achieves the separation and recovery of tin and lead in a more environmentally friendly and efficient way, thereby improving the economy and sustainability of the entire process. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The pure copper is obtained by the waste photovoltaic welding strip after the chlorination reaction of the present invention and the recycling treatment;

[0032] Among them, the left picture shows the waste photovoltaic welding ribbon after chlorination reaction, and the right picture shows the pure copper obtained after separation. DETAILED DESCRIPTION

[0033] First, those skilled in the art should understand that these implementations are only used to explain the technical principles of the embodiments of the present application, and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0034] The present invention provides a method for separating and recovering valuable metals in welding strips of retired photovoltaic modules, comprising the following steps:

[0035] S1: Thermal decomposition: After pretreatment, the solder strip is placed in a low-oxygen environment for thermal decomposition to decompose the organic matter in the solder strip while avoiding oxidation of copper, tin and lead;

[0036] S2: Chlorination reaction: adding a chlorinating agent to the thermally decomposed solder strip, wherein the chlorinating agent is ammonium chloride, and the solder strip and the chlorinating agent are mixed in a mass ratio of 1:1 to 2:1, and heated at a temperature range of 300°C-500°C for chlorination reaction, so that the tin and lead in the solder strip are converted into volatile chlorides respectively;

[0037] S3: volatilization and collection in stages: by gradually increasing the temperature, the solder strip treated in step S2 is heated to 600°C-700°C to volatilize and collect tin chloride, and then further heated to 800°C-900°C to volatilize and collect lead chloride;

[0038] S4: copper separation: physically separating the non-volatile solid residue in the solder strip after the treatment in step S3 to obtain metallic copper;

[0039] Metal chloride treatment: The tin chloride and lead chloride collected in step S3 are recovered to obtain tin and lead metals.

[0040] The above method of the present invention, through chlorination reaction and temperature control, efficiently separates the tin-lead alloy and copper in the welding strip under a low-pressure and low-oxygen environment. The method has the advantages of good separation effect, low cost, environmental protection, etc., and realizes the selective volatilization and collection of tin chloride (SnCl2) and lead chloride (PbCl2) by different temperature control; Specifically, the efficient separation of tin-lead alloy and copper is realized by temperature control. Due to the difference in the volatilization temperature of tin and lead, tin chloride (SnCl2) and lead chloride (PbCl2) can be selectively volatilized by a staged heating method, thereby improving the separation efficiency. The method can separate tin and lead in the tin-lead alloy at a relatively low temperature, and collect metal chlorides by volatilization, thereby realizing the recycling of tin and lead. The reaction is carried out under a low-oxygen environment, which reduces the possibility of oxidation of the tin-lead alloy, and obtains relatively pure tin and lead metals. The above method of the present invention is simple to operate, suitable for large-scale production, and has relatively low cost and good environmental protection. By accurately controlling the pressure and heating temperature, the efficient separation of tin, lead and copper in the tin-lead alloy is realized, and they are collected separately according to their different volatilization temperatures. This method has low energy consumption, high separation rate, good recovery rate, and is suitable for large-scale production.

[0041] As a preferred solution, the solder strip pretreatment includes: preparing retired photovoltaic modules, and mechanically disassembling them to separate solder strips, where the solder strips contain copper, tin, and lead;

[0042] As a preferred solution, in step S2, the chlorinating agent is ammonium chloride, and the mass ratio of the welding strip to the chlorinating agent is (1-2):1.

[0043] As a preferred solution, in step S2, the heating time for the chlorination reaction is 0.5h-2h.

[0044] As a preferred solution, in step S2, the heating chlorination reaction is carried out in a low oxygen environment with an oxygen concentration of ≤1 ppm.

[0045] As a preferred solution, in step S3, the purity of the metallic copper is ≥98%.

[0046] As a preferred solution, in step S3, the reaction pressure is ≤0.5 atm, and the tin chloride and lead chloride are collected and passed into a condenser to obtain solid tin chloride and lead chloride.

[0047] As a preferred solution, in step S4, the recovery treatment condition is: reducing or distilling the collected tin chloride and lead chloride to obtain metallic tin and lead with a purity of ≥90%.

[0048] In combination with the above technical solution, an embodiment combined with specific data is provided below to further explain the above technical solution of the present invention:

[0049] Embodiment 1:

[0050] Step S1: Welding ribbon pretreatment

[0051] The retired photovoltaic modules are mechanically disassembled and the solder strips are separated. The solder strips contain valuable metal components such as copper, tin and lead. A 100-gram solder strip sample is placed in a ceramic crucible and subjected to thermal decomposition treatment in a low-oxygen environment (0.5ppm) to completely decompose the organic matter in the solder strip while avoiding metal oxidation. The processed waste photovoltaic solder strips are then collected.

[0052] Step S2: Chlorination reaction

[0053] The solder strip sample after thermal decomposition in step S1 is placed in a ceramic container, and 150 grams of ammonium chloride (NH4Cl) is added as a chlorinating agent to ensure that the mass ratio of the solder strip to the chlorinating agent is 1:1.5; the ceramic container is placed in a heating furnace, and heated in a vacuum environment of 0.8atm, the reaction temperature is controlled at 350°C, and the insulation time is 2 hours; during the chlorination reaction, tin (Sn) and lead (Pb) in the solder strip react with the chlorinating agent and are converted into tin chloride (SnCl2) and lead chloride (PbCl2) with lower volatilization temperatures, respectively, while copper remains in a solid state and does not react with ammonium chloride.

[0054] Step S3: Phased volatilization and collection

[0055] After the chlorination reaction, the collection process of volatiles is controlled by gradually increasing the temperature:

[0056] The vacuum degree in the heating furnace is adjusted to 0.3 atm, and the reaction temperature is adjusted to 650° C., so that tin chloride (SnCl2) is volatilized and condensed into a solid state through a condensation device, and solid tin chloride is collected;

[0057] The reaction temperature is then raised to 850°C to volatilize lead chloride (PbCl2) and condense through the cooling system of the condensation device to collect solid lead chloride. The condensation device is divided into multiple temperature control zones. The lower temperature zone is used to collect tin chloride, and the higher temperature zone is used to collect lead chloride. In actual operation, the volatilization temperature of lead chloride is relatively high, so a higher temperature is required for volatilization. The volatilized lead chloride will be collected at the farther end of the condensation device, while the tin chloride is at the closer end.

[0058] Step S4: Copper separation

[0059] After the volatilization is completed, the remaining solid residue is unreacted metallic copper, which is separated from the crucible by physical separation (filtration) and cleaned to finally obtain high-purity metallic copper with a purity of up to 98.5%.

[0060] Step S5: Metal chloride treatment

[0061] The solid tin chloride (SnCl2) and lead chloride (PbCl2) collected in step S3 are further recovered after being treated with high-purity carbon powder through reduction reaction. Through the reduction reaction, the tin chloride and lead chloride are reduced to metallic tin and metallic lead, and the obtained metal purities are 92.6% and 92.8%, thereby achieving efficient recovery of tin and lead.

[0062] Embodiment 2:

[0063] Step S1: Welding ribbon pretreatment

[0064] The retired photovoltaic modules are mechanically disassembled and the solder strips are separated. The solder strips contain valuable metal components such as copper, tin and lead. A 100-gram solder strip sample is placed in a ceramic crucible and subjected to thermal decomposition treatment in a low-oxygen environment (0.5ppm) to completely decompose the organic matter in the solder strip while avoiding metal oxidation. The processed waste photovoltaic solder strips are then collected.

[0065] Step S2: Chlorination reaction

[0066] The solder strip sample after thermal decomposition in step S1 is placed in a ceramic container, and 100 grams of ammonium chloride (NH4Cl) is added as a chlorinating agent to ensure that the mass ratio of the solder strip to the chlorinating agent is 1:1; the ceramic container is placed in a heating furnace and heated in an environment with an oxygen content of 0.5%, the reaction temperature is controlled at 450°C, and the insulation time is 0.5 hours; during the chlorination reaction, tin (Sn) and lead (Pb) in the solder strip react with the chlorinating agent and are converted into tin chloride (SnCl2) and lead chloride (PbCl2) with lower volatilization temperatures, respectively, while copper remains in a solid state and does not react.

[0067] Step S3: Phased volatilization and collection

[0068] After the chlorination reaction, the collection process of volatiles is controlled by gradually increasing the temperature:

[0069] The vacuum degree in the heating furnace is adjusted to 0.2 atm, and the reaction temperature is adjusted to 650° C., so that tin chloride (SnCl2) is volatilized and condensed into a solid state through a condensation device, and solid tin chloride is collected;

[0070] The reaction temperature is then raised to 900°C to volatilize lead chloride (PbCl2) and condense through the cooling system of the condensation device to collect solid lead chloride. The condensation device is divided into multiple temperature control zones. The lower temperature zone is used to collect tin chloride, and the higher temperature zone is used to collect lead chloride. In actual operation, the volatilization temperature of lead chloride is relatively high, so a higher temperature is required for volatilization. The volatilized lead chloride will be collected at the farther end of the condensation device, while the tin chloride is at the closer end.

[0071] Step S4: Copper separation

[0072] After the volatilization is completed, the remaining solid residue is unreacted metallic copper, which is separated from the crucible by physical separation (filtration) and cleaned to finally obtain high-purity metallic copper with a purity of up to 98.5%.

[0073] Step S5: Metal chloride treatment

[0074] The solid tin chloride (SnCl2) and lead chloride (PbCl2) collected in step S3 are further recovered after being treated with high-purity carbon powder through reduction reaction. Through the reduction reaction, the tin chloride and lead chloride are reduced to metallic tin and metallic lead, and the obtained metal purity is 92.0% and 92.1%, thereby achieving efficient recovery of tin and lead.

[0075] Embodiment 3:

[0076] Step S1: Welding ribbon pretreatment

[0077] The retired photovoltaic modules are mechanically disassembled and the solder strips are separated. The solder strips contain valuable metal components such as copper, tin and lead. A 100-gram solder strip sample is placed in a ceramic crucible and subjected to thermal decomposition treatment in a low-oxygen environment (0.3ppm) to completely decompose the organic matter in the solder strip while avoiding metal oxidation. The processed waste photovoltaic solder strips are then collected.

[0078] Step S2: Chlorination reaction

[0079] The solder strip sample after thermal decomposition in step S1 is placed in a ceramic container, and 200 grams of ammonium chloride (NH4Cl) is added as a chlorinating agent to ensure that the mass ratio of the solder strip to the chlorinating agent is 1:2; the ceramic container is placed in a heating furnace, and heated in an environment with an oxygen content of 0.8%, the reaction temperature is controlled at 300°C, and the insulation time is 2 hours; during the chlorination reaction, tin (Sn) and lead (Pb) in the solder strip react with the chlorinating agent and are converted into tin chloride (SnCl2) and lead chloride (PbCl2) with lower volatilization temperatures, respectively, while copper remains in a solid state and does not react.

[0080] Step S3: Phased volatilization and collection

[0081] After the chlorination reaction, the collection process of volatiles is controlled by gradually increasing the temperature:

[0082] The vacuum degree in the heating furnace is adjusted to 0.1 atm, and the reaction temperature is adjusted to 700° C., so that tin chloride (SnCl2) is volatilized and condensed into a solid state through a condensation device, and solid tin chloride is collected;

[0083] The reaction temperature is then raised to 850°C to volatilize lead chloride (PbCl2) and condense through the cooling system of the condensation device to collect solid lead chloride. The condensation device is divided into multiple temperature control zones. The lower temperature zone is used to collect tin chloride, and the higher temperature zone is used to collect lead chloride. In actual operation, the volatilization temperature of lead chloride is relatively high, so a higher temperature is required for volatilization. The volatilized lead chloride will be collected at the farther end of the condensation device, while the tin chloride is at the closer end.

[0084] Step S4: Copper separation

[0085] After the volatilization is completed, the remaining solid residue is unreacted metallic copper, which is separated from the crucible by physical separation (filtration) and cleaned to finally obtain high-purity metallic copper with a purity of up to 98.6%.

[0086] Step S5: Metal chloride treatment

[0087] The solid tin chloride (SnCl2) and lead chloride (PbCl2) collected in step S3 are respectively introduced into hydrogen for reduction reaction treatment process for further recovery. Through the reduction reaction, the tin chloride and lead chloride are reduced to metallic tin and metallic lead, and the obtained metal purities are 93.0% and 92.6%, respectively, thereby achieving efficient recovery of tin and lead.

[0088] like Figure 1 As shown, Figure 1 The waste photovoltaic welding strip after chlorination reaction and the pure copper obtained after separation treatment in the separation and recovery method of Example 1; the left picture is the waste photovoltaic welding strip after chlorination reaction, and the right picture is the pure copper obtained after separation. Figure 1 It can be seen that the pure copper obtained by the method of the present invention has high purity and good surface gloss.

[0089] Through the above embodiments, the technical principles adopted by the method of the present invention and its advantages over the prior art can be further demonstrated. The method of the present invention solves the following technical problems existing in the photovoltaic ribbon recycling process in the prior art through an optimized chlorination reaction process and a precise temperature control system:

[0090] Avoid the formation of metal oxides and simplify the separation difficulty: Compared with the method that relies on aerobic pyrolysis in the background technology, the present invention successfully avoids the oxidation of metal components in the solder strip by performing thermal decomposition and chlorination reaction in a low-oxygen environment, thereby reducing the difficulty of separating metal oxides. In a low-pressure environment combined with a staged temperature rise volatilization process, the method of the present invention can achieve efficient separation of metal tin and lead at a lower temperature, significantly improving the recovery efficiency.

[0091] Reduce energy consumption and improve metal purity: Compared with some methods in the prior art, vacuum distillation operations at temperatures above 1300°C are required, resulting in high energy consumption and complex equipment. The present invention precisely controls the volatility characteristics of tin and lead chlorides to separate tin chloride and lead chloride within the temperature ranges of 600°C-700°C and 800°C-900°C, respectively, which not only reduces energy consumption but also reduces dependence on high vacuum equipment. At the same time, the method of the present invention successfully recovers metallic tin and lead with a purity of ≥90% through subsequent reduction treatment, and the recovery efficiency and product quality are higher than the existing process.

[0092] Reduce potential threats to the environment: Chemical reagents such as strong acids and alkalis used in the background technology may cause waste liquid discharge problems. The present invention uses only ammonium chloride as a chlorinating agent, and through precise process design, the volatilized chloride is directly collected and solidified through a condensation device, thereby avoiding the generation of waste liquid. The process is safe to operate, environmentally friendly, and has strong sustainability.

[0093] Operability suitable for large-scale production: The method of the present invention adopts simple and easy process steps, including thermal decomposition, chlorination reaction, staged volatilization and reduction treatment of metal chlorides, which can significantly reduce production costs and equipment complexity. The combination of staged heating and condensation devices ensures efficient separation of various metals, simplifies the operation process, and is particularly suitable for industrial large-scale production.

[0094] In summary, the present invention provides an efficient, environmentally friendly, low-energy photovoltaic ribbon recycling method, which overcomes the defects of high complexity, high energy consumption and high pollution risk in the prior art, not only improves the recycling efficiency, but also provides a new solution for the resource utilization of photovoltaic components, with significant economic and social benefits.

[0095] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0096] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for separating and recovering valuable metals in retired photovoltaic module welding strips, characterized in that: The following steps are involved: S1: Thermal decomposition: After pre-treatment, the solder strip is placed in a vacuum or low-oxygen environment for thermal decomposition to decompose the organic matter in the solder strip while avoiding oxidation of copper, tin and lead; S2: Chlorination reaction: adding a chlorinating agent to the thermally decomposed solder strip, wherein the chlorinating agent is ammonium chloride, and the solder strip and the chlorinating agent are mixed in a mass ratio of 1:1 to 2:1, and heated at a temperature range of 300°C-500°C for chlorination reaction, so that the tin and lead in the solder strip are converted into chloride and volatile gas with lower volatilization temperature respectively; S3: volatilization and collection in stages: by gradually increasing the temperature, the solder strip treated in step S2 is heated to 600°C-700°C to volatilize and collect tin chloride, and then further heated to 800°C-900°C to volatilize and collect lead chloride; S4: copper separation: physically separating the non-volatile solid residue in the solder strip after the treatment in step S3 to obtain metallic copper; Metal chloride treatment: The tin chloride and lead chloride collected in step S3 are recovered to obtain tin and lead metals.

2. The method for separating and recovering valuable metals in retired photovoltaic module welding strips according to claim 1, characterized in that: The solder strip pretreatment includes: preparing retired photovoltaic modules, and mechanically disassembling them to separate solder strips, which contain copper, tin and lead.

3. The method for separating and recovering valuable metals in retired photovoltaic module welding strips according to claim 1, characterized in that: In step S2, the chlorinating agent is ammonium chloride, and the mass ratio of the welding strip to the chlorinating agent is (1-2):

1.

4. The method for separating and recovering valuable metals in retired photovoltaic module welding strips according to claim 1, characterized in that: In step S2, the heating time for chlorination reaction is 0.5h-2h.

5. The method for separating and recovering valuable metals in retired photovoltaic module welding strips according to claim 1, characterized in that: In the steps S2 and S3, the heating for chlorination reaction and volatilization reaction is carried out in a low oxygen environment with an oxygen concentration of ≤1 ppm.

6. The method for separating and recovering valuable metals in retired photovoltaic module welding strips according to claim 1, characterized in that: In the step S3, the purity of the metallic copper is ≥98%.

7. The method for separating and recovering valuable metals in retired photovoltaic module welding strips according to claim 1, characterized in that: In the step S3, the tin chloride and lead chloride are collected and then passed into a condenser to obtain solid tin chloride and lead chloride.

8. The method for separating and recovering valuable metals in retired photovoltaic module welding strips according to claim 1, characterized in that: In step S4, the recycling treatment condition is: reducing or distilling the collected tin chloride and lead chloride to obtain metallic tin and lead with a purity of ≥90%.

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