A closed-loop method for recycling valuable metals in waste photovoltaic modules

Abstract

The present invention relates to a closed-loop method for recovering valuable metals in waste photovoltaic modules, and belongs to the technical field of waste photovoltaic module recycling. The present invention places waste photovoltaic welding strips in an inert atmosphere, heats to a temperature of 400-500°C and keeps the temperature, melts the tin-lead solder on the surface of the waste photovoltaic welding strips, and captures the silver on the surface of the tin-lead solder to form a silver-containing tin-lead melt A, while the internal copper does not melt to maintain a solid phase, and solid-liquid separation is performed to obtain a silver-containing tin-lead melt A and solid-phase copper; waste photovoltaic silicon cell powder is added to the silver-containing tin-lead melt A, heated and stirred in an inert atmosphere to capture silver by tin-lead to form a silver-containing tin-lead melt B, and solid-liquid separation is performed to obtain a silver-containing tin-lead melt B and solid-phase silicon and aluminum; metal zinc is added to the silver-containing tin-lead melt B for elution, and solid-liquid separation is performed to obtain a silver-zinc alloy and a tin-lead melt; the silver-zinc melt and the tin-lead melt are respectively subjected to vacuum distillation separation to obtain residual metallic silver, residual metallic tin, condensed product metallic zinc, and condensed product metallic lead.

Description

Technical Field

[0001] The invention relates to a closed-loop method for recovering valuable metals in waste photovoltaic modules, belonging to the technical field of recycling waste photovoltaic modules. Background Art

[0002] The silicon cells and solder ribbons in discarded silicon photovoltaic modules contain valuable metals such as silicon, silver, copper, tin and aluminum. Recycling the valuable metals in these discarded silicon photovoltaic modules can reduce resource waste and extend the life cycle of resource utilization.

[0003] At present, the valuable metals in waste photovoltaic modules are mainly extracted through hydrometallurgical processes. This process mainly includes leaching (using acid, alkali or other chemical solvents to dissolve metal ions from solids), precipitation (using acid, alkali and salt to precipitate metal ions), reduction (using reducing chemical reagents), electrolysis / electrodeposition (using electrolytes) and other processes, which are used to achieve the recovery of metals such as silicon, silver, copper, tin, aluminum and lead in waste photovoltaic modules one by one. Although these complex and fine hydrometallurgical steps can effectively extract valuable metals, many acid and alkaline solutions or electrolytes are used in the processes of leaching, precipitation, reduction and electrolysis, resulting in an increase in the types and volumes of waste liquid discharged. This not only increases the difficulty and cost of waste liquid treatment, but also poses potential hazards to the environment. Therefore, there is an urgent need to develop a new green method that does not use any chemical reagents to achieve closed-loop recovery of valuable metals in waste photovoltaic modules. Summary of the invention

[0004] In view of the dual challenges of environmental risks and economic benefits in the recovery of valuable metals from discarded photovoltaic modules in the prior art, the present invention proposes a closed-loop method for recovering valuable metals from discarded photovoltaic modules. According to the Cu-Sn-Pb-Ag isothermal phase diagram, a specific heating temperature (400-500°C) is set to separate the copper inside the discarded photovoltaic ribbon from the tin-lead solder on the surface to obtain metallic copper and a tin-lead-silver alloy melt; then, the tin-lead solder in the discarded photovoltaic ribbon is used as a capture agent to capture the silver in the discarded photovoltaic silicon cell to obtain a silver-tin-lead melt, and the silver-tin-lead melt is separated from solid silicon and aluminum according to the density difference; then, metallic zinc is added to the silver-tin-lead melt to precipitate silver to obtain a silver-zinc alloy and a tin-lead melt; finally, the silver-zinc alloy and the tin-lead melt are separated by vacuum distillation technology to obtain metallic silver, zinc, tin and lead, and the zinc can be recycled. The present invention realizes the coordinated recovery of valuable metals in welding strips and silicon cells in discarded photovoltaic modules without using any chemical reagents, and realizes the closed-loop recycling of valuable metals in discarded photovoltaic modules, thereby achieving the purpose of green, economical and sustainable recovery of discarded photovoltaic modules.

[0005] A closed-loop method for recycling valuable metals in waste photovoltaic modules, the specific steps are as follows:

[0006] (1) placing the waste photovoltaic ribbon in an inert atmosphere and heating it to a temperature of 400-500°C and keeping it warm, so that the tin-lead solder on the surface of the waste photovoltaic ribbon is melted and the silver on the surface of the tin-lead solder is captured to form a silver-containing tin-lead melt A, while the internal copper does not melt and maintains a solid phase, and the solid-liquid separation is performed to obtain the silver-containing tin-lead melt A and solid phase copper;

[0007] (2) Waste photovoltaic silicon cell pieces are mechanically crushed and ground to obtain waste photovoltaic silicon cell piece powder;

[0008] (3) adding the waste photovoltaic silicon cell powder to the silver-containing tin-lead melt A, heating and stirring in an inert atmosphere to allow the tin-lead to capture the silver to form the silver-containing tin-lead melt B, and performing solid-liquid separation to obtain the silver-containing tin-lead melt B and solid phase silicon and aluminum;

[0009] (4) adding metallic zinc to the silver-containing tin-lead melt B and heating it to completely dissolve the zinc, then cooling it to melt it out to obtain a silver-zinc alloy, and performing solid-liquid separation to obtain a silver-zinc alloy and a tin-lead melt;

[0010] (5) heating the silver-zinc alloy in a vacuum to melt it to obtain a silver-zinc melt, and subjecting the silver-zinc melt to vacuum distillation to separate residual metallic silver and condensed metallic zinc, which is then returned to step (4) for recycling;

[0011] (6) The tin-lead melt is heated under vacuum conditions and vacuum distilled to separate the residual metallic tin and the condensed product lead.

[0012] The average particle size of the waste photovoltaic silicon cell powder in step (2) is 0.053-0.074 mm.

[0013] In the step (3), the mass ratio of the silver-containing tin-lead melt A to the waste photovoltaic silicon cell powder is 2-3:1, and the temperature at which the tin-lead captures the silver is 450-550°C.

[0014] In the step (4), the amount of metallic zinc added is 40-50 wt.% of the tin-lead melt B, and the cooling and melting temperature is 390-430°C.

[0015] In the step (5), the temperature of the vacuum distillation of the silver-zinc alloy is 600-800° C., the vacuum degree is 50-100 Pa, and the vacuum distillation time is 30-40 min.

[0016] In the step (6), the temperature of the vacuum distillation of the tin-lead alloy is 900-1100° C., the vacuum degree is 10-20 Pa, and the vacuum distillation time is 20-30 min.

[0017] The beneficial effects of the present invention are:

[0018] (1) The closed-loop recycling method of the present invention realizes the effective separation and purification of valuable metals in waste photovoltaic modules, avoiding the pollution problems that may be caused by traditional chemical methods;

[0019] (2) All process steps of the present invention are carried out through physical separation rather than chemical treatment, thus achieving green recovery of valuable metals and promoting the recycling of resources;

[0020] (3) The closed-loop recycling method of the present invention reduces the demand for external raw materials and the consumption of chemical reagents, reduces recycling costs, and improves economic benefits. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with specific implementation modes, but the protection scope of the present invention is not limited to the described contents.

[0022] Example 1: A closed-loop method for recovering valuable metals from discarded photovoltaic modules, the specific steps are as follows:

[0023] (1) The waste photovoltaic welding ribbon is placed in an inert (argon) atmosphere and heated to a temperature of 500°C and kept warm, so that the tin-lead solder on the surface of the waste photovoltaic welding ribbon is melted and the silver on the surface of the tin-lead solder is captured to form a silver-containing tin-lead melt A, while the internal copper does not melt and maintains a solid phase, and the silver-containing tin-lead melt A and solid phase copper are obtained by solid-liquid separation by siphon method; in terms of mass percentage, Ag accounts for 18.9wt.%, Sn accounts for 52.5wt.%, Pb accounts for 27.6wt.%, and Cu accounts for 1.0wt.%, and the capture rate of silver is 99.9wt.%; the purity of the solid phase copper is 99.8wt.wt.%;

[0024] (2) The waste photovoltaic silicon cell pieces are mechanically crushed and ground to obtain waste photovoltaic silicon cell piece powder with a particle size of 0.061-0.074 mm;

[0025] (3) Adding the waste photovoltaic silicon cell powder into the silver-containing tin-lead melt A, heating to 550°C in an inert (argon) atmosphere and stirring (ultrasonic stirring) for 60 minutes to form a silver-containing tin-lead melt B, and obtaining the silver-containing tin-lead melt B and a solid phase silicon and aluminum mixture by solid-liquid separation through skimming method; under the condition that the mass ratio of the silver-containing tin-lead melt A to the waste photovoltaic silicon cell powder is 2:1, the silver-containing tin-lead melt is continuously used for silver capture of 10 batches of waste photovoltaic silicon cell powder. In terms of mass percentage, in the silver-containing tin-lead melt B, Ag accounts for 23.1wt.%, Sn accounts for 50.3wt.%, Pb accounts for 25.7wt.%, Cu accounts for 0.9wt.%, and the silver capture rate is 99.4wt.%;

[0026] (4) adding metallic zinc (purity 99.9%) to the silver-containing tin-lead melt B (the amount of metallic zinc added is 50wt.% of the tin-lead melt B), and heating to 700°C to completely dissolve the zinc, then cooling to 410°C for smelting to obtain a silver-zinc alloy, and filtering and separating to obtain the silver-zinc alloy and the tin-lead melt; in this embodiment, the silver content of the silver-zinc alloy is 31.9wt.%, the zinc content is 67.7wt.%, and the tin content of the tin-lead melt is 64.9wt.%, the lead content is 31.8wt.%, and the zinc content is 3.1wt.%;

[0027] (5) heating and melting the silver-zinc alloy under vacuum conditions, and performing vacuum distillation separation for 30 minutes at a temperature of 800° C. and a vacuum degree of 50 Pa to obtain metallic silver and a condensed product metallic zinc; the metallic zinc is returned to step (4) for recycling;

[0028] (6) vacuum heating the tin-lead melt, and performing vacuum distillation separation for 30 minutes at a temperature of 1100° C. and a vacuum degree of 10 Pa to obtain metallic tin and a condensed product metallic lead;

[0029] In this embodiment, the purity of metallic silver is 99.8 wt.%, the purity of metallic tin is 99.7 wt.%, the purity of metallic lead is 99.6 wt.%, and the purity of metallic zinc is 99.8 wt.%.

[0030] Example 2: A closed-loop method for recovering valuable metals from discarded photovoltaic modules, the specific steps are as follows:

[0031] (1) The waste photovoltaic welding ribbon is placed in an inert (argon) atmosphere and heated to a temperature of 400°C and kept warm, so that the tin-lead solder on the surface of the waste photovoltaic welding ribbon is melted and the silver on the surface of the tin-lead solder is captured to form a silver-containing tin-lead melt A, while the internal copper does not melt and maintains a solid phase, and the silver-containing tin-lead melt A and solid phase copper are obtained by solid-liquid separation by siphon method; in terms of mass percentage, Ag accounts for 19.1wt.%, Sn accounts for 52.6wt.%, Pb accounts for 27.7wt.%, Cu accounts for 0.6wt.%, and the silver capture rate is 99.8wt.%; the purity of the solid phase copper is 99.4wt.%;

[0032] (2) The waste photovoltaic silicon cell pieces are mechanically crushed and ground to obtain waste photovoltaic silicon cell piece powder with a particle size of 0.061-0.074 mm;

[0033] (3) Adding the waste photovoltaic silicon cell powder into the silver-containing tin-lead melt A, heating to 530°C in an inert (argon) atmosphere and stirring (gas stirring) to perform tin-lead capture of silver for 30 minutes to form a silver-containing tin-lead melt B, and performing solid-liquid separation by skimming to obtain the silver-containing tin-lead melt A and a solid phase silicon and aluminum mixture; under the condition that the mass ratio of the silver-containing tin-lead melt A to the waste photovoltaic silicon cell powder is 2:1, the silver-containing tin-lead melt is continuously used to capture the silver of 10 batches of waste photovoltaic silicon cell powder. In terms of mass percentage, in the silver-containing tin-lead melt B, Ag accounts for 22.3wt.%, Sn accounts for 50.8wt.%, Pb accounts for 26.5wt.%, Cu accounts for 0.4wt.%, and the silver capture rate is 99.3wt.%;

[0034] (4) adding metallic zinc (99.9 wt.%) to the silver-containing tin-lead melt B (the amount of metallic zinc added is 55 wt.% of the tin-lead melt B), and heating to 700°C to completely dissolve the zinc, then cooling to 390°C for smelting to obtain a silver-zinc alloy, and performing solid-liquid separation to obtain a silver-zinc alloy and a tin-lead melt; in this embodiment, the silver content of the silver-zinc alloy is 28.7 wt.%, and the zinc content is 70.8 wt.%, and the tin content of the tin-lead melt is 68.6 wt.%, the lead content is 27.5 wt.%, and the zinc content is 3.6 wt.%;

[0035] (5) heating and melting the silver-zinc alloy under vacuum conditions, and performing vacuum distillation separation for 40 min at a temperature of 600° C. and a vacuum degree of 100 Pa to obtain metallic silver and a condensed product metallic zinc, which is returned to step (4) for recycling;

[0036] (6) heating the tin-lead melt under vacuum conditions, and performing vacuum distillation separation at a temperature of 900° C. and a vacuum degree of 20 Pa for 30 minutes to obtain metallic tin and a condensed product metallic lead;

[0037] In this embodiment, the purity of metallic silver is 99.1wt.%, the purity of metallic tin is 99.4wt.%, the purity of metallic lead is 99.7wt.%, and the purity of metallic zinc is 99.9wt.%.

[0038] Example 3: A closed-loop method for recovering valuable metals from discarded photovoltaic modules, the specific steps are as follows:

[0039] (1) The waste photovoltaic welding ribbon is placed in an inert (helium) atmosphere and heated to a temperature of 450°C and kept warm, so that the tin-lead solder on the surface of the waste photovoltaic welding ribbon is melted and the silver on the surface of the tin-lead solder is captured to form a silver-containing tin-lead melt A, while the internal copper does not melt and maintains a solid phase, and the silver-containing tin-lead melt A and solid phase copper are obtained by solid-liquid separation by siphon method; in terms of mass percentage, Ag accounts for 19.0wt.%, Sn accounts for 52.6wt.%, Pb accounts for 27.7wt.%, and Cu accounts for 0.7wt.%, and the capture rate of silver is 99.5wt.%; the purity of the solid phase copper is 99.7wt.%;

[0040] (2) The waste photovoltaic silicon cell pieces are mechanically crushed and ground to obtain waste photovoltaic silicon cell piece powder with a particle size of 0.053-0.061 mm;

[0041] (3) Adding the waste photovoltaic silicon cell powder into the silver-containing tin-lead melt A, heating to 450°C in an inert (helium) atmosphere and stirring (electromagnetic stirring) for 60 minutes to form a silver-containing tin-lead melt B, and obtaining the silver-containing tin-lead melt A and a solid phase silicon and aluminum mixture by solid-liquid separation through skimming method; under the condition that the mass ratio of the silver-containing tin-lead melt A to the waste photovoltaic silicon cell powder is 3:1, the silver-containing tin-lead melt is continuously used for silver capture of 12 batches of waste photovoltaic silicon cell powder. In terms of mass percentage, in the silver-containing tin-lead melt B, Ag accounts for 21.7wt.%, Sn accounts for 51.7wt.%, Pb accounts for 25.9wt.%, Cu accounts for 0.7wt.%, and the silver capture rate is 99.1wt.%;

[0042] (4) adding metallic zinc (99.9 wt.%) to the silver-containing tin-lead melt B (the amount of metallic zinc added is 45 wt.% of the tin-lead melt B), and heating to 700°C to completely dissolve the zinc, then cooling to 430°C for smelting to obtain a silver-zinc alloy, and performing solid-liquid separation to obtain a silver-zinc alloy and a tin-lead melt; in this embodiment, the silver content of the silver-zinc alloy is 32.5 wt.%, the zinc content is 67.0 wt.%, and the tin content of the tin-lead melt is 66.3 wt.%, the lead content is 29.4 wt.%, and the zinc content is 3.9 wt.%;

[0043] (5) heating and melting the silver-zinc alloy under vacuum conditions, and performing vacuum distillation separation for 40 min at a temperature of 700° C. and a vacuum degree of 70 Pa to obtain metallic silver and a condensed product metallic zinc, which is returned to step (4) for recycling;

[0044] (6) heating the tin-lead melt under vacuum conditions, and performing vacuum distillation separation for 20 minutes at a temperature of 1000° C. and a vacuum degree of 15 Pa to obtain metallic tin and a condensed product metallic lead;

[0045] In this embodiment, the purity of metallic silver is 99.5wt.%, the purity of metallic tin is 99.6wt.%, the purity of metallic lead is 99.6wt.%, and the purity of metallic zinc is 99.7wt.%.

[0046] Example 4: A closed-loop method for recovering valuable metals from discarded photovoltaic modules, the specific steps are as follows:

[0047] (1) The waste photovoltaic welding ribbon is placed in an inert (argon) atmosphere and heated to a temperature of 500°C and kept warm, so that the tin-lead solder on the surface of the waste photovoltaic welding ribbon is melted and the silver on the surface of the tin-lead solder is captured to form a silver-containing tin-lead melt A, while the internal copper does not melt and maintains a solid phase, and the silver-containing tin-lead melt A and solid phase copper are obtained by solid-liquid separation by siphon method; in terms of mass percentage, Ag accounts for 19.1wt.%, Sn accounts for 52.4wt.%, Pb accounts for 27.6wt.%, Cu accounts for 0.9wt.%, and the silver capture rate is 99.8wt.%; the purity of the solid phase copper is 99.7wt.wt.;

[0048] (2) The waste photovoltaic silicon cell pieces are mechanically crushed and ground to obtain waste photovoltaic silicon cell piece powder with a particle size of 0.061-0.074 mm;

[0049] (3) Adding the waste photovoltaic silicon cell powder into the silver-containing tin-lead melt A, heating to a temperature of 550°C in an inert (argon) atmosphere and stirring (electromagnetic stirring) for 60 minutes to form a silver-containing tin-lead melt B, and obtaining the silver-containing tin-lead melt A and a solid phase silicon and aluminum mixture by solid-liquid separation through skimming method; under the condition that the mass ratio of the silver-containing tin-lead melt A to the waste photovoltaic silicon cell powder is 3:1, the silver-containing tin-lead melt is continuously used for silver capture of 12 batches of waste photovoltaic silicon cell powder. In terms of mass percentage, in the silver-containing tin-lead melt B, Ag accounts for 21.9wt.%, Sn accounts for 52.0wt.%, Pb accounts for 25.2wt.%, Cu accounts for 0.9wt.%, and the silver capture rate is 99.9wt.%;

[0050] (4) adding metallic zinc (99.9 wt.%) to the silver-containing tin-lead melt B (the amount of metallic zinc added is 50 wt.% of the tin-lead melt B), and heating to 700°C to completely dissolve the zinc, then cooling to 410°C for smelting to obtain a silver-zinc alloy, and filtering and separating to obtain the silver-zinc alloy and the tin-lead melt; in this embodiment, the silver content of the silver-zinc alloy is 30.5 wt.%, the zinc content is 68.9 wt.%, and the tin content of the tin-lead melt is 67.3 wt.%, the lead content is 29.0 wt.%, and the zinc content is 3.5 wt.%;

[0051] (5) heating and melting the silver-zinc alloy under vacuum conditions, and performing vacuum distillation separation for 40 min at a temperature of 800° C. and a vacuum degree of 60 Pa to obtain metallic silver and a condensed product metallic zinc, which is returned to step (4) for recycling;

[0052] (6) heating the tin-lead melt under vacuum conditions, and performing vacuum distillation separation for 30 minutes at a temperature of 1100° C. and a vacuum degree of 20 Pa to obtain metallic tin and a condensed product metallic lead;

[0053] In this embodiment, the purity of metallic silver is 99.7wt.%, the purity of metallic tin is 99.6wt.%, the purity of metallic lead is 99.5wt.%, and the purity of metallic zinc is 99.5wt.%.

[0054] The specific implementation modes of the present invention are described in detail above, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A closed-loop method for recovering valuable metals from discarded photovoltaic modules, characterized in that: The specific steps are as follows: (1) placing the waste photovoltaic ribbon in an inert atmosphere and heating it to a temperature of 400-500°C and keeping it warm, so that the tin-lead solder on the surface of the waste photovoltaic ribbon is melted and the silver on the surface of the tin-lead solder is captured to form a silver-containing tin-lead melt A, while the internal copper does not melt and maintains a solid phase, and the solid-liquid separation is performed to obtain the silver-containing tin-lead melt A and solid phase copper; (2) Waste photovoltaic silicon cell pieces are mechanically crushed and ground to obtain waste photovoltaic silicon cell piece powder; (3) adding the waste photovoltaic silicon cell powder to the silver-containing tin-lead melt A, heating and stirring in an inert atmosphere to allow the tin-lead to capture the silver to form the silver-containing tin-lead melt B, and performing solid-liquid separation to obtain the silver-containing tin-lead melt B and solid phase silicon and aluminum; (4) adding metallic zinc to the silver-containing tin-lead melt B and heating it to completely dissolve the zinc, then cooling it to melt it out to obtain a silver-zinc alloy, and performing solid-liquid separation to obtain a silver-zinc alloy and a tin-lead melt; (5) heating the silver-zinc alloy in a vacuum to melt it to obtain a silver-zinc melt, and subjecting the silver-zinc melt to vacuum distillation to separate residual metallic silver and condensed metallic zinc, which is then returned to step (4) for recycling; (6) The tin-lead melt is heated under vacuum conditions and vacuum distilled to separate the residual metallic tin and the condensed product metallic lead.

2. The closed-loop method for recovering valuable metals from discarded photovoltaic modules according to claim 1, characterized in that: The average particle size of the waste photovoltaic silicon cell powder in step (2) is 0.053-0.074 mm.

3. The closed-loop method for recovering valuable metals from discarded photovoltaic modules according to claim 1, characterized in that: In step (3), the mass ratio of the silver-containing tin-lead melt A to the waste photovoltaic silicon cell powder is 2-3:1, and the temperature at which the tin-lead captures the silver is 450-550°C.

4. The closed-loop method for recovering valuable metals from discarded photovoltaic modules according to claim 1, characterized in that: In step (4), the amount of metallic zinc added is 40-50 wt.% of the tin-lead melt B, and the cooling and melting temperature is 390-430°C.

5. The closed-loop method for recovering valuable metals from discarded photovoltaic modules according to claim 1, characterized in that: In step (5), the temperature of the silver-zinc alloy vacuum distillation is 600-800° C., the vacuum degree is 50-100 Pa, and the vacuum distillation time is 30-40 min.

6. The closed-loop method for recovering valuable metals from waste photovoltaic modules according to claim 1, characterized in that: In step (6), the temperature of vacuum distillation of tin-lead alloy is 900-1100° C., the vacuum degree is 10-20 Pa, and the vacuum distillation time is 20-30 min.