Method for step-by-step separation of valuable metals Ag, Si and Al from decommissioned photovoltaic cells
By using a zinc metal trap and vacuum gasification technology, silver and aluminum in photovoltaic cells are separated in stages, solving the problems of low recovery rate and serious environmental pollution in existing technologies. This achieves efficient and clean silver and aluminum recovery, which is suitable for large-scale production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- KUNMING UNIV OF SCI & TECH
- Filing Date
- 2026-03-13
- Publication Date
- 2026-06-09
Smart Images
Figure CN122168903A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for separating valuable metals Ag, Si, and Al from decommissioned photovoltaic cells in stages, belonging to the field of photovoltaic solid waste recycling technology. Background Technology
[0002] Photovoltaic cells typically contain valuable components such as silicon, silver, and aluminum. Since silver is usually tightly bonded to aluminum electrodes in cells and embedded in the silicon matrix in the form of fine particles, its efficient separation and recycling face technical challenges.
[0003] Currently, the main method for recovering silver and aluminum from photovoltaic cells is through hydrometallurgical processes. However, hydrometallurgical recovery involves reagents such as strong acids, strong alkalis, or cyanides, which are highly toxic and prone to causing secondary pollution. Furthermore, the silver and aluminum separation steps are complex, and the recovery rate is limited. In existing processes, the trapping agents or additives are often not recyclable, increasing treatment costs and environmental burden. Therefore, developing a clean, efficient, and low-cost silver and aluminum separation and recovery process to achieve high-value utilization of silver and recycling of key reagents is of great significance for promoting the resource utilization of photovoltaic solid waste and fostering the sustainable development of the photovoltaic industry. Summary of the Invention
[0004] To address the problems of long process times and severe environmental pollution associated with existing hydrometallurgical processes for recovering Al and Ag from decommissioned photovoltaic modules, this invention proposes a method for the stepwise separation of valuable metals Ag, Si, and Al from decommissioned photovoltaic cells. Based on the Zn-Al and Zn-Ag binary phase diagrams, at temperatures above 500℃, Al has a solubility of over 35% in Zn, and Ag has a solubility of over 10% in Zn. Furthermore, the content of Al and Ag in decommissioned photovoltaic cells is only about 10% and 0.7%, respectively. Therefore, this invention uses zinc as a collector, mixing it with silicon cell powder, and at low temperatures (with silicon remaining in a solid phase), collects silver and aluminum from the powder to obtain a Zn-Al-Ag melt. Simultaneously, due to density differences (e.g., at 500~550℃, the density of the Zn-Al-Ag melt is approximately 5~6 g / cm³), the process is optimized. 3 The density of solid silicon is 2.3 g / cm³. 3 Silicon battery powder will float to the surface of the Zn-Al-Ag melt, achieving solid-liquid separation; at a temperature of 700~850℃, the saturated vapor pressure of Zn is approximately 9.25×10⁻⁶. 5 ~1.06×10 7 The pressure is much higher than 20-50 Pa, so the obtained Zn-Al-Ag melt is vacuum-vaporized to separate Zn from the melt, resulting in metallic Zn and Al-Ag alloy melt. The metallic Zn can be recycled as a scavenging agent. Based on the Gibbs free energy, the equilibrium decomposition pressure of Al2O3 and the critical decomposition pressure of Ag are calculated, and the oxygen content range is found to be (1.29 × 10⁻⁶ Pa).-29 (~72.05%), therefore, under oxygen content (30~60%) conditions, Al can be selectively oxidized in Al-Ag melt, while Ag is not oxidized. Oxygen is blown into the Al-Ag alloy melt, causing Al to be selectively oxidized to Al2O3, which floats to the melt surface. After solid-liquid separation, Al2O3 and metallic Ag are obtained. The entire process of this invention uses physical methods (no waste residue or waste liquid), achieving efficient separation of aluminum, silver, and silicon in retired photovoltaic cells. The Zn trap can be recycled, achieving the goal of sustainable recycling of retired photovoltaic modules.
[0005] A method for separating valuable metals Ag, Si, and Al from decommissioned photovoltaic cells in stages, the specific steps of which are as follows: (1) Mechanically crush and grind retired photovoltaic silicon cells to obtain retired photovoltaic silicon cell powder; (2) The silicon cell powder and metal Zn are mixed evenly to obtain a mixture. The mixture is heated under an inert atmosphere to melt the metal Zn and form a Zn melt. The Al and Ag in the silicon cell powder are captured into the Zn melt by mechanical stirring. The silicon powder is kept in solid phase and floats to the upper layer of the melt. Solid-liquid separation is performed to obtain solid silicon powder and Zn-Al-Ag alloy melt. (3) Add the Zn-Al-Ag alloy melt to a high-temperature vacuum gasification furnace for vacuum gasification and separation to obtain the residual Al-Ag alloy and the condensed product metallic Zn. The metallic Zn is returned to step (2) and mixed with silicon cell powder. (4) Selective oxidation melting of Al-Ag alloy in oxidizing gas, so that Al in Al-Ag melt is selectively oxidized to Al2O3 and floats to the surface of melt, and solid-liquid separation is obtained to obtain solid phase Al2O3 and metallic Ag melt.
[0006] Preferably, the average particle size of the photovoltaic silicon cell powder in step (1) is 0.09~0.12mm.
[0007] Preferably, in step (2), the mass ratio of metallic Zn to silicon solar cell powder is 10~15:1, the collection temperature is 500~550℃, and the time is 2~3 h.
[0008] Preferably, the vacuum degree of the vacuum separation in step (3) is 20~50Pa and the vaporization temperature is 700~850℃.
[0009] Preferably, the oxidizing gas in step (4) is an O2-Ar mixture, in which O2 accounts for 30-60% of the volume.
[0010] More preferably, the selective oxidation smelting temperature in step (4) is 1000~1300℃ and the time is 3~5h.
[0011] The beneficial effects of this invention are: (1) The entire process of this invention does not involve strong acids, strong alkalis or cyanides, and no harmful wastewater is generated, making it environmentally friendly; (2) The zinc trapping agent of this invention can be recycled, which greatly reduces the cost of raw materials and improves the economic efficiency of the process; (3) The present invention achieves efficient and high-purity recovery of silver and aluminum through a three-stage physical metallurgical process. The process flow is short and easy to achieve large-scale continuous production. Attached Figure Description
[0012] Figure 1 This is a process flow diagram of the present invention; Figure 2 The following is a graph showing the Al and Ag collection efficiency after stirring for 2 hours when the mass ratio of metallic Zn to decommissioned photovoltaic cell powder is 15:1 in Example 1. Figure 3 The graph shows the Al and Ag collection efficiency after stirring for 3 hours when the mass ratio of metallic Zn to decommissioned photovoltaic cell powder is 10:1 in Example 4. Figure 4 The images show the physical and cross-sectional EDS diagrams of the condensed Zn and Al-Ag alloys after vacuum separation in Example 6. Figure 5 The graph shows the change in purity of Zn condensate after vacuum gasification separation at different temperatures and vacuum levels. Figure 6 The graph shows the change in purity of Ag and Al2O3 after selective oxidation for different times at 1000℃ and 30wt.%. Figure 7 The graph shows the change in purity of Ag and Al2O3 after selective oxidation at different times under conditions of 1300℃ and 60wt.%. Detailed Implementation
[0013] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.
[0014] In this embodiment of the invention, the proportion of Si in the decommissioned photovoltaic cell powder is 89.19 wt.%, the proportion of Ag is 0.73 wt.%, the proportion of Al is 10.08 wt.%, and the purity of metallic Zn is 99.995 wt.%.
[0015] Example 1: A method for stepwise separation of valuable metals Ag, Si, and Al in decommissioned photovoltaic cells (see Example 2) Figure 1 The specific steps are as follows: (1) The retired photovoltaic silicon cells were mechanically crushed and ground to obtain retired photovoltaic silicon cell powder with an average particle size of 0.09 mm; (2) A mixture of silicon solar cell powder and metallic Zn is prepared, wherein the mass ratio of metallic Zn to decommissioned photovoltaic cell powder is 15:1. The mixture is heated to 500°C, 525°C, and 550°C under an inert atmosphere (argon) to melt metallic Zn and form Zn melt. The mixture is then mechanically stirred for 2 hours to capture Al and Ag from the silicon solar cell powder into the Zn melt. The silicon powder remains in a solid phase and floats to the top of the melt. Solid-liquid separation is performed to obtain solid silicon powder and Zn-Al-Ag alloy melt. After capturing 10 batches of decommissioned photovoltaic cell powder at 500°C, the average residual amount of Al in the cell powder is 1.24 wt.%, and the average Al capture rate is 87.70%. The average residual amount of Ag is 0.098 wt.%, and the average Ag capture rate is 86.58% (e.g., ...). Figure 2 As shown), the silicon powder purity was 98.66 wt.%; after collecting 10 batches of decommissioned photovoltaic cell powder at 525℃, the average residual Al content in the cell powder was 1.19 wt.%, with an average Al collection rate of 88.15%; the average residual Ag content was 0.08 wt.%, with an average Ag collection rate of 89.04% (as shown). Figure 2 As shown), the silicon powder purity was 98.73 wt.%; after collecting 10 batches of decommissioned photovoltaic cell powder at 550℃, the average residual Al content in the cell powder was 1.06 wt.%, with an average Al collection rate of 89.48%; the average residual Ag content was 0.061 wt.%, with an average Ag collection rate of 91.64% (see...). Figure 2 The purity of the silicon powder is 98.88 wt.%. (3) The Zn-Al-Ag alloy melt obtained by collecting retired photovoltaic cell powder at 500℃ is added to a high-temperature vacuum gasification furnace and vacuumed for 30 min at a vacuum degree of 20 Pa and a temperature of 700℃ to obtain residual Al-Ag alloy and condensed product metallic Zn. The metallic Zn is returned to step (2) and mixed with silicon cell powder. The percentage of residual metallic Zn in the Al-Ag alloy is 0.05 wt.% by mass; the purity of metallic Zn is 99.92 wt.% and the percentage of impurity aluminum is 0.08 wt.% (see Figure 5 ); (4) At a temperature of 1000℃, the Al-Ag alloy was selectively oxidized and smelted in an oxidizing gas (O2-Ar mixture, in which O2 accounts for 30% by volume) for 3h, 4h and 5h respectively, so that Al in the Al-Ag melt was selectively oxidized to Al2O3 and floated to the surface of the melt. Solid-liquid separation was performed to obtain solid phase Al2O3 and metallic Ag melt. In terms of mass percentage, the purity of metallic Ag in this embodiment was 80.38wt.%, 88.38wt.%, and 99.70wt.% respectively; the purity of Al2O3 was 99.66wt.%, 99.74wt.%, and 99.76wt.% respectively (see Figure 6 ).
[0016] Example 2: A method for stepwise separation of valuable metals Ag, Si, and Al in decommissioned photovoltaic cells (see Example 2) Figure 1 The specific steps are as follows: (1) The retired photovoltaic silicon cells were mechanically crushed and ground to obtain retired photovoltaic silicon cell powder with an average particle size of 0.09 mm; (2) A mixture of silicon solar cell powder and metallic Zn was uniformly mixed to obtain a mixture, wherein the mass ratio of metallic Zn to decommissioned photovoltaic cell powder was 12:1; the mixture was heated to 525°C under an inert atmosphere (argon) to melt metallic Zn and form Zn melt, and Al and Ag in the silicon solar cell powder were captured into the Zn melt by mechanical stirring for 2 hours, while silicon powder remained in a solid phase and floated to the upper layer of the melt. Solid-liquid separation was performed to obtain solid silicon powder and Zn-Al-Ag alloy melt; after capturing 10 batches of decommissioned photovoltaic cell powder, the average residual amount of Al in the cell powder was 1.14 wt.%, the average Al capture rate was 88.69%; the average residual amount of Ag was 0.087 wt.%, the average Ag capture rate was 88.08%, and the purity of silicon powder was 98.77 wt.%. (3) The Zn-Al-Ag alloy melt was added to a high-temperature vacuum gasification furnace and vacuum separated for 30 min at a vacuum degree of 30 Pa and a temperature of 750 °C to obtain the residual Al-Ag alloy and the condensed product metallic Zn. The metallic Zn was returned to step (2) and mixed with the silicon solar cell powder. The residual metallic Zn in the Al-Ag alloy accounted for 0.05 wt.% by mass; the purity of metallic Zn was 99.96 wt.% and the proportion of impurity aluminum was 0.09 wt.%. (4) At a temperature of 1150℃, the Al-Ag alloy was selectively oxidized and smelted in an oxidizing gas (O2-Ar mixture, in which O2 accounts for 45% by volume) for 3h, 4h and 5h respectively, so that Al in the Al-Ag melt was selectively oxidized to Al2O3 and floated to the surface of the melt. Solid-liquid separation was performed to obtain solid phase Al2O3 and metallic Ag melt. In terms of mass percentage, the purity of metallic Ag in this embodiment was 85.54wt.%, 97.07wt.%, and 99.90wt.% respectively; the purity of Al2O3 was 99.86wt.%, 99.95wt.%, and 99.97wt.% respectively.
[0017] Example 3: A method for stepwise separation of valuable metals Ag, Si, and Al in decommissioned photovoltaic cells (see Example 3) Figure 1 The specific steps are as follows: (1) The retired photovoltaic silicon cells are mechanically crushed and ground to obtain retired photovoltaic silicon cell powder with an average particle size of 0.10 mm; (2) A mixture of silicon solar cell powder and metallic Zn is prepared, wherein the mass ratio of metallic Zn to decommissioned photovoltaic cell powder is 10:1. The mixture is heated to 550°C under an inert atmosphere (argon) to melt metallic Zn and form Zn melt. The mixture is mechanically stirred for 2.5 h to capture Al and Ag in the silicon solar cell powder into the Zn melt. The silicon powder remains in a solid phase and floats to the upper layer of the melt. Solid-liquid separation is performed to obtain solid silicon powder and Zn-Al-Ag alloy melt. After capturing 10 batches of decommissioned photovoltaic cell powder, the average residual amount of Al in the battery powder is 1.03 wt.%, and the average Al capture rate is 89.76%. The average residual amount of Ag is 0.073 wt.%, and the average Ag capture rate is 89.98%. The purity of the silicon powder is 98.89 wt.%. (3) The Zn-Al-Ag alloy melt was added to a high-temperature vacuum gasification furnace and vacuum separated for 30 min at a vacuum of 50 Pa and a temperature of 800 °C to obtain the residual Al-Ag alloy and the condensed product metallic Zn. The metallic Zn was returned to step (2) and mixed with the silicon solar cell powder. The percentage of residual metallic Zn in the Al-Ag alloy was 0.006 wt.% by mass; the purity of metallic Zn was 99.94 wt.% and the percentage of impurity aluminum was 0.06 wt.% (see Figure 5 ); (4) At a temperature of 1300℃, the Al-Ag alloy was selectively oxidized and smelted in an oxidizing gas (O2-Ar mixture, in which O2 accounts for 60% by volume) for 3h, 4h and 5h respectively, so that Al in the Al-Ag melt was selectively oxidized to Al2O3 and floated to the surface of the melt. Solid-liquid separation was performed to obtain solid phase Al2O3 and metallic Ag melt. In terms of mass percentage, the purity of metallic Ag in this embodiment was 99.86wt.%, 99.95wt.%, and 99.95wt.% respectively; the purity of Al2O3 was 99.92wt.%, 99.97wt.%, and 99.98wt.% respectively (see Figure 7 ).
[0018] Example 4: A method for stepwise separation of valuable metals Ag, Si, and Al in decommissioned photovoltaic cells (see Example 4) Figure 1 The specific steps are as follows: (1) The retired photovoltaic silicon cells were mechanically crushed and ground to obtain retired photovoltaic silicon cell powder with an average particle size of 0.10 mm; (2) A mixture of silicon solar cell powder and metallic Zn is prepared, wherein the mass ratio of metallic Zn to decommissioned photovoltaic cell powder is 10:1. The mixture is heated to 500°C, 525°C, and 550°C under an inert atmosphere (argon) to melt metallic Zn and form Zn melt. The mixture is then mechanically stirred for 3 hours to capture Al and Ag from the silicon solar cell powder into the Zn melt. The silicon powder remains in a solid phase and floats to the upper layer of the melt. Solid-liquid separation is performed to obtain solid silicon powder and Zn-Al-Ag alloy melt. After capturing 10 batches of decommissioned photovoltaic cell powder at 500°C, the average residual amount of Al in the cell powder is 1.27 wt.%, with an average Al capture rate of 87.43%; the average residual amount of Ag is 0.108 wt.%, with an average Ag capture rate of 85.11% (e.g., ...). Figure 3 As shown), the silicon powder purity was 98.62 wt.%; after collecting 10 batches of decommissioned photovoltaic cell powder at 525℃, the average residual Al content in the cell powder was 1.17 wt.%, with an average Al collection rate of 88.39%; the average residual Ag content was 0.104 wt.%, with an average Ag collection rate of 85.75% (as shown). Figure 3 As shown), the silicon powder purity was 98.95 wt.%; after collecting 10 batches of decommissioned photovoltaic cell powder at 550℃, the average residual Al content in the cell powder was 0.98 wt.%, with an average Al collection rate of 90.27%; the average residual Ag content was 0.072 wt.%, with an average Ag collection rate of 90.14% (as shown). Figure 3 As shown), the powder purity is 98.73 wt.%; (3) The Zn-Al-Ag alloy melt obtained by collecting retired photovoltaic cell powder at 525℃ was added to a high-temperature vacuum gasification furnace and vacuum separated for 30 min at a vacuum degree of 50 Pa and a temperature of 750℃ to obtain residual Al-Ag alloy and condensed product metallic Zn. The metallic Zn was returned to step (2) and mixed with silicon cell powder. The percentage of residual metallic Zn in the Al-Ag alloy was 0.06 wt.% by mass; the purity of metallic Zn was 99.97 wt.% and the percentage of impurity aluminum was 0.03 wt.% (see Figure 5 ); (4) At a temperature of 1000℃, the Al-Ag alloy was selectively oxidized and smelted in an oxidizing gas (O2-Ar mixture, in which O2 accounts for 60% by volume) for 3h, 4h and 5h respectively, so that Al in the Al-Ag melt was selectively oxidized to Al2O3 and floated to the surface of the melt. Solid-liquid separation was performed to obtain solid phase Al2O3 and metallic Ag melt. In terms of mass percentage, the purity of metallic Ag in this embodiment was 88.38wt.%, 98.38wt.%, and 99.95wt.% respectively; the purity of Al2O3 was 99.63wt.%, 99.79wt.%, and 99.82wt.% respectively.
[0019] Example 5: A method for stepwise separation of valuable metals Ag, Si, and Al in decommissioned photovoltaic cells (see Example 5) Figure 1 The specific steps are as follows: (1) The retired photovoltaic silicon cells were mechanically crushed and ground to obtain retired photovoltaic silicon cell powder with an average particle size of 0.12 mm; (2) A mixture of silicon solar cell powder and metallic Zn is prepared, wherein the mass ratio of metallic Zn to decommissioned photovoltaic cell powder is 12:1. The mixture is heated to 500°C in an inert atmosphere (argon) to melt metallic Zn and form Zn melt. Al and Ag in the silicon solar cell powder are captured into the Zn melt by mechanical stirring for 2.5 h. The silicon powder remains in a solid phase and floats to the upper layer of the melt. Solid-liquid separation is performed to obtain solid silicon powder and Zn-Al-Ag alloy melt. After capturing 10 batches of decommissioned photovoltaic cell powder, the average residual amount of Al in the cell powder is 0.99 wt.%, and the average Al capture rate is 90.17%. The average residual amount of Ag is 0.083 wt.%, and the average Ag capture rate is 88.63%. The purity of silicon powder is 98.93 wt.%. (3) The Zn-Al-Ag alloy melt was added to a high-temperature vacuum gasification furnace and vacuum separated for 30 min at a vacuum of 30 Pa and a temperature of 700 °C to obtain the residual Al-Ag alloy and the condensed product metallic Zn. The metallic Zn was returned to step (2) and mixed with the silicon solar cell powder. The residual metallic Zn in the Al-Ag alloy accounted for 0.07 wt.% by mass; the purity of metallic Zn was 99.94 wt.% and the proportion of impurity aluminum was 0.06 wt.% (see Figure 5 ); (4) At a temperature of 1150℃, the Al-Ag alloy was selectively oxidized and smelted in an oxidizing gas (O2-Ar mixture, in which O2 accounts for 30% by volume) for 3h, 4h and 5h respectively, so that Al in the Al-Ag melt was selectively oxidized to Al2O3 and floated to the surface of the melt. Solid-liquid separation was performed to obtain solid phase Al2O3 and metallic Ag melt. In terms of mass percentage, the purity of metallic Ag in this embodiment was 87.46wt.%, 95.23wt.% and 99.10wt.% respectively; the purity of Al2O3 was 99.80wt.%, 99.93wt.% and 99.97wt.% respectively.
[0020] Example 6: A method for stepwise separation of valuable metals Ag, Si, and Al in decommissioned photovoltaic cells (see Example 6) Figure 1 The specific steps are as follows: (1) The retired photovoltaic silicon cells were mechanically crushed and ground to obtain retired photovoltaic silicon cell powder with an average particle size of 0.12 mm; (2) A mixture of silicon solar cell powder and metallic Zn was uniformly mixed to obtain a mixture, wherein the mass ratio of metallic Zn to decommissioned photovoltaic cell powder was 15:1; the mixture was heated to 550°C under an inert atmosphere (argon) to melt metallic Zn and form Zn melt, and Al and Ag in the silicon solar cell powder were captured into the Zn melt by mechanical stirring for 2.5 h, while silicon powder remained in a solid phase and floated to the upper layer of the melt. Solid-liquid separation was performed to obtain solid silicon powder and Zn-Al-Ag alloy melt; after capturing 10 batches of decommissioned photovoltaic cell powder, the average residual amount of Al in the cell powder was 0.73 wt.%, the average Al capture rate was 92.78%; the average residual amount of Ag was 0.041 wt.%, the average Ag capture rate was 94.32%, and the purity of silicon powder was 99.23 wt.%; (3) The Zn-Al-Ag alloy melt was added to a high-temperature vacuum gasification furnace and vacuum separated for 30 min at a vacuum of 20 Pa and a temperature of 800 °C to obtain the residual Al-Ag alloy and the condensed product metallic Zn. The metallic Zn was returned to step (2) and mixed with the silicon cell powder. The actual picture and cross-sectional EDS diagram of the condensed product Zn and the residual Al-Ag alloy after vacuum separation are shown in the figure. Figure 4 ,from Figure 4 It can be seen that the Zn signal in the condensate is strong and uniformly distributed, while Al exists only in a small amount of dot-like form, indicating that the condensate is mainly Zn with high purity. In contrast, the residue is dense and blocky with a continuous and uniform cross-sectional structure. EDS surface scan results show that the residue phase is mainly enriched in Al and Ag, which are continuously distributed in the matrix. No obvious Zn element signal was observed, indicating that Zn has been efficiently separated during the distillation process. The above results show that the vacuum distillation process used in this embodiment can utilize the vapor pressure difference between Zn and Al and Ag to achieve efficient separation and high-purity recovery of Zn and Al-Ag alloy, thus providing a reliable basis for the direct recovery and utilization of condensed Zn and further high-purity separation of residual Al-Ag alloy. By mass percentage, the residual metallic Zn in the Al-Ag alloy is 0.04 wt.%; the purity of metallic Zn is 99.86 wt.%, and the proportion of impurity aluminum is 0.08 wt.% (see...). Figure 5 ); (4) At a temperature of 1300℃, the Al-Ag alloy was selectively oxidized and smelted in an oxidizing gas (O2-Ar mixture, in which O2 accounts for 45% by volume) for 3h, 4h and 5h respectively, so that Al in the Al-Ag melt was selectively oxidized to Al2O3 and floated to the surface of the melt. Solid-liquid separation was performed to obtain solid phase Al2O3 and metallic Ag melt. In terms of mass percentage, the purity of metallic Ag in this embodiment was 99.54wt.%, 99.94wt.%, and 99.95wt.% respectively; the purity of Al2O3 was 99.88wt.%, 99.97wt.%, and 99.98wt.% respectively.
[0021] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.
Claims
1. A method for stepwise separation of valuable metals Ag, Si, and Al from decommissioned photovoltaic cells, characterized in that, The specific steps are as follows: (1) Mechanically crush and grind retired photovoltaic silicon cells to obtain retired photovoltaic silicon cell powder; (2) The silicon cell powder and metal Zn are mixed evenly to obtain a mixture. The mixture is heated under an inert atmosphere to melt the metal Zn and form a Zn melt. The Al and Ag in the silicon cell powder are captured into the Zn melt by mechanical stirring. The silicon powder is kept in solid phase and floats to the upper layer of the melt. Solid-liquid separation is performed to obtain solid silicon powder and Zn-Al-Ag alloy melt. (3) Add the Zn-Al-Ag alloy melt to a high-temperature vacuum gasification furnace for vacuum gasification and separation to obtain the residual Al-Ag alloy and the condensed product metallic Zn. The metallic Zn is returned to step (2) and mixed with silicon cell powder. (4) Selective oxidation melting of Al-Ag alloy in oxidizing gas, so that Al in Al-Ag melt is selectively oxidized to Al2O3 and floats to the surface of melt, and solid-liquid separation is obtained to obtain solid phase Al2O3 and metallic Ag melt.
2. The method for stepwise separation of valuable metals Ag, Si, and Al in decommissioned photovoltaic cells according to claim 1, characterized in that: Step (1) The average particle size of the retired photovoltaic silicon cell powder is 0.09~0.12mm.
3. The method for stepwise separation of valuable metals Ag, Si, and Al in decommissioned photovoltaic cells according to claim 1, characterized in that: Step (2) The mass ratio of metallic Zn to silicon solar cell powder is 10~15:1, the collection temperature is 500~550℃, and the time is 2~3 h.
4. The method for stepwise separation of valuable metals Ag, Si, and Al in decommissioned photovoltaic cells according to claim 1, characterized in that: The vacuum degree of step (3) vaporization separation is 20~50Pa and the vaporization temperature is 700~850℃.
5. The method for stepwise separation of valuable metals Ag, Si, and Al in decommissioned photovoltaic cells according to claim 1, characterized in that: Step (4) The oxidizing gas is an O2-Ar mixture, in which O2 accounts for 30-60% of the volume.
6. The method for stepwise separation of valuable metals Ag, Si, and Al in decommissioned photovoltaic cells according to claim 5, characterized in that: Step (4) Selective oxidation smelting temperature is 1000~1300℃, time is 3~5h.