A method for recovering silver, silicon and aluminum from discarded photovoltaic silicon cells

Abstract

The present invention relates to a method for respectively recovering silver, silicon and aluminum from discarded photovoltaic silicon cells, and belongs to the technical field of secondary resource recovery. The present invention mechanically crushes and grinds discarded photovoltaic silicon cells to obtain discarded photovoltaic silicon cell powder; uniformly mixes collector metal lead and discarded photovoltaic silicon cell powder to obtain a mixed material, heats the mixed material under an argon atmosphere, and performs lead capture of silver under stirring conditions, and solid-liquid separation to obtain a silver-containing lead liquid and a solid-phase silicon-aluminum mixture; the silver-containing lead liquid is heated under vacuum conditions, and vacuum distillation is performed to separate lead and silver to obtain metallic silver and metallic lead, and the metallic lead is returned as a collector; the solid-phase silicon-aluminum mixture is electrostatically separated to separate silicon and aluminum to obtain silicon and metallic aluminum. The present invention can realize the separate recovery of valuable metal silver, silicon and aluminum in discarded photovoltaic cells, and the lead used as a collector can be recycled, and has the characteristics of cleanliness, high efficiency, and short process.

Description

Technical Field

[0001] The invention relates to a method for respectively recovering silver, silicon and aluminum from discarded photovoltaic silicon cells, belonging to the technical field of secondary resource recovery. Background Art

[0002] Since discarded silicon photovoltaic modules contain heavy metal lead (tin-lead coating on the surface of the soldering ribbon), if they are not recycled, they will cause environmental pollution. In addition, discarded silicon cells and photovoltaic soldering ribbons in discarded silicon photovoltaic modules contain valuable metals such as silicon, silver, copper, tin and aluminum. Recycling these valuable metals can promote the sustainability of resources. Therefore, recycling valuable metals from discarded silicon photovoltaic modules can achieve sustainable development of photovoltaic energy.

[0003] At present, the valuable metals silicon, silver and aluminum in discarded photovoltaic silicon cells are mainly extracted through hydrometallurgical processes. The hydrometallurgical extraction process of valuable metals from discarded silicon photovoltaic modules can be summarized as follows: first, use acid (HCl, H2SO4 and HNO3, etc.) / alkali (NaOH and KOH, etc.) to leach the discarded photovoltaic silicon cells, dissolve the valuable metals silver and aluminum into the solution, and filter and recover the insoluble solid silicon; then, separate the metal silver and aluminum from the solution through precipitation, reduction, electrolysis and other processes. It can be seen that the above-mentioned hydrometallurgical process is complex and delicate, and specific acid, alkaline solutions or electrolytes are used in the processes of leaching, precipitation, reduction, electrolysis, etc., which will produce a large amount of waste liquid that is potentially harmful to the environment, increasing the risk of environmental pollution. Summary of the invention

[0004] In view of the problems of complex process and large amount of waste liquid discharge in the extraction of valuable metal silicon, silver and aluminum from discarded photovoltaic silicon cells in the prior art, the present invention proposes a method for recovering silver, silicon and aluminum from discarded photovoltaic silicon cells. The present invention uses lead as a collector to capture silver from discarded photovoltaic silicon cells under conditions below the melting points of aluminum and silicon, while the solid phase aluminum (2.7 g / cm 3 ) and silicon (2.3 g / cm 3 ) Because the density is much smaller than that of lead (11.3 g / cm 3 ), will float to the surface of the silver-containing lead liquid, and after solid-liquid separation, the silver-containing lead liquid and the solid phase silicon-aluminum mixture are obtained. The silver-containing lead liquid can be separated into metallic lead and silver through vacuum distillation, and the metallic lead can be recycled as a collector; the solid phase silicon-aluminum mixture can be separated into silicon and metallic aluminum through electrostatic separation. The entire process of the present invention adopts physical methods (no waste residue, waste liquid), achieving the purpose of green and efficient recycling of discarded photovoltaic silicon cells.

[0005] A method for recovering silver, silicon and aluminum from discarded photovoltaic silicon cells, the specific steps are as follows:

[0006] (1) Mechanically crushing and grinding the discarded photovoltaic silicon cell sheets to obtain discarded photovoltaic silicon cell sheet powder;

[0007] (2) uniformly mixing the collector metal lead and the waste photovoltaic silicon cell powder to obtain a mixed material, heating and melting the mixed material in an argon atmosphere, and performing lead capture of silver under stirring conditions, and performing solid-liquid separation to obtain a silver-containing lead liquid and a solid phase silicon-aluminum mixture;

[0008] (3) heating the silver-lead liquid under vacuum conditions and performing vacuum distillation to separate lead and silver to obtain metallic silver and metallic lead, and returning the metallic lead to step (2) as a collector;

[0009] (4) The solid phase silicon-aluminum mixture is subjected to electrostatic separation to separate the silicon and aluminum to obtain silicon and metallic aluminum.

[0010] The average particle size of the discarded photovoltaic silicon cell powder in step (1) is no more than 0.074 mm.

[0011] In the step (2), the mass ratio of the collector metal lead to the waste photovoltaic silicon cell powder is 1.5:1 to 3:1, and the temperature at which the lead captures the silver is 400 to 550°C.

[0012] The temperature of the vacuum distillation in step (3) is 900-1100° C., the vacuum degree is 5-15 Pa, and the vacuum distillation time is 40-100 min.

[0013] The electrostatic separation voltage in step (4) is 25 to 35 kV, and the rotation speed is 45 to 75 r / min.

[0014] The beneficial effects of the present invention are:

[0015] (1) In the lead capture-vacuum distillation-electrostatic separation method of the present invention, each process adopts a physical method, so that no waste liquid, waste gas, or waste residue is discharged during the entire production process, thereby achieving the purpose of green recovery of silver, silicon, and aluminum in waste photovoltaic silicon cell modules, and achieving the sustainable development of silver, silicon, and aluminum resources;

[0016] (2) The three-step process of lead capture-vacuum distillation-electrostatic separation of the present invention has a shorter and simpler process than the traditional hydrometallurgical recovery process (leaching-precipitation-oxidation-reduction-electrolysis), and achieves the purpose of efficiently recovering valuable metals in waste photovoltaic silicon cell modules;

[0017] (3) The method of the present invention simplifies the process flow, reduces the treatment of complex waste liquids, and can effectively reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1This is a graph showing the change of silver recovery rate with lead capture silver temperature under different lead capture silver time;

[0019] Figure 2 This is a graph showing the change of silver content in lead-silver alloy with vacuum distillation time at different vacuum distillation temperatures. DETAILED DESCRIPTION

[0020] 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.

[0021] Example 1: A method for recovering silver, silicon and aluminum from discarded photovoltaic silicon cells, the specific steps are as follows:

[0022] (1) The waste photovoltaic silicon cell pieces are mechanically crushed and ground to a particle size of 0.061 to 0.074 mm to obtain waste photovoltaic silicon cell piece powder;

[0023] (2) uniformly mixing collector metal lead (with a purity of 99.99%) and waste photovoltaic silicon cell powder to obtain a mixed material, heating and melting the mixed material in an argon atmosphere, allowing the metal lead to capture silver for 60 minutes under stirring at a temperature of 550° C., and performing solid-liquid separation by siphoning to obtain a silver-containing lead liquid and a solid-phase silicon-aluminum mixture; wherein the mass ratio of the collector metal lead to the waste photovoltaic silicon cell powder is 1.5:1; after the silver-containing lead liquid captures 10 batches of waste photovoltaic silicon cell powder, the silver content in the silver-containing lead liquid is 5.2wt.%, and the average recovery rate of silver is 94.1%;

[0024] (3) heating the silver-lead liquid under vacuum conditions and performing vacuum distillation to separate lead and silver to obtain metallic silver and metallic lead, and returning the metallic lead to step (2) as a collector; wherein the vacuum distillation temperature is 900° C., the vacuum degree is 5 Pa, and the vacuum distillation time is 100 min;

[0025] (4) subjecting the solid phase silicon-aluminum mixture to electrostatic separation to separate silicon and aluminum to obtain silicon and metallic aluminum; wherein the electrostatic separation voltage is 25 kV and the rotation speed is 45 r / min;

[0026] In this embodiment, the purity of metallic silver is 89.7wt.%, the purity of metallic lead is 99.7wt.%, the metallic lead contains 0.3wt.% silver, the purity of silicon is 96.7wt.%, and the purity of metallic aluminum is 97.1wt.%.

[0027] Example 2: A method for recovering silver, silicon and aluminum from discarded photovoltaic silicon cells, the specific steps are as follows:

[0028] (1) The waste photovoltaic silicon cell pieces are mechanically crushed and ground to a particle size of 0.053-0.061 mm to obtain waste photovoltaic silicon cell piece powder;

[0029] (2) uniformly mixing collector metal lead (with a purity of 99.99%) and waste photovoltaic silicon cell powder to obtain a mixed material, heating and melting the mixed material in an argon atmosphere, allowing the metal lead to capture silver for 120 minutes under stirring at a temperature of 550° C., and performing solid-liquid separation by siphoning to obtain a silver-containing lead liquid and a solid-phase silicon-aluminum mixture; wherein the mass ratio of the collector metal lead to the waste photovoltaic silicon cell powder is 3:1; after the silver-containing lead liquid captures 10 batches of waste photovoltaic silicon cell powder, the silver content in the silver-containing lead liquid is 3wt.%, and the average recovery rate of silver is 98.9%;

[0030] (3) heating the silver-lead liquid under vacuum conditions and performing vacuum distillation to separate lead and silver to obtain metallic silver and metallic lead, and returning the metallic lead to step (2) as a collector; wherein the vacuum distillation temperature is 1100° C., the vacuum degree is 15 Pa, and the vacuum distillation time is 100 min;

[0031] (4) subjecting the solid phase silicon-aluminum mixture to electrostatic separation to separate silicon and aluminum to obtain silicon and metallic aluminum; wherein the electrostatic separation voltage is 35 kV and the rotation speed is 70 r / min;

[0032] In this embodiment, the purity of metallic silver is 99.6wt.%, the purity of metallic lead is 99.3wt.%, the metallic lead contains 0.7wt.% silver, the purity of silicon is 98.6wt.%, and the purity of metallic aluminum is 98.7wt.%.

[0033] Example 3: A method for recovering silver, silicon and aluminum from discarded photovoltaic silicon cells, the specific steps are as follows:

[0034] (1) The waste photovoltaic silicon cell pieces are mechanically crushed and ground to a particle size of 0.053-0.061 mm to obtain waste photovoltaic silicon cell piece powder;

[0035] (2) The collector metal lead (with a purity of 99.99%) and the waste photovoltaic silicon cell powder are uniformly mixed to obtain a mixed material, and the mixed material is heated and melted in an argon atmosphere, so that the metal lead captures silver for 60 minutes and 120 minutes at temperatures of 400° C., 450° C., 500° C. and 550° C. under stirring conditions, and solid-liquid separation is performed by siphoning to obtain a silver-containing lead liquid and a solid phase silicon-aluminum mixture; wherein the mass ratio of the collector metal lead to the waste photovoltaic silicon cell powder is 2:1; the lead captures silver at temperatures of 400° C., 450° C., 500° C. and 550° C., respectively, and the lead captures silver at temperatures of 400° C., 450° C., 500° C. and 550° C., respectively, and the solid-liquid separation is performed by siphoning to obtain a silver-containing lead liquid and a solid phase silicon-aluminum mixture; Under the condition of silver capture time of 60min, after the silver-containing lead liquid captured 12 batches of waste photovoltaic silicon cell powder, the silver content in the silver-containing lead liquid was 4.1wt.%, 4.3wt.%, 4.6wt.%, 4.8wt.%, and the average recovery rate of silver was 87.3%, 90.5%, 93.8%, 95.2%; when the lead captured silver for 120min, the silver content in the silver-containing lead liquid was 4.3wt.%, 4.6wt.%, 5.0wt.%, 5.1wt.%, and the average recovery rate of silver was 91.2%, 94.5%, 96.1%, 98% (see Figure 1 );

[0036] (3) heating the silver-lead liquid under vacuum conditions and performing vacuum distillation to separate lead and silver to obtain metallic silver and metallic lead, and returning the metallic lead to step (2) as a collector; wherein the vacuum distillation temperature is 1000° C., the vacuum degree is 10 Pa, and the vacuum distillation time is 80 min;

[0037] (4) subjecting the solid phase silicon-aluminum mixture to electrostatic separation to separate silicon and aluminum to obtain silicon and metallic aluminum; wherein the electrostatic separation voltage is 30 kV and the rotation speed is 65 r / min;

[0038] In this embodiment, the temperatures for lead to capture silver are 400° C., 450° C., 500° C. and 550° C., respectively. When lead captures silver for 60 minutes, the purity of metallic silver is 97.3wt.%, 98.4wt.%, 98.8wt.%, 99.4wt.%, respectively; the purity of metallic lead is 99.7wt.%, 99.5wt.%, 99.4wt.%, respectively; the purity of silicon is 97.0wt.%, 97.8wt.%, 98.1wt.%, 98.3wt.%, respectively; the purity of metallic aluminum is 97.5wt.%, 98.1wt.%, 99.4wt.%, respectively. 8.5wt.%, 98.7wt.%; when lead captured silver for 120min, the purities of metallic silver were 98.5wt.%, 98.7wt.%, 99.2wt.%, 99.5wt.%, respectively; the purities of metallic lead were 99.6wt.%, 99.5wt.%, 99.2wt.%, 99.1wt.%, respectively; the purities of silicon were 97.7wt.%, 98.0wt.%, 98.2wt.%, 98.5wt.%, respectively; and the purities of metallic aluminum were 97.9wt.%, 98.3wt.%, 98.6wt.%, 98.9wt.%, respectively.

[0039] Example 4: A method for recovering silver, silicon and aluminum from discarded photovoltaic silicon cells, the specific steps are as follows:

[0040] (1) The waste photovoltaic silicon cell pieces are mechanically crushed and ground to a particle size of 0.053-0.061 mm to obtain waste photovoltaic silicon cell piece powder;

[0041] (2) uniformly mixing collector metal lead (with a purity of 99.99%) and waste photovoltaic silicon cell powder to obtain a mixed material, heating and melting the mixed material in an argon atmosphere, allowing the metal lead to capture silver for 120 minutes under stirring conditions at a temperature of 550° C., and performing solid-liquid separation by siphoning to obtain a silver-containing lead liquid and a solid-phase silicon-aluminum mixture; wherein the mass ratio of the collector metal lead to the waste photovoltaic silicon cell powder is 1.5:1; after the silver-containing lead liquid captures 10 batches of waste photovoltaic silicon cell powder, the silver content in the silver-containing lead liquid is 6wt.%, and the average recovery rate of silver is 99%;

[0042] (3) heating the silver-lead liquid under vacuum conditions and performing vacuum distillation to separate lead and silver to obtain metallic silver and metallic lead, and returning the metallic lead to step (2) as a collector; wherein the vacuum distillation temperature is 900° C., 1000° C. and 1100° C., the vacuum degree is 15 Pa, and the vacuum distillation time is 40 min, 60 min, 80 min, and 100 min, respectively; the variation of the silver content in the lead-silver alloy with the vacuum distillation time at different vacuum distillation temperatures is shown in FIG. Figure 2 ;

[0043] (4) The solid phase silicon-aluminum mixture is subjected to electrostatic separation to separate silicon and aluminum to obtain silicon and metallic aluminum; wherein the electrostatic separation voltage is 35 kV and the rotation speed is 75 r / min; the silicon purity is 98.8% and the aluminum purity is 99.0%.

[0044] In this embodiment, the vacuum distillation time is 40min, 60min, 80min, and 100min, respectively. When the vacuum distillation temperature is 900°C, the metallic silver content in the residual alloy is 18.3wt.%, 53.4wt.%, 75.8wt.%, and 89.9wt.%, respectively. The purity of the condensed metallic lead is 99.9wt.%, 99.8wt.%, 99.7wt.%, and 99.5wt.%, respectively. When the vacuum distillation temperature is 1000°C, the metallic silver content in the residual alloy is 77.5wt.%, respectively. , 93.7wt.%, 97.2wt.%, 99.6wt.%, and the purity of the condensed metallic lead was 99.7wt.%, 99.7wt.%, 99.5wt.%, 99.3wt.% respectively; when the vacuum distillation temperature was 1100°C, the metallic silver contents in the residual alloy were 90.4wt.%, 94.9wt.%, 98.2wt.%, 99.8wt.% respectively, and the purity of the condensed metallic lead was 99.6wt.%, 99.4wt.%, 99.2wt.%, 99.0wt.% respectively.

[0045] 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 method for recovering silver, silicon and aluminum from discarded photovoltaic silicon cells, characterized in that: The specific steps are as follows: (1) Waste photovoltaic silicon cell sheets are mechanically crushed and ground to obtain waste photovoltaic silicon cell sheet powder; the average particle size of the waste photovoltaic silicon cell sheet powder is not greater than 0.074 mm; (2) uniformly mixing the collector metal lead and the waste photovoltaic silicon cell powder to obtain a mixed material, heating and melting the mixed material in an argon atmosphere, and performing lead capture of silver under stirring conditions, and performing solid-liquid separation to obtain a silver-containing lead liquid and a solid phase silicon-aluminum mixture; the mass ratio of the collector metal lead to the waste photovoltaic silicon cell powder is 1.5:1 to 3:1, and the temperature for lead capture of silver is 400 to 550° C.; (3) heating the silver-lead liquid under vacuum conditions and performing vacuum distillation to separate lead and silver to obtain metallic silver and metallic lead, and returning the metallic lead to step (2) as a collector; (4) The solid phase silicon-aluminum mixture is subjected to electrostatic separation to separate the silicon and aluminum to obtain silicon and metallic aluminum.

2. The method for recovering silver, silicon and aluminum from discarded photovoltaic silicon cells according to claim 1, characterized in that: The temperature of the vacuum distillation in step (3) is 900-1100° C., the vacuum degree is 5-15 Pa, and the vacuum distillation time is 40-100 min.

3. The method for recovering silver, silicon and aluminum from discarded photovoltaic silicon cells according to claim 2, characterized in that: Step (4) electrostatic separation voltage 25 ~ 35kV, speed 45 ~ 75r / min.

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