Method for preparing aluminum-silicon alloy by recycling retired photovoltaic modules

Abstract

The invention relates to the technical field of resource recycling and alloy material preparation, in particular to a method for preparing an aluminum-silicon alloy by recycling retired photovoltaic modules. The method comprises the following steps: step 1, mechanically disassembling the retired photovoltaic module to obtain an aluminum frame and a laminated piece; 2, pyrolyzing the laminated piece, and separating out a crystalline silicon battery piece; step 3, performing crushing and acid etching on the crystalline silicon battery piece to obtain a silicon wafer; 4, the aluminum frame is smelted to obtain a melt; and uniformly mixing a silicon wafer and a fluxing agent, adding the mixture into the melt, preserving heat, and casting to obtain the aluminum-silicon alloy. The aluminum-silicon alloy is prepared from the retired photovoltaic module, and compared with other preparation methods, the raw material cost is low, and the production cost of the aluminum-silicon alloy is greatly reduced. The method is short in process, green and environmentally friendly, capable of achieving high-valued recovery of aluminum and silicon in the retired photovoltaic module and suitable for the fields of automobile part and electronic device manufacturing and the like.

Description

Technical Field

[0001] This invention relates to the field of resource recycling and alloy material preparation technology, and in particular to a method for preparing aluminum-silicon alloys from recycled decommissioned photovoltaic modules. Background Technology

[0002] With the rapid development of the photovoltaic industry, a large number of early-installed crystalline silicon photovoltaic modules are gradually entering their retirement period, and a large-scale accumulation of obsolete modules is expected within the next decade. If not properly handled, this will not only waste resources but also pose environmental pollution risks. Utilizing retired photovoltaic modules for resource recovery can not only reduce dependence on primary resources but also decrease energy consumption and carbon emissions, aligning with the development needs of a circular economy and green manufacturing.

[0003] Photovoltaic modules mainly consist of glass, solar cells, and a backsheet. The modules are bonded together with EVA and fixed by an aluminum frame. Glass, aluminum, and silicon constitute a significant portion of photovoltaic modules, with glass accounting for approximately 60%–75% of the total module mass, aluminum for approximately 10%–15%, and silicon wafers for approximately 2%–5%. Aluminum has high recycling value and is relatively easy to dismantle. Existing recycling methods for aluminum frames primarily employ physical dismantling, a mature and efficient process. While the recycled aluminum frames can be used directly as recycled aluminum, their value is low. Although silicon wafers constitute a smaller percentage of the module's mass, their manufacturing process is extremely energy-intensive and economically significant, making recycling crucial. For silicon wafer recycling, pyrolysis or thermal delamination processes are typically used to remove encapsulation materials such as EVA. Then, mechanical crushing, sorting, and chemical treatment are used to remove surface impurities. Finally, metallurgical smelting yields recycled silicon. However, due to impurities in the silicon wafers of retired modules, their quality still falls short of the purity requirements for photovoltaic-grade silicon.

[0004] Therefore, a method is proposed to directly smelt aluminum and silicon recovered from retired photovoltaic modules to prepare aluminum-silicon alloys, which simplifies the processing flow and realizes efficient resource recycling of retired photovoltaic modules. This is of great significance to the fields of resource recycling and alloy material preparation technology. Summary of the Invention

[0005] Based on the above, this invention proposes a method for preparing aluminum-silicon alloy from recycled decommissioned photovoltaic modules. This method combines pyrolysis, acid etching, and alloy smelting processes to recover aluminum and silicon from decommissioned photovoltaic modules and smelt them to obtain aluminum-silicon alloy. Compared with other methods for recycling photovoltaic modules in steps, this method uses a one-step smelting method to prepare aluminum-silicon alloy, achieving integrated recycling with a short process and high value.

[0006] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of this invention is a method for preparing aluminum-silicon alloy from recycled decommissioned photovoltaic modules, comprising the following steps: Step 1: Mechanically disassemble the retired photovoltaic modules to obtain aluminum frames and laminates; Step 2: Pyrolyze the laminate to separate the crystalline silicon solar cells; Step 3: The crystalline silicon solar cell is crushed and acid-etched to obtain a silicon wafer; Step 4: Melt the aluminum frame to obtain a melt; mix the silicon wafer with the flux and add it to the melt for smelting and casting to obtain an aluminum-silicon alloy.

[0007] The second technical solution of the present invention is an aluminum-silicon alloy prepared according to the above method.

[0008] Compared with the prior art, the present invention has the following beneficial effects: 1. Compared with other methods for recycling photovoltaic modules in stages, the method of the present invention uses a one-step melting method to prepare aluminum-silicon alloy, realizing a short-process, high-value, synergistic and integrated recycling.

[0009] 2. Flux is used to remove the oxide film on the aluminum frame and silicon wafer surface, achieving efficient recycling. At the same time, it can prevent the melt from oxidizing during the smelting process, thus playing a refining role.

[0010] 3. This invention utilizes retired photovoltaic modules to prepare aluminum-silicon alloys. Compared to other preparation methods, the raw material costs are low, significantly reducing the production cost of aluminum-silicon alloys. The method of this invention has a short process, is environmentally friendly, and enables the high-value recycling of aluminum and silicon from retired photovoltaic modules, making it suitable for fields such as automotive parts and electronic device manufacturing. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the process flow for preparing aluminum-silicon alloy using retired photovoltaic modules according to the present invention. Detailed Implementation

[0013] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0014] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0015] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0016] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0017] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0018] Unless otherwise specified, the "%" in this invention refers to a percentage by mass.

[0019] This invention proposes a method for preparing aluminum-silicon alloys from recycled decommissioned photovoltaic (PV) modules. The method involves directly smelting recycled aluminum and silicon from the decommissioned PV modules to produce the alloy. Notably, the silicon wafers of decommissioned PV modules are typically covered with an aluminum electrode layer. In traditional photovoltaic-grade silicon regeneration processes, this aluminum layer must be completely removed to ensure silicon purity. However, in the alloying utilization pathway proposed in this invention, this aluminum layer does not need to be removed and can be directly used as a raw material component in the smelting process. This simplifies the processing, reduces the amount of chemical reagents used, lowers environmental pollution, and achieves efficient resource recycling of decommissioned PV modules.

[0020] The first aspect of this invention provides a method for preparing aluminum-silicon alloys from recycled decommissioned photovoltaic modules, comprising the following steps: Step 1: Mechanically disassemble the retired photovoltaic modules to obtain aluminum frames and laminates; Step 2: Pyrolyze the laminate to separate the crystalline silicon solar cells; Step 3: The crystalline silicon solar cell is crushed and acid-etched to obtain a silicon wafer; Step 4: Melt the aluminum frame to obtain a melt; mix the silicon wafer with the flux and add it to the melt for smelting and casting to obtain an aluminum-silicon alloy.

[0021] Mechanical disassembly methods are conventional techniques in this field and are not the focus of this invention's patent protection; therefore, they will not be elaborated upon here.

[0022] The retired photovoltaic modules are crystalline silicon photovoltaic modules with a service life of 25 to 30 years. They mainly include glass, crystalline silicon cells, backsheet and aluminum frame. The mass fraction of glass in the retired photovoltaic modules is 60% to 75%, the mass fraction of aluminum is 10% to 15%, and the mass fraction of crystalline silicon cells is 2% to 5%.

[0023] In a preferred embodiment of the present invention, in step 2, the pyrolysis conditions are set as follows: pyrolysis at 520~540℃ for 15~20 min under an inert atmosphere.

[0024] In this invention, the purpose of pyrolysis is to remove the EVA film. In a preferred embodiment of this invention, in step 3, the material is broken down to a size no larger than 5 mm.

[0025] In a preferred embodiment of the present invention, in step 3, the acid etching conditions are set as follows: the broken crystalline silicon solar cell is immersed in a mixed etching solution and etched at room temperature for 10-15 minutes.

[0026] In a preferred embodiment of the present invention, the mixed etching solution is a mixed aqueous solution of HNO3, C6H8O7 and HF; the content of HNO3 in the mixed etching solution is 10~20wt%, the content of C6H8O7 is 5~10wt%, and the content of HF is 2~10wt%.

[0027] In this invention, the purpose of acid etching is to remove the silver layer on the surface of the silicon wafer.

[0028] The acid etching process also includes a step of rinsing with water until no residue remains and then drying.

[0029] In a preferred embodiment of the present invention, in step 4, the amount of silicon wafer added is 5-20 wt% of the mass of the aluminum frame; the amount of flux added is 5-15 wt% of the total mass of the aluminum frame and the silicon wafer; the flux is a mixture of fluoride and carbonate in a mass ratio of 1:(1-2); the fluoride is cryolite (Na3AlF6) and / or NaF; the carbonate is K2CO3 and / or Na2CO3.

[0030] In a preferred embodiment of the present invention, in step 4, the melting temperature is 900~1100℃. After the silicon wafer and flux are mixed evenly, they are fed into the bottom 1 / 3 of the melt in 3~5 batches through a long tube or feeder. The time interval between each feeding is 5 minutes to prevent uneven melting. After the last feeding, the temperature is maintained for 20~30 minutes.

[0031] The aluminum frame melts at the same temperature as it is smelted.

[0032] After the heat preservation is completed and before casting, there is also a step of stirring by electromagnetic and argon gas. Stirring by electromagnetic and argon gas is a conventional technical means in this field and is not the focus of this invention patent protection, so it will not be described in detail here. The purpose of stirring is to make the melt composition uniform and to eliminate temperature gradients and avoid excessive temperature difference between the upper and lower layers.

[0033] Preheat the mold to 150~250℃ before casting.

[0034] A second aspect of the present invention provides an aluminum-silicon alloy prepared according to the above method.

[0035] The present invention also provides an apparatus for the above-mentioned method of preparing aluminum-silicon alloy from recycled decommissioned photovoltaic modules, comprising a pyrolysis furnace, an acid etching tank, a smelting furnace and a casting mold connected in sequence; a waste heat recovery system is provided between the pyrolysis furnace and the smelting furnace, and the pyrolysis tail gas is recovered by a heat exchange device for preheating the smelting furnace.

[0036] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0037] The retired photovoltaic modules used in this embodiment of the invention are monocrystalline silicon photovoltaic modules with a service life of 26 years. They mainly consist of glass, solar cells, and a backsheet. The modules are bonded together with EVA and fixed with an aluminum frame. The photovoltaic module contains 73% glass, 14% aluminum, and 2% silicon wafers by mass.

[0038] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0039] The process flow for preparing aluminum-silicon alloys using retired photovoltaic modules in this invention is as follows: Figure 1 As shown.

[0040] Example 1 Step 1: Separate the aluminum frame and junction box of 60 retired photovoltaic modules by mechanical cutting to obtain the aluminum frame and laminate.

[0041] Step 2: The laminate is pyrolyzed under an argon atmosphere at a temperature of 540℃ for 20 minutes. After pyrolysis, the crystalline silicon solar cell is separated.

[0042] Step 3: The crystalline silicon solar cells separated after pyrolysis are crushed to a size limit of 5mm. They are then immersed in a mixed etching solution (water as solvent) of HNO3 (10wt%), C6H8O7 (10wt%), and HF (10wt%), and etched for 12 minutes at room temperature. After etching, they are rinsed with deionized water until no residue remains and dried in an oven at 120℃ to obtain silicon wafers with a purity of 99.97% for later use. Testing shows that the silver removal rate reaches approximately 99.6%.

[0043] Step 4: Place the aluminum frame in a medium-frequency induction furnace and heat to 900℃. Mix the silicon wafer and flux evenly, then gradually add them to the bottom 1 / 3 of the melt in three separate additions through a long tube, 5 minutes apart. The amount of silicon wafer added is 10 wt% of the aluminum frame. The flux consists of industrial-grade cryolite and K2CO3 (industrial-grade cryolite to K2CO3 mass ratio 1:1, flux added is 5 wt% of the total amount of aluminum frame and silicon wafer). After the last addition of the silicon wafer and flux mixture, hold at the temperature for 25 minutes. After melting, stir for 5 minutes using a combination of electromagnetic and argon gas. After the melt has settled for 1 minute, remove slag and cast the melt into a preheated mold at 150℃ to obtain a homogeneous aluminum-silicon alloy (alloy silicon content 9.19%) with a hardness of HB89. 90.6% Al and 91.9% Si were recovered.

[0044] Example 2 Step 1: Same as Step 1 in Example 1.

[0045] Step 2: Same as Step 2 in Example 1.

[0046] Step 3: The crystalline silicon solar cells separated after pyrolysis are crushed to a size limit of 5mm. They are then immersed in a mixed etching solution (water as solvent) of HNO3 (20wt%), C6H8O7 (5wt%), and HF (2wt%), and etched for 10 minutes at room temperature. After etching, they are rinsed with deionized water until no residue remains and dried in an oven at 120℃ to obtain silicon wafers with a purity of 99.96% for later use. Testing shows that the silver removal rate reaches approximately 99.7%.

[0047] Step 4: Place the aluminum frame in a medium-frequency induction furnace and heat to 960℃. Then, uniformly mix the silicon wafer and flux, and gradually add them to the bottom 1 / 3 of the melt through a long tube in 5 batches, 5 minutes apart. The amount of silicon wafer added is 15 wt% of the aluminum frame. The flux composition is industrial-grade cryolite and Na2CO3 (industrial-grade cryolite to Na2CO3 mass ratio 1:2, flux added is 10 wt% of the total mass of aluminum frame and silicon wafer). After the last addition of the silicon wafer and flux mixture, hold at the temperature for 20 minutes. After melting, stir for 3 minutes using electromagnetic combined with argon gas. After the melt is allowed to stand for 1 minute, perform slag removal and pour the melt into a preheated mold at 200℃ to obtain a uniform aluminum-silicon alloy (alloy silicon content of 13.64%) with a hardness of HB108. 91.9% of Al and 90.9% of Si were recovered.

[0048] Example 3 Step 1: Same as Step 1 in Example 1.

[0049] Step 2: Same as Step 2 in Example 1.

[0050] Step 3: The crystalline silicon solar cells separated after pyrolysis are crushed to a size limit of 5mm. They are then immersed in a mixed etching solution (water as solvent) of HNO3 (15wt%), C6H8O7 (7wt%), and HF (6wt%), and etched for 15 minutes at room temperature. After etching, they are rinsed with deionized water until no residue remains and dried in an oven at 120℃ to obtain silicon wafers with a purity of 99.98% for later use. Testing shows that the silver removal rate reaches approximately 99.8%.

[0051] Step 4: Place the aluminum frame in a medium-frequency induction furnace and heat to 1100℃. Then, mix the silicon wafer and flux evenly and gradually add them to the bottom 1 / 3 of the melt through a long tube in three batches, 5 minutes apart. The amount of silicon wafer added is 20 wt% of the aluminum frame. The flux composition is NaF and K2CO3 (NaF to K2CO3 mass ratio 1:2, flux added is 15 wt% of the total mass of aluminum frame and silicon wafer). After the last addition of the silicon wafer and flux mixture, hold at the temperature for 30 minutes. After melting, stir for 4 minutes using a combination of electromagnetic and argon gas. After the melt has settled for 1 minute, perform slag removal and pour the melt into a preheated mold at 250℃ to obtain a homogeneous aluminum-silicon alloy (alloy silicon content of 18.50%) with a hardness of HB138. 92.5% of Al and 91.9% of Si were recovered.

[0052] Comparative Example 1 Step 1: Same as Step 1 in Example 1.

[0053] Step 2: Same as Step 2 in Example 1.

[0054] Step 3: Crush the crystalline silicon solar cells separated after pyrolysis, limiting the size of the crushed cells to within 5mm. Rinse them with deionized water and dry them in an oven at 120℃ for later use.

[0055] Step 4: Place the aluminum frame in a medium-frequency induction furnace and heat to 1100℃. Then, mix the solar cells and flux evenly in three batches, each 5 minutes apart, and gradually add them to the bottom 1 / 3 of the melt through a long tube. The amount of silicon wafer added is 20wt% of the aluminum frame. The flux composition is NaF and K2CO3 (NaF to K2CO3 mass ratio 1:2, flux added is 15wt% of the total of aluminum frame and solar cells). After the last addition of silicon wafers, hold at the temperature for 30 minutes. After melting, stir for 4 minutes using a combination of electromagnetic and argon gas. After the melt is allowed to stand for 1 minute, slag removal is performed. The melt is then cast into a mold preheated to 250℃ to obtain a uniform aluminum-silicon alloy (alloy silicon content of 16.58%) with a hardness of HB65. 83.8% Al and 82.9% Si were recovered.

[0056] Comparative Example 2 Step 1: Same as Step 1 in Example 3.

[0057] Step 2: Same as Step 2 in Example 3.

[0058] Step 3: Same as step 3 in Example 3.

[0059] Step 4: Place the aluminum frame in a medium-frequency induction furnace and heat it to 1100℃ to melt. Then, add the silicon wafer in three batches, 5 minutes apart, through a long tube to the bottom 1 / 3 of the melt. The amount of silicon wafer added is 20wt% of the aluminum frame. After the last addition of silicon wafer, hold the temperature for 30 minutes. After melting, stir for 4 minutes using a combination of electromagnetic and argon gas. After the melt has settled for 1 minute, remove the slag and cast the melt into a preheated mold at 250℃ to obtain a uniform aluminum-silicon alloy (alloy silicon content of 16.02%) with a hardness of HB81. 80.8% of Al and 76.9% of Si were recovered.

[0060] Comparative Example 3 Step 1: Same as Step 1 in Example 3.

[0061] Step 2: Same as Step 2 in Example 3.

[0062] Step 3: Same as step 3 in Example 3.

[0063] Step 4: Place the aluminum frame in a medium-frequency induction furnace and heat it to 1100℃. Then, uniformly mix the silicon wafer and flux, and add them all at once through a long tube to the bottom 1 / 3 of the melt. The amount of silicon wafer added is 20wt% of the mass of the aluminum frame. The flux composition is NaF and K2CO3 (NaF to K2CO3 mass ratio 1:2, flux added is 15wt% of the total of the aluminum frame and silicon wafer). After adding the silicon wafer, hold the temperature for 30 minutes. After melting, stir for 4 minutes using a combination of electromagnetic and argon gas. After the melt has settled for 1 minute, perform slag removal and pour the melt into a preheated mold at 250℃ to obtain an aluminum-silicon alloy (alloy silicon content is 15.98%) with a hardness of HB89. 90.8% of Al and 79.9% of Si were recovered.

[0064] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing aluminum-silicon alloy from recycled decommissioned photovoltaic modules, characterized in that, Includes the following steps: Step 1: Mechanically disassemble the retired photovoltaic modules to obtain aluminum frames and laminates; Step 2: Pyrolyze the laminate to separate the crystalline silicon solar cells; Step 3: The crystalline silicon solar cell is crushed and acid-etched to obtain a silicon wafer; Step 4: Melt the aluminum frame to obtain a melt; mix the silicon wafer with the flux and add it to the melt for smelting and casting to obtain an aluminum-silicon alloy.

2. The method for preparing aluminum-silicon alloy from recycled decommissioned photovoltaic modules according to claim 1, characterized in that, The retired photovoltaic modules are crystalline silicon photovoltaic modules with a service life of 25 to 30 years. They mainly include glass, crystalline silicon cells, backsheet and aluminum frame. The mass fraction of glass in the retired photovoltaic modules is 60% to 75%, the mass fraction of aluminum is 10% to 15%, and the mass fraction of crystalline silicon cells is 2% to 5%.

3. The method for preparing aluminum-silicon alloy from recycled decommissioned photovoltaic modules according to claim 1, characterized in that, In step 2, the pyrolysis conditions are set as follows: pyrolysis at 520~540℃ for 15~20 min under an inert atmosphere.

4. The method for preparing aluminum-silicon alloy from recycled decommissioned photovoltaic modules according to claim 1, characterized in that, In step 3, crush the material to a size no larger than 5mm.

5. The method for preparing aluminum-silicon alloy from recycled decommissioned photovoltaic modules according to claim 1, characterized in that, In step 3, the acid etching conditions are set as follows: the broken crystalline silicon solar cell is immersed in the mixed etching solution and etched at room temperature for 10-15 minutes.

6. The method for preparing aluminum-silicon alloy from recycled decommissioned photovoltaic modules according to claim 5, characterized in that, The mixed etching solution is a mixed aqueous solution of HNO3, C6H8O7 and HF; the content of HNO3 in the mixed etching solution is 10~20wt%, the content of C6H8O7 is 5~10wt%, and the content of HF is 2~10wt%.

7. The method for preparing aluminum-silicon alloy from recycled decommissioned photovoltaic modules according to claim 1, characterized in that, In step 4, the amount of silicon wafer added is 5-20 wt% of the mass of the aluminum frame; the amount of flux added is 5-15 wt% of the total mass of the aluminum frame and the silicon wafer; the flux is a mixture of fluoride and carbonate in a mass ratio of 1:(1-2); the fluoride is cryolite and / or NaF; the carbonate is K2CO3 and / or Na2CO3.

8. The method for preparing aluminum-silicon alloy from recycled decommissioned photovoltaic modules according to claim 1, characterized in that, In step 4, the melting temperature is 900~1100℃. After the silicon wafer and flux are mixed evenly, they are fed into the bottom 1 / 3 of the melt in 3~5 batches through a long tube or feeder. The time interval between each feeding is 5 minutes. After the last feeding, the temperature is maintained for 20~30 minutes.

9. The aluminum-silicon alloy prepared by the method according to any one of claims 1 to 8.

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