Waste crystalline silicon photovoltaic module recovery method based on pyrolysis and dense medium separation

Abstract

The invention discloses a waste crystalline silicon photovoltaic module recovery method based on pyrolysis and dense medium separation, which effectively removes organic matters such as ethylene-vinyl acetate (EVA), backboards and the like in a photovoltaic module through pyrolysis, and utilizes the density difference of silicon wafers, glass and solder strips in the pyrolyzed waste photovoltaic module to accurately blend different dense media to recover the photovoltaic module. The suspension liquid with different density gradients is formed, and efficient separation of the silicon wafer, the glass and the welding strip is achieved. And heavy medium residues on the surface of the material are further removed through a wet sieve, and finally the pure recycled material is obtained. According to the method, the recovery efficiency of the silicon wafers, the glass and the welding strips is ensured to exceed 99%, and the utilization efficiency and the resource recovery level of valuable materials are remarkably improved. According to the technical scheme, the technological process is simple and efficient in design, the recovery treatment cost is greatly reduced, and environment friendliness is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of recycling waste photovoltaic modules, and in particular to a resource recycling method applicable to various waste crystalline silicon photovoltaic modules. Technical Background

[0002] Photovoltaic power generation is one of the pillars of decarbonization in the power industry. The rapid development of photovoltaic technology has provided unprecedented opportunities for reducing carbon emissions and addressing climate change. However, this progress has also brought about an urgent problem that needs to be solved, namely, waste management at the end of the life cycle of photovoltaic modules. With the vigorous development of the photovoltaic industry, the amount of scrapped photovoltaics has also increased sharply. By 2050, the world will generate a total of 78 million tons of photovoltaic module waste. On the one hand, waste photovoltaic modules contain renewable resources such as glass, copper, aluminum, silicon and silver, so their green recycling and reuse has certain economic benefits; on the other hand, waste photovoltaic modules also contain toxic and harmful substances such as heavy metal cadmium. If improperly handled, they will pose a threat to the environment and human health. Therefore, the recycling of waste photovoltaic modules is of great significance.

[0003] At present, waste photovoltaic modules are generally recycled by pyrolysis, chemical treatment and mechanical treatment. Chemical treatment requires a large amount of reagents, has a long reaction cycle and is accompanied by the generation of waste liquid and waste gas. Once it enters industrial production, it will cause secondary pollution to the environment; mechanical treatment stratification does not effectively remove EVA and backplane, although it can separate and recycle glass, it is impossible to directly obtain complete and clean solar cells from the module; the main purpose of pyrolysis is to decompose EVA and organic backplane to achieve efficient separation of glass and silicon wafers, and the obtained silicon wafers and glass are relatively pure. It is worth noting that for complete modules, it is easier to separate glass and silicon wafers after pyrolysis. However, for modules that are broken during transportation, installation, use, and disassembly, the separation technology of the mixture of glass and silicon fragments after pyrolysis is not yet mature. Therefore, there is an urgent need for a method to economically recover valuable materials and realize high-value utilization and resource recovery of waste photovoltaic modules. Summary of the invention

[0004] Technical problem: The purpose of the present invention is to overcome the shortcomings of the prior art and to provide a method for recycling waste crystalline silicon photovoltaic modules based on pyrolysis and heavy medium separation, which has a simple process flow, is easy to operate, improves the recovery rate of valuable materials, and has efficient utilization and resource recovery.

[0005] Technical solution: To achieve the above purpose, the present invention provides a method for recycling waste crystalline silicon photovoltaic modules based on pyrolysis and heavy medium separation, wherein waste photovoltaic module laminates are obtained by disassembly, the waste photovoltaic module laminates are cut and placed in an atmosphere furnace, and heated in a nitrogen atmosphere to obtain a mixture of silicon wafers, glass, and solder strips, and these materials are effectively separated after heavy medium separation; the specific steps are as follows:

[0006] a. Dismantle the discarded crystalline silicon photovoltaic modules, remove the aluminum frame and the junction box to obtain the photovoltaic laminate, and then cut the laminate;

[0007] b. Place the cut laminate into an atmosphere furnace, extract the air in the atmosphere furnace through a vacuum pump to keep the furnace oxygen-free, then introduce nitrogen to heat the atmosphere furnace, set the temperature and maintain a constant temperature for a period of time;

[0008] c. After the constant temperature stage, stop introducing nitrogen and tighten the atmosphere furnace inlet and outlet valves to keep the atmosphere furnace oxygen-free until the temperature cools to room temperature, and collect the mixed products of silicon wafers, glass, and solder strips of the waste photovoltaic modules after pyrolysis;

[0009] d. Use different types of weighting materials to prepare heavy medium suspensions of different densities, and put the mixed products of pyrolyzed silicon wafers, glass, and solder strips into the prepared heavy medium suspensions for sorting. The separation efficiency of silicon wafers, glass, and solder strips is as high as 99%;

[0010] e. The silicon wafers, glass and solder strips obtained from the heavy medium sorting are wet screened respectively to remove the heavy medium residues on them, thereby realizing the recycling of waste crystalline silicon photovoltaic module resources.

[0011] In step b, the flow rate of the nitrogen gas is 200-600 mL / min, and the rate of heating the atmosphere furnace is 8-12° C. / min.

[0012] In step b, when the temperature of the atmosphere furnace reaches 450-650° C., the constant temperature is maintained for 60-120 minutes.

[0013] In step d, the different types of weighting materials are nickel powder, magnetite powder, or ferrosilicon powder; and the passing rate of the weighting material particles through a 200-mesh sieve is more than 70%.

[0014] In step d, the density of the heavy medium suspension with different densities is 2.3-2.7 kg / m 3 .

[0015] In step e, the sieve size of the silicon wafer, glass and solder strip for wet screening is 0.1-0.2 mm, the water flow rate is 0.6-1.0 m / s, and the flushing time is 2-6 min.

[0016] Beneficial effects: The present invention is based on pyrolysis and heavy medium sorting technology, aiming to achieve efficient recovery and reuse of waste photovoltaic module materials. Due to the adoption of the above technical solution, the process will be simpler and easier to operate, achieving efficient utilization and resource recovery of valuable materials in waste photovoltaic modules. During the sorting process, the heavy medium can be used repeatedly; and it is not limited to a certain type of waste photovoltaic modules, but is applicable to various types of crystalline silicon modules, including a mixture of silicon wafers, glass and solder strips of different particle sizes produced after pyrolysis. Compared with the prior art, it has the following advantages:

[0017] (1) Heavy media is used to sort photovoltaic modules after pyrolysis, which achieves effective separation of silicon wafers, glass, and solder strips. The heavy media can be reused, which not only reduces the consumption of raw materials, but also reduces the overall operating costs.

[0018] (2) Wide applicability. The heavy medium separation technology does not discriminate the type of photovoltaic modules. Both monocrystalline silicon photovoltaic modules and polycrystalline silicon photovoltaic modules can be efficiently separated by this technology. In addition, for the mixture of different particle sizes produced after the pyrolysis process, this technology also shows excellent applicability and flexibility, ensuring the high-value utilization of different photovoltaic module materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the technical process of the present invention.

[0020] Figure 2 This is a product effect diagram of the crystalline silicon photovoltaic module after heavy medium sorting of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described below with reference to the embodiments in the accompanying drawings:

[0022] like Figure 1 As shown, the method for recycling waste crystalline silicon photovoltaic modules based on pyrolysis and heavy medium separation of the present invention obtains waste photovoltaic module laminates by disassembling, cuts the waste photovoltaic module laminates and puts them into an atmosphere furnace, heats them in a nitrogen atmosphere, obtains a mixture of silicon wafers, glass, and solder strips, and realizes effective separation of these materials after heavy medium separation; the specific steps are as follows:

[0023] a. Remove the aluminum frame of the discarded crystalline silicon photovoltaic module manually or mechanically, remove the junction box by cutting with a blade, obtain a photovoltaic laminate, and then cut the laminate;

[0024] b. Place the cut laminate into an atmosphere furnace, extract the air in the atmosphere furnace through a vacuum pump to keep the furnace in an oxygen-free state, then introduce nitrogen to heat the atmosphere furnace, and maintain a constant temperature for a period of time after setting the temperature; the flow rate of the nitrogen is 200-600mL / min, and the rate of heating the atmosphere furnace is 8-12℃ / min; when the temperature of the atmosphere furnace reaches 450-650℃, maintain the constant temperature for 60-120min.

[0025] c. After the constant temperature stage, stop introducing nitrogen and tighten the atmosphere furnace inlet and outlet valves to keep the atmosphere furnace oxygen-free until the temperature cools to room temperature, and collect the mixed products of silicon wafers, glass, and solder strips of the waste photovoltaic modules after pyrolysis;

[0026] d. Using different types of weighting materials to prepare heavy medium suspensions of different densities, the mixed products of pyrolyzed silicon wafers, glass, and solder strips are placed in the prepared heavy medium suspensions for sorting, and the separation efficiency of silicon wafers, glass, and solder strips is as high as 99%; the different types of weighting materials are nickel powder, magnetite powder, or ferrosilicon powder; the passing rate of the weighting material particles through a 200-mesh sieve is more than 70%; the density of the heavy medium suspensions with different densities is 2.3-2.7kg / m 3 .

[0027] e. Wet-screen the silicon wafers, glass and solder strips obtained by heavy medium sorting respectively, remove the heavy medium residues on them, and realize the recycling of waste crystalline silicon photovoltaic module resources. The sieve size of the wet-screened silicon wafers, glass and solder strips is 0.1-0.2mm, the water flow rate is 0.6-1.0m / s, and the flushing time is 2-6min.

[0028] Embodiment 1

[0029] a. Remove the aluminum frame of the discarded monocrystalline silicon photovoltaic module manually or mechanically, remove the junction box by cutting with a blade, obtain a photovoltaic laminate, and then cut the laminate;

[0030] b. Place the cut laminate into an atmosphere furnace, extract the air in the atmosphere furnace by a vacuum pump to keep the furnace oxygen-free, then introduce nitrogen, heat the atmosphere furnace, set the temperature and maintain a constant temperature for a period of time; the flow rate of the nitrogen is 200 mL / min, and the rate of heating the atmosphere furnace is 10°C / min; when the temperature of the atmosphere furnace reaches 500°C, maintain the constant temperature for 60 minutes;

[0031] c. After the constant temperature stage, stop introducing nitrogen and tighten the atmosphere furnace inlet and outlet valves to keep the atmosphere furnace oxygen-free until the temperature cools to room temperature, and collect the mixed products of silicon wafers, glass, and solder strips of the waste photovoltaic modules after pyrolysis;

[0032] d. Use different types of weighting materials to prepare heavy medium suspensions of different densities, and put the pyrolyzed silicon wafers, glass, and solder strip mixed products into the prepared heavy medium suspensions for sorting; the weighting material is nickel powder, and the passing rate of nickel powder particles on a 200-mesh sieve exceeds 70%. ; The silicon wafer, glass, and solder strip mixed product, the feed amount is 500g, and the feed speed is 300g / s; the density of the heavy medium suspensions of different densities is 2.3kg / m 3 , 2.7kg / m 3 The heavy medium suspension volume is 1500ml, the stirring speed is 150rpm, and the 3 The silicon wafer floats up, while the glass and solder ribbon sink. Then, the sunken glass and solder ribbon are transferred to the 2.7kg / m 3 In the suspension of high density, they are effectively separated, and the separation efficiency of silicon wafers, glass and solder strips is as high as 99%;

[0033] e. The silicon wafers, glass and solder strips obtained by heavy medium sorting are wet-screened respectively to remove the nickel powder residue on the products; the silicon wafers, glass and solder strips are wet-screened respectively, the sieve size is 0.1mm, the water flow rate is 0.6m / s, and the flushing time is 2min.

[0034] Embodiment 2

[0035] a. Remove the aluminum frame of the discarded polycrystalline silicon photovoltaic modules manually or mechanically, remove the junction box by cutting with a blade, obtain a photovoltaic laminate, and then cut the laminate;

[0036] b. Place the cut laminate into an atmosphere furnace, extract the air in the atmosphere furnace by a vacuum pump to keep the furnace oxygen-free, then introduce nitrogen, heat the atmosphere furnace, set the temperature and maintain a constant temperature for a period of time; the flow rate of the nitrogen is 300 mL / min, and the rate of heating the atmosphere furnace is 12°C / min; when the temperature of the atmosphere furnace reaches 550°C, maintain the constant temperature for 80 minutes;

[0037] c. After the constant temperature stage, stop introducing nitrogen and tighten the atmosphere furnace inlet and outlet valves to keep the atmosphere furnace oxygen-free until the temperature cools to room temperature, and collect the mixed products of silicon wafers, glass, and solder strips of the waste photovoltaic modules after pyrolysis;

[0038] d. Use different types of weighting materials to prepare heavy medium suspensions of different densities, and put the pyrolyzed silicon wafers, glass, and solder strip mixed products into the prepared heavy medium suspensions for sorting; the weighting material is ferrosilicon powder, and the passing rate of ferrosilicon powder particles on a 200-mesh sieve exceeds 70%. The feed amount of the silicon wafer, glass, and solder strip mixed product is 600g, and the feed speed is 320g / s; the density of the heavy medium suspensions with different densities is 2.4kg / m 3 , 2.6kg / m 3 The heavy medium suspension volume is 1500ml, the stirring speed is 200rpm, and the 3 The silicon wafer floats up, while the glass and solder ribbon sink. Then, the sunken glass and solder ribbon are transferred to the 2.6kg / m 3 In the suspension of high density, they are effectively separated, and the separation efficiency of silicon wafers, glass and solder strips is as high as 99%;

[0039] e. The silicon wafers, glass and solder strips obtained by heavy medium sorting are wet-screened respectively to remove the residual ferrosilicon powder on the products; the silicon wafers, glass and solder strips are wet-screened respectively, the sieve size is 0.15mm, the water flow rate is 0.6m / s, and the flushing time is 3min.

[0040] Embodiment 3

[0041] a. Remove the aluminum frame of the discarded monocrystalline silicon photovoltaic module manually or mechanically, remove the junction box by cutting with a blade, obtain a photovoltaic laminate, and then cut the laminate;

[0042] b. Place the cut laminate into an atmosphere furnace, extract the air in the atmosphere furnace by a vacuum pump to keep the furnace oxygen-free, then introduce nitrogen, heat the atmosphere furnace, set the temperature and maintain a constant temperature for a period of time; the flow rate of the nitrogen is 200 mL / min, and the rate of heating the atmosphere furnace is 10°C / min; when the temperature of the atmosphere furnace reaches 500°C, maintain the constant temperature for 60 minutes;

[0043] c. After the constant temperature stage, stop introducing nitrogen and tighten the atmosphere furnace inlet and outlet valves to keep the atmosphere furnace oxygen-free until the temperature cools to room temperature, and collect the mixed products of silicon wafers, glass, and solder strips of the waste photovoltaic modules after pyrolysis;

[0044] d. Use different types of weighting materials to prepare heavy medium suspensions of different densities, and put the pyrolyzed silicon wafers, glass, and solder strip mixed products into the prepared heavy medium suspensions for sorting; the weighting material is ferrosilicon powder, and the passing rate of ferrosilicon powder particles on a 200-mesh sieve exceeds 70%. The feed amount of the silicon wafer, glass, and solder strip mixed product is 700g, and the feed speed is 350g / s; the density of the heavy medium suspensions with different densities is 2.3kg / m 3 , 2.7kg / m 3 The heavy medium suspension volume is 1600 ml, the stirring speed is 150 rpm, and the 3 The silicon wafer floats up, while the glass and solder ribbon sink. Then, the sunken glass and solder ribbon are transferred to the 2.7kg / m 3 In the suspension of high density, they are effectively separated, and the separation efficiency of silicon wafers, glass and solder strips is as high as 99%;

[0045] e. The silicon wafers, glass and solder strips obtained by heavy medium sorting are wet-screened respectively to remove the residual ferrosilicon powder on the products; the silicon wafers, glass and solder strips are wet-screened respectively, the sieve size is 0.1mm, the water flow rate is 0.6m / s, and the flushing time is 4min.

Claims

1. A method for recycling waste crystalline silicon photovoltaic modules based on pyrolysis and heavy medium separation, characterized in that: Obtain waste photovoltaic module laminates by disassembling, cut the waste photovoltaic module laminates and put them into an atmosphere furnace, heat them in a nitrogen atmosphere, obtain a mixture of silicon wafers, glass and solder strips, and effectively separate these materials after heavy medium sorting; the specific steps are as follows: a. Dismantle the discarded crystalline silicon photovoltaic modules, remove the aluminum frame and the junction box to obtain the photovoltaic laminate, and then cut the laminate; b. Place the cut laminate into an atmosphere furnace, extract the air in the atmosphere furnace through a vacuum pump to keep the furnace oxygen-free, then introduce nitrogen to heat the atmosphere furnace, set the temperature and maintain a constant temperature for a period of time; c. After the constant temperature stage, stop introducing nitrogen and tighten the atmosphere furnace inlet and outlet valves to keep the atmosphere furnace oxygen-free until the temperature cools to room temperature, and collect the mixed products of silicon wafers, glass, and solder strips of the waste photovoltaic modules after pyrolysis; d. Use different types of weighting materials to prepare heavy medium suspensions of different densities, and put the mixed products of pyrolyzed silicon wafers, glass, and solder strips into the prepared heavy medium suspensions for sorting. The separation efficiency of silicon wafers, glass, and solder strips is as high as 99%; e. The silicon wafers, glass and solder strips obtained from the heavy medium sorting are wet screened respectively to remove the heavy medium residues on them, thereby realizing the recycling of waste crystalline silicon photovoltaic module resources.

2. The method for recycling waste crystalline silicon photovoltaic modules based on pyrolysis and heavy medium separation according to claim 1, characterized in that: In step b, the flow rate of the nitrogen gas is 200-600 mL / min, and the rate of heating the atmosphere furnace is 8-12° C. / min.

3. The method for recycling waste crystalline silicon photovoltaic modules based on pyrolysis and heavy medium separation according to claim 1, characterized in that: In step b, when the temperature of the atmosphere furnace reaches 450-650° C., the constant temperature is maintained for 60-120 minutes.

4. The method for recycling waste crystalline silicon photovoltaic modules based on pyrolysis and heavy medium separation according to claim 1, characterized in that: In step d, the different types of weighting materials are nickel powder, magnetite powder, or ferrosilicon powder; and the passing rate of the weighting material particles through a 200-mesh sieve is more than 70%.

5. The method for recycling waste crystalline silicon photovoltaic modules based on pyrolysis and heavy medium separation according to claim 1, characterized in that: In step d, the density of the heavy medium suspension with different densities is 2.3-2.7 kg / m 3 .

6. The method for recycling waste crystalline silicon photovoltaic modules based on pyrolysis and heavy medium separation according to claim 1, characterized in that: In step e, the sieve size of the silicon wafer, glass and solder strip for wet screening is 0.1-0.2 mm, the water flow rate is 0.6-1.0 m / s, and the flushing time is 2-6 min.

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