Method for recycling silicon powder from waste photovoltaic panels

Abstract

The application relates to the technical field of solid waste recycling, and discloses a method for recycling silicon powder from waste photovoltaic panels, which comprises the following steps: S1, disassembling and crushing the waste photovoltaic panels to obtain glass-containing silicon powder; S2, mixing the glass-containing silicon powder, an adjusting agent and water to perform slurry adjustment, and performing air flotation to obtain rough selection concentrate and rough selection tailings; S3, mixing the rough selection tailings, a collecting agent and a foaming agent to perform slurry adjustment, and performing air flotation to obtain sweep selection concentrate and glass, wherein the sweep selection concentrate is returned to step S2 for rough selection; S4, mixing the rough selection concentrate and the adjusting agent to perform slurry adjustment, and performing air flotation to obtain fine selection silicon material and fine selection tailings; filtering and drying the fine selection silicon material to obtain silicon powder; the adjusting agent in step S2 comprises phosphate and water glass, and the mass of the phosphate is greater than that of the water glass; the adjusting agent in step S4 comprises phosphate and sulfuric acid water glass, and the mass of the phosphate is less than that of the sulfuric acid water glass. Through the technical scheme, the problem that the effect of recycling silicon from waste photovoltaic panels is poor in the prior art is solved.

Description

Technical Field

[0001] This invention relates to the field of solid waste recycling technology, specifically to a method for recycling silicon powder from waste photovoltaic panels. Background Technology

[0002] Photovoltaic power generation is one of the pillars of decarbonization in the power industry, and the rapid development of photovoltaic technology has provided opportunities to reduce carbon emissions and address climate change. However, this development has also brought about a pressing issue: waste management at the end of the photovoltaic panel's life cycle. With the booming development of the photovoltaic industry, the number of waste photovoltaic panels is also increasing daily. On the one hand, waste photovoltaic panels contain renewable resources such as glass, copper, aluminum, silicon, and silver, making their green recycling and reuse economically beneficial. On the other hand, waste photovoltaic panels also contain toxic and harmful substances such as heavy metals like cadmium, which, if improperly handled, can threaten the environment and human health. Therefore, the recycling of waste photovoltaic panels is of great significance.

[0003] Currently, there are three mainstream recycling processes for waste crystalline silicon photovoltaic panels: pyrolysis separation, physical crushing, and chemical leaching. Their recycling principles, advantages, and disadvantages are as follows:

[0004] (1) Pyrolysis separation method:

[0005] Recycling principle: Under high temperature conditions, ethylene-vinyl acetate copolymer (EVA) and organic materials such as the backsheet are softened or even decomposed, achieving separation between the glass, battery cells and backsheet;

[0006] Advantages: Low cost, simple process, and high separation efficiency;

[0007] Disadvantages: Recycling silicon wafers is prone to breakage, consumes a lot of energy, and can easily produce toxic and harmful gases.

[0008] (2) Physical fragmentation method:

[0009] Recycling principle: Using mechanical force to completely crush waste photovoltaic panels;

[0010] Advantages: Low cost, simple operation, and environmentally friendly recycling process;

[0011] Disadvantages: Difficulty in separating recycled materials, low product purity and yield.

[0012] (3) Chemical leaching method:

[0013] Recycling principle: Utilizing the "like dissolves like" principle between organic solvents and EVA, the adhesion between the glass and the battery cells is weakened, achieving the separation of each component; at the same time, the differences in solubility of different substances in acids and alkalis are utilized to achieve the separation of metal elements and silicon wafers;

[0014] Advantages: High recovery rate, good material integrity, and high material purity;

[0015] Disadvantages: The recycling process is lengthy, the amount of acid and alkali used is large, and the amount of "three wastes" (waste gas, wastewater, and solid waste) discharged is large.

[0016] The primary purpose of pyrolysis is to decompose EVA and organic backsheets, achieving efficient separation of glass and silicon wafers, resulting in relatively pure silicon wafers and glass. For intact waste photovoltaic panels, the separation of glass and silicon wafers after pyrolysis is relatively easy. However, for waste photovoltaic panels that break during transportation, installation, use, or dismantling, the separation of the glass-silicon fragment mixture after pyrolysis is less effective. Mechanical processing, while able to separate and recycle glass because it does not effectively remove EVA and backsheets, cannot directly yield complete and clean solar cells from waste photovoltaic panels, resulting in poor silicon recovery. Chemical processing requires large amounts of reagents, has long reaction cycles, and generates waste liquid and gas; if industrialized, it will cause secondary pollution to the environment. Therefore, there is an urgent need for an economical and high-yield method to recover valuable materials, enabling the high-value utilization and resource recycling of waste photovoltaic panels. Summary of the Invention

[0017] This invention proposes a method for recycling silicon powder from waste photovoltaic panels, thereby solving or at least alleviating one or more of the above-mentioned problems and other problems existing in the prior art.

[0018] The technical solution of the present invention is as follows:

[0019] A method for recycling silicon powder from waste photovoltaic panels includes the following steps:

[0020] S1. Dismantling and crushing: Dismantle and crush the waste photovoltaic panels to obtain glass-containing silicon powder;

[0021] S2. Roughing: The glass silica powder, modifier and water are mixed to form a slurry. After the slurry is formed, aeration is performed for flotation to obtain roughing concentrate and roughing tailings.

[0022] S3, Scavenging: The roughing tailings, collector and frother are mixed and slurry is prepared. After the slurry is prepared, aeration is performed for flotation to obtain scavenged concentrate and glass. The scavenged concentrate is returned to step S2 for roughing.

[0023] S4. Fine selection: The coarse and fine materials and the modifier are mixed and slurry is prepared. After slurry preparation, aeration is performed for flotation to obtain fine silicon material and fine tailings. The fine silicon material is filtered and dried to obtain silicon powder.

[0024] The modifier mentioned in step S2 includes phosphate and water glass, wherein the mass of the phosphate is greater than the mass of the water glass;

[0025] The modifier in step S4 includes phosphate and sulfuric acid glass, wherein the mass of the phosphate is less than the mass of the sulfuric acid glass.

[0026] As a further technical solution, the powder particles crushed to a size of less than 0.074 mm account for 65wt% to 90wt%.

[0027] As a further technical solution, the metallic silicon content in the glass-containing silicon powder is 50wt%~60wt%.

[0028] As a further technical solution, the phosphate mentioned in step S2 and / or step S4 includes one or both of sodium pyrophosphate and sodium hexametaphosphate, preferably sodium hexametaphosphate.

[0029] Sodium pyrophosphate, also known as tetrasodium pyrophosphate, possesses the general properties of common phosphates, namely emulsifying and dispersing properties; sodium hexametaphosphate, also known as sodium polyphosphate, is a long-chain polymer with strong dispersing properties. In this invention, one or both of sodium pyrophosphate and sodium hexametaphosphate are selected as phosphates to promote the dispersibility of glass and silicon powder, thereby achieving high-purity recovery of silicon powder.

[0030] As a further technical solution, the mass ratio of phosphate to water glass in step S2 is 3~4:1.

[0031] In this invention, phosphate and water glass at a mass ratio of 3-4:1 are used as modifiers in the roughing process. The synergistic effect of these components ensures the high purity of the ultimately recovered silicon powder. At this mass ratio, phosphate exerts a strong dispersing effect, promoting the dispersion of silicon powder and glass agglomerates. This allows water glass to better act on the glass surface, improving the glass's hydrophilicity. The flotation process effectively separates the silicon powder and glass, laying a high-quality raw material foundation for subsequent refining processes.

[0032] As a further technical solution, the amount of modifier used in step S2 is 50~500g / t, based on the dry weight of glass-containing silica powder.

[0033] As a further technical solution, the mass ratio of phosphate and sulfuric acid water glass in step S4 is 1:4~5.

[0034] In this invention, phosphate and sulfuric acid glass at a mass ratio of 1:4~5 are used as modifiers in the refining process. The synergistic effect of these components ensures the high purity of the ultimately recovered silicon powder. At this mass ratio, the sulfuric acid glass fully exerts its high-selectivity inhibition effect on the glass, while the phosphate provides a certain dispersing effect, ensuring that the sulfuric acid glass can fully contact the glass, ultimately guaranteeing the stable production of high-purity silicon powder.

[0035] As a further technical solution, the amount of modifier used in step S4 is 30~300g / t, based on the dry weight of glass-containing silica powder.

[0036] In this invention, the collector can be any conventional collector in the art, preferably one of diesel oil or kerosene. The foaming agent can be any conventional foaming agent in the art, preferably No. 2 oil.

[0037] As a further technical solution, based on the dry weight of glass silica powder, the amount of collector is 50~100g / t, and the amount of foaming agent is 30~50g / t.

[0038] As a further technical solution, the selection process is performed at least 7 times; when the selection process is performed 7 times, the selected tail material obtained from the first selection is returned to step S2 for coarse selection, the selected tail material obtained from the second and third selections is returned to the first selection, the selected tail material obtained from the fourth and fifth selections is returned to the second selection, and the selected tail material obtained from the sixth and seventh selections is returned to the fourth selection.

[0039] In this invention, selected tailings from different stages are directionally returned for gradient impurity removal and silicon enrichment. This avoids the accumulation of impurities at different stages (coarse, medium, and fine), reducing the separation load, and allows substandard silicon powder to re-participate in the corresponding impurity removal process for thorough removal. Through the synergistic effect of multiple cycles and directional reflux, the purity of silicon powder can be gradually improved, silicon loss can be avoided, and the purity of the recovered silicon powder can be significantly increased in the end.

[0040] As a further technical solution, the phosphate in the first, second, and third selection modifiers is sodium pyrophosphate, and the phosphate in the fourth, fifth, sixth, and seventh selection modifiers is sodium hexametaphosphate.

[0041] In this invention, sodium pyrophosphate is used in the first, second, and third refining processes to prevent silicon powder from being over-dispersed and lost with the tailings; sodium hexametaphosphate is used in the fourth, fifth, sixth, and seventh refining processes to improve the removal of impurities by utilizing its strong dispersing effect, thereby further improving the purity of the recovered silicon powder.

[0042] As a further technical solution, based on the dry weight of glass-containing silica powder, the amount of adjusting agent used in the first fine-tuning process is 30~300g / t; the amount of adjusting agent used in the second fine-tuning process is 30~250g / t; the amount of adjusting agent used in the third fine-tuning process is 30~200g / t; the amount of adjusting agent used in the fourth fine-tuning process is 30~150g / t; the amount of adjusting agent used in the fifth fine-tuning process is 30~100g / t; the amount of adjusting agent used in the sixth fine-tuning process is 30~80g / t; and the amount of adjusting agent used in the seventh fine-tuning process is 30~50g / t.

[0043] The working principle and beneficial effects of this invention are as follows:

[0044] 1. This invention utilizes the difference in hydrophobicity between silicon powder and glass in waste photovoltaic panels to separate and recycle silicon powder and glass using a flotation separation method. This method is not only low-cost and has a short operating cycle, but also highly adaptable to mixtures of glass and silicon powder, with high separation and recycling efficiency, and can obtain high-purity silicon powder and glass products.

[0045] 2. The method for recycling silicon powder from waste photovoltaic panels provided by the present invention uses only a small amount of environmentally friendly flotation reagents in the entire recycling process, without the need to add a large amount of chemical reagents and high-temperature heating treatment, and the flotation return water can be recycled, with no waste gas, waste liquid or solid waste generated, which is environmentally friendly.

[0046] 3. This invention overcomes the technical shortcomings of separating glass and silicon powder mixtures through flotation separation methods and reagent optimization, realizing the resource utilization and high-value utilization of waste photovoltaic panels. In the roughing stage, phosphate and water glass are used as modifiers, ensuring that the mass of phosphate is greater than that of water glass. Simultaneously, in the cleaning stage, phosphate and sulfuric acid water glass are used as modifiers, ensuring that the mass of phosphate is less than that of sulfuric acid water glass, thus improving the purity of the recovered silicon powder. Because the glass content in the roughing raw material is relatively high, the addition of water glass can quickly act on the glass surface, enhancing the hydrophilicity of the glass. Furthermore, the high glass content in the roughing stage makes it prone to agglomeration with silicon powder; the greater mass of phosphate than water glass effectively promotes the dispersion of agglomerates, avoiding mechanical inclusion between silicon powder and glass, which would affect the silicon powder separation effect. In the cleaning stage, the glass content in the raw material is relatively low; the addition of sulfuric acid water glass can selectively inhibit glass growth. Moreover, the dispersion of glass and silicon powder is relatively good in the cleaning stage, and the greater mass of sulfuric acid than phosphate allows for more effective removal of glass, ensuring high purity of the recovered silicon powder. Detailed Implementation

[0047] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0048] In the following embodiments and comparative examples:

[0049] Sulfuric acid water glass: The mass ratio of water glass to sulfuric acid is 5:2, and the modulus of water glass is 2.8;

[0050] Yield (%) = Mass of actual silicon powder obtained ÷ Mass of glass-containing silicon powder × 100%;

[0051] Recovery rate (%) = Yield × actual silicon content in the obtained silicon powder ÷ silicon content in glass-containing silicon powder × 100%.

[0052] Example 1

[0053] A method for recycling silicon powder from waste photovoltaic panels includes the following steps:

[0054] S1. Dismantling and Crushing: The aluminum frame of the waste photovoltaic panel is removed by a frame-removing machine. The glass on the surface of the component after the aluminum frame is removed is peeled off by a peeling machine. The component after the glass is removed is crushed by a crusher to make the component smaller and layered, which facilitates the subsequent screening of the component. The crushed component is screened by a vibrating screen, and various materials are separated according to different specific gravities to obtain solder ribbon particles and glass-containing silicon wafers. The glass-containing silicon wafers are crushed to a particle size of less than 0.074mm, accounting for 65wt%, to obtain glass-containing silicon powder, of which the metallic silicon content is 53.60wt%.

[0055] S2. Roughing: Glass silica powder is fed into a mixing tank and water is added to make a slurry with a solid mass concentration of 30%. A modifier (composed of sodium pyrophosphate and water glass in a mass ratio of 3:1) is added to the slurry for conditioning. The amount of modifier added is 500g / t based on the dry weight of glass silica powder. The slurry is stirred for 5 minutes. After conditioning, the slurry is aerated and floated for 8 minutes to obtain the roughing concentrate and roughing tailings.

[0056] S3, Scavenging: Add diesel oil to the roughing tailings above to adjust the slurry. The amount of diesel oil added is 100g / t based on the dry weight of glass silica powder. The slurry mixing time is 3min. Add No. 2 oil to adjust the slurry. The amount of No. 2 oil added is 50g / t based on the dry weight of glass silica powder. The slurry mixing time is 3min. After the slurry adjustment is completed, aeration is performed for flotation. The flotation time is 5min to obtain scavenging concentrate and glass. The scavenging concentrate is returned to step S2 for roughing.

[0057] S4. Fine Refinement: Add a modifier (composed of sodium pyrophosphate and sulfuric acid water glass in a mass ratio of 1:4) to the above roughing concentrate for slurry preparation. Stir the slurry for 3 minutes. After slurry preparation, aerate and float for 5 minutes to obtain refined silicon material and refined tailings. Perform 7 refinements according to this step. Based on the dry weight of glass-containing silicon powder, the modifier addition amounts for refinement I, II, III, IV, V, VI, and VII are 300 g / t, 250 g / t, 200 g / t, 150 g / t, 100 g / t, 80 g / t, and 50 g / t, respectively. The refined tailings obtained from refinement I are returned to step S2 for roughing. The refined tailings obtained from refinement II and III are returned to refinement I. The refined tailings obtained from refinement IV and V are returned to refinement II. The refined tailings obtained from refinement VI and VII are returned to refinement IV. Filter and dry the refined silicon material from refinement VII to obtain silicon powder. The water obtained after filtration can be reused.

[0058] The final silicon powder yield was 53.81%, the metallic silicon content was 88.23 wt%, and the recovery rate was 88.58%.

[0059] Example 2

[0060] A method for recycling silicon powder from waste photovoltaic panels includes the following steps:

[0061] S1. Dismantling and Crushing: The aluminum frame of the waste photovoltaic panel is removed by a frame-removing machine. The glass on the surface of the component after the aluminum frame is removed is peeled off by a peeling machine. The component after the glass is peeled off is crushed by a crusher to make the component smaller and layered, which facilitates the subsequent screening of the component. The crushed component is screened by a vibrating screen, and various materials are separated according to different specific gravities to obtain solder ribbon particles and glass-containing silicon wafers. The glass-containing silicon wafers are crushed to a particle size of less than 0.074mm, accounting for 90wt%, to obtain glass-containing silicon powder, of which the metallic silicon content is 57.39wt%.

[0062] S2. Roughing: Glass silica powder is fed into a mixing tank and water is added to make a slurry with a solid mass concentration of 30%. A modifier (composed of sodium pyrophosphate and water glass in a mass ratio of 4:1) is added to the slurry for conditioning. The amount of modifier added is 50g / t based on the dry weight of glass silica powder. The slurry is stirred for 5 minutes. After conditioning, the slurry is aerated and floated for 8 minutes to obtain roughing concentrate and roughing tailings.

[0063] S3, Scavenging: Add kerosene to the roughing tailings above to adjust the slurry. The amount of kerosene added is 50g / t based on the dry weight of glass silica powder. The slurry is stirred for 3 minutes. Add No. 2 oil to adjust the slurry. The amount of No. 2 oil added is 30g / t based on the dry weight of glass silica powder. The slurry is stirred for 3 minutes. After the slurry is adjusted, aeration is performed for flotation. The flotation is performed for 5 minutes to obtain scavenged concentrate and glass. The scavenged concentrate is returned to step S2 for roughing.

[0064] S4. Fine Refinement: Add a modifier (composed of sodium pyrophosphate and sulfuric acid water glass in a mass ratio of 1:5) to the above roughing concentrate for slurry preparation. Stir the slurry for 3 minutes. After slurry preparation, aerate and float for 5 minutes to obtain refined silicon material and refined tailings. Perform 7 refinements according to this step. Based on the dry weight of glass-containing silicon powder, the modifier addition amounts for refinement I, II, III, IV, V, VI, and VII are 200 g / t, 150 g / t, 100 g / t, 80 g / t, 50 g / t, 30 g / t, and 30 g / t, respectively. The refined tailings obtained from refinement I are returned to step S2 for roughing. The refined tailings obtained from refinement II and III are returned to refinement I. The refined tailings obtained from refinement IV and V are returned to refinement II. The refined tailings obtained from refinement VI and VII are returned to refinement IV. Filter and dry the refined silicon material from refinement VII to obtain silicon powder. The water obtained after filtration can be reused.

[0065] The final silicon powder yield was 56.67%, the metallic silicon content was 90.18 wt%, and the recovery rate was 89.05%.

[0066] Example 3

[0067] The only difference from Example 1 is that in this example, sodium pyrophosphate in steps S2 and S4 is replaced with an equal amount of sodium hexametaphosphate.

[0068] The final silicon powder yield was 52.68%, the metallic silicon content was 94.01 wt%, and the recovery rate was 92.40%.

[0069] Example 4

[0070] The only difference from Example 3 is that in this example, sodium hexametaphosphate in step S4 (selection I, selection II, and selection III) is replaced with an equal amount of sodium pyrophosphate.

[0071] The final silicon powder yield was 52.97%, the metallic silicon content was 98.23 wt%, and the recovery rate was 97.08%.

[0072] Example 5

[0073] The only difference from Example 3 is that in this example, sodium hexametaphosphate in Selected I and Selected II in step S4 is replaced with an equal amount of sodium pyrophosphate.

[0074] The final silicon powder yield was 53.18%, the metallic silicon content was 94.65 wt%, and the recovery rate was 93.91%.

[0075] Example 6

[0076] The only difference from Example 3 is that in this example, sodium hexametaphosphate in step S4 (selection I, selection II, selection III, and selection IV) is replaced with an equal amount of sodium pyrophosphate.

[0077] The final silicon powder yield was 52.71%, the metallic silicon content was 91.17 wt%, and the recovery rate was 89.66%.

[0078] Comparative Example 1

[0079] The only difference from Example 1 is that in this comparative example, the water glass in step S2 is replaced with an equal amount of sulfuric acid water glass.

[0080] The final silicon powder yield was 51.78%, the metallic silicon content was 88.07 wt%, and the recovery rate was 85.08%.

[0081] Comparative Example 2

[0082] The only difference from Example 1 is that in this comparative example, the sulfuric acid glass in step S4 is replaced with an equal amount of water glass.

[0083] The final silicon powder yield was 57.16%, the metallic silicon content was 80.74 wt%, and the recovery rate was 86.10%.

[0084] Comparative Example 3

[0085] The only difference from Example 1 is that the modifier in step S2 of this comparative example consists of sodium pyrophosphate and water glass in a mass ratio of 1:1.

[0086] The final silicon powder yield was 53.79%, the metallic silicon content was 84.02 wt%, and the recovery rate was 84.32%.

[0087] Comparative Example 4

[0088] The only difference from Example 1 is that the modifier in step S2 of this comparative example consists of sodium pyrophosphate and water glass in a mass ratio of 1:2.

[0089] The final silicon powder yield was 53.24%, the metallic silicon content was 82.80 wt%, and the recovery rate was 82.24%.

[0090] Comparative Example 5

[0091] The only difference from Example 1 is that the modifier in step S4 of this comparative example consists of sodium pyrophosphate and water glass of sulfuric acid in a mass ratio of 1:1.

[0092] The final silicon powder yield was 56.97%, the metallic silicon content was 80.23 wt%, and the recovery rate was 85.27%.

[0093] Comparative Example 6

[0094] The only difference from Example 1 is that the modifier in step S4 of this comparative example consists of sodium pyrophosphate and water glass of sulfuric acid in a mass ratio of 2:1.

[0095] The final silicon powder yield was 57.22%, the metallic silicon content was 78.96 wt%, and the recovery rate was 84.29%.

[0096] As can be seen from the above examples and comparative examples, the silicon content and recovery rate of the silicon powder obtained in Example 1 are higher than those in Comparative Examples 1 to 6. This indicates that phosphate and water glass are used as modifiers during the roughing process, and the mass of phosphate is greater than that of water glass. At the same time, phosphate and sulfuric acid water glass are used as modifiers during the fine selection process, and the mass of phosphate is less than that of sulfuric acid water glass. This improves the purity and recovery rate of the recovered silicon powder.

[0097] Furthermore, the silicon content and recovery rate of the silicon powder obtained in Example 4 were higher than those in the other examples, indicating that when the phosphate in the adjusting agent of the first, second and third selection was sodium pyrophosphate, and the phosphate in the adjusting agent of the fourth, fifth, sixth and seventh selection was sodium hexametaphosphate, the purity and recovery rate of the recovered silicon powder were further improved.

[0098] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recycling silicon powder from waste photovoltaic panels, characterized in that, Includes the following steps: S1. Dismantling and crushing: Dismantle and crush the waste photovoltaic panels to obtain glass-containing silicon powder; S2. Roughing: The glass silica powder, modifier and water are mixed to form a slurry. After the slurry is formed, aeration is performed for flotation to obtain roughing concentrate and roughing tailings. S3, Scavenging: The roughing tailings, collector and frother are mixed and slurry is prepared. After the slurry is prepared, aeration is performed for flotation to obtain scavenged concentrate and glass. The scavenged concentrate is returned to step S2 for roughing. S4. Fine selection: The coarse and fine materials and the modifier are mixed and slurry is prepared. After slurry preparation, aeration is performed for flotation to obtain fine silicon material and fine tailings. The fine silicon material is filtered and dried to obtain silicon powder. The modifier mentioned in step S2 includes phosphate and water glass, wherein the mass ratio of phosphate to water glass is 3~4:1; The modifier mentioned in step S4 includes phosphate and sulfuric acid glass, wherein the mass ratio of phosphate to sulfuric acid glass is 1:4~5; The selection process is performed at least 7 times. When the selection process is performed 7 times, the selected tail material obtained from the first selection is returned to step S2 for coarse selection, the selected tail material obtained from the second and third selections is returned to the first selection, the selected tail material obtained from the fourth and fifth selections is returned to the second selection, and the selected tail material obtained from the sixth and seventh selections is returned to the fourth selection.

2. The method for recycling silicon powder from waste photovoltaic panels according to claim 1, characterized in that, The phosphate mentioned in step S2 and / or step S4 includes one or both of sodium pyrophosphate and sodium hexametaphosphate.

3. The method for recycling silicon powder from waste photovoltaic panels according to claim 1, characterized in that, Based on the dry weight of glass silica powder, the amount of modifier used in step S2 is 50~500g / t.

4. The method for recycling silicon powder from waste photovoltaic panels according to claim 1, characterized in that, Based on the dry weight of glass silica powder, the amount of modifier used in step S4 is 30~300g / t.

5. The method for recycling silicon powder from waste photovoltaic panels according to claim 1, characterized in that, The collector includes one of diesel oil and kerosene.

6. The method for recycling silicon powder from waste photovoltaic panels according to claim 1, characterized in that, Based on the dry weight of glass silica powder, the amount of collector is 50~100g / t, and the amount of foaming agent is 30~50g / t.

7. The method of claim 1, wherein the waste photovoltaic panel is a waste crystalline silicon photovoltaic panel. The phosphate in the first, second, and third selection modifiers is sodium pyrophosphate, and the phosphate in the fourth, fifth, sixth, and seventh selection modifiers is sodium hexametaphosphate.