Method for preparing regenerated silicon from silicon wafer cutting waste
By processing silicon wafer cutting waste through pressure filtration, granulation, and vacuum drying, the problem of uneven drying of silicon sludge was solved, and efficient preparation of recycled silicon was achieved, improving the recovery rate and purity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-11
- Publication Date
- 2026-04-14
AI Technical Summary
In existing technologies, the waste silicon sludge generated from silicon wafer cutting is difficult to dry evenly, resulting in resource waste and reduced recycling rate, and the drying process causes environmental pollution.
Silica mud filter cake is formed by pressure filtration, granulation is carried out to obtain silica mud particles of uniform size, and after drying in a vacuum or inert atmosphere, it is heated to 1450-1600℃. Slagging agents can be used to improve the purity.
This method achieves uniform drying and efficient regeneration of silica mud, resulting in high-purity regenerated silica blocks, reducing resource waste and environmental pollution, and improving the recovery rate.
Abstract
Description
Technical Field
[0001] This application relates to the field of silicon resource recycling technology, and in particular to a method for preparing recycled silicon from silicon wafer cutting waste. Background Technology
[0002] In recent years, the rapid development of the photovoltaic industry has driven a continuous increase in the production of crystalline silicon solar cells. Photovoltaic-grade monocrystalline silicon wafers are the substrate for crystalline silicon solar cells, and their demand is also constantly rising. Photovoltaic silicon wafer cutting is one of the key processing steps in the photovoltaic industry, directly affecting the efficiency and cost of photovoltaic cells. Typically, silicon wafers are cut using a process involving the cutting of monocrystalline silicon rods. These rods undergo drawing, cutting, and polishing steps to become thin sheets, which are then assembled into solar cells. The precision and efficiency of the cutting process are crucial to the final cell's performance and cost. With technological advancements, such as the application of high-efficiency processes like laser cutting and diamond wire sawing, the cutting of photovoltaic silicon wafers has become increasingly precise and energy-efficient.
[0003] Currently, approximately 35% of the high-purity silicon from diamond wire cutting of single-crystal silicon ingots enters the cutting fluid, and the resulting silicon sludge after solid-liquid separation has a water content of 30%-60%. This silicon sludge not only takes up space and is difficult to transport, but also oxidizes due to the small particle size and high reactivity of the cut silicon powder. These factors reduce the recovery rate in subsequent smelting and recycling processes, increasing economic losses.
[0004] The recycling of waste silicon sludge from cutting processes requires a drying process, which can be achieved through traditional natural air drying or machine drying. However, the silicon sludge produced after pressure filtration varies in size, making uniform drying difficult and leading to greater energy loss. Secondly, the drying process generates a large amount of dust, causing environmental pollution and resource waste. Importantly, these drying methods all cause silicon powder oxidation, ultimately reducing the recovery rate after smelting. Therefore, in the current context of the photovoltaic industry's development, effectively reducing this resource waste is crucial. A rationally designed scheme is needed for the recycling of cutting waste to maximize resource recycling. Summary of the Invention
[0005] The purpose of this application is to provide a method for preparing recycled silicon from silicon wafer cutting waste. The waste silicon mud generated from silicon wafer cutting is filtered to form silicon mud filter cake, which is then granulated to obtain silicon mud particles of uniform size. The silicon mud particles are dried and then heated to regenerate, which solves the problems of difficult drying and waste of high-purity silicon in the prior art.
[0006] To achieve one of the above-mentioned objectives, one embodiment of this application provides a method for preparing recycled silicon from silicon wafer cutting waste, comprising the following steps:
[0007] Filtration: The waste generated from silicon wafer cutting is separated by pressure filtration to form silicon sludge filter cake;
[0008] Granulation: The silica mud filter cake is fed into a granulation and forming device for extrusion granulation to obtain silica mud particles;
[0009] Drying: Dry the silica mud particles to constant weight in a vacuum or inert atmosphere;
[0010] Heating regeneration: The dried silica mud particles are heated to 1450-1600℃ to obtain regenerated silica blocks.
[0011] As a further improvement of one embodiment of this application, after the silica mud particles are dried, the silica mud particles are mixed with a slagging agent and then heated for regeneration.
[0012] As a further improvement of one embodiment of this application, the amount of slag-forming agent added is 2 to 10% of the weight of the silica mud particles.
[0013] As a further improvement of one embodiment of this application, the slag-forming agent is calcium oxide.
[0014] As a further improvement of one embodiment of this application, the shape of the silica mud particles is spherical, ellipsoidal, or cylindrical.
[0015] As a further improvement of one embodiment of this application, the silica mud particles are cylindrical in shape, with a diameter of 2 to 20 mm and a length of 5 to 20 mm.
[0016] As a further improvement to one embodiment of this application, the silica mud particles are heated and regenerated at 1450–1600°C for 2–5 hours.
[0017] As a further improvement to one embodiment of this application, the silica mud particles are dried in a vacuum or inert atmosphere until the moisture content is <0.5%.
[0018] As a further improvement to one embodiment of this application, the silica mud particles are dried at a temperature of 80–120°C.
[0019] As a further improvement of one embodiment of this application, the purity of the regenerated silicon block obtained after heating and regeneration is >99.9%.
[0020] One or more technical solutions provided in this application have at least the following technical effects or advantages:
[0021] The method for preparing recycled silicon from silicon wafer cutting waste provided in this application involves pressing and filtering the silicon sludge generated from silicon wafer cutting to form a silicon sludge filter cake, and then granulating the silicon sludge filter cake to obtain silicon sludge particles of uniform size. The silicon sludge particles of uniform size can be dried uniformly during drying. The dried silicon sludge particles are then heated and regenerated to obtain recycled silicon blocks. Detailed Implementation
[0022] The present invention will be described in detail below with reference to specific embodiments, but these embodiments do not limit the present invention. Any changes in reaction conditions, reactants or raw material amounts made by those skilled in the art based on these embodiments are included within the protection scope of the present invention.
[0023] This application provides a method for preparing recycled silicon from silicon wafer cutting waste, including the following steps:
[0024] Filtration: The waste silica sludge generated from cutting silicon wafers is filtered by pressure to form silica sludge filter cake;
[0025] Granulation: The silica mud filter cake is fed into a granulation and forming device for extrusion granulation to obtain silica mud particles;
[0026] Drying: Dry the silica mud particles to constant weight in a vacuum or inert atmosphere;
[0027] Heating regeneration: The dried silica mud particles are heated to 1450-1600℃ to obtain regenerated silica blocks.
[0028] During silicon wafer dicing, a large amount of waste silica sludge containing silicon powder and cutting fluid is generated. This waste silica sludge is first treated by pressure filtration to remove excess liquid and form a silica sludge filter cake. This step is crucial for the subsequent granulation process, directly affecting the shape and size of the silica sludge particles, and consequently, the efficiency of drying and thermal regeneration. The silica sludge filter cake is then fed into a granulation device for extrusion granulation. In this step, the silica sludge filter cake is extruded into silica sludge particles of uniform size and regular shape, ensuring uniform drying. The granulated silica sludge particles need to be dried to constant weight in a vacuum or inert atmosphere. The purpose of this step is to ensure that moisture is completely removed from the particles to prevent the generation of unnecessary steam and other gases during thermal regeneration, which could affect the purity of the silicon and heating efficiency. The dried silica sludge particles are heated to 1450–1600°C to obtain regenerated silicon blocks. Within this temperature range, the silicon and other useful components in the silica sludge particles are melted, while impurities are separated from the silicon in other ways.
[0029] In some embodiments, after the silica sludge particles are dried, they are mixed with a slagging agent and then heated for regeneration. The slagging agent reduces the viscosity of the slagging agent and increases its fluidity, making it easier to separate the slagging agent from the molten silicon. After the silica sludge particles are heated and melted, the slagging agent reacts with impurities in the silica sludge to form compounds insoluble in silicon, which form on the surface of the liquid silicon. After the heating regeneration is completed, the regenerated silicon block with impurities on its surface is cooled to room temperature, and the impurities on the surface of the regenerated silicon block are removed to obtain a high-purity regenerated silicon block.
[0030] In some embodiments, the amount of slagging agent added is 2 to 10% of the weight of the silica mud particles. The addition of the slagging agent helps to separate impurities in the silica mud from silicon, and the amount added does not need to be very high.
[0031] In some embodiments, the slagging agent is calcium oxide, a common slagging agent that reacts with impurities in silicon, such as aluminum, calcium, and iron, to form compounds insoluble in silicon, thereby effectively removing these impurities and improving the purity of silicon. Compared to other slagging agents, calcium oxide can react rapidly with impurities at high temperatures, shortening refining time and thus reducing energy consumption.
[0032] In some embodiments, the silica mud particles are spherical, ellipsoidal, or cylindrical in shape. Spherical, ellipsoidal, and cylindrical particles exhibit more uniform pressure distribution, more stable structures, and are less prone to breakage, thus preventing the generation of fine powder during drying, which would be detrimental to the stability and safety of the drying process. Furthermore, their higher stacking density results in higher efficiency during heat regeneration.
[0033] In some embodiments, the silica mud particles are cylindrical in shape, with a diameter of 2–20 mm and a length of 5–20 mm. A diameter of 2–20 mm makes drying easier, preventing the outer surface from drying while the center retains more moisture; a length of 5–20 mm makes it less likely for the particles to break apart and produce powder.
[0034] In some embodiments, the silica mud particles are heated and regenerated at 1450–1600°C for 2–5 hours, depending on the size of the silica mud particles and the type and content of impurities.
[0035] In some embodiments, the silica mud particles are dried in a vacuum or inert atmosphere until the moisture content is <0.5%.
[0036] In some embodiments, the silica sludge particles are dried at a temperature of 80–120°C to ensure sufficient removal of moisture without causing thermal damage to the silica particles. The dried silica sludge particles are then dried in a vacuum or inert atmosphere until the moisture content is <0.5% to prevent residual moisture from contaminating the silica during high-temperature heating.
[0037] In some embodiments, the purity of the regenerated silicon block obtained after heating and regeneration is >999%, which demonstrates the high efficiency of the method for preparing regenerated silicon from silicon wafer cutting waste provided in this application in removing impurities and recovering high-purity silicon.
[0038] The technical solution of this application will be further described below with reference to some specific embodiments.
[0039] Example 1
[0040] Filtration: The waste silica sludge generated from cutting silicon wafers is filtered by pressure to form silica sludge filter cake.
[0041] Granulation: The silica mud filter cake is directly added to the ring die granulator and granulated to obtain cylindrical silica mud particles, wherein the diameter of the cylindrical silica mud particles is 5mm and the length is 10mm.
[0042] Drying: The cylindrical silica mud particles are placed in a dryer and dried until the moisture content is <0.5%. The drying temperature is 80℃ and the drying atmosphere is argon.
[0043] Heating regeneration: The dried silica mud particles are filled into a crucible and placed in a furnace for heating. The heating temperature is 1500℃, the heating time is 2 hours, and an argon atmosphere is used.
[0044] After the silica mud particles have completely melted, heating is stopped, and the mixture is allowed to cool naturally to room temperature to obtain recycled silicon blocks with a purity >99.9%.
[0045] Example 2
[0046] Filtration: The waste silica sludge generated from cutting silicon wafers is filtered by pressure to form silica sludge filter cake.
[0047] Granulation: The silica mud filter cake is directly added to the ring die granulator and granulated to obtain cylindrical silica mud particles, wherein the cylindrical silica mud particles have a diameter of 5mm and a length of 10mm.
[0048] Drying: The cylindrical silica mud particles are placed in a dryer and dried to constant weight. The drying temperature is 80℃ and the drying atmosphere is argon.
[0049] Heating regeneration: The dried silica mud particles and calcium oxide are filled into a crucible at a mass ratio of silica mud particles to calcium oxide of 20:1, and then heated in a furnace. The heating temperature is 1500℃, the heating time is 2 hours, and an argon atmosphere is used.
[0050] After the silica sludge particles have completely melted, heating is stopped, and the mixture is allowed to cool naturally to room temperature. The silica slag portion is then manually sorted to obtain recycled silicon blocks with a purity >99.99%.
[0051] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
[0052] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of this application and are not intended to limit the scope of protection of this application. All equivalent implementation methods or modifications made without departing from the spirit of the art of this application should be included within the scope of protection of this application.
Claims
1. A method for preparing recycled silicon from silicon wafer cutting waste, characterized in that, Includes the following steps: Filtration: The waste generated from silicon wafer cutting is separated by pressure filtration to form silicon sludge filter cake; Granulation: The silica mud filter cake is fed into a granulation and forming device for extrusion granulation to obtain silica mud particles; Drying: Dry the silica mud particles to constant weight in a vacuum or inert atmosphere; Heating regeneration: The dried silica mud particles are heated to 1450-1600℃ to obtain regenerated silica blocks.
2. The method for preparing recycled silicon from silicon wafer cutting waste according to claim 1, characterized in that, After the silica mud particles are dried, they are mixed with a slagging agent and then heated for regeneration.
3. The method for preparing recycled silicon from silicon wafer cutting waste according to claim 2, characterized in that, The amount of slag-forming agent added is 2-10% of the weight of the silica mud particles.
4. The method for preparing recycled silicon from silicon wafer cutting waste according to claim 2, characterized in that, The slag-forming agent is calcium oxide.
5. The method for preparing recycled silicon from silicon wafer cutting waste according to claim 1, characterized in that, The silica mud particles are spherical, ellipsoidal, or cylindrical in shape.
6. The method for preparing recycled silicon from silicon wafer cutting waste according to claim 5, characterized in that, The silica mud particles are cylindrical in shape, with a diameter of 2–20 mm and a length of 5–20 mm.
7. The method for preparing recycled silicon from silicon wafer cutting waste according to claim 1, characterized in that, The silica mud particles are regenerated by heating at 1450–1600℃ for 2–5 hours.
8. The method for preparing recycled silicon from silicon wafer cutting waste according to claim 1, characterized in that, The silica mud particles are dried in a vacuum or inert atmosphere until the moisture content is <0.5%.
9. The method for preparing recycled silicon from silicon wafer cutting waste according to claim 1, characterized in that, The silica mud particles are dried at a temperature of 80–120°C.
10. The method for preparing recycled silicon from silicon wafer cutting waste according to any one of claims 1 to 9, characterized in that, The purity of the regenerated silicon block obtained after heating and regeneration is >99.9%.