Method and system for filtering and recycling rare earth metal polishing dust
By utilizing the density difference between rare earth metal dust and polishing disc particles through multi-stage sedimentation and centrifugal separation, the efficient recovery and purification of rare earth metal dust is achieved, solving the separation difficulties in existing technologies and improving the purity of the electrolytic cell and the enterprise's efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-16
- Publication Date
- 2026-03-13
AI Technical Summary
Existing technologies are insufficient to effectively separate rare earth metal particles from polishing dust and particles falling off the polishing pad, resulting in contamination of the electrolytic cell during reprocessing and low purification levels.
A multi-stage sedimentation and centrifugal separation method is adopted. By adjusting the ratio of high-density diluent and water, and combining multi-stage sedimentation tanks and centrifuges, the dust density difference is used for separation. Finally, the powder is dried to obtain high-purity rare earth metal powder.
It has achieved efficient recovery and purification of rare earth metal dust, significantly reduced pollution in electrolytic cells, and improved the economic benefits of enterprises.
Smart Images
Figure CN121648672A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a rare earth metal processing waste recycling system, and more specifically, to a method and system for filtering and recycling rare earth metal polishing dust. Background Technology
[0002] Rare earth metal blocks obtained after the electrolysis of rare earth metal powder have a relatively rough surface and contain many impurities. To remove these impurities and improve the appearance of the rare earth metal blocks, the surface is typically polished. The polishing dust produced after polishing contains some rare earth metal particles. Currently, this dust is often placed in water to settle and remove floating matter, and the resulting precipitate is then recycled. However, this dust also contains a large number of particles shed from the polishing discs. These particles are roughly the same size as the dust particles from polishing the rare earth metal blocks, making them difficult to distinguish. Furthermore, these particles are denser than water; for example, polishing discs are generally made of silicon carbide, and the density of the shed particles is around 3 g / cm³. 3 Therefore, the dust obtained after precipitation still contains a significant amount of impurities, and reprocessing it would cause pollution to the electrolytic cell. Thus, there is an urgent need for a method to filter and recover rare earth metal polishing dust to further purify it. Summary of the Invention
[0003] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a method and system for filtering and recovering rare earth metal polishing dust, which realizes the recovery of rare earth metal minerals in the dust and achieves higher purity of rare earth metal minerals in the recovered material.
[0004] The present invention discloses a method for filtering and recovering rare earth metal polishing dust, which includes the following steps: Step 1: Add the recovered rare earth metal polishing dust to a certain amount of water and stir to obtain a premixed solution; Step 2: Remove impurities from the premixed liquid; Step 3: Dilute the premixed solution after impurity removal to obtain the liquid to be precipitated; Step 4: Perform multi-stage precipitation filtration on the liquid to be precipitated, and collect the precipitate mixture except for the last stage precipitate as the target precipitate mixture. Return the precipitate mixture of the last stage precipitate to Step 2 for mixing and impurity removal with the premixed liquid. Step 5: Centrifuge the target precipitate mixture to obtain the target precipitate; Step 6: Dry the target precipitate to obtain a solidified rare earth metal powder.
[0005] Preferably, in step four, the multi-stage sedimentation and filtration process specifically includes: The liquid to be settled is transported to a sedimentation tank equipped with multiple sedimentation tanks. Each sedimentation tank is equipped with an inverted V-shaped seat. The input direction of the liquid to be settled in each sedimentation tank is towards the upper middle part of the corresponding seat, so that the liquid to be settled flows towards and impacts the seat, forming a water flow direction that is a mainstream direction towards the top of the seat and a sedimentation flow direction towards the bottom of the seat. The sedimentation flow direction results in a sedimentation mixture.
[0006] Preferably, a cooling system is provided in the sedimentation tank to maintain the water temperature in the sedimentation tank within a set temperature range.
[0007] Preferably, the temperature range is 4-10℃.
[0008] Preferably, in step three, the specific method for diluting the premixed solution after impurity removal is as follows: Water and sodium chloride are mixed in a set ratio to obtain a high-density diluent. The high-density diluent is then mixed with a premixed solution in a set ratio to obtain the liquid to be precipitated.
[0009] Preferably, the ratio of water to sodium chloride is 1:0.2 to 1:0.3.
[0010] Preferably, the ratio of the premixed liquid to the high-density diluent is 1:7 to 1:10.
[0011] Preferably, the liquid to be settled is pre-cooled before being fed into the sedimentation tank.
[0012] A recycling system for implementing the aforementioned rare earth metal polishing dust filtration and recycling method includes: A mixing tank is used to mix and process the recovered rare earth metal polishing dust after water has been added, forming a premixed liquid. An air flotation tank is used to remove impurities from the premixed liquid. It is equipped with an air plate with multiple micropores. The air plate has a premixed liquid inlet above it and a premixed liquid outlet below it. A sedimentation tank is used for multi-stage sedimentation and filtration of the liquid to be settled. It includes multiple sedimentation tanks, each containing a fixed inverted V-shaped seat. The top of each seat has an arc-shaped structure. A flow-guiding baffle is provided between two adjacent seats, extending from the top of the sedimentation tank downwards to the bottom, reaching a position horizontally corresponding to the upper middle part of the seat. The first sedimentation tank has an inlet for the liquid to be settled, facing the upper middle part of the seat in the first sedimentation tank. The last sedimentation tank is connected to a flotation tank via a return pipe, and both the last and last sedimentation tanks are connected to the input port of a centrifuge. A centrifuge is used to centrifuge the target precipitate mixture. A drying device for drying the target precipitate.
[0013] Preferably, a premixing tank is provided between the flotation tank and the sedimentation tank, and a cooler is installed in the premixing tank; a cooler is installed on the flow guide baffle in the sedimentation tank.
[0014] Beneficial effects The advantages of this invention are: 1. This invention involves preparing rare earth metal polishing dust into a liquid to be precipitated, and then performing two separation and purification processes on the liquid to be precipitated through multi-stage precipitation and centrifugation, thereby realizing the recovery of rare earth metal minerals from the dust and improving the economic benefits of enterprises.
[0015] 2. Multi-stage sedimentation filtration uses a separation method that combines buoyancy and water flow. It cleverly utilizes the density difference between dust particles and physical separation methods to achieve initial separation, which can greatly reduce the separation time of subsequent centrifugal separation.
[0016] 3. The multi-stage sedimentation filtration uses a high-density liquid to be settled, which can improve the buoyancy of the liquid on the dust. Combined with the water flow dynamics, it is easier to separate rare earth metal dust and particles falling off the grinding and polishing disc. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the recycling system structure of the present invention.
[0018] Among them: 1-mixing tank, 2-flotation tank, 3-premixed liquid outlet, 4-air plate, 5-premixing box, 6-inlet of liquid to be settled, 7-sedimentation tank, 8-base, 9-drainage baffle, 10-return pipe, 11-centrifuge, 12-drying device. Detailed Implementation
[0019] The present invention will be further described below with reference to embodiments, but this does not constitute any limitation on the present invention. Any limited modifications made by any person within the scope of the claims of the present invention are still within the scope of the claims of the present invention. Example 1 The present invention discloses a method for filtering and recovering rare earth metal polishing dust, the method comprising the following steps: Step 1: Add the recovered rare earth metal polishing dust to a measured amount of water and stir to obtain a premixed solution. The mixing ratio of rare earth metal polishing dust to water can be 1:10 by weight. Pure water can be used.
[0020] Step 2: Remove impurities from the premixed liquid to remove lighter floating or suspended matter from the dust, such as small-density particles that fall from the grinding disc during the grinding process and have a density close to that of water, or foreign matter that falls into the dust during the recycling process.
[0021] Step 3: Dilute the premixed solution after impurity removal to obtain the liquid to be precipitated. Specifically, in this step, water and sodium chloride are mixed in a predetermined ratio to obtain a high-density diluted solution. This high-density diluted solution is then mixed with the premixed solution in the same predetermined ratio to obtain the liquid to be precipitated. In this prepared liquid to be precipitated, excluding the influence of impurities such as dust, the density of the pure liquid is greater than that of water. This method increases the buoyancy of the liquid over dust particles, making it easier to precipitate and separate rare earth metal dust and particles from the polishing pad in subsequent processes.
[0022] Considering that sodium chloride is a volatile and flammable liquid, for safety reasons, the ratio of water to sodium chloride in the high-density dilution solution is 1:0.2 to 1:0.3. The specific ratio can be determined based on the mesh size of the polishing pad. For example, a 1000-mesh polishing pad produces a larger amount of particulate dust, so a higher concentration ratio (1:0.3) can be used to increase the buoyancy of the particles. Conversely, for polishing pads with a mesh size greater than 1500, which produce smaller particulate dust, a lower concentration ratio can be used to reduce sodium chloride consumption.
[0023] In this embodiment, the ratio of the premixed solution to the high-density diluent is 1:7 to 1:10. This ratio can be adjusted according to the actual sedimentation effect. Normally, a ratio of 1:7 is sufficient to reduce the consumption of high-density diluent. However, if the precipitate after sedimentation contains more than 40% particulate matter generated by the polishing pad, the ratio of the two liquids can be adjusted to 1:10.
[0024] Because rare earth metal polishing dust has a high overall density and is prone to settling, when mixing the high-density diluent and the premixed solution, equivalent amounts of both liquids can be added simultaneously according to their mixing ratio. The mixture is then stirred using a counter-flushing method, and the resulting liquid is discharged directly into the settling tank without remaining in the premixing tank. This avoids stratification of the diluted liquid.
[0025] Step 4: Perform multi-stage precipitation filtration on the liquid to be precipitated, and collect the precipitate mixture excluding the last stage precipitate as the target precipitate mixture. Return the precipitate mixture from the last stage precipitate to Step 2 for mixing and impurity removal with the premixed liquid. Recirculating the precipitate mixture from the last stage precipitate reduces the loss of rare earth metal dust.
[0026] Because the density of rare earth metal dust is 6 g / cm³ 3 The above information indicates that the particle density of the polishing pad is 3g / cm³. 3 Therefore, this embodiment utilizes the density difference between two different dust particles, combined with buoyancy settling and multi-stage sedimentation filtration, to achieve the initial separation of the two dust particles.
[0027] The multi-stage sedimentation filtration process involves transporting the liquid to be settled to a sedimentation tank equipped with three (or more) sedimentation tanks. Each sedimentation tank contains an inverted V-shaped support. The input direction of the liquid to be settled in each sedimentation tank is towards the upper-middle part (e.g., 2 / 3 position) of the corresponding support, so that the liquid flows towards and impacts the support. Because the surface of the support is inclined, the resulting water flow is mainly divided into a main flow towards the top of the support and a sedimentation flow towards the bottom. Furthermore, due to the high density of rare earth metal dust and the relatively small size difference between different types of dust particles, the rare earth metal dust mainly settles towards the bottom of the support, while the smaller particulate dust particles, influenced by buoyancy and water flow dynamics, mainly move upwards along the support. Ultimately, the sedimentation flow direction results in a sediment mixture, achieving preliminary separation.
[0028] However, it is important to note that the flow rate of the water entering the sedimentation tank needs to be adjusted according to the percentage of particulate matter and dust in the sediment of the first-stage sedimentation tank. For example, using a 25mm inner diameter conveying pipe with a 10cm distance between the pipe opening and the base, and a flow rate of 0.2m / s for the liquid to be settled, the percentage of particulate matter and dust can normally be controlled below 40%. However, if this percentage is exceeded, it indicates that the particle diameter may be large, and the flow rate needs to be appropriately increased, such as adjusting it to 0.25m / s.
[0029] To further enhance the buoyancy of the liquid on the dust, this embodiment includes a cooling system in the sedimentation tank to maintain the water temperature within a set range. The cooled liquid exerts a greater buoyancy on the dust than the liquid at room temperature, making it easier to separate dust particles of different densities and effectively improving the separation efficiency.
[0030] In this embodiment, the temperature range is 4-10℃. 4℃ is typically used.
[0031] In addition, during the dilution process in step three, the liquid to be precipitated can be pre-cooled before being fed into the sedimentation tank. Specifically, a sample cooler can be used to pre-cool the liquid to be precipitated; it is only necessary to ensure that the liquid to be precipitated is cooled to 10-15°C.
[0032] Step 5: Once the target precipitate mixture reaches a certain volume, centrifugation can be performed to obtain the target precipitate. Centrifugation allows for a secondary separation of the initially purified rare earth metal powder from the particulate powder, achieving better separation results. Measurements show that the content of the secondary purified rare earth metal powder can reach over 80%. Although the separation effect is not yet complete, the economic benefits brought by the rare earth metal powder are considerable for the enterprise, achieving the expected goals. After removing the target precipitate, since it still contains a small amount of sodium chloride, it is washed with pure water to dissolve the sodium chloride. Washing followed by precipitation removes most of the sodium chloride from the target precipitate.
[0033] Step 6: Dry the target precipitate to obtain a solidified rare earth metal powder. This solidified powder can be re-powdered and recycled for electrolytic refining.
[0034] Example 2 See Figure 1 A recycling system for implementing the above-described rare earth metal polishing dust filtration and recycling method includes: Mixing tank 1 is used to mix the recovered rare earth metal polishing dust after water has been added. After mixing, the liquid needs to be transferred to flotation tank 2 while mixing is in progress.
[0035] The dissolved air flotation (DAF) tank 2 is used to remove impurities from the premixed liquid. Unlike traditional DAF methods, the DAF tank 2 in this embodiment is equipped with an air plate 4, which has multiple micropores. A premixed liquid inlet is located above the air plate 4, and a premixed liquid outlet 3 is located below it. Before inputting the liquid, the DAF tank 2 must be filled with water. When the liquid is input into the DAF tank 2, because the liquid is above the air outlet, the rising gas carries lighter impurities from the dust to the top of the tank, while rare earth metals and particles from the polishing pads sink to the bottom of the DAF tank 2, and are then input into the premixing tank 5 along with the liquid. The amount of liquid input into the DAF tank 2 is consistent with the amount of liquid output, ensuring a balance between supply and demand and preventing overflow.
[0036] The premixing tank 5 is equipped with a cooler 1 to precool the liquid to be precipitated. The cooler 1 is connected to an external refrigeration unit.
[0037] Sedimentation tank 7 is used for multi-stage sedimentation and filtration of the liquid to be settled. It contains multiple sedimentation tanks, each with a fixed inverted V-shaped base 8. The top of the base 8 is arc-shaped. A flow guide baffle 9 is installed between adjacent bases 8, extending from the top of sedimentation tank 7 to the bottom, reaching a position horizontally corresponding to the upper middle part of the base 8. The first sedimentation tank has a liquid inlet 6, which faces the upper middle part of the base 8 in the first sedimentation tank. The last sedimentation tank is connected to the flotation tank 2 via a return pipe 10. Both the last and last sedimentation tanks are connected to the input port of the centrifuge 11. This structural design aims to ensure that the water flow formed by the liquid to be settled on the base is mainly divided into a main flow towards the top of the base and a sedimentation flow towards the bottom, thereby achieving the separation of rare earth metal polishing dust. Furthermore, a cooler is installed on the flow guide baffle 9 in sedimentation tank 7 to maintain the water temperature in the sedimentation tank at a set temperature.
[0038] Centrifuge 11 is used to centrifuge the target precipitate mixture to achieve secondary separation of rare earth metal polishing dust, thereby extracting the target precipitate. After the target precipitate is removed, since it still contains a small amount of sodium chloride, it is washed with pure water to dissolve the sodium chloride. After washing, precipitation is carried out to remove most of the sodium chloride from the target precipitate. Finally, the moistened target precipitate is placed in drying device 12.
[0039] Drying device 12 is used to dry the target precipitate to obtain agglomerated target material. The agglomerated target material is then pulverized to form rare earth metal powder that can be directly recycled. This rare earth metal powder can be directly added to an electrolytic cell for processing. Because the impurities in these rare earth metal powders are significantly reduced, the pollution caused to the materials in the electrolytic cell by adding them directly to the cell is greatly reduced, meeting the requirements for recycling.
[0040] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention, and these will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.
Claims
1. A method for filtering and recovering rare earth metal polishing dust, characterized in that, The method includes the following steps: Step 1: Add the recovered rare earth metal polishing dust to a certain amount of water and stir to obtain a premixed solution; Step 2: Remove impurities from the premixed liquid; Step 3: Dilute the premixed solution after impurity removal to obtain the liquid to be precipitated; Step 4: Perform multi-stage precipitation filtration on the liquid to be precipitated, and collect the precipitate mixture except for the last stage precipitate as the target precipitate mixture. Return the precipitate mixture of the last stage precipitate to Step 2 for mixing and impurity removal with the premixed liquid. Step 5: Centrifuge the target precipitate mixture to obtain the target precipitate; Step 6: Dry the target precipitate to obtain a solidified rare earth metal powder.
2. The method for filtering and recovering rare earth metal polishing dust according to claim 1, characterized in that, In step four, the multi-stage precipitation filtration process specifically includes: The liquid to be settled is transported to a sedimentation tank equipped with multiple sedimentation tanks. Each sedimentation tank is equipped with an inverted V-shaped seat. The input direction of the liquid to be settled in each sedimentation tank is towards the upper middle part of the corresponding seat, so that the liquid to be settled flows towards and impacts the seat, forming a water flow direction that is a mainstream direction towards the top of the seat and a sedimentation flow direction towards the bottom of the seat. The sedimentation flow direction results in a sedimentation mixture.
3. The method for filtering and recovering rare earth metal polishing dust according to claim 2, characterized in that, A cooling system is provided in the sedimentation tank to maintain the water temperature in the sedimentation tank within a set temperature range.
4. The method for filtering and recovering rare earth metal polishing dust according to claim 3, characterized in that, The temperature range is 4-10℃.
5. The method for filtering and recovering rare earth metal polishing dust according to claim 1, characterized in that, In step three, the specific method for diluting the premixed solution after impurity removal is as follows: Water and sodium chloride are mixed in a set ratio to obtain a high-density diluent. The high-density diluent is then mixed with a premixed solution in a set ratio to obtain the liquid to be precipitated.
6. The method for filtering and recovering rare earth metal polishing dust according to claim 5, characterized in that, The ratio of water to sodium chloride is 1:0.2 to 1:0.
3.
7. The method for filtering and recovering rare earth metal polishing dust according to claim 5, characterized in that, The ratio of the premixed solution to the high-density diluent is 1:7 to 1:
10.
8. The method for filtering and recovering rare earth metal polishing dust according to claim 5, characterized in that, The liquid to be precipitated is pre-cooled before being fed into the sedimentation tank.
9. A recycling system for implementing the rare earth metal polishing dust filtration and recycling method as described in any one of claims 1-8, characterized in that, include: A mixing tank (1) is used to mix the recovered rare earth metal polishing dust after water has been added to form a premixed liquid. An air flotation tank (2) is used to remove impurities from the premixed liquid. It is equipped with an air plate (4), which has multiple microholes. The air plate (4) has a premixed liquid inlet () above it and a premixed liquid outlet (3) below it. A sedimentation tank (7) is used for multi-stage sedimentation and filtration of the liquid to be settled. It is provided with multiple sedimentation tanks. Each sedimentation tank is fixed with an inverted V-shaped seat (8). The top of the seat (8) is an arc structure. A flow guide (9) is provided between two adjacent seats (8). The flow guide (9) extends from the top of the sedimentation tank (7) to the bottom and extends to a position corresponding to the upper part of the seat (8). The first sedimentation tank is provided with a liquid inlet (6) to be settled, and the liquid inlet (6) to be settled faces the upper part of the seat (8) in the first sedimentation tank. The last sedimentation tank is connected to the flotation tank (2) through a return pipe (10). Both the last sedimentation tank and the sedimentation tank are connected to the input port of the centrifuge (11). Centrifuge (11) is used to centrifuge the target precipitate mixture. A drying device (12) is used to dry the target precipitate.
10. A recycling system according to claim 9, characterized in that, A premixing tank (5) is provided between the flotation tank (2) and the sedimentation tank (7), and a cooler is installed in the premixing tank (5); a cooler is installed on the flow guide baffle (9) in the sedimentation tank (7).