High-purity aluminum powder pollution-free recycling and cyclic utilization process

Abstract

The application discloses a high-purity aluminum powder pollution-free recycling and cyclic utilization process and relates to the technical field of high-purity aluminum powder recycling and cyclic utilization, which comprises the following steps: high-purity aluminum ingots are melted and refined to obtain clean aluminum water; the clean aluminum water is filtered and then atomized by a nitrogen atomizer to obtain high-purity aluminum powder, which is then subjected to grading treatment; the high-purity aluminum powder after the grading treatment is divided into usable aluminum powder and unusable aluminum powder; the unusable aluminum powder is subjected to adsorption of iron impurities by a magnetic separation roller device; after remelting, a refining agent is added to remove impurities, and regenerated aluminum water is obtained and returned to a powder production procedure. The magnetic separation roller is arranged in a triangle shape by three electromagnetic rollers with spiral teeth on the surfaces, and an associated protection mechanism is arranged to ensure continuous powder output and no residue in cleaning. Through the synergistic effect of nitrogen protection, precise filtration, multi-stage magnetic separation and a refining agent, the purity of the recycled aluminum powder is kept above 99.99%, the unusable powder is recycled in a pollution-free closed loop, the cost is significantly reduced, and the application is suitable for industrial application.

Description

Technical Field

[0001] This invention relates to the field of high-purity aluminum powder recycling technology, and in particular to a pollution-free recycling process for high-purity aluminum powder. Background Technology

[0002] High-purity aluminum powder (aluminum purity ≥ 99.99%) is an important functional powder material, mainly used in high-end electronic components such as composite three-dimensional electrode foils for aluminum electrolytic capacitors. Its particle size requirement is typically within a narrow range of 3-6 μm. However, in the nitrogen atomization powder production process, the resulting high-purity aluminum powder has a particle size distribution between 1-50 μm. Less than 25% of this powder meets the particle size requirements and can be used, while the remaining over 75% is unusable and faces the challenge of recycling and reuse.

[0003] Because aluminum powder has a large specific surface area and high chemical activity, it is very easy to introduce impurities such as iron, silicon, oxygen, and hydrogen during the recycling process, causing the purity to drop to below 99.99%. In the end, it can only be sold as low-value alloy aluminum powder, resulting in huge resource waste and production cost pressure.

[0004] Currently, there are no publicly available patents or industry information specifically reporting on the pollution-free recycling and reuse of high-purity aluminum powder. How to achieve efficient recycling of unusable high-purity aluminum powder, effectively control contamination from elements such as iron, silicon, oxygen, and hydrogen throughout the entire recycling process, and ensure that the recycled aluminum powder retains a purity of over 99.99% and can be returned to the main production line for reuse, has become a key technical challenge restricting the large-scale production of high-purity aluminum powder.

[0005] Therefore, a pollution-free process for recycling and reusing high-purity aluminum powder is provided. Summary of the Invention

[0006] The purpose of this invention is to provide a pollution-free recycling process for high-purity aluminum powder, which solves the problems mentioned in the background technology.

[0007] This invention is achieved through a pollution-free recycling process for high-purity aluminum powder, comprising the following steps: S1. High-purity aluminum ingots are put into a smelting and holding furnace for melting and refining to obtain clean molten aluminum; S2. The clean aluminum molten metal is filtered by a filter device between the outlet of the heat preservation furnace cavity and the nitrogen atomizer, and then atomized by the nitrogen atomizer to obtain high-purity aluminum powder of 1-50μm. S3. The high-purity aluminum powder is classified by particle size under nitrogen protection to obtain usable aluminum powder and unusable powder; each aluminum powder outlet in the classification process is equipped with a magnetic separation roller device. S4. The unusable powder obtained in step S3 is compressed into blocks under nitrogen protection to obtain aluminum powder blocks. S5. The aluminum powder block is put into the smelting furnace for remelting. A refining agent is added to make the impurity elements slag and float to the surface. The slag is then removed to obtain clean molten aluminum. S6. Return the clean aluminum molten metal obtained in step S5 to step S1 to continue powder production.

[0008] A further technical solution of the present invention is: in step S2, the filtration accuracy of the filtration device is 0.010-0.050mm, which is used to block coarse particulate impurities in the molten aluminum from entering the atomization stage.

[0009] A further technical solution of the present invention is: in step S3, the magnetic separation roller device includes three electromagnetic magnetic separation rollers with a spiral tooth structure on the surface. The electromagnetic magnetic separation rollers are arranged in an equilateral triangle, with one roller in the middle of the upper layer and two rollers symmetrically arranged in the lower layer, so as to increase the contact area between aluminum powder and the magnetic separation rollers and improve the adsorption efficiency of iron particles.

[0010] A further technical solution of the present invention is that the magnetic separation roller device is also provided with an associated protection device, which is configured such that the electromagnetic magnetic separation roller is allowed to be demagnetized only when nitrogen purging is turned on.

[0011] A further technical solution of the present invention is that the diameter of the electromagnetic separator roller is 0.15 to 0.25 times the outlet diameter.

[0012] A further technical solution of the present invention is: in step S4, a magnetic separation roller device with the same operation process and steps as in step S3 is provided at the material outlet, and the working process of the magnetic separation roller device includes: S01. When discharging, first start the magnetic separator roller to rotate and energize it, then open the discharge valve to allow the material to flow through the rotating magnetic separator roller. S02. When cleaning impurities, switch to the impurity collection position, turn on nitrogen purging, and demagnetize the magnetic separator roller after the nitrogen purging is turned on, so that the adsorbed impurities are purged and collected.

[0013] A further technical solution of the present invention is that the refining agent can simultaneously remove multiple impurity elements such as calcium, sodium, magnesium, silicon, oxygen and hydrogen from molten aluminum, so that the quality of the circulating molten aluminum continuously meets the preparation requirements of high-purity aluminum powder (Al≥99.99%).

[0014] A further technical solution of the present invention is: if the usable aluminum powder obtained in step S3 does not meet the target particle size requirements, it can be repeatedly graded once or multiple times. During the grading process, the nitrogen protection and magnetic separation roller device operation of step S3 are repeated.

[0015] A further technical solution of the present invention is that the entire process of powdering, grading, collection, briquetting, and remelting is carried out in a nitrogen protective atmosphere with a purity of ≥99% to prevent oxidation and contamination.

[0016] A further technical solution of the present invention is: through the combined application of magnetic separation, precision filtration, nitrogen protection throughout the process and special refining agent, the purity of the recovered aluminum powder is still maintained at ≥99.99%, realizing the pollution-free closed-loop recycling of unusable powder.

[0017] The beneficial effects of this invention are: 1. This invention places the entire process of powdering, grading, collection, briquetting, and remelting under nitrogen protection with a purity of ≥99%, and sets up a precision filter of 0.010 to 0.050 mm before the aluminum liquid enters the atomizer, thus blocking the introduction of oxide inclusions at the source. At the same time, it strictly controls the oxygen content of aluminum powder to ≤0.4%, laying the foundation for high-quality recycling in the future.

[0018] 2. This invention innovatively incorporates a dual magnetic separation purification device at the grading outlet and the briquetting discharge port. This device employs three electromagnetic magnetic separation rollers arranged in an equilateral triangle with a spiral toothed surface, which rotate continuously, greatly increasing the contact area with the aluminum powder and achieving efficient adsorption of iron particles. Its core interconnected protection design ensures that demagnetization can only occur during nitrogen purging, completely eliminating secondary pollution caused by accidental demagnetization during operation. Combined with the specialized refining agent used in the remelting process, it can simultaneously remove multiple impurity elements such as calcium, sodium, magnesium, silicon, oxygen, and hydrogen, ensuring that the purity of the recycled aluminum remains consistently above 99.99%, fully meeting the requirements for reproducing high-purity aluminum powder.

[0019] 3. This process achieves 100% pollution-free closed-loop recycling of unusable powder, significantly improving raw material utilization, greatly reducing the production cost of high-purity aluminum powder, and reducing resource waste. It has important economic value and environmental significance for promoting the large-scale application of high-purity aluminum powder in high-end fields such as composite three-dimensional electrode foil for aluminum electrolytic capacitors. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the workflow of the present invention. Detailed Implementation

[0021] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0022] It should be noted that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding and reading. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0023] This invention provides a pollution-free recycling process for high-purity aluminum powder. Its core lies in the use of high-purity nitrogen protection throughout the entire process, precision filtration before atomization, dual magnetic separation purification in the grading and briquetting stages, and special refining agent treatment in the remelting stage. This effectively solves the problem of unusable high-purity aluminum powder being easily contaminated by elements such as iron, silicon, oxygen, and hydrogen during the recycling process, thereby achieving 100% closed-loop pollution-free recycling of unusable powder and ensuring that the recycled products can still meet the preparation requirements of high-purity aluminum powder (Al≥99.99%).

[0024] Example 1 This embodiment describes in detail a complete cycle of the pollution-free recycling process of high-purity aluminum powder according to the present invention.

[0025] Step S1: Raw material smelting and refining First, high-purity aluminum ingots with a purity of 99.99% are selected as the starting material. The aluminum ingots are then melted in an integrated melting and holding furnace. After melting, high-purity nitrogen gas (purity ≥99.99%) is introduced into the molten aluminum at a temperature of 740-760℃ for refining treatment to remove some gases and inclusions, obtaining uniform and clean molten aluminum, providing high-quality raw materials for subsequent atomization powder production.

[0026] Step S2: Precision filtration and atomization powder production The clean molten aluminum obtained in step S1 is placed in the holding furnace cavity. The outlet of the holding furnace cavity is connected to a nitrogen atomizer, and a high-precision filter is installed in the channel between the two. The filtration accuracy of this filter is 0.010 to 0.050 mm, and in this embodiment it is set to 0.030 mm. Its function is to effectively block any microscopic oxide inclusions or other refractory material particles that may be present in the molten aluminum and are invisible to the naked eye, preventing them from entering the atomization process and contaminating the final aluminum powder.

[0027] The filtered, clean molten aluminum enters a nitrogen atomizer. The atomizer uses high-pressure, high-purity nitrogen (≥99.99% purity) as the atomizing medium to pulverize and cool the molten aluminum, forming fine aluminum powder particles. By adjusting the atomization parameters, the particle size distribution of the resulting aluminum powder is controlled within the range of 1-50 μm. The atomized aluminum powder is then carried by the airflow into a collection tank for initial sedimentation and collection. The entire atomization process is conducted in a closed system to ensure isolation from outside air.

[0028] Step S3: Particle size classification and magnetic separation under nitrogen protection The high-purity aluminum powder in the collection tank is conveyed via a pneumatic conveying system under the protection of high-purity nitrogen (≥99%), and then fed into a classification system consisting of centrifugal classifiers, cyclone classifiers, and bag filters for particle size classification. The goal of the classification is to separate usable aluminum powder that meets customer particle size requirements (e.g., 2-6μm) from unusable powder that is too coarse or too fine.

[0029] The core of this step lies in the fact that each aluminum powder outlet (including usable powder outlet and unusable powder outlet) of the grading system is equipped with a unique magnetic separation roller device, the specific structure of which is as follows: Two electrically operated valves are installed at the top and bottom of the powder outlet pipe, and three electromagnetic separator rollers are installed on the pipe between the two valves. The surface of the separator rollers has a spiral tooth structure to increase the contact area and friction with the aluminum powder, thereby improving the adsorption efficiency. The diameter of the rollers is designed to be between 0.15 and 0.25 times the diameter of the outlet pipe, and in this embodiment, it is preferably 0.2 times. The three rollers are installed in two layers, with the upper roller located in the middle of the pipe and the lower two rollers arranged symmetrically. Their positions and spacing are such that the center line connecting the three rollers forms an equilateral triangle. Each separator roller is a hollow structure, with nitrogen gas pipes running through it for cooling and purging, and is continuously rotated by a motor during operation.

[0030] The working process of the magnetic separator roller is automatically controlled by the associated protection device, as follows: Start-up phase: When grading is completed and powder is ready to be discharged, the control system first activates the electromagnets of the three magnetic separator rollers and drives them to start rotating continuously.

[0031] Delayed powder discharge: After the magnetic rotation stabilizes, there is a 3-second delay. This delay allows a stable magnetic field to be established on the surface of the magnetic separator rollers and achieve uniform rotation. After the delay, the control system first opens the lower powder discharge valve, then the upper powder discharge valve. Aluminum powder from the grading tank falls through the pipe and must pass through the "triangular" area formed by the three magnetic separator rollers. As the aluminum powder flows over the spiral tooth surface, the tiny iron particles impurities it carries are fully attracted to the roller surface by the strong magnetic force, while the pure aluminum powder passes smoothly and falls into the collection bucket below.

[0032] Stop and Cleaning Phase: After powder discharge is complete, first close the upper powder discharge valve. Remove the aluminum powder collection bucket and then place it into the impurity collection bucket. At this time, keep the magnetic separator roller rotating. Next, the control system demagnetizes the magnetic separator roller and simultaneously opens the internal nitrogen purging valve to perform a powerful purging of the roller surface for about 2 minutes. After losing magnetic attraction, the ferrous particles that have been purged will fall into the impurity collection bucket. After purging is complete, stop the rotation of the magnetic separator roller, stop purging, and finally close the lower powder discharge valve.

[0033] The core of this interconnected protection device lies in interlocking the purging and demagnetizing actions of the magnetic separator roller: the magnetic separator roller is only allowed to be demagnetized when nitrogen purging is activated; otherwise, demagnetization cannot be manually shut off. This design ensures that the magnetic separator roller will never be accidentally demagnetized during operation (powder discharge), preventing adsorbed iron impurities from falling off and re-contaminating the aluminum powder. Simultaneously, it ensures that cleaning must be carried out under nitrogen protection to prevent impurities from oxidizing or becoming airborne without protection, achieving residue-free cleaning.

[0034] Through the above process, the usable aluminum powder obtained by grading is guaranteed in purity while its oxygen content is strictly controlled within the range of ≤0.4%.

[0035] Re-grading of usable aluminum powder (optional): If the customer has stricter technical requirements for the particle size of the graded aluminum powder (e.g., a narrower particle size distribution of 3-5μm), it can be fed back into the grading equipment for a second or even third fine grading. Each repeated grading process strictly follows the nitrogen protection and magnetic separation roller device operation procedures in step S3 to ensure that the purity of the product is not contaminated while obtaining accurate particle size distribution.

[0036] Step S4: Compacting unusable powder into briquettes and secondary magnetic separation The unusable powder (i.e., aluminum powder whose particle size does not meet the requirements) identified in step S3 is loaded into a sealed storage tank at the top of the briquetting machine by manual labor or a closed conveyor. After the storage tank is full of powder, the loading port is closed, and the inside is kept under high-purity nitrogen protection.

[0037] The discharge port of the storage tank is also equipped with a magnetic separation roller device identical to that in step S3: Two electric valves are installed at the discharge port, and three electromagnetic magnetic separation rollers, arranged in an equilateral triangle, with spiral teeth on the surface, filled with nitrogen, and with a diameter 0.2 times the outlet diameter, are installed on the pipe between the two valves. The operation process is as follows: 1. Align the discharge pipe of the storage tank with the briquetting chamber of the briquetting machine.

[0038] 2. Start the magnetic separator roller to energize and rotate.

[0039] 3. After a 3-second delay, first open the lower powder outlet valve, then open the upper powder outlet valve. The unusable powder in the storage tank, under nitrogen protection, undergoes secondary magnetic separation by the magnetic separator roller to remove any iron that may have been mixed in, and then quantitatively enters the briquetting chamber.

[0040] 4. Inside the briquetting chamber, a hydraulic press is used to compress the loose aluminum powder into aluminum powder blocks with a certain density and strength.

[0041] 5. After the quantitative powder dispensing is completed, close the upper powder dispensing valve. After the briquettes are pressed, reopen the upper powder dispensing valve and repeat this quantitative powder dispensing and briquetting operation until all the aluminum powder in the storage tank is pressed out.

[0042] 6. Regular Cleaning: Based on the dual requirements of production throughput and time set by the production process, the discharge pipe is adjusted periodically (e.g., every 4 hours of operation or after processing a certain amount of tonnage) to align the pipe opening with the impurity collection bin. Then, while keeping the magnetic separator roller rotating, it is demagnetized, and simultaneously, nitrogen purging is activated to purge and collect the adsorbed impurities into the bin, continuing for approximately 2 minutes. Afterward, the rotation of the magnetic separator roller is stopped, purging is stopped, the lower powder discharge valve is closed, and the discharge pipe is realigned with the briquetting chamber to resume normal operation. Magnetic separation here serves as a secondary safeguard, and the regular cleaning mechanism ensures the continuous high efficiency of the magnetic separator roller, further purifying the materials entering the smelting stage.

[0043] Step S5: Remelting and refining of aluminum powder blocks The aluminum powder blocks pressed in step S5 are transported to a smelting furnace via a collection box for remelting and recycling. The aluminum powder blocks are then fed into the smelting furnace and melted into molten aluminum under high temperature conditions. A special composite refining agent is then added to the molten aluminum.

[0044] It is important to note that the aforementioned refining agent is not a single substance, but a composite solvent composed of various inorganic salts. In this embodiment, the refining agent is selected from one or more combinations of chloride and fluoride salts. Preferably, the refining agent contains potassium chloride, magnesium chloride, potassium fluoroaluminate, and sodium nitrate, which can simultaneously remove multiple impurity elements such as calcium, sodium, magnesium, silicon, oxygen, and hydrogen from the molten aluminum. Therefore, this refining agent can effectively adsorb and react with metallic impurities such as calcium, sodium, magnesium, and silicon, as well as gases such as oxygen and hydrogen and non-metallic inclusions in the molten aluminum, generating a light scum that floats to the surface of the molten aluminum. The scum is thoroughly removed using a skimming tool, thereby obtaining clean molten aluminum (Al≥99.99%) with a purity equivalent to the initial raw material, ensuring that its quality continuously meets the process requirements for the preparation of high-purity aluminum powder during repeated cycles.

[0045] Step S6: Return to loop The clean molten aluminum obtained after slag removal in step S6 is returned to the smelting and holding furnace in step S1. After being mixed with new high-purity aluminum ingots, it is refined, filtered, and atomized into powder again, thus starting a new cycle.

[0046] Through the close integration of the above seven steps, this invention achieves 100% pollution-free closed-loop recycling of unusable aluminum powder generated during the powder-making process. The entire process—powdering, grading, collection, briquetting, and remelting—is conducted in a nitrogen protective atmosphere with a purity of ≥99%. Combined with precision filtration in S2, dual magnetic separation in S3 and S5, and treatment with a dedicated refining agent in S6, this ensures that the purity of the recycled aluminum powder remains consistently at ≥99.99%. This successfully solves the technical problems of difficult and costly high-purity aluminum powder recycling, achieving the circular utilization of high-value materials.

[0047] Example 2 In this embodiment, the specific steps of a pollution-free recycling process for high-purity aluminum powder are as follows: S1. High-purity aluminum ingots are put into a smelting and holding furnace for melting and refining to obtain clean molten aluminum; S2. The clean aluminum molten metal is filtered by a filter device between the outlet of the heat preservation furnace cavity and the nitrogen atomizer, and then atomized by the nitrogen atomizer to obtain high-purity aluminum powder. S3. The high-purity aluminum powder is classified by particle size under nitrogen protection to obtain usable aluminum powder and unusable powder; each aluminum powder outlet in the classification process is equipped with a magnetic separation roller device. S4. The unusable powder obtained in step S3 is compressed into blocks under nitrogen protection to obtain aluminum powder blocks. S5. The aluminum powder block is put into the smelting furnace for remelting. A refining agent is added to make the impurity elements slag and float to the surface. The slag is then removed to obtain clean molten aluminum. S6. Return the clean aluminum molten metal obtained in step S5 to step S1 to continue powder production.

[0048] Example 2 is basically the same as Example 1, except that the entire process of powdering, grading, collection, briquetting and remelting is carried out in a low-purity nitrogen protective atmosphere (nitrogen purity is about 95.5%), and other process parameters are consistent with those of Example 1.

[0049] Example 3 In this embodiment, the specific steps of a pollution-free recycling process for high-purity aluminum powder are as follows: S1. High-purity aluminum ingots are put into a smelting and holding furnace for melting and refining to obtain clean molten aluminum; S2. The clean aluminum molten metal is directly atomized by a nitrogen atomizer to obtain high-purity aluminum powder; S3. The high-purity aluminum powder is classified by particle size under nitrogen protection to obtain usable aluminum powder and unusable powder; each aluminum powder outlet in the classification process is equipped with a magnetic separation roller device. S4. The unusable powder obtained in step S3 is compressed into blocks under nitrogen protection to obtain aluminum powder blocks. S5. The aluminum powder block is put into the smelting furnace for remelting. A refining agent is added to make the impurity elements slag and float to the surface. The slag is then removed to obtain clean molten aluminum. S6. Return the clean aluminum molten metal obtained in step S5 to step S1 to continue powder production.

[0050] Example 3 is basically the same as Example 1, except that in step S2, the filter device between the outlet of the heat preservation furnace cavity and the nitrogen atomizer is removed, and the molten aluminum enters the atomizer directly without filtration. Other process parameters are consistent with those in Example 1.

[0051] Example 4 In this embodiment, the specific steps of a pollution-free recycling process for high-purity aluminum powder are as follows: S1. High-purity aluminum ingots are put into a smelting and holding furnace for melting and refining to obtain clean molten aluminum; S2. The clean aluminum molten metal is filtered by a filter device between the outlet of the heat preservation furnace cavity and the nitrogen atomizer, and then atomized by the nitrogen atomizer to obtain high-purity aluminum powder. S3. The high-purity aluminum powder is subjected to particle size classification under nitrogen protection to obtain usable aluminum powder and unusable powder. S4. The unusable powder obtained in step S3 is compressed into blocks under nitrogen protection to obtain aluminum powder blocks. S5. The aluminum powder block is put into the smelting furnace for remelting. A refining agent is added to make the impurity elements slag and float to the surface. The slag is then removed to obtain clean molten aluminum. S6. Return the clean aluminum molten metal obtained in step S5 to step S1 to continue powder production.

[0052] The difference between Example 4 and Example 1 is that the magnetic separation roller device set at the grading outlet in step S3 and the feeding port in step S4 is cancelled, and the aluminum powder falls directly to the processing unit.

[0053] Example 5 In this embodiment, the specific steps of a pollution-free recycling process for high-purity aluminum powder are as follows: S1. High-purity aluminum ingots are put into a smelting and holding furnace for melting and refining to obtain clean molten aluminum; S2. The clean aluminum molten metal is filtered by a filter device between the outlet of the heat preservation furnace cavity and the nitrogen atomizer, and then atomized by the nitrogen atomizer to obtain high-purity aluminum powder. S3. The high-purity aluminum powder is classified by particle size under nitrogen protection to obtain usable aluminum powder and unusable powder; each aluminum powder outlet in the classification process is equipped with a magnetic separation roller device. S4. The unusable powder obtained in step S3 is compressed into blocks under nitrogen protection to obtain aluminum powder blocks. S5. The aluminum powder blocks are put into a smelting furnace for remelting to obtain clean molten aluminum; S6. Return the clean aluminum molten metal obtained in step S5 to step S1 to continue powder production.

[0054] The difference between Example 5 and Example 1 is that the refining agent in step S5 is omitted, and aluminum powder blocks made from powder cannot be directly remelted.

[0055] Example 6 In this embodiment, the specific steps of a pollution-free recycling process for high-purity aluminum powder are as follows: S1. High-purity aluminum ingots are put into a smelting and holding furnace for melting and refining to obtain clean molten aluminum; S2. The clean aluminum molten metal is directly atomized by a nitrogen atomizer to obtain high-purity aluminum powder; S3. The high-purity aluminum powder is classified by particle size under nitrogen protection to obtain usable aluminum powder and unusable powder; each aluminum powder outlet in the classification process is equipped with a magnetic separation roller device. S4. The unusable powder obtained in step S3 is compressed into blocks under nitrogen protection to obtain aluminum powder blocks. S5. The aluminum powder blocks are put into a smelting furnace for remelting to obtain clean molten aluminum; S6. Return the clean aluminum molten metal obtained in step S5 to step S1 to continue powder production.

[0056] Compared with Example 1, Example 6 differs in that: not only is the filter device between the outlet of the heat preservation furnace cavity and the nitrogen atomizer removed in step S2, allowing the molten aluminum to enter the atomizer directly without filtration; the refining agent in step S5 is also removed, and the molten aluminum obtained by remelting the aluminum powder blocks formed by pressing is directly fed into step S1 to continue powder production.

[0057] The content of each element and the recovery rate of the high-purity aluminum powder recovered in Examples 1 to 6 are detailed in the table below: Table 1: Details of elemental content in recycled aluminum powder Based on the comparison of the above embodiments, it can be seen that: Example 2 (No High-Purity Nitrogen Protection Throughout the Process): In this example, since no high-purity nitrogen protection is provided throughout the process, the aluminum powder comes into direct contact with air during the grading and briquetting processes. This leads to an increase in oxygen and hydrogen content, resulting in more inclusions and a decrease in the recovery rate. This example demonstrates that high-purity nitrogen protection is the fundamental guarantee for preventing oxidation contamination and maintaining purity.

[0058] Example 3 (Elimination of Precision Filtration Before Atomization): In this example, impurities gradually accumulate in the molten aluminum after circulation, leading to a significant increase in the oxygen and hydrogen content of the aluminum powder, a decrease in the recycling rate, and a significant decrease in aluminum purity, failing to meet purity requirements. This example demonstrates that precision filtration is a crucial step in preventing the continuous accumulation of impurities and maintaining stable circulation.

[0059] Example 4 (Purification without Magnetic Separation): In this example, the iron content in the recovered aluminum powder increased significantly, leading to a decrease in the purity of the aluminum powder. This example demonstrates that magnetic separation purification plays an irreplaceable role in controlling iron contamination.

[0060] Example 5 (without refining agent): In this example, the removal of impurities such as calcium, silicon, oxygen, and hydrogen was insufficient. After recycling, impurities accumulated, leading to a decrease in aluminum powder purity and an increase in oxygen and hydrogen content. This example demonstrates that the ability of a specialized composite refining agent to simultaneously remove multiple impurity elements is crucial for maintaining recycling quality.

[0061] Example 6 (Unrefined, Unfiltered): In this example, the impurity content in the powder continuously accumulates, the oxygen and hydrogen content increases significantly, the aluminum purity decreases considerably, and the high amount of coarse impurities causes the filter to clog rapidly, reducing production efficiency.

[0062] A system comparison between Example 1 and five other comparative examples demonstrates that this invention, through the organic synergy of four core elements—high-purity nitrogen protection throughout the process, precision filtration before atomization, dual magnetic separation purification, and treatment with a dedicated refining agent—forms a complete pollution control system, encompassing source blocking, process protection, and multi-level purification. The absence or simplification of any element leads to a decrease in the purity of the recovered aluminum powder, an increase in impurity content, or a deterioration in cycle stability, failing to consistently meet the requirements for preparing high-purity aluminum powder. Furthermore, the unfiltered and unrefined aluminum molten metal recovered and remelted in Example 6 is of substandard quality and cannot be used normally. Only Example 1, employing all core technical features simultaneously, achieves a stable aluminum powder purity of ≥99.99% and a resource utilization rate increased to 95%, demonstrating that this invention is the optimal technical solution for achieving pollution-free closed-loop recycling of high-purity aluminum powder.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A pollution-free recycling process for high-purity aluminum powder, characterized in that, Includes the following steps: S1. High-purity aluminum ingots are put into a smelting and holding furnace for melting and refining to obtain clean molten aluminum; S2. The clean aluminum molten metal is filtered by a filter device between the outlet of the heat preservation furnace cavity and the nitrogen atomizer, and then atomized by the nitrogen atomizer to obtain high-purity aluminum powder of 1-50μm. S3. The high-purity aluminum powder is classified by particle size under nitrogen protection to obtain usable aluminum powder and unusable powder; each aluminum powder outlet in the classification process is equipped with a magnetic separation roller device. S4. The unusable powder obtained in step S3 is compressed into blocks under nitrogen protection to obtain aluminum powder blocks. S5. The aluminum powder block is put into the smelting furnace for remelting. A refining agent is added to make the impurity elements slag and float to the surface. The slag is then removed to obtain clean molten aluminum. S6. Return the clean aluminum molten metal obtained in step S5 to step S1 to continue powder production.

2. The pollution-free recycling process for high-purity aluminum powder according to claim 1, characterized in that, In step S2, the filtration accuracy of the filtration device is 0.010-0.050 mm, which is used to block coarse particulate impurities in the molten aluminum from entering the atomization stage.

3. The pollution-free recycling process for high-purity aluminum powder according to claim 1, characterized in that, In step S3, the magnetic separation roller device includes three electromagnetic magnetic separation rollers with a spiral tooth structure on the surface. The electromagnetic magnetic separation rollers are arranged in a triangle, with one roller in the middle on the top layer and two rollers symmetrically arranged on the bottom layer, in order to increase the contact area between aluminum powder and the magnetic separation rollers and improve the adsorption efficiency of iron particles.

4. The pollution-free recycling process for high-purity aluminum powder according to claim 3, characterized in that, The magnetic separator is also equipped with an associated protection device, which is configured to allow demagnetization of the electromagnetic separator only when nitrogen purging is activated.

5. The pollution-free recycling process for high-purity aluminum powder according to claim 4, characterized in that, The diameter of the electromagnetic separator roller is 0.15 to 0.25 times the outlet diameter.

6. The pollution-free recycling process for high-purity aluminum powder according to claim 1, characterized in that, In step S4, a magnetic separation roller device with the same operating procedure and steps as in step S3 is installed at the material outlet. The working process of the magnetic separation roller device includes: S01. When discharging, first start the magnetic separator roller to rotate and energize it, then open the discharge valve to allow the material to flow through the rotating magnetic separator roller. S02. When cleaning impurities, switch to the impurity collection position, turn on nitrogen purging, and demagnetize the magnetic separator roller after the nitrogen purging is turned on, so that the adsorbed impurities are purged and collected.

7. The pollution-free recycling process for high-purity aluminum powder according to claim 1, characterized in that, The refining agent can simultaneously remove multiple impurity elements such as calcium, sodium, magnesium, silicon, oxygen, and hydrogen from molten aluminum, ensuring that the quality of the circulating molten aluminum continuously meets the requirements for the preparation of high-purity aluminum powder (Al≥99.99%).

8. The pollution-free recycling process for high-purity aluminum powder according to claim 1, characterized in that, If the particle size of the usable aluminum powder obtained in step S3 does not meet the target requirements, it can be repeated once or multiple times. During the classification process, the nitrogen protection and magnetic separation roller device operation of step S3 are repeated.

9. The pollution-free recycling process for high-purity aluminum powder according to any one of claims 1 to 8, characterized in that, The entire process of powder making, grading, collection, briquetting, and remelting is carried out in a nitrogen protective atmosphere with a purity of ≥99% to prevent oxidation and contamination.

10. The pollution-free recycling process for high-purity aluminum powder according to claim 1, characterized in that, Through the combined application of magnetic separation, precision filtration, nitrogen protection throughout the process, and special refining agents, the purity of the recovered aluminum powder remains at ≥99.99%, achieving pollution-free closed-loop recycling of unusable powder.

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