Method and system for preventing impurities and foreign matters from entering powder finished product

Abstract

The invention discloses a method and a system for preventing impurities and foreign matters from entering a powder finished product, an integrated process of vacuum closed conveying, multi-field cooperative separation, double-path online monitoring and closed-loop control is adopted, external pollution is completely eradicated from the source through vacuum closed conveying, and the impurities and foreign matters are effectively prevented from entering the powder finished product through three-stage cooperative treatment. Gradient removal of full-size and full-type impurities above 0.1 mu m is achieved, millisecond-level impurity detection is achieved through double-path online monitoring of an LIBS and a light scattering particle counter, and full-automatic closed-loop regulation and control of technological parameters are achieved in cooperation with a PLC system. The total impurity content of the powder finished product can be stably reduced to be smaller than or equal to 10 ppm, the impurity removal rate is larger than 99.9%, the secondary pollution risk is smaller than 0.1%, the treatment efficiency is larger than or equal to 100 kg / h, the operation cost is reduced by 50% or above, and the problems that in the prior art, submicron impurities are not thoroughly removed, secondary pollution is prone to occurring, detection lags, efficiency is low and cost is high are solved.

Description

Technical Field

[0001] This invention relates to the field of powder purification and preparation technology for powder metallurgy and additive manufacturing, and in particular to a method and system for preventing impurities and foreign matter from entering the finished powder product. It is applicable to the whole process of impurity control and high-precision purification of powder materials in high-end fields such as metal powder for 3D printing, ceramic powder for medical implants, and polymer powder for electronic packaging. Background Technology

[0002] With the rapid development of high-end manufacturing fields such as aerospace, medical implants, and electronic packaging, the purity requirements for powder finished products in processes such as additive manufacturing and powder metallurgy have increased from 99.9% to over 99.99%, meaning the total impurity content must be controlled below 100 ppm. Impurities and foreign matter in powder finished products, including metal oxides, non-metallic particles, organic fibers, and environmental dust, are core factors leading to the failure of end products: In the aerospace field, oxide impurities as small as 1 μm in 3D-printed aero-engine blades can reduce the fatigue life of components by more than 40%; in the field of medical implants, fibrous impurities in titanium alloy powder may trigger chronic inflammation and rejection reactions in the human body; in the field of electronic packaging, metal particles in ceramic powder can cause short circuits in packaging circuits, reducing product yield to below 60%.

[0003] Currently, the mature existing technologies for controlling powder impurities mainly fall into two mainstream categories: One approach is a multi-stage sieving-filtration system. This system uses three vibrating screens (200 mesh, 400 mesh, and 800 mesh) combined with a 0.5μm microporous filter membrane to remove powder impurities. An offline laser particle size analyzer is used to detect the impurity content, and products that pass the test are packaged. The core drawbacks of this system are: the microporous filter membrane can only intercept particles larger than 0.5μm, with a removal rate of less than 50% for submicron impurities (0.1-0.5μm), resulting in incomplete removal of tiny impurities; the metal mesh of the vibrating screen is prone to wear and tear from long-term operation, generating metal particles; frequent filter membrane replacements can introduce environmental dust, posing a serious risk of secondary pollution; the offline detection cycle is greater than 2 hours, making it impossible to provide real-time feedback on impurity content, potentially leading to the scrapping of entire batches; the sieving efficiency of the 800-mesh screen is less than 30kg / h, and filter membrane replacement costs account for more than 15% of the total production cost, resulting in a serious contradiction between efficiency and cost.

[0004] The second method is a combined air classifier-magnetic separator process. This method uses a 6000 rpm air classifier to separate light impurities such as dust and fibers, and a 1.5T high-gradient magnetic separator to remove magnetic metallic impurities. The core drawback of this method is that it can only remove magnetic metallic impurities and has no effect on removing non-metallic impurities such as SiO2 and Al2O3 in ceramic powder, resulting in a blind spot in impurity removal. Furthermore, the air classifier process is prone to causing agglomeration of ultrafine powder, which not only affects the purification effect but also causes the loss of qualified powder.

[0005] Furthermore, existing purification technologies such as single electrostatic adsorption and ultrasonic sieving cannot simultaneously cover the removal requirements of impurities of all sizes and types, nor can they form a closed-loop control system that links online monitoring with process parameters. This makes it difficult to stably achieve the high-end application requirements of powder finished products with impurity content ≤10ppm, and cannot meet the extreme requirements of powder purity in aerospace, medical implantation and other fields. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for preventing impurities and foreign matter from entering finished powder products, specifically addressing four core problems of existing technologies: first, incomplete removal of submicron-level impurities, making it impossible to consistently achieve impurity control accuracy below 10 ppm; second, the processing is prone to introducing secondary pollution, making it impossible to achieve full-process pollution control; third, offline detection is lagging, easily leading to the scrapping of batch products; and fourth, low processing efficiency and high operating costs, failing to meet the demands of high performance and industrial mass production. This invention can consistently achieve a total impurity content of ≤10 ppm in finished powder products, while possessing the advantages of high efficiency, low cost, closed-loop control throughout the entire process, and compatibility with various powder materials.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for preventing impurities and foreign matter from entering a finished powder product includes the following steps: S1, Vacuum-sealed conveying: The raw material powder is placed in a sealed conveying environment with a vacuum degree of -0.06~-0.1MPa and conveyed through a stainless steel pipe with an inner wall polished Ra<0.2μm. The conveying speed is controlled at 8~12m / s and the pressure fluctuation inside the pipe is <±0.002MPa. The vacuum environment isolates external impurities such as dust and fibers, and the polishing of the inner wall of the pipe reduces secondary pollution caused by powder residue and pipe wall wear. S2, Multi-stage Synergistic Separation: The conveyed powder undergoes a three-stage synergistic separation process: airflow inertial separation, electrostatic adsorption separation, and ultrasonic sieving separation, achieving the removal of impurities of all sizes and types. Among them, airflow inertial separation removes large particles of impurities first, reducing the load on subsequent processes; electrostatic adsorption uses the charge difference between powder and impurities to remove submicron-sized particles; ultrasonic sieving removes impurities adhering to the powder surface and simultaneously deagglomerates powder, preventing screen clogging. The three processes form a synergistic purification system of "coarse filtration-fine filtration-supplementary filtration". S3, Dual-channel online monitoring: Real-time online detection of the separated powder. The elemental type and content of metallic impurities are detected by laser-induced breakdown spectroscopy (LIBS), and the content and particle size distribution of non-metallic impurities are detected by light scattering particle counter. The detection response time is ≤1s, achieving full coverage detection of metallic and non-metallic impurities with no detection blind spots. S4, Closed-loop control and finished product output: The online detection data is compared with the preset impurity threshold. If the detection result meets the preset threshold, the finished powder is output for aseptic packaging; if it does not meet the threshold, the process parameters of the multi-field collaborative separation in step S2 are fed back for adjustment, and the unqualified powder is cyclically processed until the powder meets the threshold requirements, realizing fully automated closed-loop control of "detection-judgment-adjustment".

[0008] In a preferred embodiment, in step S2, the process parameters for the airflow inertial separation are: a classifier wheel speed of 7000~9000 rpm and an airflow velocity of 18~22 m / s, used to remove large particulate impurities with a particle size >10 μm and fibrous impurities, with a removal efficiency ≥99%.

[0009] In a preferred embodiment, in step S2, the process parameters for electrostatic adsorption separation are: electrostatic field strength 36kV / cm, electrode spacing 46cm, used to remove microparticles and metal oxide impurities with a particle size of 0.1~10μm, with a removal efficiency ≥99.9%; the surface of the electrostatic adsorption electrode is coated with a TiO2 nano self-cleaning coating to achieve continuous operation without consumables and avoid secondary pollution introduced by frequent replacement of consumables.

[0010] In a preferred embodiment, in step S2, the process parameters for ultrasonic sieving and separation are: ultrasonic frequency 35~45kHz, amplitude 8~12μm, used to peel off impurities adhering to the powder surface and deagglomerate powder, with a removal efficiency ≥99.5%, while avoiding screen clogging, and improving the sieving efficiency by more than 300% compared with conventional vibrating screens.

[0011] In a preferred embodiment, in step S3, the detection limit of the laser-induced breakdown spectrum is 0.1 ppm, the particle size resolution of the light scattering particle counter is 0.1 μm, and the counting accuracy is ±1 particle / mL, which meets the high-precision detection requirements at the 10 ppm level.

[0012] In a preferred embodiment, in step S4, the preset impurity threshold is ≤10ppm total impurity content in the powder; during the closed-loop control process, at least one parameter among electrostatic field strength, ultrasonic amplitude, and classifying wheel speed is automatically adjusted by the PLC system. When equipment malfunctions or impurities exceed the standard, an audible and visual alarm is triggered, and unqualified powder is automatically diverted to the recycling bin to prevent unqualified products from flowing into the finished product stage.

[0013] In addition, this application also proposes a powder finished product impurity control system for implementing the above method, including a vacuum sealed conveying module, a multi-field collaborative separation module, a dual-path online monitoring module, and a closed-loop control module connected in sequence. The vacuum-sealed conveying module includes a vacuum feeder and a stainless steel sealed pipe with polished inner wall. The vacuum degree of the vacuum feeder is adjustable from -0.06 to -0.1 MPa. The multi-field collaborative separation module includes an air classifier, an electrostatic adsorption chamber, and an ultrasonic vibrating screen connected in sequence. The air classifier is equipped with a variable frequency speed control unit, the electrode plates of the electrostatic adsorption chamber are equipped with a self-cleaning device, and the ultrasonic vibrating screen is equipped with an amplitude sensor. The dual-channel online monitoring module includes a laser-induced breakdown spectroscopy sensor and a light scattering particle counter, both of which are installed at the outlet of the multi-field collaborative separation module; The closed-loop control module includes a PLC controller and a human-machine interface touch screen. The PLC controller is electrically connected to a multi-field collaborative separation module and a dual-channel online monitoring module.

[0014] In a preferred embodiment, the positive and negative electrode surfaces of the electrostatic adsorption chamber are coated with a TiO2 nano-self-cleaning coating. The self-cleaning device is a pulse backflushing unit matched with the electrode plates, with a pulse backflushing pressure of 0.2~0.4MPa. It can clean the impurities adsorbed on the electrode plate surface through pulse airflow, without the need to stop the machine to replace consumables, thus realizing continuous production.

[0015] A preferred embodiment further includes a nitrogen protection auxiliary module, which is connected to the vacuum sealed conveying module and the multi-field collaborative separation module to control the oxygen content in the system to be <10ppm, preventing the metal powder from oxidizing and generating new oxide impurities during the processing, while avoiding safety risks from flammable and explosive powders.

[0016] In a preferred embodiment, the PLC controller is a Siemens S7-1500 series controller, and the human-machine interface touch screen displays data such as impurity content, separation process parameters, equipment operating status, and alarm information in real time. It also supports manual modification of process parameters, preset impurity thresholds, and export of historical data, and can adapt to the processing needs of different powder materials.

[0017] Due to the application of the above technical solution, the beneficial effects of this application compared with the prior art are as follows: 1. Breakthrough in impurity removal precision, solving the core pain point of incomplete removal of tiny impurities in existing technologies: This invention achieves full coverage removal of all sizes and types of impurities above 0.1μm through a three-stage multi-field synergistic purification system of "airflow inertial separation - electrostatic adsorption separation - ultrasonic sieving separation". It can stably reduce the total impurity content of the powder product to ≤10ppm, which is 99% lower than the ≥1000ppm of the existing technology; the removal rate of 0.1-10μm submicron impurities is >99.9%, which is 49.9% higher than the existing technology, fully meeting the extreme requirements of powder purity in high-end fields such as aerospace and medical implants.

[0018] 2. Full-process pollution control, completely solving the problem of secondary pollution: This invention isolates external impurities through full-process vacuum closed conveying, and the ultra-smooth inner wall pipe reduces powder residue and pipe wall wear. The static electrode plate with TiO2 nano self-cleaning coating, together with the pulse backflushing unit, realizes consumable-free operation, eliminating the need for frequent replacement of consumables such as screens and filter membranes. This reduces the risk of secondary pollution from >5% in the existing technology to <0.1%, ensuring the long-term batch stability of the purity of the finished powder product.

[0019] 3. Millisecond-level online monitoring and closed-loop control completely solve the problem of detection lag: This invention adopts dual-channel online monitoring of laser-induced breakdown spectroscopy (LIBS) and light scattering particle counter, with a detection response time of ≤1s, which is 7200 times faster than the existing technology of >2 hours. Combined with the PLC fully automated closed-loop control system, it realizes real-time control of impurity content and dynamic adjustment of process parameters, completely avoiding the problem of batch product scrapping caused by offline detection lag, and improving the product yield to over 99.5%.

[0020] 4. High efficiency and low cost, suitable for industrial mass production needs: The powder processing efficiency of this invention is ≥100kg / h, which is 233% higher than the <30kg / h of the existing technology; the consumable-free design reduces the operating cost from >5000 yuan / ton of the existing technology to <2500 yuan / ton, a reduction of more than 50%; at the same time, the equipment can run continuously for ≥720 hours without failure, taking into account both high performance and the economic needs of industrial mass production.

[0021] 5. Strong compatibility and wide range of applications: This invention can be adapted to the purification needs of various powder materials such as titanium alloys, high-temperature alloys, ceramics, and polymers by adjusting process parameters. It can be widely used in aerospace, medical implants, electronic packaging, powder metallurgy and other fields, solving the defect of existing technologies that can only adapt to a single type of powder. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a process flow diagram of a method for preventing impurities and foreign matter from entering a finished powder product according to the present invention. Figure 2 This is an overall structural block diagram of a powder finished product impurity control system according to the present invention; Figure 3 This is a schematic diagram of the internal structure of the multi-field collaborative separation module of the present invention; The components include: 1. Vacuum-sealed conveying module; 11. Vacuum feeder; 12. Stainless steel sealed pipeline; 2. Multi-field collaborative separation module; 21. Air classifier; 22. Electrostatic adsorption chamber; 23. Ultrasonic vibrating screen; 3. Dual-channel online monitoring module; 31. Laser-induced breakdown spectrum sensor; 32. Light scattering particle counter; 4. Closed-loop control module; 41. PLC controller; 42. Human-machine interface touch screen. Detailed Implementation

[0024] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0025] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0026] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing the invention and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0027] Furthermore, in addition to indicating direction or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in certain situations to indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0028] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] Please see Figures 1-3 In the embodiments of this invention, the raw material powders used are all industrially prepared powder raw materials, and the equipment used are all industrial-grade general equipment. The impurity content detection is performed in accordance with GB / T 39252-2020 "Characteristics of Additive Manufacturing Metal Powder Performance", and offline verification detection is performed using inductively coupled plasma mass spectrometry (ICP-MS) and scanning electron microscopy (SEM).

[0031] I. Overall Structure and Working Principle of Powder Finished Product Impurity Control System The powder finished product impurity control system of this invention is a fully enclosed, integrated powder purification system that enables continuous and automated impurity control from raw material powder feeding to finished powder discharge, eliminating external pollution and secondary pollution at the source. The entire system is connected sequentially through 316L stainless steel sealed pipelines 12, with no open links throughout the process. The oxygen content, pressure, and process parameters within the system can be controlled in real time through the closed-loop control module 4, making it suitable for continuous purification production of various types of powders such as metals, ceramics, and polymers.

[0032] The core structure of the system includes a vacuum-sealed conveying module 1, a multi-field collaborative separation module 2, a dual-path online monitoring module 3, and a closed-loop control module 4, with a nitrogen protection auxiliary module as a supporting component. The specific structure, connection relationship, and working principle of each module are as follows: 1. Vacuum-sealed conveyor module 1 The vacuum-sealed conveying module 1 is the system's feeding unit and serves as the first line of defense against external impurities. Its outlet is sealed to the inlet of the multi-field collaborative separation module 2. This module includes an explosion-proof vacuum feeder 11, a stainless steel sealed pipe 12 with an ultra-smooth polished inner wall, a vacuum adjustment unit, and vacuum sealing connectors. The vacuum feeder 11 has an adjustable vacuum range of -0.06 to -0.1 MPa, allowing for real-time adjustment based on powder type and conveying volume. The stainless steel sealed pipe 12 has a polished inner wall with a polishing precision Ra < 0.2 μm, eliminating dead corners and protruding weld seams, thus preventing secondary metal contamination from powder residue and pipe wall wear. All pipe connections utilize wear-resistant fluororubber vacuum seals, ensuring a system leakage rate ≤ 10%. -9 Pa•m 3 It completely isolates external impurities such as air, dust, and fibers; the vacuum regulating unit is electrically connected to the closed-loop control module 4, which can stabilize the pressure fluctuation in the pipeline in real time to <±0.002MPa, ensuring that the powder conveying speed is stable at 8~12m / s, and avoiding powder agglomeration or pipeline erosion and wear.

[0033] 2. Multi-field collaborative separation module 2 The multi-field synergistic separation module 2 is the core purification unit of the system, used to achieve gradient removal of impurities of all sizes and types in the powder. It is a vertical coaxial series closed structure, connected from top to bottom to the air classifier 21, the electrostatic adsorption chamber 22, and the ultrasonic vibrating screen 23. Under the drive of gravity and inert carrier gas, the powder completes the three-stage synergistic separation process in sequence. There is no material spillage, no consumable replacement, and no risk of secondary pollution throughout the process.

[0034] Air classifier 21 (first-stage coarse separation unit): Equipped with a variable frequency speed control motor and a high-precision classifying wheel, the classifying wheel speed is adjustable from 7000 to 9000 rpm. The classifier cavity is equipped with an adjustable air inlet, which can control the airflow speed in the cavity from 18 to 22 m / s. The variable frequency speed control unit is electrically connected to the closed-loop control module 4, which can dynamically adjust the classification parameters according to online monitoring data, accurately remove large particle impurities with a particle size >10μm and fibrous impurities, while avoiding the loss of qualified powder.

[0035] Electrostatic adsorption chamber 22 (secondary fine separation unit): The inlet is sealed and connected to the outlet of the air classifier 21. Positive and negative plates are arranged in parallel inside the chamber with a plate spacing of 4~6cm. The high-voltage power supply unit can adjust the electrostatic field strength from 3~6kV / cm. The surfaces of both positive and negative plates are coated with a TiO2 nano self-cleaning coating, which can prevent the adsorption efficiency from decreasing due to long-term adhesion of impurities to the plates. The chamber is equipped with a pulse backflushing self-cleaning device with a pulse backflushing pressure of 0.2~0.4MPa, which can clean the impurities on the plate surface without stopping the machine, without replacing filter consumables, and realize continuous production. The high-voltage power supply unit and the pulse backflushing unit are electrically connected to the closed-loop control module 4, which can dynamically adjust the electrostatic field strength and backflushing cycle according to online monitoring data.

[0036] Ultrasonic vibrating screen 23 (three-stage separation unit): The feed inlet is sealed and connected to the discharge outlet of the electrostatic adsorption chamber 22. The screen is made of wear-resistant, non-magnetic stainless steel. It is equipped with an ultrasonic transducer and an amplitude sensor. The ultrasonic frequency is adjustable from 35 to 45 kHz, and the amplitude is adjustable from 8 to 12 μm. Through high-frequency ultrasonic vibration, it can peel off the tiny impurities adhering to the powder surface and deagglomerate the powder, thus avoiding screen clogging at the source. The screening efficiency is improved by more than 300% compared with conventional vibrating screens. The ultrasonic transducer and amplitude sensor are electrically connected to the closed-loop control module 4, which can dynamically adjust the ultrasonic parameters according to online monitoring data.

[0037] 3. Dual-channel online monitoring module The dual-path online monitoring module 3 is installed at the outlet pipe of the multi-field collaborative separation module 2. It is used for real-time, online, non-contact detection of the purified powder, achieving full coverage detection of metallic and non-metallic impurities without any blind spots. This module includes a laser-induced breakdown spectroscopy sensor 31 and a light scattering particle counter 32, both of which are electrically connected to the closed-loop control module 4, with a detection response time ≤1s.

[0038] Laser-induced breakdown spectroscopy sensor 31: used for real-time detection of the types and contents of metallic impurity elements in powders, with a detection limit of up to 0.1 ppm. It can preset corresponding characteristic peak detection wavelengths for different powders such as titanium alloys, ceramics, and polymers, accurately identify trace metallic impurities such as Fe, Cu, Al, and Cr, and output detection data in real time.

[0039] Light scattering particle counter 32: Used for real-time detection of non-metallic impurity content and particle size distribution in powder, with a particle size resolution of up to 0.1μm and a counting accuracy of ±1 particle / mL. It can accurately identify non-metallic impurity particles such as SiO2 and Al2O3, and simultaneously detect the particle size distribution and agglomeration state of the powder.

[0040] 4. Closed-loop control module 4 The closed-loop control module 4 serves as the system's control center, comprising a PLC controller 41 and a human-machine interface touchscreen 42. The PLC controller 41 is electrically connected to the vacuum-sealed conveying module 1, the multi-field collaborative separation module 2, the dual-channel online monitoring module 3, and the nitrogen protection auxiliary module, enabling the entire system to acquire data, make logical judgments, automatically adjust parameters, issue alarms, and store data. The PLC controller 41 uses a Siemens S7-1500 series controller, which can preset process parameter thresholds and impurity content thresholds for different powders. It receives real-time detection data from the dual-channel online monitoring module 3, compares it with the preset thresholds, and automatically adjusts process parameters such as the classifier wheel speed, electrostatic field strength, and ultrasonic frequency / amplitude, achieving fully automated closed-loop control of "detection-judgment-adjustment-verification." The human-machine interface touchscreen 42 can display impurity content, process parameters of each module, equipment operating status, and alarm information in real time. It supports manual modification of process parameters, threshold presets, and export of historical operating data, adapting to the processing needs of different powder materials.

[0041] 5. Nitrogen protection auxiliary module The nitrogen protection auxiliary module is in sealed connection with the vacuum sealed conveying module 1 and the multi-field collaborative separation module 2, and includes a high-purity nitrogen source, a pressure reducing valve, an oxygen content sensor, and a flow regulating valve. It can control the oxygen content in the system to be <10ppm in real time. On the one hand, it prevents the oxidation of active metal powders such as titanium alloys and high-temperature alloys during the processing, thus preventing the generation of new oxide impurities. On the other hand, it avoids safety risks caused by flammable and explosive polymer powders. At the same time, it provides inert carrier gas for powder conveying, ensuring the stable flow of powder in the system.

[0042] Overall system workflow: The raw material powder is conveyed to the multi-field co-separation module 2 in a high-vacuum inert environment via the vacuum-sealed conveying module 1. It then passes through the air classifier 21 to remove large particles of impurities, the electrostatic adsorption chamber 22 to remove submicron-sized micro-impurities, and the ultrasonic vibrating screen 23 to remove adhering impurities and deagglomerated powder. The purified powder flows through the dual-path online monitoring module 3 to detect the impurity content in real time. If the detection result meets the preset threshold, the powder enters the finished product warehouse for vacuum aseptic packaging. If it does not meet the threshold, the PLC controller 41 automatically adjusts the process parameters of the multi-field co-separation module 2, and the powder is returned to the separation module for recycling until it meets the threshold requirements. The entire process achieves fully enclosed, automated, and closed-loop control for impurity prevention and control.

[0043] Example 1 This embodiment addresses impurity control in TC4 titanium alloy powder used for aerospace 3D printing, employing the method and system of this invention. The specific steps are as follows: S1, Vacuum-sealed conveying: The TC4 titanium alloy raw material powder prepared by gas atomization (with an initial impurity content of 1260ppm) is fed into a sealed stainless steel pipe through a vacuum feeder 11. The vacuum degree is controlled at -0.08MPa, the inner wall of the pipe is polished to Ra<0.1μm, the conveying speed is 10m / s, the pipe pressure fluctuation is <±0.001MPa, and the oxygen content in the system is controlled to <10ppm through a nitrogen protection auxiliary module throughout the process to prevent external contamination and powder oxidation. S2, Multi-field Coordinated Separation: The conveyed powder undergoes a three-stage coordinated separation process sequentially. First-stage airflow inertial separation: the classifier wheel rotates at 8000 rpm and the airflow velocity is 18 m / s, removing large particulate impurities and organic fibers with a particle size >10 μm, with a removal efficiency of 99.2%; Two-stage electrostatic adsorption separation: electrostatic field strength 4.5kV / cm, electrode spacing 5cm, electrode surface coated with TiO2 nano self-cleaning coating, removes TiO2 and other oxide impurities and tiny metal particles with a particle size of 0.1-10μm, with a removal efficiency of 99.92%; Three-stage ultrasonic sieving and separation: ultrasonic frequency 38kHz, amplitude 10μm, removes impurities adhering to the powder surface and deagglomerates the powder, with a removal efficiency of 99.6%; S3, Dual-channel online monitoring: The Ti characteristic peak at 394.4 nm is detected by a LIBS sensor, and the content of metallic impurities such as Fe, Cu, and Al is detected in real time with a detection limit of 0.1 ppm and a response time of 0.5 s; the non-metallic impurities such as SiO2 and Al2O3 and their particle size distribution are detected by a light scattering particle counter 32 with a particle size resolution of 0.1 μm. S4, Closed-loop control and finished product output: The preset impurity threshold is ≤10ppm for total impurity content. The PLC system compares the detection data with the preset threshold in real time. In this embodiment, the detection result is 8.2ppm for total impurity content, which meets the threshold requirement. The finished powder is then output for vacuum aseptic packaging.

[0044] Offline ICP-MS and SEM verification showed that the TC4 titanium alloy powder prepared in this embodiment had a total impurity content of 8.2 ppm, a 0.1-0.5 μm submicron impurity removal rate of 99.93%, a processing efficiency of 120 kg / h, no secondary pollution after 72 hours of continuous operation, and an operating cost of 2200 yuan / ton, which is far superior to existing technical indicators and fully meets the requirements for aerospace 3D printing.

[0045] Example 2 Please see Figures 1-3 This embodiment addresses the control of impurities in alumina ceramic powder for medical implants, employing the method and system of this invention. The specific steps are as follows: S1, Vacuum-sealed conveying: The alumina ceramic raw material powder (initial impurity content 980ppm) prepared by sintering and crushing is fed into a sealed stainless steel pipe through a vacuum feeder 11, with the vacuum degree controlled at -0.09MPa, the inner wall of the pipe polished Ra<0.1μm, the conveying speed at 11m / s, and the pipe pressure fluctuation <±0.001MPa. S2, Multi-field Coordinated Separation: The conveyed powder undergoes a three-stage coordinated separation process sequentially. First-stage airflow inertial separation: the classifier wheel rotates at 8500 rpm, the airflow velocity is 22 m / s, and it removes large particulate impurities and fibers with a particle size >10 μm, with a removal efficiency of 99.1%. Two-stage electrostatic adsorption separation: electrostatic field strength 5.5kV / cm, electrode spacing 5cm, electrode surface coated with TiO2 nano self-cleaning coating, removes metal particle impurities with a particle size of 0.1-10μm, with a removal efficiency of 99.91%; Three-stage ultrasonic sieving and separation: ultrasonic frequency 42kHz, amplitude 10μm, removes impurities adhering to the powder surface and deagglomerates the powder, with a removal efficiency of 99.5%; S3, Dual-channel online monitoring: Detects the Al characteristic peak at 396.1nm using a LIBS sensor, and detects the content of metallic impurities such as Fe, Cr, and Ni in real time, with a detection limit of 0.1ppm and a response time of 0.5s; Detects the content and particle size distribution of non-metallic impurities such as SiO2 using a light scattering particle counter 32, with a particle size resolution of 0.1μm. S4, Closed-loop control and finished product output: The preset impurity threshold is ≤10ppm for total impurity content. The PLC system compares the detection data with the preset threshold in real time. In this embodiment, the detection result is 7.6ppm for total impurity content, which meets the threshold requirement. The finished powder is then output for aseptic packaging.

[0046] Offline testing and verification showed that the alumina ceramic powder prepared in this embodiment had a total impurity content of 7.6 ppm, a non-metallic impurity removal rate of 99.88%, a processing efficiency of 110 kg / h, no screen clogging after 48 hours of continuous operation, and an operating cost of 2350 yuan / ton, fully meeting the biosafety requirements for medical implants.

[0047] Example 3 Please see Figures 1-3 This embodiment addresses the control of impurities in polyethylene powder used for electronic packaging, employing the method and system of this invention. The specific steps are as follows: S1, Vacuum-sealed conveying: The polyethylene raw material powder (initial impurity content 850ppm) prepared by melt extrusion is fed into a sealed stainless steel pipe through a vacuum feeder 11, with the vacuum degree controlled at -0.07MPa, the inner wall of the pipe polished Ra<0.15μm, the conveying speed at 9m / s, and the pipe pressure fluctuation <±0.002MPa. S2, Multi-field Coordinated Separation: The conveyed powder undergoes a three-stage coordinated separation process sequentially. Primary airflow inertial separation: The classifier rotates at 7500 rpm, and the airflow velocity is 15 m / s. It removes large particulate impurities and fibers with a particle size >10 μm, with a removal efficiency of 99.0%. Two-stage electrostatic adsorption separation: electrostatic field strength 3.5kV / cm, electrode spacing 5cm, electrode surface coated with TiO2 nano self-cleaning coating, removes metal particle impurities with a particle size of 0.1-10μm, with a removal efficiency of 99.90%; Three-stage ultrasonic sieving and separation: ultrasonic frequency 35kHz, amplitude 8μm, removes impurities adhering to the powder surface and deagglomerates the powder, with a removal efficiency of 99.5%; S3, Dual-channel online monitoring: Detects the C characteristic peak at 283.3nm using a LIBS sensor, and monitors the content of metallic impurities such as Na, K, and Fe in real time, with a detection limit of 0.1ppm and a response time of 0.8s; Detects the content and particle size distribution of non-metallic impurities using a light scattering particle counter 32, with a particle size resolution of 0.1μm; S4, Closed-loop control and finished product output: The preset impurity threshold is ≤10ppm total impurity content. In this embodiment, the initial detection result is 12.3ppm, which does not meet the threshold requirement. The PLC system automatically increases the electrostatic field strength to 4kV / cm and the ultrasonic frequency to 36kHz. After circulating the powder, the online detection result is 8.8ppm, which meets the requirements, and the finished powder is output.

[0048] Offline testing and verification showed that the polyethylene powder prepared in this embodiment had a total impurity content of 8.8 ppm, a metal impurity removal rate of 99.92%, a processing efficiency of 105 kg / h, a closed-loop control response time of 0.8 s, and no batches of unqualified products were generated, fully meeting the requirements for electronic packaging.

[0049] Comparative Example 1 This comparative example uses a multi-stage sieving-filtration system based on existing technology to process the same TC4 titanium alloy raw material powder (initial impurity content 1260ppm) as in Example 1. The specific process is as follows: sieving is performed using a three-stage vibrating screen with 200 mesh, 400 mesh and 800 mesh, followed by filtration with a 0.5μm pore size microporous filter membrane, offline detection is performed using a laser particle size analyzer, and packaging is done after passing the test.

[0050] Testing revealed that the TC4 titanium alloy powder prepared in this comparative example had a final impurity content of 1080 ppm, a 0.1-0.5 μm submicron impurity removal rate of 42%, a processing efficiency of 28 kg / h, and an operating cost of 5200 yuan / ton. After 72 hours of continuous operation, the content of metal impurities increased by 120 ppm due to screen wear, indicating a significant risk of secondary pollution.

[0051] Comparative Example 2 This comparative example uses the existing airflow classification-magnetic separation combined process to process the same alumina ceramic raw material powder (initial impurity content 980ppm) as in Example 2. The specific process is as follows: airflow classification with a classification wheel speed of 6000rpm, combined with processing by a 1.5T high gradient magnetic separator, and packaging after offline testing and passing the test.

[0052] Testing revealed that the alumina ceramic powder prepared in this comparative example had a final impurity content of 760 ppm, a non-metallic impurity removal rate of 22%, and a magnetic metallic impurity removal rate of 95%. However, it was unable to remove non-metallic impurities such as SiO2, indicating a significant detection blind spot and failing to meet the requirements for use in medical implants.

[0053] The comparison between the embodiments and comparative examples clearly shows that the present invention has achieved a significant improvement over the prior art in terms of impurity removal accuracy, processing efficiency, operating cost, and secondary pollution prevention and control, and has outstanding technical advantages.

[0054] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 preventing impurities and foreign matter from entering a finished powder product, characterized in that, Includes the following steps: S1, Vacuum-sealed conveying: The raw material powder is placed in a sealed conveying environment with a vacuum degree of -0.06~-0.1MPa and conveyed through a stainless steel pipe with an inner wall polished Ra<0.2μm. The conveying speed is controlled at 8~12m / s and the pressure fluctuation inside the pipe is <±0.002MPa. The vacuum environment isolates external impurities from entering, and the inner wall polishing of the pipe reduces secondary pollution caused by powder residue and pipe wall wear. S2, Multi-field Synergistic Separation: The conveyed powder undergoes three-stage synergistic separation processes: airflow inertial separation, electrostatic adsorption separation, and ultrasonic sieving separation, to remove impurities of all sizes and types. Among them, airflow inertial separation first removes large particles of impurities to reduce the load on subsequent processes, electrostatic adsorption uses the charge difference between powder and impurities to remove submicron-sized particles, and ultrasonic sieving removes impurities adhering to the powder surface and deagglomerates the powder. The three processes form a synergistic purification system. S3, Dual-channel online monitoring: Real-time online detection of the separated powder, using laser-induced breakdown spectroscopy to detect the content of metal impurities, and using a light scattering particle counter to detect non-metallic impurities and particle size distribution, with a detection response time ≤1s; S4, Closed-loop control and finished product output: The online detection data is compared with the preset impurity threshold. If the detection result meets the preset threshold, the finished product powder is output; if it does not meet the threshold, the process parameters of the multi-field collaborative separation in step S2 are fed back for adjustment until the powder meets the threshold requirements, realizing fully automated closed-loop control of "detection-judgment-adjustment".

2. The method for preventing impurities and foreign matter from entering the finished powder product according to claim 1, characterized in that, In step S2, the process parameters for the airflow inertial separation are: the classifier wheel speed is 7000~9000 rpm, the airflow velocity is 18~22 m / s, which is used to remove large particulate impurities with a particle size >10μm and fibrous impurities, with a removal efficiency ≥99%.

3. The method for preventing impurities and foreign matter from entering the finished powder product according to claim 1, characterized in that, In step S2, the process parameters for electrostatic adsorption separation are: electrostatic field strength 36kV / cm, electrode spacing 46cm, used to remove tiny particles and metal oxide impurities with a particle size of 0.1~10μm, with a removal efficiency ≥99.9%; the surface of the electrostatic adsorption electrode is coated with a TiO2 nano self-cleaning coating.

4. The method for preventing impurities and foreign matter from entering the finished powder product according to claim 1, characterized in that, In step S2, the process parameters for ultrasonic sieving and separation are: ultrasonic frequency 35~45kHz, amplitude 8~12μm, used to peel off impurities adhering to the powder surface and deagglomerate the powder, with a removal efficiency ≥99.5%.

5. The method for preventing impurities and foreign matter from entering the finished powder product according to claim 1, characterized in that, In step S3, the detection limit of the laser-induced breakdown spectrum is 0.1 ppm, the particle size resolution of the light scattering particle counter is 0.1 μm, and the counting accuracy is ±1 particle / mL.

6. The method for preventing impurities and foreign matter from entering the finished powder product according to claim 1, characterized in that, In step S4, the preset impurity threshold is ≤10ppm total impurity content in the powder; during the closed-loop control process, at least one of the parameters of electrostatic field strength, ultrasonic amplitude, and classifying wheel speed is automatically adjusted by the PLC system. When an abnormality occurs, an alarm is triggered and unqualified powder is automatically diverted.

7. A powder product impurity control system for implementing the method of any one of claims 1-6, characterized in that, It includes a vacuum-sealed delivery module, a multi-field collaborative separation module, a dual-path online monitoring module, and a closed-loop control module, which are connected sequentially through a sealed pipeline. The vacuum-sealed conveying module includes a vacuum feeder and a stainless steel sealed pipe with polished inner wall. The vacuum degree of the vacuum feeder is adjustable from -0.06 to -0.1 MPa. The multi-field collaborative separation module includes an air classifier, an electrostatic adsorption chamber, and an ultrasonic vibrating screen that are sequentially and sealed together. The air classifier is equipped with a variable frequency speed control unit, the plates of the electrostatic adsorption chamber are equipped with a self-cleaning device, and the ultrasonic vibrating screen is equipped with an amplitude sensor. The dual-channel online monitoring module includes a laser-induced breakdown spectroscopy sensor and a light scattering particle counter, both of which are installed at the outlet pipe of the multi-field collaborative separation module. The closed-loop control module includes a PLC controller and a human-machine interface touch screen. The PLC controller is electrically connected to a multi-field collaborative separation module and a dual-channel online monitoring module.

8. The powder finished product impurity control system according to claim 7, characterized in that, The positive and negative electrode surfaces of the electrostatic adsorption chamber are coated with a TiO2 nano self-cleaning coating. The self-cleaning device is a pulse backflush unit matched with the electrode plates, and the pulse backflush pressure is 0.2~0.4MPa.

9. The powder finished product impurity control system according to claim 7, characterized in that, It also includes a nitrogen protection auxiliary module, which is in sealed connection with the vacuum sealed delivery module and the multi-field collaborative separation module to control the oxygen content in the system to be <10ppm.

10. The powder finished product impurity control system according to claim 7, characterized in that, The PLC controller adopts the Siemens S7-1500 series controller. The human-machine interface touch screen displays the impurity content, separation process parameters, and equipment operating status in real time, and supports manual parameter modification and threshold preset.

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