Micro-nano multi-stage vortex air classification system and method with continuous self-cleaning

Abstract

The application discloses a micro-nano multi-section vortex air grading system and method capable of continuous grading and self-cleaning, comprising a primary vortex air classifier and two secondary vortex air classifiers, one of which is used as a standby machine; a PTFE membrane filter screen and a cleaning system are additionally arranged in the secondary vortex air classifier; the primary vortex air classifier is uniformly fed by a vibrating feeder at a constant speed to classify the original powder into micron powder, the micron powder is classified into sub-micron powder through the secondary vortex air classifier and the PTFE membrane filter screen, and finally the ultra-fine powder in the sub-micron powder is collected through an electrostatic dust collector. The particle size range of the fine powder product obtained after grading is obviously narrowed, and the particle size is smaller; when the filter screen in the working secondary classifier is blocked, the PTFE membrane filter screen and the conical discharge hopper area are back-flushed by using high-pressure gas and cleaning nozzles to realize self-cleaning, thereby improving the production efficiency.

Description

Technical Field

[0001] This invention belongs to the technical field of dry preparation methods for ultrafine powders, specifically relating to a micro-nano level multi-segment vortex air classification system that can be continuously classified and self-cleaned; and also relating to a micro-nano level multi-segment vortex air classification method that can be continuously classified and self-cleaned. Background Technology

[0002] In the field of dry preparation of ultrafine powders, with the continuous development of modern industry, the demand for ultrafine powders is increasing day by day, and its application scope covers many key fields such as electronics, medicine, chemical industry, and materials.

[0003] Traditional dry-process equipment for preparing ultrafine powders suffers from numerous problems in practical operation. On one hand, the classification efficiency is low, making it difficult to meet the stringent requirements of large-scale industrial production in terms of both output and quality. Existing classifiers often fail to completely separate coarse and fine particles during powder classification, resulting in uneven particle size distribution and impacting the product's performance in high-end applications. For example, in the preparation of electronic materials, ultrafine powders with uneven particle size distribution may lead to unstable performance of electronic components.

[0004] On the other hand, cleaning the equipment cavities has always been a challenging problem in the industry. During long-term production, powder particles easily adhere to and accumulate on the inner walls of the equipment cavities and on critical components. This accumulated powder not only affects the normal operation of the equipment and reduces grading accuracy, but may also pose safety hazards. For example, in the preparation of some flammable and explosive powders, the accumulated powder may cause an explosion due to friction. Currently, the most common cleaning method is manual disassembly and cleaning, which not only consumes a lot of manpower, resources, and time, but may also damage the equipment during disassembly and installation, affecting its service life and stability.

[0005] In summary, developing a dry process for preparing ultrafine powders that can achieve efficient classification and has a self-cleaning chamber function is of great practical significance and has an urgent market demand. This is precisely the original intention behind the development of the micro-nano level multi-segment vortex air classification system with continuous classification and self-cleaning in this invention. Summary of the Invention

[0006] The purpose of this invention is to provide a micro-nano level multi-segment vortex air classification system that can continuously classify and self-clean, which solves the problem that current dry-process equipment for preparing ultrafine powders often has problems such as incomplete separation of coarse and fine particles and inconvenience in cleaning when classifying powders.

[0007] The first technical solution adopted in this invention is a continuously self-cleaning micro-nano level multi-segment vortex air classification system, including a primary vortex air classifier, two secondary vortex air classifiers connected in series on the primary vortex air classifier to achieve two-stage classification, one of which serves as a backup; the secondary vortex air classifiers are equipped with PTFE membrane filters and a cleaning system to achieve continuous classification; the secondary vortex air classifiers are connected to an electrostatic precipitator to collect the classified fine powder; the electrostatic precipitator is connected to the two secondary vortex air classifiers respectively through a three-way pipe; a pneumatic reversing valve is installed on the pipeline connecting the primary vortex air classifier to the two secondary vortex air classifiers to reverse the air path.

[0008] This invention achieves two-stage classification of materials by connecting two vortex air classifiers in series. The secondary vortex air classifier is equipped with a filter with replaceable filtration precision for further classification. At the same time, in order to avoid the classification interruption caused by filter clogging, a backup secondary classifier and a cleaning system are added to achieve continuous classification. The classified fine powder is collected by an electrostatic dust collector. The particle size range of the fine powder product obtained after classification is significantly narrowed, the particle size is smaller, and the classification output is increased. The invention is further characterized in that, The primary vortex air classifier has a feeding port on its upper cover housing. A vacuum chamber is connected below the upper cover housing. High-speed compressed gas is introduced into the vacuum chamber through its air inlet. The inner wall of the vacuum chamber is arranged in three layers, each layer with multiple second air nozzles, and the second air nozzles of adjacent layers are staggered. A rotating feeding disc is installed inside the vacuum chamber, driven by a stepper motor and bearings of the primary classifier. A vortex inlet pipe is located below the vacuum chamber. The airflow from the vortex inlet pipe enters the primary vortex air classifier through the main airflow inlet. Replaceable guide vanes are installed inside the vortex inlet pipe. A classification platform is located directly below the vortex inlet pipe, connected to the micro-powder output pipe via an adjusting ring a. The micro-powder output pipe extends out of the conical discharge hopper and connects to the inlet of the secondary classifier. A coarse powder collection chamber is connected below the conical discharge hopper. A pneumatic reversing valve is located on the outside of the conical discharge hopper where the micro-powder output pipe is located. The grading platform has a hollow center and smooth raised edges.

[0009] The two-stage vortex air classifier includes a main chamber with a secondary classifier inlet at the top. A PTFE-coated filter cylinder is installed inside the main chamber, with its upper part connected to a secondary powder output pipe. The secondary powder output pipe is connected to a T-junction pipe of the electrostatic precipitator. A longitudinal filter cleaning nozzle is located in the middle of the PTFE-coated filter cylinder, with its lower end connected to a cleaning system air supply pipe. Cleaning nozzles a and b are installed on the vertical section of the cleaning system air supply pipe within the main chamber. The cleaning system air supply pipe extends outward from the main chamber and connects to an air compressor. A normally closed butterfly valve is installed on the outer extension of the cleaning system air supply pipe. The lower part of the main chamber is connected to the powder collection chamber via an adjusting ring b and a vortex stabilizer.

[0010] The cleaning system includes a filter brush and a cavity brush. Both the filter brush and the cavity brush are connected to the cylinder piston via a brush holder. The cylinder connected to the cylinder piston is located in the upper part of the main cavity. The cavity brush is set close to the inner wall of the main cavity, and the filter brush is set close to the PTFE membrane filter cylinder. There are two sets of the cleaning system, which are symmetrically arranged on both sides of the PTFE membrane filter cylinder.

[0011] The electrostatic precipitator housing is equipped with an electrostatic precipitator inlet and an electrostatic precipitator outlet. Multiple layers of electrodes are installed inside the housing, with corona wires positioned between adjacent electrodes. The electrodes are fixedly connected to the upper part of the housing via tension springs. A rapping mechanism is connected to one side of the lower end of each electrode, comprising a rapping mechanism stepper motor and a crank connecting rod connected to the motor shaft. The end of the crank connecting rod contacts the electrode. The bottom of the electrostatic precipitator housing is hollowed out and connected to the fine powder collection chamber.

[0012] The second technical solution adopted in this invention is a continuous, self-cleaning, micro / nano-level multi-segment vortex air classification method. The method involves feeding the raw powder into a primary vortex air classifier at a uniform speed using a vibrating feeder to classify it into micron-sized powder. Then, the micron-sized powder is further classified into submicron-sized powder by a secondary vortex air classifier and filtered through a PTFE-coated filter. Finally, the ultrafine powder in the submicron-sized powder is collected using an electrostatic precipitator. The specific operation steps are as follows: Material is fed into the feeding port of the vortex air classifier via a vibrating feeding plate. After entering the classifier, the material falls into a rotating spreading disc, which disperses the material powder around the inner wall of the chamber. Compressed gas is ejected at high speed through the vacuum chamber inlet and the second air nozzle, breaking up any agglomerated powder particles. The broken particles fall downwards. Air entering through the main airflow inlet enters the chamber through the vortex inlet pipe and is classified by the vortex formed by the replaceable guide vanes. The separated coarse powder falls into the coarse powder collection chamber along the conical discharge hopper. The fine powder is drawn into the secondary stage due to the negative pressure of the fine powder output pipe. The main chamber of the vortex air classifier forms a swirling motion. Large particles of micro powder settle down to the conical discharge hopper and are finally collected in the micro powder collection chamber. Small particles of sub-micro powder are filtered through the PTFE membrane filter in the central area and then drawn away by negative pressure through the sub-micro powder output pipe into the electrostatic precipitator. The separated micro powder is discharged from the micro powder collection chamber. The particles are ionized by the corona wire in the electrostatic precipitator to generate charged ions, which cause the sub-micro powder to become charged and settle on the electrode plate. The vibrating mechanism then vibrates the electrode plate to make the fine powder fall into the fine powder collection chamber. Finally, the fine powder product is discharged from the fine powder collection chamber.

[0013] The beneficial effects of this invention are: Compared with the prior art, the present invention makes the following improvements to the existing air classifier: First, the classification system, consisting of two vortex air classifiers connected in series, effectively classifies the material in two stages. The built-in filter of the secondary vortex air classifier further classifies the powder. Finally, the fine powder is collected by an electrostatic dust removal system, which significantly narrows the particle size range of the fine powder product after classification, reduces the particle size, and increases the output.

[0014] Secondly, when the rotating feeding disc of the primary vortex air classifier disperses the material around the inner wall of the cavity, the high-pressure gas in the vacuum chamber blows away the agglomerated powder in the material through three layers of cross-distributed second air nozzles, six in each layer, thereby enabling the material to be better classified.

[0015] Third, a liftable grading platform is added below the grading area of ​​the primary vortex air classifier. For materials with different particle size distributions, the radial distance between the grading platform and the conical discharge hopper is adjusted by raising and lowering the grading platform to prevent ungraded particles from falling into the conical discharge hopper and causing errors.

[0016] Fourth, the two-stage vortex air classifier has a built-in replaceable PTFE membrane filter with different precision levels to block larger particles in the classified micron powder, preventing unclassified micron powder from appearing in the fine powder product, thereby achieving narrow-level classification at the micro-nano level.

[0017] Fifth, multiple backup secondary vortex air classifiers can be added to the two-stage classification process. When the PTFE membrane filter built into the working secondary classifier becomes clogged, the secondary classification can be switched to the backup secondary vortex air classifier through a pneumatic reversing valve, thereby achieving continuous classification.

[0018] Sixth, the secondary vortex air classifier is equipped with a self-cleaning system. When the pressure difference between the inlet and outlet pressure gauges of the secondary vortex air classifier is abnormal, the built-in PTFE membrane filter becomes clogged. After the reversing valve is activated to switch to the standby secondary vortex air classifier, the high-pressure gas in the cleaning pipeline and the cleaning nozzle backwash the clogged PTFE membrane filter and the conical discharge hopper area. Two parallel cylinders are set at the upper end of the main chamber. The pistons of the cylinders are connected to the brush brackets. The brush brackets are connected to the external chamber brushes and the internal filter brushes through spring pins. During the reciprocating motion of the pistons, the inner wall of the chamber and the outer wall of the filter are cleaned. The powder adhering to the filter and the inner wall of the chamber is collected into the micro powder collection chamber and discharged, completing the cleaning while increasing the output of powder separation micro powder.

[0019] Seventh, a vortex stabilizer is installed at the connection between the main chamber and the coarse powder collection chamber. This stabilizer provides a smooth surface to the tail of the vortex during separation, allowing the vortex to adhere and helping to stabilize it at the center, as well as preventing separated coarse particles from being re-entered into the vortex. During cleaning, it prevents coarse powder in the fine powder collection chamber from being blown back into the main chamber of the secondary vortex air classifier when the high-speed airflow is cleaning the inner wall of the conical discharge hopper area. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the micro-nano level multi-segment vortex air classification system of the present invention, which is capable of continuous classification and self-cleaning. Figure 2 This is a schematic diagram of the flow field and working process of the first-stage vortex air classifier of the present invention; Figure 3 This is an overall and cross-sectional schematic diagram of the first-stage vortex air classifier of the present invention; Figure 4 This is a schematic cross-sectional view of the internal structure of the first-stage vortex air classifier of the present invention. Figure 5 This is a schematic diagram of the flow field and working process of the two-stage vortex air classifier of the present invention; Figure 6 This is an overall and cross-sectional schematic diagram of the two-stage vortex air classifier of the present invention; Figure 7 These are enlarged schematic diagrams of the overall and partial electrostatic dust removal box of the present invention; Figure 8 This is a particle size distribution diagram of fine powder in Embodiment 6 of the present invention.

[0021] Figure 9 This is a flowchart of the workflow of the micro-nano level multi-segment vortex air classification method of the present invention, which is capable of continuous classification and self-cleaning.

[0022] In the diagram: 1. Stepper motor for primary classifier; 2. Bearing; 3. Feed inlet; 4. Rotary feeding disc; 5. Second air nozzle; 6. Vacuum chamber air inlet; 7. Main airflow inlet; 8. Vortex air inlet pipe; 9. Replaceable guide vane; 10. Classification platform; 11. Adjustable distance ring a; 12. Micro powder output pipe; 13. Conical discharge hopper; 14. Micro powder output port; 15. Coarse powder collection chamber; 16. Pneumatic reversing valve; 17. Pressure gauge a; 18. Pressure gauge b; 19. Secondary classifier inlet; 20. Cylinder; 21. Secondary micro powder output pipe; 22. Secondary classifier top cover; 23. Main chamber; 24. Cylinder piston; 25. Brush bracket; 26. 27. Spring plunger, 28. Cavity brush, 29. Filter brush, 30. Filter cleaning nozzle, 31. Cleaning nozzle a, 32. PTFE membrane filter, 33. Cleaning nozzle b, 34. Vortex stabilizer, 35. Adjustable ring b, 36. Fine powder collection chamber, 37. Cleaning system air supply pipe, 38. Cleaning pipe normally closed butterfly valve, 39. Pressure gauge c, 40. Output pipe normally open butterfly valve, 41. T-connector, 42. Electrostatic precipitator inlet, 43. Electrostatic precipitator body, 44. Tension spring, 45. Corona wire, 46. Electrode plate, 47. Electrostatic precipitator output port, 48. Vibration mechanism, 49. Vibration mechanism stepper motor, 40. Fine powder collection chamber. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0024] Example 1 This invention relates to a continuously self-cleaning, micro / nano-scale multi-segment vortex air classification system, such as... Figure 1-8 As shown, it includes a primary vortex air classifier, with two secondary vortex air classifiers connected in series to achieve two-stage classification, one of which serves as a backup. The secondary vortex air classifiers are equipped with PTFE membrane filters 31 and a cleaning system to achieve continuous classification. The secondary vortex air classifiers are connected to an electrostatic precipitator 42 to collect the classified fine powder. The electrostatic precipitator 42 is connected to the two secondary vortex air classifiers via a three-way pipe 40.

[0025] A pneumatic reversing valve 16 is installed on the pipeline connecting the first-stage vortex air classifier to the two second-stage vortex air classifiers to switch the air path; pressure gauges a17 and b18 are respectively installed on the pipeline connecting the two second-stage vortex air classifiers.

[0026] Example 2 Based on Embodiment 1, the upper cover of the primary vortex air classifier is provided with a feeding port 3, and a vacuum chamber is connected to the lower part of the upper cover. The inner wall of the vacuum chamber is arranged in three layers at intervals, and a vacuum chamber air inlet 6 is provided on the vacuum chamber. Each layer of the vacuum chamber has a second air nozzle 5, and the second air nozzles 5 of adjacent layers are staggered. A rotating material spreading disc 4 is provided inside the vacuum chamber, and the rotating material spreading disc 4 is driven to rotate by the primary classifier stepper motor 1 and bearing 2. A ring of vortex air inlet pipes 8 is provided below the vacuum chamber. The airflow from the shell inlet pipe 8 enters the interior of the first-stage vortex air classifier through the main airflow inlet 7. A replaceable guide vane 9 is installed inside the shell inlet pipe 8. A classification platform 10 is installed directly below the shell inlet pipe 8. The classification platform 10 is connected to the micro powder output pipe 12 through the adjustment ring a11. The micro powder output pipe 12 extends out of the conical discharge hopper 13 and is connected to the inlet 19 of the second-stage classifier. A coarse powder collection chamber 15 is connected below the conical discharge hopper 13. A pneumatic reversing valve 16 is located on the outside of the conical discharge hopper 13 of the micro powder output pipe 12. like Figure 4 As shown, the replaceable guide wing 9 includes an annular base, with multiple diffuser wings evenly distributed along the circumference of the annular base. The diffuser wings extend in a curved shape from the inner circumference to the outer circumference. An air gap is provided between adjacent diffuser wings, and the annular base and the diffuser wings are integrated.

[0027] The air gap angle between adjacent diffusers is 90 degrees to the center of the annular base, forming a swirling flow field.

[0028] The grading platform 10 has a hollow center and smooth raised edges.

[0029] The two-stage vortex air classifier provided by this invention, such as Figure 5-6 As shown, this is an improved version of a commonly used cyclone separator, with an internal cleaning system. The two-stage vortex air classifier includes a main chamber 23, with a secondary classifier inlet 19 at the top. A PTFE membrane filter cylinder 31 is installed inside the main chamber 23, and its upper part is connected to a secondary powder output pipe 21. The secondary powder output pipe 21 is connected to a three-way pipe 40 of the electrostatic precipitator housing 42. A longitudinal filter screen is installed in the middle of the PTFE membrane filter cylinder 31. The cleaning nozzle 29 is connected to the lower end of the filter cleaning nozzle 29 via a cleaning system air supply pipe 36. The cleaning system air supply pipe 36 is equipped with a cleaning nozzle a30 and a cleaning nozzle b32 on its vertical section inside the main cavity 23. The cleaning system air supply pipe 36 extends outward from the main cavity and is connected to an air compressor. A normally closed butterfly valve 37 is installed on the outer extension section of the cleaning system air supply pipe 36. The main cavity 23 is connected to the micro powder collection chamber 35 below via an adjusting ring b34 and a vortex stabilizer 33.

[0030] Example 3 Based on Example 2, the cleaning system includes a filter brush 28 and a cavity brush 27. Both the filter brush 28 and the cavity brush 27 are connected to the cylinder piston 24 via a brush holder 25. The cylinder 20 connected to the cylinder piston 24 is located on the upper part of the main cavity 23. The cavity brush 27 is set close to the inner wall of the main cavity 23, and the filter brush 28 is set close to the PTFE membrane filter cylinder 31. There are two sets of the cleaning system, which are symmetrically arranged on both sides of the PTFE membrane filter cylinder 31.

[0031] The electrostatic precipitator housing 42 is provided with an electrostatic precipitator inlet 41 and an electrostatic precipitator outlet 46. Multiple layers of electrode plates 45 are provided inside the electrostatic precipitator housing 42, and corona wires 44 are provided between adjacent electrode plates 45. The electrode plates 45 are fixedly connected to the upper part of the electrostatic precipitator housing 42 by tension springs 43. A rapping mechanism 47 is connected to one side of the lower end of the electrode plate 45. The rapping mechanism 47 includes a stepper motor 48 and a crank connecting rod connected to the motor shaft. The end of the crank connecting rod contacts the electrode plate 45. The bottom of the electrostatic precipitator housing 42 is hollowed out and connected to the fine powder collection chamber.

[0032] Example 4 The present invention provides a continuously graded, self-cleaning micro / nano-level multi-segment vortex air grading method, such as... Figure 9 As shown in the flowchart of the vortex air classification system, when an abnormal pressure difference is detected in pressure gauge a17 or pressure gauge b18, the PTFE membrane filter cylinder of the working secondary vortex air classifier may become clogged. The switching valve 16 automatically switches to another secondary vortex air classifier to achieve continuous classification. The classified powder flows into the three-way pipe 40 to enter the next stage. After the reversing valve 16 is automatically switched to another two-stage vortex air classifier, the clogged PTFE membrane filter cylinder 31 and the cavity are self-cleaned. At this time, the normally open butterfly valve 39 of the output pipe connected to the three-way pipe 40 is closed, and the normally closed butterfly valve 37 of the cleaning pipe connected to the cleaning system air supply pipe 36 is opened. The external air compressor inputs high-speed airflow to backflush the PTFE membrane filter cylinder 31 clogged by particles and the cleaning nozzles a30 and b32 connected to the cleaning system air supply pipe 36 to flush the conical discharge hopper area. The cylinder piston 24 of the cylinder 20 is connected to the brush bracket 25. The brush bracket 25 is connected to the external cavity brush 27 and the internal filter brush 28 through the spring pin 26. During the reciprocating motion of the piston, the inner wall of the cavity and the outer wall of the filter are cleaned. The powder attached to the filter and the inner wall of the cavity is collected into the micro powder collection chamber 35 and discharged to complete the cleaning while improving the output of powder separation micro powder.

[0033] The classifying platform 10 in the primary vortex air classifier can be raised and lowered by the adjusting ring a11. The radial distance between the classifying platform 10 and the conical discharge hopper 13 can be adjusted by raising and lowering the classifying platform 10 to prevent unclassified particles from falling into the conical discharge hopper 13 and causing errors.

[0034] The micro powder collection chamber 35 of the two-stage vortex air classifier is connected to the main chamber 23 by a three-section clamp. A vortex stabilizer 33, which can be raised and lowered by the adjustable ring b34, is added in the middle. It provides a smooth surface to the tail of the vortex below the discharge port. This smooth surface helps to stabilize the vortex at the center and prevents the high-speed airflow output by the cleaning nozzle b32 from blowing the powder collected in the micro powder collection chamber back into the main chamber during the cleaning process.

[0035] Example 5 This invention relates to a continuously self-cleaning, micro / nano-level multi-segment vortex air classification method, such as... Figure 9 As shown, the material is fed at a uniform speed by a vibrating feeder, and the original powder is classified into micron powder by a primary classifier. Then, the micron powder is classified into submicron powder by a secondary classifier and a filter screen. Finally, the ultrafine powder in the submicron powder is collected by an electrostatic dust collector.

[0036] Material is fed into the primary vortex air classifier via a vibrating feed plate through the feeding port 3 on both sides. After entering the classifier, the material falls into the rotating spreading disc 4. The rotating spreading disc 4 is connected to the stepper motor 1 above, which disperses the material powder around the inner wall of the cavity. Compressed gas is ejected at high speed through the vacuum chamber inlet 6 and the second air nozzle 5 of each vacuum chamber inlet, breaking up the agglomerated powder in the material. The broken particles fall downwards. Air entering through the main airflow inlet 7 enters the cavity through the vortex inlet pipe 8 and the replaceable guide wing 9, forming a vortex for classification. The separated coarse powder falls into the coarse powder collection chamber 15 along the conical discharge hopper 13 and can be recycled as raw material. Micro powder is sucked into the secondary vortex air classifier through the negative pressure of the micro powder output pipe. The secondary vortex air classifier... Figure 5-6As shown, the process is an improvement on a commonly used cyclone separator. After initial separation, the powder enters the main chamber 23 through the inlet 19 of the secondary classifier, forming a swirling motion. Larger particles, subjected to greater centrifugal force, settle down along the inner wall and are finally collected in the conical discharge hopper into the micro powder collection chamber 35. Smaller particles, subjected to less centrifugal force, are filtered by the negative pressure of the secondary micro powder output pipe 21 and then sucked away by the PTFE membrane filter cylinder 31 in the central area. The particles are then separated again by the vortex formed by the secondary vortex air classifier and the replaceable PTFE membrane filter cylinder 31. The separated micro powder is discharged from the micro powder collection chamber 35. The secondary micro powder is drawn into the electrostatic precipitator 42 through the negative pressure of the secondary micro powder output pipe 21. The particles are ionized by the corona wire 44 in the electrostatic precipitator, generating charged ions. The charged dust particles then settle on the electrode plate 45. The vibrating mechanism 47 then vibrates the electrode plate, causing the fine powder to fall into the fine powder collection chamber 49. Finally, the fine powder product is discharged from the fine powder collection chamber 49.

[0037] Example 6 In one embodiment of the present invention, the material to be graded is nickel powder, with a particle size distribution as shown in the table below.

[0038]

[0039] Fine powder products obtained after classification using a continuously self-cleaning micro-nano level multi-segment vortex air classification system, such as... Figure 8 As shown, the content of -100nm particle size powder reached 41.27%, the content of -300nm particle size powder reached 89.08%, and the content of -500nm particle size powder reached 100%. The D of the fine powder product... 50 It is 133nm, D max The particle size is 491nm, and the fine powder yield is 22%.

[0040] When the two-stage vortex air classifier is not equipped with a PTFE membrane filter, and the classification system classifies nickel powder materials of the same particle size composition under the same operating parameters, the fine powder product obtained after classification will have a higher D content. 50 It is 277nm, D max The particle size is 778nm, and the fine powder yield is 28%. When using a multi-stage vortex air classifier system without a self-cleaning system and a backup second vortex air classifier to classify nickel powder materials of the same particle size composition, under the same operating parameters and the same running time, the D of the fine powder product is... 50 It is 144nm, D max The particle size is 526nm, and the fine powder yield is 5.1%.

Claims

1. A continuously self-cleaning, micro / nano-level multi-segment vortex air classification system, characterized in that, The system includes a primary vortex air classifier, on which two secondary vortex air classifiers are connected in series to achieve two-stage classification, with one of the secondary vortex air classifiers serving as a backup. The secondary vortex air classifiers are equipped with PTFE membrane filter cylinders (31) and a cleaning system. The secondary vortex air classifiers are connected to an electrostatic dust collector (42) to collect the classified fine powder. The electrostatic dust collector (42) is connected to the two secondary vortex air classifiers respectively through a three-way pipe (40). A pneumatic reversing valve (16) is installed on the pipeline connecting the first-stage vortex air classifier to the two second-stage vortex air classifiers to switch the air path. The upper cover of the primary vortex air classifier is provided with a feeding port (3), and a vacuum chamber is connected to the lower part of the upper cover. High-speed compressed gas is introduced into the vacuum chamber through the vacuum chamber air inlet (6). The inner wall of the vacuum chamber is provided with three layers at intervals, and multiple second air nozzles (5) are distributed on each layer, and the second air nozzles (5) of adjacent layers are staggered. A rotating material spreading plate (4) is provided in the vacuum chamber. The rotating material spreading plate (4) is driven to rotate by the primary classifier stepper motor (1) and bearing (2). A vortex air inlet pipe (8) is provided below the vacuum chamber. The airflow of the vortex air inlet pipe (8) flows into the main air inlet. The inlet (7) enters the interior of the first-stage vortex air classifier. A replaceable guide vane (9) is provided inside the vortex inlet pipe (8). A classification platform (10) is provided directly below the vortex inlet pipe (8). The classification platform (10) is connected to the micro powder output pipe (12) through the adjustment ring a (11). The micro powder output pipe (12) extends out of the conical discharge hopper (13) and is connected to the inlet (19) of the second-stage classifier. A coarse powder collection chamber (15) is connected below the conical discharge hopper (13). The pneumatic reversing valve (16) is located on the outside of the conical discharge hopper (13) of the micro powder output pipe (12). The hierarchical platform (10) has a hollow center and smooth protrusions around the perimeter; The secondary vortex air classifier includes a main chamber (23), with a secondary classifier inlet (19) at the top of the main chamber (23). A PTFE-coated filter cylinder (31) is installed inside the main chamber (23), with its upper part connected to a secondary powder output pipe (21). The secondary powder output pipe (21) is connected to a three-way pipe (40) of an electrostatic precipitator housing (42). A longitudinal filter cleaning nozzle (29) is installed in the middle of the PTFE-coated filter cylinder (31). The lower end of the cleaning nozzle (29) is connected to the cleaning system air supply pipe (36). The cleaning system air supply pipe (36) is provided with cleaning nozzle a (30) and cleaning nozzle b (32) on the vertical section inside the main cavity (23). The cleaning system air supply pipe (36) extends outward from the main cavity and is connected to the air compressor. The cleaning pipe normally closed butterfly valve (37) is provided on the outer extension section of the cleaning system air supply pipe (36). The main cavity (23) is connected to the micro powder collection chamber (35) below through the pitch ring b (34) and the vortex stabilizer (33).

2. The continuously graded, self-cleaning micro / nano-level multi-segment vortex air classification system according to claim 1, characterized in that, The cleaning system includes a filter brush (28) and a cavity brush (27). Both the filter brush (28) and the cavity brush (27) are connected to the cylinder piston (24) via a brush holder (25). The cylinder (20) connected to the cylinder piston (24) is located on the upper part of the main cavity (23). The cavity brush (27) is set close to the inner wall of the main cavity (23), and the filter brush (28) is set close to the PTFE membrane filter cylinder (31). There are two sets of the cleaning system. They are symmetrically arranged on both sides of the PTFE membrane filter cylinder (31).

3. The continuously graded, self-cleaning micro / nano-level multi-segment vortex air classification system according to claim 1, characterized in that, The electrostatic precipitator box (42) is provided with an electrostatic precipitator inlet (41) and an electrostatic precipitator outlet (46). The electrostatic precipitator box (42) is provided with multiple layers of electrode plates (45). Corona wires (44) are provided between adjacent electrode plates (45). The electrode plates (45) are fixedly connected to the upper part of the electrostatic precipitator box (42) by tension springs (43). A rapping mechanism (47) is connected to one side of the lower end of the electrode plate (45). The rapping mechanism (47) includes a stepper motor (48) of the rapping mechanism and a crank connecting rod connected to the motor shaft. The end of the crank connecting rod contacts the electrode plate (45). The bottom of the electrostatic precipitator box (42) is hollowed out and connected to the fine powder collection chamber.

4. The continuously graded, self-cleaning micro / nano-level multi-segment vortex air grading system according to claim 1, characterized in that, The replaceable guide wing (9) includes an annular base, with multiple diffuser wings evenly distributed along the circumference of the annular base. The diffuser wings extend in a curved shape from the inner circumference to the outer circumference. An air gap is provided between adjacent diffuser wings, and the annular base and the diffuser wings are integrated.

5. A micro-nano-level multi-segment vortex air classification method with continuous, self-cleaning capabilities, characterized in that... The micro / nano-level multi-segment vortex air classification system described in any one of claims 1-4 is used. The original powder is uniformly fed into a primary vortex air classifier via a vibrating feeder to classify it into micron-sized powder. Then, the micron-sized powder is further classified into submicron-sized powder by a secondary vortex air classifier and filtered through a PTFE-coated filter. Finally, the ultrafine powder in the submicron-sized powder is collected by an electrostatic precipitator. The specific operation steps are as follows: Material is fed into the feeding port of the vortex air classifier via a vibrating feeding plate. After entering the classifier, the material falls into a rotating spreading disc, which disperses the material powder around the inner wall of the chamber. Compressed gas is ejected at high speed through the vacuum chamber inlet and the second air nozzle, breaking up any agglomerated powder particles. The broken particles fall downwards. Air entering through the main airflow inlet enters the chamber through the vortex inlet pipe and is classified by the vortex formed by the replaceable guide vanes. The separated coarse powder falls into the coarse powder collection chamber along the conical discharge hopper. The fine powder is drawn into the secondary stage due to the negative pressure of the fine powder output pipe. The main chamber of the vortex air classifier forms a swirling motion. Large particles of micro powder settle down to the conical discharge hopper and are finally collected in the micro powder collection chamber. Small particles of sub-micro powder are filtered through the PTFE membrane filter in the central area and then drawn away by negative pressure through the sub-micro powder output pipe into the electrostatic precipitator. The separated micro powder is discharged from the micro powder collection chamber. The particles are ionized by the corona wire in the electrostatic precipitator to generate charged ions, which cause the sub-micro powder to become charged and settle on the electrode plate. The vibrating mechanism then vibrates the electrode plate to make the fine powder fall into the fine powder collection chamber. Finally, the fine powder product is discharged from the fine powder collection chamber.

Images