High-speed turbulence dispersed micro powder grading equipment and grading method based on forced vortex centrifugal force field

Abstract

The invention provides a high-speed turbulence dispersed micro-powder grading device and method based on a forced vortex centrifugal force field, the high-speed turbulence dispersed micro-powder grading device comprises an airflow grading machine, the airflow grading machine comprises a group of disc-shaped upper rotor and lower rotor, the upper rotor and the lower rotor are overlapped and buckled, and a blade cage is clamped and cushioned between the upper rotor and the lower rotor; the whole blade cage is cylindrical, the blade cage is composed of a plurality of blades along the radial cylinder, gaps of the blades are channels connecting the inside and the outside of the cylinder, the outer sides of the disc edges of the upper rotor and the lower rotor directly face an annular stator, the disc edges of the upper rotor and the lower rotor and the space between the blades and the annular stator enclose a classification area of the airflow classifier, and the profile of the section of the classification area is in a lying trapezoid shape. The top edge of the trapezoid is formed on the inner side end contour of the stator, the bottom edge is formed on the outer side end contour of the blade, and two waists are respectively formed on the disc edge contours of the upper and lower rotors; gaps for guiding high-speed airflow to pass through to form a high-turbulence dispersion area are formed between the upper and lower rotors and the annular stator; and the upper part of the inner cavity of the blade cage is provided with a fine powder outlet leading to the outside of the airflow classifier.

Description

Technical Field

[0001] The present invention belongs to the technical field of powder material classification, and specifically relates to a high-speed turbulent dispersion micropowder classification equipment and classification method based on a forced eddy current centrifugal force field. The equipment is suitable for the precise classification of ultrafine particles of 0.5-50 microns and can be applied to various scenarios from research and development to large-scale production, and is particularly suitable for diversified materials such as low-melting-point polymers, hard ceramics, abrasives, and chemicals. Background Art

[0002] Traditional centrifugal classifiers rely solely on a single centrifugal force field, which is insufficient for dispersing agglomerated particles, resulting in cut particle size drift (more than ±20%) and a sharpness index >2.5. Classifiers using static guide vanes are unable to dynamically adjust the flow field, so the processing volume is inversely proportional to the classification accuracy. When the processing volume is >5kg / h, the fine powder recovery rate drops by 30%. High-speed airflow directly impacts particles, which easily forms a vortex dead zone at the root of the rotor blades, causing local overheating (>120°C) and blade abrasion, making the maintenance cycle less than 100h. In addition, the feed nozzles of traditional centrifugal classifiers are mostly straight tube structures, which easily lead to insufficient particle acceleration and large particles easily penetrate the blade cage (>15μm particle escape rate ≥8%).

[0003] In general, the prior art has the following shortcomings and deficiencies:

[0004] 1. Insufficient dispersion: Traditional mechanical dispersion is prone to damage particles and has poor effect on breaking up agglomerates of ultrafine powders (<1μm);

[0005] 2. Low classification accuracy: Imprecise flow field control causes coarse particles to mix with fine powder (D75 / D25>2.0);

[0006] 3. Applicability limitations: It is difficult to achieve stable grading of both low melting point materials and high hardness materials;

[0007] 4. High energy consumption: Turbulent resistance at high speed causes system pressure loss > 5kPa.

[0008] 5. Complex structure and difficult maintenance: Traditional equipment mostly adopts multi-stage diversion structure and complex transmission system, with many parts, cumbersome disassembly and assembly, and high maintenance cost;

[0009] 6. Weak recycling processing capacity: The tiny particles entrained in the coarse particles cannot be effectively recovered and reclassified, resulting in a low recovery rate of fine powder. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a high-speed turbulent dispersion micropowder classification equipment based on a forced eddy current centrifugal field with higher classification accuracy, wider particle size range and higher classification efficiency.

[0011] The technical problem to be solved can be implemented by the following technical scheme.

[0012] A high-speed turbulent dispersion type micro-powder grading device based on forced vortex centrifugal force field, comprising an airflow classifier (100), characterized in that,

[0013] The airflow classifier comprises a set of upper rotors (106) and lower rotors (107) in the form of discs, the upper rotors (106) and the lower rotors (107) are stacked together, and a blade cage (117) is clamped between the two; the blade cage (117) is in the form of a cylindrical structure as a whole, and along the radial direction, the cylinder body is composed of a plurality of blades (108) arranged at intervals, the gap between the blades is a passage (118) connecting the outside of the cylinder body and the inner cavity, the discs of the upper rotors (106) and the lower rotors (107) are opposite to an annular stator (109) on the outside, and the space between the disc edges of the upper rotors (106) and the lower rotors (107) and the blade (108) and the annular stator (109) forms a classification zone (116) of the airflow classifier, the cross-sectional profile of the classification zone is in the form of a lying trapezoid, the top edge of the trapezoid is formed at the inner side end profile of the stator (109), the bottom edge is formed at the outer side end profile of the blade (108), and the two waists are formed at the disc edge profiles of the upper rotors (106) and the lower rotors (107), respectively.

[0014] The upper rotors (106), the lower rotors (107) and the annular stator (109) are provided with gaps for guiding high-speed airflow to form a high-turbulent dispersion zone; the inner cavity of the blade cage (117) is provided with a fine powder discharge port (105) which is connected to the inner cavity and leads to the outside of the airflow classifier.

[0015] Further, the inner cavity of the blade cage (117) is connected to the fine powder discharge port (105) through a flow channel (123) of an inner rotor (111); the inner rotor (111) is a cylindrical body, the lower part of the inner rotor is embedded in a positioning groove formed in the disc surface of the lower rotor (107), and the upper part of the inner rotor is limited by the upper rotor (106), a plurality of through holes forming the flow channel (123) are formed in the cylinder wall of the inner rotor, the inner cavity of the cylindrical body of the inner rotor is opposite to the fine powder discharge port and is connected to the inner cavity of the blade cage (117) through the flow channel (123); the flow channel (123) is the only passage connecting the inner cavity of the blade cage and the fine powder discharge port.

[0016] Further, the through holes forming the flow channel (123) are inclined holes, and the included angle between the hole center line and the center line of the inner rotor is 70-85°.

[0017] Furthermore, in the grading area (116) outside the blade (108), the disc angle a between the upper rotor (106) and the lower rotor (107) is controlled within a range of 15-40°; and in the cavity portion inside the blade 108, between the blade and the inner rotor, the disc angle b between the upper rotor (106) and the lower rotor (107) is controlled within a range of 5-20°.

[0018] Furthermore, the upper rotor (106), the blade cage (117) and the lower rotor (107) which are fastened together as one body are positioned on a rotating shaft (121) of a high-speed motor.

[0019] Furthermore, the invention also includes a feed port (102), which is connected to the annular cavity formed by the classification zone (116) through a feed channel (124), and the annular cavity is also connected to a coarse powder outlet (103) for discharging the classified coarse powder; and also includes a circulation port (104) connected to the annular cavity, and the circulation port (104) is used to input the coarse powder for secondary classification.

[0020] Furthermore, the invention also includes a gas inlet (101), and the gas entering the classification zone (116) through the gas inlet (101) carries the classified fine powder particles from the classification zone through the channel (118) between the blades into the inner cavity of the blade cage (117), then passes through the flow channel (123) from the inner cavity of the blade cage into the inner cavity of the inner rotor, and then passes through the inner cavity of the inner rotor and leaves the gas classifier (100) through the fine powder discharge port (105); the gas leaving the gas classifier with fine powder particles then enters the first-stage cyclone separation (1) to complete the collection of intermediate particles, then enters the second-stage cyclone separation (2) to complete the collection of fine powder, and then the gas enters the dust filter (3) to complete the dust filtration, until the gas is discharged from the fan discharge port.

[0021] Preferably, the blade cage is a wear-resistant ceramic part or a polytetrafluoroethylene part.

[0022] Another technical problem to be solved by the present invention is to provide a fine powder classification method using the aforementioned classification device, the method comprising the following steps:

[0023] (1) After the material is sucked into the gas classifier, it is subjected to the centrifugal force and the air flow drag force difference in the rotor ring expansion section, achieving non-contact circumferential dispersion;

[0024] (2) High-speed airflow passes through the gap between the stator and rotor to form a strong shear turbulence field, which completely breaks up the 0.5 μm-level agglomerates;

[0025] (3) After dispersion, the particles enter the classification zone, where they are balanced by the centrifugal force of the forced vortex generated by the rotor and the drag force of the centripetal airflow;

[0026] (4) Coarse particles larger than the target particle size are thrown toward the stator wall and discharged through the coarse powder outlet; fine particles smaller than the target particle size are dragged through the channel of the blade cage and enter the inner cavity of the blade cage, and are finally discharged from the top fine powder outlet.

[0027] Furthermore, the feed rate of the material is controlled to be less than or equal to 10% of the total air volume; the air flow velocity at the gap between the rotor and the stator is 60-110 m / s to ensure the stable formation of a high turbulence dispersion zone; the speed of the servo motor driving the rotor is adjustable within the range of 500-15000 rpm to generate a controllable centrifugal force field.

[0028] The high-speed turbulent dispersion type micro-powder classification equipment and classification method based on the forced eddy current centrifugal force field using the above technical solution have the following characteristics and beneficial effects:

[0029] 1. Breakthrough in classification accuracy: sharpness index 1.0-1.5 (D75 / D25), overlap rate reduced by 40%; fine powder and coarse powder have less overlap in particle size, and accuracy is better than existing equipment (sharpness index>2.0);

[0030] 2. Wide particle size coverage: through the rotor speed (500-15000rpm) and air flow speed (0.1-4m 3 / min) to achieve a wide range of grading from 0.5 to 50 microns, covering ultrafine powders and coarse powders that existing equipment cannot handle; and supports nano-level subdivision;

[0031] 3. Zero-damage dispersion: No mechanical load design, the integrity rate of melting-point sensitive materials (such as PE) is greater than 99%; the blade cage is made of wear-resistant ceramic (suitable for hard materials) or polytetrafluoroethylene (suitable for low-melting-point materials), the high turbulence dispersion area prevents the melting of low-melting-point materials, and the wear-resistant material reduces the wear of hard materials on the equipment;

[0032] 4. Low energy consumption and high recovery rate: By optimizing the stator-rotor gap (air flow velocity of 20-110m / s), the pressure loss is reduced, and the energy consumption is reduced by 20% compared with traditional equipment; the circulation channel design increases the fine powder recovery rate to more than 95%;

[0033] 5. Strong universality: The verification materials cover 12 types of powders including alumina, carbon powder, flour, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the structure of the micro powder classification equipment of the present invention;

[0035] Figure 2 for Figure 1 Another perspective of the structure diagram;

[0036] Figure 3 for Figure 1 Side view of;

[0037] Figure 4 for Figure 1 Side view from another perspective;

[0038] Figure 5 This is a process flow chart of the micro powder classification equipment of the present invention;

[0039] Figure 6 Schematic diagram of the structure of the air flow classifier of the present invention;

[0040] Figure 7 for Figure 6 sectional view of

[0041] Figure 8 for Figure 6 Side view of;

[0042] Figure 9 for Figure 8 Middle AA plane section view;

[0043] Figure 10 Schematic diagram of air flow and powder flow in the air classifier of the present invention;

[0044] Figure 11 Schematic diagram of the structure of the classifying wheel of the air classifier of the present invention;

[0045] Figure 12 Schematic diagram of the exploded structure of the classifying wheel of the air classifier of the present invention;

[0046] Figure 13 Schematic diagram of the cross-sectional structure of the inner rotor of the air classifier of the present invention;

[0047] Figure 14 This is a schematic diagram of the three-dimensional structure of the inner rotor of the air flow classifier of the present invention;

[0048] In the picture:

[0049] 1. First-stage cyclone separation; 2. Second-stage cyclone separation; 3. Dust filter; 4. Micro-powder collection bottle; 5. Intermediate particle collection bottle; 6. Micro-feeder; 7. Pressure gauge; 8. Touch screen; 9. Control cabinet; 10. Coarse powder circulation pipeline; 11. Coarse powder collection bottle; 12. Pressure relief valve; 13. Regulating valve; 14. Fan; 15. Venturi tube; 16. Fan filter element; 17. Gas inlet; 18. Fan exhaust; 19. Heat dissipation window; 20. Gas pressure reducing valve; 21. Power plug.

[0050] 100. (Micropowder) air flow classifier; 101. Gas inlet; 102. Feed port; 103. Coarse powder outlet; 104. Circulation port; 105. Fine powder outlet; 106. Upper rotor; 107. Lower rotor; 108. Blades; 109. Stator; 110. Upper cover; 111. Inner rotor; 112. Shaft seal; 113. Shaft seal cover; 114. Housing; 115. High-speed motor; 116. Classifying area; 117. Blade cage; 118. Channel; 119. Positioning screw; 120. Locking screw; 121. Rotating shaft; 122. Fastening screw; 123. Flow channel; 124. Feed channel. DETAILED DESCRIPTION

[0051] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0052] The present invention provides a high-precision micro-powder classification device and classification method based on forced eddy-turbulence coordinated control, which aims to solve the technical problems of existing micro-powder classification devices, such as narrow classification range, low precision, poor material adaptability, complex structure, high energy consumption, and weak circulation processing capacity. Specifically, the device includes:

[0053] 1. Achieve precise grading in a wide range of 0.5-50 microns;

[0054] 2. Improve grading accuracy and control the sharpness index (D75 / D25) at 1.3-1.8;

[0055] 3. Adapt to the stable classification of various materials such as low melting point, hard, brittle, etc. to avoid agglomeration, melting or equipment wear;

[0056] 4. Simplify the structure and reduce the difficulty of maintenance;

[0057] 5. Optimize flow field design, reduce energy consumption, and improve fine powder recovery rate;

[0058] 6. Achieve continuous and stable operation, taking into account both research and development and large-scale production needs;

[0059] 7. Eliminate the interference of particle agglomeration on classification accuracy;

[0060] 8. Compatible with non-destructive grading of heat-sensitive / hard materials.

[0061] Reference Figures 1 to 14 The grading equipment of the present invention is integrated into a movable equipment cabinet. The material is delivered to the feed port 102 of the conical hopper of the air classifier 100 through the micro feeder 6, and is delivered to the grading area 116 through the feed channel for grading.

[0062] Specifically, material enters the equipment through feed port 102. Gas from gas inlet 101 and the high-speed centrifugal force of the rotors cause the material to be classified near the upper and lower rotors (upper rotor 106 and lower rotor 107) and blades 108. Coarse powder is discharged through coarse powder outlet 103 and collected in coarse powder collection bottle 11. Since some fine powder may be carried along with it during discharge, the discharged material is, if necessary, returned to the equipment along the coarse powder circulation line 10 and through the circulation port 104 along the corresponding channel for classification. Fine powder exits through the fine powder outlet 105 at the top. This design employs a dual material outlet: a lateral coarse powder outlet (including a circulation loop) and a top fine powder outlet (connected to a cyclone separator).

[0063] The fine powder discharge port 105 is connected to the primary cyclone 1 via a pipeline. The fine powder transported to the primary cyclone along with the gas has its intermediate particles intercepted in the primary cyclone and collected in the intermediate particle collection bottle 5 at the lower end. The primary cyclone is connected to the secondary cyclone 2 via a pipeline. The fine powder (micro powder) transported from the primary cyclone to the secondary cyclone along with the gas is intercepted in the secondary cyclone and collected in the fine powder collection bottle 4 at the lower end. The secondary cyclone is connected to the dust filter 3 via a pipeline. The gas carrying dust from the secondary cyclone is transported to the dust filter, where the dust is intercepted by the dust filter. The gas then passes through the pressure relief valve 12 and the fan filter element 16 to the fan 14 and is discharged from the fan exhaust port 18. This realizes an airflow path for gas (air) to enter the airflow classifier 100 from the fan exhaust port 101 and be discharged from the fan outlet 18 after completing material classification and transport.

[0064] A control cabinet 9 is provided at one end of the equipment cabinet. The control cabinet 9 can control the entire system through a PLC. A touch screen 8 is provided on the control cabinet 9, which is used to control the equipment and send instructions and other related operations. A pressure gauge 7 for real-time monitoring of the system pressure is also provided on the top of the control cabinet 9. The gas inlet 17 provided at the position of the fan 14 assists the gas entering at the gas inlet 101 and the high-speed centrifugal force of the rotor to generate a forced swirl. The fan 14 can provide a negative pressure environment for the entire system, enabling the micropowder to be successfully collected from the equipment. A heat dissipation window 19 is also provided on the equipment cabinet, and the hot air in the cabinet is discharged from the heat dissipation window through the equipped heat dissipation fan. The figure also shows the fan filter element 16, gas pressure reducing valve 20, power plug 21, regulating valve 13, pressure relief valve 12 and Venturi tube 15, among which the Venturi tube is used to increase the gas flow rate that provides vortex; the fan filter element is used to prevent dust from entering the fan; the gas pressure reducing valve is used to adjust the pressure of the compressed air pumped into the circulation pipeline; the power plug provides power to the entire system, and the regulating valve is used to adjust the gas flow that provides vortex; the pressure relief valve is used to prevent the pressure in the equipment from being too high and protect the entire system. When the pressure exceeds the rated value, the pressure relief valve will release the pressure.

[0065] The (micro-powder) gas classifier 100 of the present application has the following unique structure compared with the existing gas classifier:

[0066] The upper rotor 106 and the lower rotor 107 are in the shape of a disc, and are inverted together, both of which have a disc edge, the inner surface of which is a bevel with a broken profile line, and a cylindrical blade cage 117 is clamped between the upper rotor 106 and the lower rotor 107, the upper and lower ends of the blade cage 117 are connected with the disc bottom of the disc-shaped structure of the upper rotor 106 and the lower rotor 107 respectively, and for the need of stable positioning, corresponding grooves can be provided on the disc bottom for limiting and positioning the blade cage. In the radial direction, the cylindrical blade cage 117 is composed of a plurality of blades 108 and the space (i.e. the channel 118) between the blades, and the outer side of the disc edge is an annular stator 109. The stator 109, the disc edge of the upper rotor 106, the disc edge of the lower rotor 107 and the blades 108 form an annular space, which is used as a classification zone 116 for classifying materials; the end face of the classification zone is in the shape of a recumbent trapezoid, the top edge of the trapezoid is the inner side end of the stator 109, the bottom edge is the outer side end of the blades 108, and the two waists (waist lines) are the disc edge of the upper rotor 106 and the disc edge of the lower rotor 107. The space of the classification zone 116 is connected with the inner cylinder part of the cylindrical body of the blade cage 117 through the channels 118 between the blades 108 of the blade cage 117, and the upper part of the inner cylinder is connected with the fine powder outlet 105. The classification zone 116 is connected with the coarse powder outlet 103, the feeding channel 124 and the circulating port 104 through pipelines respectively.

[0067] Referring to Figure 7 and Figure 9The upper rotor 106, blade cage 117, and lower rotor 107 are connected and fixed together via fastening screws 122. The lower rotor 107 is connected and fixed to the rotating shaft 121 of the high-speed motor 115 at the center of the disk via locking screws 120. The upper rotor 106, blade cage 117, and lower rotor 107 as a whole can be considered a classifying wheel. The outer portion of the classifying wheel is provided with a housing 114. A shaft seal 112 is provided radially between the housing 114 and the rotating shaft 121. The shaft seal 112 is mainly used to seal the high-speed motor shaft and the equipment cavity. The lower portion of the shaft seal 112 is placed on a stepped table provided by the housing 114, and the upper portion is limited by the shaft seal cover 113. The shaft seal cover 113 is fastened to the housing 114 via positioning screws 119. The outer edge of the classifying wheel placed in the housing 114 faces the annular stator 109 fixed to the housing 114. The upper portion of the housing 114 is enclosed by an upper cover 110, which is provided with a fine powder discharge port 105. The fine powder discharge port 105 communicates with the inner cavity of the blade cage 117. An inner rotor 111 is positioned at this connection point. The inner rotor 111 has a cylindrical structure, with its lower portion embedded in a positioning slot defined in the disk of the lower rotor 107 and its upper portion restrained by the stepped hole surface of the upper rotor 106. Several flow channels 123 are defined in the inner wall of the inner rotor. The upper portion of the cylindrical inner cavity faces and communicates with the fine powder discharge port, and the cylindrical inner cavity communicates with the inner cavity of the blade cage 117 through the flow channels 123.

[0068] See also Figure 10 The gas entering the classification zone 116 through the gas inlet 101 carries the fine powder particles from the classification zone 116 through the channel 118 between the blades into the inner cavity of the blade cage 117, then passes through the flow channel 123 from the inner cavity of the blade cage into the inner cavity of the inner rotor, and then leaves the gas classifier 100 through the inner cavity of the inner rotor and the fine powder discharge port 105. Figures 1 to 5 The gas carrying fine powder particles leaving the gas classifier then enters the first-level cyclone separation 1, the second-level cyclone separation 2 and the dust filter 3 for subsequent operations.

[0069] The coarse powder particles classified in the classification zone 116 leave the gas classifier 100 from the classification zone 116 through the coarse powder outlet 103 and, if necessary, re-enter the classification zone 116 through the circulation port 104 for secondary classification.

[0070] In an embodiment of the present invention, the upper and lower rotors are designed with a disc plate with a diameter of 500mm, and the blade cage contains 24 blades. The material of the blades is wear-resistant ceramic when processing hard materials, and polytetrafluoroethylene when processing low-melting-point materials. The blade height is 80mm. The stator (stator ring) of the annular structure has an inner diameter of 501-504mm, and the gap between it and the rotor (including the upper and lower rotors and blade cage with double disc plates) is usually controlled to be 0.5-2mm, preferably 1-2mm; a high-speed airflow of 20-110m / s is guided to form a high-turbulence dispersion zone to achieve agglomerate crushing; the rotor speed (adjustable from 500-15000rpm) and the airflow speed (0.1-4m 3 The stator's unique structural design and the 0.5-2mm gap with the classifying wheel accelerate gas flow, creating the necessary conditions for eddy currents and ensuring even distribution of the eddy currents to avoid unstable airflow.

[0071] In the feeding system, the convergent-divergent feeding nozzle (referring to the conical hopper mentioned above) is matched with the micro electromagnetic feeder. The throat cross-sectional area of ​​the convergent-divergent nozzle is less than 10% of the total air duct, and is connected to the micro electromagnetic feeder. The feed volume is controlled to be ≤10% of the total air volume to ensure uniform dispersion of the material.

[0072] In an embodiment of the present invention, the feeding amount of the micro electromagnetic feeder is 50 kg / hr, which can be controlled by PLC; the parameters of the feed nozzle are: convergent section angle 30°, divergent section angle 15°, throat diameter 10 mm; the circulation channel adopts a stainless steel pipe with a diameter of 50 mm, one end of which is connected to the coarse particle outlet (i.e., coarse powder outlet 103), and the other end is connected to the upstream of the feed nozzle (usually circulating feed from the circulation port 104); the connection structure of the coarse particle outlet and the circulation channel realizes secondary classification of tiny particles and improves the recovery rate of fine powder.

[0073] In the embodiment of the present invention, the fan 14 adopts a variable frequency fan with a power of 5kW and an air volume adjustment range of 0.5-2m 3 / min.

[0074] See also Figure 11 In the grading area 116 outside the blades 108, the included angle a between the upper and lower rotors 106, 107 is typically controlled within a range of 15-40°, depending on the rotor size, with a preferred angle of 25° in this embodiment. Inside the blades 108, in the cavity between the blades and the inner rotor, the included angle b between the upper and lower rotors 106, 107 is typically controlled within a range of 5-20°, depending on the rotor size, with a preferred angle of 13° in this embodiment.

[0075] See also Figure 13 and Figure 14In an embodiment of the present invention, the number of openings in the flow channel 123 on the inner rotor wall is generally controlled according to the powder particle size distribution. Fine powder has more openings, while coarse powder has more openings and fewer openings. The number of openings is generally 2-5, and in the embodiment of the present invention, it is 3. In addition, the openings in the flow channel are preferably oblique holes, that is, the angle c between the centerline of the opening and the vertical direction (with the centerline of the inner rotor as the vertical direction) follows the rule that the smaller the powder classification particle size, the smaller the angle. The angle range is generally controlled to be 70-85°, preferably 80°. The aperture is determined according to the size of the equipment, and the aperture range is generally 20-50mm. In the embodiment of the present invention, 20mm is used. The special aperture method of the inner rotor can provide the powder with sufficient time to stay in the vortex area for classification.

[0076] The airflow control of the present invention adopts a variable frequency blower + PID closed-loop control. The airflow velocity V at the slit is adjustable from 60 to 110 m / s, and the stator-rotor gap size is matched to ensure the stable formation of a high-turbulence dispersion zone. The rotor is driven by a servo motor, and the speed can be adjusted within the range of 500-15000 rpm (controlled by a frequency converter), generating a controllable centrifugal force field.

[0077] The classification process of the classification method of the present invention is as follows:

[0078] 1. Turbulent dispersion stage:

[0079] After the material is sucked in through the nozzle, it is subjected to the centrifugal force and the air flow drag force difference in the rotor ring expansion section (referring to the classification area), achieving non-contact circumferential dispersion;

[0080] The high-speed airflow passes through the stator-rotor gap to form a strong shear turbulence field, which completely breaks up the 0.5μm-level agglomerates.

[0081] 2. Centrifugal classification stage:

[0082] After dispersion, the particles enter the classification zone, where they are balanced by the centrifugal force of the forced vortex generated by the rotor and the drag force of the centripetal airflow;

[0083] Coarse particles (> target particle size) are thrown toward the stator wall and discharged through the side outlet;

[0084] Fine particles (less than target particle size) penetrate the blade cage due to drag force and are discharged from the top outlet.

[0085] 3. Loop optimization:

[0086] The coarse powder outlet contains an external circulation channel to re-inject the entrained fine powder into the classification area;

[0087] The fine powder is secondary classified by the cyclone, the dust is collected by the filter element, and the system negative pressure is maintained by the rear-end fan.

[0088] The key parameters for coordinated control are shown in Table 1 below.

[0089] Table 1:

[0090] parameter Adjustment range Graded impact mechanism Rotor speed 500-15000rpm Speed ​​↑ → Centrifugal force ↑ → Cutting particle size ↓ air flow speed <![CDATA[0.1-4m 3 / min]]> Flow rate ↑ → fine powder recovery rate ↑, excess will result in particle size ↑ Feed rate ≤200kg / h Overloading causes fine powder mixing rate>5%

[0091] Table 1 is described as follows:

[0092] 1. Rotor speed: The speed range of the equipment is 500-15000rpm; the higher the speed, the greater the centrifugal force and the smaller the particle size.

[0093] For example, at 10,000 rpm, the D50 classification particle size reaches 3 microns, and at 15,000 rpm, the D50 classification particle size can reach 0.8 microns.

[0094] 2. Air flow speed: The air flow speed adjustment range is 0.1-4m 3 / min; Under the premise of a certain feed flow rate, the higher the flow rate, the greater the fine powder recovery rate, but if the air flow velocity is too high, the D50 classification particle size will become larger, which is not conducive to the recovery of fine powder.

[0095] For example: Under the premise of 5kg / h feed flow rate, the air flow velocity is 0.15m 3 / min, the fine powder recovery rate can reach 65%; if the air flow speed is increased to 0.3m 3 / min, the fine powder recovery rate can reach 85%, but the air flow velocity is greater than 1.2m 3 / min, the particle size of the particles to be collected will become larger, and the recovery rate of fine powder will decrease.

[0096] 3. Feed rate: The feed rate range of this equipment is 0-200kg / h. If the feed rate reaches 250kg / h, the proportion of coarse powder in the fine powder to be collected will exceed 5%, so it is meaningless to classify the fine powder.

[0097] In addition, it should be noted that this application does not distinguish between the upper rotor and the lower rotor. When simply referring to the rotor, it refers to the upper rotor and the lower rotor that operate synchronously.

[0098] To further illustrate the classification method, a specific example is given below.

[0099] Example:

[0100] Parameter settings:

[0101] 1. The rotor speed is set to 8000rpm. Under this speed condition, a high-intensity centrifugal force field can be constructed in the classification chamber, fully meeting the dynamic condition requirements for fine classification of micropowders.

[0102] 2. Adjust the fan air volume to 1.2m 3 / min, combined with the calculation and optimization of the classifier structure parameters, can ensure that the airflow velocity at the stator-rotor gap is stably maintained at 80 m / s, providing sufficient dispersion kinetic energy for the material.

[0103] 3. The feed quantity is controlled at 2 kg / hr, which can ensure continuous and stable supply of the material and effectively avoid the problem of reduced classification efficiency caused by too fast feed rate.

[0104] Operation process:

[0105] 1. Fan starting stage: first start the fan system, accurately adjust the fan speed through the frequency converter, and strictly control the air volume at 1.2 m 3 / min. During this process, the wind speed sensor data needs to be continuously monitored to ensure that the airflow velocity at the stator-rotor gap is stably maintained at 80 m / s to provide initial power support for material dispersion.

[0106] 2. Rotor starting stage: after the fan runs stably, start the classification rotor, and gradually increase the rotor speed to 8000 rpm with the help of servo motor driving. Under this speed condition, the centrifugal force field strength generated by the rotor can reach more than 10000G, providing the core driving force for the subsequent particle classification process.

[0107] 3. Material feeding stage: after the rotor speed is stable, start the micro electromagnetic feeder. This equipment uses pulse vibration feeding method to introduce the material into the classifier. In the dispersion zone, the material particle group is subjected to strong impact of 80 m / s high-speed airflow, and the agglomerates are effectively broken to achieve single dispersion state.

[0108] 4. Classification and separation stage: after the material enters the classification zone, the particles realize size separation under the joint action of centrifugal force and airflow drag.

[0109] 5. Quality detection stage: the fine powder after classification is detected for particle size, and the key particle size parameters are measured by a laser particle size analyzer:

[0110] The coarse particles with particle size greater than 5 microns move along the wall of the classification chamber due to the centrifugal force greater than the airflow drag, and are finally discharged from the coarse particle outlet. The discharged coarse particles are returned to the feed inlet through the circulation channel for secondary classification treatment.

[0111] The fine particles with particle size less than 5 microns are discharged from the fine powder outlet due to the dominant role of airflow drag. Subsequently, the fine powder is sequentially subjected to preliminary separation by a cyclone separator and deep filtration by a filter cartridge dust collector to realize efficient collection of dust.

[0112] D75 = 5.4 microns, indicating that the proportion of particles below this particle size is 75%;

[0113] D25=4.2 microns, i.e. 25% of the particles are below this size;

[0114] The sharpness index is calculated to be 5.4 / 4.2=1.29, which meets the preset high-precision grading standard (sharpness index ≤1.6), fully indicating that the grading effect meets the process requirements.

Claims

1. A high-speed turbulent dispersion type micro powder classification device based on a forced eddy current centrifugal force field, comprising an air flow classifier (100), characterized in that: The airflow classifier comprises a set of upper rotors (106) and lower rotors (107) in the shape of discs, the upper rotors (106) and lower rotors (107) being overlapped and interposed with a blade cage (117) therebetween; the blade cage (117) is in the shape of a cylinder as a whole, and along the radial direction, the cylinder is composed of a plurality of blades (108) arranged at intervals, and the gaps between the blades are channels (118) connecting the outside of the cylinder and the inner cavity; the discs of the upper rotors (106) and lower rotors (107) are arranged along the outer sides. Facing an annular stator (109), the disk edges of the upper rotor (106) and the lower rotor (107) and the space between the blades (108) and the annular stator (109) form a classification area (116) of the airflow classifier. The cross-sectional profile of the classification area is a lying trapezoid. The top edge of the trapezoid is formed at the inner end profile of the stator (109), the bottom edge is formed at the outer end profile of the blades (108), and the two sides are formed at the disk edge profiles of the upper rotor (106) and the disk edge profiles of the lower rotor (107). A gap is provided between the upper rotor (106), the lower rotor (107) and the annular stator (109) for guiding high-speed airflow to form a high-turbulence dispersion zone; and a fine powder discharge port (105) is provided at the upper part of the inner cavity of the blade cage (117) and is connected to the blade cage and leads to the outside of the airflow classifier.

2. The high-speed turbulent dispersion type micro powder classification equipment based on forced eddy current centrifugal force field according to claim 1 is characterized in that: The inner cavity of the blade cage (117) is connected to the fine powder discharge port (105) through a flow channel (123) of an inner rotor (111); the inner rotor (111) is a cylindrical body, the lower part of the inner rotor is embedded in the positioning groove provided on the disk surface of the lower rotor (107), and the upper part is limited by the upper rotor (106); a plurality of through holes forming the flow channel (123) are provided on the cylindrical wall of the inner rotor, and the upper part of the cylindrical inner cavity of the inner rotor faces the fine powder discharge port and is connected thereto, and the cylindrical inner cavity is connected to the inner cavity of the blade cage (117) through the flow channel (123); the flow channel (123) is the only channel connecting the inner cavity of the blade cage and the fine powder discharge port.

3. The high-speed turbulent dispersion type micro powder classification equipment based on forced eddy current centrifugal force field according to claim 2 is characterized in that: The through hole forming the flow channel (123) is an inclined hole, and the angle between the center line of the opening and the center line of the inner rotor is 70-85 degrees.

4. The high-speed turbulent dispersion type micro powder classification equipment based on forced eddy current centrifugal force field according to claim 1 is characterized in that: In the grading area (116) outside the blade (108), the disc angle a between the upper rotor (106) and the lower rotor (107) is controlled within a range of 15-40 degrees; and in the cavity portion inside the blade 108, between the blade and the inner rotor, the disc angle b between the upper rotor (106) and the lower rotor (107) is controlled within a range of 5-20 degrees.

5. The high-speed turbulent dispersion type micro powder classification equipment based on forced eddy current centrifugal force field according to claim 1 is characterized in that: An upper rotor (106), a blade cage (117) and a lower rotor (107) which are fastened together as one body are positioned on a rotating shaft (121) of a high-speed motor.

6. The high-speed turbulent dispersion type micro powder classification equipment based on forced eddy current centrifugal force field according to claim 1, characterized in that: The invention also includes a feed port (102) connected to the annular cavity formed by the classification zone (116) through a feed channel (124), and the annular cavity is also connected to a coarse powder outlet (103) for discharging the classified coarse powder; and a circulation port (104) connected to the annular cavity, and the circulation port (104) is used to input the coarse powder for secondary classification.

7. The high-speed turbulent dispersion type micro powder classification equipment based on forced eddy current centrifugal force field according to claim 2, characterized in that: The invention also includes a gas inlet (101). The gas entering the classification zone (116) through the gas inlet (101) carries the classified fine powder particles from the classification zone through the channel (118) between the blades into the inner cavity of the blade cage (117), then passes through the flow channel (123) from the inner cavity of the blade cage into the inner cavity of the inner rotor, and then passes through the inner cavity of the inner rotor and leaves the gas classifier (100) through the fine powder discharge port (105); the gas leaving the gas classifier carrying the fine powder particles then enters the first-stage cyclone separation (1) to complete the collection of intermediate particles, then enters the second-stage cyclone separation (2) to complete the collection of fine powder, and then enters the dust filter (3) to complete the dust filtration, until the gas is discharged from the fan discharge port.

8. The high-speed turbulent dispersion type micro powder classification equipment based on forced eddy current centrifugal force field according to claim 1, characterized in that: The blade cage is made of wear-resistant ceramic or polytetrafluoroethylene.

9. A method for classifying fine powder using the classifying device according to any one of claims 1 to 8, characterized in that: The steps include: (1) After the material is sucked into the gas classifier, it is subjected to the centrifugal force and the air flow drag force difference in the rotor ring expansion section, achieving non-contact circumferential dispersion; (2) High-speed airflow passes through the gap between the stator and the rotor to form a strong shear turbulence field, which completely breaks up the 0.5 μm-level agglomerates; (3) After dispersion, the particles enter the classification zone, where they are balanced by the centrifugal force of the forced vortex generated by the rotor and the drag force of the centripetal airflow; (4) Coarse particles larger than the target particle size are thrown toward the stator wall and discharged through the coarse powder outlet; Fine particles smaller than the target particle size penetrate the channel of the blade cage due to drag force and enter the inner cavity of the blade cage, and are finally discharged from the fine powder discharge port at the top.

10. The classification method according to claim 9, characterized in that The material feed rate is controlled to be less than or equal to 10% of the total air volume; the air flow velocity at the gap between the rotor and the stator is 60-110 m / s to ensure the stable formation of a high-turbulence dispersion zone; the speed of the servo motor driving the rotor is adjustable within the range of 500-15000 rpm to generate a controllable centrifugal force field.

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