Center blanking type powder concentrator

Abstract

The utility model discloses a center blanking type powder concentrator, which belongs to the technical field of powder grading equipment, and comprises a shell, a powder inlet, a powder outlet and a powder outlet. The rotor is rotationally located in the shell, and a plurality of moving blades are distributed along the circumference of the rotor; one end of the central coal dropping pipe is inserted into the shell and is positioned in a central shaft of the rotor; the powder return cone is connected with the lower part of the shell; the multiple sets of guide vane assemblies are distributed on the periphery of the rotor at intervals along the circumference, one end of each guide vane assembly is connected with the portion, below the powder outlet, of the shell, the other end of each guide vane assembly is connected with the other end of the powder return cone, and partial shielding is formed between every two adjacent sets of guide vane assemblies. The device is used for preventing airflow turbulence of a powder selecting area caused by escape of wind powder flow blown back by passive blades. The problems that in the prior art, air powder flow blown back by a driven blade escapes from a gap between adjacent guide static blades, airflow turbulence is caused, and the sorting efficiency of the powder concentrator is reduced are solved.

Description

Technical Field

[0001] The utility model belongs to the technical field of powder grading equipment, and relates to a large-scale ultra-fine powder separator driven by gears, in particular to a center-feeding type separator. Background Art

[0002] Ultra-fine materials formed after grinding cement materials, non-metallic ores, smelting slag and other materials are usually classified and separated by an ultra-fine powder separator. The large-scale ultra-fine powder separator with a central feed pipe currently adopts a belt drive form. The separator with belt drive requires two large bearings as supports. The bearing housing is heavy and has a complex structure, resulting in a relatively high manufacturing cost.

[0003] There are also some problems in the use and maintenance of the separator with belt drive: First, when replacing bearings or wearing parts, the drive assembly needs to be removed from the separator as a whole, which is inconvenient for operation; second, the belt often slips and needs to be tensioned regularly; third, the inside of the separator is usually under negative pressure, and the rotating gap at the transmission shaft of the separator is connected to the outside. The negative pressure will suck in external pollutants, contaminate the lubricating oil, and accelerate the wear of the transmission bearings; fourth, when the rotor rotates, the air-powder flow blown back by the passive blades escapes from the gap between adjacent guide static blades in the separator, causing the air flow in the separation area to be disordered and reducing the separation efficiency of the separator.

[0004] Therefore, it is necessary to provide a separator that does not adopt the belt drive form. Summary of the Utility Model

[0005] In order to at least solve the problem in the above-mentioned prior art that the air-powder flow blown back by the passive blades escapes from the gap between adjacent guide static blades in the separator, causing the air flow in the separation area to be disordered and reducing the separation efficiency of the separator, the utility model provides the following technical solution: A center-feeding type separator, the separator comprising:

[0006] A housing having a powder outlet;

[0007] A rotor rotatably disposed within the housing, the rotor being circumferentially provided with a plurality of moving blades;

[0008] A central coal-feeding pipe, one end of which is inserted into the housing and is located within the central axis of the rotor;

[0009] A return powder cone connected to the lower part of the housing; and

[0010] The deflector vane assembly, multiple groups of which are circumferentially and spacedly distributed on the periphery of the rotor. One end of the deflector vane assembly is connected to the housing below the powder outlet, and the other end of the deflector vane assembly is connected to the other end of the powder return cone. A partial occlusion is formed between adjacent two groups of the deflector vane assemblies to prevent the air-powder flow blown back by the moving blades from escaping and causing air flow disorder in the powder selection area.

[0011] Optionally, in the above-mentioned central feeding type powder separator, the deflector vane assembly includes: a fixed wind baffle, a stationary vane and a deflector;

[0012] The fixed wind baffle is parallel to the tangent direction of the rotor and is connected to the upper part of the housing;

[0013] The stationary vane is located at one end of the fixed wind baffle, and one end of the stationary vane is connected to the powder return cone;

[0014] The deflector is located at the other end of the fixed wind baffle;

[0015] The stationary vane partially occludes the deflector in the adjacent deflector vane assembly.

[0016] Optionally, in the above-mentioned central feeding type powder separator, the deflector is arranged at an angle with the fixed wind baffle, and the stationary vane is arranged at an angle with the tangent of the rotor.

[0017] Optionally, in the above-mentioned central feeding type powder separator, the angle between the stationary vane and the tangent of the rotor is greater than the angle between the deflector and the fixed wind baffle.

[0018] Optionally, in the above-mentioned central feeding type powder separator, the angle between the stationary vane and the tangent of the rotor is 30° - 40°;

[0019] The angle between the deflector and the fixed wind baffle is 20° - 30°.

[0020] Optionally, in the above-mentioned central feeding type powder separator, the housing includes: an upper housing, a middle housing and a lower housing arranged in sequence;

[0021] The powder outlet is arranged on the side wall of the upper housing;

[0022] One end of the middle housing is connected to the upper housing, the other end of the middle housing is detachably connected to the lower housing, and the cross-section of the ring formed by the middle housing and the deflector vane assembly gradually increases from top to bottom;

[0023] The deflector vane assembly is located inside the middle housing;

[0024] The lower housing is connected to the powder return cone.

[0025] Optionally, in the above-mentioned central feeding type powder separator, the powder separator further includes: the gear drive device, and the gear drive device includes: an internal gear box, an external gear box, and a drive motor;

[0026] The internal gear box is located inside the top of the housing. A slewing bearing and a first gear are arranged inside the internal gear box. The slewing bearing includes: a bearing and a second gear located outside the bearing. The bearing is sleeved on the central shaft, and the first gear meshes with the second gear;

[0027] One end of the central shaft is located inside the internal gear box, and the other end of the central shaft extends to the middle of the housing;

[0028] The external gear box is located outside the top of the housing, and the output shaft of the external gear box is connected to the first gear;

[0029] The drive motor is mounted on the housing through a motor support, and the output shaft of the drive motor is connected to the input shaft of the external gear box.

[0030] Optionally, in the above-mentioned central feeding type powder separator, the powder separator further includes: a sealing device, and the sealing device includes: a sealed air chamber, a first air seal ring, and a second air seal ring;

[0031] The sealed air chamber is located below the internal gear box and outside the central shaft; the sealed air chamber is provided with a sealed air inlet, and the sealed air chamber is communicated with the inner cavity of the internal gear box;

[0032] The first air seal ring is located outside the bottom of the sealed air chamber and is used to air-seal the gap between the sealed air chamber and the central shaft;

[0033] The second air seal ring is located outside the bottom of the central shaft and is used to air-seal the gap between the central shaft and the central coal dropping pipe.

[0034] Optionally, in the above-mentioned central feeding type powder separator, the moving blades are divided into upper and lower layers, and the moving blades at opposite upper and lower positions are connected by a support plate. The moving blades are detachably connected to the rotor, and one end of the moving blade is angled 90° in the rotation direction of the rotor.

[0035] Optionally, in the above-mentioned central feeding type powder separator, the length of the central coal dropping pipe is greater than the length of the central shaft. One end of the central coal dropping pipe extends into the inner cavity of the powder return cone, and the other end of the central coal dropping pipe is covered with a cover plate.

[0036] The beneficial effects brought by the technical solution provided by the embodiment of the present utility model are as follows:

[0037] In the present application, partial occlusion is formed between two adjacent guide vane assemblies, which can prevent the air powder flow blown back by the passive vane from escaping and causing air flow disorder in the powder selection area, thus ensuring the powder selection efficiency of the powder separator. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic structural diagram of a central feeding type powder separator provided by the embodiment of the present utility model;

[0039] Figure 2 is Figure 1 a top view schematic diagram of the specific structure of the shown guide vane;

[0040] Figure 3 is Figure 2 a schematic structural diagram of C shown;

[0041] Figure 4 is Figure 1 a schematic structural diagram of the shown rotor vane;

[0042] Figure 5 It is a schematic structural diagram of a gear drive device in a central feeding type powder separator provided by the embodiment of the present utility model;

[0043] Figure 6 is Figure 1 a schematic structural diagram of A shown;

[0044] Figure 7 is Figure 1 a schematic structural diagram of B shown;

[0045] In the figure: 1. housing; 101. upper housing; 102. middle housing; 103. lower housing; 104. powder outlet; 2. central shaft; 3. rotor; 4. moving vane; 5. return powder cone; 6. central coal feeding pipe; 7. guide vane; 701. fixed wind baffle; 702. static vane; 703. guide plate; 8. support seat; 9. built-in gearbox; 10. external gearbox; 11. driving motor; 12. first air seal ring; 13. second air seal ring; 14. sealing air inlet; 15. coupling; 16. motor base; 17. sealing air chamber. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] In order to make the purpose, technical solution and advantages of the present utility model clearer, the embodiments of the present utility model will be further described in detail below with reference to the accompanying drawings.

[0047] In the description of the present utility model, the orientation or positional relationship indicated by terms such as "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present utility model rather than requiring the present utility model to be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present utility model. The terms "connected", "connected to", and "arranged" used in the present utility model should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection; it can be directly connected or indirectly connected through an intermediate component; it can be a wired electrical connection, a radio connection, or a wireless communication signal connection. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0048] Please refer to Figure 1-7 , the present utility model provides the following technical solutions: a central feeding type powder separator. The powder separator of the present application includes: a housing 1, a rotor 3, a central coal feeding pipe 6, a return powder cone 5, and a guide vane 7 assembly. The housing 1 has a powder outlet 104 for discharging the particles with qualified fineness separated. The rotor 3 rotates inside the housing 1, and the rotor 3 can be driven to rotate by a driving device (such as a motor). The driving device is not limited in this embodiment. A plurality of moving vanes 4 are arranged along the circumference of the rotor 3. One end of the central coal feeding pipe 6 (also called the feeding pipe) is inserted into the housing 1 and extends into the return powder cone 5. At the same time, the central coal feeding pipe 6 is located inside the central axis 2 of the rotor 3, and feeding is realized through the central coal feeding pipe 6. The return powder cone 5 is in a funnel shape, and the return powder cone 5 is connected to the lower part of the housing 1. Materials (such as cement materials, non-metallic ores, smelting slag, etc.) are added into the central coal feeding pipe 6. The materials fall into the return powder cone 5 along the central coal feeding pipe 6 and flow out from one end (also called the feeding port) of the return powder cone 5 and fall into the grinding area on the grinding table. A plurality of groups of guide vane 7 assemblies are distributed at intervals along the circumference outside the rotor 3. One end of the guide vane 7 assembly is connected to the housing 1 below the powder outlet 104, and the other end of the guide vane 7 assembly is connected to the other end of the return powder cone 5. A partial occlusion is formed between two adjacent groups of guide vane 7 assemblies, that is, there is a certain overlap degree between two adjacent guide vane 7 assemblies. When the air-powder flow passes through the gap space between two adjacent groups of guide vane 7 assemblies, such a structure can prevent the air-powder flow blown back by the moving vane 4 from escaping and causing air flow disorder in the powder separation area, thereby ensuring the separation efficiency of the powder separator.

[0049] Refer to Figure 2 As shown, the guide vane 7 assembly includes: a fixed wind baffle 701, a stationary vane 702, and a guide plate 703. Among them, the fixed wind baffle 701 is parallel to the tangent direction of the rotor 3, and the fixed wind baffle 701 is connected to the upper part of the housing 1, such as by bolts. The stationary vane 702 is located at one end of the fixed wind baffle 701 (at Figure 2In the shown screen, taking a set of guide vane 7 assemblies at the lowest position inside the housing 1 as an example, the stationary vane 702 is connected to the left end of the fixed wind deflector 701. For example, the stationary vane 702 can be bolted to the fixed wind deflector 701. One end of the stationary vane 702 is connected to the upper edge of the powder return cone 5, such as by bolt connection, which avoids the air-powder flow outside the powder return cone 5 passing through the upper edge of the powder return cone 5 to form a short circuit. The deflector 703 is welded to the other end of the fixed wind deflector 701 (in Figure 2 In the shown screen, taking a set of guide vane 7 assemblies at the lowest position inside the housing 1 as an example, the deflector 703 is connected to the right end of the fixed wind deflector 701. The stationary vane 702 partially obscures the deflector 703 in the adjacent guide vane 7 assemblies, that is, the projection of the stationary vane 702 on the tangent of the rotor 3 (or on the extension line of the fixed wind deflector 701), in addition to covering the gap between two adjacent sets of guide vane 7 assemblies, also partially overlaps with the projection of the deflector 703 on the fixed wind deflector 701, so as to prevent the air-powder flow blown back by the passive vane 4 from escaping from the gap space between two adjacent sets of guide vane 7 assemblies.

[0050] Furthermore, referring to Figure 3 As shown, the deflector 703 and the fixed wind deflector 701 are arranged at an angle, and the stationary vane 702 and the tangent of the rotor 3 (which can also be imagined as the extension line of the fixed wind deflector 701) are arranged at an angle. It should be noted that the angles here are all acute angles. Specifically, one end of the fixed wind deflector 701 is bent towards the rotor 3 at the center of the housing 1, and the stationary vane 702 is located on the bent edge of the fixed wind deflector 701; or the fixed wind deflector 701 is not bent, and the stationary vane 702 and the fixed wind deflector 701 are arranged at an angle (this angle is an obtuse angle, and the sum of it and the bending angle is 180°). The deflector 703 is welded to the inner side of the other end of the fixed wind deflector 701. Preferably, since a gap space for the air-powder flow to pass through is formed between two adjacent sets of guide vane 7 assemblies, the angle between the stationary vane 702 and the tangent of the rotor 3 is greater than the angle between the deflector 703 and the fixed wind deflector 701, so that the above-mentioned gap space is in a reduced state. According to the Venturi effect and Bernoulli's equation, C = P+(1 / 2)*ρv^2+ρgh, it can be known that when a certain fluid passes through a contraction section, the flow velocity increases, and when the flow velocity increases, its pressure decreases, forming a low pressure, thereby generating an adsorption effect, so as to better promote the air-powder flow to pass through the gap space.

[0051] Preferably, the angle between the stator vane 702 and the tangent of the rotor 3 (or the extension line of the fixed wind deflector 701) is 30° to 40°, for example: 30°, 32°, 34°, 35°, 40°. The angle between the deflector 703 and the fixed wind deflector 701 is 20° to 30°, for example: 20°, 23°, 25°, 37°, 30°. When the angle between the stator vane 702 and the tangent of the rotor 3 (or the extension line of the fixed wind deflector 701) is 34° and the angle between the deflector 703 and the fixed wind deflector 701 is 25°, the shielding effect of the stator vane 702 on the deflector 703 is the best while ensuring the smooth passage of the air-powder flow through the gap space.

[0052] As an embodiment of the specific structure of the above-mentioned housing 1, in this embodiment, the housing 1102 includes: an upper housing 1101, a middle housing 1102, and a lower housing 1103 arranged in sequence. As Figure 1 shown, a powder outlet 104 is provided on the side wall of the upper housing 1101. One end of the middle housing 1102 is connected to the upper housing 1101, and the other end of the middle housing 1102 is detachably connected to the lower housing 1103. The deflector vane 7 assembly is located inside the middle housing 1102. The cross-section of the ring formed by the middle housing 1102 and the deflector vane 7 assembly (referring to the fixed wind deflector 701) gradually increases from top to bottom, so that the air-powder flow can change its running direction and better pass through the gap space. The lower housing 1103 is connected to the powder return cone 5. Preferably, a docking flange is provided at the connection between the middle housing 1102 and the lower housing 1103. Both of the two paired flanges have two groups of precision reamed holes bolts, and the middle housing 1102 and the lower housing 1103 can be connected together through the precision reamed holes bolts. In addition, a plurality of support seats 8 are circumferentially arranged on the side wall of the powder return cone 5 to support the powder return cone 5 and fix it on the housing 1. The air-powder flow from the grinding area enters the classifier through the annular space between the housing 1 and the powder return cone 5.

[0053] In order to drive the rotation of the rotor 3, the classifier of the present application further includes: a gear drive device. Specifically, referring to Figure 5As shown in the figure, the gear drive device includes: an internal gearbox 9, an external gearbox 10, and a drive motor 11. The internal gearbox 9 is located inside the top of the housing 1. A slewing bearing and a first gear are arranged inside the internal gearbox 9. The slewing bearing includes: a bearing and a second gear located outside the bearing. The bearing is sleeved on the central shaft 2, and the first gear meshes with the second gear. One end of the central shaft 2 is located inside the internal gearbox 9, and the other end of the central shaft 2 extends to the middle of the housing 1. The external gearbox 10 is located outside the top of the housing 1. The output shaft of the external gearbox 10 is connected to the first gear to achieve large reduction ratio transmission. The drive motor 11 is installed on the housing 1 through a motor support, and the output shaft of the drive motor 11 is connected to the input shaft of the external gearbox 10 through a coupling 15. When in use, driven by the drive motor 11, the output shaft of the external gearbox 10 drives the first gear inside the internal gearbox 9 to rotate. The first gear drives the second gear to rotate, and at the same time drives the central shaft 2 inside the bearing to rotate. The central shaft 2 drives the rotor 3 and the moving blades 4 to rotate. It should be noted that the drive motor 11 can be selected as a motor with a motor controller or a variable frequency motor. The speed of the rotor 3 is adjusted through the drive motor 11 to achieve the required output speed. In this application, a gear drive device is adopted. When replacing the bearing or vulnerable parts, it is not necessary to remove the drive assembly from the classifier as a whole, which is convenient for operation.

[0054] In order to achieve the sealing of the air and powder inside the classifier, the classifier of this application further includes: a sealing device. The sealing device includes: a sealed air chamber 17, a first air seal ring 12, and a second air seal ring 13. The sealed air chamber 17 is located below the internal gearbox 9 and outside the central shaft 2. The sealed air chamber 17 is provided with a sealed air inlet 14. The sealed air chamber 17 communicates with the inner cavity of the internal gearbox 9. The first air seal ring 12 is located outside the bottom of the sealed air chamber 17. Since the central shaft 2 penetrates the sealed air chamber 17 and one end of the central shaft 2 extends into the internal gearbox 9, there are gaps between the central shaft 2 and the sealed air chamber 17, and between the central shaft 2 and the internal gearbox 9. The first air seal ring 12 is used to air-seal the gap between the sealed air chamber 17 and the central shaft 2. The second air seal ring 13 is located outside the bottom of the central shaft 2 and below the rotor 3 at the same time. Therefore, the second air seal ring 13 is also called the rotor air seal ring. Since the central coal dropping pipe 6 is located inside the central shaft 2, there is a gap between the central shaft 2 and the central coal dropping pipe 6. The second air seal ring 13 is used to air-seal the gap between the central shaft 2 and the central coal dropping pipe 6. When continuous external air enters the sealed air chamber 17 through the sealed air inlet 14, a part of the air enters the gap between the central shaft 2 and the sealed air chamber 17, and then is blocked by the first air seal ring 12 and cannot move forward to form sealed air. Refer to Figure 6As shown, above the first air seal ring 12 (referring to the gap between the central axis 2 and the sealed air chamber 17 and above), it is the sealed air side, and below the first air seal ring 12 is the air-powder side). Another part of the air enters the built-in gearbox 9 through the gap between the sealed air chamber 17 and the central axis 2. Subsequently, the air enters the gap between the central axis 2 and the central coal dropping pipe 6 and is blocked by the second air seal ring 13 and cannot move forward to form sealed air (refer to Figure 7 As shown, the gap between the central axis 2 and the central coal dropping pipe 6 above the second air seal ring 13 is the sealed air side, and below the second air seal ring 13 is the air-powder side). In this way, the air-powder isolation inside the separator is achieved through the first air seal ring 12 and the second air seal ring 13, and at the same time, the inside of the built-in gearbox 9 is prevented from being contaminated.

[0055] To ensure the rigidity of the rotating cage, the moving blades 4 are divided into upper and lower layers, and the number of moving blades 4 in each layer is 48. The moving blades 4 opposite in the upper and lower positions are connected by a support plate. The moving blades 4 are detachably connected to the rotor 3. One end of the moving blade 4 is angled 90° in the rotation direction of the rotor 3 to form an L shape, as Figure 4 As shown, during the rotation of the moving blade 4 with the rotor 3, the materials in the air-powder flow are separated. The higher the rotation speed of the rotor 3, the finer the fineness of the separated materials.

[0056] As a preference for the above-mentioned central coal dropping pipe 6, in this embodiment, the length of the central coal dropping pipe 6 is greater than the length of the central axis 2. One end of the central coal dropping pipe 6 extends into the inner cavity of the return powder cone 5, and the other end of the central coal dropping pipe 6 (referring to the end located outside the housing 1) is covered with a cover plate to prevent the air-powder flow from escaping from the central coal dropping pipe 6.

[0057] The working principle of this equipment is as follows:

[0058] The milled ultrafine powder material is blown up by hot air to form an air-powder flow, which enters the classifier. First, it enters the annular space between the bottom of the housing 1 and the return powder cone 5. The middle part of the housing 1 and the guide vane 7 form a conical space with a gradually decreasing annular cross-sectional area from bottom to top, which increases the pressure of the air-powder flow and enables it to better enter the gap space between adjacent guide vanes 7. The air-powder flow changes its direction of movement. A part of the coarse particles (i.e., particles with unqualified fineness) carried in the air-powder flow hit the stationary vane 702 in the guide vane 7 and fall into the return powder cone 5. The air-powder flow passing through the gap space converges with the air flow formed by the rotation of the moving vane 4. The qualified particles pass through the rotor 3 and enter the powder outlet 104 at the upper part of the housing 1, while the unqualified coarse particles fall into the return powder cone 5 and are returned to the milling area through the return powder cone 5 for re-milling. Partial occlusion is formed between adjacent groups of guide vane 7 assemblies to prevent the air-powder flow passing through the gap space from being blown back by the moving vane 4 and escaping, causing air flow disorder in the classification area. The rotor 3 (and the moving vane 4) is driven to rotate by outputting different speeds through the gear drive device. The faster the rotor 3 rotates, the smaller the particle diameter that can pass through the moving vane 4, thereby realizing the control of the fineness of the material.

[0059] It should be noted that in order to allow the unqualified coarse particles to return to the milling area through the return powder cone 5, the central coal dropping pipe 6 and the inner wall of the return powder cone 5 should not be in contact.

[0060] As is known by common technical knowledge, the present utility model can be implemented by other embodiments without departing from its spiritual essence or essential features. Therefore, the above-disclosed embodiments are illustrative in all aspects and not exclusive. All changes within the scope of the present utility model or equivalent to the present utility model are encompassed by the present utility model.

Claims

1. A center-dropping powder classifier, characterized in that: The powder classifier comprises: A shell having a powder outlet; A rotor, the rotor is rotatably located in the housing, and the rotor is provided with a plurality of moving blades along the circumference; A central coal dropping pipe, one end of which is inserted into the shell, and the central coal dropping pipe is located in the central axis of the rotor; A powder return cone connected to the lower portion of the housing; and A guide vane assembly, wherein a plurality of groups of the guide vane assemblies are distributed at circumferential intervals on the periphery of the rotor, one end of the guide vane assembly is connected to the shell below the powder outlet, and the other end of the guide vane assembly is connected to the other end of the powder return cone, and a partial shielding is formed between two adjacent groups of the guide vane assemblies to prevent the wind and powder flow blown back by the moving blades from escaping and causing air flow turbulence in the powder selection area.

2. The center-dropping powder classifier according to claim 1, characterized in that: The guide vane assembly comprises: a fixed windshield, a stationary vane and a guide plate; The fixed wind shield is parallel to the tangent direction of the rotor, and the fixed wind shield is connected to the upper part of the shell; The stationary blade is located at one end of the fixed windshield plate, and one end of the stationary blade is connected to the powder return cone; The deflector is located at the other end of the fixed wind shield; The stationary blades partially shield the guide plates in the adjacent guide blade assemblies.

3. The center-dropping powder classifier according to claim 2, characterized in that: The guide plate is arranged at an angle with the fixed wind shield plate, and the stationary blade is arranged at an angle with the tangent line of the rotor.

4. The center-dropping powder classifier according to claim 2, characterized in that: The included angle between the stationary blade and the tangent line of the rotor is greater than the included angle between the guide plate and the fixed wind shield plate.

5. The center-dropping powder classifier according to claim 2, characterized in that: The angle between the stationary blade and the tangent line of the rotor is 30° to 40°; The included angle between the guide plate and the fixed wind shield is 20° to 30°.

6. The center-dropping powder classifier according to claim 1, characterized in that: The housing comprises: an upper housing, a middle housing and a lower housing arranged in sequence; The powder outlet is provided on the side wall of the upper shell; One end of the middle shell is connected to the upper shell, and the other end of the middle shell is detachably connected to the lower shell. The cross section of the ring formed by the middle shell and the guide vane assembly gradually increases from top to bottom. The guide vane assembly is located on the inner side of the middle casing; The lower shell is connected to the powder return cone.

7. The center-dropping powder classifier according to claim 1, characterized in that: The powder selecting machine further comprises: the gear driving device, which comprises: an internal gear box, an external gear box and a driving motor; The built-in gear box is located on the inner side of the top of the housing, and a slewing bearing and a first gear are arranged in the built-in gear box. The slewing bearing includes: a bearing and a second gear located outside the bearing, and the bearing is sleeved on the central shaft, and the first gear and the second gear are meshed; One end of the central shaft is located in the built-in gear box, and the other end of the central shaft extends to the middle of the housing; The external gear box is located on the top outer side of the housing, and the output shaft of the external gear box is connected to the first gear; The driving motor is mounted on the housing via a motor support, and the output shaft of the driving motor is connected to the input shaft of the external gear box.

8. The center-dropping powder classifier according to claim 7, characterized in that: The powder classifier further comprises: a sealing device, wherein the sealing device comprises: a sealed air chamber, a first air sealing ring and a second air sealing ring; The sealed air chamber is located below the built-in gear box and outside the central axis; the sealed air chamber is provided with a sealed air inlet, and the sealed air chamber is communicated with the inner cavity of the built-in gear box; The first air-sealing ring is located at the outer side of the bottom of the sealed air chamber and is used to air-seal the gap between the sealed air chamber and the central axis; The second air sealing ring is located at the outer side of the bottom of the central shaft, and is used for air sealing the gap between the central shaft and the central coal dropping pipe.

9. The center-dropping powder classifier according to claim 1, characterized in that: The moving blades are divided into two layers, the upper and lower layers, and the moving blades that are opposite to each other are connected by a support plate. The moving blades are detachably connected to the rotor, and one end of the moving blade is bent at an angle of 90° toward the rotation direction of the rotor.

10. The center-dropping powder classifier according to claim 1, characterized in that: The length of the central coal dropping pipe is greater than the length of the central axis, one end of the central coal dropping pipe extends to the inner cavity of the powder return cone, and the other end of the central coal dropping pipe is covered with a cover plate.

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