Classifying rotor and centrifugal air classifier

Abstract

To provide a classification rotor which is high in abrasion resistance and light in weight, and a centrifugal air flow classifier.SOLUTION: A classification rotor comprises: a lid body made of ceramic which has a through hole in a thickness direction; and a bottomed cylindrical body made of ceramic including a bottom part which has a shaft hole on the same axis as the through hole and a peripheral wall part which is connected with the bottom part and has a plurality of slits. An inferior surface of the lid body and an edge face of the peripheral wall part are joined through a layer of ceramic. A centrifugal air flow classifier uses the classification rotor.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a classifying rotor and a centrifugal air classifier. [Background technology]

[0002] A centrifugal air classifier has a mechanism that rotates the built-in classifying rotor at high speed and flows an air current containing powder from the side of the rapidly rotating classifying rotor to the opening in the center of the upper plate. Coarse powder contained in the air current is thrown out of the classifying rotor by the centrifugal force generated by the rotation of the blades, and fine powder is removed from the opening in the center of the upper plate of the classifying rotor by the air current which overcomes the centrifugal force, thereby classifying the powder contained in the air current into coarse and fine powder.

[0003] For example, Patent Document 1 proposes a classification rotor for use in such a mechanism, which has multiple flat blades, both ends of which are sandwiched between two replaceable slit plates with radial slits, and the upper and lower plates of the classification rotor are supported by supports provided inside. It also describes that the blades are made of a ceramic material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Utility Model Registration No. 3103835 Summary of the Invention [Problem to be solved by the invention]

[0005] The classification rotor proposed in Patent Document 1 has the problem that when classifying hard powders such as ceramic powder, the metal components other than the blade (e.g., upper and lower plates) are prone to wear. In addition, as the proportion of metal components increases, the rotor becomes heavier, resulting in a large load on the motor that rotates it.

[0006] An object of the present disclosure is to provide a classification rotor and a centrifugal air classifier that are highly wear-resistant and lightweight. [Means for solving the problem]

[0007] The classification rotor according to the present disclosure comprises a ceramic lid having a through hole in the thickness direction, and a bottomed cylindrical body made of ceramic having a bottom having an axial hole coaxial with the through hole and a peripheral wall connected to the bottom and having a plurality of slits. The lower surface of the lid and the end surface of the peripheral wall are joined via a ceramic layer.

[0008] The centrifugal air classifier according to the present disclosure uses the above-mentioned classifying rotor. Effect of the Invention

[0009] The classifying rotor and centrifugal air classifier according to the present disclosure are highly wear-resistant and lightweight. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a perspective view of a classifying rotor according to a non-limiting embodiment of the present disclosure. [Diagram 2] 2 is a cross-sectional view of the classifying rotor shown in FIG. 1 taken along an axis. [Diagram 3] 3 is an enlarged view of the periphery of a layer made of ceramics in the classifying rotor shown in FIG. 2. [Figure 4] FIG. 1 is a schematic diagram illustrating a centrifugal air classifier according to a non-limiting embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] <Classification rotor> Hereinafter, a classifying rotor according to a non-limiting embodiment of the present disclosure will be described in detail with reference to the drawings. However, in each of the drawings referred to below, for the sake of convenience, only the main components necessary for explaining the embodiment are shown in a simplified form. Therefore, the classifying rotor may include any component not shown in each of the drawings referred to. Furthermore, the dimensions of the components in each drawing do not faithfully represent the dimensions of the actual components and the dimensional ratios of each component. These points are also true of the centrifugal air classifier described below.

[0012] The classifying rotor 1 includes a cover body 2 and a bottomed cylindrical body 3, as shown in an example in FIGS.

[0013] The lid 2 has a through hole 21 in the thickness direction. The through hole 21 can function as an outlet hole for taking out fine powder classified from the powder to the outside of the classifying rotor 1. The powder can be, for example, a hard powder such as a ceramic powder. The lid 2 may be disk-shaped.

[0014] The bottomed cylindrical body 3 has a bottom 31 and a peripheral wall 32. The bottom 31 has an axial hole 311 on the same axis S as the through hole 21. The axial hole 311 can function as an attachment hole for a motor that rotates the classifying rotor 1. The axial hole 311 may be a hole in a cylinder 312 that protrudes toward the lid 2.

[0015] The axis S may be referred to as a rotation axis. The classifying rotor 1 is rotatable around the axis S. The classifying rotor 1 may have a shape extending along the axis S.

[0016] The peripheral wall portion 32 is connected to the bottom portion 31. The peripheral wall portion 32 may be formed integrally with the bottom portion 31. The peripheral wall portion 32 has a plurality of slits 321. The slits 321 can function as a portion for passing an airflow containing powder inside the classifying rotor 1. The slits 321 can also function as a portion for flicking coarse powder contained in the airflow to the outside of the classifying rotor 1.

[0017] The number of the slits 321 may be equal to or greater than 24 and equal to or less than 120. The multiple slits 321 may be positioned at equal intervals along the outer periphery of the peripheral wall portion 32. The multiple slits 321 may extend along the axis S.

[0018] Here, the lid 2 is made of ceramics. The bottomed cylindrical body 3 is also made of ceramics. The lower surface 22 of the lid 2 and the end surface 322 of the peripheral wall portion 32 are joined via a layer 4 made of ceramics. As a result, since the lid 2, the bottomed cylindrical body 3 and the layer 4 are made of ceramics, the wear resistance of the classifying rotor 1 is increased, and mixing of wear powder generated from the members constituting the classifying rotor 1 into the powder is suppressed. Furthermore, since the entire classifying rotor 1 is lighter, the load on the motor for rotating the classifying rotor 1 is reduced, allowing it to be used for a long period of time.

[0019] The ceramic may be mainly composed of aluminum oxide. The main component may mean the component that is the largest in a total of 100 mass% of all components that constitute the ceramic. The main component may be, for example, 80 mass% or more. When the main component of the ceramic is aluminum oxide, it may contain at least one of silicon, magnesium, and calcium as an oxide.

[0020] The components that make up ceramics can be identified using an X-ray diffractometer (XRD) using CuKα radiation, and then the elemental content can be determined using an X-ray fluorescence analyzer (XRF) or an inductively coupled plasma (ICP) emission spectrometer (ICP) and converted into the content of the identified components.

[0021] The ceramics in the lid 2, the bottomed cylindrical body 3, and the layer 4 may be the same or different. For example, the layer 4 may be made of ceramics having the same main component as the ceramics in the lid 2 and the bottomed cylindrical body 3. In this case, the lower surface 22 of the lid 2 and the end surface 322 of the peripheral wall portion 32 can be firmly joined. The thickness of the layer 4 may be set to, for example, about 40 μm or more and 60 μm or less.

[0022] The layer 4 may have a first protrusion 41 connected to the layer 4 on the inner circumferential side of the bottomed cylindrical body 3. The presence of the first protrusion 41 makes it difficult for powder to be sandwiched between the layer 4 and the lower surface 22 of the lid 2 and between the layer 4 and the end surface 322 of the peripheral wall portion 32, reducing the risk of the sandwiched powder being mixed in as a foreign matter even when different powders are classified in the front and rear. The main component of the first protrusion 41 may be the same as the main component of the layer 4.

[0023] The average diameter of the closed pores present in the first convex portion 41 may be 1.5 times or less the average diameter of the closed pores present in the vicinity of the first convex portion 41 of the lid 2. In this case, since the closed pores present in the first convex portion 41 are small, the occurrence of microcracks originating from the closed pores of the first convex portion 41 and the progression of the microcracks to the lid 2, the bottomed cylindrical body 3, and the layer 4 can be suppressed.

[0024] The average diameter of the closed pores present in the first convex portion 41 may be 0.8 times or more the average diameter of the closed pores present in the vicinity of the first convex portion 41 of the lid body 2. In addition, the average diameter of the closed pores present in the first convex portion 41 may be smaller than the average diameter of the closed pores present in the vicinity of the first convex portion 41 of the lid body 2.

[0025] The average diameter of the closed pores is not limited to a specific value. For example, the average diameter of the closed pores present in the first convex portion 41 may be set to about 0.8 μm or more and 1.7 μm or less. In addition, the average diameter of the closed pores present in the vicinity of the first convex portion 41 of the lid body 2 may be set to about 1 μm or more and 2.1 μm or less.

[0026] The average diameter of the closed pores present in the vicinity of the first convex portion 41 and the first convex portion 41 of the lid body 2 may be measured by, for example, cross-sectional observation using a scanning electron microscope. A sample including a part of the lid body 2 to be measured and the first convex portion 41 in contact with the lid body 2 is cut out and embedded in a polyester-based resin to form a cylindrical sample. Here, the cross section of the sample may be mirror-finished using diamond abrasive grains. The magnification may be set to, for example, 500 times. The observation range for observing the cross section of the sample may be set to, for example, a horizontal length of 256 μm and a vertical length of 192 μm, dividing the lid body 2 and the first convex portion 41.

[0027] The vicinity of the first protrusion 41 of the lid body 2 refers to the remainder of the lid body 2 when the cross-sectional area of ​​the first protrusion 41 in the observation range is set to 25% to 50%, assuming that the observation range including a part of the lid body 2 and a part of the first protrusion 41 in contact with the lid body 2 is 100%. The cross-sectional area of ​​the remainder of the lid body 2 is also set to 25% to 50% in this observation range.

[0028] Each divided observation area may be analyzed, and the average diameter of the closed pores may be obtained by applying a particle analysis technique using the image analysis software "Azokun (Ver2.52)" (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.). The average diameter of the closed pores may be the average value of the equivalent circle diameters.

[0029] In the analysis, the particle analysis setting conditions were: particle brightness dark, binarization method manual, threshold value 70-100, small figure removal area 0.3μm 2 and a noise reduction filter.

[0030] In the above measurement, the threshold value was set to 70 to 100, but the threshold value can be adjusted according to the brightness of the image, which is the observation range. The brightness of the particles was set to dark, the binarization method was set to manual, and the small figure removal area was set to 0.3 μm 2 With a noise reduction filter, the threshold value can be adjusted so that the markers appearing in the image match the shape of the closed pores.

[0031] The layer 4 may have a second convex portion 42 connected to the layer 4 on the outer periphery side of the bottomed cylindrical body 3. In this case, even when used in a highly corrosive environment, the layer 4 is less susceptible to corrosion, reducing the risk of separation between the lid 2 and the bottomed cylindrical body 3, allowing for long-term use. The main component of the second convex portion 42 may be the same as the main component of the layer 4.

[0032] The average diameter of the closed pores present in the second convex portion 42 may be 1.5 times or less the average diameter of the closed pores present in the vicinity of the second convex portion 42 of the lid 2. In this case, since the closed pores present in the second convex portion 42 are small, the occurrence of microcracks originating from the closed pores of the second convex portion 42 and the progression of the microcracks to the lid 2, the bottomed cylindrical body 3, and the layer 4 can be suppressed.

[0033] The average diameter of the closed pores present in the second convex portion 42 may be 0.8 times or more the average diameter of the closed pores present in the vicinity of the second convex portion 42 of the lid 2. In addition, the average diameter of the closed pores present in the second convex portion 42 may be smaller than the average diameter of the closed pores present in the vicinity of the second convex portion 42 of the lid 2.

[0034] For example, the average diameter of the closed pores present in the second convex portion 42 may be set to about 0.8 μm or more and 1.7 μm or less. Also, the average diameter of the closed pores present in the vicinity of the second convex portion 42 of the lid 2 may be set to about 1 μm or more and 2.1 μm or less.

[0035] The average diameter of the closed pores present in the second convex portion 42 and in the vicinity of the second convex portion 42 of the lid body 2 may be measured by, for example, cross-sectional observation using a scanning electron microscope. A sample including a part of the lid body 2 to be measured and the second convex portion 42 in contact with the lid body 2 is cut out and embedded in a polyester-based resin to form a cylindrical sample. Here, the cross section of the sample may be mirror-finished using diamond abrasive grains. The magnification may be set to, for example, 500 times. The observation range for observing the cross section of the sample may be set to, for example, a horizontal length of 256 μm and a vertical length of 192 μm, dividing the lid body 2 and the second convex portion 42.

[0036] The vicinity of the second convex portion 42 of the lid body 2 refers to the remainder of the lid body 2 when the observation range including a part of the lid body 2 and a part of the second convex portion 42 in contact with the lid body 2 is taken as 100%, and the cross-sectional area of ​​the second convex portion 42 is set to be 25% or more and 50% or less.

[0037] When the second convex portion 42 is not in contact with the lower surface 22 of the lid body 2 (i.e., the outer peripheral surface 35 of the bottomed cylindrical body 3 and the outer peripheral surface of the lid body 2 are flush), the vicinity of the second convex portion 42 of the lid body 2 refers to the remainder of the lid body 2 when the cross-sectional area of ​​the second convex portion 42 in the observation range is set to be 25% to 50%, assuming that the observation range including the corner formed by the outer peripheral surface of the lid body 2 and the lower surface of the lid body 2 and a part of the second convex portion 42 is 100%. In either case, the cross-sectional area of ​​the remainder of the lid body 2 is set to be 25% to 50%. After this, the average diameter of the closed pores can be obtained using the same method as described above.

[0038] The average diameter of closed pores present in lower layer 23 including lower surface 22 of lid 2 may be smaller than the average diameter of closed pores present in upper layer 25 including upper surface 24 of lid 2. In this case, the hardness of lower surface 22 is higher than that of upper surface 24, improving the wear resistance of lower surface 22. On the other hand, upper surface 24 is more likely to experience large vibration due to motor rotation than lower surface 22, but this vibration can be reduced.

[0039] The lower layer 23 may be located closer to the lower surface 22 than the center 2a in the thickness direction of the lid 2. The upper layer 25 may be located closer to the upper surface 24 than the center 2a in the thickness direction of the lid 2. For example, the thickness of the lid 2 may be set to about 15 mm or more and 30 mm or less. The average diameter of the closed pores present in the lower layer 23 may be set to about 2 μm or more and 7 μm or less. The average diameter of the closed pores present in the upper layer 25 may be set to about 3 μm or more and 8 μm or less.

[0040] The average diameter of the closed pores present in the lower layer 23 and the upper layer 25 may be measured by, for example, cross-sectional observation using a scanning electron microscope. Samples including the lower layer 23 and the upper layer 25 to be measured may be cut out, and the cross-sections of the samples may be mirror-finished using diamond abrasive grains. The magnification may be set to, for example, 500 times. The observation range for observing the cross-section of the sample may be set to, for example, a horizontal length of 256 μm and a vertical length of 192 μm. After this, the average diameter of the closed pores can be obtained using the same method as described above.

[0041] The inner bottom surface 33 and the inner peripheral surface 34 of the bottomed cylindrical body 3 and the lower surface 22 of the lid body 2 may be as-fired surfaces. If the surfaces are as-fired surfaces, there is no crushed layer on the as-fired surfaces, so that falling off of the particles from the as-fired surfaces is suppressed.

[0042] The outer peripheral surface 35 of the bottomed cylindrical body 3 may be a ground surface. In this case, the dimensional accuracy of the outer peripheral surface 35 is high. Therefore, the outer peripheral surface 35 can suppress circumferential runout relative to the inner peripheral surface 34 that forms the axial hole 311, so that runout can be reduced when the classifying rotor 1 is rotated.

[0043] The classifying rotor 1 is not limited to a specific size. For example, the maximum length of the classifying rotor 1 in the direction along the axis S may be set to about 150 mm or more and 220 mm or less. The outermost diameter of the classifying rotor 1 in the direction perpendicular to the axis S may be set to about 280 mm or more and 350 mm or less. The maximum length of the slit 321 in the direction along the axis S may be set to about 120 mm or more and 160 mm or less. The maximum width of the slit 321 in the direction perpendicular to the axis S may be set to about 5 mm or more and 10 mm or less.

[0044] The cross-sectional shape of the slit 321 shown in FIG. 1 is rectangular, but it may be a racetrack shape or an ellipse other than the rectangular shape.

[0045] Next, a manufacturing method of the classification rotor according to the present disclosure will be described using an example of manufacturing the above-mentioned classification rotor 1.

[0046] First, a mixed powder containing 0.3% to 0.42% by mass of magnesium hydroxide converted to oxide (MgO), 0.03% to 0.05% by mass of silicon oxide, 0.01% to 0.02% by mass of calcium carbonate converted to oxide (CaO), and the remainder being aluminum oxide is weighed out and placed in a rotary mill together with a solvent such as water, and mixed with ceramic balls made of aluminum oxide with a purity of 99.5% or more and 99.99% or less.

[0047] Next, a molding binder such as polyvinyl alcohol, polyethylene glycol, acrylic resin, etc. is added and mixed to obtain a slurry. Here, the amount of molding binder added is 2 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the mixed powder.

[0048] Next, the slurry is spray-dried using a spray dryer to obtain granules. The granules are molded by a CIP (Cold Isostatic Pressing) method at a pressure of, for example, 80 MPa to 100 MPa to obtain disk-shaped and cylindrical molded bodies. These molded bodies are then subjected to cutting or other processing to obtain a precursor A of the lid body 2 and a precursor B of the bottomed cylindrical body 3, respectively.

[0049] Here, a paste containing a powder mainly composed of aluminum oxide, a cellulose-based polysaccharide, and a solvent is prepared.

[0050] Specifically, a solvent such as water or ethanol is added to the mixed powder so that the volume ratio of mixed powder:solvent is 55-60:40-45, and the total of the solvent and mixed powder is 100 parts by mass. To this 100 parts by mass, 8 parts by mass to 20 parts by mass of cellulose polysaccharide is added, and these are placed in a storage container in a stirring device and mixed and stirred to obtain a paste.

[0051] Here, the cellulose polysaccharide is, for example, at least one of methyl cellulose, ethyl cellulose, ethyl methyl cellulose, hydroxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, carboxymethyl cellulose, carboxymethyl ethyl cellulose, and carboxyethyl cellulose.

[0052] The average diameter of the closed pores may be adjusted, for example, by the conditions when stirring the paste. For example, when the average diameter of the closed pores present in the first convex portion 41 is set to 1.5 times or less of the average diameter of the closed pores present in the vicinity of the first convex portion 41 of the lid body 2, the rotation speed of the stirrer may be set to 1200 rpm or more and 1600 rpm or less, and the rotation time may be set to 5 minutes or more and 15 minutes or less. When the average diameter of the closed pores present in the first convex portion 41 is set to be smaller than the average diameter of the closed pores present in the vicinity of the first convex portion 41 of the lid body 2, the rotation speed may be increased to 1400 rpm or more and 1600 rpm or less, and the rotation time may be set to 5 minutes or more and 15 minutes or less.

[0053] By stirring the paste within such a range of stirring conditions, it is possible to adjust the average diameter of the closed pores to satisfy the above-mentioned relationship. The above points are also applicable to the adjustment of the average diameter of the closed pores present in the second convex portion 42.

[0054] After the paste is applied to the opposing surfaces of at least one of precursor A and precursor B, the opposing surfaces are placed facing each other and precursor A and precursor B are pressurized, for example, at a pressure of 20 kPa to 40 kPa. At this time, the paste may be allowed to protrude from the opposing surfaces on the inner and outer circumferential sides of precursor B. Then, a precursor in which precursor A and precursor B are connected is obtained by the above pressurization.

[0055] Next, the paste is dried by keeping it at room temperature for 12 to 48 hours while adjusting the humidity, and then the precursor is fired in an air atmosphere at a temperature of 1500°C to 1700°C for 5 to 8 hours to obtain the classification rotor 1.

[0056] Here, in order to obtain a classification rotor in which the average diameter of closed pores in the lower layer, including the lower surface of the lid body 2, is smaller than the average diameter of closed pores in the upper layer, including the upper surface of the lid body 2, precursor B is made thick in advance (for example, more than twice the thickness of the lid body 2), and after firing, the upper layer side and the lower layer side are ground so that the grinding amount is greater on the upper layer side than on the lower layer side.

[0057] The above-mentioned manufacturing method is one example of a method for manufacturing the classification rotor 1. Therefore, it goes without saying that the classification rotor 1 is not limited to one manufactured by the above-mentioned manufacturing method.

[0058] <Centrifugal air classifier> Next, a centrifugal air classifier according to a non-limiting embodiment of the present disclosure will be described with reference to the drawings, taking as an example a case in which the above-described classifying rotor 1 is used.

[0059] As shown in an example in Fig. 4, a centrifugal air current classifier 100 (hereinafter sometimes referred to as "classifier 100") is configured using a classification rotor 1. Since the classifier 100 is configured using a classification rotor 1 that is highly resistant to wear and is lightweight, stable classification is possible for a long period of time.

[0060] The classifier 100 may comprise a casing 101 that houses the classifying rotor 1 therein, a motor 102 that rotates the classifying rotor 1, a supply pipe 103 that supplies raw material to the inside of the casing 101, a plurality of nozzles 104 located below the supply pipe 103 and supplying compressed air to the inside of the casing 101, and an outlet pipe 105 that transports the fine powder classified by the classifying rotor 1 to the outside of the casing 101.

[0061] Although the embodiments of the present disclosure have been described above, it goes without saying that the present disclosure is not limited to the above-described embodiments, and any embodiment may be used without departing from the gist of the present disclosure. [Explanation of symbols]

[0062] 1. Classifying rotor 2. Cover 21...Through hole 22...Bottom surface 23...Lower part 24...Top surface 25. Upper Management 2a...center 3...Bottomed cylindrical body 31...Bottom 311... Shaft hole 312...Cylinder 32...peripheral wall part 321...Slit 322...end face 33...Inner bottom surface 34...Inner peripheral surface 35...outer surface 4...layer 41...First protrusion 42...Second protrusion 100 Centrifugal air classifier 101 Casing 102 Motor 103...supply pipe 104 Nozzle 105...Export pipe S...axis

Claims

1. A lid body made of ceramic having a through hole in a thickness direction; a bottomed cylindrical body made of ceramic having a bottom portion having an axial hole coaxial with the through hole and a peripheral wall portion connected to the bottom portion and having a plurality of slits; the lower surface of the lid body and the end surface of the peripheral wall portion are joined via a layer made of ceramics, A classification rotor, wherein an average diameter of closed pores present in a lower layer portion including a lower surface of the lid body is smaller than an average diameter of closed pores present in an upper layer portion including an upper surface of the lid body.

2. The classifying rotor according to claim 1 , wherein the layer has a first protrusion connected to the layer on an inner circumferential side of the bottomed cylindrical body.

3. 3. The classification rotor according to claim 2, wherein an average diameter of closed pores present in the first convex portion is 1.5 times or less an average diameter of closed pores present in the vicinity of the first convex portion of the lid body.

4. 4. The classifying rotor according to claim 1, wherein the layer has a second protrusion connected to the layer on the outer circumferential side of the bottomed cylindrical body.

5. 5. The classification rotor according to claim 4, wherein an average diameter of closed pores present in the second convex portion is 1.5 times or less an average diameter of closed pores present in the vicinity of the second convex portion of the lid body.

6. 6. The classifying rotor according to claim 1, wherein the inner bottom surface and inner peripheral surface of the bottomed cylindrical body and the lower surface of the lid are as-fired surfaces.

7. 7. The classifying rotor according to claim 1, wherein the outer peripheral surface of the bottomed cylindrical body is a ground surface.

8. A centrifugal air classifier using the classification rotor according to any one of claims 1 to 7.

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