JP2013085992A - Air flow classifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air flow classifier capable of easily adjusting a classification point.SOLUTION: The air flow classifier includes: a classification plate 2 having a conical upper surface 2a gradually becoming higher toward the center; a casing 3 storing the classification plate 2 and forming a classification chamber 9 above the classification plate 2; an injection nozzle 10 for injecting solid-gas mixed fluid containing gas and raw material powder into the classification chamber 9 and forming a swirling airflow in the classification chamber 9; a fine powder discharge port 6 opening at the center of the classification plate 2; and a coarse powder discharge port 8 opening along the outer periphery of the classification plate 2. In the classification chamber 9, impellers 14, which suck gas from the center part of the swirling airflow while rotating at high speed and send the gas to the outer periphery of the swirling airflow, are coaxially provided at intervals above the classification plate 2.

Description

  The present invention relates to an airflow classifier that centrifuges raw powder into coarse powder and fine powder using a swirling airflow.

  In general, when manufacturing fine powder such as toner used in image forming apparatuses such as copying machines, the raw powder is made up of coarse powder and fine powder using a swirling airflow in order to keep the powder particle size within a predetermined range. An air-flow classifier that performs centrifugal separation is used.

  As such an airflow classifier, for example, the one described in FIG. The airflow classifier includes a classification plate having a conical upper surface that gradually increases toward the center, a casing that accommodates the classification plate and forms a classification chamber above the classification plate, and high-pressure air in the classification chamber. An air nozzle that injects a solid-gas mixed fluid of raw material powder to form a swirling airflow in the classification chamber, a fine powder discharge port that opens in the center of the classification plate, and a coarse powder discharge port that opens along the outer periphery of the classification plate; Have

  This airflow classifier forms a swirling airflow toward the center in the classification chamber by injecting a solid-air mixed fluid from the air nozzle into the classification chamber. The raw material powder in the solid-gas mixed fluid is separated into coarse powder and fine powder by the moving gas flow. That is, the coarse powder moves radially outward in the classification chamber by the outward centrifugal force due to the swirling of the air flow, and is discharged from the coarse powder discharge port on the outer periphery of the classification plate, and the fine powder is the air moving toward the center. It moves to the inside in the radial direction in the classification chamber by the flow, and is discharged from the fine powder outlet in the center of the classification plate.

  Further, in this classifier, an acceleration air nozzle is provided separately from the air nozzle for injecting the solid-air mixed fluid, and the swirling speed of the airflow in the classification chamber is increased by the high pressure air injected from the acceleration air nozzle into the classification chamber, The classification point is made small.

JP 2010-149090 A

  By the way, when classifying powder using the airflow classifier described in Patent Document 1, in order to adjust the classification point, the height dimension of the classification chamber is set as described in paragraph 0054 of the same document. The balance between the swirling speed of the air flow in the classification chamber and the moving speed of the air toward the center was changed by adjusting the air volume of the high-pressure air injected from the acceleration air nozzle or adjusting the classification point. .

  However, the operation of changing the height dimension of the classification chamber (specifically, the operation of adding or decreasing the number of dividing rings constituting the peripheral wall of the classification chamber) needs to be performed after the operation of the classifier is temporarily stopped. It is complicated. In addition, it is not easy to find out how much the classification chamber height and high-pressure air flow should be set in order to match the classification point to the target value. Had to make adjustments locally.

  Moreover, since the airflow classifier of patent document 1 uses the high pressure air which injects from the air nozzle for acceleration separately from the high pressure air which injects from an air nozzle as a part of solid-gas mixed fluid, the air consumption in a classifier There was a problem that there were many. In particular, when it is necessary to use a high-pressure inert gas instead of high-pressure air due to the nature of the powder raw material, a large consumption of gas in the classifier increases the operating cost, which is uneconomical.

  The problem to be solved by the present invention is to provide an airflow classifier capable of easily adjusting the classification point.

  In order to solve the above problems, a classification plate having a conical upper surface that gradually increases toward the center, a casing that accommodates the classification plate and forms a classification chamber above the classification plate, and a gas in the classification chamber An injection nozzle that injects a solid-gas mixed fluid of the raw material powder and forms a swirling airflow in the classification chamber, a fine powder discharge port that opens in the center of the classification plate, and a coarse powder that opens along the outer periphery of the classification plate In the airflow classifier having a discharge port, an impeller that sucks gas from the central portion of the swirling airflow and sends it to the outer peripheral portion of the swirling airflow while rotating at a high speed in the classification chamber is spaced above the classification plate. And provided coaxially.

  In this way, by rotating the impeller in the classification chamber at a high speed, gas is sucked into the impeller from the central portion of the swirling airflow, and the sucked gas is sent to the outer peripheral portion of the swirling airflow at a swirling speed. The swirling speed of the airflow in the classification chamber becomes higher than when there is no impeller, and mixing of coarse powder on the fine powder side can be prevented. Then, by changing the rotational speed of the impeller, it is possible to adjust the classification point by changing the turning speed of the airflow in the classification chamber.

  It is preferable that an annular guide member is provided on the outer diameter side of the impeller to guide the gas sent radially outward from the impeller and guide it radially inward from the coarse powder outlet. In this way, by preventing the gas sent from the impeller from blowing directly into the coarse powder outlet, the fine powder present in the vicinity of the coarse powder outlet is reduced by the flow of gas sent from the impeller. It is possible to prevent a situation of falling into the discharge port.

  The said airflow type classifier can employ | adopt the thing of the structure which interrupted | blocked the classification room from external air so that external air may not flow into a classification room. In this way, fine metal powders that may oxidize and burn when exposed to oxygen (for example, powder materials of sintered magnets based on neodymium iron boron), and powders that are extremely reluctant to absorb moisture (such as pharmaceuticals and foods) In addition, using an inert gas such as nitrogen gas, argon gas or helium gas, or air from which moisture has been removed by a desiccant is used as the gas of the solid-gas mixed fluid, so that classification by an airflow classifier can be performed. . And since the swirling speed of the airflow in the classification chamber can be increased by using the impeller, the acceleration inertness for increasing the swirling speed of the airflow in the classification chamber separately from the inert gas injected from the injection nozzle. There is no need to supply gas from the outside, and the consumption of inert gas in the classifier can be suppressed.

  Further, the impeller uses a rotating disk unit that is coaxially disposed opposite to and above the classifying plate, and a plurality of blades fixed to the lower surface of the disk unit. preferable. In this way, the impeller blades rotating at high speed collide with the powder particles in the airflow swirling on the lower side, so that the agglomerated fine particles can be crushed into a dispersed state. As a result, sharp classification is possible.

  Since the airflow classifier of the present invention can adjust the classification point by changing the rotational speed of the impeller in the classification chamber, it is not necessary to stop the operation of the classifier to adjust the classification point. . Therefore, the adjustment of the classification point is easy.

The front view which shows the airflow classifier of embodiment of this invention Sectional view along the line II-II in FIG. Fig. 1 is an enlarged sectional view of the vicinity of the classification chamber of the airflow classifier The figure which looked at the impeller shown in FIG. 1 from the lower side (A) is a figure which shows the other example of an impeller shown in FIG. 4, (b) is a figure which shows the other example of the impeller shown in FIG. Piping diagram showing a crusher unit using the airflow classifier shown in FIG. The figure which shows the correspondence of the rotation speed of an impeller when using the grinder unit shown in FIG. 6, and a classification point (A) is a figure which shows the particle size distribution of the fine powder obtained using the grinder unit shown in FIG. 6, (b) is a figure which shows the particle size distribution of the fine powder obtained using the conventional grinder unit.

  FIG. 1 shows an airflow classifier 1 according to an embodiment of the present invention. The airflow classifier 1 includes a classification plate 2 and a casing 3 that accommodates the classification plate 2. The casing 3 is formed by detachably connecting an upper casing 3A and a lower casing 3B.

  The classification plate 2 includes a separate core 4 having a conical upper surface 2 a that gradually increases toward the center, and an annular plate 5 fixed to the lower surface of the separate core 4. A fine powder discharge port 6 is opened at the center of the classification plate 2, and a fine powder discharge cylinder 7 that passes through the wall surface of the casing 3 and communicates with the outside is connected to the fine powder discharge port 6. Further, an annular coarse powder outlet 8 that opens along the outer periphery of the classification plate 2 is provided between the outer periphery of the classification plate 2 and the inner periphery of the casing 3. The coarse powder discharge port 8 communicates with the lower end opening of the casing 3.

  As shown in FIG. 3, the classification plate 2 has an annular stepped portion 2 b that is continuous with the outer diameter side of the conical upper surface 2 a and has a lower outer diameter side. In the figure, the stepped portion 2b employs a classification plate 2 in which the separate core 4 and the annular plate 5 are formed separately and joined together, and a cylindrical surface 4a is formed on the outer periphery of the separate core 4, and the cylinder The stepped portion 2b is formed outside the cylindrical surface 4a by making the outer diameter of the annular plate 5 larger than the outer diameter of the surface 4a, but the separate core 4 and the annular plate 5 are formed integrally. The classification plate 2 may be adopted, and the step portion 2b may be directly provided on the classification plate 2.

  Above the classification plate 2, a classification chamber 9 surrounded by the upper casing 3A and the classification plate 2 is formed. Between the upper casing 3A and the lower casing 3B, an annular powder supply header 11 in which an injection nozzle 10 for injecting a solid-gas mixed fluid of gas and raw material powder is formed in the classification chamber 9 is incorporated.

  As shown in FIG. 2, an annular powder supply passage 12 is formed on the outer peripheral side of the powder supply header 11, and the solid-gas mixed fluid supplied from the outside of the casing 3 is powdered through the powder supply cylinder 13. It is introduced into the supply passage 12.

  A plurality of injection nozzles 10 are formed at equal intervals in the circumferential direction on the powder supply header 11. Each injection nozzle 10 communicates between the powder supply passage 12 and the classification chamber 9 and introduces and injects the solid-gas mixed fluid in the powder supply passage 12 into the classification chamber 9. Each injection nozzle 10 is formed to inject in a direction inclined with respect to the radial direction so that the solid-gas mixed fluid injected from each injection nozzle 10 forms a swirling airflow in the classification chamber 9. It has become.

  In the figure, the injection nozzle 10 is formed by processing a groove from the outer periphery to the inner periphery of the powder supply header 11 on the lower surface of the powder supply header 11, but the injection nozzle 10 is formed by other methods. Alternatively, for example, a large number of guide vanes (not shown) inclined with respect to the radial direction may be arranged at intervals in the circumferential direction, and the gap between the adjacent guide vanes may be used as the injection nozzle 10.

  As shown in FIG. 3, an impeller 14 is coaxially provided in the classification chamber 9 with a space above the classification plate 2. The impeller 14 is a centrifugal impeller that sucks gas in the axial direction when it is rotationally driven, and sends the gas radially outward, and is a disk portion that is coaxially disposed opposite to and above the classification plate 2. 15 and a plurality of blades 16 fixed to the lower surface of the disk portion 15.

  As shown in FIG. 4, each blade 16 is arranged to extend linearly in the radial direction. As shown in FIG. 3, the shape of each blade 16 is a shape in which the axial height of the blade 16 gradually increases from the outer diameter side toward the inner diameter side. So that the diameter of the circle portion connecting the highest position in the axial direction is substantially the same as the diameter of the fine powder outlet 6 (that is, the circle portion connecting the highest position of the upper surface 2a of the classification plate 2). Is formed. The distance between the impeller 14 and the classification plate 2 is gradually narrowed from the outer diameter side toward the inner diameter side so that a space having a size that does not hinder the center-oriented swirling airflow exists at the narrowest distance. An impeller 14 is arranged. The outer diameter of the impeller 14 is larger than the diameter of the fine powder outlet 6.

  A rotating shaft 17 is fixed at the center of the disk portion 15. The rotary shaft 17 is rotatably supported by a rolling bearing 19 incorporated in the ceiling wall 18 of the classification chamber 9, and the rotation of the electric motor 20 (see FIG. 1) is input to the rotary shaft 17. . In FIG. 1, the rotary shaft 17 and the rotor shaft 21 of the electric motor 20 are directly connected via a shaft coupling 22, but the rotary shaft 17 and the rotor shaft 21 of the electric motor 20 are connected via a transmission belt or the like. May be.

  The electric motor 20 is connected to a motor control device 23 (see FIG. 6) that can change the rotation speed of the electric motor 20 by an external operation, and can adjust the rotating shaft 17 of the impeller 14 within a range of 0 to 10000 rpm. It has become. In addition to controlling the number of revolutions of the electric motor 20, the motor control device 23 has a function of monitoring the load on the impeller 14 based on the voltage and current value of the electric motor 20.

  As shown in FIG. 3, the disk portion 15 is arranged close to the ceiling wall 18 of the classification chamber 9. A purge passage 24 for injecting a purge gas into the gap between the disk portion 15 and the ceiling wall 18 is provided in the ceiling wall 18 of the classification chamber 9. The purge passage 24 includes an annular groove 25 that opens on the lower surface of the ceiling wall 18 so as to surround the rotary shaft 17, and a gas supply passage 26 that introduces a purge gas into the annular groove 25 from the outside of the casing 3. By injecting gas from the annular groove 25 into the gap between the disk portion 15 and the ceiling wall 18, the powder particles in the classification chamber 9 are prevented from accumulating in the gap between the disk portion 15 and the ceiling wall 18.

  If the impeller 14 is formed by sintering ceramics, coated with ceramics or coated with hard urethane on the surface, it effectively prevents wear due to contact with powder particles. can do.

  An annular guide member 27 is provided on the outer diameter side of the impeller 14 of the ceiling wall 18 of the classification chamber 9, and the gas sent out in the radial direction from the impeller 14 flows along the inner periphery of the guide member 27. It is guided downward along the guide surface 28. Here, the inner diameter of the guide surface 28 is larger than the outer diameter of the impeller 14 and smaller than the outer diameter of the classifying plate 2, and the gas guided downward along the guide surface 28 is discharged from the coarse powder. It is guided radially inward from the outlet 8. The lower surface of the guide member 27 is formed in an inverted conical shape that gradually increases toward the center.

  The step portion 2b of the classification plate 2 is formed at a height position for receiving the solid-gas mixed fluid ejected horizontally from the ejection nozzle 10. The gas inlet into the classification chamber 9 is only the injection nozzle 10 and the purge passage 24. That is, the classification chamber 9 is not provided with an inlet for outside air (that is, air in the atmosphere outside the casing 3), and is configured to be blocked from outside air so that the outside air does not flow into the classification chamber 9.

  FIG. 6 shows a pulverizer unit using the airflow classifier 1 having the above configuration.

  This pulverizer unit pulverizes the coarse powder discharged from the lower end opening of the casing 3 of the airflow classifier 1 and the airflow classifier 1 by colliding with the collision member 30 together with the gas, and the pulverized powder particles , And a circulation passage 32 for introducing the solid-gas mixed fluid discharged from the jet pulverizer 31 into the powder supply cylinder 13 of the airflow classifier 1, It consists of an injection feeder 34 that feeds the raw material powder together with gas in the middle of the circulation passage 32.

  Connected to the powder inlet 33 of the injection feeder 34 is a continuous quantitative supply machine (not shown) for continuously supplying the raw material powder at a constant supply speed. The injection feeder 34 continuously sucks the raw material powder supplied from the continuous quantitative feeder, mixes the raw material powder with gas, and continuously feeds it.

  A tank 36 of an inert gas (for example, nitrogen gas, argon gas, or helium gas) is connected to the gas supply port 35 of the jet crusher 31, and an inert gas tank 36 is also connected to the gas supply port 37 of the injection feeder 34. Is connected. An inert gas tank 36 is also connected to the purge gas supply passage 26 provided in the casing 3 of the airflow classifier 1.

  Connected to the fine powder discharge cylinder 7 of the airflow classifier 1 is a cyclone solid-gas separation device 38 that separates the solid-gas mixed fluid discharged from the fine powder discharge cylinder 7 into fine powder and inert gas. Further, a bag filter 40 for collecting fine powder remaining in the inert gas discharged from the solid-gas separator 38 is connected to the gas outlet 39 of the solid-gas separator 38. A compressor 42 is connected to the gas discharge port 41 of the bag filter 40, and a tank 36 is connected to the discharge port of the compressor 42. The compressor 42 compresses the inert gas discharged from the bag filter 40 and sends the compressed inert gas into the tank 36.

  Next, the operation of the pulverizer unit will be described.

  When the raw material powder is introduced into the powder inlet 33 of the injection feeder 34 while the inert gas in the tank 36 is supplied to the injection feeder 34, the solid-gas mixed fluid of the inert gas and the raw material powder is injected into the injection feeder 34. The solid-gas mixed fluid is sent to the powder supply cylinder 13 of the airflow classifier 1 through the circulation passage 32.

  As shown in FIG. 2, the solid-gas mixed fluid fed into the casing 3 from the powder supply cylinder 13 is injected into the classification chamber 9 from the plurality of injection nozzles 10 through the powder supply passage 12. . The solid-gas mixed fluid ejected from each ejection nozzle 10 forms a swirling airflow (semi-free vortex) directed toward the center in the classification chamber 9. At this time, since the coarse powder contained in the solid-gas mixed fluid injected from the injection nozzle 10 is blocked by the step portion 2b of the classification plate 2, the solid-gas concentration in the classification chamber 9 (the powder occupied in the solid-gas mixed fluid) Even when disturbance of the ratio of body particles occurs, it is possible to prevent the coarse powder from jumping into the fine powder outlet 6.

  During operation of the airflow classifier 1, the impeller 14 in the classification chamber 9 is rotated at a high speed. Thereby, the turning speed of the airflow in the classification chamber 9 can be increased. That is, when the impeller 14 is rotated at a high speed, the impeller 14 acts as a centrifugal impeller that sucks gas in the axial direction and sends gas outward in the radial direction. Therefore, as shown by the arrows in FIG. An inert gas containing a part of the raw material powder is sucked into the impeller 14 from the center of the airflow directed toward the center between the plate 2 and the impeller 14, and the sucked inert gas is classified into the classification plate. 2 and the impeller 14 are sent to the outer periphery of the airflow directed toward the center at a turning speed, and the sent inert gas accelerates the turning speed of the airflow directed toward the center in the classification chamber 9. Further, the swirling airflow directed toward the center in the classification chamber 9 is also accelerated by the forced vortex generated in the vicinity of the impeller 14.

  Thus, when the swirling airflow directed toward the center is formed in the classification chamber 9 by the injection from the injection nozzle 10 and the rotation of the impeller 14, the outward centrifugal force acting due to the swirling of the airflow and the centerward direction are formed. The raw material powder in the solid-gas mixed fluid is separated into coarse powder and fine powder by the flow of the moving inert gas.

  That is, the coarse powder moves radially outward in the classification chamber 9 by the outward centrifugal force due to the swirling of the air flow, and is discharged from the coarse powder discharge port 8 on the outer periphery of the classification plate 2, and the fine powder is directed toward the center. The inside of the classification chamber 9 is moved radially inward by the flow of the moving inert gas, and is discharged from the fine powder discharge port 6 at the center of the classification plate 2. Here, by changing the rotational speed of the impeller 14, the swirling speed of the airflow directed toward the center in the classification chamber 9 is changed to adjust the classification point (the particle size of the powder particles discharged as fine powder). Is possible.

  The coarse powder discharged from the coarse powder discharge port 8 on the outer periphery of the classification plate 2 flows into the jet pulverizer 31 from the lower end opening of the casing 3 and is pulverized, as shown in FIG. It is discharged from the jet crusher 31 in a state of being mixed with an inert gas flowing into the machine 31. The solid-gas mixed fluid discharged from the jet pulverizer 31 is sent to the powder supply cylinder 13 of the airflow classifier 1 through the circulation passage 32 and is again centrifuged into coarse powder and fine powder. The coarse powder is returned to the jet pulverizer 31 from the lower end opening of the casing 3 and repeatedly pulverized until a predetermined particle size is obtained.

  The fine powder discharged from the fine powder discharge port 6 at the center of the classification plate 2 is collected by the solid-gas separation device 38. The ultrafine powder that has not been collected by the solid-gas separation device 38 is collected by the bag filter 40. The inert gas that has passed through the bag filter 40 is compressed by the compressor 42 and reused.

  As described above, the airflow classifier 1 sucks gas into the impeller 14 from the center of the swirling airflow by rotating the impeller 14 in the classification chamber 9 at high speed, and the sucked gas is swirled into the swirling airflow. Therefore, the swirling speed of the airflow in the classification chamber 9 is higher than when no impeller 14 is provided, and mixing of coarse powder on the fine powder side can be prevented. Then, by changing the rotational speed of the impeller 14, the swirl speed of the airflow in the classification chamber 9 can be changed to adjust the classification point.

  Moreover, since this airflow classifier 1 blocks the classification chamber 9 from the outside air so that the outside air does not flow into the classification chamber 9, as shown in the above embodiment, an inert gas is used as the gas of the solid-gas mixed fluid. By using it, it is possible to classify metal fine powder (for example, powder material of a neodymium iron boron-based sintered magnet) that may oxidize and burn when exposed to oxygen. Similarly, by using air from which moisture has been removed by a desiccant as the gas of a solid-gas mixed fluid, it is also possible to classify powders (medicine, food, etc.) that are extremely disliked by moisture absorption.

  In addition, since the airflow classifier 1 uses the impeller 14 to increase the swirling speed of the airflow in the classification chamber 9, the airflow in the classification chamber 9 is separated from the inert gas injected from the injection nozzle 10. It is not necessary to supply an inert gas for acceleration to increase the turning speed of the gas, and the gas consumption in the airflow classifier 1 can be suppressed, and the operating cost of the airflow classifier 1 is reduced. It is possible.

  In addition, since the airflow classifier 1 is provided with the guide member 27 on the outer diameter side of the impeller 14, it is possible to perform a sharp classification that prevents the fine powder from being mixed into the coarse powder side. That is, if classification is performed with the guide member 27 removed, the gas sent out from the impeller 14 is guided downward along the inner peripheral surface of the upper casing 3A and directly blows into the coarse powder outlet 8. At this time, the fine powder existing in the vicinity of the coarse powder outlet 8 may fall into the coarse powder outlet 8 due to the flow of gas sent out from the impeller 14. On the other hand, in this airflow classifier 1, the gas sent out radially outward from the impeller 14 is guided downward by the guide member 27 provided on the outer diameter side of the impeller 14, and the coarse powder outlet 8 Since the gas sent out from the impeller 14 can be prevented from blowing directly into the coarse powder outlet 8, as a result, it is present in the vicinity of the coarse powder outlet 8. It is possible to prevent the fine powder to fall into the coarse powder outlet 8 due to the gas flow sent out from the impeller 14.

  By the way, fine powder is more likely to aggregate due to static electricity or moisture on the surface of the particle than coarse powder. When the fine powder in the solid-gas mixed fluid forms aggregated particles, the aggregated particles are apparently equivalent to coarse powder. Since it has a particle size, it is classified as a coarse powder and the accuracy of classification is reduced. In particular, when the airflow classifier 1 is used by being incorporated in the above pulverizer unit, when the fine agglomerated particles are classified as a coarse powder, the agglomerated particles are pulverized by the jet pulverizer 31 to further reduce the particle size of the fine powder. Therefore, there is a problem in that ultra fine powder having a particle size smaller than the target particle size is likely to be generated.

  Therefore, in order to enable sharp classification, as the impeller 14, as shown in the above-described embodiment, one having a disk portion 15 and a plurality of blades 16 fixed to the lower surface of the disk portion 15 is used. It is preferable. By doing so, the blades 16 of the impeller 14 rotating at high speed collide with the powder particles in the airflow swirling on the lower side thereof, thereby crushing the agglomerated particles of fine powder into a dispersed state. As a result, it is possible to perform a sharp classification that prevents the fine particles from agglomerating into the coarse particles. In addition, as the impeller 14, it is also possible to employ a centrifugal impeller of a type in which a plurality of blades are provided at intervals in the circumferential direction between a pair of upper and lower opposing disks. By changing the rotational speed of 14, it is possible to adjust the classification point by changing the swirling speed of the air flow in the classification chamber 9.

  In the above embodiment, as illustrated in FIG. 4, the impeller 14 in which the blades 16 are arranged so as to extend linearly in the radial direction has been described as an example. However, as illustrated in FIG. It is also possible to employ an impeller 14 in which a plurality of blades 16 whose diameter side is inclined rearward in the rotational direction than the inner diameter side are arranged at intervals in the circumferential direction, and as shown in FIG. It is also possible to employ an impeller 14 in which a plurality of blades 16 whose outer diameter side is inclined forward in the rotational direction than the inner diameter side are arranged at intervals in the circumferential direction.

  In order to confirm that the classification point of the airflow classifier 1 can be adjusted by changing the rotational speed of the impeller 14, the rotational speed of the impeller 14 of the airflow classifier 1 in the pulverizer unit described above. The test was conducted to measure the particle size of the fine powder recovered by the solid-gas separator 38 according to the number of rotations.

  That is, in the pulverizer unit, the raw material powder is pulverized by the jet pulverizer 31 and classified by the airflow classifier 1, where the rotational speed of the impeller 14 of the airflow classifier 1 is in the range of 4500 to 7000 rpm. The particle size of 50000 powder particles was measured using a Coulter counter for the fine powder collected by the solid-gas separator 38 at each rotation speed. The Coulter Counter detects the change in the electrical resistance value of the electrolyte solution through the aperture when the powder particles pass through the aperture (pore) in the electrolyte solution, and measures the particle size based on the change in the electrical resistance value. To do.

The operating conditions of the pulverizer unit in this test are as follows.
Raw material powder: Toner flakes (2mm pass product)
Gas consumption of the injection feeder 34: 200NL / min
Feeding amount of raw material powder from the injection feeder 34: 1.4 kg / hr, 2.4 kg / hr, 3.1 kg / hr
Gas consumption of jet crusher 31: 2000NL / min
Speed of impeller 14: 4500-7000rpm
Internal pressure of tank 36: 0.6MPa

  Further, when the rotational speed of the impeller 14 is increased while the supply amount of the raw material powder from the injection feeder 34 is constant, the hold-up in which the powder stays in the circulation system of the pulverizer unit at a certain rotational speed. In this case, the amount of raw material powder supplied from the injection feeder 34 was lowered, and the particle size was measured under the condition that the fine powder collection yield was 95% or more.

  In FIG. 7, the measurement result of the particle size of the powder particle collect | recovered as a fine powder is shown. As can be seen from this measurement result, by changing the rotation speed of the impeller 14 of the airflow classifier 1 in the range of 4500 to 7000 rpm, the classification point of the powder particles discharged as fine powder from the fine powder discharge port 6 is reduced to about It can be changed by 4 μm. The classification point refers to the particle size (so-called D50) when the cumulative number from the small particle size side becomes 50% of the total particle size distribution of the powder particles discharged as fine powder.

  8A, in the above test, when the supply amount of the raw material powder from the injection feeder 34 was 2.4 kg / hr and the impeller 14 was rotated at a rotational speed of 6000 rpm, it was recovered as fine powder. The particle size distribution of 50000 powder particles is shown. The particle size distribution shown in FIG. 8B is the particle size distribution of the powder particles recovered as fine powder when a conventional pulverizer unit similar to that in FIG. 6 is configured using a conventional airflow classifier that does not use the impeller 14. It is.

  Comparing FIGS. 8A and 8B, the particle size distribution shown in FIG. 8A has a smaller proportion of ultrafine powder having a particle size of 3 μm or less than the particle size distribution shown in FIG. This is because, in the conventional airflow classifier that does not use the impeller 14, the fine aggregated particles present in the solid-gas mixed fluid apparently have the same particle size as the coarse powder. The particles are pulverized by the jet pulverizer 31 to further reduce the particle size of the fine powder. As a result, it is considered that a relatively large amount of ultrafine powder is generated as shown in FIG. 8B.

  On the other hand, in the airflow classifier 1 of the present invention using the impeller 14, the blades 16 of the impeller 14 rotating at high speed collide with the powder particles in the airflow swirling below. The fine agglomerated particles are crushed into a dispersed state, and as a result, the situation where the fine agglomerated particles flow into the jet pulverizer 31 is prevented, and as shown in FIG. It is thought that it became.

DESCRIPTION OF SYMBOLS 1 Airflow classifier 2 Classifier 2a Upper surface 3 Casing 6 Fine powder discharge port 8 Coarse powder discharge port 10 Injection nozzle 14 Impeller 15 Disk part 16 Blade 27 Guide member

Claims (4)

A classification plate (2) having a conical upper surface (2a) that gradually increases toward the center, and a casing that accommodates the classification plate (2) and forms a classification chamber (9) above the classification plate (2) (3), an injection nozzle (10) for injecting a solid-gas mixed fluid of gas and raw material powder into the classification chamber (9) to form a swirling airflow in the classification chamber (9), and the classification plate ( 2) In the airflow classifier having a fine powder outlet (6) that opens in the center of (2) and a coarse powder outlet (8) that opens along the outer periphery of the classification plate (2).
In the classification chamber (9), an impeller (14) that sucks gas from the central part of the swirling airflow and sends it to the outer peripheral part of the swirling airflow while rotating at high speed is spaced above the classification plate (2). And an airflow classifier characterized by being provided coaxially.   On the outer diameter side of the impeller (14), an annular gas guided radially outward from the impeller (14) is guided downward and guided radially inward from the coarse powder outlet (8). The airflow classifier according to claim 1, further comprising a guide member (27).   The airflow classifier according to claim 1 or 2, wherein the classification chamber (9) is blocked from outside air so that outside air does not flow in.   The impeller (14) is fixed to the lower surface of the disc portion (15), and a rotationally driven disc portion (15) disposed coaxially and opposed above the classification plate (2). The airflow classifier according to any one of claims 1 to 3, comprising a plurality of blades (16).

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