JP2007083104A - Jet mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To give new functions that an average particle diameter of an object to be crushed is changed or a particle distribution width is changed to a jet mill. <P>SOLUTION: The jet mill has a plurality of air nozzles arranged on a ring-like outer wall of a jet mill body so as to be inclined relative to a center of a disc-like cavity and generating an air stream of a high speed in the disc-like cavity; and an exit arranged at an approximately center of the disc-like cavity of the jet mill body. When an effective diameter of the jet mill body is made to ϕN (mm), the arrangement number n of the plurality of air nozzles is represented by the following formula (1): [(N/100)-1]≤n≤[(N/100)+2] wherein [a] represents the maximum integer value of a or less and n is made to an integer of 2 or more. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  According to the present invention, a powder having a large particle diameter (inside of a pulverizing chamber) is supplied by a high-speed air flow supplied from an air nozzle arranged on the outer wall to a pulverizing chamber formed as a cavity in the jet mill body. The present invention relates to a jet mill that continuously pulverizes a material to be pulverized into fine powders having a particle size of the order of micron, and at the same time performs classification by a swirling air flow.

  A jet mill pulverizes coarsely pulverized materials with a high-speed air flow supplied into the pulverization chamber from air nozzles inclined on the outer wall, and classifies the pulverized material with a swirling air flow. However, it is known that the pulverizer is suitable for ultrafine pulverization. The jet mill has a simple structure inside the grinding chamber, and can easily disassemble and assemble the upper and lower surfaces of the grinding chamber, and can be easily cleaned after use. There are features.

  On the other hand, since the object to be crushed is pulverized only by the air flow inside the pulverization chamber, the object to be pulverized should be pulverized to a predetermined particle size, and the particle size variation of the object to be pulverized should be controlled to be small. Is difficult. For this reason, various improvements have been made to pulverize the object to be pulverized to a predetermined particle size or to reduce the variation in particle size. For example, in order to make it possible to adjust the pulverization particle size over a wide range, the inflow angle of the air flow supplied from the air nozzle to the inside of the pulverization chamber can be changed (see Patent Document 1), and the classification accuracy is improved. For this reason, there are known ones in which a special mechanism for classification such as a classification rotor is provided around the outlet pipe (see Patent Document 2).

However, although the swirling fluid energy type pulverizer disclosed in Patent Document 1 enables adjustment of the pulverization particle size over a wide range, the swirling flow is simultaneously pulverized by injecting compressed air. Is formed, and the classification action is only exerted. Therefore, there is a problem that classification accuracy is poor and large particles are discharged.
Further, the horizontal swirling flow type jet mill disclosed in Patent Document 2 improves the low classification accuracy of Patent Document 1, but the swirl flow formed by the compressed air and the swirl flow formed by the classification rotor are different. Since the swirl speeds are different, there are problems such as vortex disturbances and fine powder adhering to the rotor wall.

  In addition, these conventional technologies all have new complicated mechanical parts such as a special mechanism that makes the inflow angle of air flow variable and a special mechanism for classification inside the grinding chamber. It is added inside the grinding chamber. These are the features of the jet mill that the internal structure of the crushing chamber is simple, the upper and lower surfaces of the crushing chamber can be easily disassembled and assembled, and cleaning after use is easy. It was lost and not always satisfactory.

JP 52-44450 A JP-A-63-319067

  By the way, in the conventional jet mill, the number of air nozzles for supplying pulverization air toward the inside of the pulverization chamber is arranged on the average of about 4 to 16 in accordance with the effective diameter of the jet mill. As is well known, the object to be crushed is pulverized by supplying air at a predetermined flow rate from these air nozzles.

  As a result of various studies to further improve the configuration of such a conventional jet mill, the present inventor has found that the size of the jet mill (effective diameter: diameter if circular, long diameter if elliptical, The present inventors have found that there are a number of air nozzles suitable for performing stable pulverization, particularly fine pulverization, corresponding to any of the short diameters or the representative diameters based on these short diameters.

  That is, according to the results of the study by the present inventor, by adopting an appropriate number of air nozzles corresponding to the size of the jet mill, even under the same conditions such as the same device, the same total supply air volume, etc. The jet mill can be provided with new functions such as changing the average particle size of the material to be crushed or changing the particle size distribution width.

  Therefore, the object of the present invention is to provide a jet mill with a new function such as changing the average particle size of the material to be crushed or changing the particle size distribution width. The object is to provide a jet mill having features.

In order to solve the above-described problems, a jet mill according to the present invention includes a jet mill body in which a disk-shaped cavity is formed, and a ring-shaped outer wall of the jet mill body that is inclined with respect to the center of the disk-shaped cavity. A jet mill having a plurality of air nozzles that generate a high-speed air flow in the disk-shaped cavity, and an outlet disposed at substantially the center of the disk-shaped cavity of the jet mill body, The disk-shaped cavity forms a ring-shaped pulverization zone for pulverizing an object to be pulverized by the high-speed air flow supplied from the plurality of air nozzles, and an effective diameter of the jet mill main body is φN (mm) In this case, the number n (lines) of the plurality of air nozzles is expressed by the following formula (1).
[(N / 100) -1] ≦ n ≦ [(N / 100) +2] (1)
Here, [a] represents the maximum integer value of a or less, and n is an integer of 2 or more.
Here, the effective diameter N of the jet mill body refers to the pitch circle diameter connecting the tips of the plurality of air nozzles.

  The characteristic configuration of the jet mill according to the present invention is a jet mill having another basic configuration (for example, Japanese Patent Application No. 2004-255528 “Jet Mill” (Japanese Patent Application Laid-Open No. 2005-131633) filed by the present applicant. No. 1), and having a narrow path that divides the pulverization zone and the classification zone in the cavity of the jet mill body) (claims 2 to 11).

  More specifically, in addition to the above-described configuration, a ring that is disposed inside the pulverization zone, communicates with the exit space, and is located inside the pulverization zone, and classifies objects to be pulverized by the air flow. It is preferable to have a ring-shaped classification zone, and a ring-shaped first narrow path that is disposed between the pulverization zone and the classification zone and that divides and communicates with the pulverization zone and the classification zone. 2).

Here, the jet mill main body includes a substantially disc-shaped upper casing and a lower casing, and the ring-shaped outer wall interposed between the upper casing and the lower casing, and the disc-shaped cavity is It is preferable that it is an internal space formed between the upper casing and the lower casing and inside the ring-shaped outer wall (Claim 3).
Further, it is preferable that the ring-shaped first narrow narrow path is formed at a predetermined interval between an upper surface and a lower surface of the disk-shaped cavity (Claim 4).

In addition, the ring-shaped first narrow path is a ring-shaped that is attached to the upper surface and the lower surface of the cavity substantially parallel to each other at a predetermined interval at a predetermined radial position of the disk-shaped cavity. It is preferable that the channel is a ring-shaped channel (classified ring channel) formed by the barrier.
The ring-shaped grinding zone is an internal space in which the upper surface and the lower surface of the disk-shaped cavity are asymptotic to each other toward the center, and the cavity is narrowed toward the center direction. The first narrow path is a ring-like shape formed between the protrusions on the upper surface and the lower surface of the cavity, which are respectively arranged at a predetermined interval at predetermined positions in the radial direction of the disk-shaped cavity. A channel (classified ring channel) is preferred (Claim 6).

Furthermore, it has a ring-shaped second narrow narrow passage that is disposed between the classification zone and the outlet disposed inside thereof and divides and communicates with the classification zone and the space of the outlet. Preferred (claim 7).
Here, it is preferable that the ring-shaped second narrow path is formed at a predetermined interval between the upper surface and the lower surface of the disk-shaped cavity (Claim 8).

  Further, the outlet is formed by a cylindrical outlet pipe disposed upward or downward at a substantially central portion of the disc-shaped cavity of the jet mill body, and the ring-shaped second narrow path is A projecting portion at the lower end or the upper end of the outlet pipe disposed at a predetermined interval from each other, and a disc or short tube shape disposed above the lower surface or below the upper surface of the substantially central portion of the cavity. It is preferably a ring-shaped channel (outlet ring channel) formed between the protrusions (claim 9).

That is, the ring-shaped second narrow channel (exit ring channel) is disposed at a substantially central portion of the cavity inside the jet mill main body and is projected upward at a lower end of the exit pipe; Discs or short-tube-shaped protrusions arranged on the upper side of the lower surface of the substantially central part are arranged at a predetermined interval from each other, or downward toward the substantially central part of the cavity. A protrusion at the upper end of the outlet pipe disposed and a disk-shaped or short tube-shaped protrusion disposed below the upper surface of the substantially central portion of the cavity are disposed at a predetermined interval. Is preferred.
The outlet pipe is movable in the vertical direction with respect to the jet mill main body, and the interval between the ring-shaped second narrow passages is determined by moving the outlet pipe in the vertical direction. It is preferable that the lower end or the upper end protrusion be adjusted by moving it closer to or away from the disk or short tube-shaped protrusion.

  Further, the outlet is formed by a cylindrical outlet pipe disposed upward or downward at a substantially central portion of the disc-shaped cavity of the jet mill body, and the ring-shaped second narrow path is Between the protruding portion at the lower end or the upper end of the outlet pipe and the ring-shaped convex portion provided on the upper side of the lower surface of the substantially central portion or the lower side of the upper surface, spaced apart from each other by a predetermined distance. It is preferable that the channel is a ring-shaped channel.

  According to the present invention, as will be described in detail below, the size of the jet mill (effective diameter: a diameter if circular, a major axis or a minor axis, or a representative diameter based on these, etc. if elliptical). Correspondingly, by finding that there are a number of air nozzles suitable for stable pulverization, especially fine pulverization, the jet mill can be used even under the same conditions such as the same equipment, the same total supply air flow, etc. There is a remarkable effect that it is possible to provide a new function such as changing the average particle size of the material to be crushed or changing the particle size distribution width.

Hereinafter, a jet mill according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
In the embodiment described below, first, there is no narrow path that separates the pulverization zone and the classification zone in the cavity of the jet mill body as disclosed in the above-mentioned JP-A-2005-131633. An example based on a simple configuration is shown.

  1 is a plan sectional view conceptually showing a jet mill according to a first embodiment of the present invention, FIG. 2 is a side sectional view of the jet mill shown in FIG. 1, and FIG. It is a sectional side view which shows one Embodiment of a specific structure. The jet mill shown here has an inner diameter (specifically, a pitch circle diameter connecting the tips of the air nozzles) of 200 mm.

  As shown in FIGS. 1 to 3, the jet mill according to the first embodiment has a tangent line (or center) to a ring-shaped (cylindrical) outer wall 4 of a disk (cylindrical or hollow disk) -shaped jet mill body 2. The object to be pulverized is pulverized inside the pulverizing chamber 8 in the jet mill body 2 by a high-speed air flow supplied inward from the two air nozzles 6 arranged to be inclined with respect to the line). is there. The crushing chamber 8 is a jet mill body surrounded by a disc-shaped upper plate (upper casing) 10 and a lower plate (lower casing) 12 that form the jet mill body 2 and between the outer wall 4 and the outlet pipe 32. 2 is formed as a disk-shaped (ring donut-shaped or cylindrical) cavity (internal space). Then, as shown in FIG. 3, the upper plate 10, the lower plate 12 and the outer wall 4 are sealed with a sealing material such as an O-ring so that air and fine powder of the pulverized object are not leaked to the outside. Yes.

  As shown in FIG. 1, two air nozzles 6 are provided on the annular outer wall 4 of the jet mill main body 2 so as to be inclined at equal intervals with respect to the tangent line, and are supplied from the air nozzle 6. The air flow is jetted into the grinding chamber 8 at a high speed, and the material to be ground is pulverized mainly by the shearing action of the air flow. Further, when the air flow swirls at high speed inside the crushing chamber 8, the objects to be crushed supplied into the crushing chamber 8 also swirl at high speed, and the swirling motion allows the objects to be crushed to each other or to the crushing chamber. The pulverization is also performed by colliding with the wall surface 8.

  Compressed air supplied from a compressed air source (not shown) is supplied through a pipe line (not shown), is throttled by the air nozzle 6 to form a high-speed air flow, and this high-speed air flow is jetted into the pulverization chamber 8. Here, the angle of the air nozzle 6 disposed to be inclined to the outer wall 4 is 10 to 50 degrees with respect to the tangent to the annular outer wall 4 (80 to 40 degrees with respect to the center line), more preferably 20 to 40 degrees. (70 to 50 degrees with respect to the center line).

Conventionally, in the case of a jet mill main body of this size, normally 6 to 8 air nozzles 6 are arranged at equal intervals on the annular outer wall 4, but in the jet mill according to the present embodiment, Based on the defining method as described above, two air nozzles 6 are arranged at equal intervals on the annular outer wall 4 with respect to the effective diameter φ200 mm of the jet mill.
Here, the method of determining the number of the air nozzles 6 is determined according to the above-described equation (1) from the conditions of 200 / 100-1 = 1, 200/100 + 2 = 4, and 2 ≦ n, where n = 2-4. Here, the smallest even value 2 is determined.

  Similar to the air nozzle 6, the material to be crushed is supplied from a supply port 14 that is inclined at substantially the same angle with respect to the outer wall 4 of the jet mill body 2. In this embodiment, as shown in detail in FIG. 3, the supply port 14 includes a funnel 16 for supplying the material to be crushed and a supply nozzle 18 for supplying air for supplying the material to be crushed to the pulverization chamber 8. , And a diffuser 20 that mixes the material to be crushed supplied from the funnel 16 and the air supplied from the supply nozzle 18 and supplies the mixture to the inside of the pulverization chamber 8. An appropriate amount of the material to be crushed is supplied to the funnel 16.

  The material to be crushed supplied to the funnel 16 is supplied to the inside of the pulverizing chamber 8 through the diffuser 20 by a high-speed air flow blown from the supply nozzle 18. The object to be crushed supplied to the inside of the pulverization chamber 8 is mainly pulverized by a high-speed air flow ejected from the air nozzle 6 and supplied from the air nozzle 6 and the air stream ejected together with the object to be crushed from the diffuser 20. The inside of the crushing chamber 8 is swung at a high speed by the air flow, and the objects to be crushed collide with each other or the inner wall surface of the crushing chamber 8 to be pulverized into fine powder.

  In the jet mill according to the present embodiment, the upper surface and the lower surface of the crushing chamber 8 formed as a donut-shaped cavity inside the jet mill main body 2 are arranged at a predetermined interval. An outlet ring channel 30 is disposed inside (center). Here, the outlet ring channel 30 has a diameter approximately the same as the diameter of the lower end of the outlet pipe 32 (circular pipe) 32 disposed at the center of the upper plate 10 of the crushing chamber 8 and the lower end of the outlet pipe 32. And a disc 34 disposed in the center of the lower plate 12 of the crushing chamber 8. That is, the lower end of the protruding portion 32a of the outlet pipe 32 and the upper surface of the disc 34 are arranged at a predetermined interval, so that the exit ring is defined by the space between the lower end of the protruding portion 32a and the upper surface of the circular plate 34. A channel 30 is formed.

  Here, the protrusion 32a at the lower end of the outlet pipe 32 disposed in the center of the upper plate 10 forming the crushing chamber 8 is configured such that the protruding amount of the protrusion 32a into the crushing chamber 8 is variably configured. It is also possible to adjust the opening width of the ring channel 30. A specific example will be described with reference to FIG. That is, the upper casing of the jet mill body 2 is composed of a ring-shaped upper plate 10 and a support block 11 that is attached to the upper plate 10 and supports the outlet pipe 32 so as to be movable up and down. By forming a female threaded portion 11a in the support block 11 to be engaged with a height adjusting screw 32b formed on the surface, the outlet pipe 32 is rotated to adjust the height provided on the outer peripheral surface thereof. The outlet pipe 32 is moved up and down by moving it forward or backward with respect to the female thread portion 11a of the support block 11 that is screwed with the screw 32b, and the protrusion 32a at the lower end of the outlet pipe 32 moves into the grinding chamber 8. It is possible to adjust the opening width (interval) of the outlet ring channel 30 by adjusting the protruding amount (from the lower inner wall surface or lower end portion of the support block 11) to an arbitrary amount. .

  The outlet ring channel 30 is formed by a protruding portion 32 a of a pipe 32 protruding from the upper plate 10 of the crushing chamber 8 toward the crushing chamber 8 and a disc 34 fixed to the center of the lower plate 12 of the crushing chamber 8. For example, instead of the circular plate 34, as shown in FIGS. 4 (a) and 4 (b), a short circular tubular protrusion provided at the center of the lower plate 12 of the crushing chamber 8 is used. A member having an arbitrary shape such as a (short circular tube) 35 can be used.

  Since the jet mill according to the present embodiment is configured as described above, the object to be crushed is supplied to the pulverization zone 26 outside the pulverization chamber 8 and is pulverized mainly by a high-speed air flow ejected from the air nozzle 6. Further, due to the air flow supplied from the supply nozzle 18 and ejected together with the material to be crushed from the diffuser 20 and the air flow supplied from the air nozzle 6, the material to be crushed swirls in the pulverization chamber 8 at a high speed. Or it collides with the wall surface inside the crushing chamber 8 and is crushed into fine powder.

  The fine powder pulverized to a predetermined particle size floats on the air flow swirling inside the crushing chamber 8, and at this time, the coarsely pulverized object has a large centrifugal force generated by the swirling air flow. Therefore, only the fine powder which stays in the vicinity of the outer peripheral portion of the crushing chamber 8 and is pulverized to a predetermined particle size or less passes through the outlet ring channel 30 and is discharged to the outside together with the air flow discharged from the outlet pipe 32 to the outside, and becomes a fine powder product. To be recovered.

  Although the basic operation of the jet mill according to the present embodiment is as described above, the following comparative experiment was performed for comparison with the conventional jet mill. Here, the jet mill used in the experiment has an inner diameter (the above-mentioned pitch circle diameter) of the crushing chamber 8 of φ200 mm and has a cross-sectional shape shown in FIG. 3, and as shown in FIG. The two air nozzles 6 were arranged at symmetrical positions, and the material to be crushed was supplied from the supply port 14 arranged at an intermediate position between them.

  In addition, as a conventional type jet mill for comparison, the basic configuration is the same as that of the jet mill according to the present embodiment, but the number of the air nozzles 6 and the arrangement state thereof are different. That is, as shown in FIG. 5, six air nozzles 6 were arranged on the outer wall 4, and the material to be crushed was supplied from the supply port 14.

[Example 1 and Comparative Example 1]
Using the two types of jet mills described above, the polyester nonmagnetic toner having an average diameter of 500 μm was pulverized, and the particle size and particle size distribution of the pulverized product were measured. Here, the discharge port diameter of the two air nozzles 6 used in the jet mill according to the present embodiment is φ2.2 mm, and the discharge port diameter of the six air nozzles 6 used in the conventional jet mill is φ1.3 mm. This dimension is determined so that the discharge area of the entire air nozzle is substantially equal.

That is, the total discharge area of the air nozzles 6 (two) in the jet mill according to this embodiment is (2.2) ² × (π / 4) × 2≈7.60 (mm ² ).
The total discharge area of the air nozzles 6 (six) in the case of a conventional type jet mill is (1.3) ² × (π / 4) × 6≈7.96 (mm ² )
Therefore, the difference is a little less than 5%, and it is considered that the difference can withstand the comparison.

Here, the amount of air sent to the entire discharge area of the air nozzle 6 is 0.7 m ³ / min, and the supply amount of the object to be crushed (raw material) is 800 g / h. The result of the pulverization experiment performed under these conditions is as shown in FIG.

As shown in FIG. 6, in the case of the jet mill according to the present embodiment (represented by the mark ●) and the conventional type (six nozzles) jet mill (represented by the mark ◇). The particle size of the pulverized product is clearly different.
The reason why this phenomenon occurs is that when the total air volume is made substantially the same, in the case of the jet mill according to this embodiment (two nozzles), the flow velocity of the supplied air in the pulverization chamber is large. It is also possible that the

  As described above, according to the jet mill according to the present embodiment, the average particle diameter of the object to be crushed is changed to the jet mill using substantially the same apparatus, even under the same condition that the total air volume is substantially equal. Or, it is possible to provide a new function such as changing the particle size distribution width.

  Next, as disclosed in the above-mentioned prior application of the present applicant (see Japanese Patent Application Laid-Open No. 2005-131633), an improvement having a narrow path that divides the pulverization zone and the classification zone in the cavity of the jet mill body An example based on the configuration described above is shown.

  7 is a plan sectional view conceptually showing a jet mill according to a second embodiment of the present invention, FIG. 8 is a side sectional view of the jet mill shown in FIG. 7, and FIG. It is a sectional side view which shows one Embodiment of a specific structure. The jet mill shown here has an inner diameter (specifically, a pitch circle diameter connecting the tips of the air nozzles) of φ500 mm.

The jet mill shown in FIGS. 7 to 9 is an improvement of the jet mill according to the first embodiment shown in FIGS. 1 to 3 and has a radius of the crushing chamber 8 formed as a ring donut-shaped cavity. Classifying rings 22 and 24, which are ring-shaped barriers formed inside the crushing chamber 8, are arranged at positions approximately in the middle of the width in the direction. The crushing chamber 8 has an outer ring (ring donut) shape. It is divided into a pulverization zone 26 and an inner ring (ring donut) classification zone 28.
The gap between the classifying rings 22 and 24 forms a classifying ring channel 23 serving as a first narrow path characteristic of the jet mill according to the present embodiment. It communicates with the zone 28.

  The classifying rings 22 and 24 as ring-shaped barriers have a predetermined interval (opening width of the classifying ring channel 23) between the upper surface and the lower surface of the crushing chamber 8 formed as a cavity inside the jet mill body 2. The upper classifying ring 22 is disposed on the upper plate 10 of the jet mill body 2 and the lower classifying ring 24 having the same diameter and substantially symmetrical with the lower plate 12 of the jet mill main body 2 is predetermined. The ring-shaped barrier is divided and communicated with the outer pulverization zone 26 and the inner classification zone 28.

That is, the classification ring channel 23 that becomes a narrow path of the jet mill according to the present embodiment is constituted by a space between the upper and lower classification rings 22 and 24 that become ring-shaped barriers, and is divided by the classification rings 22 and 24. The crushing zone 26 and the classification zone 28 are communicated with each other.
In the present embodiment, as the classification rings 22 and 24, those having various intervals (opening width of the classification ring channel 23) are prepared and arranged in the crushing chamber 8 of the jet mill body 2. By exchanging the classification rings 22 and 24 to be performed, the interval between the classification rings 22 and 24 (opening width of the classification ring channel 23) can be easily adjusted to an appropriate interval according to the object to be crushed.

As shown in FIGS. 8 and 9, the wall surfaces of the classification rings 22 and 24 arranged in the pulverization chamber 8 on the pulverization zone 26 side are surely returned to the pulverization zone 26 so that the object to be crushed is returned to the pulverization zone 26. It is preferable that the corners have a shape configured with a convex curve toward the center of the jet mill body 2 or a surface inclined toward the center of the jet mill body 2.
Further, as shown in FIGS. 8 and 9, the wall of the classification rings 22 and 24 on the classification zone 28 side is such that the crushed material that has passed through the classification ring channel 23 between the classification rings 22 and 24 enters the classification zone 28. It is preferable that the corners have a shape configured with a convex curve toward the center of the jet mill main body 2 or a surface inclined toward the center of the jet mill main body 2 so as to flow smoothly.

  Also in the jet mill according to the present embodiment, the upper surface and the lower surface of the crushing chamber 8 formed as a donut-shaped cavity inside the jet mill main body 2 are arranged at a predetermined interval. The exit ring channel 30 is arranged inside (center part) of. Here, the outlet ring channel 30 has a diameter substantially the same as the diameter of the lower end of the outlet pipe 32 (circular pipe) 32 disposed at the center of the upper plate 10 of the crushing chamber 8 and the lower end of the outlet pipe 32. Thus, it is constituted by a disc 34 disposed in the center of the lower plate 12 of the grinding chamber 8. That is, the lower end of the protruding portion 32a of the outlet pipe 32 and the upper surface of the disc 34 are arranged at a predetermined interval, so that the exit ring is defined by the space between the lower end of the protruding portion 32a and the upper surface of the circular plate 34. A channel 30 is formed.

The protrusion 32a at the lower end of the outlet pipe 32 disposed in the center of the upper plate 10 forming the crushing chamber 8 is also configured so that the protruding amount of the protrusion 32a into the crushing chamber 8 is variable as described above. Thus, the opening width of the outlet ring channel 30 can be adjusted.
As described above, the outlet ring channel 30 is also a short circular tube provided in the center of the lower plate 12 of the crushing chamber 8 as shown in FIGS. 4A and 4B instead of the circular plate 34. It is possible to use a member having an arbitrary shape such as a projection (short circular tube) 35.

  Since the jet mill according to the present embodiment is configured as described above, the object to be crushed is supplied to the pulverization zone 26 outside the pulverization chamber 8 and pulverized by a high-speed air stream ejected from the air nozzle 6. The air to be crushed by the air flow supplied from the supply nozzle 18 together with the material to be crushed from the diffuser 20 and the air flow supplied from the air nozzle 6 swirls in the pulverization zone 26 of the pulverization chamber 8 at high speed. They collide with each other or the wall surface inside the grinding zone 26 and are crushed into fine powder.

  Then, the fine powder pulverized to a predetermined particle size floats on an air flow swirling inside the pulverization chamber 8, and passes through the classification ring channel 23 which is a space between the classification rings 22 and 24 from the pulverization zone 26. The air flows through the air and flows into the classification zone 28 of the grinding chamber 8. At this time, the coarsely pulverized object has a large centrifugal force generated by the swirling air flow, so that it remains in the pulverization zone 26, and only fine powder pulverized to a predetermined particle size or less passes through the classification ring channel 23 to the classification zone 28. Flow into. The fine powder of the material to be pulverized which has flowed into the classification zone 28 floats on the air flow rectified from the pulverization zone 26 swirling in the classification zone 28, leaving a coarse pulverized material with mixed particles, It is aligned to a predetermined particle size distribution, passes through the outlet ring channel 30, is discharged to the outside together with the air flow discharged to the outside from the outlet pipe 32, and is recovered as a fine powder product.

In the classification ring channel 23, which is the space between the classification rings 22 and 24, the fine powder particles have centrifugal force (m · Vt ² / r: m is the mass of the particles, and Vt is the tangential velocity of the particles. , R are radii) and air drag (A · dp · Vr: A is a coefficient, dp is the particle size of the particle, Vr is the radial velocity of the particle), and classification is performed. When the distance between the classification rings 22 and 24 is increased, the opening width of the classification ring channel 23, that is, the flow path cross-sectional area is increased, and the velocity (Vr) of air toward the center is decreased. Therefore, the centrifugal force> the air drag, the classification point becomes small, and the particles do not easily pass through the classification ring channel 23. For this reason, the particle size of the fine powder to be pulverized can be controlled by changing the distance between the classification rings 22 and 24 (the opening width of the classification ring channel 23).

  Further, in the present invention, by providing the classification ring channel 23 by the classification rings 22 and 24, the fine powder having the target particle size can be efficiently discharged from the pulverization zone 26, so that overpulverization is suppressed and the object is achieved. Generation of fine powder smaller than the particle size can be reduced. In addition, since uniform streamlines can be formed in both the pulverization zone 26 and the classification zone 28, it is possible to suppress the jumping of coarse particles to the fine powder product side, so that a sharp particle size distribution can be obtained. Can do.

  Furthermore, the fine powder discharged to the outside from the outlet pipe 32 together with the air flow is a fine powder having a particle size of micron order, and is collected by a collecting device such as a cyclone or a bag filter (not shown). Fine powder is obtained as a product that is finely pulverized, classified with high accuracy, and has a uniform particle size distribution.

  In the classification zone 28, the particles that have entered this region are swirled in the classification zone 28 many times, so that the particles that are closer to fine particles go out of the apparatus together with the air current, and are close to coarse particles. The particles operate to move back and forth between the classification zone 28 and the grinding zone 26, and are crushed each time they enter the grinding zone 26. Thereby, the effect of multistage pulverization classification is obtained, and classification with higher accuracy is performed.

By the way, conventionally, in the case of a jet mill main body of this size, normally, 8 to 16 air nozzles 6 are arranged on the annular outer wall 4 at equal intervals. In FIG. 4, four air nozzles 6 are arranged on the annular outer wall 4 at equal intervals with respect to the effective diameter φ500 mm of the jet mill based on the defining method as described above.
Here, the determination method of the number of the air nozzles 6 is determined according to the above-described equation (1) from the condition that 500 / 100-1 = 4, 500/100 + 2 = 7, and 2 ≦ n, n = 4 to 7 Here, the smallest even value 4 of them is determined.

[Example 2 and Comparative Example 2]
Although the basic operation of the jet mill according to the present embodiment is as described above, the following comparative experiment was performed in order to reduce the number of air nozzles 6 of the jet mill. The jet mill used in the experiment here has an inner diameter (the aforementioned pitch circle diameter) of the crushing chamber 8 of φ500 mm, has a cross-sectional shape shown in FIG. 7, and has three, four, and seven on the outer wall 4. The 14 and 14 air nozzles 6 were arranged at equal intervals, and the material to be crushed was supplied from the supply port 14 arranged at one place between them.
Of these, the one having 14 air nozzles 6 corresponds to a conventional jet mill, and the other three types correspond to experiments for reducing the number of air nozzles 6.

Here, the total discharge area of the air nozzle 6 in each jet mill is:
In case of 3 nozzles with nozzle diameter of 2.8mm,
(2.8) ² × (π / 4) × 3≈18.47 (mm ² )
In case of 4 nozzles with nozzle diameter of 2.4mm,
(2.4) ² × (π / 4) × 4≈18.10 (mm ² )
In case of 7: Nozzle diameter φ1.8mm,
(1.8) ² × (π / 4) × 7≈17.81 (mm ² )
In the case of a conventional jet mill (nozzle diameter φ1.3mm x 14)
(1.3) ² × (π / 4) × 14≈18.58 (mm ² )
The difference is a little less than 4%, and it is considered that the comparison can withstand the comparison.

  Using the above four types of jet mills, polyester-based non-magnetic color toner having an average diameter of 500 μm was pulverized, and the particle size of the pulverized product was measured by changing the mixing ratio (particle mass / air supply amount). The results are shown in FIG.

As shown in FIG. 10, the pulverization result (particle size of the pulverized product) in the jet mill in which the three, four, seven, and fourteen air nozzles 6 used in the above experiment are arranged at equal intervals is clearly shown. The difference is seen.
That is, at the stage where the number of air nozzles 6 is reduced from 14 to 7, the median diameter (so-called D ₅₀ ) has dropped dramatically. This tendency is substantially the same when the number of air nozzles 6 is four, but when the number of air nozzles 6 is further reduced (three), the effect tends to decrease.

  The reason why this phenomenon occurs is that, in the same way as in the previous experiment, the flow rate of the supplied air in the grinding chamber is increased in order to make the total air volume substantially the same. Conceivable.

  As described above, according to the jet mill according to the present embodiment, the average particle diameter of the object to be crushed is changed to the jet mill using substantially the same apparatus, even under the same condition that the total air volume is substantially equal. Alternatively, it is possible to provide a new function such as changing the particle size distribution width.

  The above-described embodiments and examples are merely examples of the present invention, and the present invention is not limited to these, and appropriate modifications or improvements can be made without departing from the spirit of the present invention. Needless to say, it may be performed.

  For example, as shown in Table 1, according to the present invention, the number of nozzles can be arranged with a significantly reduced number compared to the number of conventional nozzles arranged. In general, the number of arrangements is “particularly preferable”, but it is not necessarily limited thereto. Moreover, it is not necessary to limit to an even number.

1 is a plan sectional view conceptually showing the structure of a jet mill according to an embodiment of the present invention. It is a sectional side view of the jet mill shown in FIG. It is a sectional side view which shows the detailed example of the specific structure of the jet mill shown in FIG. It is a figure which shows the principal part of another structural example of the structural member of the exit ring channel used for the jet mill shown in FIGS. 1-3, and has shown the detail of the part enclosed with the circle A in FIG. Is a cross-sectional view, and (b) is a perspective view. It is a plane sectional view which shows notionally the composition of the conventional type jet mill shown for comparison. It is a graph which shows the crushing experiment result by the jet mill which concerns on 1st Embodiment, and the conventional type jet mill. It is a plane sectional view which shows notionally the composition of the jet mill concerning other embodiments of the present invention. It is a sectional side view of the jet mill shown in FIG. It is a sectional side view which shows the detailed example of the specific structure of the jet mill shown in FIG. It is a graph which shows the crushing experiment result by the jet mill which concerns on 2nd Embodiment, and the conventional type jet mill.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Jet mill main body 4 Outer wall 6 Air nozzle 8 Crushing chamber 10 Upper board 11 Support block 11a Female thread part 12 Lower board 14 Supply port 16 Funnel 18 Supply nozzle 20 Diffuser 22, 24 Classification ring 23 Classification ring channel (1st narrow channel)
26 Grinding zone 28 Classification zone 30 Exit ring channel (second narrow path)
32 Outlet pipe 32a Protruding part 32b Outlet pipe height adjusting screw 34 Disc 35 Short pipe

Claims (11)

A jet mill body in which a disk-shaped cavity is formed;
A plurality of air nozzles disposed on the ring-shaped outer wall of the jet mill body so as to be inclined with respect to the center of the disk-shaped cavity, and generating a high-speed air flow in the disk-shaped cavity;
A jet mill having an outlet disposed substantially in the center of the disk-shaped cavity of the jet mill body,
The disk-shaped cavity forms a ring-shaped pulverization zone for pulverizing an object to be pulverized by the high-speed air flow supplied from the plurality of air nozzles,
When the effective diameter of the jet mill main body is φN (mm), the number n (lines) of the plurality of air nozzles is represented by the following formula (1).
[(N / 100) -1] ≦ n ≦ [(N / 100) +2] (1)
Here, [a] represents the maximum integer value of a or less, and n is an integer of 2 or more. The jet mill according to claim 1,
In addition to the above-described configuration, a ring-shaped classification zone that is disposed inside the pulverization zone and communicates with the exit space and is positioned inside the pulverization zone, and classifies objects to be pulverized by the air flow;
A jet mill that is disposed between the pulverization zone and the classification zone and has a ring-shaped first narrow path that divides and communicates with the pulverization zone and the classification zone. The jet mill main body includes a substantially disc-shaped upper casing and a lower casing, and the ring-shaped outer wall interposed between the upper casing and the lower casing,
3. The jet mill according to claim 1, wherein the disk-shaped cavity is an internal space formed between the upper casing and the lower casing and inside the ring-shaped outer wall.   4. The jet mill according to claim 1, wherein the ring-shaped first narrow path is formed at a predetermined interval between an upper surface and a lower surface of the disk-shaped cavity.   The ring-shaped first narrow path is formed by ring-shaped barriers that are respectively attached to the upper and lower surfaces of the cavity substantially parallel to each other at a predetermined interval at a predetermined radial position of the disk-shaped cavity. The jet mill according to any one of claims 1 to 4, which is a ring-shaped channel to be formed. The ring-shaped grinding zone is an internal space in which the upper surface and the lower surface of the disk-shaped cavity are asymptotic to each other toward the center, and the cavity is narrowed toward the center direction,
The ring-shaped first narrow narrow path is formed between protrusions on the upper surface and the lower surface of the cavity respectively arranged at predetermined intervals at predetermined positions in the radial direction of the disk-shaped cavity. The jet mill according to claim 1, wherein the jet mill is a ring-shaped channel. The jet mill according to any one of claims 1 to 6,
Furthermore, it is arranged between the classification zone and the outlet disposed inside thereof, and has a ring-shaped second narrow narrow path that divides and communicates with the classification zone and the outlet space. Jet mill.   The jet mill according to claim 7, wherein the ring-shaped second narrow path is formed at a predetermined interval between an upper surface and a lower surface of the disk-shaped cavity. The outlet is formed by a cylindrical outlet pipe disposed upward or downward at a substantially central portion of the disc-shaped cavity of the jet mill body,
The ring-shaped second narrow narrow path is disposed at a predetermined distance from the lower end or upper end protrusion of the outlet pipe, and on the upper side or the lower side of the lower surface of the substantially central portion of the cavity. The jet mill according to claim 7 or 8, wherein the jet mill is a ring-shaped channel formed between the arranged circular plate or short tube-shaped protrusions. The outlet pipe is movable in the vertical direction with respect to the jet mill body;
The interval between the ring-shaped second narrow passages is such that the outlet pipe is moved in the vertical direction so that the protruding part at the lower end or the upper end of the outlet pipe is brought closer to the protruding part of the disc or short tube shape The jet mill according to claim 9, wherein the jet mill is adjusted by moving away. The outlet is formed by a cylindrical outlet pipe disposed upward or downward at a substantially central portion of the disc-shaped cavity of the jet mill body,
The ring-shaped second narrow narrow path is disposed at a predetermined distance from the lower end or upper end protrusion of the outlet pipe, and on the upper side or the lower side of the lower surface of the substantially central portion of the cavity. The jet mill according to any one of claims 8 to 10, which is a ring-shaped channel formed between the provided ring-shaped convex portions.

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