JP5474363B2 - Horizontal swirl type jet mill - Google Patents

Description

  The present invention relates to a jet mill in which powder is entrained in a fluid ejected from a nozzle at high pressure and pulverized by collision between particles. More specifically, a horizontal swirl that can suppress coarse particles caused by the phenomenon of jumping in and can obtain a pulverized product having a very narrow particle size distribution that contains almost no ultrafine particles even when pulverized to a size of several μm. The present invention relates to a flow type jet mill.

  A jet mill is well known as a type that pulverizes coarse pulverized material with a high-speed air flow supplied into the pulverization chamber from a nozzle arranged on the outer wall and classifies the pulverized material with a swirling air flow. (For example, Patent Document 1). This jet mill has a simple structure inside the crushing chamber, and the upper and lower surfaces of the crushing chamber can be easily disassembled and assembled, and cleaning after use is easy. However, since the pulverized material is pulverized only by the air flow inside the pulverization chamber, it is difficult to control the pulverized material to a predetermined particle size or to control the variation in the particle size of the pulverized material. For this reason, various improvements have been made to make the pulverized material a predetermined particle size and to reduce variations.

  For example, in Patent Document 2, the discharge part is protruded from one of the upper and lower wall parts defining the hollow chamber and extends toward the other wall so as to cross the hollow chamber in the vertical direction, and A cylindrical portion disposed in a recess provided on the other wall and projecting out of the cavity chamber, and having a discharge auxiliary path and a secondary classification gap, the pulverized material from the classification zone and the discharge auxiliary path; A jet mill is disclosed that is adapted to enter the cylindrical portion through a secondary classification gap.

  In Patent Document 3, a disk-shaped cavity formed inside a mill body is divided into a ring-shaped pulverization zone for pulverizing an object to be pulverized by a high-speed air flow supplied from a plurality of air nozzles, and an inside of the pulverization zone. Divided into a ring-shaped classification zone that is arranged, communicates with the exit space, is located inside the grinding zone, and classifies the object to be crushed by the air flow, and divides both between the grinding zone and the classification zone And a ring-shaped first narrow narrow passage that communicates and divides the classification zone and the outlet space between the classification zone and the outlet inside thereof, and communicates with the ring-shaped second narrow narrow passage A jet mill is disclosed.

  Patent Document 4 and Patent Document 5 include a center pole disposed at the center of the lower surface of the swirl crushing chamber, and the apex of the center pole and the lower end surface of the outlet are on the center line in the height direction of the swirl crushing chamber. There is disclosed a jet mill having a configuration as described below. With such a configuration, the classification zone and the pulverization zone in the swirl crushing chamber can be clearly separated, and fine particles having a predetermined size and a narrow particle size distribution are discharged from the outlet at the top of the swirl crushing chamber. At the same time, it teaches that the coarse particles are blown to the outer periphery by the centrifugal force generated by the high-speed jet flow, and have the effect of improving the collision dependency between the raw materials in the high-speed jet flow.

JP 52-44450 A JP 2007-196147 A JP 2005-131633 A JP 2000-42441 A JP 2007-275849 A

  In these conventional jet mills, for example, the high-pressure swirling flow for pulverization / classification is disturbed by the air flow for supplying the raw material, and the powder of the raw material flows into the classification zone without being pulverized, together with the pulverized product. It is difficult to completely eliminate the so-called jumping phenomenon that is discharged, and the ratio of coarse particles increases from such jumping phenomenon. In these jet mills, it is difficult to pulverize relatively soft pulverizers such as resins and solid organic compounds to a size of several μm. Even if they can be pulverized to a size of several μm, ultrafine particles ( 0.45 μm or less) and the particle size distribution becomes wide.

  The present invention is a horizontal swirling flow that can suppress a coarse particle due to a jumping phenomenon and can obtain a pulverized product having a very narrow particle size distribution that contains almost no ultrafine particles even when pulverized to a size of several μm. It aims to provide a jet mill of the type.

  As a result of intensive studies to achieve the above object, the present inventor has found that a mill main body having a substantially disk-shaped cavity, a supply pipe for introducing the crushed material into the cavity, and for removing the crushed material from the cavity. A discharge cylinder and injection means for generating a swirling flow by injecting fluid into the cavity, and the discharge cylinder is located at the upper center of the lower wall of the mill main body that defines the upper and lower sides of the cavity. Is protruded vertically with a gap between the upper wall of the mill body partitioning the upper and lower sides of the cavity, and the upper end of the cylinder is closed with an orifice-shaped plate having a narrow hole, and The inventors have invented a horizontal swirl type jet mill in which the crushed material is discharged from the narrowed hole through the lumen of the cylinder to the outside.

  In the horizontal swirling jet mill of the present invention, the crushed material injected and introduced from the supply pipe is obtained by closing the upper end of the discharge cylinder provided vertically at the approximate center of the mill body with an orifice-shaped plate having a narrowed hole. It is possible to substantially eliminate the phenomenon of jumping into the opening at the upper end of the discharge cylinder without being pulverized and being discharged together with the pulverized material. In addition, since the finely pulverized fine particles hardly return to the pulverization zone, even if the fine particles are pulverized to an average particle size of several μm, very few fine particles are generated. The horizontal swirling flow jet mill of the present invention has greatly improved classification accuracy and can simplify quality control.

  Further, a substantially annular space is defined from the cavity by the mill main body and the discharge cylinder, and a zone for mainly pulverizing the pulverized material and a zone for mainly classifying the crushed material are formed in the space. Then, the coarse particles are returned from the classification zone to the pulverization zone, and the particle size distribution can be narrowed. Furthermore, those equipped with injection means consisting of a high-pressure gas chamber and a Laval nozzle have very high pulverization efficiency, and the ratio of coarse particles transferred from the pulverization zone to the classification zone is reduced. Therefore, both the classification speed and accuracy are likely to increase. .

  When the head loss of the supply pipe is larger than the head loss of the discharge tube, the backflow of the crushed material to the supply pipe is prevented, and the crushed material can be efficiently supplied into the cavity. And, by providing the outlet of the supply pipe in a cavity off the upper side of the discharge cylinder, an undisturbed swirling flow is generated above the orifice-shaped plate, and both the classification speed and accuracy are likely to be high, and the jumping phenomenon It becomes possible to efficiently supply the pulverized material into the cavity while reducing the amount of slag.

  Preferred embodiments of the present invention will be described with reference to the drawings to describe the present invention in more detail. Note that the present invention is not limited to these embodiments, and includes modifications, modifications, or additions that do not depart from the spirit and scope of the present invention.

Embodiment 1
2 is a perspective view showing an example of a jet mill according to Embodiment 1 of the present invention (in a state where the upper wall of the mill body is opened), and FIG. 3 is a cross-sectional view of the jet mill shown in FIG. 4 is a longitudinal sectional view of the jet mill shown in FIG. 2 (viewed in the Y direction).

(Construction)
The horizontal swirl type jet mill of the present invention shown in FIG. 2 includes a mill body 1 having a substantially disc-shaped main cavity a, a supply pipe 30 for introducing crushed material into the main cavity a, and the main cavity. a discharge cylinder 2 for taking out the crushed material from a, and an injection means for injecting a fluid into the main cavity a to generate a swirling flow.
The mill body of the jet mill shown in FIG. 2 has a shape in which both ends of a short double cylinder are respectively closed by round tray plates (upper wall 10 and lower wall 11).

  A sub-cavity b (high pressure gas chamber) is formed between the inner cylinder 12 and the outer cylinder 13 of the double cylinder, and a main cavity a (pulverization / classification chamber) is formed inside the inner cylinder 12. The main cavity a has a substantially disc shape, and the sub-cavity b has a substantially annular shape. The mill body in FIG. 2 has an annular sub-cavity b as a high-pressure gas chamber. However, the high-pressure gas chamber is provided separately from the mill body, and a gas pipe is drawn from the separate high-pressure gas chamber to A gas pipe can be directly connected to the side wall (inner cylinder), and the subcavity chamber can be omitted.

The upper wall 10 of the mill body only needs to have a structure that does not disturb the swirling flow above the discharge cylinder, which will be described later, and may be a round tray plate as shown in FIG. The part corresponding to the upper part of the discharge cylinder as shown in FIG.
A through-hole 6 is provided in the lower wall of the mill body so that a discharge cylinder, which will be described later, can pass therethrough. The clearance between the discharge tube 2 and the lower wall 11 passed through the through hole 6 is sealed so that the swirling flow does not leak to the outside.

The discharge cylinder 2 is provided vertically through the lower wall substantially at the center of the lower wall 11 of the mill body that defines the upper and lower sides of the main cavity.
The discharge cylinder divides the main cavity a of the mill main body into a substantially annular space between the discharge cylinder 2 and the mill main body inner cylinder 12 and a space (a lumen) inside the discharge cylinder. That is, the horizontal swirling flow type jet mill shown in FIG. 4 forms a triple cylinder by the mill body and the discharge cylinder.

  A gap is maintained between the upper end of the discharge cylinder and the upper wall 10 of the mill body that defines the upper and lower sides of the main cavity. The distance between the upper end of the discharge cylinder and the upper wall of the mill body is not particularly limited, but the upper end of the discharge cylinder 2 is preferably not extremely lower than the height of the nozzle 40 of the injection means. Moreover, when the space | interval of the upper end of a discharge cylinder and the upper wall of a mill main body becomes too short, a crushed material may be clogged in this clearance gap and classification may become difficult. Therefore, for example, in the case where the upper wall and the lower wall are round tray-shaped plates as shown in FIG. 4, the nozzle 40 of the injection means has a distance h ′ from the lower wall of the mill body and a distance from the lower wall to the upper wall. When the ratio h ′ / H with respect to H is 0.5 (the same distance from the upper wall and the lower wall), the upper end of the discharge cylinder is the distance h from the lower wall of the mill body and the lower wall to the upper wall. The ratio h / H with respect to the distance H is preferably not less than 0.45, and preferably not more than 0.95 in consideration of clogging. In other words, the discharge cylinder preferably has a ratio h / H of 0.45 to 0.95 of the distance h from the lower wall of the mill body to the upper end of the discharge cylinder and the distance H from the lower wall to the upper wall.

The upper end of the discharge cylinder is closed by an orifice-shaped plate 5 having a narrowed hole 51 so that the crushed material is discharged from the narrowed hole to the outside through the internal space of the cylinder.
And by the gas ejected from the injection means, in the substantially annular space between the discharge cylinder 2 and the mill main body inner cylinder 12, the zone for mainly pulverizing the crushed material and the classification of the crushed material are mainly performed. A zone is formed. A swirling flow is also generated above the orifice plate, and this swirl flow causes fine particles to enter the lumen of the discharge cylinder through a narrow hole in the center of the orifice plate, and coarse particles to the outside of the outer periphery of the orifice plate. It will start. The coarse particles that are ejected are pulverized again in the crushing zone to become fine particles and return to the classification zone.

The orifice-shaped plate 5 is not particularly limited in its thickness, material, and shape as long as it has a narrow hole 51 in the center. The illustrated orifice plate has a narrow hole in the center of a flat disk, but is not limited to this. For example, the outer periphery of the plate is slightly curved upward or downward. Also good. The curved plate may be attached to the upper end of the discharge cylinder so as to be convex (umbrella shape) or may be attached to be convex downward (funnel shape).
The size (diameter) of the constriction hole with respect to the diameter of the orifice plate (that is, the lumen diameter of the discharge cylinder) can be appropriately selected in consideration of the balance between the classification accuracy and the discharge amount. For example, the ratio of the size (diameter) of the narrowed hole to the diameter of the orifice plate (ie, the lumen diameter of the discharge tube) is preferably 0.3 to 0.85, and the diameter of the orifice plate (ie, the discharge tube) The difference between the lumen diameter) and the size (diameter) of the stricture hole can be preferably 30 mm to 105 mm.

  The raw material supply means includes a supply pipe 30 connected to the upper wall portion 10 or the inner wall 12 at a predetermined position and angle, a hopper 31 connected to the supply pipe 30, a nozzle 32, and the like. . When the crushed material enters the supply pipe 30 from the hopper 31, the crushed material is jetted and supplied to the pulverization zone of the main cavity chamber a together with the high-pressure fluid pumped from the nozzle 32. In addition, the raw material supply means 3 includes, for example, a Laval nozzle configuration in which a high-pressure fluid supply pipe and an acceleration pipe are combined, or a configuration provided at a plurality of locations depending on the physical properties and supply amount of the raw material powder.

  The head loss of the supply pipe is preferably designed to be larger than the head loss of the discharge tube. By designing in such a head loss relationship, it is possible to prevent back flow of the crushed material to the supply pipe. Further, the outlet of the supply pipe is preferably provided in a cavity that is removed from above the discharge cylinder.

  The injection means 4 includes a sub-cavity b, an air supply pipe 41 that introduces high-pressure fluid from the outside into the sub-cavity b, and an inner cylinder 12 that injects the high-pressure fluid in the sub-cavity b into the main cavity a. And a nozzle 40 that performs the above operation. The nozzles 40 are respectively attached to portions equally divided with respect to the outer peripheral surface of the inner cylinder 12 and are provided in a state inclined at a predetermined angle with respect to the diameter direction of the inner cylinder 12.

  The injection nozzle 40 is preferably a Laval nozzle. The Laval nozzle is a nozzle having a shape in which a cross-sectional area contracts and expands. In the convergent part, which is the entrance of the nozzle, the gas is subsonic, but in the throat part where the cross-sectional area is small, the pressure drops slightly and the gas flow becomes sonic. In the divergent part where the nozzle spreads, the pressure further decreases and the gas flow is released at supersonic speed. By using a Laval nozzle, gas can be injected at a higher speed.

  When the high-pressure fluid is injected from the nozzle 40, the injection means 4 forms a pulverization zone on the peripheral side away from the center and forms a classification zone on the central side in the main cavity chamber a by the swirling flow caused by the injection. For example, the subcavity b may be omitted and the high pressure fluid may be directly supplied to each nozzle 40. In the pulverization zone, the crushed materials are accelerated and collide with each other or collide with the surrounding wall surface, and are pulverized. In this case, as shown in Japanese Patent No. 3087201, the pulverization zone includes an impact plate for promoting pulverization, You may attach a baffle plate. In the classification zone, among the pulverized products pulverized in the pulverization zone, those having reached a predetermined particle size or particle size are transferred from the pulverization zone and classified, and then discharged to the outside through the lumen of the discharge tube.

(Operation)
In the above jet mill, the pulverized material is supplied from the raw material supply means 3 to the main cavity chamber a. Coarse particles of coarse particles are accelerated in a crushing zone formed on the outer peripheral side of the main cavity chamber a among the swirling flows of the high-pressure fluid ejected from the plurality of nozzles 40 and collide with each other, or collide with the inner cylinder 12. It is crushed while colliding. The pulverized fine particles are moved to a classification zone formed on the center side of the main cavity chamber a.
The crushed material, which is further classified above the discharge cylinder by the swirling flow in the classification zone and is reduced to the target size, enters the lumen of the discharge cylinder through the narrowed hole of the orifice plate and is taken out to the outside. . The crushed material that does not reach the target size is returned to the outer peripheral portion (grinding zone) of the main cavity chamber a by the centrifugal force of the swirling flow and pulverized again.
In this jet mill, the orifice plate prevents the coarse particles that have not been pulverized from entering the discharge cylinder, and the pulverization is reliably performed. Further, since the finely pulverized fine particles are not easily returned from the classification zone to the pulverization zone without entering the discharge cylinder, it is possible to prevent the fine particles from becoming finer.

[Embodiment 2]
FIG. 5 is a longitudinal sectional view of the jet mill according to the second embodiment. Since the cross-sectional view and perspective view of the second embodiment are the same as those in FIGS. 3 and 2, they are omitted.
FIG. 5 shows an example in which the upper wall 110 constituting the mill body is hat-shaped. That is, in this mill body, the through hole 107 is formed in the central portion of the upper wall portion 110, and the through hole 107 is closed by a reverse concave outer cylinder member 108. The through hole 107 is a hole having a larger diameter than the through hole 106 of the lower wall portion 111. The outer cylinder member 108 is integrally connected to the upper wall portion 110 by being disposed so as to be coaxial with the through hole 107 and the discharge cylinder 102. In this structure, for example, the classification zone formed between the upper wall portion 110, the discharge cylinder 102, and the orifice plate 105 is expanded by the reverse concave shape of the outer cylinder member 108, and as a result, improvement in classification efficiency is expected. Is done.

[Embodiment 3]
FIG. 6 is a longitudinal sectional view of the jet mill according to the third embodiment. Since the cross-sectional view and perspective view of the third embodiment are the same as those in FIGS. 3 and 2, they are omitted.
FIG. 6 shows a configuration in which the outer cylinder member 208 is further formed in a deep reverse concave shape, the entire length of the discharge cylinder 202 is lengthened, and the elongated cylindrical extension protrudes into the reverse concave shape of the outer cylinder member 208. It has become. That is, the discharge cylinder 202 protrudes from the lower wall portion 211, extends to the upper wall portion 210 side so as to cross the hollow chamber 2 a in the vertical direction, and is connected to the outer cylinder member 208 attached to the upper wall portion 210. It arrange | positions keeping a clearance gap in reverse concave shape. For this reason, among the pulverized products pulverized in the pulverization zone, the pulverized product that has entered the classification zone of the hollow chamber 2a is classified in the classification zone, and then is accurately classified by passing through the gaps. It can be discharged from. In this structure, the pulverized material that has entered the classification zone is classified again with high accuracy (secondary classification) by passing through the gap in addition to the primary classification in the classification zone. Classification accuracy is improved by suppressing variation in particle size or particle size without impairing simplification and compactness.

[Embodiment 4]
FIG. 7 is a transverse sectional view of the jet mill according to the fourth embodiment, and FIG. 8 is a longitudinal sectional view of the jet mill according to the fourth embodiment.
In the fourth embodiment, the sub-cavity b is omitted from the jet mill of FIG. 2, and an annular wall 312 that divides the main cavity 3a (this annular wall corresponds to the inner cylinder 12 of FIG. 2). ), The nozzle device 340 constituting the injection means 304 is respectively provided at a portion equally divided into 12 areas. Each nozzle device 340 is connected to a high-pressure fluid supply unit (not shown) by piping or the like, and jets high-pressure fluid in the same manner as the nozzle 40 in FIG. The orifice-shaped plate may be an umbrella or a dish whose peripheral portion is curved downward or upward.

〔Example〕
The effectiveness of the present invention will be clarified by an example in which pulverization is performed using the jet mill according to Embodiment 1 of the present invention.
The jet mill used in this example has the structure shown in FIGS. In this jet mill, the inner diameter of the main cavity chamber (pulverization chamber) is 646 mm, the height of the outer peripheral portion of the main cavity chamber is 180 mm, the inner diameter of the discharge cylinder is 155 mm, the diameter of the narrow hole of the orifice plate is 75 mm, and the height of the discharge cylinder (Distance from the lower wall of the mill body to the upper end of the discharge cylinder) is 154 mm, the distance between the discharge cylinder and the upper wall of the mill body is 35 mm, 12 injection nozzles, and nozzles for supply means (supply pipe) 1 It has a piece. The pulverization conditions were set at a pulverization pressure of 7 kg / cm ² and an air volume of 16 to 18 m ³ / min. As the pulverizer, Topgin M raw powder (manufactured by Nippon Soda Co., Ltd., having a median diameter of 44 μm) was used.
The particle size distribution of the crushed Topgin M bulk powder was measured with a laser diffraction particle size analyzer SALD-2100 (manufactured by Shimadzu Corporation). The result is shown in FIG.

[Comparative example]
In the comparative example, the jet mill shown in FIG. 1 was used. This jet mill has the same structure as the jet mill shown in FIGS. 2 to 4 except that the upper end of the discharge cylinder is opened to the same size as the inner diameter of the discharge cylinder (not blocked by the orifice plate). Is. Topgin M bulk powder (manufactured by Nippon Soda Co., Ltd., having a median diameter of 44 μm) was pulverized under the same pulverization conditions as in Examples.
The particle size distribution of the crushed Topgin M bulk powder was measured with a laser diffraction particle size analyzer SALD-2100 (manufactured by Shimadzu Corporation). The result is shown in FIG.

As is clear from the comparison between the example and the comparative example, the average particle size is 2 μm when the jet mill of the example in which the upper end of the discharge cylinder of the jet mill is closed with an orifice-like plate having a narrowed hole is pulverized by two passes. However, there are almost no ultrafine particles having a size of 0.45 μm or less, almost no coarse particles exceeding 10 μm, and a very narrow particle size distribution.
On the other hand, the one pulverized by the jet mill of the comparative example not provided with the orifice-shaped plate has an average particle size of about 3.3 μm, but contains not a few ultrafine particles having a size of 0.45 μm or less. In addition, there are many coarse particles exceeding 10 μm, and they have a wide particle size distribution.

  The horizontal swirling jet mill of the present invention can be pulverized to a very fine particle size even if it is a relatively soft resin or solid organic compound. In addition, the product obtained by pulverization contains almost no ultrafine particles or coarse particles and has a very narrow particle size distribution.

Vertical section of a conventional jet mill 1 is a perspective view of a jet mill according to Embodiment 1 (in a state where an upper wall of the mill body is opened). Cross section of the jet mill shown in FIG. Longitudinal section of the jet mill shown in FIG. Vertical sectional view of the jet mill of the second embodiment Vertical sectional view of the jet mill of the third embodiment Cross section of jet mill of embodiment 4 Longitudinal sectional view of the jet mill of the fourth embodiment The figure which shows the particle size distribution of the crushing material grind | pulverized by the jet mill of an Example. The figure which shows the particle size distribution of the crushing material grind | pulverized by the jet mill of the comparative example

1: Mill body (10 and 11 are upper and lower wall parts, 12 and 13 are inner and outer cylinders)
2, 102, 202, 302, 402: Discharge tube 30, 330: Supply pipe 31, 331: Hopper 32: Raw material supply nozzle 40, 140, 240, 340, 440: Injection nozzle 41, 141, 241, 341, 441 : Air supply pipe 5, 105, 205, 305: Orifice plate (51: Stenosis hole)
51, 151, 251 and 351: Narrow hole 6, 106, 206, 306, 406: Lower wall through hole 107, 207: Upper wall through hole 108, 208: Outer cylinder member a, 1a, 2a, 3a, 4a ... main Cavity (grinding / classification room)
b, 1b, 2b, 4b: Sub cavity (high pressure gas chamber)
H: Distance from the lower wall of the mill body to the upper wall of the mill body h: Height of the discharge cylinder (distance from the lower wall of the mill body to the upper end of the discharge cylinder)

Claims (5)

A mill main body having a substantially disk-shaped cavity, a supply pipe for introducing the crushed material into the cavity, a discharge cylinder for taking out the crushed material from the cavity, and a fluid is ejected into the cavity to generate a swirling flow. And injection means for
The discharge cylinder protrudes vertically at the approximate center of the lower wall of the mill body that defines the upper and lower sides of the cavity, with the upper end of the cylinder maintaining a gap between the upper wall of the mill body that defines the upper and lower sides of the cavity. Has been established,
The upper end of the cylinder is closed with an orifice-shaped plate having a narrow hole, and the crushed material is discharged from the narrow hole through the lumen of the cylinder to the outside.
Horizontal swirl type jet mill.   A substantially annular space is defined from the cavity by the mill body and the discharge cylinder, and a zone for mainly pulverizing the crushed material and a zone for mainly classifying the crushed material are formed in the annular space. The horizontal swirling flow jet mill according to claim 1.   The horizontal swirling flow jet mill according to claim 1 or 2, wherein a head loss of the supply pipe is larger than a head loss of the discharge cylinder.   The horizontal swirl type jet mill according to claim 3, wherein an outlet of the supply pipe is provided in a cavity deviated from above the discharge cylinder.   The horizontal swirling flow type jet mill according to any one of claims 1 to 4, wherein the injection means comprises a high-pressure gas chamber and a Laval nozzle.

Images