JP2009195789A - Jet mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a collision type jet mill for colliding each compressed air jetted from a plurality of crushing nozzles which prevent the attachment of powder to the wall surface of a casing to enhance the crushing efficiency. <P>SOLUTION: The jet mill is provided with a plurality of nozzle groups each having one or more crushing nozzles 4 arranged so that the compressed air to be jetted collides on one collision point C to keep a plurality of collision points C formed by the compressed air jetted from these nozzle groups distributed circumferentially at the surrounding of a rotary classifier 3 and present between it and the wall surface 2c of the surrounding casing 2. Thus, powder carried towards the wall surface 2c of the casing 2 by the swirl of air generated at the surrounding of the rotary classifier 3 is efficiently crushed on the collision point C of the compressed air jetted from the nozzle groups at the surrounding. The attachment of the powder to the wall surface 2c can be inhibited and the crushing efficiency can be enhanced by intercepting the swirl to carry the powder to the wall surface 2c with the compressed air jetted from the nozzle groups. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a jet mill that pulverizes a material to be crushed in a casing by jetting compressed air from a pulverizing nozzle, classifies the pulverized material to be crushed by a rotary classifier disposed in the casing, and discharges the pulverized material.

  The jet mill that pulverizes the crushed material in the casing by jetting compressed air from a pulverizing nozzle, classifies the pulverized crushed material with a rotary classifier disposed in the casing, and discharges the compressed air to the jet mill. It is roughly divided into a swivel type that injects so as to swirl along the wall surface of the casing (for example, see Patent Document 1) and a collision type that collides compressed air injected from a plurality of pulverizing nozzles. (For example, see Patent Document 2). Some of the collision-type jet mills cause the compressed air injected from the crushing nozzle to collide with a collision plate provided in the casing.

  The swirl type jet mill wraps the object to be crushed into the jet swirl flow of compressed air ejected from the pulverizing nozzle and rubs the object to be crushed. Is not so strong and it is difficult to obtain fine fine powder. On the other hand, the collision type jet mill has a strong crushing action because the object to be crushed is put on a jet stream of compressed air injected from the crushing nozzle and collides with each other or collides with a collision plate provided in the casing. Suitable for obtaining fine fine powder.

Japanese Patent Publication No. 7-67541 JP 2003-88773 A

  FIG. 6 shows a rotary classifier 3 disposed in the upper part of the casing 2 forming the pulverizing chamber 1, and a plurality of pulverizing nozzles 4 opposed to the center on the wall surface of the lower part of the casing 2, An example of a collision type jet mill in which compressed air injected from these pulverizing nozzles 4 collides with each other at a collision point C will be described. The rotary classifier 3 rotates the classifying impeller 3b around the axis by the motor 3a, and only the finely pulverized fine powder that is not significantly affected by the centrifugal force due to the rotation of the classifying impeller 3b is classified into the classifying impeller 3b. The coarse powder which is taken into the inside from a plurality of classification blades provided in the inside and discharged from the fine powder discharge pipe 3c and greatly affected by the centrifugal force jumps outside by the classification blades and returns to the inside of the casing 2. .

  In such a collision type jet mill, the swirling flow of air generated around the rotary classifier 3 by the rotation of the classifying impeller 3b flows toward the wall surface of the surrounding casing 2, and the swirling flow hitting the wall surface is the wall surface. Air flow along For this reason, after the coarse powder and a part of fine powder not taken into the rotary classifier 3 are conveyed to the wall surface side of the casing 2 by this swirl flow, the air flow along the wall surface along the wall surface It moves and adheres to the wall surface of the casing 2 in a region that is not blocked by the compressed air injected from the crushing nozzle 4. In addition, in the part of the wall surface which a swirl flow directly hits, since powder has good fluidity, it does not adhere to a wall surface very much. In the example shown in FIG. 6, rotation is performed except for the wall surface on the bottom side of the casing 2 where the swirl flow is blocked by the compressed air injected from the pulverizing nozzle 4 and the wall surface directly beside the rotary classifier 3 where the swirl flow directly hits. Powder A adheres to the wall surface in the range from the lower side of the classifier 3 to the upper side of the crushing nozzle 4 or the upper wall surface of the rotary classifier 3.

  When the powder adheres to the wall surface in this way, the pulverization opportunity by the pulverization nozzle is lost, and there is a problem that the pulverization efficiency decreases. Moreover, when a large amount of powder adheres to the wall surface, the inner volume of the casing is reduced, which leads to a decrease in the function of the jet mill. In the swirl type jet mill as described in Patent Document 1, since a strong swirl flow is generated along the wall surface of the casing, it is unlikely that powder adheres to the wall surface in this way.

  Accordingly, an object of the present invention is to prevent the adhesion of powder to the wall surface of the casing and improve the pulverization efficiency in a collision type jet mill in which compressed air injected from a plurality of pulverization nozzles collides with each other.

  In order to solve the above problems, the present invention provides a rotary classifier that rotates a classification impeller around an axis in a casing forming an enclosed grinding chamber, and compresses the casing. Collision in which the compressed air to be ejected collides at one point in a jet mill in which a pulverizing nozzle for injecting air is provided, and fine powder of the crushed material pulverized by the pulverizing nozzle is classified by the rotary classifier A plurality of nozzle groups in which a plurality of the pulverizing nozzles are arranged so as to form points are provided, and a plurality of collision points formed by compressed air ejected from these nozzle groups are arranged around the rotary classifier. A configuration was adopted that is distributed in the direction and exists between the surrounding wall surfaces of the casing.

  That is, a plurality of nozzle groups in which a plurality of crushing nozzles are arranged so as to form a collision point where the compressed air to be injected collides at one point, and a plurality of collisions formed by compressed air injected from these nozzle groups Air generated around the rotary classifier by the rotation of the classifying impeller by having points distributed around the rotary classifier in the circumferential direction and between the walls of the surrounding casing. The powder that is conveyed toward the wall of the casing by the swirling flow is efficiently pulverized at the collision point of the compressed air injected from the nozzle group around it, and the powder flows by the compressed air injected from the nozzle group In order to improve the pulverization efficiency, the adhesion of the powder to the wall surface of the casing can be prevented, and the grinding efficiency can be increased. Moreover, this collision type jet mill can arrange the nozzle group which forms the collision point of compressed air in the position close | similar to a rotary classifier, and a compact design compared with the conventional collision type jet mill is attained. There are also advantages.

  By causing the plurality of collision points to be present at equal intervals on the same circumference centered on the axis of the rotary classifier, a swirling flow around the rotary classifier is directed toward the casing wall. In addition, the pulverized powder can be uniformly crushed at the collision point, and the swirling flow that conveys the powder toward the wall surface can be uniformly blocked, thereby further improving the pulverization efficiency.

  Wall surfaces on both axial sides of the axial center of the rotary classifier of the casing are formed by planes facing each other, and at least two pulverizing nozzles of the nozzle group are opposed to each other by the wall surfaces formed by the opposed planes. By arranging them, a collision point can be formed around the rotary classifier with a simple arrangement of the crushing nozzles.

  The plurality of collision points are brought close to a wall surface of a casing around the rotary classifier, and the operation of some nozzle groups among the nozzle groups forming the plurality of collision points is alternately stopped to By switching and using the nozzle group, even if the powder temporarily adheres to the wall on the rear side of the collision point of the stopped nozzle group, it will be close to this wall surface when the nozzle group is reactivated. The powder adhering temporarily can be blown off by the compressed air injected, and the powder adhering to the wall surface of the casing can be given another opportunity to pulverize again by the operation of a small number of nozzle groups.

  The jet mill of the present invention is provided with a plurality of nozzle groups in which a plurality of crushing nozzles are arranged so as to form a collision point where the compressed air to be injected collides at one point, and is formed by compressed air injected from these nozzle groups. The multiple collision points are distributed in the circumferential direction around the rotary classifier and exist between the surrounding casing and the wall of the surrounding casing. The powder carried toward the wall surface of the casing by the swirling flow of the air generated in the surroundings can be efficiently crushed at the collision point of the compressed air injected from the nozzle group around the powder, and by the compressed air injected from the nozzle group By increasing the fluidity of the powder, it is possible to prevent the powder from adhering to the wall surface of the casing and to increase the grinding efficiency.

  By causing the plurality of collision points to exist at equal intervals on the same circumference centered on the axis of the rotary classifier, the swirl flow around the rotary classifier is directed toward the casing wall surface. The powder to be conveyed is pulverized evenly at the collision point, and the swirl flow that conveys the powder toward the wall surface is uniformly interrupted, thereby further improving the pulverization efficiency.

  Wall surfaces on both axial sides of the axial center of the rotary classifier of the casing are formed as opposed surfaces, and at least two pulverizing nozzles of the nozzle group are opposed to each other on the wall surfaces formed by the opposed surfaces. By arrange | positioning, a collision point can be formed in the circumference | surroundings of a rotary classifier by arrangement | positioning of a simple crushing nozzle.

  The plurality of collision points are brought close to the wall surface of the casing around the rotary classifier, and the operation of some nozzle groups among the nozzle groups forming the plurality of collision points is alternately stopped, and the plurality of nozzles By switching the group, even if powder temporarily adheres to the wall on the rear side of the collision point of the stopped nozzle group, when the nozzle group is reactivated, it is injected close to the wall surface. With the compressed air, the temporarily adhering powder is blown off, and the powder adhering to the wall surface of the casing can be given another opportunity to pulverize with a small number of nozzle groups.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. This jet mill is of a collision type in which compressed air sprayed from a plurality of pulverizing nozzles collides with each other to pulverize the material to be crushed, and forms an enclosed pulverization chamber 1 as shown in FIGS. A rotary classifier 3 that rotates a classifying impeller 3b around a longitudinal axis by a motor 3a is disposed in the center of the casing 2 having a circular cross section. Six crushing nozzles 4 are arranged on the upper and lower wall surfaces 2a, 2b of the casing 2 formed in a plane so as to face each other in the axial direction of the center so as to face each other. Collision points C where compressed air injected from six nozzle groups composed of nozzles 4 collide are distributed in the circumferential direction around the rotary classifier 3, and between the wall surfaces 2 c around the casing 2. To come to exist. The six collision points C exist at equal intervals on the same circumference around the axis of the rotary classifier 3, and are close to the surrounding wall surface 2c.

  The rotary classifier 3 takes in only fine fine powder pulverized by the pulverization nozzle 4 of each nozzle group into the inside from among a plurality of classification blades provided in the classification impeller 3b, and externally passes through the fine powder discharge pipe 3c. To discharge. The coarse powder is splashed outward by the classification blades, returned to the casing 2, and re-ground. The rotary classifier 3 is attached to the cylindrical attachment member 5 through the lower wall surface 2 b of the casing 2, and a clearance between the through hole of the wall surface 2 b and the seal air introduction path 5 a provided in the attachment member 5. It is designed to be sealed with air supplied from. The fine powder discharge pipe 3 c is inserted into the rotary classifier 3 through the upper wall surface 2 a of the casing 2.

  Due to the rotation of the classifying impeller 3b of the rotary classifier 3, a swirling flow of air is generated around the rotary classifier 3 in the casing 2, and coarse particles and some of the particles that have not been taken into the rotary classifier 3 The fine powder is conveyed toward the surrounding wall surface 2c by this swirling flow. In the area around the rotary classifier 3 in which the six nozzle groups are alternately operated in the circumferential direction, every other three nozzle groups, By the compressed air injected from these nozzle groups, the powder carried in the swirl flow is pulverized before reaching the wall surface 2c. In the area around the rotary classifier 3 where the stopped nozzle group exists, the swirl flow is not blocked, and the powder carried by the swirl flow temporarily adheres to the wall surface 2c on the rear surface side. Since the collision point C of the group is close to the wall surface 2c, when the nozzle group is reactivated, the temporarily adhering powder is surely blown away by the compressed air jetted from these, and the opportunity for pulverization is again obtained. Given.

  FIGS. 3A, 3B, 3C, and 3D show a first modification. In each of these first modified examples, the crushing nozzles 4 constituting the nozzle group are arranged on the upper and lower wall surfaces 2a and 2b as in the embodiment, and the collision point C of each nozzle group is set to the surrounding area. (A) is a case where the cross section of the casing 2 is a triangle, and three collision points C are equally spaced on the same circumference centered on the axis of the rotary classifier 3. (B) is a case where the casing 2 has a square cross section and four collision points C are equally spaced on the same circumference, and (c) is a cross section of the casing 2. In a square shape, eight collision points C exist along the surrounding wall surface 2c at equal intervals, (d) shows a rectangular cross section of the casing 2, and the collision point C faces the longitudinal wall surface 2c. Two things existed.

  4 (a), (b), (c), (d), (e), and (f) each show a second modification. In each of these second modified examples, the crushing nozzles 4 constituting the nozzle group are arranged on the surrounding wall surface 2c, and the collision point C of each nozzle group is brought close to the surrounding wall surface 2c. ) Has a triangular cross section of the casing 2, and three collision points C exist on the same circumference centered on the axis of the rotary classifier 3 at equal intervals, and (b) shows the casing 2 (C) is a rectangular cross section of the casing 2 and the collision point C is the longitudinal wall surface 2c. (D) shows the collision point C of (c) composed of three crushing nozzles 4, and (e) shows a cross section of the casing 2 with a rounded corner in the longitudinal direction. (F), which has two collision points C on the corner portion side in the longitudinal direction. The collision point C) of which is constituted by three grinding nozzles 4.

  5 (a), (b), (c), (d), and (e) each show a third modification. In these third modifications, the crushing nozzles 4 constituting the nozzle group are arranged on both the upper and lower wall surfaces 2a, 2b and the surrounding wall surface 2c, and the collision point C of each nozzle group is placed on the surrounding wall surface 2c. (A) is that the casing 2 has a triangular cross section, and three collision points C exist at equal intervals on the same circumference centered on the axis of the rotary classifier 3. (B) is a case in which the cross section of the casing 2 is square, and four collision points C are equally present on the same circumference, and (c) is a case in which the cross section of the casing 2 is square. Two collision points C exist on the side of the pair of wall surfaces 2c facing each other, (d) is a case where the casing 2 has a rectangular cross section and two collision points C exist on the side of the wall surface 2c in the longitudinal direction. , (E) is a rhombus with a rounded corner in the longitudinal direction of the casing 2. The collision point C in the longitudinal direction of the corner portion is obtained by the presence of two. In addition, in each modification of (a), (b), (c), each nozzle group is composed of four crushing nozzles 4 arranged two on the upper and lower wall surfaces 2a, 2b and the surrounding wall surface 2c, In each modification of (d) and (e), each nozzle group is composed of five crushing nozzles 4 arranged on the upper and lower wall surfaces 2a and 2b and three on the surrounding wall surface 2c.

  In the embodiment and each modification described above, the axis of the rotary classifier is vertically oriented, and the upper and lower wall surfaces of the casing on both sides in the axial direction of the axis are formed as planes, but the axis of the rotary classifier is horizontally oriented. The shape of the wall surface of the casing is not limited to those of these embodiments and modifications. In addition to the collision pulverizing nozzle, a swirling nozzle that injects compressed air to swirl along the wall surface of the casing may be provided as an auxiliary.

A longitudinal sectional view showing an embodiment of a jet mill Sectional view along the line II-II in FIG. a, b, c, and d are cross-sectional views showing the first modification of FIG. a, b, c, d, e, and f are sectional views showing the second modification of FIG. a, b, c, d, and e are sectional views showing the third modification of FIG. A longitudinal sectional view showing an example of a conventional collision type jet mill

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crushing chamber 2 Casing 2a, 2b, 2c Wall surface 3 Rotary classifier 3a Motor 3b Classification impeller 3c Fine powder discharge pipe 4 Crushing nozzle 5 Attachment member 5a Seal air introduction path

Claims (4)

  In the casing forming the enclosed grinding chamber, a rotary classifier for rotating the classification impeller around the shaft center is provided, and a grinding nozzle for injecting compressed air is provided in the casing. In the jet mill that classifies and discharges the fine powder of the pulverized material by the rotary classifier, a plurality of the pulverizing nozzles are arranged so as to form a collision point where the injected compressed air collides at one point. A plurality of collision points formed by compressed air injected from these nozzle groups are distributed in the circumferential direction around the rotary classifier, and the wall surface of the surrounding casing A jet mill characterized by existing in between.   2. The jet mill according to claim 1, wherein the plurality of collision points exist at equal intervals on the same circumference centering on an axis of the rotary classifier.   Wall surfaces on both axial sides of the axial center of the rotary classifier of the casing are formed by planes facing each other, and at least two pulverizing nozzles of the nozzle group are opposed to each other by the wall surfaces formed by the opposed planes. The jet mill according to claim 1, wherein the jet mill is arranged.   The plurality of collision points are brought close to a wall surface of a casing around the rotary classifier, and the operation of some nozzle groups among the nozzle groups forming the plurality of collision points is alternately stopped to The jet mill according to any one of claims 1 to 3, wherein the nozzle group is switched and used.

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