Media-circulation type pulverizer

Abstract

The media-circulation type pulverizer comprising: an agitating member disposed in a lower region of a pulverization chamber; an annular partition wall disposed to extend upwardly in the pulverization chamber; and a media guide member provided on a lower surface of the end plate of the agitating member, wherein the annular partition wall has a height set to be to of a height of the pulverization chamber, and the media guide member has a lower end which enters a space of the inner region of the pulverization chamber located inside the annular partition wall, and wherein a vertically-extending flow straightening blade is provided between said lower portion of the media guide member and an upper portion of the annular partition wall, and the media separation member is provided on the lower end of the lower portion of the media guide member.

Claims

1. A media-circulation type pulverizer comprising: a pulverization container including an end plate closing up an upper end thereof and having a pulverization chamber having an upright cylindrical form and containing pulverizing media in the form of beads; a raw-material-slurry supply section provided in the pulverization container; an agitating member disposed in a lower region of the pulverization chamber and having a rotary shaft coaxial with a central axis of the pulverization chamber; an annular partition wall disposed to extend upwardly from a position surrounding an outer periphery of the agitating member or a position radially away from the outer periphery by a given distance, so as to radially divide an internal space of the pulverization chamber to form an inner region of a pulverization chamber and an annular outer region of the pulverization chamber; a media guide member provided on a central area of a lower surface of the end plate to extend downwardly and configured to turn a mixture of a raw material slurry and pulverizing media being moved upwardly through the outer region of the pulverization chamber by an action of the agitating member, to a downward flow so as to direct the mixture toward the inner pulverization chamber region; a media separation member provided underneath the media guide member; and a product slurry discharge section provided inside the media guide member and communicating with an inside of the media separation member so as to enable a product slurry after separation of the pulverizing media by the media separation member to be discharged to outside therethrough, wherein the media-circulation type pulverizer is operable to circulate the pulverizing media between the inner region of the pulverization chamber and the outer region of pulverization chamber to pulverize a raw material in the raw material slurry by this circulating pulverizing media, and wherein the annular partition wall has a height set to be to of a height of the pulverization chamber, and the media guide member is formed as a downwardly tapered, circular truncated cone-shaped guide member which has a lower end which enters a space of the inner region of the pulverization chamber located inside the annular partition wall, and wherein a vertically-extending flow straightening blade is provided between said lower portion of the media guide member and an upper portion of the annular partition wall, and the media separation member is provided on the lower end of the lower portion of the media guide member.

2. The media-circulation type pulverizer as recited in claim 1, wherein the agitating member comprises a hub having a portion extended to a vicinity of a lower surface of the media guide member so as to define a small gap between an upper surface of the extended portion of the hub and the lower surface of the lower portion of the media guide member, and wherein the media separation member is a gap separator formed by the small gap.

3. The media-circulation type pulverizer as recited in claim 1, wherein the media separation member is a screen separator provided underneath the lower end of the lower portion of the media guide member.

4. The media-circulation type pulverizer as recited in claim 1, which is configured to enable cooling water to pass through an inside of the media guide member and/or an inside of the annular partition wall.

5. The media-circulation type pulverizer as recited in claim 1, wherein the pulverizing media has a diameter of 0.2 to 2.0 mm.

6. The media-circulation type pulverizer as recited in claim 1, wherein the annular partition wall is made of a resin material.

7. The media-circulation type pulverizer as recited in claim 1, wherein the annular partition wall is made of a ceramic material.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a sectional view showing a media-circulation type pulverizer according to one embodiment of the present invention.

(2) FIG. 2 is a horizontal sectional view of the media-circulation type pulverizer shown in FIG. 1, wherein only a pulverization container and an annular partition wall are shown.

(3) FIG. 3 is a sectional view of a modification of the media-circulation type pulverizer comprising a different type of media separation member.

DESCRIPTION OF EMBODIMENTS

(4) With reference to the accompanying drawings, a media-agitation type pulverizer of the present invention will now be described based on one embodiment thereof.

(5) FIG. 1 shows a media-circulation type pulverizer 10 according to one embodiment of the present invention. This media-circulation type pulverizer 10 comprises an upright cylindrical pulverization container 12 including an end plate 12a closing up an upper end thereof. The pulverization container 12 internally has a columnar pulverization chamber 14, and is provided with a raw-material-slurry supply port 16 for introducing a raw material in a slurry form into the pulverization chamber 14.

(6) In a lower central region of an internal space of the pulverization chamber 14 of the pulverization container 12, an agitating member 22 having a rotational axis approximately coaxial with a central axis of the pulverization chamber 14 is rotatably disposed. The agitating member 22 is composed of a centrifugal impeller which comprises, for example, a hub 22a and a plurality of blades 22b fixed therearound.

(7) The hub 22a of the agitating member 22 is fixed to an upper end of a rotary drive shaft 24 which is an agitating-member driving shaft extending axially downwardly from the upper end while penetrating through the pulverization container 12. The rotary drive shaft 24 has a lower end which is connected to a drive source via a well-known drive mechanism (not shown) in such a manner as to be rotationally driven in the direction indicated by the arrowed line in FIG. 1. Preferably, the rotary drive shaft 24 has a rotation shaft (a rotational axis) aligned with the central axis of the pulverization chamber 14. Further, the rotary drive shaft 24 is provided with a shaft seal (e.g., a mechanical seal).

(8) In place of the above centrifugal impeller, the agitating member 22 may be composed of a diagonal flow impeller.

(9) As is well known in the field of media-circulation type pulverizers, pulverizing media 30 in the form of beads (which are shown in the figures in a significantly enlarged manner) are contained in the pulverization container 12. As the pulverizing media 30, it is possible to use pulverizing media having a diameter of 0.2 to 2 mm. A total volume of the pulverizing media is 30 to 80% of a volume of the pulverization chamber.

(10) The end plate 12a has a lower surface provided with a media guide member 31 configured to turn a flow f of a mixture of a raw material slurry and the pulverizing media 30 moving upwardly, to a downward flow (see FIG. 2). This media guide member 31 is composed of a downwardly tapered, circular truncated cone-shaped member which is provided on a central area of the lower surface of the end plate 12a and has a cylindrical internal space 31a, wherein said circular truncated cone-shaped member is configured such that an outer peripheral surface thereof is configured to turn the mixture of a raw material slurry and the bead-form pulverizing-dispersing media moving upwardly by an action of the agitating member, to a downward flow.

(11) Preferably, an angle between an inclined surface and an upper surface (larger-area surface) of the media guide member 31 is set to be 45 to 90 degrees.

(12) A media separation member 32 is provided underneath the media guide member 31 and configured to separate the media 30 dispersed in the raw material slurry, from the raw material. As shown in FIG. 1, the hub 22a of the agitating member 22 is extended upwardly to form an extended portion serving as a separation member-constructing member 22c. The media guide member 31 operates as a gap separator formed by a small gap defined between a circular upper surface 22d of the separation member-constructing member and a circular lower surface 31b of the media guide member 31. Preferably, a width e of the gap is about of the diameter of the pulverizing media. This gap separator has a simple structure and can be constructed at low cost.

(13) Preferably, the media separation member 32 has a radius less than a radius of the lower surface of the media guide member 31. This is intended to prevent most of the pulverizing media 30 flowing downwardly along the inclined surface of the media guide member 31 from gathering toward the media separation member 32 so as to provide good media separation capability to the media separation member 32.

(14) The media guide member 31 has a cylindrical-shaped internal space 31a into which a cylindrical-shaped discharge nozzle-defining member 34 having an outer diameter less than an inner diameter of the cylindrical-shaped internal space 31a is inserted, so that a discharge nozzle 36 for enabling a product slurry after separation of the pulverizing media 30 by the media separation member 32 to be discharged to the outside of the pulverizer therethrough is defined between an outer periphery of the discharge nozzle-defining member 34 and an inner periphery of the media guide member 31.

(15) Within the pulverization chamber 14, an annular partition wall 50 is disposed to extend upwardly from a position surrounding an outer periphery of the blades 22b of the agitating member 32 or a position radially away from the outer periphery by a given distance. This annular partition wall 50 is composed of an inner peripheral annular plate 52, an outer peripheral annular plate 54 spaced apart radially outwardly from the inner peripheral annular plate 52, a lower annular plate 56 forming a lower side thereof, and an upper annular plate 58 forming an upper side thereof, wherein an internal space of the annular partition wall 50 is formed in a liquid-tight manner.

(16) Preferably, the annular partition wall 50 has a height dimension which is to of a height dimension of the pulverization chamber 14.

(17) Preferably, a lower end of the media guide member 31 enters a space of the aftermentioned inner region of the pulverization chamber inside the annular partition wall.

(18) This annular partition wall 50 is disposed to radially divide a given space of the pulverization chamber 14 to form an inner region of a pulverization chamber 14a and an annular outer region of a pulverization chamber 14b. The inner region of the pulverization chamber 14a serves as a downward passage of the mixture of the pulverizing media and the raw material slurry, and the outer region of the pulverization chamber 14b serves as an upward passage of the mixture of the pulverizing media and the raw material slurry. Thus, the flow f of the mixture of the pulverizing media and the raw material slurry is formed within the pulverization chamber 14 as a combined flow (i.e., helicoidal flow) consisting of a flow moving in a circumferential direction of the pulverization chamber 14 (i.e., a primary flow) and a flow capable of regularly repeating a movement cycle of, after moving in a radially outward direction of the pulverization chamber toward an inner wall of the pulverization container, moving upwardly through an upward flow path between the annular partition wall and the pulverization container, and then moving downwardly by an effect of the media guide member 31 from a central region of the pulverization chamber 14 to return to the agitating member 22, via the inside of the annular partition wall (i.e., a secondary flow). Generally, this helicoidal flow involves a problem of being unstable due to weakness and instability of the secondary flow thereof. Therefore, preferably, a vertically-extending flow straightening blade 60 is provided between a lower portion of the media guide member 31 and an upper portion of the annular partition wall 50, as depicted in FIG. 1, to strengthen and stabilize the secondary flow and suppress the primary flow. By providing the straightening blade 60, it is possible to maximally restrict the free flow of the media in the pulverizing chamber 14 by the downward flow of mixture of the raw material slurry and the bead-form pulverizing media, to thereby reduce a concentration of the media around the media separation member 32 and restrict media floating toward the media separation member to provide further enhanced separation capacity to the media separation member. In addition, based on strengthening the secondary flow to form stable helicoidal flow, it is possible to uniformize a distribution of the pulverizing media in the helicoidal flow and eliminate dynamic localization due to centrifugal force, to thereby generate active shearing force between the pulverizing media to provide further enhanced function to the pulverizing media.

(19) Preferably, a distance between an outer peripheral wall of the annular partition wall and an inner peripheral wall of the pulverization container is in the range of 10 to 50 mm. If the distance is less than the lower limit, the movement of the beads is excessively restricted. On the other hand, if the distance is greater than the upper limit, free flowability of the beads is excessively increased.

(20) A jacket (not depicted) for enabling a cooling medium (cooling water) to pass therethrough is provided along an outer periphery of the pulverization container 12, so as to cool the pulverization chamber 14. This jacket has a lower portion provided with a coolant water inlet for introducing cooling water therethrough and an upper portion provided with a cooling water outlet 46 for discharging the cooling water therethrough.

(21) The annular partition wall 50 is formed in the above structure having an annular internal space, and supported by a plurality of pipes 62 attached to the pulverization container. The pipes 62 can be used to enable cooling water to be supplied into and discharged from the annular internal space therethrough. Thus, in this embodiment, it is possible to additionally cool the raw material slurry from the inside of the pulverization container 12.

(22) Preferably, each of the pipes 62 is disposed to extend downwardly from the upper end of the pulverizing container 12 to have a lower end supporting the guide ring 50, as shown in the drawing.

(23) Further, the media guide member 31 may be formed to define an internal space therein, and cooling water may be supplied to pass through this internal space, so as to cool the raw material slurry which is circulated or newly supplied raw material slurry.

(24) Furthermore, when cooling water is to passed through an internal space of the discharge nozzle-defining member 34, the slurry flowing through the discharge nozzle 36 can be cooled by both the cooling water passing through the discharge nozzle-defining member 34 and the cooling water passing through the media guide member 31.

(25) Generally, the slurry discharged from the pulverizer needs to be cooled. Thus, conventionally, a heat exchanger or the like has been provided in a circulation pathway. The above structure makes it possible to eliminate the need for or simplify such a heat exchanger, thereby achieving a significant reduction in cost.

(26) The pulverization container 12 is configured such that the end plate 12a can be removed to open the pulverization container 12 so as to facilitate maintenance.

(27) In the media-circulation type pulverizer of the present invention, the agitating member 22 can be rotationally driven at a circumferential velocity of 4 to 40 m/s

(28) In the above embodiment, the media separation member is composed of a gap separator. Alternatively, the media separation member may be composed of a screen type as shown in FIG. 3.

(29) In operation, the agitating member 22 is rotationally driven, while a raw material slurry containing target particles to be pulverized, as a raw material, is introduced into the pulverization chamber 14 from the raw material supply port. The slurry introduced into the pulverization chamber 14 is moved downwardly toward the agitating member 22, while riding on an already-formed circulating flow of a raw material slurry and the pulverizing media 30 in the pulverization chamber 14, and mixingly agitated by the agitating member 22. Subsequently, the resulting mixture of the slurry and the media 30 is moved radially outwardly up to the inner peripheral wall of the pulverization container 12, and then turned to form a flow f moving upwardly through the upward passage between the inner peripheral wall of the pulverization chamber 14 and the guide ring 50. Then, when the mixture is moved upwardly to a vicinity of the end plate 12a, it is turned to form the aforementioned downward flow.

(30) In this flow pathway, a part of the media having a relatively large mass are biased downwardly and separated from the slurry. In this case, an insufficiently-pulverized part of the target particles having a relatively large particle size behave in the same manner as the media. On the other hand, slurry containing sufficiently-pulverized particles having a relatively small particle size enters into an internal space of the media separation member 32 and discharged to the outside of the media-circulation type pulverizer via the discharge nozzle 36 inside the media guide member 31. By this construction, raw material particles can be subjected to good-quality pulverization and dispersion in an adequately regulated flow through a contact with freely-moving pulverizing media, thereby obtaining a high-quality product. Further, according to the media-circulation type pulverizer of the present invention, by the above-functions, it is possible to achieve pulverization with a narrow particle size distribution.

LIST OF REFERENCE SIGNS

(31) 10: media-circulation type pulverizer 12: pulverization container 14: pulverization chamber 16: raw-material-slurry supply port 22: agitating member 24: rotary drive shaft 30: pulverizing media 31: media guide member 32: media separation member 36: discharge nozzle 50: annular partition wall 60: flow straightening blade