Jet mill

Abstract

Disposed is a jet mill that has a cylindrical pulverization chamber (10) and a classification chamber (6) that connects to the pulverization chamber (10). A fine-powder discharge port (4a) and a classification rotor (7) are provided in the classification chamber (6). A feedstock supply port (5) and at least one gas emission nozzle (11) are provided in the pulverization chamber (10). The shape of the classification chamber (6) is a cone that starts on the inner wall of the pulverization chamber (10), and is angled towards the classification rotor (7). This configuration gives the jet mill high efficiency of pulverization and reduces the amount of powders left in the chamber when the jet mill has finished running.

Claims

1. A jet mill comprising: a lower casing having an external peripheral surface and a cylindrical internal peripheral surface; an upper casing having a conical internal peripheral surface; and an adapter plate provided at a center of a bottom portion of the lower casing, the adapter plate having a horizontally-oriented flat top surface and a side surface which is inclined from an external periphery of the top surface toward the bottom portion of the lower casing, wherein a space defined by the conical internal peripheral surface of the upper casing and the inclined side surface of the adapter plate forms a lower cylindrical pulverization chamber and an upper classification chamber connected with the pulverization chamber, wherein the classification chamber is provided with a classification rotor connected with a fine-powder discharge port, the conical internal peripheral surface of the upper casing extending from the cylindrical internal peripheral surface of the lower casing and being inclined toward the classification rotor along an axis of the classification rotor, and wherein the pulverization chamber is provided with a raw material supply port and at least one gas emission nozzle disposed slanted in a rotational direction of the classification rotor from an external peripheral wall surface, the raw material supply port having an open end formed where the conical internal peripheral surface of the upper casing meets the cylindrical internal peripheral surface of the lower casing to supply raw material powder to the pulverization chamber.

2. The jet mill according to claim 1, wherein the mill is provided with a collision member facing a distal end of the gas emission nozzle across a predetermined gap.

3. The jet mill according to claim 2, wherein a collision surface of the collision member is inclined relative to the gas emission nozzle toward an internal peripheral surface of a casing of the pulverization chamber.

4. The jet mill according to claim 2, wherein the collision surface of the collision member is configured as a cone, a pyramid, or an obliquely truncated circular or polygonal pillar.

5. The jet mill according to claim 1, wherein the pulverization chamber and the classification chamber are integrated together and oriented laterally.

6. The jet mill according to claim 5, wherein the gas emission nozzle is oriented substantially horizontally at a position at a bottom of the pulverization chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross-sectional view showing an embodiment of the jet mill of the present invention;

(2) FIG. 2 is a perspective view showing an embodiment of the jet mill of the present invention;

(3) FIG. 3 is a perspective view showing another embodiment of the jet mill of the present invention;

(4) FIG. 4 is a graph showing performance of working examples of the jet mill of the present invention and comparative examples; and

(5) FIG. 5 is a schematic drawing of a jet mill used as a comparative example in a working example of the present invention.

BEST MODE FOR EMBODYING THE INVENTION

First Embodiment

(6) The first embodiment of the present invention will be described hereunder based on FIGS. 1 and 2.

(7) The jet mill according to the first embodiment of the present invention has a bottomed cylindrical lower casing 1 open at the top, and an upper casing 2 superposed on the lower casing 1. The upper casing 2 is removably attached to the lower casing 1 by a fastening tool 3. With the upper casing 2 attached to the lower casing 1, the upper casing 2 and the lower casing 1 have a common vertical axis X, as shown in FIG. 1. In FIG. 2, the upper casing 2 is shown as being removed.

(8) The lower casing 1 has a generally cup-like shape comprising a generally cylindrical bottom portion 1a having a through-hole in the center, and a cylindrical side wall portion 1b generally extending vertically upward from the radially outer side end of the bottom portion 1a.

(9) The upper casing 2 has a generally annular shape comprising a fine-powder discharge port 4a in the center the fine-powder discharge port 4a being for discharging fine powder. More specifically, the upper casing 2 has a top surface 2a extending generally horizontally, a cylindrical external peripheral surface 2b extending generally vertically downward from the radially outer side end of the top surface 2a, and a generally conical inner peripheral surface 2c extending obliquely upwards in a substantially linear manner from the bottom end of the external peripheral surface 2b to the radially inner side end of the top surface 2a, i.e. to the fine-powder discharge port 4a.

(10) A fine-powder discharge tube 4 is connected to the top of the fine-powder discharge port 4a so as to share an axis X. In a location near the external periphery of the upper casing 2, a raw material supply tube 5 (an example of the raw material supply port) passing vertically through the upper casing 2 is provided, and powder as a material to be processed is supplied to the lower casing 1 via this raw material supply tube 5.

(11) Attached to the center of the bottom portion 1a in the lower casing 1 is a bottom plate 14 in the shape of a circular truncated cone (an example of the circular truncated cone-shaped adapter), comprising a top surface 14a having a flat circular outer shape slightly larger than the fine-powder discharge port 4a, and an inclined side surface 14b expanding gradually outward from the external periphery of the top surface 14a toward the bottom portion 1a.

(12) Since the outside diameter, i.e. the maximum outside diameter of the lower end of the bottom plate 14 is designed to be sufficiently smaller than the inside diameter of the side wall portion 1b of the lower casing 1, part of the bottom portion 1a (the outermost periphery) of the lower casing 1 extends as a generally flat annular portion between the external periphery of the bottom plate 14 and the internal periphery of the side wall portion 1b of the lower casing 1.

(13) A generally circular truncated cone-shaped space is formed within the jet mill by the conical inner peripheral surface 2c of the upper casing 2 and the inclined side surface 14b of the bottom plate 14, and this circular truncated cone-shaped space is conveniently divided into a lower pulverization chamber 10 where mainly pulverization takes place, and an upper classification chamber 6 where mainly classification takes place.

(14) A gas emission nozzle 11 is provided in the pulverization chamber 10 as shown in FIG. 2. The gas emission nozzle 11 is provided at the distal end of a gas jet tube 11p attached so as to pass through the side wall portion 1b of the lower casing 1, and the gas emission nozzle 11 is provided to be inclined in the rotational direction of a classification rotor 7, described hereinafter, from the external peripheral side surface of the side wall portion 1b. The proximal end side of the gas jet tube 11p is connected with a compressor 30 by a gas supply hose 11b. A gas storage tank T is provided in the middle of the gas supply hose 11b, the gas storage tank T being fixed to a casing 20 that supports the jet mill.

(15) Since the gas jet tube 11p and the gas emission nozzle 11 are disposed inclined laterally in relation to the diameter of the lower casing 1, high-pressure compressed gas from the compressor 30 discharged from the gas emission nozzle 11 generates a high-speed swirl flow of gas in the pulverization chamber 10. The angle of inclination in relation to the diameter of the gas jet tube lip and the gas emission nozzle 11 is preferably set within a range of approximately 40 to 70 degrees when the inside diameter of the lower casing 1 is approximately 400 mm, for example, but the angle of inclination can be an angle needed to generate a swirl flow in the pulverization chamber 10.

(16) Furthermore, a collision member 12 as pulverizing means is provided in the pulverization chamber 10. The collision member 12 is disposed at a position inwardly separated by a predetermined distance from the side wall portion 1b and bottom portion 1a of the lower casing 1, and the collision member 12 has a columnar base part 12b and a conical collision surface 12a provided to the base part 12b on the opposite side of a rod-shaped member 12c.

(17) As shown in FIG. 2, the collision member 12 is disposed at an end of the rod-shaped member 12c provided as parallel with the gas jet tube 11p, and the rod-shaped member 12c is supported at the distal end of a support member 13 provided so as to pass generally in the diameter direction through the side wall portion 1b of the lower casing 1.

(18) The support member 13 supports the rod-shaped member 12c in such manner that the entire collision member 12 including the other end of the rod-shaped member 12c is separated from the bottom portion 1a of the lower casing 1 and the inside surface of the side wall portion 1b.

(19) The collision surface 12a is disposed so as to face the swirl flow generated by the gas emission nozzle 11 and an emission port 11a itself of the gas emission nozzle 11. The collision surface 12a and the emission port 11a of the gas emission nozzle 11 are placed so as to face each other across a predetermined gap.

(20) Hereinabove, the predetermined gap in the present invention is defined as a distance whereby a sufficient speed is maintained in order for the powder accelerated by the gas emission nozzle 11 to collide and be pulverized. The predetermined gap is preferably set to approximately 30 to 260 mm, although it differs depending on the inside diameter of the lower casing 1, the port diameter of the emission port 11a, and the emitted air quantity. The predetermined gap is preferably set to approximately 70 to 130 mm, in a case in which the inside diameter of the lower casing 1 is approximately 400 mm, the port diameter (the diameter) of the emission port 11a is approximately 8.6 mm, and the air quantity is approximately 5 m.sup.3/min, for example.

(21) Thus, the powder supplied from the raw material supply tube 5 into the pulverization chamber 10 is made to collide with the collision surface 12a by the emitted gas (jet airflow) from the gas emission nozzle 11, whereby the power can be finely pulverized.

(22) Particularly, at least a part of the conical collision surface 12a, i.e. the region near the side wall portion 1b of the lower casing 1 is configured as a specific surface inclined toward the side wall portion 1b of the lower casing 1 relative to the diameter direction in association with the axis X, much of the powder reflected by this specific surface continuously collides with the side wall portion 1b of the lower casing 1, thereby being pulverized further.

(23) In the center along the diameter of the classification chamber 6, more specifically between the flat top surface of the bottom plate 14 and the fine-powder discharge port 4a of the upper casing 2, there is provided a classification rotor 7 which is rotatably driven about the axis X. The classification rotor 7 has a generally cylindrical shape, the external peripheral surface of which is continuously connected with the circular truncated cone shaped classification chamber 6, and the top end of the classification rotor 7 is continuously connected with the fine-powder discharge port 4a.

(24) The classification rotor 7 is attached to the top end of a rotating shaft 8 extending in a vertical direction from a space below the lower casing 1 to a space above the top surface 14a of the bottom plate 14, via through-holes formed in the centers of the bottom plate 14 and the lower casing 1. A pulley 9 is attached to the bottom end of the rotating shaft 8 to rotate the classification rotor 7 in the direction of the arrow shown in FIG. 2 by a motor (not shown). The rotational direction of the classification rotor 7 coincides with the orientation of the jet airflow from the gas emission nozzle 11.

(25) The classification rotor 7 has a lower ring member 7a connected to the top end of the rotating shaft 8, an upper ring member 7b disposed to face the bottom surface of the periphery of the through-hole in the upper casing 2 forming the fine-powder discharge port 4a, and a plurality of classification blades 7c extending vertically so as to connect the lower ring member 7a and the upper ring member 7b. Each of the classification blades 7c has a long, thin, rectangular plate shape extending vertically, and the inside diameter of the upper ring member 7b is substantially the same as the inside diameter of the fine-powder discharge tube 4.

(26) The lower ring member 7c comprises a circular truncated cone shaped base end portion connected to the top end of the rotating shaft 8, and a circular plate shaped portion extending in a radially outward direction from the bottom end of the base end portion, and the classification blades 7c are erected from the top surface of the circular plate shaped portion. The outside diameter of the circular plate shaped portion is substantially the same as the diameter of the top surface 14a of the bottom plate 14, and the circular plate shaped portion is disposed to face the top surface 14a of the bottom plate 14. The classification rotor 7 is supported on the rotating shaft 8 in a cantilever fashion via the lower ring member 7a, as shown in FIG. 1.

(27) The shape and number of the classification blades 7c are not limited to the example shown in FIGS. 1 and 2, and can be selected as desired. The shape of the classification blades 7c can be selected from a flat plate shape, a wedge shape that is thick in the external peripheral side and thin in the inner side, a teardrop shape having a curved surface in the external peripheral side, a curved flat plate, a flat plate with a bent distal end, and, a shape such that the upper outside diameter of the classification rotor 7 is greater than the lower outside diameter, or the like.

(28) The classification blades 7c are disposed in a radial formation from the center of the classification rotor 7 along the external peripheral surface, but may also be disposed slanted to the opposite direction of the rotational direction relative to the center. It is configured such that, when the upper casing 2 being attached, a small gap is formed but there is no contact between the bottom surface of the periphery of the through-hole in the upper casing 2 and the top end surface of the upper ring member 7b of the classification rotor 7.

(29) In the inside surface of the upper casing 2 facing the upper ring member 7b of the classification rotor 7, two annular grooves are provided so as to be separated from each other in the radial direction. A labyrinth seal is thereby created in the gap between the upper casing 2 and the classification rotor 7, and the coarse powder is prevented from getting out from the classification chamber 6 into the fine-powder discharge tube 4. Furthermore, by supplying a compressed gas into the gap so that the pressure in the gap exceeds that of the interior of the classification chamber 6, whereby coarse powder can be more effectively prevented from getting out.

(30) In the same manner, the configuration is such that a small gap to prohibit a contact is formed with between the lower ring member 7a and the top surface 14a of the bottom plate 14.

(31) The powder supplied from the raw material supply tube 5 is accelerated by the gas emitted from the gas emission nozzle 11, and is pulverized by colliding with the collision member 12 or the internal peripheral wall surface of the lower casing 1, or by collisions with itself. It is configured such that the powder repeatedly collides with the collision member 12 and with itself while swirling at high speeds around the conical internal peripheral surface of the upper casing 2, and pulverization of the powder proceeds.

(32) The fine powder that has been made into a fine powder by the pulverization process is transferred from the pulverization chamber 10 to the classification chamber 6, while swirling at high speeds along the internal peripheral surface. Inside the classification chamber 6, fine powder that has been sufficiently made into a fine powder is classified by the classification rotor 7, passed through the interior of the classification rotor 7 to be expelled out of the apparatus through the fine-powder discharge tube 4, and recovered by a cyclone, a dust collector, or another known collecting means. On the other hand, coarse powder larger than a predetermined grain size is not passed through the classification rotor 7, but is carried to the lower side of the classification rotor 7 and returned to the pulverization chamber 10 to be pulverized again.

(33) It is possible to set the size and inclination angle and so on of the bottom end of the bottom plate 14 as desired. For example, when the inside diameter of the lower casing 1 is approximately 400 mm and the height of the internal peripheral surface is approximately 75 mm, it is possible to set, the outside diameter of the top end of the bottom plate 14 as approximately 170 mm, the outside diameter of the bottom end as approximately 300 mm, the inclination angle of the same as approximately 50 degrees, and the height of the same as approximately 75 mm. Although it may be configured such that the outside diameter of the bottom end of the bottom plate 14 is greater than the outside diameter of the top end to form an inclined surface, it is preferable to set said outside diameter as at least one-half of the inside diameter of the lower casing 1, in terms of further reducing the amount of stagnant powder.

(34) Though not shown, the fine-powder discharge port 4a may be provided in the top surface of the bottom plate 14, and the fine-powder discharge tube 4 may be passed through the middle of the bottom plate 14 and drawn out below the lower casing 1. In this case, the classification rotor 7, the rotating shaft 8, and the pulley 9 are supported on the upper side of the upper casing 2.

(35) In the present embodiment, the number of gas emission nozzles 11 attached to the lower casing 1 is not limited to one, and it may be a plurality. The inside diameter of the emission port 11a can also be varied as appropriate according to the type, the properties, the grain size, or the intended grain size of powder. Depending on the type of powder, the collision member 12 may not be provided, and the powder would be finely pulverized by swirling at high speeds inside the pulverization chamber 10 and thereby colliding with itself or colliding with the internal peripheral wall surface of the lower casing 1.

(36) The shape of the collision surface 12a of the collision member 12 is not limited to a conical shape, and it may be a pyramid or a spherical shape. The base portion 12b may be a polygonal pillar or a sphere instead of a circular pillar. When a circular pillar or a polygonal pillar is used as the shape of the base portion 12b, the collision surface 12a is preferably configured from a surface inclined toward the side wall portion 1b of the lower casing 1 in relation to the diameter direction associated with the axis X, so that the powder rebounds toward the internal peripheral surface of the lower casing 1 after having collided with the collision surface 12a.

(37) The material of the collision surface 12a of the collision member 12 is preferably made from a super hard alloy or a ceramic in view of preventing damage from abrasion, but depending on the type of powder, the material is not necessarily limited to these examples. It is possible to use aluminum oxide, zirconium oxide, tungsten carbide, silicon carbide, titanium carbide, silicon nitride, titanium nitride and so on, but without limitation, as the preferred examples of the super hard alloy or ceramic.

(38) When a heat-sensitive raw material is pulverized, it is also possible to cool the collision member 12. As a method of cooling, it is conceivable to let refrigerant flow through a refrigerant flow channel provided inside the collision member.

(39) The pulverizing force can also be adjusted by varying the gap between the gas emission nozzle 11 and the collision member 12 as appropriate. Specifically, the configurations of these members can be varied as appropriate according to the type of powder, the properties, the grain size, or the intended grain size. For this purpose, the means for connecting the support member 13 and the rod-shaped member 12c is configured to be capable of adjusting the gap between the collision surface 12a and the emission port 11a.

(40) The materials for the lower casing 1, the upper casing 2, the fine-powder discharge tube 4, the classification rotor 7, the gas emission nozzle 11, the bottom plate 14, and other components are not particularly limited; these components may be created from a common material such as stainless steel. In the case of powder that has a high abrasive effect, at least components that powder contacts, including the gas emission nozzle 11 and the collision member 12, are preferably made from a super hard alloy or a ceramic material. It is possible to use aluminum oxide, zirconium oxide, tungsten carbide, silicon carbide, titanium carbide, silicon nitride, titanium nitride and so on, but without limitation, as the preferred examples of the super hard alloy or ceramic.

Second Embodiment

(41) The second embodiment of the present invention will be described hereunder based on FIG. 3.

(42) In the second embodiment, essentially, the pulverization chamber 10 and the classification chamber 6 in the jet mill in the embodiment described using FIGS. 1 and 2 are oriented laterally, and the gas emission nozzle 11, classification rotor 7, and other configurational members of these chambers are attached accordingly.

(43) The term oriented laterally means to being disposed so that the rotational axis direction and gravitational axis direction of the classification rotor 7 are substantially orthogonal to each other.

(44) Namely, the essential structure is the same as the first embodiment shown in FIGS. 1 and 2, but in the case of a lateral orientation, it is preferable that the raw material supply tube 5 should be attached to the external peripheral wall surface of the lower casing 1 constituting the pulverization chamber 10, the raw material supply tube 5 to be displaced to a side from the center of the lower casing 1 and disposed along the rotational direction of the classification rotor 7 so as to be connected with the pulverization chamber 10.

(45) In the second embodiment, since the pulverization chamber 10 and the classification chamber 6 are oriented laterally, the powder stagnates more easily in the lower part of the lower casing 1 due to gravity. Therefore, the gas emission nozzle 11 and the collision member 12 are disposed in the vertically lower part of the lower casing 1 with a substantially horizontal orientation. Thereby, a pulverizing effect can be imparted to the powder by the gas emission nozzle 11 and the collision member 12, under the condition in which the concentration of powder is high in a limited space, the powder can be pulverized effectively.

Embodied Example

(46) As an embodied example, a pulverization test was conducted using the laterally oriented jet mill of the second embodiment shown in FIG. 3. As a comparative example, a pulverization test was conducted using the fluidized bed type jet mill (Counter Jet Mill 200 AFG (Hosokawa Micron Group)) shown in FIG. 5. FIG. 4 shows the results of these pulverization tests.

(47) In these both pulverization tests, heavy calcium carbonate having a mean grain size of 235 m was used as the object to be processed. The operation was performed with adjusting the rotational speeds of both classification rotors 7, 27 in such way that the mean grain sizes of the products obtained by the two pulverization become equal, and the pulverization efficiencies at this time were compared. The masses of powder remained inside the apparatus after the operation had ended were also weighed and compared.

(48) FIG. 4 is a graph in which the horizontal axis is the mean grain size [m] of the powder obtained by pulverization, and the vertical axis is the processing ability per unit air quantity, i.e. the pulverization efficiency ((kg/h)/(m.sup.3/min)).

(49) As shown in FIG. 4, although there is no great difference in the mean grain sizes of the resulting powders between the embodied examples and the comparative examples, it is clear that the embodied examples had better pulverization efficiency than the comparative examples. In other words, to obtain the products with the same mean grain size, it is clear that the working examples show a greater energy conservation effect than the comparative examples. The amount of stagnant powder in the apparatus remained after the operation had ended was 2 kg in the embodied examples which is far less than 17 kg in the case of comparative examples, and the amount of raw material wasted was successfully reduced.

INDUSTRIAL APPLICABILITY

(50) The present invention is an apparatus that can finely pulverize various materials efficiently in a wide range of fields, typical examples including: inorganic compounds such as: lithium compounds including lithium carbonate, lithium hydroxide, lithium nicolate, lithium cobalt oxide, and lithium manganite, etc.; sodium compounds including sodium nitrate (sodium sulfate), sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium sulfite, sodium nitrite, sodium sulfide, sodium silicate, sodium nitrate, sodium bisulfate, sodium thiosulfate, and sodium chloride, etc.; magnesium compounds including magnesium sulfate, magnesium chloride, magnesium hydroxide, magnesium oxide, magnesium carbonate, magnesium acetate, magnesium nitrate, magnesium oxide, and magnesium hydroxide, etc.; aluminum compounds including aluminum hydroxide, aluminum sulfate, aluminum hydroxide, poly aluminum chloride, aluminum oxide, alum, aluminum chloride, aluminum nitride, etc.; silicon compounds including silicon oxide, silicon nitride, silicon carbide, calcium silicate, magnesium silicate, sodium silicate, aluminum silicate, etc.; potassium compounds including potassium chloride, potassium hydroxide, potassium sulfate, potassium nitrate, potassium carbonate; calcium compounds including calcium carbonate, calcium chloride, calcium sulfate, calcium nitrate, calcium hydroxide, etc.; titanium compounds including titanium oxide, barium titanate, strontium titanate, titanium carbide, titanium nitride, etc.; manganese compounds including manganese sulfate, manganese carbonate, manganese oxide, etc.; iron compounds including iron oxide etc.; cobalt compounds including cobalt chloride, cobalt carbonate, cobalt oxide, etc.; nickel compounds including nickel hydroxide, nickel oxide, etc.; yttrium compounds including yttrium oxide, yttrium iron garnet, etc.; zirconium compounds including zirconium hydroxide, zirconium oxide, zirconia silicate, zircon sand, etc.; antimony compounds including antimony chloride, antimony oxide, antimony sulfate, etc.; barium compounds including barium chloride, barium oxide, barium nitrate, barium hydroxide, barium carbonate, barium sulfate, barium titanate, etc.; bismuth compounds including bismuth oxide, bismuth subcarbonate, bismuth hydroxide, etc.; magnetic materials including alnico magnets, iron-chrome-cobalt magnets, iron-manganese magnets, barium magnets, strontium magnets, samarium-cobalt magnets, neodymium-iron-boron magnets, manganese-aluminum-carbon magnets, praseodymium magnets, and platinum magnets; as well as pigments, glass, metal oxides, carbon, active carbon, coke, minerals, talc, battery materials, hydrogen storage alloys, organic compounds, resins, toners, powder paints, and the like. Because the amount of stagnant powder in the apparatus and the remained amount after the apparatus has stopped are both small, the amount of raw material wasted can be reduced either.

EXPLANATIONS OF LETTERS OR NUMERALS

(51) 1 Lower casing 2 Upper casing 3 Fastening tool 4 Fine-powder discharge tube 4a Fine-powder discharge port 5 Raw material supply tube (raw material supply port) 6 Classification chamber 7 Classification rotor 7c Classification blades 8 Rotating shaft 9 Pulley 10 Pulverization chamber 11 Gas emission nozzle 11a Emission port 12 Collision member 12a Collision surface 12b Base portion 12c Rod-shaped member 13 Support member 14 Bottom plate (circular truncated cone shaped adapter) 20 Container 21 Gas emission nozzle 27 Classification rotor X axis T Gas storage tank