JP3542382B2 - Classifier - Google Patents

Description

[0001]
[Industrial applications]
TECHNICAL FIELD The present invention relates to a classification device capable of separating / classifying fine particles with high accuracy by a wet method.
[0002]
[Prior art]
Generally, most of raw materials and intermediate materials of so-called new materials such as fine ceramics, polymer materials, and electronic materials are powders. The material properties are controlled by the powder, and the adjustment of particle size occupies an important weight. Therefore, strict uniformity and completeness are required for adjusting the particle size of the raw material powder.
On the other hand, conventionally, in the field of dry classification, classification of submicron particles has also been performed, but there has been a problem of deterioration in classification performance due to adhesion and aggregation of fine particles on the particle surface. Therefore, in the case where classification accuracy and certainty are required, it is presently necessary to rely on wet classification.
The advantage of this wet classification over the dry classification is that adhesion between particles and between particles and vessel walls and cohesion are much smaller. This is because the intermolecular force between liquid molecules is large, the intermolecular force acting between particles is relatively weakened, and an electric repulsion force is generated in the particles due to the electric double layer at the particle-liquid interface. It is believed to be. Further, in order to prevent adhesion and agglomeration of particles, the volume concentration of the particles must be extremely low in the dry classification, but the wet classification is practically possible even at a considerably high solid concentration.
In order to classify fine particles more accurately by a wet method, it is pursued to reduce fluid turbulence in a classification zone.
As a wet classification device developed for such a purpose, for example, one disclosed in Japanese Patent Publication No. 3-97 is known.
[0003]
According to the technology disclosed in the above publication, a swirling flow of a slurry containing fine powder is formed between a rotating body having a circular cross section and an inner cylinder which rotates coaxially with the rotating body, while the inner cylinder and the inner cylinder are rotated. A swirling flow of liquid such as water is formed between the inner cylinder and the outer cylinder that rotates coaxially, and the swirling flow and the swirling flow of the slurry are joined together below the inner cylinder and classified by a splitter. It is configured as follows.
That is, the slurry flows down the flow path formed inside the inner cylinder, and the auxiliary liquid flows down while turning the flow path formed between the inner cylinder and the outer cylinder, These meet in a classifying chamber formed below between the inner cylinder and the outer cylinder. In this classifying chamber, coarse particles in the fine powder contained in the slurry are greatly affected by the centrifugal force due to the swirling flow of the slurry as compared with fine particles, and the particles have a particle size (strictly speaking, particle weight). A). As a result, in the lower splitter, fine fine powder is classified and collected in the center portion and coarse fine powder is separated and collected in the peripheral side portion.
[0004]
[Problems to be solved by the invention]
In the classifier according to the above configuration, since the rotating body and the wall surface of the inner cylinder rotate together with the fluid, the speed difference between the fluid and the wall surface is small, and the fluid is not disturbed. However, turbulence at the boundary between the slurry and the fluid was unavoidable, and the problem of coarse particles being mixed into fine particles could not be avoided.
Furthermore, in the above-mentioned apparatus, there is a problem that the fluid is disturbed in the classification chamber under the influence of the inner cylinder positioned above and the splitter positioned below.
Therefore, the present invention has been made in view of the above circumstances, and completely prevents coarse particles from being mixed into fine products without causing turbulence in a classifying chamber, thereby enabling high-precision classification. The purpose of the present invention is to provide a classifier.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the main means adopted by the present invention includes, as a gist, a substantially spherical rotor which rotates integrally and a housing which contains the rotor inside , and the surface of the rotor and the housing are provided. A fluid containing particles having different particle sizes is continuously supplied to the gap between the inner peripheral wall surfaces of the housing, and based on the difference in centrifugal force applied to the particles caused by the difference in size of the particles, In a classifier for discharging a fluid containing small-sized particles from a discharge hole communicating with the gap, the rotor and the housing are rotated at a speed at which a quasi-rigid rotating flow is generated. This is a classification device characterized in that it is attached to and collected on a surface.
[0006]
[Action]
The rotor and the housing are integrally rotated at a high speed, for example, and a liquid and a raw material slurry are supplied to a classifying chamber formed between the rotor and the housing. Thereby, a stable quasi-rigid rotating stratified flow composed of the Ekman layer, the shear layer (Stewartson layer), the inner region, and the rigid rotating region is generated in the classifying chamber.
Classification is mainly performed in a shear layer, and coarse particles (coarse product) taken into the rigid rotation region do not go out of the rigid rotation region again, and can perform high-precision classification.
[0007]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings to facilitate understanding of the present invention. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
Here, FIG. 1 is a side sectional view of a classifier according to one embodiment of the present invention, FIG. 2 is an enlarged view of a main part in FIG. 1, FIG. 3 is a graph showing a classification result by the classifier, and FIG. Is a graph showing the partial classification efficiency obtained based on the classification result in Fig. 5, Fig. 5 is a schematic diagram of a classification device for explaining a numerical simulation of classification, and Fig. 6 is a graph showing a spherical particle in a quasi-rigid rotating stratified flow under predetermined conditions. FIG. 7 is a graph showing a partial classification efficiency obtained from the obtained motion trajectory, and FIG. 7 is a schematic configuration diagram of a classification device according to another embodiment of the present invention.
In the classifier 1 according to this embodiment, as shown in FIGS. 1 and 2, a rotating shaft 5 is rotatably supported on a base 2 via bearings 3 and 4, and a driving force is transmitted to a lower portion thereof. Pulley 6 is mounted. At the upper end of the rotating shaft 5, a rotor 7 having a cylindrical surface and a housing 8 having a spherical inner peripheral surface are integrally mounted on the same axis. A classifying chamber 9 is formed by a gap between the outer peripheral surface of the housing 7 and the inner peripheral surface of the housing 8.
[0008]
An inflow-side slip ring 10 is connected to the upper end of the housing 8. A first supply port 11 is provided at a position of the axis of the inflow-side slip ring 10, and a second supply port 12 is provided outside the first supply port 11. Is provided. Then, raw material slurry is supplied from the first supply port 11 and water is supplied from the second supply port 12 to the classification chamber 9.
A first discharge hole 13 is provided at a lower axis position of the classifying chamber 9, and the first discharge hole 13 is a second discharge hole penetrated at the axis position of the rotary shaft 5. 14. The second discharge hole 14 is communicated with an outflow-side slip ring 15 connected to the lower end of the rotary shaft 5, and fine products are discharged from an outlet 16 provided in the outflow-side slip ring 15. You.
On the other hand, the coarse product is collected by adhering to the inner peripheral wall surface of the housing 8.
Hereinafter, the relationship between the specific dimensions (unit: mm) of the main part and the flow rate in the classification device 1 will be described.
r _R = 72.64: radius of the cylindrical portion of the rotor 7 R _R = 87.90: radius of the spherical portion of the rotor 7 R _H = 94.49: radius of the spherical portion of the housing 8 d _O = 8: of raw material slurry Inner diameter (outer diameter is 10) of supply pipe (first supply port 11)
d _W = 10.9: inner diameter d _S = 36 of the water supply cylindrical portion: shaft diameter d _F = 6 of the rotary shaft 5 at the fitting portion with the rotor 7: discharge cylindrical portion of the fine particle product (second discharge hole) The radius Q _O of the intermediate part of the diameter, which changes in three steps in 14): the flow rate of the raw slurry Q: the total flow rate of the raw slurry and water = the flow rate of the fine product Q−Q _O : the flow rate of water
In the classifying apparatus 1 as described above, the quasi-rigid rotary stratified flow is generated in the classifying chamber 9 by supplying water and raw material slurry to the classifying chamber 9 and rotating the rotor 7 and the housing 8 integrally at a high speed. I do. Then, by classifying the raw material slurry in the quasi-rigid rotating stratified flow, only the fine product completely prevented from mixing coarse particles is discharged from the discharge port 16.
Here, the classification conditions in the classification device 1 will be described in detail.
That is, the conditions of the Ekman number E = ν / (Ωr _R ² ) and the Rossby number ε = Q / (4πΩr _R ³ E ^0.5 ) for obtaining a stable quasi-rigid rotating stratified flow are obtained from the flow visualization experiment. ≤ 1.59E ^0.46 . Therefore, in an experiment using the classifier 1, E = 5.37 × 10 ⁻⁶ and ε = 8.30 × 10 ⁻³ . Here, ν is the kinematic viscosity of water, Ω is the angular velocity of the rotor 7 and the housing 8, and r _R is the radius of the cylindrical portion of the rotor 7.
And, as the raw material powder, true spherical particles of polymethyl methacrylate having a true specific gravity of 1.19 are used and added to water of a dispersion medium at a weight concentration of 0.50% to form a raw material slurry. The ratio of the raw material slurry flow rate Q _O to the total flow rate Q of the raw material slurry and water to which a small amount of liquid synthetic detergent is added as a dispersant, Q ₀ / Q, can be set to about 0.3 at the maximum. Since the smaller the value, the better the classification performance, the value was set to 0.113 in this experiment.
[0010]
The classification results obtained are as follows.
Here, in FIG. 3, the integrated distributions of the raw material slurry, fine product, and coarse product are indicated by R _O , R _F , and R _C , respectively. It should be noted that the coarse product R _C was not determined by direct measurement, but was determined from the raw slurry S _O , the fine product R _F, and the recovery η _F = 0.38 of the fine product R _F (R _{C = (R O -η F R F} ) / (1-η F)). The solid line in the figure indicates a polynomial approximation curve at the experimental point.
Next, FIG. 4 shows the partial classification efficiency Δη obtained from the frequency distribution obtained by differentiating the approximate polynomial in FIG. As a result, the 50% particle diameter D _P50 (classification point) was determined to be 4.3 μm, and the classification sharpness D _P25 / D _P75 (classification accuracy) was determined to be 1.52.
Subsequently, the result of numerical simulation of classification for the single-stage classification device 17 shown in FIG. 5 is shown below.
The classifier 17 includes a disk-shaped rotor 18 and a cylindrical tank-shaped housing 19 that rotate integrally at a high speed. Raw material slurry is supplied from an inlet 20. The fine-grained product is collected at the outlet 21, while the coarse-grained product is collected by adhering to the cylindrical inner peripheral wall of the housing 19.
The dimensional relationship of the main parts in the classifier 17 will be described below.
a: radius of the rotor 18 D _ha = 0.3a: the axis of the rotor 18 length R = 0.7a: inflow, radial D outlets 20,21 _h1 = D _h2 = 0.15a: the axis of the rotor 18 and the housing 19 Directional clearance width D ₁ = 0.3a: Radial clearance width between rotor 18 and housing 19
The flow field is obtained by directly numerically integrating the equation of motion of the incompressible viscous fluid (Navier-Stokes equation), and the trajectory of the particle is expressed by the equation of motion of the particle (Basset, Boussinesq-Oseen equation, Term and gravitational term are ignored).
FIG. 6 shows a quasi-rigid rotating stratified flow when the Ekman number E = ν / (Ωa ² ) is 1.67 × 10 ⁻⁵ and the Rossby number ε = U _O / (Ωa) is 1.67 × 10 ^−3. , The partial classification efficiency Δη obtained from the motion trajectories obtained for the spherical particles having various dimensionless diameters D _P ′ (= D _P / {a (Eε) ^0.5 }) is shown.
Here, ν is the kinematic viscosity of the fluid, Ω is the angular velocity between the rotor 18 and the housing 19, and U _O is the magnitude of the uniform radial velocity component at the inflow and outflow 20, 21. The density ratio ρ _p / ρ _f of the particles to the fluid was 1.19, and the initial velocity of the particles at the inlet 20 was the same as the velocity of the fluid there. Further, the supply positions of the particles (raw material slurry) at the inflow port 20 were five kinds of a to e shown in the figure. For example, in the case of the position b, the raw material slurry is supplied only in a range where the dimensionless axis coordinate z 'of the inlet 20 is from 0 (rotor wall) to 0.5 (center of the clearance), and from 0.5 to 1 (housing wall). ) Is supplied with a fluid containing no particles. Here, it is assumed that the particle size distribution of the particles contained in the raw slurry does not depend on z ′. As is clear from the figure, the classification accuracy _Dp25 / _Dp75 (= D' _p25 / D' _p75 ) is best at the position d where the raw material slurry is supplied only near the rotor wall, and the value of 1.10. In this case, the classification point D _p50 = (D ′ _P50 a (Eε) ^0.5 ) takes a value of 3.05a (Eε) ^0.5 .
[0012]
Next, a classifier 22 according to another embodiment of the present invention will be described with reference to FIG.
That is, the classifying device 22 changes a plurality of radial dimensions of the outer peripheral surface of the rotor 23 and the inner peripheral surface of the housing 24 in a stepwise manner (three steps in the present embodiment) toward the axis thereof, thereby providing a plurality of classifications. The classification chambers 25a, 25b, 25c are formed.
Then, a fluid (water) containing no particles is supplied to the Ekman layer on the housing 24 at the entrances of the classification chambers 25a, 25b, 25c of each stage. By mainly controlling the flow rate of this fluid, a stable quasi-rigid rotary stratified flow can be obtained in each of the classifying chambers 25a, 25b, and 25c.
Since the classifying apparatus according to the present embodiment is configured as described above, a quasi-rigid rotary stratified flow without any turbulence is generated in each classifying chamber, thereby classifying the raw material slurry. Specifically, sharp classification in the submicron region is possible. In particular, it is possible to completely prevent the coarse particles from being mixed into the fine product.
In the range of the Ekman number and the Rossby number at which a stable quasi-rigid rotating stratified flow can be obtained, the particle size to be classified can be freely adjusted by changing the rotation speed of the rotor and housing and the flow rate of fluid such as water. Can be controlled.
In addition, since only the number of revolutions and the flow rate are control variables, automatic control of the apparatus can be easily realized.
[0013]
【The invention's effect】
As described above, the present invention includes a substantially spherical rotor that rotates integrally and a housing that includes the rotor therein, and a gap having a different particle size is provided in a gap between the surface of the rotor and the inner peripheral wall surface of the housing. A fluid containing particles is continuously supplied, and a fluid containing particles having a relatively small particle size is communicated with the gap based on a difference in centrifugal force applied to the particles caused by a difference in size of the particles. A classifier that rotates the rotor and the housing at a speed at which a quasi-rigid rotary flow is generated, and collects coarse particles by adhering to the inner peripheral wall surface of the housing. Therefore, it is possible to completely prevent coarse particles from being mixed into fine products without causing disturbance of the fluid in the classification chamber, and to perform high-precision classification.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a classification device according to an embodiment of the present invention.
FIG. 2 is an enlarged view of a main part in FIG.
FIG. 3 is a graph showing a classification result by the classification device.
FIG. 4 is a graph showing a partial classification efficiency obtained based on the classification result in FIG. 3;
FIG. 5 is a schematic diagram of a classification device for explaining a numerical simulation of classification.
FIG. 6 is a graph showing a partial classification efficiency obtained from a motion trajectory obtained for a spherical particle in a quasi-rigid rotating stratified flow under a predetermined condition.
FIG. 7 is a schematic configuration diagram of a classification device according to another embodiment of the present invention.
[Explanation of symbols]
1, 17, 22 ... Classifier 7, 18, 23 ... Rotor 8, 19, 24 ... Housing 9, 25a, 25b, 25c ... Classification room

Claims (3)

A substantially spherical rotor that rotates integrally and a housing containing the rotor therein , and a fluid containing particles having different particle sizes is continuously supplied to a gap between a surface of the rotor and an inner peripheral wall surface of the housing. A classifying device for supplying and discharging a fluid containing particles having a relatively small particle size from a discharge hole communicating with the gap based on a difference in centrifugal force applied to the particles caused by a difference in size of the particles. A classifier , wherein the rotor and the housing are rotated at a speed at which a quasi-rigid rotating flow is generated, and coarse particles are attached to and collected on the inner peripheral wall surface of the housing . 2. The classifying apparatus according to claim 1, wherein a plurality of classifying chambers are configured by making each radial dimension of an outer peripheral surface of the rotor and an inner peripheral surface of the housing vary stepwise along the axial direction. The classifier according to claim 1 or 2, wherein the rotor and the housing are operated under the condition of ε ≦ 1.59E ^0.46 (ε: Rossby number, E: Ekman number).

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