JPH0722719B2 - Particle classification method and apparatus - Google Patents

Description

TECHNICAL FIELD The present invention relates to a particle classification method and apparatus used in the powder industry in general, such as cement industry, chemical industry, and ceramic industry.

2. Description of the Related Art Conventionally, in general, this type of method and apparatus applies two or more types of forces such as gravity, wind force, and centrifugal force to particles suspended in a space in a fixed direction and a direction perpendicular thereto, and as a result, , It is usual to classify by utilizing the difference generated in the spatial trajectory of particles.

Problems to be Solved by the Invention However, the above-mentioned conventional method and apparatus have the following problems. That is, the wind force inevitably causes non-uniform air flow distribution and orbital disturbance of particles due to air flow fluctuations, which inevitably limits the classification accuracy.

In addition, the error of classification accuracy becomes particularly large in the fine powder region where the wind force (air viscosity) is stronger than the acting force such as centrifugal force, and therefore the lower limit that cannot be exceeded in the classification particle size (limit particle size). Cause This lower limit is around 5 μm even with the current highest performance devices.

The present invention has been made to solve such a problem, and an object thereof is to provide a particle classification method and apparatus with higher accuracy than the conventional particle classification methods described above.

Means for Solving the Problems With reference to the drawings showing an embodiment of the present invention, first, regarding the apparatus in FIGS. 1 and 7, an electrode group 2 composed of a plurality of linear electrodes 1 arranged in parallel, This is a particle classifying apparatus in which at least two sets are polymerized, the linear electrodes 1 are insulated from each other and crossed, an AC power source 3 is connected between the electrode groups 2, and an electric field matrix 4 is formed. As a particle classification method, particles to be classified are supplied to the electric field matrix.

The AC power supply 3 may be a single-phase AC power supply as shown in FIG. 1 or a three-phase AC power supply as shown in FIG. 5 or FIG. It may be a multi-phase AC power source including. Further, the crossovers of the linear electrodes 1 may be simply polymerized as shown in FIG. 6, or as shown in FIG. 1, the positions of the linear electrodes 1 of another electrode group 2 may be alternately changed in the vertical direction. May be done. That is, it may be woven. Also, preferably, FIG.
As shown in FIG. 14, a path 5 for supplying particles communicating with the electric field matrix 4 is provided with a charging device 6 for giving an electric charge to the particles, but this may be omitted as will be described later. Further, the electric field matrix 4 may be provided in a pressure higher than the atmosphere, or may be provided in a gas other than air or a mixed gas of the same gas and air.

The particles to be classified are charged as they are or charged by the particle charging device 6, and are supplied to the electric field matrix 4 by wind force, gravity or the like. The particles to be classified approach the electric field matrix 4 and have been precharged by contact charging or by the charging device 6, while the electric field matrix 4 forms the electric field as described above, and FIGS. The lines of electric force 7 as shown in are generated. The lines of electric force 7 are alternating in direction. Therefore, among the supplied particles, the particles 8 having a particle size larger than a certain particle size are
As a result of the charging, as shown in FIG. 3, the electric field line 7 has an arcuate shape and vibrates along the electric field line 7, resulting in arrow A8.
It is subjected to a directional centrifugal force and is therefore suspended above the electric field matrix 4 in FIG. On the other hand, the particles 8
Since the surface area of the particle 9 is smaller than that of the particle 8, the amount of electric charge is smaller than that of the particle 8. Therefore, the electromotive force of the electric field matrix 4 as described above is less likely to occur, and therefore the electrodynamics of the electric field is weaker. Through the target pore 10. In this way, classification is performed. Further, as shown in FIG. 5, the one using a three-phase AC power source as the AC power source 3 can form a so-called traveling wave type electric field curtain in the electric field matrix 4, and for example, particles 8 suspended on the electric field matrix 4 as described above. Can be moved in the direction of the phase sequence.
This would speed up the collection of particles that were blocked from passing.

Example FIGS. 8 and 9 show a twill weave electric field matrix, and FIGS. 10 and 11 show a satin weave electric field matrix 4. These also show standing wave type electric field matrices. As the linear electrode 1, for example, an electric wire coated with an insulator such as Teflon or polyethylene is used.

What is shown in FIG. 12 is a classifying device in which a standing wave type electric field matrix 4 is formed in a cylindrical shape and a corona discharge electrode 6a and a counter electrode 6b are provided as a charging device 6 on the upper part. The raw material enters through the mouth portion 11 and is charged by the charging device 6, of which particles 9 having a particle size smaller than a certain size pass through the electrodynamic pores 10 of the electric field matrix 4,
Collected as a product from the outlet 12. On the other hand, the particles 8 larger than the particles 9 which are strongly affected by the blocking force of the electric field matrix 4 descend by gravity and are discharged from the discharge port 13. In this classification, the sieving of particles (so-called classification point) can be adjusted by changing the alternating voltage and frequency applied to the electric field matrix 4. The electric field matrix 4 may be applied by superimposing a DC voltage on an AC voltage.

In the structure shown in FIG. 14, the electric field matrix 4 is formed in a flat shape and is inclined, and the particles 8 which are strongly subjected to the electrodynamic blocking force descend on the electric field matrix 4 and enter the hopper 14, The smaller particles 9 pass through the electrodynamic pores 10 and enter the product hopper 15 for classification. The one shown in FIG. 15 enters the preliminary charging section 18 from the raw material hopper 16 through the feeder 17 and detects its concentration with the dust densitometer 20 before entering the charging section 19, and feed back its output to the feeder 17. Charged part 19
To keep the dust load on the surface constant. The particles charged by the charging unit 19 enter the classification chamber 21 provided with the electric field matrix 4, and the particles passing through the electrodynamic pores 10 are collected by the electrostatic precipitator 22. The particles not collected are sent again to the feeder 17. Since this device is a closed circuit system, it can be set in a high pressure environment, and the electric field matrix 4 can be operated at a sufficiently high voltage. Therefore, it is possible to expect classification characteristics under the environment of high-pressure air as shown in FIG.

FIG. 16 to FIG. 18 are explanatory views of the preliminary charging unit 18 in FIG. 15, and as shown in FIG. 18, the surface of the coated electrode to which a voltage is applied has a positive or negative potential. And several sets of uncharged particles come into contact with such a charged layer to become charged particles. Therefore, as shown in FIG. 17, the electric field matrix 4 is formed in a roll shape in many layers, and is provided in the casing 23 shown in FIG. 16 so that the uncharged particles entering from the inlet 11 exit from the outlet 12. By the time it becomes a particle with a certain amount of charge. This is the precharge of the particles,
It has become possible to improve the dispersion of the raw material powder in order to improve the classification accuracy.

EFFECTS OF THE INVENTION Since the present invention is configured as described above, it is possible to provide a classification method and apparatus having higher classification accuracy than the conventional method.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, showing an outline of a particle classifier, FIG. 2 is a view taken along the line II-II of FIG. 1, and FIG. 3 is a principle explanatory view of the present invention. FIG. 4 is a diagram for explaining the principle of the present invention, FIG. 5 is a diagram showing a second embodiment of the present invention and corresponding to FIG. 2, and FIG. 6 is a diagram showing the third embodiment of the present invention. FIG. 7 is a perspective view of a part, FIG. 7 is a view corresponding to FIG. 1 showing the fourth embodiment, FIG. 8 is a view showing the fifth embodiment, a view corresponding to FIG. 1, and FIG. 8 is a view taken along the line IX-IX of FIG. 8, FIG. 10 shows a sixth embodiment of the present invention, and is a view corresponding to FIG. 1, and FIG. 11 is a view taken along the line XI-XI of FIG. , 12th
FIG. 7 is a sectional view of a particle classifier showing a seventh embodiment of the present invention, FIG. 13 is a sectional view taken along line XIII-XIII of FIG. 12, and FIG. 14 is an eighth embodiment of the present invention. Figure corresponding to Figure 12,
FIG. 15 is a view showing the outline of a particle classifying apparatus according to the ninth embodiment, FIG. 16 is a detailed sectional view of a preliminary charging section 18 of the apparatus shown in FIG. 15, and FIG. 17 is a XVII of FIG. -XVII line sectional view, 18th
17 is an explanatory view of the operation of the device shown in FIG. 17, and FIG. 19 is a graph showing an example of expected classification characteristics when the device shown in FIG. 15 is operated. 1 ... Linear electrode 2 ... Electrode group 3 ... AC power supply 4 ... Electric field matrix

Claims (14)

[Claims] 1. An electrode group consisting of a plurality of linear electrodes arranged in parallel, at least two sets of which are superposed, and the linear electrodes of each set are insulated and crossed from each other, and an AC voltage is applied between the electrode groups. A particle classification method, which comprises applying an electric field matrix to supply particles to be classified to the electric field matrix. 2. The method for classifying particles according to claim 1, wherein the crossing of the linear electrodes is performed by alternating the positions of the linear electrodes of other electrode groups in the vertical direction. 3. The particle classification method according to claim 1, wherein the particles to be classified to be supplied are charged. 4. The particle classification method according to claim 1, wherein the AC voltage is a single-phase AC voltage whose frequency and / or applied voltage can be varied. . 5. The particle classification method according to claim 1, wherein the AC voltage is a polyphase AC voltage capable of varying one or both of frequency and applied voltage. . 6. The particle classification method according to any one of claims 1 to 5, wherein the electric field matrix is provided in a gas having a pressure higher than atmospheric pressure. 7. The electric field matrix according to claim 1, wherein the electric field matrix is provided in a gas other than air, or in the atmosphere in which the gas and air are mixed. Particle classification method. 8. An electrode group consisting of a plurality of linear electrodes arranged in parallel is overlapped with at least two sets, and the linear electrodes of each set are insulated and crossed from each other, and an AC power supply is provided between the electrode groups. A particle classifier, which is connected to form an electric field matrix. 9. The particle classifying apparatus according to claim 8, wherein the crossing of the linear electrodes is made to alternate with the linear electrodes of another electrode group in the vertical direction. 10. The particle classification device according to claim 8, wherein the electric field matrix has a particle supply passage communicating with the particle charging device. 11. The particle classifying apparatus according to claim 8, wherein the AC power supply is a single-phase AC power supply capable of varying one or both of frequency and applied voltage. . 12. The particle classification device according to claim 8, wherein the AC power supply is a multi-phase AC power supply capable of varying one or both of frequency and applied voltage. . 13. The particle classifying apparatus according to claim 8, wherein the electric field matrix is provided in a gas having a pressure higher than atmospheric pressure. 14. The electric field matrix is provided in a gas other than air or in a mixed gas of the same gas and air, according to claim 8.
Item particle classifier.