JPH08238456A - Gas flow classifying method and gas flow classifying apparatus - Google Patents

Abstract

PURPOSE: To efficiently carry out gas classification for a raw material to be classified at high precision by selecting and taking particles with a prescribed particle size or higher from the raw material to be classified before the gas flow classification for the raw material. CONSTITUTION: After a raw material 15 to be classified is gathered in a dust collecting apparatus 32, the raw material is supplied to a vibration sieve 40 and particles with a prescribed particle size or higher are removed from the raw material 15 to be classified and the removed particles are sent to a pulverizing apparatus 50 through a pipe 42 and a treatment to make particle size small is carried out. Meanwhile, the raw material 15 which passes the vibration sieve 40 is sent to a pipeline 35 through a hopper 33 and a quantitative feeder 34, and in such a state that the raw material is mixed with compressed air, the raw material 15 is sprayed by a material feed nozzle 16 to a raw material selecting chamber of a gas flow classifier 1 and classified by air current. Particles with smaller particle size than that of particles to become products are collected as a fine powder by a dust collector 36, particles which become products are collected as a middle powder by a dust collector 37, and particles with larger particle size than that of the particles to become products are collected as a rough powder by a dust collector 38.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air flow classification method and air flow classification device for classifying a raw material to be classified in which particles having various particle sizes are mixed according to the particle size by utilizing the Coanda effect. The present invention relates to a technique for improving the accuracy of classifying a classification material.

[0002]

2. Description of the Related Art A raw material which has been made into fine particles by a pulverization process is usually in a state in which particles having various particle sizes are mixed, from coarse particles to very fine particles. Therefore, when the finely divided raw material is industrially used, the raw material after the pulverization treatment is subjected to a so-called classification treatment so that the raw material is classified according to the particle diameter in a desired range. The classification here means that particles moving in a fluid by gravity, centrifugal force, or inertial force can differ in settling velocity or particle path depending on the particle diameter, and therefore the particles are classified according to their size. For example, in the case of producing powder such as toner for a copying machine, the toner raw material mixed with particles of various particle diameters is jetted into the air flow, and it depends on the particle diameter generated by the Coanda effect. Airflow classifiers are widely used that classify toner raw materials by particle size by utilizing the difference in the scattering and descending paths.

FIG. 6 schematically shows a conventional example of such an air flow classifier. This airflow classifier 1 is the first
Also, three classification exhaust flow paths 7, 8 and 9 branched by the second classification edges 2 and 3 and the Coanda block 4 and the back block 5 are opened on the outlet side of the chamber and two A raw material sorting chamber 14 having air passages 11 and 12 opened on the inlet side of the chamber, and an air flow formation (not shown) for generating air flows from the air inlet passages 11 and 12 toward the exhaust passages 7, 8, and 9. Means (for example, an exhaust fan) and compressed gas 19
A raw material supply nozzle 16 for pumping and injecting the classified raw material 15 is provided in the raw material selection chamber 14 using (usually compressed air).

Here, the raw material 15 to be classified is supplied to the raw material supply nozzle 16 and dispersed by the compressed gas flow 19 supplied to the raw material supply nozzle 16 to form a solid-gas mixed phase flow from the raw material supply nozzle 16. It is injected into the raw material sorting chamber 14. The jet flow containing the classified raw material 15 injected from the raw material supply nozzle 16 into the raw material selection chamber 14 is
It flows along the Coanda block 4 by the Coanda effect,
Centrifugal force acts on the material to be classified 15, and the relatively coarse particles in the material 15 to be classified jump out from the jet stream flowing along the Coanda block 4. Outside the jet flow that flows along the Coanda block 4, airflows flowing from the intake air flow paths 11 and 12 to the exhaust flow paths 7, 8 and 9 flow,
The relatively coarse particles in the raw material to be classified 15 that have jumped outward from the jet flow that flows along the exhaust gas flow path 7 corresponding to each predetermined particle size range due to the difference in the scattering paths that are different for each particle due to this air flow. It is designed to be separated and discharged into 8 and 9.

The particle descending path on which the Coanda effect acts has a larger curvature as the particle size is smaller and the inertia is smaller, and scatters and descends along the air flow contact surface of the Coanda block 4 and is closest to the Coanda block 4. It is discharged to the road 7. On the other hand, the larger the particle size and the larger the inertia, the smaller the curvature of the scattering descending path, and the scattering descends further away from the Coanda block 4,
Is discharged to the exhaust flow path 9 furthest from. As a result, the exhaust flow paths 7, 8 and 9 are used for discharging fine powder in which the exhaust flow path 7 closest to the Coanda block 4 is made of particles having a small particle size.
The exhaust passage 9 farthest from the raw material supply nozzle 16 is for discharging coarse powder of particles having a large particle diameter, and the exhaust passage 8 located in the middle is for discharging intermediate powder having an intermediate particle diameter. Then, the classified raw material 15 discharged to each of the exhaust flow paths 7, 8 and 9
Are respectively collected by dust collectors (not shown) connected to the respective exhaust flow paths 7, 8, 9 via the conduits 21, 22, 23, and thus separated into powder and air.

[0006]

By the way, in order to improve the accuracy of classifying the material to be classified, as shown schematically in FIG. 7, the larger the particle size, the larger the Coanda block 4 is.
It is necessary to make the particles fall as far away as possible from the above, and to make the particles having a smaller particle diameter fly closer to the Coanda block 4. Further, it is necessary that the particles contained in the raw material 15 to be classified do not agglomerate with each other, and that the particles are reliably dispersed and injected from the raw material supply nozzle 16 into the raw material selection chamber 14. Therefore, by increasing the ejection speed of the compressed air flow 19 for injecting the classified raw material 15 from the raw material supply nozzle 16 into the raw material selection chamber 14, the shearing force generated in the compressed air flow 19 is increased and the classified raw material 15 is dispersed. It is necessary to improve sex.

However, when the jetting speed of the compressed air stream 19 for injecting the classified material 15 from the material supply nozzle 16 into the material selection chamber 14 is increased, the particles contained in the classified material 15 as shown in FIG. Some large particles or agglomerates that behave similarly to large particles collide with the back block 5 and bounce off to enter the exhaust passage 8 for discharging medium powder and the exhaust passage 7 for discharging fine powder. There is. Therefore, for example, when the intermediate powder taken out through the conduit 22 communicating with the exhaust passage 8 is used as a product, particles or large agglomerates having a large particle diameter deviating from a predetermined particle diameter range are mixed in the product. As a result, the grain quality of the product is impaired.

Further, as shown schematically in FIG. 8, when the particle size range of the particles contained in the material to be classified 15 is much wider than the particle size range of the product particles, the product particles are Since the narrow area shown by hatching in FIG. 8 is scattered and descended, the interval between the first and second classification edges 2 and 3 must be set narrow, and the efficiency of collecting product particles is improved. Is greatly reduced. In addition, the material to be classified 15
When a large number of particles having a particle size larger than the particle size range of the particles to be the product are contained, the scattering and falling of the particles to be the product in the raw material sorting chamber 14 are obstructed, and a predetermined exhaust flow is generated. The airflow cannot be entered into the passage 8, and the accuracy of the airflow classification is deteriorated due to the turbulence of the airflow. Also,
In the deflection of the medium powder and the fine powder in the classification area, FIG.
As shown in FIG. 3, the coarse powder L having a relatively large particle diameter collides with the medium powder M or the fine powder S having a smaller particle diameter than the coarse powder L, so that the medium powder M or the fine powder S should have the desired shape. Dispersion route is obstructed. As a result, there is a problem that the classification accuracy is deteriorated, for example, fine powder is mixed in the medium powder side or medium powder or fine powder is mixed in the coarse powder side. The arrows in the figure indicate the scattering direction of each particle.

When the particle size range of the particles contained in the material to be classified 15 is larger than the particle size range of the product particles, the product particles approach the Coanda block 4. As shown in FIG. 8, the first and second classification edges 2.3 must be inclined so that their tips approach the Coanda block 4, as shown in FIG. In this case, the first and second classification edges 2
As shown in FIG. 9, the material No. 3 extends obliquely with respect to the air flow flowing in the raw material sorting chamber 14, so that the classification edge 2
Particles collide with the upstream side surface of 3 and the side surface is worn or particles are attached. Furthermore, since a vortex flow is generated on the downstream side of the classification edges 2 and 3, in the case of a raw material having a large cohesive force, secondary cohesive lumps are generated and the particle size quality of the product is deteriorated.

Therefore, an object of the present invention is to solve the above problems, and even when the classified raw material 15 contains many particles having a particle size larger than the particle size of the product particles, An object of the present invention is to provide an airflow classifying method and an airflow classifying apparatus which enable particles as products to be scattered and dropped in a wide range in a raw material selection chamber, and thereby efficiently classify raw materials to be classified with airflow with high accuracy.

[0011]

The above object of the present invention is to eject an air stream containing a raw material to be classified along a curved and extending air flow contact surface of a Coanda block so that the particles contained in the raw material to be classified have a coanda content. In the air flow classification method of classifying the particles according to the size of the particle size by operating the effect,
This can be achieved by an air stream classification method characterized in that particles having a particle size larger than a predetermined particle size are selected and taken out from the material to be classified before the air classification of the material to be classified.

Further, the above object of the present invention is to provide a raw material sorting chamber, an inlet air passage communicating with the raw material sorting chamber and a plurality of branched exhaust passages, and a curved air flow contact surface protruding into the raw material sorting chamber. An air flow classifier equipped with an air flow classifier having a Coanda block having an air flow contact surface and a raw material supply nozzle for forming an air flow in which a raw material to be classified is placed on a flow of a compressed gas ejected into the raw material selection chamber along the air flow contact surface. In the apparatus, it is achieved by an air stream classifying device characterized by comprising a selecting means for selecting and extracting particles having a particle size larger than a predetermined particle size from the material to be classified before air classifying the material to be classified. be able to.

[0013]

In the airflow classification method and the airflow classification apparatus of the present invention, particles (including agglomerates) having a particle diameter larger than a predetermined particle diameter are removed from the material to be classified in advance, and then the material to be classified is subjected to airflow classification. Therefore, the particles to be the product can be stably scattered and lowered over a wide range in the raw material sorting chamber of the air stream classifier. As a result, the spacing between the classification edges can be widened, so that the material to be classified can be efficiently and highly accurately classified by air flow.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of an airflow classifying method and an airflow classifying apparatus according to the present invention will be described in detail below with reference to the drawings. Here, FIG. 1 is a drawing schematically showing the overall configuration of an airflow classifying device according to a first embodiment of the present invention, FIG. 2 is a block diagram explaining the operation of the airflow classifying device shown in FIG. 1, and FIG. 5 is a drawing schematically showing the operation of the airflow classifier in the airflow classifying apparatus shown in FIG. 4, FIG. 4 is a drawing schematically showing the overall configuration of the airflow classifying apparatus of Example 2 according to the present invention, and FIG. 5 is an airflow shown in FIG. It is a block diagram explaining operation of a classification device. In the following description, the same parts as those of the conventional airflow classifier are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 1, the airflow classifying apparatus 100 of the present embodiment includes a raw material 1 to be classified 1 supplied through a pipe 31.
5, a dust collector 32 for collecting the dust 5, a vibrating sieve 40 as a selecting means interposed between the dust collector 32 and the hopper 33 for supplying the classified material to the air stream classifier 1, and the air stream classifier 1, Dust collectors 36, 37, 38 for collecting the particles classified by the air flow classifier 1 are provided.

The vibrating screen 40 removes particles having a particle size larger than a predetermined particle size contained in the material 15 to be classified, for example, an open path type electromagnetic screen (Soniclean manufactured by Shinto Kogyo Co., Ltd.) or the like. Can be preferably used. Then, by appropriately setting the cut point in the vibrating screen 40, particles having a particle size larger than a predetermined particle size can be selected and removed from the classified raw material 15. The removed particles are sent to the crusher 50 through the pipe 42 and subjected to a treatment for reducing the particle size. On the other hand, particles having a particle size smaller than the particle size set as the cut point pass through the vibrating sieve 40 and are supplied to the hopper 33.

Next, the operation of the airflow classification device 100 of the first embodiment will be described with reference to FIGS. 1 and 2. First, the classified material 15 is collected in the dust collector 32 via the pipe 31, and then supplied to the vibrating screen 40. Then, particles having a particle size larger than a predetermined particle size are vibrated with a sieve 4.
0 is removed from the raw material 15 to be classified and is sent to the crusher 50 via the pipe 42 to be subjected to a treatment for reducing the particle size. On the other hand, the material 1 to be classified which has passed through the vibrating sieve 40
5 is sent to the hopper 33 via the pipe line 41 and stored therein,
The fixed amount is sent to the pipe 35 by a fixed amount per unit time. Then, the raw material supply nozzle 1 is mixed with the compressed air 19 supplied into the pipe 35.
6 is jetted into the raw material sorting chamber 14 of the airflow classifier 1. Then, the classified raw material 15 is subjected to air flow classification by the air flow classifier 1, and particles having a particle size smaller than that of the product particles are made into the dust collector 36 as fine powder, and the product particles are made into the dust collector 37 as the intermediate powder. Particles having a larger particle size than the particles are collected by the dust collector 38 as coarse powder.

The coarse powder collected by the dust collector 38 is sent to the crusher 50 via the pipe 39, and is crushed by the vibrating sieve 40 together with the particles removed from the material to be classified to reduce its particle size. Processing is performed. And the conduit 51
After being taken out of the crusher 50 via the crusher, it is supplied to the dust collector 32 together with the newly supplied classified material 15.

At this time, the raw material to be classified 15 which is jetted from the raw material supply nozzle 16 into the raw material sorting chamber 14 of the air stream classifier 1
Does not include particles having a particle size larger than a predetermined particle size. Therefore, particles having a large particle size do not collide with the rear surface block 5 and bounce back, and do not jump into the exhaust passage 8 for the intermediate powder, so that the particle size quality of the intermediate powder taken out as a product is not impaired.

Further, as shown in FIG. 3, the material to be classified 15 from which particles having a particle diameter larger than a predetermined particle diameter have been removed.
The largest particle contained in the back block 5
The material supply nozzle 16 so that it comes closest to
By adjusting the ejection speed of the classified material 15 from the above, the width in which the particles in the target particle size range scatter and descend in the material selection chamber 14 can be widened. As a result, the interval between the first and second classification edges 2 and 3 can be widened, so that the accuracy of classifying the material 15 to be classified can be improved, and the particle size quality of the intermediate powder as a product can be improved. be able to.

Furthermore, since the inclination of the classification edges 2.3 can be set so as to extend in parallel to the direction of the air flow, eddy currents are prevented from being generated on the downstream side of the classification edges 2.3. be able to. As a result, it is possible to prevent deterioration of the particle size quality of the product due to turbulence of the air flow. Further, it is possible to prevent particles from colliding with each other on the upstream side surfaces of the classification edges 2 and 3 to cause abrasion or particles to adhere, so that the airflow classification can be stably performed for a long time. .

Second Embodiment Next, an airflow classifying apparatus and an airflow classifying method according to a second embodiment of the present invention will be described with reference to FIGS. 4 and 5. In the vibrating sieve 40 used in the airflow classification device 100 of the above-described Example 1, the screen gradually becomes clogged due to long-term use, and the particle size of the particles removed from the material to be classified 15 becomes gradually smaller. , Vibrating sieve 40
The amount of the classified raw material 15 that passes through the hopper and is supplied to the hopper 33 decreases.

Therefore, as shown in FIG. 4, in the airflow classifying device 200 of the second embodiment, the airflow classifying device 100 of the first embodiment is provided with a pipe line 60 that bypasses the vibrating sieve 40.
A damper 61 for switching the pipeline with an opening sensor is newly added. When the sensor (not shown) detects that the supply amount of the classified material 15 from the vibrating sieve 40 to the hopper 33 per unit time is lower than the specified value, the controller (not shown) also operates the damper 61. The classified raw material 15 supplied from the dust collector 32 is directly supplied to the hopper 33 through the pipe 60, and the amount of the classified raw material 15 supplied to the hopper 33 per unit time is kept constant. Then, when the opening degree of the damper 61 exceeds a specified value, an alarm is issued to notify that the screen of the vibrating screen 40 is clogged. Therefore, the second embodiment
According to the airflow classifying device of No. 3, even if the screen of the vibrating sieve 40 is clogged, the amount of the classified material 15 supplied to the airflow classifier 1 does not decrease sharply.
The airflow classification process can be performed stably.

The airflow classifying method and the airflow classifying apparatus of the present invention are not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made based on the gist of the present invention. For example, in Example 1 and Example 2 described above, a vibrating sieve is used as a selecting means for selecting particles having a particle size larger than a predetermined particle size from the classified material 15 in the vibrating screen. Instead, an air stream classifier or a cyclone can be used as the sorting means.

Further, the air flow classification as described in the specification of the "air flow classification device" (see Japanese Patent Publication No. 5-41317 and Japanese Patent Publication No. 5-73476) previously invented by the applicant of the present invention. In the machine, sampling means for sampling the air-flow classified particles, particle size measuring means for measuring the particle size of the sampled particles, weight measuring means for measuring the weight of the air-flow classified raw material, and the particles Control means for controlling the operation of the sorting means based on the information obtained from the diameter measuring means and the weight measuring means are added. Then, by the control means, for example, by switching a plurality of filters having different cut points provided in the vibrating sieve, or by operating the angle of the classification edge of the airflow classifier as the selection means, it is supplied to the airflow classifier. It becomes possible to control the maximum value of the particle size of the particles contained in the classified material. As a result, not only can the operation of the airflow classification device be automated, but the accuracy of airflow classification of the material to be classified can be further improved.

[0026]

As described above, in the airflow classification method and airflow classification apparatus of the present invention, particles and agglomerates having a particle size larger than a predetermined particle size are removed from the material to be classified in advance and then classified. Since the raw material is classified by air flow, among the particles having various particle sizes contained in the material to be classified, particles having a particle size to be a product can be scattered and dropped over a wide range in the raw material selection chamber of the air flow classification device.
As a result, the spacing between the classification edges can be widened, so that the material to be classified can be efficiently and highly accurately classified by air flow. Further, since the inclination of the classification edge can be arranged along the flow of the air flow, and the turbulence of the air flow near the classification edge can be prevented, it is possible to prevent the particle size quality of the product from being deteriorated. . Furthermore, it is possible to prevent particles from colliding with the upstream side surface of the classification edge and causing abrasion to the classification edge, or to prevent the particles from adhering, so that airflow classification can be performed stably for a long time. it can. Therefore, according to the present invention, it is possible to provide an airflow classifying method and an airflow classifying apparatus capable of efficiently classifying a material to be classified by airflow with high accuracy.

[Brief description of drawings]

FIG. 1 is a drawing schematically showing an overall configuration of an airflow classification device according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating an operation of the airflow classification device shown in FIG.

FIG. 3 is an explanatory view schematically showing the operation of an airflow classifier in the airflow classifier shown in FIG.

FIG. 4 is a drawing schematically showing the overall configuration of an airflow classification device of Example 2 according to the present invention.

5 is a block diagram illustrating an operation of the airflow classifier shown in FIG.

FIG. 6 is a vertical sectional view of an airflow distributor.

FIG. 7 is an enlarged view of a main part schematically showing the problem of the airflow classifier shown in FIG.

FIG. 8 is an explanatory view schematically showing the operation of the airflow classifier shown in FIG.

9 is a block diagram illustrating the operation of the airflow classifier shown in FIG.

FIG. 10 is a schematic diagram showing a state where coarse powder prevents deflection of medium powder and fine powder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Air flow classifier 2, 3 classification edge 4 Coanda block 5 Back block 7, 8, 9 Exhaust flow path 11, 12 Inlet air flow path 14 Raw material selection chamber 15 Classified raw material 16 Raw material supply nozzle 19 Compressed air flow 21, 22, 23 , 24 Pipe lines 32, 36, 37, 38 Dust collector 33 Hopper 34 Quantitative feeder 40 Vibrating sieve (sorting means) 50 Crusher 100 Airflow classifier of Example 1 200 Airflow classifier of Example 2

Claims (9)

[Claims] 1. An air stream containing a raw material to be classified is jetted out along a curved air flow contact surface of a Coanda block, and the particles contained in the raw material to be classified are subjected to a Coanda effect so that the particle diameter of the particles is increased. In the airflow classification method of classifying according to the size of, before the airflow classification of the material to be classified, characterized in that the particles having a particle size larger than a predetermined particle size is selected and taken out from the material to be classified Airflow classification method. 2. The air stream classification method according to claim 1, wherein the particles extracted from the material to be classified by the screening are subjected to a treatment to further reduce the size thereof, and then the particles are returned into the material to be classified for air stream classification. . 3. A raw material sorting chamber, an inlet air flow passage communicating with the raw material sorting chamber and an exhaust flow passage branched into a plurality, a Coanda block having a curved air flow contact surface protruding into the raw material sorting chamber, An air flow classifier equipped with an air flow classifier having a raw material supply nozzle that forms an air flow in which a raw material to be classified is placed on a flow of a compressed gas ejected along the air flow contact surface into the raw material selection chamber, An airflow classifying device comprising a selecting means for selecting and extracting particles having a particle size larger than a predetermined particle size from the raw material to be classified before the airflow classification. 4. A means for carrying out a treatment for reducing the particle diameter of the particles taken out by the selecting means, and a transfer means for returning the particles having the reduced particle diameter into the material to be classified. The airflow classification device according to claim 3. 5. The airflow classifying apparatus according to claim 3, wherein the sorting means is a vibrating screen. 6. The airflow classifying apparatus according to claim 5, further comprising a bypass supply means for bypassing the vibrating screen and supplying the material to be classified to the airflow classifier. 7. Switching means for switching the material to be classified supplied to the vibrating screen to the bypass supply means side,
The measuring means for measuring the weight of the raw material to be classified passing through the vibrating screen, and the control means for controlling the switching means based on the information obtained from the measuring means. Airflow classifier. 8. The airflow classifying apparatus according to claim 3, wherein the sorting means is an airflow classifier. 9. A sampling means for sampling the particles classified by the airflow classifier, a particle size measuring means for measuring the particle size of the sampled particles, and a weight of the classified material classified by the airflow. The air flow classification according to claim 3, further comprising: a weight measuring unit; and a control unit that controls the operation of the sorting unit based on the information obtained from the particle size measuring unit and the weight measuring unit. apparatus.