JPH0999274A - Airflow classification method and device - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent the deterioration of the classification accuracy by preventing the diffusion that occurs when the material to be classified is jetted into the classification chamber. [Structure] A sub-nozzle 30 is provided above a raw material supply nozzle 22 from which a compressed air flow is ejected. Due to the air curtain formed by this compressed air flow, the classified raw material 21 ejected from the raw material supply nozzle 22 into the raw material selection chamber 18 can be prevented from being pressed and diffused toward the exhaust flow paths 15, 16, 17 side. . Therefore, since the material to be classified 21 is normally classified by the Coanda effect,
It is possible to prevent the classification accuracy from decreasing.

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 classified raw material in which particles having various particle sizes are mixed according to the particle size by utilizing the Coanda effect. The present invention relates to an airflow classification method and device capable of 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 various particles from coarse particles to very fine particles are mixed. Therefore, when the finely divided raw material is industrially used, the raw material after the pulverization treatment is subjected to so-called classification treatment to classify the raw material according to the particle diameter in a desired range.

The classification here means that particles that move in a fluid by gravity, centrifugal force or inertial force can be differentiated by utilizing the fact that the sedimentation velocity or the particle path can be varied depending on the particle diameter. For example, in the case of producing powder such as toner for a copying machine by a method of sorting by particle size, a toner raw material in which particles of various particle sizes are mixed is jetted into an air stream to separate the toner raw material by particle size. Airflow classifiers for classification are widely used.

FIG. 5 is a sectional view of a conventional airflow classifier 100. In this airflow classifier 100, three classification exhaust flow paths 107, 108, and 109 branched by the first and second classification edges 102 and 103, the Coanda block 104, and the back block 105 are located in the raw material selection chamber 114. It is provided on the outlet side and has two intake paths 111, 11
2 is provided on the inlet side of the raw material sorting chamber 114, and the exhaust passages 107, 108 from the intake paths 111, 112,
An air flow forming means (not shown) such as an exhaust fan for generating an air flow flowing toward 109 and compressed gas (usually compressed air) are used to pressure-feed the classified raw material 115 into the raw material selection chamber 114, The material supply nozzle 116 for jetting is provided.

The jet containing the classified raw material 115 injected from the raw material supply nozzle 116 into the raw material selection chamber 114 flows along the Coanda block 104 due to the Coanda effect, and centrifugal force acts on the classified raw material 115 to cause the centrifugal separation. The relatively coarse particles in the classification raw material 115 are due to the Coanda block 1
Jump out from the jet flow along 04. On the outside of the airflow flowing along the Coanda block 104, the exhaust flow paths 107, 108, 109 from the intake flow paths 111, 112 are provided.
The raw material to be classified 1 which has flown toward the outside and has flown out from the jet flowing along the Coanda block 104 toward the outside.
The relatively coarse particles in 15 are separated and discharged to the corresponding exhaust flow paths 107, 108, 109 for each predetermined particle size range due to the difference in the different scattering paths for each particle due to this air flow.

That is, the particle scattering and 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 airflow contact surface of the Coanda block 104 and is closest to the Coanda block 104. It is discharged to the exhaust passage 107. On the other hand, the larger the particle size and the larger the inertia, the smaller the curvature of the scattering descent path,
The exhaust flow path 1 which is the farthest from the Coanda block 104 is scattered and descends far from the Coanda block 104.
It is discharged to 09.

As a result, the exhaust passages 107, 10
The exhaust passages 8 and 109 are the exhaust passages 107 closest to the Coanda block 104 for discharging fine powder composed of particles having a small particle diameter, and the exhaust passages 1 farthest from the raw material supply nozzle 116.
No. 09 is for discharging coarse powder composed of particles having a large particle size.
Then, the exhaust passage 108 located in the middle is for discharging the intermediate powder having the intermediate particle size.

The classified raw material 115 discharged into the exhaust flow paths 107, 108, 109 is the exhaust flow paths 107, 10 respectively.
8 and 109 are respectively collected by a dust collector (not shown) connected via pipes 121, 122 and 123,
Here, it is divided into powder and gas.

[0009]

The presence of agglomerates is one of the factors that deteriorate the classification accuracy of the airflow classifier 100. This is because some particles adhere to each other to form larger pseudo-particles and behave in a manner corresponding to the pseudo-particle diameter, and thus they follow a trajectory different from the trajectory that originally flies as a single particle. It has become.

As a solution to this problem, the material to be classified 11
A method of decomposing agglomerated particles into single particles by passing a compressed gas containing 5 through an ejector or an orifice and utilizing a difference in inertial force of each particle in the agglomerated particles and a shearing force generated between the particles. And is generally well known. Further, it is also known that so-called rapid classification is effective in which each particle dispersed in a single particle by such a decomposition treatment is classified immediately after the dispersion treatment so as not to reaggregate due to Brownian motion or the like. Therefore, in the dry classification, the classified raw material 115 is usually introduced into the raw material selection chamber 114 through the raw material supply nozzle 116 together with the compressed gas.

However, as shown in FIG. 6, when the compressed air containing the classified raw material 115 is introduced into the raw material selection chamber 114 from the raw material supply nozzle 116, the compressed air discharged from the raw material supply nozzle 116 is From that moment, it mixes with the surrounding fluid and diffuses while forming turbulence. The compressed air discharged from the raw material supply nozzle 116 has a velocity difference with the surrounding flow, and diffuses while causing turbulence.

Further, if the speed difference is to be corrected by the classifier as a whole, there is a problem that the blower or the suction machine for that purpose has a large capacity. Further, the material to be classified 115 contained in the compressed gas by this diffusion is separated into the material selection chamber 114.
There is a problem in that the initial behavior in the inside is different, and as a result, the classification accuracy is deteriorated. Therefore, an object of the present invention is to eliminate the above-mentioned problems, so that the compressed gas mixed with the raw material to be classified is prevented from diffusing in the raw material sorting chamber, and the raw material to be classified can be classified with high accuracy. A method and apparatus are provided.

[0013]

The above object of the present invention is to provide an inlet air flow path communicating with a raw material selection chamber and an exhaust flow path branched into a plurality, and have a curved air flow contact surface protruding into the raw material selection chamber. Using a Coanda block, an air flow classification method of injecting a classified raw material into the raw material selection chamber by a compressed air stream ejected from a raw material supply nozzle along the air flow contact surface and classifying the classified raw material by the flow of the compressed air stream In, the compressed airflow ejected from the raw material supply nozzle is classified by a compressed airflow different from the compressed airflow ejected from the raw material supply nozzle while being suppressed to the exhaust passage side. Can be achieved by a method.

Diffusion of the classified raw material can be prevented by pressing the raw material jetted from the raw material supply nozzle with the compressed air flow toward the exhaust passage. The above-mentioned object of the present invention is the velocity of an air stream containing a raw material ejected from the raw material supply nozzle,
This can be achieved by an airflow classification method characterized by ejecting the other compressed airflow at the same or a high speed.

By making the velocity of another compressed air flow higher than the velocity of the air flow ejected from the raw material supply nozzle, it is possible to reliably prevent the raw material to be classified from diffusing. The above-mentioned object of the present invention is a raw material sorting chamber, an inlet flow passage communicating with the raw material sorting chamber and an exhaust flow passage branched into a plurality, a Coanda lock having a curved air flow contact surface protruding into the raw material sorting chamber,
An air flow classifying device having a raw material supply nozzle for forming an air flow in which a material to be classified is placed on a flow of a compressed air stream jetted into the raw material selection chamber along the air flow contact surface, with respect to the position of the raw material supply nozzle. This can be achieved by an airflow classifying device characterized in that a sub-nozzle for generating an airflow in the same direction as the raw material supply nozzle is provided on the side opposite to the Coanda block.

By providing the sub-nozzle, another compressed air flow can be generated with a simple structure. The above-mentioned object of the invention can be achieved by an air flow classifying device characterized in that a compressed air flow supply system to the sub-nozzle comprises a compressed air flow supply device and a flow rate adjusting device.

By controlling the flow rate adjusting device, it is possible to generate a compressed air flow suitable for various conditions. Further, the above object of the present invention can be achieved by an airflow classifying device characterized in that the inside of the sub-nozzle is divided into a plurality of chambers in a direction along the air flow.

By dividing the inside of the sub-nozzle into a plurality of chambers, it is possible to prevent the compressed air flow from being disturbed.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an airflow classification method and apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an air flow classification device to which the present invention is applied, FIG. 2 is a detailed view of a sub nozzle, FIG. 3 is a sectional view showing an attachment angle of the sub nozzle, and FIG. 4 is a transverse sectional view of the sub nozzle.

As shown in FIG. 1, this air flow classifier 1
Means that the three classification exhaust passages 15, 16 and 17 branched by the first and second classification edges 11 and 12, the Coanda block 13 and the back block 14 are the raw material sorting chamber 1
8 is provided on the outlet side, and two intake paths 19,
A raw material selection chamber 18 provided with 20 on the inlet side and an air flow forming means (not shown) such as an exhaust fan for generating an air flow flowing from the air inlet paths 19, 20 toward the respective exhaust flow paths 15, 16, 17. ) And compressed gas (usually compressed air) are used to pump the classified material 21 into the material sorting chamber 18.
It is composed of a raw material supply nozzle 22 for jetting.

Here, the classified raw material 21 is supplied into the raw material supply nozzle 22 by the hopper 23 containing the classified raw material 21 communicating with the proximal end side of the raw material supply nozzle 22, and is supplied to the raw material supply nozzle 22. Compressed gas stream 2 supplied
4, and is injected into the raw material selection chamber 18 from the raw material supply nozzle 22 as a solid-gas mixed phase flow. Then, the jet flow containing the classified raw material 21 injected from the raw material supply nozzle 22 into the raw material sorting chamber 18 flows along the Coanda block 13 by the Coanda effect. At this time, centrifugal force acts on the classified raw material 21 and the classified raw material 21 is classified. The relatively coarse particles in the raw material 21 fly out from the jet flow flowing along the Coanda block 13.

On the outside of the air flow flowing along the Coanda block 13, from the air intake passages 19 and 20 to the exhaust passages 15,
The air flow toward 16, 17 flows, and the Coanda block 13
The relatively coarse particles in the raw material to be classified 21 that have jumped outward from the jet flow flowing along the exhaust gas flow path 15 corresponding to each predetermined particle size range due to the difference in the different scattering paths for each particle due to this air flow. , 16 and 17 are separately discharged.

The particle scattering descent 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 13 and is closest to the Coanda block 13. It is discharged to the path 15. On the other hand, the larger the particle size and the larger the inertia, the smaller the curvature of the scattering descent path, and scatters and descends farther from the Coanda block 13, and is discharged from the Coanda block 13 to the farthest exhaust passage 17.

As a result, the exhaust flow paths 15, 16, 1
7 is the exhaust passage 15 closest to the Coanda block 13
However, the exhaust flow path 17 farthest from the raw material supply nozzle 22 is for discharging coarse powder composed of particles having a small particle size. The exhaust passage 16 located in the middle is for discharging the intermediate powder having the intermediate particle size.

The classified raw material 21 discharged into the exhaust flow paths 15, 16 and 17 is supplied to the exhaust flow paths 15, 16 and 17 respectively.
Dust is collected by a dust collector (not shown) connected to the pipes via pipes 25, 26, and 27, where it is separated into powder and gas. The configuration described above is the same as the conventional one. Further, the airflow classifying device 1 of the present invention is provided on the upper side of the raw material supply nozzle 22, that is, on the side opposite to the Coanda block 13.
A sub nozzle 30 is provided. The ejection port of the sub-nozzle 30 is arranged toward the raw material sorting chamber 18. The compressed air sent from the compressor 31 is supplied to the sub-nozzle 30 via a flow rate adjusting valve 32 and a flow meter 33.

In this air flow classifying apparatus 1, as described below, the compressed gas containing the raw material to be classified 21 ejected from the raw material supply nozzle 22 into the classification chamber, that is, the raw material selecting chamber 18 diffuses immediately after the ejection. As a result, it is possible to prevent the locus of the classified raw material 21 in the raw material sorting chamber 18 from changing and the classification accuracy from decreasing. That is, as shown in FIG. 2, the air flow including the classified raw material 21 ejected from the raw material supply nozzle 22 and trying to diffuse upward is directed downward by the air curtain formed by the compressed air flow 35 ejected from the sub nozzle 30. By holding down and keeping the starting point of the particle trajectory more constant, the classification accuracy can be improved.

Compression 35 ejected from the sub nozzle 30
Is controlled by controlling the valve opening of a flow rate adjusting valve 32 provided at the rear of the raw material supply nozzle 22 so as to be suitable for the ejection speed of the raw material supply air stream ejected from the raw material supply nozzle 22, the particle size and the specific gravity of the classified raw material 21. The conditions can be obtained. Further, as shown in FIG. 3, by appropriately setting the attachment angle θ of the sub-nozzle 30 with respect to the raw material supply nozzle 22, the compressed airflow 35 ejected from the sub-nozzle 30 can be positively used for controlling the particle trajectory. it can. This is particularly effective for particles having a large specific gravity.

The velocity V2 of the compressed air flow 35 ejected from the sub-nozzle 30 is the same as or slightly higher than the velocity V1 of the air flow ejected from the raw material supply nozzle 22 by adjusting the valve opening of the flow rate adjusting valve 32. When the speed is set, the turbulence (diffusion) of the air flow ejected from the raw material supply nozzle 22 can be reliably prevented and the classification accuracy can be improved. In this example, V1 = 185 m / s, V2 = 200 m / s, θ =
By setting the angle to 3 °, good classification accuracy could be obtained.

Further, as shown in FIG. 4 (A), in order to minimize the turbulence of the compressed airflow 35 ejected from the sub-nozzle 30, the inner surface of the sub-nozzle 30 is divided by the vertical partition plate 3.
The velocity gradient of the compressed air flow 35 can be reduced by dividing the compressed airflow 35 into a plurality of chambers 37 according to 6 or a plurality of chambers 39 by a lateral partition plate 38 as shown in FIG. This makes it possible to improve the classification accuracy. Since the compressed air flow 35 does not contain dust, the partition plates 36 and 38 can be made as thin as possible.

As described above, the airflow classifying device 1 ejects the compressed airflow 35 from the sub-nozzle 30, so that the classification accuracy can be improved with a simple structure.

[0031]

As described above, according to the present invention, the compressed air flow ejected from the raw material supply nozzle is suppressed to the exhaust passage side by the compressed air flow different from the compressed air flow ejected from the raw material supply nozzle. Since the classification is performed while doing so, it is possible to prevent the air flow containing the raw material to be classified, which is ejected from the raw material supply nozzle, from being diffused, and thereby it is possible to improve the classification accuracy.

Further, according to the present invention, since the other compressed air flow is ejected at the same speed as or a larger speed than the air flow containing the raw material ejected from the raw material supply nozzle, it is ejected from the raw material supply nozzle. The flow of air can be reliably suppressed and diffusion can be prevented. Further, according to the present invention, since the sub-nozzle for generating the air flow in the same direction as the raw material supply nozzle is provided on the side opposite to the Coanda block with respect to the position of the raw material supply nozzle, the configuration is simplified.

Further, according to the present invention, the system for supplying the compressed air flow to the sub-nozzle comprises the device for supplying the compressed air flow and the flow rate adjusting device. Therefore, by controlling the flow rate adjusting device, the raw material supply nozzle and the sub nozzle are controlled. It is possible to eject the compressed airflow of the optimum condition from the sub-nozzle according to the speed of the airflow to be ejected, the attachment angle between the raw material supply nozzle and the sub-nozzle, and the like.

Furthermore, according to the present invention, since the interior of the bu nozzle is divided into a plurality of chambers in the direction along the air flow, the turbulence of the air flow ejected from the sub-nozzles is prevented and the classification accuracy is improved. be able to.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an airflow classification device according to the present invention.

FIG. 2 is a detailed view of a sub nozzle.

FIG. 3 is a sectional view showing an attachment angle of a sub nozzle.

FIG. 4 is a cross-sectional view of a sub nozzle.

FIG. 5 is a cross-sectional view of an airflow classification device according to a conventional example.

FIG. 6 is a detailed view of a conventional raw material supply nozzle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Air flow classifier 13 Coanda block 15, 16, 17 Exhaust flow path 18 Raw material selection chamber 19, 20 Air inlet flow path 21 Classified raw material 22 Raw material supply nozzle 30 Sub nozzle 31 Compressed gas supply device 32 Flow rate control device 35 Compressed air flow

Claims (5)

[Claims] 1. A Coanda block having an inlet air flow path communicating with a raw material selection chamber and a plurality of branched exhaust flow paths, and having a curved air flow contact surface protruding into the raw material selection chamber is used for the air flow contact surface. In the airflow classification method of ejecting the classified raw material into the raw material sorting chamber by the compressed airflow ejected from the raw material supply nozzle, and classifying the classified raw material by the flow of the compressed airflow, the compression ejected from the raw material supply nozzle An air flow classification method, characterized in that the air flow is classified by a compressed air flow different from the compressed air flow ejected from the raw material supply nozzle while being suppressed toward the exhaust flow path side. 2. The air stream according to claim 1, wherein the other compressed air stream is jetted at a speed equal to or greater than the speed of the air stream containing the classified raw material jetted from the raw material supply nozzle. Classification method. 3. A raw material sorting chamber, an inlet flow passage communicating with the raw material sorting chamber and an exhaust flow passage branched into a plurality, a Coanda lock having a curved air flow contact surface protruding into the raw material sorting chamber, and the air flow. An air flow classifying device having a raw material supply nozzle that forms an air stream in which a material to be classified is placed on a flow of a compressed air stream jetted into the raw material selection chamber along a contact surface, wherein a Coanda block is provided with respect to the position of the raw material supply nozzle. An air flow classifying device comprising a sub-nozzle on the opposite side from the sub-nozzle for generating an air flow in the same direction as the raw material supply nozzle. 4. The airflow classifying apparatus according to claim 3, wherein the compressed airflow supply system to the sub-nozzle comprises a compressed airflow supply device and a flow rate adjusting device. 5. The airflow classification device according to claim 3, wherein the inside of the sub-nozzle is divided into a plurality of chambers in a direction along the air flow.