JP2003245609A - Classifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air classifier having a classification rotor for allowing classifying air to flow from the outside to the inside in the direction opposite to a centrifugal separation direction to prevent particles with a large particle size from flowing into the classification rotor to enter fine particle matter. <P>SOLUTION: The ratio of the height (L) of the classification rotor to the diameter (D) thereof is smaller than 0.5. When a plurality of the classification rotors are arranged, the rotary shaft of the classification rotor is set at an angle smaller than 90° with respect to the vertical extension direction of a classification chamber. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a classifier having a classification rotor in which classification air flows from the outside to the inside in the direction opposite to the centrifugal separation direction.

[0002]

2. Description of the Related Art A classifying rotor of a classifier of this type is usually provided with a classifying blade arranged in a ring shape and extending parallel to a rotating shaft. These classification blades may extend obliquely with respect to the rotation axis, may be arranged at an angle in the radial direction, or may have a bent shape.

A classifier is used to separate a crushed powdery material into at least a fine particle having a small particle size and a coarse particle having a large particle size. Whether each particle is classified into a fine particle or a coarse particle is determined by the classified particle size.

For particles having the same size as the classified particle size, a force balance occurs in the classified rotor. That is, it is a balance between the outward centrifugal force generated by the rotation of the classification rotor and the inward suction force generated by the suction airflow.

Particles having a size smaller than the classified particle size are conveyed to the inside because they are controlled by the suction force, whereas particles having a size larger than the classified particle size are outside because they are controlled by the centrifugal force. It is centrifuged.

The classified particle size obtained by the classifier mainly depends on the diameter or the circumferential speed of the classifying rotor. If the structure and size are the same, the higher the peripheral speed or the number of rotations of the classification rotor, the finer the classification particle size can be obtained.
However, as the number of rotations of the classifying rotor increases, the wear and power consumption of the classifying blades remarkably increase, so it is mechanically and economically appropriate to suppress the classifying particle size to an appropriate level.

On the other hand, if the circumferential velocity of the classifying rotor and the inflow velocity of the classifying air in the circumferential part of the classifying rotor are kept constant, the larger the diameter of the classifying rotor, the correspondingly the inflowing air amount rises. The coarser the classified particle size is. That is, the classified particle size moves to the coarse particle size region. Therefore, if you want to separate fine particles similar to the small classification rotor with a large diameter classification rotor, you must further increase the circumferential speed, that is, the number of revolutions, and the classification blade wear and power consumption will increase. Not only that, but there is a risk that strength problems may occur in the structure including the bearing.

As a means for solving these drawbacks, it has been proposed to provide a classifier with a plurality of relatively small classifying rotors instead of providing one large classifying rotor.

A classifier of this kind having a plurality of classifying rotors is known from DE 3303078C1.
The air classifier in this case consists of a vertical classifying chamber with a cylindrical upper part and a funnel-shaped lower part, and a classifying device arranged in the upper part. This classifying device has a plurality of classifying rotors of the same kind which are adapted to the processing steps and connected in parallel, and these classifying rotors are individually driven. Classification air flows through the rotating classification rotor from the outside to the inside. The particles to be classified in this case are supplied to the classification chamber together with the classification air flowing from the lower opening of the lower portion or directly. This classified air is discharged from the inside of the classified rotor together with the classified fine particles. The coarse particles are discharged from the opening at the bottom of the classification rotor.

In the case where the same classifier is provided in the crusher, the coarse particles separated by the classifier are sent to the crushing chamber in the crusher and crushed again.

In DE 3615494A1, a plurality of separately driven classification rotors are arranged in a casing which constitutes a rectangular parallelepiped classification chamber, and each classification rotor is provided with a separate fine grain outlet. Machine is listed. It is possible to obtain a plurality of different fine particles by separately providing fine particle outlets of these classification rotors or by combining them.

[0012]

However, particles having a particle size larger than the classified particle size may enter the fine particles due to some obstacle during classification. The so-called "jump-in particles" broaden the particle size distribution of the classified fine granules and cause deterioration of the quality of the obtained fine granule products. Especially in the case of a classifier having a plurality of classifying rotors, the uniformity of particle size is likely to be impaired. That is, when a plurality of classification rotors are arranged in parallel, coarse particles once centrifugally separated on the outside of the classification rotors flow into the adjacent classification rotors and enter fine particles due to the high speed. .

When the classifying machine has one classifying rotor, the above problems do not occur. Further, in the case of a crusher with a built-in classifier, it is preferable that the classifying rotor has a drive shaft extending vertically. The reason is to prevent particles that are splashed upward from the lower crusher portion from directly jumping into the classification rotor.

In a classifier built-in type crusher having a plurality of classifying rotors, the rotary shaft of the classifying rotor is generally arranged horizontally, but this is inconvenient in terms of coarse particle jumping. . This is because large particles may enter the classification rotor from the radial direction at a very high speed. Also, DE3
When powder particles are directly supplied from above the classifying rotor as in 615494C2, it is disadvantageous because gravity is applied to the particles and the particles directly hit the classifying rotor. Here, large particles supported by gravity directly enter the classification rotor without being centrifuged by the classification rotor.

By the way, the radial velocity of the classifying air in the classifying rotor is quickly adapted to the classifying condition with respect to the particle diameter to be uniformized, but the mass is large for large particles having a high inflow velocity. Due to the resulting inertial forces, a small amount of braking is carried through the separation area in the classification rotor to the exit area of the fines.

Further, in the case of a classifier having a plurality of classifying rotors, it is difficult to supply the classifying objects equally to all the classifying rotors, and different classifying rotors are supplied differently depending on the state at that time. Inevitable. This causes flow fluctuations and vibrations, and also results in a momentary excessive increase in the flow velocity of the classification air flowing into the classification rotor.
This fluctuation or phenomenon is intensified as the number of classification rotors increases.

An object of the present invention is to increase the uniformity of particle size. Proper configuration and / or placement of the classifying rotor provides a method for reducing large particles from entering the classifying rotor at high speed and for re-extracting already introduced large particles from the classifying rotor to the outside. It is to prevent it from getting into fine granules.

[0018]

The object of the present invention is solved by the following structural features shown in the above claims.

According to the first aspect of the present invention, as described in claim 1,
When using the classification rotor, if the effective length of the classification blade in the axial direction is the classification rotor height (L) and the outer end is the classification rotor diameter (D), the classification rotor height (L) and the classification rotor diameter The ratio of (D) is smaller than 0.5 (L / D
It has been found that the use of <0.5), preferably less than 0.45, has a positive effect on the uniformity of the particle size. Further, in order to keep the air inflow velocity of the classification rotor constant, the diameter (D) of the classification rotor is increased along with the reduction of the height (L) of the classification rotor. Therefore, the flight time of particles in the classification rotor is lengthened. It is sufficient to dampen too large particles and expel them again from the classification rotor, especially at high inflow speeds.

[Effect] This effect has been conventionally thought to impair the uniformity of the particle size, because it is expected that the classifying rotor with a small L / D ratio will have a high flow velocity. That is, it has been considered that when the radial velocity in the classification rotor is increased, the inward flow is strengthened, so that the number of large particles entering the fine particles is increased.

However, it has been found that since the diameter of the classifying rotor (D) is increased, the path becomes longer until it reaches the circumferential region of the fine particle outlet of the fluid, so that the velocity of the fluid is damped. In other words, the velocity of the fluid in the radial direction certainly increases at the inlet of the classifying rotor, but the fluid is subjected to the centrifugal action in the classifying rotor until it reaches the fine particle outlet (d), so the flow path becomes long. This results in more braking and the radial velocity in the circumferential region of the fines outlet is smaller than in the case of a conventional classification rotor. In this way, the particles that have entered the classification rotor continue to receive centrifugal force in the classification rotor, and since the centrifugal force that large particles receive is greater than the centrifugal force that small particles receive, large particles that go toward the fine particle outlet Is further decelerated and braked, and is subjected to the action of the centrifugal force, so that the direction is easily changed to the centrifugal force direction.

Therefore, when a classifying rotor having an L / D ratio of less than 0.5 is used, although large particles are introduced into the classifying rotor, these large particles are effectively and surely classified again. Since the particles are centrifugally separated to the outside of the rotor, the amount of large particles that enter the fine particles is smaller than that in the case of a classification rotor of the same kind having an L / D ratio of 0.5 or more.

The second aspect of the present invention is a further preferable form of the first aspect of the present invention, in which the L / D ratio of the classification rotor is 0.3 to.
It should be set between 0.4. As a result, it is possible to more reliably prevent large particles from entering the fine particles.

According to a third aspect of the present invention, as described in claim 3,
That is, a plurality of classification rotors are arranged in one classification chamber. That is, by providing a plurality of relatively small classifying rotors in one classifier, it is possible to set the classifying particle size smaller than that in which one large classifying rotor is mounted, and to obtain fine particles having a uniform particle size. Can be obtained efficiently.

In addition, as a method for increasing the effect of the present invention,
Uniformity of particle size can be further improved by taking measures to prevent large particles from entering the classification rotor. That is, considering the supply amount of the powdery or granular material that can be classified, it is desirable to prevent a large amount of large particles from flowing into the classification rotor. If a large amount of particles are introduced at one time, the normal centrifugal separation in the classification rotor cannot be expected, and even if classification is possible, the time required for classification will be too long.

The fourth aspect of the present invention was devised as a preventive measure, and as described in claim 4, the rotation axes of the plurality of classification rotors are formed at an angle smaller than 90 ° with respect to the vertical direction of the classification chamber. It was extended with and the classification rotor was attached to this.

[Operation and Effect] That is, it is effective to arrange the classification rotor at an angle of 90 ° or less on the vertical axis instead of horizontally. In other words, if the arrangement angle of the classification rotor is reduced, it is less likely that large particles splashed from the other classification rotors and the crushing portion will jump directly into the classification rotor. In particular, by optimizing the angle between 0 ° and 90 °, it is possible to realize a compact structure with excellent economical efficiency.

The fifth aspect of the present invention, as a further preferred form of the fourth aspect of the present invention, extends the rotation axes of a plurality of classifying rotors at an angle of about 45 ° with respect to the vertical direction of the classifying chamber, and the classifying rotors are added thereto. It is installed. By setting the angle range shown in claim 4 more concretely from the actual surface, it is possible to prevent large particles from entering the classification rotor and
A compact structure with excellent economy can be realized.

The sixth aspect of the present invention was devised as another effective measure for preventing large particles from flowing into the classifying rotor, and as described in claim 6, from the upper part of the classifying chamber. A supply pipe is provided so as to penetrate between the plurality of classification rotors, and the lower end opening of the supply pipe is arranged below the classification rotor.

[Operation and Effect] As described above, when the particles to be classified are collectively supplied to the center of a plurality of classifying rotors and enter the classifying chamber below the classifying rotors for the first time, the particles are classified. It is possible to prevent large particles from directly entering the classification rotor without being subjected to a sufficient classification action by the classification rotor, such as directly falling on the classification rotor or reaching the classification blade surface.

Further, if the powdery material is supplied below the classifying rotor, the effect of gravity can be expected, and the effect that large and heavy particles can be kept away from the classifying rotor can be expected. The fine particles reach the upper classification rotor by riding on the rising air flow, and the larger particles have a tendency to drop downward because the action of gravity prevails over the rising air flow, and the tendency toward the upper classification rotor is weakened.

The seventh aspect of the present invention, as a further preferable form of the sixth aspect of the present invention, is provided with a direction changing member for changing the direction of the powder or granules in the horizontal direction at the lower end of the supply pipe so that the powder falls vertically downward. This is to change the direction of the granular material in the horizontal direction and supply the granular material in the vicinity of the classification rotor in the axial direction of the classification rotor.

[Effects] That is, when the fine particles contain a very large amount of fine particles, it is advantageous to provide the direction changing member so that the fine particles can be directly supplied to the classification rotor. Do you get it. This is particularly effective in the case of a crusher with a built-in classifier, in the case where the powder and granules have already reached the final fine particle size and the risk of over-grinding is avoided. This redirecting member also does not have a negative effect on the uniformity of the grain size. This is because the redirected particles flow substantially parallel to the axial extension of the classification rotor and do not flow radially with respect to the classification rotor axis.

According to the eighth aspect of the present invention,
The classification rotor is arranged in the casing of the classification chamber, and the discharge rotor for sending out fine particles from the classification rotor which is integrally connected to the classification rotor and rotated is arranged outside the casing. As a result, the classification rotor can be easily touched from outside the casing, and cleaning and maintenance monitoring can be easily performed.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the experimental examples of FIG. 1 and FIG. 2, four classifications having different classification rotor heights (L) and classification rotor diameters (D) and different ratios of the classification rotor height (L) to the classification rotor diameters (D) An example using a rotor is shown. As a granule, diameter 40 μm, particle density 270
Performed with 0 kg / m ³ particles. As the classification conditions, in all cases, the classified particle size at the fine particle outlet (d) was 8.
6 μm, the inflow velocity of particles was set to 36 m / s, and the circumferential velocity of the classification rotor was adjusted.

Each classifying rotor is provided with a fines outlet (d) of the same diameter. Figure 1 shows a schematic diagram of the classification rotor.
Fig. 1 shows the particle orbit curve in the classification rotor shown in (a).
It was described in (b). Each of these particle orbital curves is
The orbital curve of particles (40 μm) with a particle size much larger than the classified particle size (8.6 μm) is shown. When the other test conditions were the same (particle inflow velocity 36 m / s), the L / D ratio was varied between 0.2 and 0.8.

The thin solid line shows the track of large particles inside the classifying rotor with an L / D ratio of 0.8. This track reaches and exceeds the circumferential region of the fines exit. L
Similarly, when using a classification rotor having a / D ratio of 0.6 and 0.5, large particles intersect the circumferential region of the fine particle outlet. Therefore, the large particles in these two classification rotors get into the fine particles. This is because the large particles that have entered the circumferential region of the fine particle outlet are caught by the suction airflow discharged from the fine particle outlet, and can no longer be centrifuged outside by the classification rotor.

Different behavior is seen for classifying rotors with an L / D ratio of 0.4 or 0.2. If the other test conditions are the same, similarly large particles will be quickly braked by the action of centrifugal force during the increase of the flight distance inside the classification rotor, and the circle of the fine particle outlet (d) The flight direction will be changed to the outside before reaching the circumferential area. That is, since the large particles are centrifugally separated before reaching the circumferential region of the fine particle outlet (d), they do not enter the fine particle.

FIGS. 2A and 2B show the same experimental results as a diagram of particle radial velocity with respect to the classification rotor radius. It can be clearly seen that the velocity-direction change (particle radial velocity zero-pass) and the associated flight direction change occur inside the classification rotor for both L / D ratios of 0.4 and 0.2, Therefore, it is possible to centrifuge large particles. On the other hand, other test values of the classification rotor (when the L / D ratio is 0.5, 0.6 and 0.
8), large particles in the circumferential region of the fines outlet (d) can no longer be centrifuged and the fines outlet (d)
Discharge from.

FIG. 3 shows, as another embodiment, the upper part of the casing 1 of a classifier having two classifying rotors (2a, 2b). Both classification rotors (2a, 2b)
Via the drive shafts (3a, 3b), a dedicated motor (4a,
4b). Drive shaft (3a, 3b)
From the motors (4a, 4b) to the classification rotors (2a, 2
It extends through b) to the disk-shaped covers (5a, 5b) of the classification rotors (2a, 2b). Classification rotor (2
a), 2b) are inclined by 45 ° with respect to the vertical axis, and the classification rotors (2a, 2b) are rotated by 90 ° with respect to each other.
Are arranged at an angle of.

By arranging the classification rotors (2a, 2b) in this way, coarse particles centrifugally separated outward by the classification rotor (2a) are prevented from being thrown into the other classification rotor (2b). It Two fine grain passages (6
a, 6b) merge into one common passage (7) in the embodiment shown here. This embodiment is used when producing only one fines. Of course, these fines passages (6a, 6b) can also be kept separate if desired. For example, in the case of producing two different kinds of fine particle fractions, the classification rotor (2
a, 2b) is driven by motors (4a, 4b) having different rotation speeds.

FIG. 4 shows another embodiment similar to FIG. In this case, the classification rotors (2a, 2b) having different designs are used. In this case, the drive shafts (3a, 3b) are respectively connected to the discharge rotors (8a, 8b).
It is connected with each classification rotor (2a, 2b) via b). These discharge rotors (8a, 8b)
Has radial through holes, these through holes allow
From the inside of the classification rotor (2a, 2b) to the fine particle passage (6a,
It is possible to deliver fine particles to 6b).

FIG. 5 shows, as another embodiment, a classifier built-in airflow type crusher of a type in which powder particles are intensively collided and crushed, and a supply pipe (10) arranged from above. . By this supply pipe (10), it is possible to supply the powdery particles to the crushing chamber (13) below the classification rotors (2a, 2b) through the center of the two classification rotors (2a, 2b). .

FIG. 6 shows an air flow type crusher similar to that shown in FIG. 5, with a direction changing member (12) additionally provided. This apparatus is for classifying rotors (2a, 2b) of powder and granules introduced through a supply pipe (10) into an air flow type crusher.
To the pre-classification of the ground material before it reaches the grinding chamber (13).

[0045]

As described above, according to the present invention,
Prevents large particles from flowing into the classification rotor at high speed,
In addition, by guiding the large particles that have flowed in to the outside again from the inside of the classifying rotor, it is possible to prevent the large particles from entering the fine particles and obtain a product with a uniform particle size. Further, it is possible to efficiently carry out effective classification together with selection of an optimum supply method of the powder or granules to be classified to the classification rotor.

The classifier of the present invention is particularly effective for powder materials such as toner and powder coating material for photosensitive materials which require a sharp particle size distribution with a narrow particle size range.
Furthermore, resins, waxes, pigments, ceramics, abrasives, fillers, metal powders and metal oxides such as alumina and zirconia, graphite, mineral materials such as talc, mica, calcium carbonate, limestone, calcite, graphite and quartz, In addition to medicines, foods, feeds, soybeans, wheat, starches, etc., it can be applied to various other granular materials.

[Brief description of drawings]

FIG. 1 shows particle orbit curves in classification rotors having different L / D ratios.

FIG. 2 shows the radial velocity of particles on the classification rotor radius.

FIG. 3 is an embodiment showing a spatial arrangement of a plurality of classification rotors using a drive shaft that penetrates therethrough.

FIG. 4 is an embodiment showing a spatial arrangement of a classification rotor having a discharge rotor.

FIG. 5 shows an embodiment of the present invention in which an air flow type crusher with a built-in classifier is provided with a crushed material supply pipe.

FIG. 6 shows an embodiment of the present invention in which a classifier built-in airflow type pulverizer is provided with a pulverized material supply pipe and a direction changing device.

[Explanation of symbols]

D classification rotor diameter L classification rotor height d Fine particle outlet 1 casing 2a, 2b classification rotor 3a, 3b drive shaft 4a, 4b motor 6a, 6b Fine grain passage 7 passages 8a, 8b discharge rotor 10 supply pipes 11 classification room 12 direction conversion member 13 Grinding room

Claims (8)

[Claims] 1. An airflow classifier having a classifying rotor having ring-shaped classifying blades substantially parallel to a rotation axis, which separates fine particles into fine particles and coarse particles, and the fine particles are classified air. In the classifier in which the coarse particles are discharged from the inside through the classifying rotor and returned to the classifying chamber, the effective length of the classifying blade in the axial direction is defined as the classifying rotor height (L), and the outer end is the classifying rotor diameter (L). D), the classifier is characterized in that the ratio of the classifying rotor height (L) to the classifying rotor diameter (D) is smaller than 0.5. 2. The classifier according to claim 1, wherein the ratio of the classifying rotor height (L) to the classifying rotor diameter (D) is 0.3 to 0.4. 3. The classifier according to claim 1, wherein a plurality of classifying rotors are arranged in one classifying chamber. 4. The classifier according to claim 3, wherein the rotating shaft of the classifying rotor is extended at an angle smaller than 90 ° with respect to the vertical direction of the classifying chamber. 5. The classifier according to claim 3, wherein the rotating shaft of the classifying rotor is extended at an angle of about 45 ° with respect to the vertical direction of the classifying chamber. 6. A supply pipe is provided so as to penetrate between a plurality of classification rotors from an upper part of the classification chamber, and a lower end opening of the supply pipe is arranged below the classification rotor. The classifier according to 3 to 5. 7. The classifier according to claim 6, further comprising a direction changing member that changes the direction of the powdery particles in the horizontal direction at the lower end of the supply pipe. 8. A classifying rotor is arranged in a casing of a classifying chamber, and a discharging rotor for discharging fine particles from the classifying rotor integrally connected to the classifying rotor is arranged outside the casing. The classifier according to claim 1.