JPH07265802A - Powder classifier and its operation - Google Patents

Abstract

PURPOSE:To provide a powder classifier capable of efficiently and precisely classifying powders even when the classification point is changed. CONSTITUTION:A casing 1 is provided with a powder inlet 3 at the center of the upper face and an air inlet 10 on the outer side wall periphery, and a classification rotor 4 having an air circulating cavity extending from the circumference toward the axial center is provided and made rotatable by a vertical rotating shaft 8. Further, a throttling plate 9 is detachably fixed in the powder inlet to adjust the amt. of air from the powder inlet. Consequently, the ratio of the amt. of air from the powder inlet to that from the air inlet is appropriately set, and classification is performed under optimum conditions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder classifier using an air flow and a method of operating a powder classifier for adjusting the amount of air.

[0002]

2. Description of the Related Art A powder classifier is used for selecting powders having a predetermined particle size from powder particles having various particle sizes.
Many classification methods are known, and one of them is a powder classifier using a classification rotor. A powder classifier using this classifying rotor rotates a classifying rotor having classifying blades at high speed in a casing to generate centrifugal force by rotating the classifying rotor on the powder charged from the upper part of the classifying rotor and at the same time, classifying rotor. Air is introduced from the periphery of the class toward the center, and powder with a large particle size that is largely subjected to centrifugal force by the classification rotor flows out of the classification rotor, while particle size that is greatly affected by the air flow due to centrifugal force The small powder is moved along with air toward the center to classify the powder.

[0003]

In this type of powder classifier, the air used for classification flows from the outer circumference of the classifying disk through the air inlet, but in reality, other parts, namely, The powder to be classified also enters from the charging opening and flows into the classification disk together with the powder. The sum of these two amounts of air is the air for classification.
Generally, in an air classifier, it seems that it is better to perform the classification action only with the amount of air flowing in from the outer periphery, but from various experiences, this type of classifier also requires some amount of air from the powder inlet. Therefore, it was found that the classification efficiency is increased by appropriately selecting the ratio of the two air amounts.

On the other hand, even in this type of classifier, since the powder is classified by the balance between the centrifugal force acting on the powder and the air flow, the specifications of classification, such as the throughput per unit time and the classification point, are designed. However, if the user changes the number of rotations, etc., the classification point can be changed, but if the classification point is changed in this way, the centrifugal force and air from the classification rotor The equilibrium with the drag force of the flow may change, resulting in a decrease in efficiency and classification accuracy.

The present invention has been made in view of the above points, and not only provides a powder classifier that can change the classification point without lowering the accuracy even in such a case, but also has a classification accuracy of the classifier. It is to provide an improved driving method.

[0006]

In order to achieve the above object, the present invention uses an air inflow amount from a powder charging port formed at the center of the upper surface of a casing and an air introducing port formed at the side of the casing. The operating method is to adjust the ratio with the amount of air introduced into the device to a preferable ratio. To adjust the ratio, an air amount adjusting device, a diaphragm plate or an adjusting valve is attached to the powder charging port.

The ratio Q ₁ / Q ₂ between the air amount Q ₂ from the air inlet and the air amount Q ₁ coming from the powder inlet is 0.02.
The classification efficiency becomes highest by keeping it at 0.14.
In this type of classifier, the powder introduced into the machine is subjected to a dispersing action by the air introduced at the same time and becomes closer to a single particle, so that Q ₁ is required to some extent, and when it is extremely small, the dispersing action can occur. Disappear. On the other hand, if Q ₁ becomes too large, the turbulence due to the merging with the airflow that comes in from the original air inlet will increase, and the airflow in the classification field will be disturbed and the force as designed will not reach the particles, resulting in classification accuracy. Is reduced.

In order to achieve such a ratio, a diaphragm plate or a regulating valve may be attached to the powder inlet as described above. The relationship with the amount of air from the air inlet may be set within the above range.

[0009]

[Function] The classification accuracy is improved by appropriately selecting the ratio of the amount of air from the powder inlet to the amount of air from the air inlet of the powder classifier. If the classification point is changed by changing the rotation speed of the classification rotor, etc., the relationship between the centrifugal force of the classification rotor and the drag force of the air from the air inlet will change, and the classification accuracy as designed will not be obtained. However, even in such a case, by appropriately setting the ratio of the amount of air flowing into the casing from the powder inlet and the amount of air introduced from the air inlet, it is possible to achieve high efficiency without lowering the classification accuracy. Can classify.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the powder classifier and its operating method of the present invention will be described with reference to the drawings.

FIG. 1 is a vertical sectional view showing an embodiment of a powder classifier according to the present invention. The powder classifier 1 includes a casing 2 that covers the entire body, a classifying rotor 4 provided in the casing 2, a balance rotor 6, a rotating shaft 8 that rotates these, and the like.

The casing 2 has a circular shape as a whole, has a powder feeding port 3 connected to a powder feeding device (not shown) at the center of the upper surface, and has an air introducing port 10 and a coarse powder removing device on the peripheral side. An outlet 12 and a spiral casing 14 are provided. A powder feeding pipe 5 is connected to the powder feeding port 3, and the powder is fed into the powder classifier 1 together with air from the powder feeding pipe 5. The powder feeding pipe 5 is provided with a diaphragm mounting portion 7 so that a diaphragm plate 9 can be mounted (in the figure, it is shown in a mounted state). The rotating shaft 8 is provided at the center of the casing 2, is rotatably supported by a bearing 30, and has a pulley 33 attached to the lower end thereof, and is rotationally driven by being connected to a drive motor (not shown).

The classification rotor 4 is integrally attached to the rotary shaft 8 and has a cavity 16 formed therein, which communicates from the circumferential portion to the lower portion of the shaft center. The cavity 16 has an open peripheral edge portion. Is provided with a plurality of classification blades 18 extending radially in a radial direction, and a classification chamber 24 is formed. In addition, on the upper plate 19 of the classification rotor 4, an opening 20 is formed in a ring shape along the outer periphery, which is located substantially in the center of the classification blade 18 in the radial direction and through which the powder falls.

A plurality of auxiliary blades 22 are arranged at equal intervals on the lower surface of the classification rotor 4 facing the classification blades 18. When the classification rotor 4 rotates, the auxiliary blades 22 cause air to flow in the direction of rotation. Air is introduced in the direction of the classification chamber 24 in a given and swirled state. A space 26 is formed between the casing 2 and the outer periphery of the classification rotor 4, and the coarse powder outlet 12 is formed in communication with the space 26.

A space 32 is formed between the upper plate 19 of the classification rotor 4 and the upper plate 17 of the casing 2 to connect the powder charging port 3 and the ring-shaped opening 20 of the classification rotor 4 to each other. There is. In this space 32, a large number of powder dispersion blades 34 extending from the axial center to the outer peripheral direction are radially provided on the center side of the upper plate 19 of the classification rotor 4, and the dispersion blades 34 have radial ends. Upper plate 1 of the classification rotor 4 between the opening 20 and the opening 20
9 The upper surface is made flat, and the powder is secondarily dispersed between this flat surface and the inner surface of the casing 2 facing it.

The balance rotor 6 is mounted so as to be symmetrical with respect to the classification rotor 4 in arrangement, and the cavity portion 4 communicating from the circumferential portion to the axial center portion is almost the same as the classification rotor 4.
2, and the cavity portion 42 is integrally fixed to the classification rotor 4 and the rotary shaft 8 so as to communicate with the cavity portion 16 of the classification rotor 4. A large number of blades 44 are radially provided in the cavity 42 at the peripheral edge of the opening of the balance rotor 6, and the casing 2 is provided with a spiral casing 14 surrounding the outer periphery of the balance rotor 6 opening. It is integrally and airtightly attached. This spiral casing 14
Is connected to a collection device such as a cyclone and a bag filter (not shown), and a fan and a blower.

Next, the powder classifier 1 configured as described above
I will explain how to drive.

First, the classification rotor 4 and the balance rotor 6 are rotated at a desired speed by a motor (not shown), and a negative pressure air flow is generated inside the powder classifier 1 by a blower connected to the outside. As a result, air is sucked from the air introduction port 10 of the casing 2, and the air introduced by this suction is converted into a flow in the rotational direction by the auxiliary blades 22 and swirls into the classification chamber 24 from the void 26, In the classification chamber 24, the flow is in the radial direction along the classification blade 18. The air that has entered the classification chamber 24 is the balance rotor 6
And is sucked through the spiral casing 14. The flow of air at this time is shown by an arrow in FIG.

In this state, the powder raw material charged with the air from the powder charging port 3 rides on the air flow, and while passing between the dispersion blades 34, the powder raw material is almost radiated about the axis of the classification rotor 4 in the radial direction. The powder is uniformly dispersed, and the powder is primarily dispersed.
The powder coming out from the end of the dispersion blade 34 is the classification rotor 4
With the rotation of, the light is radiated almost in the tangential direction of the array circle of the dispersion blades 34 and is secondarily dispersed.

The sufficiently dispersed powder is supplied to the classification chamber 24 through the ring-shaped powder introduction opening 20, where each particle of the powder flows in the radial direction along with the centrifugal force generated by the rotation of the classification rotor 4. Receives drag due to air. Of these particles, the coarse particles satisfying the relationship of centrifugal force> drag force are blown into the space 26 around the outer periphery of the classification rotor 4, and the coarse powder outlet 12
Is taken out of the powder classifier 1 while being air-sealed using a rotary valve or the like. Further, fine particles for which the relationship of centrifugal force <drag is established are pneumatically transported to the outside of the powder classifier 1 through the balance rotor 6 and the spiral casing 14 while being carried on the air flow in the radial direction, and are then transferred to the cyclone, bag filter, etc. It is collected by a collector.

Here, if the classification point is changed by changing the rotation speed of the classification rotor 4, for example, the balance between the centrifugal force and the air flow due to the rotation speed may change, and the classification efficiency may decrease. Therefore, the diaphragm plate 9 is attached to the powder feeding pipe 5 as shown in the figure. By attaching the diaphragm plate 9, the amount of air passing through the powder charging port 3 and the air introducing port 10
It is possible to change the ratio of the amount of air introduced from the to the optimum value, and set the centrifugal force and the drag force of air to values that match the classification points.Even when the classification points are changed, the classification accuracy is improved. Classification is possible without lowering.

If the diameter of the powder charging port 3 is set to be thick and the amount of air is narrowed down by the adjusting means, the diaphragm plate 9 or the like, the amount of air is increased by changing the classification point. It is easy to adjust the adjustment means or remove the diaphragm plate. Further, in order to increase the amount of air, not only the diameter of the powder introduction port may be increased, but also the distance between the upper plate 19 of the classification rotor 4 and the casing 2 may be increased. After doing so, it is effective to limit only the air inflow amount of the powder feeding pipe 5 by the diaphragm plate 9 or the like. Further, the adjusting means may be a variable air adjusting means capable of adjusting the normal air flow rate.

Further, since the diaphragm plate 9 is provided with the passage hole at the center thereof, the powder can be introduced into the center of the classification rotor 4, and the dispersion of the powder on the upper surface of the classification rotor 4 can be more surely performed. There is also an effect to do.

(Experimental example) In the experiment, the diameter of the classification rotor was 10
Using a centrifugal powder classifier according to the present invention of 00 mm,
The rotation speed was 700 rpm, the total air amount was 120 m ³ / min, and the powder supply amount was 6 t / hour. The experimental results are shown in FIGS. 2 and 3. The total air amount is the sum of the air inflow amount from the powder feeding port 3 and the air amount from the air introducing port 10, and the air amount ratio is the air amount flowing from the powder feeding port 3. It refers to the ratio to the amount of air introduced from the air inlet 10. or,
D _{25 in} FIG. 3 is a particle size at which 25% of powder is integrated and separated, and D ₇₅ is a particle size at which 75% of powder is integrated and separated. The classification accuracy index κ is a value obtained by dividing D ₂₅ by D ₇₅ , and the closer the value is to 1, the sharper the classification accuracy is. FIG. 2 is a graph showing the results of FIG. 3, and shows the change of the classification accuracy index κ with respect to the air amount ratio. It is clear from this graph that the classification accuracy index κ improves when the air amount in the powder inlet 3 is limited and the air amount ratio is reduced.

On the other hand, FIG. 4 shows a case where a powder classifier similar to that used in the above experimental example is classified under the conditions of a rotation speed of 3600 rpm, a total air amount of 62 m ³ / min, and a powder supply amount of 250 kg / hour. 2 shows the same relationship as in FIG. As can be seen from FIG. 4, when the air amount ratio exceeds a certain value, the classification accuracy index κ
Is reduced. This is because if the amount of air from the powder charging port 3 is excessively limited, it adversely affects the dispersion of the powder on the upper surface of the classification rotor 4 and also the relationship between the centrifugal force and the drag force of air. It seems to be because.

[0026]

According to the powder classifier and the method of operating the same of the present invention, the optimum ratio can be obtained by adjusting the ratio of the amount of air flowing in from the powder inlet and the amount of air introduced from the air inlet. It is possible to perform classification in the operating state. Furthermore, by setting the air amount ratio to 0.02 to 0.14, the classification accuracy can be further improved.

Further, since the air quantity ratio of the classifier can be changed appropriately, even when the classification point is changed, the air quantity ratio is set to a value suitable for the changed classification point. As a result, the optimum classification state can be formed, the classification accuracy does not decrease, and classification can be performed with high efficiency even at the changed classification point.

By providing the air adjusting means in the powder feeding pipe connected to the powder feeding port, the amount of air flowing in from the powder feeding port can be easily changed. Furthermore, since the diaphragm plate can be attached or detached, the amount of air can be easily adjusted and the cost can be reduced. Further, the powder can be put in the center of the classification rotor, and the dispersion can be ensured.

[Brief description of drawings]

FIG. 1 is a sectional view of a powder classifier according to the present invention.

FIG. 2 is a graph showing experimental results using the powder classifier according to the present invention.

FIG. 3 is a table showing experimental results using the powder classifier according to the present invention.

FIG. 4 is a graph showing the experimental results using the powder classifier according to the present invention.

[Explanation of symbols]

 1 Classifier 2 Casing 3 Powder charging port 4 Classification rotor 5 Powder charging pipe 6 Balance rotor 7 Restrictor mounting part 8 Rotating shaft 9 Throttling plate 10 Air inlet 12 Coarse powder outlet 14 Vortex casing 16 Cavity 18 Classifying blade 20 Opening

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Satoshi Akiyama 5-3-1, Tsurugaoka, Oi-cho, Iruma-gun, Saitama Nisshin Seifun Co., Ltd. (72) Takahiro Ichikawa Tsurugaoka, Oi-cho, Iruma-gun, Saitama 5-3-1 Nisshin Seifun Co., Ltd. Production Technology Research Institute (72) Inventor Yukiyoshi Yamada Tsurugaoka, Oi-cho, Iruma-gun, Saitama 5-3-1 Nisshin Seifun Co., Ltd. (72) Inventor Hikosaka Tohru Nisshin Engineering Co., Ltd. 18-4 Koamimachi, Nihonbashi, Chuo-ku, Tokyo

Claims (5)

[Claims] 1. An air flow cavity in which two powder disks having the same diameter are parallel to each other in the axial direction from the circumference to the axial center in a casing having a powder inlet in the center of the upper surface and an air inlet around the outer wall. A classification rotor having a vertical section is rotatably provided by a vertical rotation shaft, and a plurality of classification blades are formed on the circumference of the classification chamber in the cavity of the classification rotor, and a powder is formed on the upper disc between the classification blades. In the powder classifier provided with a charging opening, the powder classifying apparatus is operated by adjusting a ratio of an air inflow amount from the powder charging port and an air amount from the air introducing port. Driving method. 2. The air amount ratio of the air inflow amount from the powder charging port to the air amount from the air introducing port is 0.02 to 0.02.
The method for operating the powder classifier according to claim 1, wherein the method is 0.14. 3. An air circulation cavity in which two powder disks having the same diameter are parallel to each other in the axial center direction from a circumferential portion in a casing having a powder charging opening at the center of the upper surface and an air introducing opening around the outer wall. A classification rotor having a vertical section is rotatably provided by a vertical rotation shaft, and a plurality of classification blades are formed on the circumference of the classification chamber in the cavity of the classification rotor, and a powder is formed on the upper disc between the classification blades. A powder classifier having a charging opening, wherein the powder charging port is provided with adjusting means for adjusting an air inflow amount. 4. The powder classifier according to claim 3, wherein the adjusting means is a diaphragm plate. 5. The powder classifier according to claim 3, wherein the adjusting means is a variable air amount adjusting valve.