KR940006023B1 - Powdered body sorter - Google Patents

Abstract

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Description

Powder classifier

1 is a particle size distribution diagram obtained from classification test results using a powder classifier according to the present invention.

2 is a longitudinal sectional view of an example of a powder classifier.

3 is a partially cutaway plan view of the classifier.

* Explanation of symbols for main parts of the drawings

1: Casing 2a: Powder inlet

2b: air inlet 4: classification rotor

7,8: classification wing 16: dispersion wing

18: Balanced rotor 19: cavity

21: Vortex Casing

[Industrial use]

This invention relates to the powder classifier which classifies powder using the equilibrium of centrifugal force and drag by airflow.

[Prior art]

Background Art Conventionally, various powder classification methods are known, but one of them is an air classification method which imparts centrifugal force to powder particles, imparts drag force by air flow, and classifies by changing the equilibrium point determined from centrifugal force and drag force. (See, for example, Japanese Patent Publication No. 57-11269).

FIG. 2 is a longitudinal sectional view of an example of an air classifier of this type, which is known in the prior art, and FIG. 3 is a plan view showing a part of the classifying rotor of the powder classifier shown in FIG.

In the figure, 1 is a casing which has a powder inlet 2a connected to a powder supply device (not shown) at the center of the upper surface, and an air inlet 2b at the peripheral part side. A disk-shaped classifying rotor 4 having a cavity 3 communicating from the circumference downwardly to the axial center is arranged, which classifying rotor 4 is provided by bearings 5 at the longitudinal axis of the casing 1. It is integrally fixed to the upper end of the rotating shaft 6 attached vertically. In addition, in the cavity 3 of the open periphery of the classification rotor 4, as shown in FIG. 3, a plurality of outer classification blades 7 arranged at equal intervals in the circumferential direction are radially formed, and While forming a plurality of inner classifying blades 8 radially inside the outer classifying blade 7 and facing the outer classifying blade 7 so as to be two stages in the radial direction of the classifying rotor 4, A predetermined gap 9 is formed between the outer and inner classification vanes 7, 8, and furthermore communicates with the cavity 3 in the upper plate 4a of the classification rotor 4 facing the gap 9. The powder inlet 10 on the ring is formed. Moreover, by making it the structure of such a classification blade, the classification chamber 11 of the wide forced vortex corresponding to the coarse side and the fine powder side to the outer classification blade 7 and the inner classification blade 8 part. 7 and 8).

In addition, on the lower surface of the classifying rotor 4 facing the classifying blades 7 and 8, a plurality of auxiliary wings 12 are radially arranged at equal intervals in a circular direction, and the classifying rotor 4 rotates. In this case, the auxiliary blades 12 impart a flow in the rotational direction to the air so as to be introduced in the direction of the classification chamber 11 in the pivoted state. 13 is a hollow formed around the outside of the classification rotor 4, and a coarse powder ejection opening 14 communicating with the hollow 13 is formed in the casing 1.

15 is a space for communicating the powder inlet 2a formed between the upper plate 4a of the classifying rotor 4 and the lower surface of the upper plate of the casing 1 with the ring-shaped powder inlet 10 of the classifying rotor 4. On the central part side of the upper plate 4a of the classification rotor 4 located in the space 15, a plurality of powder dispersing vanes 16 extending in the circumferential direction from the shaft center are provided radially, and the dispersing wing 16 The top plate 4a of the classifying rotor 4 between the radial end of the ring and the ring-shaped powder inlet 10 is planarized to disperse the powder secondly between this flat surface and the inner surface of the casing 1 opposite it. The dispersion gap 17 is formed.

18 is a disk-shaped balance rotor having a common portion 19 communicating from the same circumference with the classification rotor 4 to the axial center portion, the balance rotor 18 being placed in the arrangement with the classification rotor 4. Further, the cavity 19 is in communication with the cavity 3 of the classification rotor 4 so as to be integrally fixed to the rotating shaft 6 in the casing 1, and at the same time, the cavity of the opening peripheral portion of the balanced rotor 18 is fixed. In the part 19, a plurality of wings 20 are radially installed, and are integrally hermetically attached to the balanced rotor 18. In addition, a collecting device such as a cyclone or a bag filter (not shown) is connected to the vortex casing 21.

Next, the operation will be described. First, the classification rotor 4 and the balanced rotor 18 are rotated at a predetermined speed by an electric motor (not shown), and the suction action of the balanced rotor 18 and the blower connected to the outside (not shown). The air introduced from the negative pressure air inlet (2b) into the classifier is exchanged by the auxiliary blades (12) for flow in the rotational direction and is separated from the space (13) by the classifier (11). In the classifier chamber 11, the classifier blades 7 and 8 are used to generate airflow at the same circumferential speed as the classifier rotor 4. At the same time, in the classifying chamber 11, since it is a type sucked by the balance rotor 18 and the blower, the air in the circumferential surface of the classifying chamber 11 becomes a radial flow. The air passing through the balanced rotor 18 is connected to the cyclone blower via the vortex casing 21.

The flow of air at this time is shown by the arrow in FIG.

과 반경방향의 흐름에 의한 항력(3π μVrDp)을 받는다. 이들 입자중 원심력＞항력의 관계가 성립하는 굵은 입자는 분급 로우터(4)의 외주의 빈곳(13)내로 날려져셔, 조분 취출구(14)로부터 회전형 밸브 등을 이용하여 공기 밀봉된 상태로 분급기 밖으로 취출된다. 또, 원심력＜항력의 관계가 성립하는 미세한 입자는 반경방향의 공기류에 실린 상태로 평형로우터(18), 와류형 케이싱(21)을 거쳐서 분급기 밖으로 공기 수송되어, 싸이크론, 백 필터 등의 포집기에 의해 포집된다.In this state, the powder raw material introduced from the powder inlet 2a is loaded into the air stream, and is uniformly divided in the radial direction around the axis of the classification rotor 4 during the passage between the dispersing blades 16, Primary dispersion of the powder is performed. Then, the main body coming out of the discontinuity of the dispersing vanes 16 is radiated in the substantially tangential direction of the dispersing vane array source in accordance with the rotation of the classification rotor 4, and is secondly dispersed in the dispersing gap 17. The powder sufficiently dispersed by the above action is passed through the ring-shaped powder inlet 10 and supplied to the classification chamber 11, where each particle of the powder is centrifugal force (

And drag due to radial flow (3π μVrDp). Among these particles, the coarse particles having a relationship of centrifugal force> drag are blown into the space 13 of the outer circumference of the classification rotor 4, and the classifier is air-sealed from the coarse powder outlet 14 using a rotary valve or the like. Is taken out. In addition, the fine particles having a relationship of centrifugal force <drag are transported out of the classifier through the balance rotor 18 and the vortex casing 21 in a state of being loaded in a radial air stream, and are collected in a cyclone, bag filter or the like. Is captured by

In addition, adjustment of the classification point in the classifier of the said structure is performed by changing the rotational speed of the classification rotor 4, or the passage air volume of the classification chamber 11. As shown in FIG.

In addition, the code | symbol in the said formula is as follows.

Dp: particle diameter

ρp: particle density

Vo: Wind speed in the circumferential direction

Vr: radial wind speed

R: Radius distance of the grading point

μ: viscosity of air

By the way, it is known that the number of classification blades 7, 8 in this kind of powder classifier affects the classification degree. The action of the blade is to give the centrifugal force of the particles, in addition to making the direction of the air flow constant and rectifying correctly.

Therefore, the number of classification wings is normally determined from the viewpoint as described later. The relative speed Vro near the surface (pressure side) facing the rotation direction of the classification blade is represented by the following equation.

Where Q is the air volume, Z is the number of blades of the classification blade, b is the height of the classification blade, Ro is the radius of the classification rotor, t is the thickness of the classification blade, ω is the rotational angular velocity of the classification rotor, and Vro is the direction of rotation of the classification blade. The relative velocity near the face towards, r is the central diameter of the rotor classifier.

On the other hand, the relative speed Vr ₁ of the surface (negative pressure side) which becomes an inner surface with respect to rotation is represented by the following formula.

In addition, these formulas (1) and (2) are both described in the new edition Pneumatics Engineering Handbook Basic Section 172 Corona Screw (1979).

If the number of classifying blades is small, the difference between the state velocity Vr ₀ given by equation (1) and Vr ₁ given by equation (2) becomes large, and the classification field is disturbed. In the case of increasing the number of classifier wings upside down, a good classifier field is formed as a whole. In view of the commutation of the classifier, the number of classifier blades is more preferable, but there are design limitations in order to secure an effective wind passage opening area, and in a typical design, the relative speed Vr ₀ on the pressure side The number of classifier blades is determined based on the size of the classification rotor and the operating conditions (rotational speed, air volume, etc.) such that the ratio A of the relative speed Vr ₁ on the negative pressure side is 0.4, preferably 0.5 or more.

Specifically, the throughput is, for example, 1 hour based on the standard specification of the classifier (Daily Material Volume 2, No. 10 (1984), page 51, No. 10 (1984) # 51). For large classifiers up to around 4000 kg, the classifying rotor has a diameter of 1000 mm, a class vane height of 40 mm, a class vane thickness of 10 mm, a rotating rotor speed of 1300 rpm (700 to 2000 rpm), air volume of 97 m ³ / min ( 70 to 120 m ³ / min), in order to satisfy the relative speed ratio A with all the standard specifications, the number of blades is set to 90 sheets. Since the diameter is 600 mm, the rotation speed of the classification rotor is 700 to 2000 rpm, and the air volume is 40 to 60 m ³ / min, the number of classification blades is set to 45 sheets in order to satisfy the ratio A of the relative speed to all the standard specifications.

As a result of experiments by changing the number of classifier blades of the classifier, the inventors found that the number of blades affects the yield of the product, in particular, the yield of the coarse side product.

[Object and Composition of the Invention]

SUMMARY OF THE INVENTION The present invention has been made in view of the above point, and aims to improve the yield of the coarse powdered product, and in order to achieve this object, the number of classifier blades of the powder classifier is usually determined based on at least the diameter of the classifying rotor and the amount of air. The number of sheets lost was less than the number of wings classified.

EXAMPLE

Hereinafter, the present invention will be described in detail.

In the powder classifier which is the object of the present invention, the classifier blade also has a slight grinding effect, so when the number of blades is large, the grinding effect is also increased so that the powder is ground, and it is difficult to recover the crude powder having a small amount of fine powder mixing desired. do.

Next, the experiment example which classified two types of powder using the comparatively large classifier is shown.

[(1) Experimental Example 1]

Powder: calcium bicarbonate

Experimental Example 2

Target powder: silicon oxide

As can be seen from the above two experimental examples, the coarse yield increases when the number of wings of the classification blade is less than the standard number of sheets (in the above example, 90 sheets based on the formula shown in the above-mentioned (prior art) column).

In addition, when the result of Experimental Example 2 is expressed by the particle size distribution map, it becomes like a 1st degree. The curve A is the powder before classification, the curves B ₁ and B ₂ are the derivatives and coarse powder when the number of blades is 90, and the curves C ₁ and C ₂ are the derivatives and coarse powder when the number of classification blades is 60 sheets.

As can be seen from this figure, as suggested by the present invention, when the number of classifying blades is reduced, the particle size of the fine powder does not change so much that the coarse particle size is coarse. In other words, the rate at which the fine powder in the coarse powder mixes is reduced to obtain a good coarse powder.

It has also been experimentally confirmed that similar results can be obtained by reducing the number of 45 wings by a normal design to 36 even for a medium classifier.

As described above, in the present invention, the number of classifying blades of the main classifier is set to be less than the number of classifying blades normally determined based on the diameter of the classifying rotor and the amount of air, thereby reducing the mixing of fine powder in the coarse-grained product. At the same time, the effect of increasing the yield is obtained.

Claims (1)

It is rotatably installed by the vertical rotation axis of the classifying rotor formed with the air distribution cavity by a plurality of classing vanes arranged in the casing having the powder inlet in the center of the upper surface and the air inlet around the outer wall to extend in the axial direction from the periphery. In the powder classifier which classifies powder by the equilibrium of the centrifugal force which acts on powder by rotation of the said classification rotor, and the drag force which acts on the said main body by the airflow which passes through the said air distribution cavity part axially, The said classification apparatus WHEREIN: The number of blades is made less than the number of classification blades normally determined based on the diameter of a classification rotor and the quantity of air which passes through the said air distribution cavity part, The powder classifier characterized by the above-mentioned.

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