JPH0852432A - Classification method and classification device - Google Patents

Abstract

PURPOSE:To decrease the amt. of air necessary for classification and to reduce the consumption of power by supplying the raw material and air to a rotating truncated conical inclined face to classify the raw material, discharging the coarse powder from the large-radius cone side and the fine powder from the small-radius side. CONSTITUTION:The inner cone 2, rotary casing 3 and outer casing 4 respectively having an inverted truncated conical shape expanding upward are concentrically arranged with the vertical shaft as the center. A raw material feed pipe 6 is allowed to pierce the inner cone 2 and communicated with an annular space 7 between the rotary casing 3 and inner cone 2, and a raw material M to be classified is supplied. An air feed pipe 8 is provided at the top 4a of the outer casing 4, and the air A is supplied downward into the annular space 7. The classifier 1 is rotated, the air A is supplied, and hence the fine powder is moved downward and discharged from a fine powder outlet 10 along with the air. The coarse powder is sent upward in the space 7, introduced between the rotary casing 3 and outer casing and discharged from a coarse powder recovery part 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a classifying method and classifying apparatus, and more particularly to a classifying method and apparatus for classifying powder particles such as cement raw material, cement clinker, ore, coal and ceramics.

[0002]

2. Description of the Related Art Conventionally, a wind power classifier has been used for classifying powder raw materials, particularly for classifying a large amount of powder, and as a typical wind power classifier used in the cement industry, Startevanto type, cyclone type, O-SEPA
(Trademark of Onoda Cement Co., Ltd.). In these wind force classifiers, all the particles to be classified are classified in the balance of gravity, wind force, and centrifugal force.

A typical way of receiving the force of the particles to be classified in such a wind classifier will be described with reference to FIG. The particles to be classified include the fluid resistance F in the centripetal direction due to the air flow and the centrifugal force mrw due to the rotational movement of the rotor blades.
² , and gravity mg acts, and balances by the following formula 1.

[0004]

[Equation 1]

In Equation 1, the Stokes
In the classification in the s) region, ignoring the buoyancy and frictional force received by the classified particles, and assuming that the particles move at the same velocity as the fluid, the fluid resistance F and the particle mass m are as follows in Equations 2 and 3
Can be expressed as

[0006]

[Equation 2]

[0007]

(Equation 3)

When the equations (2) and (3) to (1) are sorted by the separated particle diameter D _p , they can be expressed by the following equation (4). In the denominator of Equation 4, the value of (r ² w ⁴ + g ² ) is always a value of g ² or more. That is, in order to obtain the target separated particle diameter D _p , the wind speed V corresponding to a value of at least g is required.

[0009]

[Equation 4]

[0010] Here, D _p: separation particle diameter (m) m: particle mass (Kg) C _D: resistance coefficient (-) r: radius of gyration (m) ρ _f: air density (Kg / m ³⁾ w: Angular velocity (rad / sec) ρ _p : Particle density (Kg / m ³ ) F: Fluid resistance (Kg ・ m / sec ² ) μ: Viscosity coefficient of air (Pa ・ sec) g: Acceleration of gravity (m / sec ² ) V: Velocity (m / sec).

[0011]

As described above, the wind force has the same importance as gravity and centrifugal force, and in the conventional wind force classifier, particles ride on the air and oppose gravity and centrifugal force. It requires a large amount of wind power to move. Therefore,
The amount of air used for classification is large, and the power consumption of the fan is large. For example, in a vertical roller mill with a built-in classifier that grinds cement raw materials, the amount of electric power of a fan required for classification is comparable to the amount of electric power required for grinding.

The present invention provides a classifying method and a classifying apparatus which solve the above-mentioned drawbacks, reduce the amount of air required for classification, and significantly reduce the power consumption.

[0013]

In order to achieve the above-mentioned object, according to the classification method of the present invention, the raw material and air are supplied to a rotating truncated cone-shaped inclined surface to perform classification, and the radius of the truncated cone is determined. Of the large cone, the coarse powder is discharged, and the air and the fine powder are discharged from the small cone radius (Claim 1). The classifying device of the present invention is characterized by having a trapezoidal shape (claim 2), and has a means for supplying a raw material and air to a rotating truncated cone-shaped inclined surface. The coarse cone is discharged, and the air and the fine powder are discharged from the side with the smaller truncated cone radius (Claim 3), and the inverted truncated cone in which the rotating truncated cone-shaped inclined surface rotates about the vertical axis. Sloped surface (claim 4), vertical axis A rotary casing rotatably provided as a center, an internal cone arranged inside the rotary casing, a raw material supply pipe and an air supply pipe communicating with an annular space between the rotary casing and the internal cone, and the annular A coarse powder outlet provided above the space and a fine powder outlet provided below the space (Claim 5), wherein the rotary casing and the inner cone are concentrically arranged with respect to a vertical axis. A reverse conical shape (claim 6), further comprising an outer casing concentrically arranged outside the rotary casing, and communicating with the coarse powder discharge port to collect coarse powder below the outer casing. A portion is provided (Claim 7), and the outer casing has an inverted truncated cone shape (Claim 8).

[0014]

By utilizing a rotating truncated cone-shaped inclined surface, particles are mainly balanced by the component force of gravity and the component force of centrifugal force, and classification is performed with a small amount of air (fluid drag force). FIG. 2 is a diagram for explaining how the particles to be classified according to the present invention receive a force. When the particles to be classified are supplied to a rotating inclined surface and air is supplied downward to the inclined surface,
The particles to be classified are balanced by the equation 5 shown in the following equation. Note that θ
Indicates the inclination angle (°) from the vertical direction of the inclined surface, and other symbols are the same as those shown in the conventional example.

[0015]

(Equation 5)

The above-mentioned equations 2 and 3 to 5 are separated particle diameter D
Rearranging with _p , it can be expressed by the following equation (6). While the value of (r ² w ⁴ + g ² ) shown in the equation ⁴ is always a value of g ² or more, the value of (rw ² sin θ−g cos θ) in the equation 6 is the setting of the inclination angle θ. It can be 0 or more depending on the value. That is, according to the present invention, classification can be performed when the wind speed V is at least 0, and the air volume can be suppressed as much as possible.

[0017]

(Equation 6)

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described mainly with reference to FIG. 1 by taking a classifying device which rotates about a vertical axis as an example. However, the axis can be a horizontal direction other than the one described here. . In FIG. 1, a classification device 1 of the present invention
Is an inner cone 2 formed in the shape of an inverted truncated cone that expands from the inside to the top in order from the inside, the rotating casing 3,
The outer casing 4 and the outer casing 4 are arranged concentrically with each other about the vertical axis. The inner cone 2 is attached so as to hang from the top portion 4a of the outer casing 4,
The rotating casing 3 is provided rotatably about a vertical axis by a vertical rotating shaft 5 penetrating the inner cone 2.

The raw material supply pipe 6 penetrates the inner cone 2 to communicate with the annular space 7 between the rotary casing 3 and the inner cone 2, and the air supply pipe 8 is provided on the top portion 4a of the outer casing 4, From the outer periphery of the upper part of the inner cone 2 to the annular space 7
Is provided so as to communicate with above.

A coarse powder discharge port 9 is provided on the larger circular truncated cone radius of the rotary casing 3 formed in the shape of the inverted truncated cone, that is, above the annular space 7, and the coarse powder discharge port 9 is provided.
The coarse powder recovery unit 1 is provided below the outer casing 4 in communication with
1 is provided. On the other hand, a fine powder discharge port 10 is provided on the side having a smaller truncated cone radius, that is, below the annular space 7, and is connected to a collecting device such as a bag filter or a blower such as a fan (not shown).

The outer casing 4 does not necessarily have to be arranged concentrically with the rotary casing 3 as shown in the drawing, but may be in communication with the coarse powder discharge port 9 above the annular space 7 to collect the coarse powder. Various types of discharge devices such as a gravity type, a mechanical type, and an electric type can be applied. Further, the raw material supplied from the raw material supply pipe 6 may be of an air flow conveying system. In this case, the air supply pipe 8 may be omitted, or air from the air supply pipe 8 may be used in combination so that the raw material supply pipe 6 can be used. The raw material is introduced as a dust-containing air stream.

In such a classifying device 1, the rotary shaft 5 and the rotary casing 3 are rotationally driven by a driving device (not shown), and the classified raw material M is supplied from the raw material supply pipe 6 toward the inclined surface 3a of the rotary casing 3. It On the other hand, when the air A is introduced from the upper side of the annular space 7 to the lower side of the annular space 7 by a blower or the like (not shown) from the rear of the fine powder discharge port 10, the classified raw material M is represented by the above-mentioned equation 5. Centrifugal force component mrw ² sin θ and gravity component force m
It is classified according to the balance between gcos θ and wind force.

The particles having the target separation particle diameter D _p or more, which is shown by the above-mentioned equation 6, that is, the coarse powder which is largely affected by the centrifugal force component component, is the inverted frustoconical rotary casing 3 in the annular space 7. Move upward along the inclined surface 3a of
It is discharged from the coarse powder collecting section 11 below the outer casing 4 through the coarse powder discharge port 9. In addition, the target separation particle diameter D _p
The following particles, that is, fine powder, have a greater component of gravity than the component of centrifugal force and a larger fluid resistance of the air flowing downward in the annular space 7, and are discharged from the fine powder discharge port 10 together with air, and are not shown. It is collected by a collection facility such as a bag filter.

Here, the target separated particle diameter D _p can be appropriately adjusted depending on the rotation speed and the air volume of the rotary casing 3 as shown in the above-mentioned equation 6, but as described above, it is basically Can classify with a very small air flow.
Especially in the basic design of the classifying device, the rotating casing 3
Efficient classification is possible by suitably predetermining the inclination angle and raw material charging position. The inclination angle of the rotary casing 3 from the vertical direction can be set in the range of 0 to 90 degrees, that is, in an extremely wide range from almost vertical to horizontal, and especially the centrifugal force component which is also a feature of the present invention. It is desirable to set the inclination angle to about 20 to 60 degrees in consideration of the classification action at a low air volume due to the balance with the component force of gravity.

The classifying apparatus of the present invention described above can be suitably used for classifying various powders and granules. For example, classification of cement raw material by vertical milling, preliminary milling such as vertical milling, roll pressing, etc. In a cement clinker grinding system consisting of a combination of a crusher and a tube mill, it can be suitably used as a classifier for a preliminary crusher. By the way, when classifying the cement raw material of the vertical mill by the classifying device of the present invention in which the inclination angle of the classifying rotary casing 3 from the vertical direction is 30 degrees, it is compared with the conventional classifying by the vertical roller mill with a built-in classifier. As a result, an air flow reduction of about 30% could be realized.

[0026]

As described above, according to the present invention, the amount of air required for classification can be reduced and the power consumption can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a classification device of the present invention.

FIG. 2 is a diagram for explaining how to apply a force to particles to be classified according to the present invention.

FIG. 3 is a diagram for explaining how to receive the force of particles to be classified in a conventional air classifier.

[Explanation of symbols]

 1 Classifying device 2 Inner cone 3 Rotating casing 4 Outer casing 4a Top part 5 Rotating shaft 6 Raw material supply pipe 7 Annular space 8 Air supply pipe 9 Coarse powder discharge port 10 Fine powder discharge port 11 Coarse powder recovery unit A Air M Classified raw material

Claims (8)

[Claims] 1. A raw material and air are supplied to a rotating truncated cone-shaped inclined surface for classification, coarse powder is discharged from the one having a large truncated cone radius, and air and fine powder are discharged from a one having a small truncated cone radius. A classification method characterized by discharging. 2. The classification method according to claim 1, wherein the rotating truncated cone-shaped inclined surface is an inverted truncated cone rotating around a vertical axis. 3. A means for supplying a raw material and air to a rotating truncated cone-shaped inclined surface, wherein coarse powder is discharged from the larger truncated cone radius and air and fine powder from the smaller truncated cone radius. A classifying device characterized by discharging the. 4. The classifying device according to claim 3, wherein the rotating truncated cone-shaped inclined surface is an inverted truncated cone-shaped inclined surface which rotates about a vertical axis. 5. A raw material supply communicating with a rotary casing rotatably provided around a vertical axis, an internal cone arranged inside the rotary casing, and an annular space between the rotary casing and the internal cone. A pipe and an air supply pipe,
A classification device comprising a coarse powder discharge port provided above the annular space and a fine powder discharge port provided below. 6. The classifying device according to claim 5, wherein the rotating casing and the inner cone are arranged concentrically with each other about a vertical axis, and have an inverted truncated cone shape. 7. An outer casing concentrically arranged outside the rotary casing, further comprising a coarse powder recovery section provided below the external casing in communication with the coarse powder discharge port. The classification device according to claim 6. 8. The classification device according to claim 7, wherein the outer casing has an inverted truncated cone shape.