JPH06277629A - Spiral flow type air classification machine - Google Patents

Abstract

PURPOSE:To classify a raw material of a powder and granular body at a required classification point by setting the fixing pitch of blades to satisfy a specified equation in relating to the separating particle diameter in a classification machine wherein a plurality of spiral flow adjusting blades are provided on a rotor and a guide vane is provided on the outer periphery through a classification room. CONSTITUTION:A rotor 5 on the outer peripheral part of which a plurality of spiral flow adjusting blades 6 are fixed is stored under a condition of free rotation in the center of a cylindrical casing 1 wherein a conical hopper 2 on the bottom part of which an exit 3 for coarse powder is opened is provided on the lower part. Then, air for classification is fed in a classification room 7 from an air feeding path 11 through a guide vane 8 to form a free spiral flow and a raw material is fed from a raw material inlet 13 under a condition where a forcible spiral flow is formed by rotating the spiral flow adjusting blade 6 through a rotating shaft 4 and fine powder with at most a specified particle diameter is separated and is recovered through a product discharging exit 12. At this instance, an excellent accuracy of classification is obtd. by setting the fixing pitch P of the spiral flow adjusting blade 6 to a value satisfying the equation P<=1.04XDp(th)<0.365> in relation to the separation particle diameter Dp(th).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a swirl type air classifier used for classifying raw materials for powder and granular materials such as cement, calcium carbonate and ceramics.

[0002]

2. Description of the Related Art A conventional vortex type air classifier is used for powder and granular materials,
For example, disperse powdered particles such as limestone powder in the air flow,
The product is obtained by classifying the coarse powder portion and the fine powder portion by utilizing the balance between the centrifugal force and the anti-centering force, and putting the fine powder portion on the air stream and taking it out of the machine. (Japanese special public Sho 57-2
(See Japanese Patent No. 4189)

As is well known, the theoretical separation particle size D _p ( _th ) [m] of a vortex air classifier is obtained by the following general formula.

[Equation 4] In this general formula, V _t is the peripheral speed (m / s) of the tip of the vortex flow adjusting blade, μ is the viscosity coefficient of air (Pa · s), D is the rotor diameter (m), and V _r is the inward direction at the tip of the vortex flow adjusting blade. The wind speed (m / s) and ρ _p respectively represent the density of air. However, the particle Reynolds number R _ep = D _p ( _th ) Vrρf / μ <
2

[0004]

[SUMMARY OF THE INVENTION However, compared the general formula by the obtained theoretical separation diameter D _{p (th),} and the actual obtained by classification classifying particle diameter D _{p (o b s)} Then,
It was found that there is the following relationship between the two and they do not always match.

[Equation 5]That is, as the target separation particle size becomes smaller,
Separated particle size D_p (_{o b s} ) Is theoretical separation particle size D_p (
_th) Will be larger than.

The present inventor has found that the particle size D _p ( _th ) and the particle size D _p (
_As a result of studying the cause of the above relationship with _{o b s} ), the following was found.

As shown in FIG. 6, the tangential flow velocity distribution of the vortex flow in the vortex type air classifier equipped with the guide vane A8 and the vortex flow adjusting vane A6 which are opposed to each other through the classification chamber A7 is represented by W in FIG. . The separated particle size D _p is the tangential flow velocity V _{t A} , V _t
It is determined by the balance between the centrifugal forces F _{c A} and F _{c B} derived from _B and the air resistance forces F _{d A} and F _{d B} derived from the inward wind speed.

The separated particle diameter D _p gradually decreases on the radius from the guide vane portion A to the tip end portion B of the vortex flow adjusting blade, and increases again inside the tip end of the vortex flow adjusting blade.

Therefore, the guide vane A8 and the swirl adjusting vane A
Particles larger than the separation particle size at point B in the classification raw material charged between the No. 6 and 6 are recovered to the coarse powder side, and particles smaller than that are recovered to the fine powder side. That is, the separation particle size of this classifier is the separation particle size D _{p B} at point _B.

As described above, the separated particle size D _{p B} is determined by the tangential flow velocity V _{t B} and the inward wind velocity at this point, but the actual tangential flow velocity V _{t B} does not always match the rotor peripheral velocity. There is some delay. That is, the flow velocity at the point B of the tangential flow velocity distribution W of the vortex is slower than the rotor peripheral velocity R shown by the broken line.

On the other hand, V _{t B} in calculating the theoretical diameter D _{p (th)} is used rotor peripheral speed R. This is the cause of differences between the actual separation particle size D _p and theoretical diameter _{D p (th) (o b} s). In particular, when the rotor peripheral speed is high, there is a large difference between the tangential flow velocity and that of the guide vane portion, and it becomes difficult to perform sufficient acceleration during this time, and this tendency becomes remarkable. As is clear from the above, classification cannot be performed at a desired classification point using the general formula.

In view of the above circumstances, it is an object of the present invention to easily and accurately classify a powdery or granular material at a desired classification point.

[0012]

The inventor of the present invention has found that the factors considered to affect the classification point, for example, the spacing between the eddy current adjusting blades, that is, the mounting pitch P (m) and the separation particle size D _p ( _th ) (m). Experiments were performed by changing the above, and the results shown in FIG. 4 were obtained. In FIG. 4, the vertical axis represents the eddy current adjusting blade mounting pitch P (m), and the horizontal axis represents the separated particle size D _p (m). L _{1 to} L ₄ have separated particle diameters D _p ( _th ) of 2.9 μm, 4.8 μm, and 6.8, respectively.
The case of μm and 10.0 μm is shown.

As a result, the particle size D _p ( _th ) and the particle size D _p ( _o)
A straight line L was formed by connecting the respective classification points that coincide with _{b s} ). The relationship between the particle diameter D _p ( _th ) on the straight line L and the mounting pitch D can be expressed by the following P-D _p relational expression (1).

[Equation 6]

By substituting the general formula into the right side of the formula (1), the following formula (2) is obtained.

[Equation 7]

The diameter of the eddy current adjusting vanes and the rotor is D
The inward velocity V _r (m / s) can be expressed by the following equation (3), where (m), height H (m), and classification air volume Q (m ³ / s). V _r = Q / (πDH) (3)

From the equations (2) and (3), the corrected pitch equation (4) is obtained.

[Equation 8]

Therefore, the present inventor has installed a plurality of swirl adjusting blades in a rotor, and installing the swirl adjusting blades in a swirl type air classifier in which guide vanes are provided on the outer circumference of the swirl adjusting blades via a classification chamber. The pitch P is the separation particle size D _p ( _th )
It is intended to achieve the above object by a vortex type air classifier characterized by being obtained by a P-D _p relational expression in relation to.

[0018]

[Function] The theoretical separation particle size D _{p is} expressed by the Ρ-D _p relational expression (1).
( _Th ) is substituted to obtain the mounting pitch P of the eddy current adjusting blades,
The eddy current adjusting vanes are attached to the rotor at the pitch P. Then, the actual tangential flow velocity and the rotor peripheral velocity match, and accurate classification can be performed. Therefore, it is also possible to surely obtain the desired separation diameter D _{p (o b s)} in fine classification point.

[0019]

Embodiments of the present invention will be described with reference to the accompanying drawings. A conical hopper 2 is provided in the lower part of the cylindrical casing 1, and the lower part of the hopper 2 is communicated with the coarse powder discharge port 3.

A rotor 5 fixed to the rotating shaft 4 is arranged in the center of the casing 1. The rotor 5 has a diameter D and a height H.

A plurality of eddy current adjusting blades 6 are mounted on the outer peripheral portion of the rotor 5, and the mounting pitch P thereof is the modified pitch formula (4), that is,

[Equation 9] Required by.

Next, the particle density Ρp =
Pitch P when classifying 2700 kg / m ³ limestone
Will be described. Rotor diameter D = 2.1 m, rotor height H = 0.3 m, temperature 20 ° C., air density in air of 1 atm Ρ _f = 1.20 kg / m ³ , air viscosity coefficient μ = 1.81 × 10- ⁵ (Pa.s).

Under the above conditions, the theoretical separated particle size D _p (
Table 1 shows the mounting pitch P (m) of the eddy current adjusting blades required to achieve _th ) (m). This pitch P
The value of (m) may be determined from the P-D _p relational expression (1) as a classifier used for classification to the minimum separation particle size applied to the classifier, for example, 3 μm.

[Table 1] Note that Q indicates the classification air flow (m ³ / s), and Vt indicates the peripheral speed (m / s) at the tip of the vortex flow adjusting blade.

A guide vane 8 whose angle can be adjusted is disposed on the outer periphery of the vortex flow adjusting blade 6 via a classification chamber 7.
The determination of the width S of the classification chamber 7 is extremely important. The coarse agglomerates in the classification chamber are blown to the outside and collide with the guide vanes 8, where they are classified. Further, the steeper the velocity gradient of the tangential flow velocity distribution W, the stronger the shearing force due to the difference in the velocity of the air flow to the aggregates in this portion, and the classification is promoted. However, if the width S is too narrow, the vortex will be disturbed. As a result, the granular material causes diffuse reflection in the classification chamber, and normal classification cannot be performed.

On the contrary, when the width S of the classification chamber is widened, the classification action due to the collision of the guide vanes and the velocity gradient of the air flow described above becomes insufficient, and the agglomerated particles are not dispersed into the primary particles, but the classification chamber 7 Therefore, not only the classification effect is deteriorated, but also coarse particles are included in the refined powder.

Then, various experiments were conducted in order to determine an appropriate value of the width S of the classification chamber 7, and the following SP relational expression (5) could be obtained. However, the coefficient K = 5 to 20.

[Equation 10]

The ratio T / P between the pitch P (m) and the thickness T of the vortex flow adjusting blade 6 in the circumferential direction is set to 0.35 or less, and the opening area M of the rotor 5 is set to 65% or more.

According to an experiment, when the thickness T of the vortex flow adjusting blade 6 in the circumferential direction exceeds the above range, the width S of the classification chamber 7 and the mounting pitch P of the vortex flow adjusting blade 6 fall within the above range. Even if there is, the vortex flow in the vicinity of the vortex flow adjusting blade 6 may be disturbed, and for example, the coarse powder portion having a size of 3 μm or more may jump in frequently and sharp fine powder classification may not be possible.

On the contrary, when the opening area is less than the above range,
Although the thickness T becomes abnormally thin and there are problems in strength, material, structure, and construction, it is desirable that the thickness T be as thin as possible without causing the above problems.

This T / P is preferably 0.35 or less, but in view of the current technical strength, when performing sharp fine powder classification, for example, 3 μm cutting, the thickness T is T / P of 0.1. I know it's enough.

The opening area M of the rotor is preferably 65% or more because the pressure loss in the classifier is reduced if the opening area M is as large as possible in terms of structure, mechanical strength and fine powder classification.

Next, the operation of the embodiment will be described. The classified air is sent from the classified air supply passage 11 to the classification chamber 7 through the guide vane 8 to form a free vortex in the classification chamber 7, and the rotating shaft 4 is rotated to rotate the vortex flow adjusting blade 6 to generate a forced vortex. Form.

Then, these vortices swirl in the classifying chamber 7 and pass between the vortex flow adjusting blades 6 and the product discharge port 1
It is discharged from the 2 out of the machine.

In this state, when the material Y to be classified, for example, calcium carbonate, is introduced from the raw material inlet 13, the material Y to be classified collides with the dispersion plate 14 and drops into the classification chamber 7 while scattering in the outer peripheral direction.

Then, the raw material Y is struck by the strong centrifugal force on the surface of the guide vane 8, and the strong agglomerated particles are disentangled to the primary particles by the strong impact force to destroy the single particles, and more ideally. It is taken into the high-speed vortex of the vortex gradient without causing slip.

Then, the particles are classified by the balance action of the centrifugal force and the drag force of air. This classified fine powder Y ₂ , for example, a particle size of 5 μm or less, is loaded into an ascending airflow and is rolled.
While passing through the inside of the filter 5 and flowing into the product discharge port 12, it is also collected into an air filter (not shown).

Further, the coarse powder Y ₁ falls in the hopper 2 while swirling in the casing _{1, and} is discharged from the coarse powder discharge port 3.

The embodiment of the present invention is not limited to the above. For example, instead of providing the product discharge port of the vortex type air classifier above the classifier, it may be provided below the classifier.
Also, it can be applied to various rotor classifiers, such as providing a raw material inlet at the center of the upper part of the classifier, providing a product discharge port downward, and introducing the raw material inlet together with classification air on the side or below the classifier. It is a thing.

Further, the vortex type air classifier 100 of the present invention and the mill 110 may be combined as in the rigid mill shown in FIG. In FIG. 5, 101 is a raw material inlet for supplying the raw material Y to be crushed onto the table 111, and 112 is a roller.

Since the present invention is configured as described above, the theoretical separated particle size and the separated particle size obtained by actual separation match. Therefore, it is possible to reliably perform classification at a desired classification point.

The tangential flow velocity distribution of the vortex in the vortex type air classifier of the present invention is shown in FIG. 3, which is shown in FIG.
3, the rotor peripheral speed R and the tangential flow velocity distribution W of the eddy current in the vicinity of the eddy current adjusting blade 6 are the same in FIG. Therefore, unlike the conventional example, since the theoretically separated particle size becomes the separated particle size obtained by actual separation, accurate classification can be performed at a desired classification point.

[Brief description of drawings]

FIG. 1 is a partially sectional front view showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a diagram showing the operation of the present invention.

FIG. 4 is a diagram showing a relationship between a mounting pitch and a separated particle size.

FIG. 5 is a partial cross-sectional front view showing a second embodiment of the present invention.

FIG. 6 is a diagram showing a conventional example.

[Explanation of symbols]

5 Rotor 6 Eddy current adjusting blade 7 Classification chamber 8 Guide vane P Eddy current adjusting blade mounting pitch D _p ( _th ) Theoretical separation particle size μ Air viscosity coefficient ρ _p Particle density H Rotor height Q Classification air volume V _t Circumferential speed of the tip of eddy current adjusting blade S Width of classification chamber

Claims (4)

[Claims] 1. A vortex type air classifier in which a rotor is provided with a plurality of vortex flow adjusting vanes, and guide vanes are provided on the outer periphery of the vortex flow adjusting vanes through a classification chamber, wherein the mounting pitch P of the vortex flow adjusting vanes is separated. A vortex type air classifier characterized by being obtained by the following equation in relation to the particle size D _p ( _th ). [Equation 1] 2. A vortex type air classifier in which a plurality of swirl adjusting blades are provided on a rotor, and guide vanes are provided on the outer periphery of the swirling adjusting blades through a classifying chamber, wherein a mounting pitch P of the swirl adjusting blades is air. Coefficient of viscosity μ, particle density ρ _p , rotor height H, classification air volume Q, peripheral velocity V at the tip of the eddy current adjusting blade
An eddy current air classifier characterized by being calculated by the following equation in relation to _t . [Equation 2] 3. The width S of the classification chamber has a pitch P and a coefficient K.
The eddy-flow air classifier according to claim 1 or 2, wherein the relationship is calculated by the following equation. [Equation 3] 4. The vortex type air classifier according to claim 3, wherein K is 5 to 20.