JP3448716B2 - Eddy current air classifier - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In a conventional vortex type air classifier, a classification raw material is supplied from the upper side and enters a classification space while being dispersed by a dispersion plate. On the other hand, the air required for classification is fixed all around the classifier. It is sucked by the fan behind the classifier through the arranged guide vanes. At this time, the classified air starts a uniform vortex movement by the guide vanes, and is further accelerated by the rotor blade to a speed required for classification.

That is, when the space between the guide vanes and the rotor blade is defined as a classification space, the airflow there can be regarded as a two-dimensional vortex airflow. The particles supplied to the classification space start vortex motion together with this vortex flow, and are classified by the balance of centrifugal force and drag force acting on the particles at that time. As a result, particles smaller than the separated particle size determined by the balance between the two forces enter the rotor and are discharged and collected via the outlet duct.

On the other hand, large particles fall by gravity while being repeatedly classified in a classification space and discharged from a coarse powder discharge port. The separated particle size is controlled by the rotation speed of the rotor or the classified air flow rate, that is, the centrifugal force or drag force applied to the particles.

[0005]

When performing fine powder classification, it is necessary to give a strong centrifugal force to the powder particles. For that purpose, the rotation speed of the rotor blade must be increased.

However, when the rotation speed increases, the pressure loss of the air classifier increases due to the swirling and turbulent flow of air required for classification, so that the capacity of the fan for sucking air increases. Will be required. for that reason,
Equipment and investment become excessive, which is a major problem in saving resource energy.

The classification of powder such as cement falls into the category of fine powder classification, but it is a relatively coarse classification. Therefore, although the pressure loss is relatively low, the production amount of such powder is extremely large, the ratio of the energy cost to the powder price is large, and even a slight pressure reduction has a great influence.

The present inventor measured the pressure loss of the whole classifier and the pressure loss only outside the outer circumference of the rotor blade in order to find out where the pressure loss in the classifier mainly occurs. The results shown were obtained.

In FIG. 1, a curve A shows the pressure loss of the entire classifier, and a curve B shows the pressure loss only outside the outer circumference of the rotor blade. This curve B shows the dynamic pressure and static pressure at the outer circumference of the rotor blade. Was measured and the difference between the sum, that is, the total pressure and the total pressure at the classifier inlet was investigated.

According to this experiment, it was found that most of the pressure loss occurs inside the rotor, that is, inside the rotor chamber. Therefore, while investigating the cause of the pressure loss,
The method of reducing pressure loss in the rotor chamber was studied.

The pressure loss in the rotor chamber is (A) centrifugal force due to swirling of air, (B) fluid friction loss due to velocity difference between adjacent fluid particles, and (C) inner wall surface of the classifier and fluid. It is thought to be due to the friction of. In order to minimize the causes of (A) and (B), considering that the circumferential component of the air velocity in the rotor blade portion is the same as that in the rotor blade, swirling inside the rotor blade is considered. Is desired to be a forced vortex that has the smallest shearing stress between adjacent fluid particles, that is, the friction loss between the fluids and the smallest centrifugal force that is practically possible, and that has a constant rotational angular velocity at the rotor radial position.

However, in reality, the air flowing from the classification chamber into the rotor passes through between the rotor blades in a turbulent state while having the same peripheral velocity as the rotor blades, and enters the inside. Therefore, as the air moves toward the center of the rotor shaft due to its moment of inertia, the circumferential velocity component increases up to a certain radial position, from which Burg becomes a forced vortex.
A radial position that forms a vortex of ers and becomes the forced vortex is generally near the radius of the outlet of the rotor chamber. Therefore, it has been found that by extending the inner diameter of the rotor blade up to the radius of the exhaust port of the rotor chamber, it is possible to form a forced vortex without forming a Burgers vortex.

In view of the above circumstances, the present invention aims to reduce pressure loss.

As a result of the above research, the present inventor intends to achieve the above object by constructing the present invention as follows. A rotor chamber having an inlet and an exhaust port, a plurality of rotor blades provided at the inlet of the rotor chamber at intervals in the circumferential direction of the rotor, and a classification chamber provided on the outer periphery of the inlet of the rotor chamber. in vortex type air classifier provided with; before
The rotor blades are spaced apart in the radial direction of the rotor.
The vortex flow is arranged in a plurality of rows, and the rotor radial length of the rotor blade is 0.7 to 1.0 times the difference between the outer radius of the rotor blade and the radius of the exhaust port of the rotor chamber. Type air classifier.

[0015]

[Function] The fluid flowing from the classification chamber to the inlet of the rotor chamber is
While coming into contact with the rotor blade, it passes through the inside of the rotor blade and is discharged to the outside of the machine from the exhaust port of the rotor chamber. At this time, the fluid in the rotor chamber becomes a forced vortex without forming a Burgers vortex, so that the pressure loss is drastically reduced.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. 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 a rotary 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 rotor blades 6 are attached to the outer peripheral portion of the rotor 5, and the attachment pitch p is determined by the following equation (1) or equation (2) obtained by experiment. (See Japanese Patent Application No. 5-74670). p ≦ 1.04 × Dp (th) ^0.365 (1)

[0019]

[Equation 1]

Next, under the following conditions, 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 ρ _f = 1.20 kg / m ³ in air at 1 atm, air viscosity coefficient μ = 1.81 × 10- ⁵ (Pa.s).

Under the above conditions, the theoretical separation particle size D _p (
Table 1 shows the mounting pitch p of the rotor blades required to achieve the above ( _th ). The value of this pitch p is the minimum separation particle size applied to the classifier from the above formula (1), for example, 3 μ.
It may be determined as a classifier applied to classification up to m.

[Table 1]

Note that Q represents the classification air flow (m ³ / s), and Vt represents the peripheral speed (m / s) at the tip of the rotor blade.

A classification chamber 7 is provided on the outer periphery of the rotor blade 6.
A guide vane 8 whose angle can be adjusted is provided via the. The mounting angle θ _G of the guide vane 8, that is, the inclination angle of the guide vane 8 with respect to the tangent line L is obtained by the following equation.

[0024]

[Equation 2]

Details of the equation (3) are disclosed in Japanese Patent Application No. 305599/1993 based on FIG. 4 which is a principle diagram. In this equation (3) and FIG. 4, R1 is the radius of the circumscribed circle BC of the rotor blade 6, and R2 is the guide vane 8
Radius of the inscribed circle GC of ω1, ω1 is the angular velocity of the rotor blade 6, ω2 is the angular velocity of the air stream entering the classification space, Ur is the radial velocity component of the classifier of air velocity, ρp is the particle density, and S is the size of the classification chamber 7. The width and O indicate the center of the classifier, respectively.

If the mounting angle θG of the guide vane 8 is not proper, a delay with respect to the air velocity occurs, which causes wear of the rotor blade and excessive energy consumption. Therefore, the mounting angle θG is obtained by the above formula, and for example, the mounting angle θG is set to 15 degrees.

Next, the determination of the width S of the classification chamber 7 is extremely important. The steeper the velocity gradient of the tangential flow velocity distribution is, the stronger the shearing force due to the velocity difference of the air flow acts on the agglomerates in this portion. Classification is promoted. However, if the width S is too narrow, the vortex will be disturbed. As a result, the particles do not reach a predetermined speed and normal classification cannot be performed.

On the contrary, if the width S of the classification chamber is too wide, a uniform vortex cannot be formed, and the agglomerated particles will leave the classification chamber 7 without being dispersed into the primary particles, so that the classification is performed. The effect gets worse.

Then, various experiments were conducted to determine an appropriate value of the width S of the classifying chamber 7, and the following formula was obtained. However, p is the pitch of the rotor blades,
The coefficient K is 5 to 20 (m ^1/2 ). S = K√p

It is also important to determine the circumferential thickness T of the rotor blade 6. The ratio T / p between the thickness T and the pitch p is 0.
35 or less, and the opening area M of the rotor 5 is formed to be 65% or more.

According to an experiment, when the thickness T of the rotor 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 rotor blade 6 are within the above range. In some cases, the vortex flow near the rotor blades 6 is disturbed, the number of coarse powder particles having a size larger than the separation particle size is increased, and sharp fine powder classification cannot be performed.

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 and construction, it is desirable that the thickness T be as thin as possible without causing the above problems.

The ratio T / p between the thickness T and the pitch p is 0.
It is desirable that the thickness T is 35 or less, but from the viewpoint of the current technical strength, it is known that when the fine fine powder classification, for example, 3 μm cutting is performed, the thickness T is T / P of 0.1.

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

In order to form a forced vortex without forming a Burgers vortex, the length B of the rotor blade 6 in the rotor radial direction is set.
According to experiments, w, that is, the length obtained by subtracting the inner radius R3 of the rotor blade from the outer radius R1 of the rotor blade is 0.7 to 1 which is the difference between the outer radius R3 of the rotor blade and the radius R0 of the exhaust port 30 of the rotor chamber RT. It was found that the optimum range was 0.0 times.

Next, the operation of the embodiment will be described. Classifying air is sent from the classifying air supply passage 11 to the classifying chamber 7 through the guide vane 8 and the rotating shaft 4 is rotated to rotate the rotor blade 6 to form a vortex in the classifying chamber 7.

Then, the vortex flow is swirled in the classifying chamber 7, the flow direction is changed upward by passing between the rotor blades 6 at the inlet IN of the rotor chamber RT, passing through the exhaust port 30, and discharged from the discharge duct 12 to the outside of the machine. To be done. In this state, when a material to be classified Y, for example, calcium carbonate, is introduced from the raw material inlet 13, the material to be classified Y collides with the dispersion plate 14 and falls into the classification chamber 7 while scattering in the outer peripheral direction.

During this time, the particles of the material to be classified are accelerated by the vortex flow and swirl in the classification chamber. At this time, the particles are classified by the shearing force of the eddy current and the collision friction between the particles due to the shearing force, while the particles having a size smaller than the separated particle size determined by the balance between the centrifugal force and the drag force reach the outer peripheral portion of the rotor blade.

The classified fine powder Y ₂ , for example, a particle size of 5 μm or less, passes through the inside of the rotor chamber RT, rises, flows into the exhaust duct 12, and is collected in an air filter (not shown).

At this time, the air flow in the rotor chamber RT is Burg
Since it becomes a forced vortex without forming an ers vortex, the pressure loss in the rotor chamber is drastically reduced.

The coarse powder Y ₁ falls in the hopper 2 while swirling in the classification chamber 7 and is discharged from the coarse powder discharge port 3.

A second embodiment of the present invention will be described with reference to FIG. The feature of this embodiment is that the rotor blades are divided in the radial direction of the rotor, the rotor blades 6a and 6b are arranged, and the distance F between the blades 6a and 6b is set so that the forced vortex does not collapse. In this embodiment, the rotor blade 6
The pressure loss due to the friction between the surface of a and 6b and the fluid can be further reduced.

A third embodiment of the present invention will be described with reference to FIG. The feature of this embodiment is that the rotor blades 6a, 6b, 6
When the number of c in the circumferential direction is large and the pitch p is small, the rotor blades 6a are divided so that the forced vortex does not collapse.
This is to reduce the number of 6b and 6c uniformly toward the rotor center O. In this embodiment, the pressure loss due to the wear of the rotor blade surface and the fluid is further reduced, and the rotor blade is easily machine-manufactured.
The weight and the manufacturing cost can be reduced.

A fourth embodiment of the present invention will be described with reference to FIG. The feature of this embodiment is that a raised body 50 is formed on the bottom surface 5a of the rotor 5 of the rotor chamber RT so as to rise from the inscribed circle radius R3 of the inner rotor blade 6b. The ridge 50 is formed in a conical shape.
Of the slope (busbar) 50a of the bottom surface 5a, that is,
The rising angle θ must not be too large or too small. Then, as a result of the experiment, it was found that the angle θ obtained by the following equation in relation to the height H of the rotor 5 is the optimum value.

Θ = tan ⁻¹ {0.3 to 0.6} H / R ₃ }

In this embodiment, the air Ar horizontally swirling in the classification chamber 7 changes its direction while being guided by the ridge 50 through the rotor blades 6a and 6b, and is discharged through the exhaust port 30 of the rotor chamber RT. It is discharged to the duct 12. Therefore, the air Ar flows smoothly without causing stagnation in the lower portion inside the rotor, and the pressure loss is reduced.

A fifth embodiment of the present invention will be described with reference to FIG. The feature of this embodiment is that the radius R0 of the exhaust port 30 of the rotor chamber RT is 0.4 to 0.8 of the outer radius R1 of the rotor blade 6.
That is double the size. In this embodiment, the rate of air that reaches the vicinity of the central axis of the rotor can be reduced, so that the pressure loss can be reduced.

A sixth embodiment of the present invention will be described. The feature of this embodiment is that the rotating shaft 4 of the rotor 5 is formed to be 0.2 to 0.4 times thicker than the outer peripheral radius R1 of the rotor blade. In this embodiment, the rate of air that reaches the vicinity of the rotor central axis can be reduced, so that the pressure loss can be reduced.

A seventh embodiment of the present invention will be described. The feature of this embodiment is that the first to sixth embodiments are appropriately combined. For example, a combination of the fourth embodiment of FIG. 7 and the second embodiment of FIG. 5, the third embodiment of FIG. 6, or the sixth embodiment, or the sixth embodiment and the second embodiment of FIG. This is to be combined with the embodiment or the third embodiment of FIG. In this way, by appropriately combining the respective examples, it is possible to obtain a classifier with less pressure loss.

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

[0051]

Since the present invention is constructed as described above, a large pressure loss does not occur in the rotor chamber.
Therefore, the pressure loss of the entire classifier is significantly reduced as compared with the conventional example.

Further, of the energy required for the air classifier, the ratio of the fan that sucks air is high, and the energy required for the fan is proportional to the pressure loss, so the power of the fan can be reduced by several tens of percent compared to the conventional example.

When the rotor blade of the present invention M and that of the conventional example L were constructed as shown in FIGS. 9 and 10, respectively, and pressure loss experiments were conducted, the results shown in FIG. 8 were obtained.
As is clear from FIG. 8, the pressure loss in the present invention M was about 65% of that in the conventional example L, and the difference between the two L and M increased as the rotor rotation speed increased.

In FIGS. 9 and 10, a is 122 m
m is the radius of the exhaust port, b is the outer radius of the rotor blade of 205 mm, c is the inner radius of the rotor blade of 189 mm, d is the inner radius of the outer rotor blade 6 of 195 mm, and e is the inner radius of the rotor blade of 165 mm. 6, and f is the inner radius of the inner rotor blade of 150 mm. Of course, the classification air flow rate is the same in both experimental examples.

[Brief description of drawings]

FIG. 1 is a diagram showing a pressure loss of an entire vortex type air classifier and a pressure loss outside a rotor blade.

FIG. 2 is a partial cross-sectional view of the front view of the classifier showing the first embodiment of the present invention.

FIG. 3 is a vertical sectional view taken along line III-III in FIG.

FIG. 4 is a diagram showing an airflow model in a cross section of the classification chamber.

FIG. 5 is a diagram showing a second embodiment of the present invention.

FIG. 6 is a diagram showing a third embodiment of the present invention.

FIG. 7 is a vertical sectional view showing a fourth embodiment of the present invention.

FIG. 8 is a diagram showing pressure losses of the present invention and a conventional example.

9 is a diagram showing a rotor blade of the present invention used in the experiment of FIG.

10 is a diagram showing a conventional rotor blade used in the experiment of FIG.

[Explanation of symbols]

4 Rotor rotation axis 5 rotors 6 rotor blades 7 classification room 30 Exhaust port of rotor chamber 50 Ridges IN Rotor room entrance R0 Rotor chamber exhaust port radius R1 Rotor blade inner radius R2 Rotor blade outer radius

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-303560 (JP, A) JP-A-4-244275 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B07B 1/00-15/00

Claims (9)

(57) [Claims] 1. A rotor chamber having an inlet and an exhaust port, a plurality of rotor blades provided at the inlet of the rotor chamber at intervals in the circumferential direction of the rotor, and an outer periphery of the inlet of the rotor chamber. A vortex air classifier having a rectifying chamber; and the rotor blades spaced in a radial direction of the rotor.
And the rotor radial direction length of the rotor blade is 0.7 of the difference between the outer radius of the rotor blade and the radius of the exhaust port of the rotor chamber.
A swirl type air classifier characterized by being ~ 1.0 times. 2. A rotor chamber having an inlet and an exhaust port, a plurality of rotor blades provided at the inlet of the rotor chamber at intervals in the circumferential direction of the rotor, and an outer periphery of the inlet of the rotor chamber. A vortex air classifier having a rectifying chamber; and the rotor blades spaced in a radial direction of the rotor.
And the rotor radial direction length of the rotor blade is 0.7 of the difference between the outer radius of the rotor blade and the radius of the exhaust port of the rotor chamber.
The vortex air classifier is characterized in that the radius of the rotating shaft of the rotor is 0.2 to 0.4 times the outer radius of the rotor blade. 3. A rotor chamber having an inlet and an exhaust port, a plurality of rotor blades provided at the inlet of the rotor chamber at intervals in the circumferential direction of the rotor, and an outer periphery of the inlet of the rotor chamber. A vortex air classifier having a rectifying chamber; and the rotor blades spaced in a radial direction of the rotor.
And the rotor radial direction length of the rotor blade is 0.7 of the difference between the outer radius of the rotor blade and the radius of the exhaust port of the rotor chamber.
The vortex air classifier is characterized in that a ridge-shaped body that restricts an air flow is arranged on the bottom surface of the rotor. 4. A rotor chamber having an inlet and an exhaust port, a plurality of rotor blades provided at the inlet of the rotor chamber at intervals in the circumferential direction of the rotor, and an outer periphery of the inlet of the rotor chamber. A vortex air classifier having a rectifying chamber; and the rotor blades spaced in a radial direction of the rotor.
And the rotor radial direction length of the rotor blade is 0.7 of the difference between the outer radius of the rotor blade and the radius of the exhaust port of the rotor chamber.
.About.1.0 times, the radius of the rotor rotation axis is 0.2 to 0.4 times the outer radius of the rotor blade, and a ridge-shaped body for restricting airflow is arranged on the bottom surface of the rotor. A swirl type air classifier. 5. The vortex type air classifier according to claim 1, 2, 3 or 4, wherein the rotor blades have an equal interval. 6. The number of rotor blades on the rotor center side is
Number of rotor blades outside the rotor that are evenly thinned
5. The vortex type air classifier according to claim 1, 2, 3, or 4, characterized in that it is arranged in a smaller number . 7. A rotor tray having a radius of an exhaust port of a rotor chamber
Claim, characterized in 0.4-0.8 Baidea Rukoto de outer peripheral radius 1,2,3, or vortex type air classifier according 4. 8. The raised body extends from the inner circumference circle of the rotor blade.
A cone that rises conically toward the rotation axis of the data
The vortex type air classifier according to claim 3 or 4, wherein the vortex type air classifier is a shape . 9. The angle θ of the slope of the conical body with respect to the bottom surface is
From the relationship between rotor height H and rotor blade inner diameter R3
The vortex air classifier according to claim 8 , wherein the vortex type air classifier is obtained by the following equation . θ = tan ⁻¹ {(0.3 to 0.6) H / R ₃ }