JPH0683818B2 - Powder classifier - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a powder classifier for classifying powder by utilizing the balance between centrifugal force and drag force exerted on the powder by a swirling airflow.

(Prior Art) For example, in a wheat milling process, a flat screen is used as a treatment after milling with a roll, but the screening of wheat flour having a fine grain size and having a large amount of skin is often not successful with a flat screen.

Conventionally, for classification of powders having such a relatively large particle size,
Uses an air classifier that accelerates particles using the swirling flow of air that flows in without using the centrifugal force generated by the rotation of a rotating body, and classifies powder particles due to the difference in work between the centrifugal force and the viscosity of air. Has been done. In this type of air classifier, the classified air is guided from the outside to the classifying chamber, a vortex is generated in the classifying chamber, powder is introduced into the vortex, and the balance between the centrifugal force and the drag due to the air flow is used. The powder is classified. The air flow flows in from the outside and is exhausted to the outside of the machine through the exhaust pipe at the center, but the separated fine powder component is contained in this exhaust, and the coarse powder component moves to the outer wall side of the classification chamber. The powder component should be collected.

The conventional air classifier used for such a purpose has a relatively inexpensive equipment and is economical to operate, but has a low processing capacity,
Moreover, there is a problem that the classification accuracy is lowered when the processing capacity is increased.

(Object and Structure of the Invention) The present invention has been made in view of the above points, and an object thereof is to improve the processing capacity and the classification accuracy. Place the top of the cone directly underneath, form a powder passage along the conical surface that extends from this top, and extend the lower end of this powder passage from the peripheral edge toward the axial direction at a predetermined angle. The guide vanes having the variable angles are arranged at substantially the center, and a central opening connected to the exhaust pipe is provided at the axial center below the cone and an air inlet is provided at the outer peripheral edge of the guide vane. A centrifugal force applied to the powder falling from the powder passage between the guide vanes due to the swirling flow of the air introduced from the air inlet by the exhaust pipe when passing between the guide vanes; Ba with drag A lance was used to classify the powder.

(Example) The present invention will be described below with reference to the drawings.

FIG. 1 is a vertical sectional view of an embodiment of the powder classifier according to the present invention, and FIG. 2 is a partially cutaway plan view of the classifier.

In the figure, reference numeral 1 is a funnel-shaped powder charging port, and a cone 2 for powder dispersion is provided immediately below the powder charging port so that the top part 2a is located. A conical cover 3 is provided so as to cover the conical body 2 and slightly apart from the conical surface.
The gap 4 between the conical surface and the conical surface is a powder dispersion passage 4.
The dispersion passage 4 is bent inward at the lower end in a dogleg shape.

A ring-shaped casing 5 is attached to the outer periphery of the lower end of the cone 2. The casing 5 is composed of upper and lower two-stage rings 5a and 5b. The upper stage ring 5a is fixed to the lower end of the cover 3, and a flange 7 forming an air inlet 6 is screwed to the peripheral edge.

An arm 81 is provided between the upper and lower rings 5a and 5b of the casing 5.
A ring-shaped partition plate 8 is provided, and a large number of upper guide vanes 9 divided into upper and lower stages by this partition plate 8 are provided.
a, 9b, 9c, ... and lower guide vanes 9a'9b'9c '...
Are arranged substantially parallel to each other along the circumferential direction. The upper and lower gaps divided by the partition plate 8 are preferably about 1: 1. The dogleg-shaped lower end of the dispersion passage 4 is the upper guide vane 9a,
It opens at almost the center of 9b, 9c, .... Guide vanes 9a, 9a '; 9 having elongated holes 8a, 8b, 8c, ... Which extend in the radial direction at equal intervals along the circumferential direction are formed near the outer periphery of the partition plate 8.
b, 9b '; 9c, 9c'; ... pin 10 provided at the outer end
, are engaged with the long holes 8a, 8b, 8c ,. On the other hand, the upper and lower guide vanes 9a, 9a '; 9b, 9b';
Pins 11a, 11b, 11 provided at the inner end portions of 9c, 9c ';
.. are pivotally attached to the upper and lower rings 5a and 5b of the casing 5.

Another disc is placed in the central opening of the lower ring 5b of the casing 5.
12 is attached, and an exhaust pipe 13 is connected to the central opening 12a. A fan and a bag filter are connected downstream of the exhaust pipe 13.

The tip of the arm 81 of the partition plate 8 is fixed to a female threaded ring 17 which is moved by operating the handle 14 from the outside. The handle 14 and the male threaded rod 15 form a part of the angle adjuster 20 for adjusting the angle of the guide vane, and
It is fixed to the lower surface of the lower ring 5b of the casing 5 by 16.

A hopper 21 for collecting classified coarse powder is provided on the lower side of the casing 5, and the lower end of the hopper 21 is connected to a rotary valve 22.

Next, classification of powder will be described.

The powder charged from the powder charging port 1 hits the top 2a of the cone 2 and is dispersed in eight directions, and falls downward through the dispersion passage 4.

On the other hand, rotating the fan connected to the exhaust pipe 13
When the pressure inside 13 is made negative, the outside air is introduced from the air inlet 6. The introduced air is the guide vanes 9a, 9b, 9c,
While flowing in from the outer peripheral direction of ..., the air flows into the guide vanes 9a, 9b, 9c, ... The air flow flowing between the guide vanes becomes a swirling flow as indicated by arrow A in FIG. 2 depending on the relationship between the vane direction and the position of the central opening 12a of the ring 12, and becomes a vortex flow toward the central opening 12a toward the exhaust pipe. Pour into 13.

By the way, the bottom surface 2b of the cone 2 and the guide vanes 9a, 9b, 9c,
A region between the inner peripheral side air passage of ... and a classification zone B is formed, and the powder dropped between the guide vanes through the dispersion passage 4 is uniformly accelerated by the air flow and is classified into the classification zone B. It is transported to and given centrifugal force. In the classification zone B, the fine powder having a relatively small particle size is carried close to the center due to the balance between the centrifugal force and the drag force due to the air flow, and is absorbed into the exhaust pipe 13 through the central opening 12a of the ring 12 to obtain the particle size. The relatively large coarse powder of # 1 drops into the hopper 21 through the opening C between the lower ring 5b and the ring 12 of the casing 5. Thus, the fine powder and the coarse powder are classified.

In this case, the classification point is determined by the magnitude of the centrifugal force applied to the powder, that is, the angle of the guide vanes and the air absorbing power of the fan connected to the exhaust pipe 13. However, if the number of rotations of the fan is not changed and kept constant, the classification point can be changed only by adjusting the angle of the guide vane.

Adjust the angle of the guide vanes as follows.

When the handle 14 of the angle adjuster 20 is rotated, the male threaded rod 15 is rotated, the female threaded ring 17 meshing with it is moved in one direction, and the arm 81 of the partition plate 8 is swung. The partition plate 8 rotates. When the partition plate 8 rotates, its long hole
Guide vanes 9a, 9a '; 9 pin-engaged with 8a, 8b, 8c, ...
Since b, 9b '; 9c, 9c'; rotate about the pins 11a, 11b, 11c, ..., the angle of the guide vanes can be changed.

When the angle formed by the guide vanes 9a, 9b, 9c, ... With respect to the radial direction increases, the acceleration of the powder particles increases, so that finer particles can be classified.

In order to confirm the effect of the present invention, an experiment for confirming classification points was performed on wheat flour.

FIG. 3 shows the change in the partial classification efficiency with respect to the mesh opening when the temporary set value S is changed.
It can be confirmed that it can be changed in the range of 100 to 190 μm.

FIG. 4 shows the change in the partial classification efficiency with respect to the mesh opening when the guide vane has one stage as in the conventional case and when the guide vane has two stages as in the present invention. In this case, the first-stage guide vanes are the total thickness of the second-stage guide vanes.

As can be seen from this figure, when the guide vanes are provided in two stages, the slope of the curve becomes steeper than in the case where the guide vanes are provided in one stage, and the classification accuracy is improved.

(Effect of the invention) As described above, in the present invention, the apex of the cone is arranged immediately below the granular material injection port at the center of the upper surface, and the powder passage is formed along the conical surface extending from the apex. The lower end of the powder passage is made to open at approximately the center of a plurality of guide vanes having variable angles, which are arranged so as to extend from the peripheral edge portion in the axial direction at a predetermined angle, and to the axial center portion below the conical body. A central opening connected to the exhaust pipe is provided, and an air inlet is provided at the outer peripheral edge of the guide vane, and when the air introduced from the air inlet due to exhaust by the exhaust pipe passes between the guide vanes, it becomes a swirling flow. Further, the guide vanes are divided into upper and lower two stages by partition plates, and the swirling flow distributes the powder by the balance between the centrifugal force and the drag force exerted on the powder falling from the powder passage between the guide vanes of the upper guide vane. Since the powder is treated so as to classify, the powder treating capacity is increased, and the swirling air flow surely imparts the swirling motion to the powder, so that the powder is uniformly accelerated and the classification accuracy is improved. In addition, air is introduced into the guide vanes from the periphery of the guide vanes toward the center, that is, along the radial direction, and then the guide vanes bend the air,
The direction of air can be reliably changed by the guide vanes, and the classification point can be changed. Further, by setting the guide vanes in the upper and lower stages, the powder introduced between the guide vanes is guided to the classification zone together with the air flow without settling, so that the particles are classified in a uniform mixed state and the classification accuracy is improved. Can be improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of the powder classifier according to the present invention, FIG. 2 is a partially cutaway plan view of the powder classifier, and FIGS. 3 and 4 confirm the effects of the present invention. Is a graph showing the experimental results for 1) powder input port, 2 ... cone, 2a ... top, 3 ...
Cover, 5 ... Casing, 6 ... Air inlet, 8 ...
Partition plate, 9a, 9b, 9c, ... 9a ', 9b', 9c '... Guide vane, 12a ... Central opening, 13 ... Exhaust pipe, 20 ... Angle adjuster

Claims (2)

[Claims] 1. A powder charging port is provided at the center of the upper surface, and a powder passage is formed along a conical surface extending from the top of a cone provided directly below the powder charging port. The lower end is located substantially at the center of the plurality of guide vanes arranged so as to extend from the peripheral edge portion in the axial direction at a predetermined angle, and the central opening connected to the exhaust pipe is provided at the lower axial center portion of the conical body. The guide vane has an air inlet on the outer peripheral edge of the guide vane, the guide vane is divided into upper and lower two stages by a partition plate, and the powder passage is opened between the upper guide vanes. When the air introduced from the air inlet becomes a swirl flow when passing between the guide vanes,
A powder classifier characterized by classifying powder by a balance between a centrifugal force and a drag force applied to the powder falling from the powder passage between the guide vanes by the swirling flow. 2. The powder classifier according to claim 1, wherein the direction of the guide vanes is variable.