JPS6044031B2 - Structure of classification impeller for powder classification equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a rotary classification impeller for a powder classification device.

Conventionally, there are various known powder classifiers in which raw material powder to be classified (hereinafter simply referred to as raw material) is conveyed with an air flow into a classification chamber of the classifier and classified by a rotating classification impeller, one example of which is shown in Figure 1. As shown in the cross-sectional view of the main parts of a known rotary classification impeller, the rotary classification impeller R has the classification blade B as its axis o.
Some types are arranged more radially, and in this type, the bending strength against the applied centrifugal force is such that the direction in which the centrifugal force is applied matches the longitudinal direction of the blade cross section, and the moment of inertia of the classifying blade cross section is It is advantageous in terms of strength because it can be set high.

In this type of classification impeller, the classification impeller B,
The airflow a near the outer peripheral edge of the rotation tends to be disturbed, and a part of the airflow a is drawn into the rear surface Br side of the rotating front surface Bf of the classification vane, and the entrained airflow u is The mixed coarse powder particles or flowing particles tend to pass between the classification blades B and enter the fine powder region sorted by the device, which may result in extremely low classification accuracy. In addition, the radially arranged classification blades B are not arranged with consideration given to the smooth inflow of airflow, and therefore exhibit excessive resistance to the inflow of airflow and fine powder, increasing pressure loss and causing rotation. This system has the drawback of increasing the power loss of the entire device, including the driving power of the classification impeller and the power of the windmill that is the driving source for the air flow. Another known example is a classification impeller R that rotates the classification blades as shown in the sectional view of the main part shown in FIG. Axis center 0 direction・
The classification impeller R rotates its outer peripheral end toward the direction. In the case where the classification blade B is tilted backward in the opposite direction of rotation, the classification blade B is
. The actual width of R is quite large, so the rotating classification impeller R is used. The centrifugal force F accompanying the rotation of the classification blade B. A considerably large bending load W acts on the classification blade B. Due to the strength of the rotary classification impeller R, there are certain restrictions on the size and rotation speed of the rotary classification impeller R, so it is possible to increase the rotation speed to make the classification point of the sorted particles smaller, or increase the size to expand the processing capacity. This has been a hindrance to the aim of improving classification accuracy and efficiency by operating in a high speed range or in a high rotation range. In view of these points, it is an object of the present invention to provide a rotary classification impeller that can be used in a powder classification apparatus and has low pressure loss, can rotate at high speed, or can be made large. Next, the structure of the present invention will be explained with reference to the following examples.

In the figure, 4 is the casing, and there is a fine powder outlet 2 near the center of the upper end.
, a coarse powder outlet 3 and a raw material inlet 1 are arranged at the bottom. Reference numeral 7 denotes a rotary shaft for rotating a rotary classification impeller 6 attached to the rotary shaft by an electric motor 14, and the fine powder outlet 2 is disposed above the rotary classification impeller 6.

The fine powder outlet 2 includes a cyclone collector (not shown),
A classification chamber 11 is connected to the windmill via a bag filter or the like, and a classification chamber 11 is provided between the rotary classification impeller 6 and the casing 4.
is formed. The rotary classification impeller 6 includes a classification blade 5, an upper ring 8 for holding the classification blade 5, a lower ring 9, and a conical cover 1 disposed below the lower ring 9.
0, and the upper ring 8 is composed of the upper ring 8
The structure is such that airflow and fine powder cannot easily pass through to the fine powder outlet 2 through the gap between the upper surface of the casing 4 and the classifying blades 51,
52 and 53 are arranged in multiple stages radially from the axis 0 of the rotary classification impeller 6 toward the outer periphery by the upper ring 8 and the lower ring 9, and the direction in which centrifugal force is applied matches the longitudinal direction of the blade cross section. The moment of inertia is set sufficiently large to solve the strength problem, and the classification blades 51,5. , 53 is arranged so that a slight gap is maintained in the rotational direction of the rotary classification impeller 6 from the outer periphery of the rotary classification impeller 6 toward the axis 0, and the rotational peripheral dimension gradually decreases. Overlapping. A plurality of classification blades 51, 52, 53 arranged together form a classification blade group 5, and in addition to providing a plurality of sets, the intervals between each group of these classification blade groups 5 are set to the individual classification blades 51, 52, 53.
The arrangement is such that the gap is wider than the gap between 52 and 53, thereby suppressing an increase in the resistance of the air flow S2 due to rotation. a conical cover 10 disposed under the lower ring 9;
is arranged at a position facing the raw material inlet 1, and the raw material inlet 1
This is to smoothly guide the airflow and raw materials brought into the classification chamber 11. Note that 12 is an air sieve ring, and 13 is a secondary air blowing pipe, both of which are provided as necessary. With the above configuration, the raw material carried in with the airflow from the raw material inlet 1 is transferred to the conical cover 10 disposed above the raw material inlet 1.
The raw material is smoothly guided into the classification chamber 11 along the surface of the material, and within the classification chamber 11, the raw material is given a circular motion by the rotation of the rotating classification impeller 6 along with the airflow, and the coarse particles are separated from the outer periphery by centrifugal force. Then, the fine powder particles smoothly pass between the classification blades 5 composed of multiple stages together with the flowing air stream S2, and are discharged to the fine powder outlet 2.

Incidentally, the coarse powder particles that have moved to the outer periphery of the classification chamber 11 and have been classified and sorted have their rotational speed reduced by friction with the inner wall surface of the casing 4, descend along the inner wall surface due to their own weight, and collect at the coarse powder outlet 3, where they are collected by the machine. is discharged outside. Further, the fine powder particles discharged from the fine powder outlet 2 are collected by a cyclone collector, a bag filter, etc., and the air flow used for the conveyance, classification, and separation is recirculated and used or discharged to the outside of the apparatus. Further, by secondarily introducing an airflow separately prepared from the secondary air blowing pipe 13, an upward airflow is applied near the inclined downstream end of the wind sieve ring 12, and the coarse powder descends on the inclined surface. This is to apply the air sieving action of the upward airflow to the particle group again, to separate the fine powder particles adhering to and mixed with the coarse powder particles, to raise them, and to send them into the classification chamber 11 again. This is useful for improving the fine powder mixing rate in the powder, that is, the fine powder recovery rate.The classification blades 51, 5, and 53 have a classification effect in combination with the fact that the closer the axis center is to 0, the less the applied load is. In other words, each gap between the classification blades 51, 52, 53 of one group is narrower than the gap between adjacent groups, and the width of the classification blades 51, 52, 53 is narrower than the gap between adjacent groups. Since the tip portions are located almost at the outer periphery, even if the amount of overlap in the circumferential direction is small, the classification accuracy will not be impaired. The feature is a plurality of small classification blades 51, 5 arranged inside the rotating classification impeller 6.

, 53 are successively stacked one on top of the other, the depth of the rotating blades described above can be maintained, and the classification blades 51, 5, respectively. , 53, the entrainment of airflow to the back side of the classification blade is small, and the airflow and the classified fine powder are smoothly discharged to the fine powder outlet 2 without receiving unnecessary resistance. In this example, the classification blade is 51.5. , 53, but as other embodiments, the classification blade 53 is omitted for a small size, or 51, 5 for a large size. ,53・
The present invention can be carried out even if a large number of rows are arranged. As described above, according to the present invention, the deterioration in classification accuracy due to the turbulence of the airflow that conventionally occurs near the classification blades is eliminated, and the inflow resistance when the flowing air current passes through the classification blades is reduced, and the device is operated. The required power is reduced, the restriction on the strength of the classification blade is resolved, so the rotation speed can be further increased to set the classification point of the sorted particles to be extremely small, and the processing capacity can be increased by further increasing the size. Further, the present invention is extremely useful industrially, as classification accuracy can be greatly improved by operating in a high speed rotation range.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the main parts of a conventionally known rotary classification impeller;
The figure is a sectional view of a main part of another known example, FIG. 3 is a sectional view of a main part of an embodiment according to the present invention, and FIG. 4 is a sectional view taken along the line AN in FIG. 3. In the figure, 1... Raw material inlet, 2...
Fine powder outlet, 3... Coarse powder outlet, 4... Casing, 5... Classifying blade, 6... Rotating classification impeller, t...・Outer periphery, S2...
It is a popular trend.

Claims (1)

[Claims] 1 A raw material inlet 1 for carrying in the material to be classified with the airflow, a fine powder outlet 2 for carrying out the classified and sorted fine powder together with the air flow, and a lower coarse powder outlet 3 for discharging the classified and sorted coarse powder by its own weight. In the powder classification device, a rotary classification impeller 6 in which classification blades 5 are arranged in a cylindrical or truncated conical shape is disposed in a casing 4 equipped with the above-mentioned The rotary classification impeller 6 has a plurality of classification blades 5_1, 5_2, 5_3 which are arranged radially and stacked one on top of the other in such a way that a slight gap is maintained from the outer periphery toward the rotational direction side, and the rotational outer circumferential dimension is gradually reduced.・・・
A plurality of classification blade groups 5 are provided, and the intervals between each group of these classification blade groups 5 are set to the individual classification blades 5_1, 5_2, 5_3...
...The structure of a classification impeller for a powder classification device characterized by being wider than the gap between the impellers.