JPH07108386B2 - Classifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an airflow-type classification apparatus for separating an object to be classified (classification raw material) into fine powder and coarse powder.

[Prior Art] An airflow classifier is widely used for classifying powder particles such as cement raw materials, coal, and chemicals. A startate type air separator has been used for a long time in air flow type powder classifiers (for example, Handbook of Chemical Engineering, No. 4).
Edition, p. 1079). Further, as an attempt to improve the classification efficiency, a casing having a substantially cylindrical upper portion and a conical hopper lower portion, a horizontal rotating plate installed rotatably driven by a vertical shaft inside the casing, and Various classifying devices equipped with a vortex flow adjusting piece or the like mounted vertically on a rotating plate have also been proposed (for example, Japanese Patent Publication No. 57-2418).
9).

In this classification device, the classification airflow is introduced in the swirling direction from the side surface of the cylindrical portion of the casing through the guide vanes. on the other hand,
The classification raw material is introduced from the top of the casing, is given a centrifugal force by the dispersion plate to be dispersed, collides with the side wall of the casing, is turned downward, and is introduced into the classification space. The rotating plate and the eddy current adjusting piece are rotationally driven at a peripheral speed higher than the circumferential speed of the classification airflow, accelerate the swirling direction speed of the classification airflow, and directly hit the classification raw material to produce the classification raw material. On the other hand, a centrifugal force is applied outward in the outer peripheral direction.

Then, the fine powder has an inward air flow conveying force higher than an outward centrifugal force, moves toward the center along with the air flow, and is fed into the fine powder discharge pipe. On the other hand, the coarse powder passes through the classification space while flowing along the guide vanes due to the centrifugal force exceeding the inward conveying force, and falls into the hopper at the lower part of the casing.

In addition, when explaining the separation action of this coarse powder in detail, the raw material in the classification space continuously undergoes the classification action and reduces the amount itself, that is, the concentration (the amount of the classified raw material passing at a certain point in the vertical direction of the classification space). And the classification air amount [kg / m ³ ]) are gradually reduced while turning downward.

In the process of swirling and descending the raw material in this classification space, particles having a smaller flow diameter move toward the center above the classification space and are separated from coarse powder. In other words, the proportion of particles present in the classification space and the flow diameter of the particles are as follows when viewed in the vertical direction of the classification space.

(A) The particle concentration is higher in the upper part of the classification space and lower in the lower part.

For example, if the concentration at the upper entrance of the classification space is 100%,
It will be about 50% to 70% at the lower exit.

(B) Regarding the particle size of the particles, the higher the classification space, the greater the amount of fine powder, and the lower the classification space, the smaller the proportion of fine powder.

From this, particles having a smaller particle size are collected in the upper part of the classification space, and particles having a larger particle size are collected in the lower part.

[Problems to be Solved by the Invention] As described above, in the above-described conventional classification device, particles having a smaller particle size are collected in the upper part of the classification space, and particles having a larger particle size are collected in the lower part. It is promoted by the influence of (a). This means that the average classification particle size xc shifts from finer to coarser as it goes downward in the classification space, and the synthesized total classification performance is as shown in Fig. 10. Will be damaged.

In addition, the general characteristics of the airflow classifier are that, as shown in FIGS. 6 and 7, when the amount of the classification material supplied to the classifier is increased, other operating conditions are kept constant. The proportion of some of the classified raw materials that fall through the classification space without being classified, that is, the so-called division (or bypass) increases, and the particle size of the fine powder to be classified and collected tends to shift to fine powder. That is, as shown in the partial classification rate curve in FIG. 8, the partial classification rate curve shifts to the fine grain side depending on the supply amount, and the particle size xc (in the main part) of the median number (50%) of the portion involved in classification The average classified particle size) shifts to a smaller particle size. This phenomenon is a major factor that determines the classification particle size, 1) centrifugal force given to the particles entrained by the inflow direction and velocity of the classification airflow in the classification space, 2) the radial inward velocity component of the airflow Viscous force on particles, 3) In addition to the three main factors of direct and indirect centrifugal force exerted on particles of a rotating classifier, the classifying material itself dispersed and suspended in the classifying airflow is as if it were a powder cloud. It is caused by the fact that it behaves like and exhibits a filter effect. In other words, as the raw material supply increases, the probability of stall due to the collision of particles with each other, the change of direction of movement, the adhesion and aggregation, etc. changes, and the larger the particle size, the greater the effect, and the inward passage probability of the classification space. Is decreased, and the average classified particle size xc shifts to fine particles.

Further, in the above conventional classification device, a dispersion plate is provided to uniformly disperse the raw material into the classification space, and the rotating dispersion plate applies centrifugal force to the classification raw material to disperse the raw material horizontally. There is. Such a dispersing machine requires a large amount of energy to drive it, and the tip of the dispersing plate and the inner portion of the casing that collides with the classification material and changes the direction of movement downward are extremely susceptible to wear.

Therefore, frequent repairs are required and the cost is increased due to the use of wear resistant materials.

Furthermore, the dispersion plate in the above-mentioned conventional classification device has a drawback that the dispersion effect is affected when the rotation speed is changed.

[Means for Solving Problems] The classifying device of the present invention is configured such that the classifying space is separated from the rotary shaft as it goes downward, and an aeration overflow distributor is used as a means for supplying powder raw material to the classifying space. It was adopted.

That is, the classifying device of the present invention comprises a frustoconical upper casing provided so as to be constricted at the upper side, an introducing pipe for a classification airflow tangentially connected to a side circumference of the upper casing, and the upper casing. And a plurality of rotating shafts provided in the vertical axis center position, inclined in the upper casing so as to approach the rotating shaft in the upper direction, and arranged at a predetermined interval in the circumferential direction of the rotating shaft. Of the airflow guide vane, and the rotary shaft is supported. The airflow guide vane is inclined toward the center of the airflow guide vane so as to be closer to the rotary shaft, and at a predetermined interval in the circumferential direction of the rotary shaft. A plurality of classifying blades that are arranged, and a distributor that is provided around the upper casing to circulate the classifying material into a classifying space between the classifying blades and the airflow guide blades. Overflow placed facing the space A ventilation member disposed on the outer periphery of the plate and the overflow side plate and below the upper edge of the overflow side plate, and by supplying high pressure air to the lower side of the ventilation member, An aeration overflow distributor for forming a fluidized bed of raw material on the upper side and overflowing the fluidized bed from the upper edge of the overflow side plate to the classification space, and a fine powder discharge connected to the center of the top of the upper casing. It comprises a tube and a lower casing connected to the lower end of the upper casing.

[Operation] In the classifying device of the present invention, the powder raw material charged into the classification space from the air-rate overflow distributor is continuously subjected to centrifugal force by the air flow introduced in the swirling direction and the rotating classification blade to continuously. While undergoing classification, it turns and falls in the classification space. Thus, the classifying blade has a larger radius of gyration as it goes downward, and thus the centrifugal force applied to the particles becomes greater as it goes downward.

Therefore, the tendency that the particle concentration becomes smaller and the classified particle size shifts to the large diameter side as it goes downward in the classification space is offset by the tendency that the centrifugal force becomes larger and the classified particle size shifts to the smaller diameter side as the lower part of the classification space. The classified particle size becomes substantially the same in the vertical direction, and sharp classification can be performed.

In addition, the raw material is supplied to this classification space by an air-rate type overflow distributor so as to be directly charged into the classification space, and since the conventional rotary dispersion plate is unnecessary, the casing and the like are not worn. . Also, the power consumption required for dispersion is small.

If the lower casing is a combination of an outer casing with a lower constriction and an inner casing with an upper constriction, the overall height of the classifying device is small, and the equipment cost is reduced.

[Examples] Examples will be described below with reference to the drawings. FIG. 1 is a side sectional view of an airflow classifying device according to an embodiment, FIG. 2 is a plan view, FIGS. 3 and 4 are plan sectional views taken along lines III-III and IV-IV of FIG. 1, respectively. Is.

Reference numeral 10 denotes a truncated cone-shaped upper casing that is installed so as to be narrowed upward, and a lower casing 12 is connected to the lower end of the upper casing. This lower casing
12 comprises a lower conical frusto-conical outer casing 14 and an upper conical frusto-conical inner casing 16, the inner casing 16 being installed inside the outer casing 14,
The upper and lower levels of both casings 14 and 16 are made substantially equal.

One or a plurality (two in the illustrated embodiment) of airflow introducing pipes 18 are connected to the upper casing 10 in a tangential direction. An airflow guide plate 20 is annularly arranged in the upper casing 10. The airflow guide plate 20 is inclined along the inner peripheral surface of the upper casing 10 so as to approach a later-described rotating shaft 22 as it goes upward, and a plurality of plates are arranged at predetermined intervals in the circumferential direction of the rotating shaft 22. Are arranged. In addition, this airflow guide plate 20
Is supported by the upper casing 10 and is inclined with respect to the radial direction of the upper casing 10 to guide the air flow in the swirling direction.

The upper casing 10 is installed so that the rotary shaft 22 is inserted into the upper casing 10 from above in the vertical axis position. The lower end of the rotary shaft 22 is pivotally supported by the top surface portion of the inner casing 16, and the upper end of the rotary shaft 22 is the upper casing 10.
It penetrates the tube wall of the fine powder discharge tube 24 connected to the central portion of the top surface and is connected to a drive device (not shown).

Horizontal mounting plates 26, 28 are fixed to the upper and lower parts of the upper casing 10 of the rotating shaft 22, and these mounting plates 26,
Classifying blades 30 are installed on the peripheral edge of 28 with both upper and lower ends supported. The lower mounting plate 28 of the mounting plates 26, 28 has a larger diameter than the upper mounting plate 26, and therefore the classification blade 30 is inclined so that the upper end thereof approaches the rotating shaft 22. This classification wing 30
A plurality of plates are installed on the rotating shaft 22 at predetermined intervals in the circumferential direction. The space between the classification blade 30 and the airflow guide plate 20 is a classification space 32.

An air-rate type overflow distributor 34 for supplying the raw material into the classification space 32 is attached to the upper part of the upper casing 10. The air-rate type overflow distributor 34 communicates with the inside of the classification space 32 through an opening 36 formed around the peripheral portion of the top surface of the upper casing 10.

As enlargedly shown in FIG. 5, an overflow side plate 38 is erected around the outer peripheral side of the opening 36, and the overflow side plate 38 is provided upright.
Air slide 40 for introducing powder raw material to the outer peripheral side of 38
Are connected. The air slide introduces the raw material into the air-rate type overflow distributor 34 while partially fluidizing the raw material by the high pressure air blown through the canvas 42. The canvas 42 as a ventilation member is arranged substantially horizontally below the upper edge of the overflow side plate 38, and high-pressure air is introduced to the lower side thereof to form a fluidized bed of the raw material on the upper side thereof. To be done. An equalizer 44 is hung vertically from the canopy portion on the outer peripheral side of the overflow side plate 38.
The powder raw material introduced from (1) is evenly distributed in the air flow type overflow distributor 34 in the entire circumferential direction. Further, reference numeral 46 is a dispersion assisting blade, which is attached to the tip of the attachment plate 26 immediately above the opening 16.

Reference numeral 48 in the figure indicates the classification blade 30 to prevent the classification blade 30 from swinging.
Reference numeral 50 is an air slide connected to the lower part of the lower casing, which is a support plate installed between the two.

The operation of the classification device will be described below.

The classification airflow supplied at a proper speed through the classification air introduction pipe 18 has a spiral shape of the introduction pipe 18 and guide vanes.
With 20, it flows into the classification space 32 with a turning force. On the other hand, the classified raw material passes through the raw material supply air slide 40,
It is thrown into the air-rate type overflow distributor 34. Then, it overflows the overflow side plate 38 and is uniformly introduced into the classification space 32 over the entire circumference. At this time, the powder material is completely dispersed in the air stream by the dispersion assisting blades 46 located right above the classification space 32 and falls into the classification space 32.

In the classification space 32, the classification airflow is flowing while swirling through the guide vanes 20 attached at an angle suitable for the classification flow diameter with respect to the inflow velocity and the amount of passing air. Also,
The classifying blade 30 is rotated at a peripheral speed of the classifying blade 30 at a speed substantially equal to or faster than the circumferential direction of the classifying airflow flowing from the guide blade 20 by driving the rotating shaft 22, and used as a classifying raw material that swirls in the classifying space. A centrifugal force outward in the circumferential direction is applied through the swirling airflow caused by the classifying blade and by direct impact. The raw material falling from the upper part of the classification space 32 is continuously subjected to classification by the classification airflow and the rotating classification blade 30, that is, continuously finely powdered, while reducing the amount itself, in other words, the concentration. Turn and fall while reducing.

Thus, the lower the classification space 32, the farther it is from the rotary shaft 22, the stronger the centrifugal force is. This prevents the classified particle size from migrating to a small size in the upper part of the high density by reducing the centrifugal force effect on the particles of the classifying blade, and the large size of the classified particle size in the lower part of the low density. It is prevented by increasing the centrifugal force effect on the particles of the classification blade.

That is, since the classifying blade 30 has a larger turning radius as it goes downward, the centrifugal force applied to the particles becomes higher as it goes downward. Therefore, the classification space 32
This is offset by the tendency that the particle concentration becomes smaller toward the lower side and the classified particle size shifts toward the large diameter side, and the centrifugal force increases toward the lower side and the classified particle diameter shifts toward the smaller diameter side. As a result, as shown in FIG. 9, the average classified particle size becomes substantially the same in the vertical direction of the classification space 32, and it is possible to achieve sharp classification performance.

The fine powder conveyed to the classification airflow is introduced through a discharge pipe 24 into a cyclone, a bag filter, an electrostatic precipitator or the like and collected. The remaining classification raw material after undergoing classification in the classification space 32, that is, coarse powder, after passing through the classification space 32, falls into the coarse powder collection space 52 composed of the outer casing 14 and the inner casing 16, A transportation air slide that is collected on an annular coarse powder extraction air slide 50 that connects the bottom circumferences of both casings 14 and 16 and that is connected to an appropriate position on this.
It is transported to 54 (see Fig. 4) and unloaded.

The raw material is supplied to the classification space 32 by an air-flow type overflow distributor 34 so as to be directly charged into the classification space 32, and the casing is not required since a conventional rotary dispersion plate is unnecessary. There is also little wear. Also, the power consumption required for dispersion is small.

In the above embodiment, since the lower casing 12 is a combination of the lower constricted outer casing 14 and the upper constricted inner casing 16, the total height of the classification device is reduced,
Equipment costs are reduced. For example, when the connected equipment such as a bucket elevator can be made low, and when the device needs to be housed in the building, the height of the building can be made low and the equipment cost can be reduced.

[Effect] As described above, the classifying device of the present invention can classify the raw material to be classified with sharp classifying performance. Therefore, the pulverizing effect is remarkably improved in the pulverizing system incorporating the classifying device of the present invention.

Further, the classifying device of the present invention consumes less power and reduces the wear of the casing, so that the running cost is also reduced.

[Brief description of drawings]

FIG. 1 is a schematic side sectional view of an airflow classifier showing one embodiment according to the present invention, FIG. 2 is a plan view, and FIGS. 3 and 4 are lines III-III and IV- shown in FIG. FIG. 5 is a plan sectional view taken along line IV, and FIG. 5 is a sectional view of the air-rate type overflow distributor.
FIG. 6 is an explanatory diagram showing the relationship between changes in the partial classification rate curve of the airflow classifier according to the amount of the classified raw material supplied, FIG. 7 is an explanatory diagram showing the relationship between the amount of the classified raw material and the fineness of fine powder, and FIG. Explanatory diagram of the relationship between the amount of classified raw material and the average classified particle diameter in the partial classification curve
FIG. 9 is an explanatory view of the classification action of the present invention, and FIG. 10 is an explanatory view of the classification action of the conventional technique. 10 …… upper casing, 12 …… lower casing, 14 …… outer casing, 16 …… inner casing, 18 …… airflow introducing pipe, 20 …… airflow guide plate, 22 …… rotating shaft, 30 …… classifying blade, 32 …… Classification space, 34 …… Air rate overflow distributor.

Claims (2)

[Claims] 1. A frusto-conical upper casing provided so as to be narrowed upward, an inlet pipe for a classification airflow tangentially connected to a side circumference of the upper casing, and a vertical shaft of the upper casing. A rotary shaft provided at the center position, and a plurality of airflow guides inclined in the upper casing so as to approach the rotary shaft in the upper direction and arranged at a predetermined interval in the circumferential direction of the rotary shaft. The blades are supported by the rotary shaft, are inclined toward the center of the airflow guide blade so as to be closer to the rotary shaft, and are arranged at predetermined intervals in the circumferential direction of the rotary shaft. A distributor provided around a plurality of classifying blades and provided in the upper part of the upper casing so as to introduce the classification raw material into the classifying space between the classifying blades and the airflow guide vanes. Overflow side plate and the overflow A ventilation member is provided on the outer periphery of the side plate and below the upper edge of the overflow side plate, and high-pressure air is supplied to the lower side of the ventilation member so that the raw material flows to the upper side of the ventilation member. An air-rate type overflow distributor that forms a layer and overflows the fluidized bed from the upper edge of the overflow side plate into the pre-classification space; a fine powder discharge pipe connected to the center of the top of the upper casing; A lower casing connected to the lower end of the casing, and a classification device. 2. The lower casing is a frusto-conical outer casing that is connected to the lower end of the upper casing and is constricted downward. Inside the outer casing, upper and lower end levels are the outer casing. The classifying device according to claim 1, further comprising a frustoconical inner casing that is provided so as to be substantially equal and has an upper portion constricted.