JP2811621B2 - Method and apparatus for supplying raw material powder to airflow classifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for supplying raw material powder to an airflow classifier, and more particularly to a method and apparatus for supplying raw material powder to a multi-product airflow classifier utilizing the Coanda effect as an airflow classifier. .

[0002]

2. Description of the Related Art An example of a method for supplying raw material powder to a multi-product airflow classifier utilizing the Coanda effect is disclosed in
There is a so-called ejector dispersion method described in JP-A-44827 and JP-A-63-101858. In the ejector dispersion method, compressed air is supplied to the ejector, and the negative pressure generated at the same time when the supplied compressed air expands, the raw material powder continuously supplied to the ejector from the raw material supply device is dispersed in the airflow. Forming a gas-solid multiphase flow,
It is supplied to the airflow classifier through a raw material blowing pipe.

FIG. 4 is a block diagram of a conventional air flow classifier using an ejector dispersed supply system, and FIG. 5 is a block diagram thereof. The raw material powder 3 stored in the hopper 1 is supplied to an ejector 7 by a raw material supply device 5. Compressed air is supplied from the air compressor 9 to the ejector 7 simultaneously with the supply of the raw material, and the compressed air is supplied into the ejector 7 from the minute opening to expand in the ejector 7. The raw material powder is dispersed in the gas by the action of the negative pressure generated at the time of expansion, and a solid-gas multiphase flow is formed by the raw material powder 3 and the gas. The solid-gas multiphase flow is introduced into the airflow classifier 11 through the raw material blowing pipe 13 that connects the ejector 7 and the airflow classifier 11.

[0004] In the airflow classifier 11, air is sucked in the direction indicated by arrows A, B, and C by the exhaust fan,
As shown by E, outside air is introduced. The raw material powder 3 supplied to the airflow classifier 11 continuously flows by flowing each particle in a different direction based on a difference in inertia force, centrifugal force, fluid resistance, and the like according to the size of each particle. Classified. In the illustrated example, the raw material powder supplied from the ejector 7 is:
The particles flow in the directions indicated by arrows A, B, and C for each particle size and are classified into three types of particle sizes. In other words, particles with large diameters whose inertial force and centrifugal force are larger than the fluid resistance flow and are separated in the direction away from the supply unit. As a result, it descends in a curved line along the Coanda block 15, flows toward the supply section and is classified.

[0005]

The purpose of the airflow classifier 11 is to instantly separate the raw material powder 3 into several products depending on the size of the particles. Ideally it would be supplied in a state. However, when the raw material powder 3 is pulverized, the cohesive force between the particles increases because the surface energy of the particles is large. Further, the fine particles may be aggregated under the influence of humidity, static electricity or the like. Therefore, in the case of the raw material powder 3 containing a large amount of fine particles, it cannot be completely dispersed by the conventional ejector dispersion method, and the fine particles are supplied to the airflow classifier 11 in the form of an aggregate without dispersing part of the fine particles. In particular, fine particles of toner and magnetic material tend to aggregate.

In the airflow classifier 11, the aggregates of fine particles are classified as coarse powder and medium powder, and fine particles that should not be present are mixed in the dispersed product, especially the medium powder and coarse powder product. Classification accuracy is reduced, and in extreme cases, the classified product loses product value.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and eliminates agglomerates of fine particles in a solid-gas mixed-phase flow supplied to an airflow classifier. An object of the present invention is to provide a method and an apparatus for supplying a raw material powder capable of performing high classification.

[0008]

The above object of the present invention is achieved by the following constitution. (1) The raw material powder is crushed and dispersed by a compressed air flow, the dispersed raw material powder is carried on an air flow, and the raw material powder is classified into a plurality of sizes using the Coanda effect. the method of supplying the raw material powder into an air classifier, the
After the raw material powder is dispersed by the compressed air flow, the raw material powder is further disintegrated and secondary dispersed by another compressed air flow, and the raw material powder after the secondary dispersion is supplied to the airflow classifier. A method for supplying raw material powder to an airflow classifier, characterized in that:

(2) The raw material powder is crushed and dispersed by a compressed air flow, and the dispersed raw material powder is carried by an air flow,
In an apparatus for supplying the raw material powder to an airflow classifier that classifies the raw material powder into a plurality of sizes using the Coanda effect, a primary dispersing unit that disintegrates the raw material powder by a compressed air flow and the like Secondary dispersing means for pulverizing the raw material powder by the compressed air flow of the secondary dispersing means so that the raw material powder after the primary dispersion reaches the secondary dispersing means together with the air flow used for the dispersion; The raw material powder supply device, wherein the secondary dispersion means and the air flow classifier are connected so that the raw material powder after dispersion reaches the air flow classifier together with the air flow used for the dispersion.

(3) The method for supplying raw material powder according to (1), wherein the raw material powder is crushed and dispersed by vortex of compressed air during the secondary dispersion. (4) The secondary dispersion means is an air flow crusher having a cylindrical dispersion chamber and a compressed air ejection means for ejecting compressed air into the dispersion chamber to generate a swirl of compressed air. The raw material powder supply device according to the above (2).

A known ejector is used as the primary dispersion means.
Alternatively, an injector can be used, and as the secondary dispersion means, an air current pulverizer can be used, and a combination of the primary dispersion means and the secondary dispersion means is preferable.

Known air flow classifiers utilizing the Coanda effect can be used, and for example, an elbow jet classifier manufactured by Nippon Steel Mining can be used. In addition, as the airflow pulverizer, a known pulverizer can be used. In particular, a pulverizer that forms a vortex and disintegrates it is preferable.

[0013]

The solid-gas mixed phase flow of the raw material powder, which has been crushed by the compressed air flow and is primarily dispersed, and the airflow are led to the secondary dispersion means, and the raw material powder is further crushed by the compressed air flow in the secondary dispersion means. By dispersing the aggregates, even if the disintegration and dispersion by primary dispersion are insufficient and aggregates of fine particles are generated, the aggregates are surely disintegrated and dispersed by secondary dispersion. Therefore, the raw material powder supplied to the airflow classifier does not have agglomerates of fine particles, and the airflow classifier can classify with high accuracy by utilizing the Coanda effect, thereby greatly improving the classification result.

Both primary dispersion and secondary dispersion use compressed air. Particularly in secondary dispersion, compressed air is blown into the dispersion chamber to form a vortex, and the raw material powder is dispersed using the vortex. Is preferred. By utilizing the eddy current, even if the raw material powder contains an aggregate of fine particles, this is entangled in the eddy current and repeatedly crushed and crushed with other particles and aggregates to be satisfactorily disintegrated. It is preferable to use the vortex for secondary dispersion because the efficiency of crushing the aggregates is high. However, a configuration in which the raw material powder is secondary-dispersed simply by blowing compressed air may be used. Aggregates can be broken up.

In particular, according to the present invention, the raw material powder contains a large amount of fine particles and has an average particle diameter (d ₅₀ ) of 8 μm or less, particularly 7 μm to ₅ μm.
The application in the case of classifying m is preferable because the effect is extremely large. The type of the raw material powder supplied according to the present invention is not particularly limited, and any material can be used as long as the aggregation of the fine particles is likely to occur. Preferred examples of the raw material powder supplied according to the present invention include a toner and calcium carbonate, which are liable to cause aggregation of fine particles.

If the number of dispersion stages is further increased to third or higher, the disintegration and dispersion of aggregates are further ensured, but the third or higher dispersion requires an increased amount of compressed air and lowers the raw material concentration. Not a good idea. As the amount of compressed air increases, more power is required, the size of the airflow classifier increases, and the size of the product dust collector and exhaust fan increases, resulting in reduced economic efficiency.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a configuration diagram of a raw material powder supply apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram of a processing step according to the method of the present invention. In FIG. 1, the same components as those in the conventional configuration shown in FIG. 4 are denoted by the same reference numerals.

A raw material powder 3 composed of powders of various particle sizes is contained in a hopper 1. The raw material powder 3 in the hopper 1 is supplied to the ejector 7 by a raw material supplier 5 by a fixed amount, and compressed air is supplied to the ejector 7 by the air compressor 9 at the same time. The compressed air supplied into the ejector 7 is expanded by being ejected from the minute opening, and as a result, a negative pressure is generated near the ejection portion. Then, the raw material powder 3 supplied to the ejector 7 is dispersed by the action of the negative pressure. The dispersion of the raw material powder 3 by the ejector 7 is the primary dispersion. The raw material powder 3 after the primary dispersion is supplied to the dispersion chamber 21 of the airflow crusher 19 through the raw material supply pipe 17, and secondarily dispersed in the dispersion chamber 21.

As shown in FIG. 3, the dispersion chamber 21 of the airflow crusher 19 has a cylindrical shape having a circular horizontal cross section, and at least one of the air chambers on the outer peripheral portion for injecting compressed air in a direction not toward the center. It has a jet nozzle 23. The airflow pulverizer 19 is of a horizontally swirling airflow entrainment type, and jets a supersonic jet airflow from a jet nozzle 23 to form a dispersion chamber 2.
A vortex is created in 1. The airflow from the jet nozzle 23 entrains and disperses the particles after the primary dispersion supplied from above into the dispersion chamber 21 and collides with other particles floating and swirling toward the front.

The agglomerates in the dispersion chamber 21 are moved radially outward by the centrifugal action of the high-speed swirling, and are crushed while repeating collision and friction. Thereby, even if there is an aggregate of fine particles in the raw material powder after the primary dispersion, the aggregate is further broken down by the air current. The fine powder resulting from the crushing of the aggregates has less centrifugal action and is discharged from the raw material draw-out pipe 25 connected to the center of rotation.

The raw material powder 3 discharged from the raw material draw-out pipe 25 has particles of various sizes sufficiently dispersed therein, and in this state, is supplied to the airflow classifier 11 through the raw material blowing pipe 13. The outlet of the tip of the raw material blowing pipe 13 is a slit or a minute opening, and the secondary dispersed raw material powder 3
Is discharged from the outlet into the airflow classifier 11 at high speed.

In the airflow classifier 11, as described above, the raw material powder 3 is supplied while sucking air in the respective directions indicated by arrows A, B, and C, so that the raw material powder 3 is Each time, the fluid flows in the directions indicated by arrows A, B, and C and is classified. Since the coarse powder receives the most centrifugal force during the flow, it flows in the direction of arrow A, the medium flows in the direction B, and the fine powder flows in the direction C.
The classified powder flowing in each direction is collected by a cyclone or a bag filter and collected as a classified product.

[0023]

Next, a description will be given of an embodiment in which the raw material powder is classified by the above-described apparatus. The effect of the raw material dispersion in the airflow classifier appears in the classification accuracy, which can be confirmed by experiments. Hereinafter, a classification in which only primary dispersion is performed by an ejector is referred to as a conventional example, and this is compared with an example of the present invention.

Example 1 As a multi-product air flow classifier utilizing the Coanda effect, an elbow jet classifier EJ-15-3S manufactured by Nippon Steel Mining Co., Ltd. was provided, and a compressed air pipe for secondary dispersion and a raw material extraction pipe were provided. The jet mill JM-20 manufactured by Matsuzaka Trading Co., Ltd.
0 and these were ligated as in FIG. In Table 1, in Conventional Examples 1 and ² , the pressure of the compressed air in the ejector is 6 kg / cm ² , and the air volume is 0.87 Nm ³ / min.
In the embodiment of the present invention, the pressure of the compressed air at the time of primary dispersion in the ejector is 6 kg / cm ² , the air volume is 0.33 Nm ³ / min, and the pressure of the compressed air at the time of secondary dispersion in the airflow pulverizer is 2 kg / cm ^2. And the air volume is 0.52 Nm ³ / min.

The raw material powder is a two-component black toner, whose representative particle size is an average particle size (particle size passing through 50% by volume) d ₅₀ = 5.1.
In μm, the particle size fraction of 3 μm or less was 2.4%, and the particle size fraction of 6 μm or more was 30.0%. In this case, a coulter counter TA-2 manufactured by Coulter Electronics Co., Ltd. (U.S.A.), which is an electric detection band system, was used as a particle size distribution measuring device. Table 1 shows the classification results.

[0026]

[Table 1]

Based on the results shown in Table 1, Example 1 of the present invention is compared with Conventional Example 1. When the representative value of the particle size of the medium powder is about the same (for example, about 4.7 μm), the present invention Example 1
The yield of the middle powder in the product yield is much higher than that of the conventional example 1. From this, it can be seen that according to the present invention, the yield of a medium-sized powder product having a predetermined particle size is much improved.

Next, Embodiment 1 of the present invention and Conventional Example 2 will be compared. The yield of medium powder in the product yield is the same (for example, 56
%), Example 1 of the present invention has a 3 μm
The following fraction and the fraction of 6 μm or more are extremely lower than those of the conventional example 2. From this, it can be seen that according to the present invention, the classification accuracy has been greatly improved compared to the related art. From the above, as described in the present invention, by providing the secondary dispersion means and secondary dispersing the powder, even if agglomerates of the fine powder are generated, they are crushed. Aggregates are not supplied, and high-precision classification can be performed.

Example 2 According to the apparatus configuration and conditions of Example 1, the raw material powder was changed and classified. The raw material powder in Example 2 was ground calcium bicarbonate, and its typical particle size was 36% when the particle size was less than 1 μm.
42% for 1 to 5 μm and 11% for 10 μm or more.
In this case, SKN-500 manufactured by Seishin Co., Ltd., which is a light transmission sedimentation method, was used as the particle size distribution analyzer. The target value of the classification is that the product yield of the medium powder is 20% or more, and the representative value of the particle size of the medium powder is 10% or less for less than 1 μm and 70% for 1 to 5 μm.
Classification was performed by setting 10% or more to 0%. Table 2 shows the classification results.

[0030]

[Table 2]

As is clear from the results shown in Table 2, in the conventional example, the classification target value was not achieved for both the yield of the powder and the representative value of the particle size, but in Example 2 of the present invention, both were achieved. It can be seen that there was a secondary dispersion effect by the secondary dispersion means in the present invention. In Example 2 of the present invention, in particular, the ratio of less than 1 μm in the representative value of the particle size of the medium powder was reduced, and
The proportion of m has increased. This and medium powder 10μm
Since the above ratio was 0% in both the conventional example and the example 2 of the present invention, it is understood that the secondary dispersion effect of the present invention is particularly effective for fine particles.

[0032]

According to the present invention, the raw material powder after the primary dispersion is further secondary-dispersed and then supplied to the airflow classifier, whereby the fine powder aggregates which cannot be completely disintegrated by the primary dispersion are also obtained. Is completely crushed and dispersed by the secondary dispersion, so that the airflow classifier performs reliable classification. In particular, the classification accuracy is improved because the aggregates of fine powders that have been conventionally classified as coarse or medium powders are reduced. Therefore, according to the present invention, the function of the classifier can be sufficiently exhibited with a simple configuration, and high classification accuracy and high yield can be achieved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a raw material supply device and a classifier according to an embodiment of the present invention.

FIG. 2 is a block diagram of a raw material supply device and a classifier according to an embodiment of the present invention.

FIG. 3 is a horizontal sectional view of an airflow pulverizer.

FIG. 4 is a configuration diagram of a conventional raw material supply device and a classifier.

FIG. 5 is a block diagram of a conventional raw material supply device and a classifier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hopper 3 Raw material powder 5 Raw material supply device 7 Ejector 9 Air compressor 11 Air flow classifier 13 Raw material blowing pipe 15 Coanda block 17 Raw material supply pipe 19 Air flow crusher 21 Dispersion chamber 23 Jet nozzle 25 Raw material draw-out pipe

Claims (4)

(57) [Claims] The raw material powder is crushed and dispersed by a compressed air flow, the dispersed raw material powder is carried on an air flow, and the raw material powder is reduced to a plurality of sizes by utilizing the Coanda effect. In the method of supplying the raw material powder to an airflow classifier to be classified , after the raw material powder is dispersed by the compressed air flow, the raw material powder is further crushed by another compressed air flow to be secondary-dispersed. A method for supplying raw material powder to an airflow classifier, wherein the raw material powder after the next dispersion is supplied to the airflow classifier. 2. The raw material powder is crushed and dispersed by a compressed air flow, the dispersed raw material powder is carried on an air flow, and the raw material powder is reduced to a plurality of sizes by utilizing the Coanda effect. In an apparatus for supplying the raw material powder to an airflow classifier to be classified, a primary dispersion means for crushing the raw material powder by a compressed air flow and a secondary dispersion means for crushing the raw material powder by another compressed air flow Are connected in series so that the raw material powder after the primary dispersion reaches the secondary dispersion means together with the airflow used for the dispersion, and the raw material powder after the secondary dispersion is airflow classified together with the airflow used for the dispersion. A raw material powder supply device, wherein the secondary dispersion means and the airflow classifier are connected in order to reach the device. 3. The raw material powder supply method according to claim 1, wherein said raw material powder is crushed and dispersed by vortex of compressed air during said secondary dispersion. 4. The secondary dispersion means is an air flow pulverizer having a cylindrical dispersion chamber and a compressed air ejection means for ejecting compressed air into the dispersion chamber to generate a swirl of compressed air. The raw material powder supply device according to claim 2, wherein: