JPH03154629A - Granulation of spherical particle - Google Patents

Abstract

PURPOSE:To contrive the granulation of spherical and compacted particles by combining two operations, i.e., one step of applying gas pressure to a powdery material in order for the material to be compressed into an aggregate and the other step of granulating the aggregate into spherical particles in a dry condition or in a slightly damp atmosphere by fluid bed. CONSTITUTION:Particles are formed by combining the two operations of granulating procedure, i.e., one step of applying gas pressure to a powdery material in order for the material to be compressed into an aggregate and the other step of granulating the aggregate into spherical particles in a dry condition or in an atmosphere slightly damp or rather vaporous with org. solvent vapor by fluid bed or other means. The aforesaid two steps are repeated alternately. As a result, the spherical and compacted particles ranging in diameter from 0.1 to 1mm can be granulated at a high yield rate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a granulation device that is capable of granulating spherical granules having a minute particle size.

[Prior Art] Conventionally, several granulation methods for obtaining spherical particles are known.

One method is to place raw material powder onto a rotating perforated plate, add a binder, and then roll the powder into granules. According to this granulation method, spherical granules can be obtained, but the particle size is several millimeters to several tens of millimeters, and it is difficult to obtain particles with a particle diameter of several millimeters or less, and it is difficult to control the particle size. Another problem is that the particle size varies. Also, controlling moisture is troublesome.

A spray granulation method is known as another granulation method that produces spherical granules. In this granulation method, raw material powder is dissolved into a liquid, a binder is added thereto, and then the mixture is sprayed. By blowing hot air through this, the liquid in the sprayed material is instantaneously evaporated, and the powder left behind by the evaporation of the sprayed liquid is obtained as spherical granules.

According to this granulation method, spherical particles from several tens of microns to several hundred microns are obtained, but most of them are hollow. In addition, the slurry needs to be adjusted and the equipment is large, making it unsuitable for small-lot, high-mix production.

Various other granulation methods are known, such as fluidized bed granulation and agitation granulation, but it is difficult to obtain spherical particles.

Further, as a method for forming spherical granules, spherical particles can also be obtained by forming cylindrical granules using an extrusion granulator and subjecting the cylindrical granules to a spherical granulator. However, it has the same problems as transfer granulation, such as the inability to obtain granules with minute particle sizes.

[Problems to be Solved by the Invention] As stated above, with any conventional granulation method, spherical granules with a particle size in the range of 0.1 mm to 1 mm cannot be obtained. . Moreover, there are many variations in particle size, and it is relatively difficult to granulate particles with a uniform particle size. Therefore, when trying to obtain particles with uniform particle size,
It had problems such as low yield.

The present invention enables the granulation of spherical particles with a wide range of particle sizes, including the range of 0.1 mm to 1 mm, which could not be obtained by any conventional granulation method, and furthermore, the particle size can vary. The purpose of the present invention is to provide a granulation method with less granulation.

When using raw materials, granules can similarly be formed in the presence of slight moisture or organic solvent vapor (eg alcohol vapor).

Furthermore, the granulation method of the present invention includes 1, for example, in a fluidized bed apparatus, increasing the gas pressure in the apparatus to apply pressure to the raw material and compressing it to form aggregates, and after a predetermined time, reversing the direction of the air flow. In this method, fluidization is carried out to form one spherical granule at the same time in the same device. This method is also convenient when the formation of aggregates by compression and granulation by flow are repeated. That is, in the present invention, it is possible to combine the formation of aggregates by compression and granulation by flow using separate devices, or by changing the direction of air flow in the same device.

The former has the advantage of performing the compression action more effectively, while the latter has the advantage of sharing equipment and shortening the time. is particularly effective.

The gas used in the present invention is preferably an inert gas such as air or nitrogen.

Next, the principle 0 operation of the present invention will be explained in more detail.

First, the principle of the present invention will be explained theoretically.

In the self-sufficient granulation process, granules are formed by repeating agglomeration and dispersion to a particle size with a balance between cohesive energy and dispersion energy.

Here, using Lumbu's equation, it can be expressed as follows.

a=il-c)/π ・K-H/d" In this formula, 0 is the tensile stress of the powder bed randomly filled with equal spherical particles, ε is the porosity, K is the coordination number, and H is the contact average adhesion force at a point,
d is the particle size of the raw material.

Now, as shown in Fig. 1, raw material powder 2 is put into container 1,
If fluidizing air is supplied from the bottom, a fluidized bed is formed as is well known. At this time, if an appropriate fluidized state is maintained, granulation will be carried out in the case of powder with strong adhesive force due to the fluid rolling action.
These granules (agglomerates) remain separated from the powder even after the fluidization state is stopped, and the yield is poor because no adhesive force is exerted. Moreover, the strength of the granulated product is weak and easily crumbles.

By applying counter pressure as shown in Figure 2,
The fluidization condition is stopped and pressure is applied to the agglomerates, compacting them. This also causes the powder to adhere to the aggregates and homogenize them.

In other words, dispersion energy and spheroidization energy are provided by the flow of the powder raw material, and amorphous aggregates are formed by the adhesive force of the raw material itself or, in the case of raw materials without adhesive force, by the adhesive force due to the application of a slight amount of moisture or organic solvent vapor. By applying pressure, cohesive energy is added and a consolidated pile body is obtained. Moreover, it could not be obtained using conventional granulation methods. It is characterized in that granules with a wide range of particle sizes, including those with particle sizes of 0.1 mm to 1 mm, can be obtained in high yield.

Generally, in a fluidized bed granulation method, etc., a binder is used, and aggregates are formed by adhering the powder to the binder on the particle surface. Therefore, the powder does not adhere uniformly in a spherical shape, and therefore only a fluid with an amorphous shape and a low bulk density is obtained.

In the method of the present invention, as described above, the aggregates are formed in a dry state or in an atmosphere containing a small amount of moisture or organic solvent vapor, so that the resulting aggregates are approximately spherical. However, since the formed aggregates are attached mostly by the adhesive force of the raw material powder itself, it is easy to break if left as is.As mentioned above, by applying pressure to the aggregates, it is consolidated and the adhesive strength is significantly increased by 4. The particles are enlarged to form compacted particles while maintaining their spherical shape.

[Example] Next, an outline of an apparatus for carrying out the method of the present invention and an example using this apparatus will be shown.

FIG. 3 is a diagram showing an apparatus for realizing the fluidized compression granulation method of the present invention, which is a conventionally known fluidized bed apparatus provided with a mechanism for applying a counter pressure. In this figure, 1 is a blower for blowing air, 2 is a temperature and humidity controller, 3 is a fluidized bed device, 4 is a switching valve, and 5 is a floor for exhaust ventilation.

In this apparatus, normal fluidization is first performed in the fluidized bed apparatus 3. In this case, if the air flow flows as shown by the solid line arrow and the switching valve 4 is switched to flow the air flow as shown by the broken line arrow, the air from the exhaust blower will flow from above the fluidized bed device 3. is added, pressure is applied in the fluidized bed device 3 by the air flow from the ventilation blower 1, and consolidation and spheroidization are applied to obtain the desired granulated material.

Of course, in order to obtain the desired granules, it may be desirable to repeatedly switch the switching valve 4.

The device described above applies positive pressure by using the exhaust floor for counter pressure, but it may also be a device with a counter pressure blower for negative pressure as shown in Figure 4. In the apparatus shown, air flows as shown by the solid line arrow during flow and as shown by the broken line arrow when under pressure, and granulation similar to that shown in FIG. 3 is possible.

Next, an experimental example using the above apparatus will be shown.

Experiment fl) Experiment (2) Raw material name Ferrite thread mixture Alumina raw material average particle size 0.9μ 0.5μ Granule average particle size 0.35nm O, 55mm Input amount 450g 450g Yield
8o% 90% air amount
B, 27n”/win 0.15m”/sin
Back pressure 0.02g/rs
"0.02Kg/m" reverse pressure cycle time
15sec 15sec back pressure time
1sec 1sec total granulation time
300 m1n 540 m1n or more As the experimental data shows, in experiment (1), the particle size was 0.3
In experiment (2), spherical and compact granules with particle diameters o and 55 nv+, which could not be obtained by conventional granulation methods, were obtained in the range of 0.1 to 1 mm.

[Effects of the Invention] According to the method of the present invention, as shown in Examples, it is possible to granulate spherical and compacted particles with a particle size ranging from 0.1 mm to 1 mm at a high yield. You can.

[Brief explanation of the drawing]

1 and 2 are diagrams showing the principle of the method of the present invention, and FIGS. 3 and 4 are schematic diagrams of an apparatus for carrying out the method of the present invention, respectively. 1...Air blower, 2...Temperature and humidity controller, 3...
Fluidized bed device, 4... switching valve, 5...-exhaust blower,
6...Back pressure blower

Claims (2)

[Claims] (1) An operation of compressing the raw material powder by applying gas pressure to form an aggregate, and a fluidized bed or other method in a dry state or in an atmosphere containing a slight amount of moisture or organic solvent vapor. A spherical granulation method characterized in that granules are formed by individually adding two operations: an operation for forming spherical particles. (2) The spherical granulation method according to claim (1), characterized in that the above two operations are repeated alternately.