JPH06170206A - Spherical granulation method - Google Patents

Abstract

(57) [Summary] [Structure] When forming zirconia powder into spherical particles by the tumbling granulation method, core particles having a diameter of 2 mm or less are formed from the zirconia powder by the stirring granulation method. A granulation method comprising adding zirconia powder to the core particles and growing the core particles to form spherical particles. [Effect] Heavy spheres with high sphericity and the same sphere diameter can be obtained in a short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an efficient method for producing zirconia spheres, which become a ball for grinding by sintering.

[0002]

2. Description of the Related Art In recent years, raw materials in various industrial fields have tended to be finely divided, and a grinding medium used in a grinder for improving the grinding efficiency of the raw materials also tends to have a small particle size. The production of small-diameter spheres with a diameter of 20 mm or less, particularly spheres with a diameter of 10 mm or less, has recently been suitable for continuous mass production at a relatively low cost, and moreover, a rolling granulation method excellent in sphericity, compact density and the like. Is manufactured by. The rolling granulation method using a rotary container is represented by a drum type and a plate type granulator.

[0003] The tumbling granulation method is generally carried out in the same granulating apparatus from the formation of nuclei to spheres having a desired spherical diameter while spraying a binder on a dry powder or a moist powder. There is. In addition, when only fine powder is used as the raw material powder, the efficiency of forming the particles that form the core of the granule becomes low. Therefore, generally, a method in which coarse powder is mixed with the fine powder in the order of several tens% Has been taken.

Generally, the granulation rate is controlled by adjusting the amount of powder and binder added.

[0005]

It is said that the productivity of the rolling granulation method depends statistically on the production rate of core particles.

The tumbling granulation method is carried out by a consistent operation from the raw material powder to the finished pellet, but when the granulating operation is performed using the raw material powder, the addition of the binder causes non-uniform aggregation of the raw material powder. Then, the size and density of the generated nuclear particles may be disturbed. Further, it takes a huge amount of time to grow from the raw material powder into the core particles having a diameter of several mm. Furthermore, it can be said that it is very difficult to deal with such a method in order to obtain a large number of spheres having the same sphere diameter in a short time and with high accuracy.

[0007]

DISCLOSURE OF THE INVENTION The inventors of the present invention formed a nucleus with another granulator in advance, and provided a non-uniform distribution of the nucleus by a two-stage granulation method of supplying this nucleus to a rolling granulator. The present invention has been proposed by discovering that it is possible to shorten the time without causing the occurrence, and that spheres having the same sphere diameter can be obtained almost at the same time.

That is, according to the present invention, when the zirconia powder is formed into spherical particles by the rolling granulation method, the core particles having a diameter of 2 mm or less are formed from the zirconia powder by the stirring granulation method, and the rolling granulation method is performed. The gist of the present invention is to provide a granulation method which comprises adding zirconia powder to the core particles and growing the core particles to form spherical particles. The present invention will be described in more detail below.

The characteristics required for the core particles are that there is no uneven distribution in the shape, and the core itself is not crushed or crushed in the process of being put into a rolling granulator and being granulated and growing. To have strength. From this, it is an important factor in the method of producing the nucleus that rolling and compaction are sufficient and that the nucleus is formed in a short time.

In the present invention, as a method for producing a nucleus, a stirring granulation method which has a high rate of nucleus formation, and has a high rolling and compacting action is adopted.

The granulating machine is not particularly limited, and a general stirring granulating machine equipped with a stirring blade and a crushing blade is applied. Further, the conditions of the granulator are not particularly limited, but since the correlation between the powder and the binder is the most dominant factor in the formation of the nuclei, the raw material powder used and the product in the granular form are It is important to set the obtained stirring speed.

If the water content is too much relative to the raw material powder, the bonding of the core particles will be accelerated and the particles will become coarse. On the other hand, if the water content is too small, the agglomerate will become a porous aggregate with a high porosity. The density will be low. When a stirring blade is rotated to form an agglomerate serving as a core like a normal stirring granulator, it is important to adjust the amount of water in the charged powder. Further, in the case of a device such as a mullerizer that obtains a granulated product having a uniform particle size by supplying the extruded granulated product and performing a cutting action, it is necessary to optimize the water content at the time of forming the extruded product. Is. Normal,
The water content in the zirconia powder used for rolling granulation is 10 to 13 wt% on a wet basis.

The diameter of the core particle should be 2 mm or less, preferably 1 mm or less.

Further, the granulation speed by the tumbling granulator is very low, and the smaller the core particles are, the longer the time required to obtain a finished granule is. Therefore, it is desirable to make the core particles too small. It is important that there is no

When core particles having a diameter of 2 mm or more are formed by an ordinary stirring granulator, the crushing effect by shearing is prioritized over rolling and compaction by a stirring blade, and the self-weight increases as the number of core particles increases. The yield decreases due to the crushing phenomenon caused by the collision of nuclear particles. Also, when using a marumerizer,
It is possible to form core particles with a diameter of 2 mm or more, but the density of the compact in the Marumerizer is lower than the density by the rolling granulation method, so when the diameter grows to 2 mm or more, it is transferred to the rolling granulator and granulated. However, the characteristics of the core particles influence, and the density of the granules of the finished pellet becomes insufficient.

When granulating the core particles using a stirring granulator equipped with stirring blades, the raw material powder is first collected in a container,
Water as a binder is added to the raw material powder with stirring. The addition of water causes the powder to agglomerate and at the same time undergoes a crushing action by a stirring blade to initially form a granule having a small particle size. Subsequently, raw material powder and water are quantitatively added to the fine particles to form desired spheres having a diameter of 2 mm or less.

As a method of controlling the size of the core particles in the method of supplying the extruded granules such as a mulmelizer, a method of supplying the extruded granules adjusted to a desired diameter to a granulator or After the extruded granule having a small diameter is cut with a marumerizer, the raw material powder and water are subsequently added to obtain a sphere by a method having a desired sphere diameter.

The obtained core particles are classified by using a sieve and supplied to the rolling granulator which is the next step. The core particles smaller than the desired particle size are returned to the core particle forming step and recycled.

The core particles obtained here are re-charged into the agitation granulator, and spheroidized and improved in density by rolling in the state as it is or in the state in which a small amount of water is added and a sizing action is added. The nuclear particle characteristics are further improved.

The core particles obtained by the above operation are supplied to the rolling granulator represented by the drum type and the dish type.

The rolling granulation is not particularly limited,
General granulation conditions are applied, and raw material powder and water, which is a binder, are continuously added to the core particles supplied to the tumbling granulator, and granulated into a desired small diameter sphere with a diameter of 20 mm or less. To be done. After that, by drying and sintering at 1400 to 1600 ° C., a crushing ball or the like can be obtained.

[0022]

Before the core particles are fed to the tumbling granulator, the raw material powder is granulated in advance by the agitation granulator, the particles are grown and classified, and the size of the core particles is made uniform so that the own weight becomes uniform. By this operation, the adhering speed of the raw material powder to the core particles, which is the growth mechanism of the rolling granulation, is made uniform, and the granulated pellets having a uniform particle size are efficiently obtained. In addition, since it is possible to obtain heavy core particles having a diameter of 2 mm or less in a short time with a stirring granulator, the production efficiency can be improved.

[0023]

According to the method of the present invention, heavy spheres having a high sphericity and having the same spherical diameter can be obtained in a short time.

[0024]

The present invention is described in detail below with reference to examples, but the present invention is not limited to these.

Example 1 As shown in FIG. 1, an agitating motor made of stainless steel and equipped with an agitating blade of 80 mm and an inner diameter of the lower portion of 85 mm and a height of 1
A simple stirrer composed of a polyethylene container having a diameter of 00 mm was prepared, and 50 g of Toso-Zirconia powder TZ-3YS having a particle diameter of 60 μm was weighed in the container and stirred at a rotation speed of 1000 rpm. While adding water, fine particles were obtained. Subsequently, zirconia powder and water were added to this fine granule at a constant rate under stirring to obtain a spherical granule having a diameter of 2 mm or less within a required time of about 30 minutes. When the spherical granules were classified hierarchically, 1.2 to 1.7 mm
A granulate having a particle size distribution of was obtained in a yield of about 70%.

Next, a diameter of 1.2 mm corresponding to the remaining 30%
The following granules were again charged into the stirring granulator shown in FIG. 1 to grow the spheres, and finally about 500 g of spherical granules were obtained.

The density of the molded product after drying the spherical granules was 3.2 g / m ³ , and the water content when dried at 120 ° C. was about 12 wt%.

300 g of the spherical granulated product having a diameter of 1.2 to 1.7 mm was weighed and placed in a plate type granulator having a pan having a diameter of 600 mm, and the pan was rotated at a constant rotation speed. When the addition amounts of the raw material powder and water were adjusted so that the finished pellets had a diameter of about 15 mm, all the pellets obtained were granules having a diameter of about 15 mm.

The density of the molded product after drying of the granulated sphere pellets was 3.3 g / m ³ , and the average sphericity, which is the ratio of the minimum diameter to the maximum diameter of the pellet, was 1.03.

Example 2 Water was added to the same zirconia powder as in Example 1, and a screw-type extrusion granulator was used to form a somen-shaped granulation having a screen pore size of 0.5 mm in diameter. Got the body 500 g of this granulated material was supplied to a spherical granulator Malmerizer manufactured by Fuji Paudal Co., Ltd., and a cutting operation was performed under high speed rotation. The resulting granulate had a diameter of approximately 0.5 mm. This granulated product was again charged into a marumerizer, and zirconia powder and water were added under high speed rotation to grow to a spherical shape having a diameter of 1 mm. The time required for this operation was about 20 minutes. The spherical granules had a water content of 11 wt% when dried at 120 ° C. and a compact density of 2.6 g /
It was m ³ .

The spherical granules thus obtained were used as core particles and had a diameter of 6
The mixture was put into a dish-type granulator having a pan of 00 mm, and the addition amounts of the raw material powder and water were adjusted so that the diameter of the finished pellet was around 8 mm under a constant rotation speed of the pan.

The green compact density of this finished pellet is 3.2 g.
/ M ³ and the sphericity was 1.02.

Comparative Example 1 Core particles were formed using the same stirring apparatus and conditions as in Example 1 and zirconia powder, and the raw material powder and water were added at a constant rate to grow the core particles.

The growth of nuclei proceeded with the addition of the raw material powder and water until the diameter of the core particles was 2 mm, but when the diameter became 2 mm or more, the crushing and crushing phenomena of the core particles in the growth stage began to occur, and the growth of the particles started. As a result, the crushing phenomenon increased, resulting in a core particle with a broad particle size distribution and poor spherical shape.

Comparative Example 2 Using the zirconia powder used in Example 1, core particles were grown to a spherical shape having a diameter of 2.5 mm by the same apparatus and method as in Example 2. The compact density was 2.5 g / m ³ .

The obtained spherical granules are used as core particles and have a diameter of 6
The mixture was put into a dish-type granulator having a 00 mm pan, and raw material powder and water were added to obtain spheres having a diameter of about 8 mm.

The finished pellets were dried at 120 ° C. and the density of the molded body was measured and found to be 2.9 g / m ³ .

Comparative Example 3 The rotation speed of a plate type granulator having a pan having a diameter of 600 mm was set to be the same as that of Example 1, and the zirconia powder used in Example 1 and water were added to the inside of the pan to perform rolling granulation. The spherical granules were manufactured by the method.

Since the addition amount of the raw material powder and water controls the generation rate, the diameter is 2 mm as the direction of increasing the addition rate.
However, when the addition speed was increased, the granules produced had a wide particle size distribution, and the granules had a high porosity and a low molding density. Therefore, the addition rate was adjusted, the addition conditions excellent in particle size distribution were examined, and the granulation operation was performed, but it took 5 to 6 hours to obtain core particles having a diameter of 2 mm.

[Brief description of drawings]

FIG. 1 shows a stirring granulator used in Example 1.

[Explanation of symbols] Stirring motor Stirring blade Polyethylene container

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Claims (1)

[Claims] 1. When forming zirconia powder into spherical particles by a tumbling granulation method, a core particle having a diameter of 2 mm or less is formed from the zirconia powder by a stirring granulation method, and the core particle is tumbled by a tumbling granulation method. A granulating method, characterized in that the core particles are grown while adding zirconia powder to and granulated into spherical shapes.