JP3109972B2 - Granulation of raw materials for ceramics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a granulating method for granulating raw materials for ceramics.

[0002]

2. Description of the Related Art Granulated materials obtained by granulating powdery ceramic raw materials are used in appropriate fields as raw materials for press molding and as ceramic sands. Various means for granulating such raw materials are available. Granulation method is adopted. As a generally employed granulation method, there is a method in which an organic binder is added to a powder of a ceramic raw material to perform granulation, and a method in which a clay-containing ceramic raw material is spray-granulated by a spray dryer.

[0003]

However, among these granulation methods, the former method requires the use of an organic binder, and requires a degreasing step for removing the organic binder after granulation, which is costly. There is a problem that the granulation time increases with the increase. In the latter method, it is difficult to granulate particles in a certain particle size range stably, and the obtained granules have a small particle diameter and tend to be hollow (bubbles). Therefore, the molded article is liable to cause defects, and when used as a ceramic sand, there is a problem in strength. Therefore, an object of the present invention is to provide a granulation method for producing a granulated body capable of solving these problems.

[0004]

SUMMARY OF THE INVENTION The present invention is a method of granulating a ceramic raw material by using a ceramic raw material by a rolling granulation method, wherein powder is used as the ceramic raw material. It is characterized in that a slurry is supplied to the powder at the time of granulation in a spray state.

In the method for granulating a ceramic raw material according to the present invention, a raw material containing 5% by weight or more of dry clay is used as the ceramic raw material, and the powder of the ceramic raw material is solidified as the slurry. Adopting a slurry, using a slurry having a solid content of 60% by weight to 90% by weight as the slurry, and having an average particle diameter of 4% as the ceramic material.
It is possible to adopt a mode such as employing a powder having a size of 0 μm or less.

[0006]

In the granulation method of the present invention, the powder of the ceramic raw material, which is the granulation raw material, is agglomerated by the moisture given to the powder during granulation to form a granulation nucleus, By tumbling granulation, this granulation nucleus rolls and attaches powder to the outer periphery of the nucleus to increase the diameter. Granules having a particle size can be obtained by separation. In such a granulation method, the granules gradually grow from small granulation nuclei and have a predetermined particle size, so that the inside is dense, there are few bubbles, and high compressive strength is obtained. In particular, when clay is included in the raw material, a material having higher compressive strength can be obtained due to the adhesive action of the clay.

In such a granulation method, when water is supplied to the powder in a granulated state during granulation, the granules have no bubbles and a relatively high compressive strength per unit particle size. Has an irregular shape whose shape is not determined without forming a spherical shape. For this reason, there is a major problem in use as a raw material for ceramics. Also, when supplying water to the powder in a spray state at the time of granulation, it becomes a granule having a nearly spherical form, and when a powder having an average particle diameter of 10 μm or less is used as the powder. The resulting granules have extremely small bubbles and a high compression load per unit particle diameter. However, when a powder having an average particle diameter of 10 μm or more is used as the powder, large bubbles gradually increase in the granulated body in proportion to the particle diameter of the powder.

On the other hand, when water is supplied to the powder in a slurry state during granulation as in the granulation method of the present invention, the powder is agglomerated by the water and solids in the slurry. A grain nucleus is formed, and by rolling granulation, the granule nucleus is rolled and powder is adhered to the outer periphery thereof through a slurry to increase the diameter. Therefore, a relatively large powder having an average particle diameter of 10 μm or more is employed because the amount of water trapped in the granule during granulation is small, and the water is not locally ubiquitously trapped. However, granules having a spherical shape with almost no air bubbles and high compressive strength can be obtained.

In the granulation method of the present invention, a slurry having a solid content of a powder of a ceramic raw material is employed as the slurry, and a slurry having a solid content of 60% to 90% by weight is employed as the slurry. If a powder having an average particle diameter of 40 μm or less is used as a raw material for ceramics, a granule having a large particle diameter of 1000 to 3000 μm, which has almost no bubbles and high compressive strength, can be obtained.

[0010]

【Example】

(Preparation of Granulation Powder and Slurry as Granulation Raw Materials) As the granulation powder, pulverized clay, silica sand, feldspar, alumina and the like are mixed and crushed to prepare a powder. The mixing amount of the clay is preferably 5 to 30% by weight, and as the pulverizing means and mixing means, appropriate pulverizing means and mixing means such as wet pulverization, dry pulverization and the like, and wet mixing and dry mixing can be employed. When wet pulverization or wet mixing is employed, a drying step is required. The particle size of the powder as the granulation raw material is 1 μm
Particles having respective particle diameters in the range of ５００500 μm were prepared. Further, in preparing the slurry, powder used as a granulation raw material was employed as a solid content, and a slurry having a solid content of 10 to 90% by weight was prepared.

(Granulation means) In the rolling granulation method, a fine granulation apparatus shown in FIG. 1 is employed. The granulator is based on a fine granulator GRC (fine granulator manufactured by Shinto Kogyo Co., Ltd.), and is configured by adding a spray mechanism to the granulator. FIG. 1 schematically shows the granulation apparatus, and FIG. 2 schematically shows the principle of the granulation apparatus. The granulation apparatus includes a conical drum 11 and a granulation powder A as a granulation raw material.
A conical drum 11 is driven by a motor 16, comprising a first vibrating feeder 12 for supplying the water, a spraying mechanism 13, a second vibrating feeder 14 for discharging the granules B, and a far-infrared heater 15. . Also, the conical drum 11
The inside is divided into granulation zone and sizing zone,
The powder A for granulation is supplied to the inside of the conical drum 11 from the small-diameter port 11a side via the first vibrating feeder 12 in a fixed amount, and the powder A for granulation in the conical drum 11 is supplied from the spray mechanism 13 to the inside. A constant amount of water is supplied in a dripped state or a spray state or a slurry is sprayed, and in this state, the conical drum 11 rotates, so that the granulating powder A forms granulation nuclei in the conical drum 11. The granulation powder A gradually adheres to the outer periphery of the granulation nucleus to increase the particle size.

In the conical drum 11, large-diameter granules are formed by the segregation action of the conical drum 11.
And the small-diameter granules flow toward the small-diameter port 11a side of the conical drum 11, during which the fine particles continuously roll and become spherical, and are pushed out to the large-diameter side 11b side. It is continuously discharged through the outlet 14. During this discharge, the moisture of the granulated body B is adjusted by the far-infrared heater 15 on the second vibrating feeder 14.

In FIG. 2, the trajectory of the granulated material B in the rotating conical drum 11 is indicated by an arrow, and the difference in centrifugal force between the large-diameter 11b side and the small-diameter 11a side of the conical drum 11 and the granulation are shown. Of the conical drum 1
The layer surface of the powder A in which the granulated material in 1 flows from the large-diameter side 11b to the small-diameter side 11a is formed. The granules B are repeatedly rolled in the direction of the arrow through the inside of the layer of the powder A for granulation. The large granules B are returned to the large diameter 11b side by centrifugal force without being caught in the layer of the granulation powder A, and finally discharged from the large diameter 11b side.

(Granulation Experiment 1) In this experiment, the relationship between the difference in water supply in the granulation step and the characteristics of the prepared granules was examined. In this experiment, a powder having an average particle diameter of 15 μm comprising silica sand containing 10% by weight of dry clay (clay drying temperature: 180 ° C.), feldspar and alumina was used as the powder for granulation. As the granulating device, the fine granulating device shown in FIG. 1 is employed, and as the water supply means in the granulating step, means for spraying a slurry having a solid content concentration of 75% by weight using the spray mechanism 13 ( Slurry spraying method) was employed, and the water supply to the powder was set to 10 wt% on the outside. The obtained granules were fired at 1250 ° C. Further, as a comparative example, powder was granulated by the same means as described above except that a water dropping method and a water spraying method were employed as a water supply means, and the obtained granules were fired at 1250 ° C. In each of the fired granules (A), (B), and (C) obtained by the slurry spraying method, the water dropping method, and the water spraying method, the particle diameter is 2000 μm.
The compressive strength was measured by selecting one having a range of m ± 100 μm, and the cross-sectional shape of the granulated product was observed with a microscope.
FIG. 3 shows a cross-sectional shape of each granule using a microscope. Also,
The compressive strength (kg / cm ² ) of each granule is 33.4
(A), 19.4 (B) and 12.1 (C).

Referring to the results of this experiment, the granules (A) formed by using the slurry spraying method are almost spherical, and the presence of air bubbles is hardly confirmed. On the other hand, the granules (B) formed by using the water dropping method have almost no presence of air bubbles, but have a non-spherical shape and an atypical shape. The granules (C) thus formed are almost spherical, but the presence of large bubbles is confirmed. On the other hand, these granules (A),
The compressive strengths of (B) and (C) are in the order of (A)>(B)> (C). Therefore, when these results are combined, it is understood that the granules formed by using the slurry spraying method have the best properties.

(Granulation Experiment 2) In this experiment, in the granulation method in which the powder is granulated by using the slurry spraying method, the solid concentration of the slurry to be used and the compression of the obtained granules after sintering. The relationship with strength was examined. In this experiment, a powder having an average particle diameter of 15 μm comprising silica sand containing 10% by weight of dry clay (clay drying temperature: 180 ° C.), feldspar and alumina was used as the powder for granulation. As the granulating apparatus, the fine granulating apparatus shown in FIG. 1 is employed, and the slurry has a solid content of 0% by weight or less.
Slurries of various solids concentrations in the range of 90% by weight were employed.
The obtained granules were fired at 1250 ° C. and the compressive strength was measured. The results obtained are shown in the graph of FIG.

Referring to the graph, the compressive strength of the granulated body after calcination is almost constant and low in a slurry having a solid concentration of 0% by weight to 30% by weight, while the solid content is 0% to 30% by weight. When the concentration exceeds 30% by weight, the concentration gradually increases, and when the solid concentration exceeds 50% by weight, the concentration sharply increases and the solid concentration becomes 80%.
It reaches a maximum near the weight%, and then drops sharply. From these results, when the solid content concentration of the slurry was evaluated from the viewpoint of the compressive strength of the granulated product, the solid content concentration was 6% in the tumbling granulation of the powder.
It is preferred to employ a slurry in the range of 0% to 90% by weight.

(Granulation Experiment 3) In this experiment, in the granulation method of granulating the powder by using the slurry spraying method, the particle diameter of the granulation powder to be adopted and the calcination of the obtained granulated body The relationship with the subsequent porosity was examined. In this experiment, the average particle diameter of silica powder containing 10% by weight of dry clay (clay drying temperature: 180 ° C.), feldspar and alumina was 200 μm as the powder for granulation.
Powders of each average particle size up to were used. Further, a fine granulation apparatus shown in FIG. 1 was employed as a granulation apparatus, and a slurry having a solid content of 70% by weight was employed as a slurry. The obtained granules were fired at 1250 ° C., and the cross-sectional shape was observed with a microscope, and the porosity of each granule was measured by the Archimedes method (boiling method). The results obtained are shown in the graph of FIG.

Referring to the graph, the porosity of the granules after firing is very small when the granulation powder has a very small particle size of 10 μm or less, but the porosity is 10 μm.
When the particle size exceeds 40 μm, the porosity gradually increases, and when the particle size exceeds 40 μm, the porosity sharply increases. From these results, if the particle diameter of the granulation powder is evaluated from the viewpoint of the porosity of the granulated body, it is preferable to employ a powder having an average particle diameter of 40 μm or less as the granulation powder. . If the slurry spraying method is adopted as the granulation method as in this experiment, the average particle diameter is 10 μm.
Not only powder with a small particle size of 10 μm
Even if a powder having a relatively large particle diameter of up to 40 μm is employed, a granule having a small porosity and therefore a high compressive strength can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a fine granulation apparatus for performing a granulation method of the present invention.

FIG. 2 is an explanatory diagram showing a granulation principle in the granulation apparatus.

FIG. 3 is a schematic cross-sectional view of a granule obtained by using a means for supplying water having different contents, which is observed with a microscope after firing.

FIG. 4 is a graph showing the relationship between the solid content concentration of the employed slurry and the compressive strength of the obtained granules after firing when the slurry spraying method is employed.

FIG. 5 is a graph showing the relationship between the particle size of the granulating powder to be employed and the porosity of the obtained granulated body after firing when the slurry spraying method is employed.

[Explanation of symbols]

11: conical drum, 12: first vibratory feeder, 13: spray mechanism, 14: second vibratory feeder, 15: far-infrared heater, 16: drive motor, A: fired structure obtained by adopting the slurry spray method Granules, B: Granules after firing obtained by employing the water dropping method, C: Granules after firing obtained by employing the water spraying method.

Claims (5)

(57) [Claims] The present invention relates to a method of granulating a ceramic raw material using a raw material for ceramic by a rolling granulation method, wherein a powder is employed as the raw material for ceramic and a slurry is added to the powder during granulation. A method for granulating raw materials for ceramics, characterized in that the raw material is supplied in a spray state. 2. A method for granulating a ceramic raw material according to claim 1, wherein said ceramic raw material contains 5% by weight or more of dry clay. 3. The method for granulating a ceramic raw material according to claim 1, wherein a slurry containing a solid content of the ceramic raw material powder is used as the slurry. Granulation method. 4. The method for granulating a raw material for ceramics according to claim 1, wherein the slurry has a solid content of 60% by weight to 90% by weight. Granulation method of raw materials for use. 5. The method for granulating a ceramic raw material according to claim 1, wherein the ceramic raw material comprises:
A method for granulating a raw material for ceramics, wherein a powder having an average particle diameter of 40 μm or less is employed.