JP2000086348A - Ceramics compact and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a dense ceramics compact consisting essentially of a coal ash, especially a fly ash which is an industrial waste by sintering a coal ash and an inorganic sintering material and imparting a specific bulk density, a specified percentage of water absorption, a specific pore volume and a specified specific surface to the ceramics compact. SOLUTION: This ceramics compact has 1.0-2.0 g/cm3 bulk density, 0.01-0.8 vol.% percentage of water absorption, 0.01-0.2 cc/g pore volume and 0.1-0.4 m2/g specific surface area. The average particle diameter of a coal ash (e.g. a fly ash) used for producing the compact is 10-40 μm and the mixing ratio of the coal ash is 60-90 wt.% based on the dry weight. The melting temperature of an inorganic sintering material (e.g. feldspar) is 1,050-1 250 deg.C and the average particle diameter thereof is 0.2-15 μm. The mixing ratio of the inorganic sintering material is 10-40 wt.% based on the dry weight. When the viscosity of the mixture of the coal ash with the inorganic sintering material is low, an inorganic thickening material (e.g. kaolin) may be used. The mixing ratio thereof is 0-25 wt.% based on the dry weight. The amount of water used is 25-40 pts.wt. based on 100 pts.wt. of the total weight of the coal ash, inorganic sintering material, etc. The heat-treating temperature is 1,000-1,300 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic molded product mainly composed of coal ash, especially fly ash (fly ash), and a method for producing the same.

[0002]

BACKGROUND OF THE INVENTION Fly ash is a fine by-product of the combustion of coal, especially bituminous coal in powder form. Generally, fly ash is produced in very large quantities from coal-fired power plants. Conventionally, these fly ash are mostly disposed of by land treatment such as landfill, and only a part of them is effectively used in the form of aggregate for concrete.

[0003] In recent years, proposals have been made to use fly ash effectively. For example, JP-A-52-78687 and JP-A-55-78687.
Japanese Patent Application Publication No. 134640 proposes a production method in which bentonite, which is a binder, is mixed with fly ash in a considerable amount and water-mixed is sintered to obtain a heavy metal trapping material.

Japanese Patent Application Laid-Open No. 9-156998 discloses a technique relating to a ceramic molded body obtained by molding and sintering fine particles of coal ash. However, this technology
The present invention relates to a porous ceramic molded body having a very high water absorption of 10 to 50% by volume, which is manufactured using a very small particle diameter of 1 to 10 μm as a raw material coal ash. Such a ceramic molded body has a problem that its use is limited because it is porous and has low strength.

According to a study by the present inventors, coal used in recent years contains many foreign coals, and fly ash generated from a plant using such foreign coals has a large particle diameter. In order to adopt the above method, a process such as pulverization is required, so that there are problems that the process becomes complicated and the cost increases.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a dense ceramic molded body mainly composed of coal ash, especially fly ash, and a method for producing the same.

[0007]

According to the present invention, a bulk density obtained by sintering coal ash and an inorganic sintered material is 1.0 to 2.0 g / c.
m ³ , water absorption 0.01 to 0.8 volume%, pore volume 0.01 to 0.2 cc / g, specific surface area 0.1 to 0.4
m ² / g.

In the present invention, the average particle diameter is 10 to 40 μm.
60 to 90% by weight of coal ash in dry weight, melting temperature 10
An inorganic sintered material having an average particle size of 0.2 to 15 μm at 50 to 1250 ° C. has a dry weight of 10 to 40% by weight, and an inorganic thickener has a dry weight of 0 to 25% by weight (coal ash, inorganic sintered material and A mixture obtained by mixing the dry weight of the inorganic thickener with 100% by weight) and water is kneaded and extruded while at least temporarily deaerated, dried, and dried.
This is a method for producing the ceramic molded body, which is heat-treated at 00 to 1300 ° C.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION
The bulk density is 1.0 to 2.0 g / cm ³ and the water absorption is 0.01
0.8% by volume, pore volume of 0.01 to 0.2 cc /
g, the specific surface area is 0.1 to 0.4 m ² / g, the preferred bulk density is 1.1 to 1.85 g / cm ³ , the preferred water absorption is 0.02 to 0.75% by volume, and the preferred fineness. The pore volume is 0.02 to 0.18 cc / g, and the preferred specific surface area is 0.1 to 0.8 cc / g.
15 to 0.35 m ² / g. In the present invention,
The bulk density is JIS R 2205 and the water absorption is JIS R 22
05, the pore volume is measured by the mercury intrusion method, and the specific surface area is measured by the BET method.

[0010] The shape of the ceramic molded body of the present invention is not particularly limited, but is preferably a plate, a column, a cylinder, a prism, a prism, a honeycomb, a star, a clover shape, a block, or a sphere. .

The ceramic compact of the present invention is obtained by sintering coal ash and an inorganic sintered material. In order to obtain a ceramic molded body having desired physical properties, the particle diameters of the raw coal ash and the inorganic sintered material are appropriately selected.

The ceramic molded article of the present invention can be used for building materials such as exterior wall tiles, exterior wall tile blocks, floor tiles, floor tile blocks, wall materials, lightweight aggregates, fire and heat resistant building materials, heat insulation materials, and the like. Construction materials such as lightweight aggregates, roadbed materials, fine aggregates, garden paving stones, residential land development rainwater infiltration layer materials, park ground maintenance work infiltration structural materials, road and subgrade embankment materials,
Gardening materials such as tree planting, artificial ground planting, slope vegetation spraying and horticultural soil, tiles, tile-blocks, etc.
It can be used as an irregular filling material such as a magnetic Raschig ring.

Hereinafter, the method for producing a ceramic molded body of the present invention will be described.

In the method for producing a ceramic molded body of the present invention, first, coal ash, an inorganic sintered material, optionally an inorganic thickener and an appropriate amount of water are mixed to obtain a mixture.

The coal ash used in the method for producing a ceramic molded article of the present invention has an average particle diameter of 10 to 40 μm, preferably 13 to 35 μm. Examples of such coal ash include fly ash and bottom ash generated from a coal combustion power plant or the like, with fly ash being particularly preferred. The mixing ratio of coal ash is 60 to 90% by weight on a dry weight basis.

In the present invention, the average particle diameter is a particle diameter corresponding to a cumulative volume of 50% in a volume-based cumulative distribution curve obtained by a laser diffraction type particle size distribution measuring method. In the present invention, the term “% by weight” indicating the mixing ratio means that the total of the dry weights of coal ash, inorganic sintered material and inorganic thickener is 100%.
% By weight means% by weight.

The inorganic sintered material used in the method for producing a ceramic molded body of the present invention has a melting temperature of 1050 to 1250 ° C.
belongs to. As such an inorganic sintered material, coal ash, particularly fly ash has a melting temperature of 1100 to 1200.
Feldspar (melting temperature around 1150 ° C), which is relatively close to ° C and has a large effect of filling the voids, is preferable.

The average particle diameter of the inorganic sintered material is 0.2
To 15 μm, preferably 0.5 to 5 μm. Since the inorganic sintered material has a role of filling the voids between the coal ash particles by melting and sintering, the selection of the average particle size of the inorganic sintered material is important.

Since the coal ash particles are mutually bonded and densified by using such an inorganic sintered material, the bulk density of the obtained ceramic molded body is increased, and the water absorption,
The pore volume and specific surface area are reduced.

The mixing ratio of the inorganic sintered material is 10% by dry weight.
４０40% by weight. In order to obtain a denser ceramic molded body, it is preferable to add a large amount of the inorganic sintered material, and in order to reduce shrinkage of the ceramic molded body after the heat treatment due to melting and sintering of the inorganic sintered material, an inorganic material is used. It is preferable that the proportion of the sintered material added is small.

When the viscosity of the mixture is small using only coal ash and the inorganic sintered material, in order to increase the viscosity and enhance the moldability by extrusion molding, the inorganic sintering material is used in addition to the coal ash and the inorganic sintered material. A sticky material may be used. Examples of such an inorganic thickener include kaolin, bentonite, diatomaceous earth, talc, activated clay, and the like. Bentonite, which has a high viscosity and is inexpensive, is particularly preferable. The mixing ratio of the inorganic thickener is 0 to 25% by weight on a dry weight basis, and preferably 1 to 25% by weight. It is preferable that the mixing ratio of the inorganic thickener is large in order to increase the viscosity so as to facilitate molding, and the addition ratio of the inorganic thickening material is small in order to minimize the adhesion between the molded bodies after molding. Is preferred.

The amount of water used varies depending on factors such as the type of coal ash, inorganic sintering material and inorganic thickener,
Usually, it is 25 to 40 parts by weight based on 100 parts by weight of the total weight of the coal ash, the inorganic sintered material and the inorganic thickener. It is preferable that the amount of water is large in order to lower the viscosity so that molding is easy, and the amount of water is small in order to enhance the shape retention after molding and to minimize the adhesion between molded bodies. Is preferred.

In addition to the above, water-soluble thickeners such as methylcellulose and hydroxymethylcellulose, inorganic fibers such as glass fibers and ceramic fibers, and pore-forming materials such as ammonium nitrate and ammonium carbonate may be added to the mixture. .

In the present invention, in the step of kneading and extruding the mixture, the inside of the kneading device or the extruding device containing the mixture is at least temporarily degassed in order to obtain a dense compact. The pressure at the time of deaeration is preferably 0.1 kPa (absolute pressure, hereinafter abbreviated) or more so that the capacity of a deaeration pump or the like is not unnecessarily increased and a predetermined pressure reduction condition is reached in a short time. In order to further reduce the shrinkage of the ceramic molded body due to the heat treatment by reducing the voids between the particles to obtain a dense ceramic molding precursor, the pressure is preferably set to 100 kPa or less.

The apparatus used for kneading is not particularly limited.
For example, a batch-type kneader using a double-armed stirring blade, a continuous kneader such as a shaft reciprocating type or a self-cleaning type can be used, but the kneading is performed while checking the state of the kneaded product. The batch type is preferable in that kneading can be performed.

The apparatus used for extrusion molding is not particularly limited, and examples thereof include an auger type extruder and a piston type extruder. The extruded product is appropriately cut into a suitable length.

The ceramic molding precursor thus obtained has a dense structure in which components such as coal ash, inorganic sintering material and water are uniformly dispersed and has a dense structure. The shrinkage of the body is small, and the mechanical strength of the sintered ceramic body after sintering is improved. Further, from such a ceramic molding precursor, there is also an effect that a homogeneous ceramic molded body can be obtained with good reproducibility.

The ceramic molding precursor is then dried to obtain a dried ceramic molding precursor. The drying method is not particularly limited, for example, generally known hot air drying method, natural drying method, humidity drying method and the like, but it is possible to make the drying speed of the outer surface and the inner surface of the ceramic molding precursor close. Therefore, the natural drying method and the humidity drying method are preferred.

Next, the dried body of the ceramic forming precursor is heat-treated, and the coal ash and the inorganic sintered material are sintered to obtain a ceramic formed body. Heat treatment temperature is usually 1000-1
The temperature is 300 ° C, preferably 1120 to 1250 ° C. In order to obtain a denser ceramic molded body having excellent mechanical strength, it is preferable to reduce the rate of temperature rise to the heat treatment temperature, and the rate of temperature rise is usually 400 ° C./h or less, preferably 100 to 100 ° C./h. 350 ° C./h. Since the heat treatment time varies depending on the heat treatment temperature and the mixing ratio of the coal ash, it cannot be specified unconditionally, but is usually 0.5 to 5 hours.

[0030]

Example 1 80 parts by weight of spherical fly ash having an average particle diameter of 31 μm and 20 parts by weight of feldspar having an average particle diameter of 6 μm were mixed by a double-arm kneader until uniform, and then 32 parts by weight of water was added. Was added and kneaded until it became clay-like (material A). The obtained kneaded product was 10 mm thick with a clay kneading type vacuum extruder under a reduced pressure condition of 35 kPa.
Extruded to a width of 95 mm, cut to a length of 45 mm,
A ceramic molding precursor was obtained. This was dried in the shade for one day, and the temperature was raised from room temperature to 1200 ° C. at 300 ° C./h.
Heat treatment was performed at 200 ° C. for 2 hours. The obtained ceramic compact had a bulk density of 1.39 g / cm ³ and a water absorption of 0.0.
9 volume%, pore volume 0.09 cc / g, specific surface area 0.1
It was 8 m ² / g, and a ceramic molded body having excellent mechanical strength was obtained. When the morphology of the formed ceramic article was observed with a scanning electron microscope, it was confirmed that fly ash particles were bonded to each other, and that most of the voids between the particles were occupied by feldspar and were dense. This ceramic molded article could be used as a building material such as a lightweight aggregate, a fire- and heat-resistant building material and a heat insulating material.

Comparative Example 1 Extrusion molding, cutting and drying were performed in the same manner as in Example 1 except that the material A was not subjected to vacuum degassing using a clay-type vacuum extruder. And heat treatment was performed to obtain a ceramic molded body. The obtained ceramic molded body has a bulk density of 1.09 g / c.
m ³ , water absorption 0.95% by volume, pore volume 0.27c
c / g and the specific surface area were 0.43 m ² / g, but the mechanical strength was poor, and it was partially broken by a slight impact.

Comparative Example 2 A ceramic molded body was manufactured in the same manner as in Example 1 except that coal ash obtained by grinding bottom ash and having an average particle diameter of 88 μm was used as coal ash. The obtained ceramic molded body had a bulk density of 1.18 g / cm ³ , a water absorption of 1.29% by volume, a pore volume of 0.31 cc / g, and a specific surface area of 0.31 m ² / g, but had a mechanical strength. Was inferior and was partially damaged by a slight impact.

Comparative Example 3 In Example 1, 95 parts by weight of fly ash and 5 parts by weight of feldspar were mixed in a double-arm kneader until uniform, and then 35 parts by weight of water were added to form a clay. Extrusion molding was carried out in the same manner as in Example 1 except that the mixture was kneaded to the extent that the viscosity and shape retention were poor, and handling after molding was caused by adhesion between the ceramic forming precursors and deformation of the ceramic forming precursors. It was impossible.

Comparative Example 4 A ceramic molded body was manufactured in the same manner as in Example 1, except that the heat treatment temperature was changed to 950 ° C. The obtained ceramic molded body had a bulk density of 0.92 g / cm ³ , a water absorption of 2.6% by volume, a pore volume of 0.49 cc / g, and a specific surface area of 0.54 m ^2.
/ G. Further, the ceramic molded body was not magnetically advanced, and had a low mechanical strength such that it was partially damaged by a slight impact.

Comparative Example 5 A ceramic molded body was manufactured in the same manner as in Example 1 except that the heat treatment temperature was changed to 1350 ° C. However, not only did the ceramic molded body melt during the heat treatment, and the shape was not maintained, but also the adjacent ceramic molded bodies were fused and fixed.

Example 2 71 parts by weight of spherical fly ash having an average particle diameter of 26 μm and 29 parts by weight of feldspars having an average particle diameter of 6 μm were mixed by a double-arm kneader until uniform, and then 37 parts by weight of water was used. The mixture was added and kneaded until it became clay-like. The obtained kneaded product was 18 mm in outer diameter and 12 m in inner diameter by a clay kneading vacuum extrusion molding machine under a reduced pressure condition of 10 kPa.
m and extruded to a length of 18 mm to obtain a Raschig-shaped ceramic molding precursor. This is dried in the shade for one day, and 300 ° C./h from room temperature to 1220 ° C.
And heat-treated at 1220 ° C. for 2 hours. The obtained ceramic molded body has a bulk density of 1.16 g / cm ³ , a water absorption of 0.05 volume%, a pore volume of 0.07 cc / g, and a specific surface area of 0.16 m ² / g, and has excellent mechanical strength. A ceramic molded body was obtained. When the morphology of the formed ceramic article was observed with a scanning electron microscope, it was confirmed that fly ash particles were bonded to each other, and that most of the voids between the particles were occupied by feldspar and were dense. This ceramic molded body could be used as a magnetic Raschig ring for irregular packing or the like.

Example 3 86 parts by weight of spherical fly ash having an average particle diameter of 29 μm and 14 parts by weight of feldspars having an average particle diameter of 3 μm were mixed by a double-arm kneader until uniform, and then 40 parts by weight of water. The mixture was added and kneaded until it became clay-like. The obtained kneaded product was extruded to an outer diameter of 1.5 mm with a clay kneading vacuum extruder under a reduced pressure of 60 kPa, and cut into a length of 2 mm to obtain a cylindrical ceramic molding precursor. . This was dried in the shade for one day, heated from room temperature to 1185 ° C. at 300 ° C./h, and heat-treated at 1185 ° C. for 2 hours. The obtained molded body has a bulk density of 1.44.
g / cm ³ , water absorption 0.17% by volume, pore volume 0.16
cc / g, the specific surface area was 0.34 m ² / g, and a ceramic molded body having excellent mechanical strength was obtained. When the morphology of the formed ceramic article was observed with a scanning electron microscope, it was confirmed that fly ash particles were bonded to each other, and that most of the voids between the particles were occupied by feldspar and were dense. This ceramic molded body is used for garden paving stones, materials for rainwater infiltration layer in residential land development, infiltration structural materials for park ground maintenance work, construction materials for road and subgrade embankment materials, and for tree planting, artificial ground planting, and slopes. It could be used as a horticultural material or the like including vegetation spraying and horticultural soil.

Example 4 78 parts by weight of spherical fly ash having an average particle diameter of 33 μm, feldspar 1 having an average particle diameter of 8 μm
3 parts by weight and 9 parts by weight of bentonite were mixed by a double-arm kneader until uniform, then 35 parts by weight of water was added and kneaded until it became clay-like. 7
Under a reduced pressure condition of kPa, the extruder was extruded to an outer diameter of 3 mm by a clay-type vacuum extruder, cut into a length of 3 mm, and then formed into a spherical ceramic precursor having a diameter of about 3 mm by a rolling granulator. I got This was dried in the shade for one day, heated from room temperature to 1185 ° C. at 300 ° C./h, and heat-treated at 1185 ° C. for 2 hours. The obtained molded body has a bulk density of 1.42.
g / cm ³ , water absorption 0.04% by volume, pore volume 0.06
cc / g, the specific surface area was 0.22 m ² / g, and a ceramic molded body having excellent mechanical strength was obtained. When the morphology of the formed ceramic article was observed with a scanning electron microscope, it was confirmed that fly ash particles were bonded to each other, and that most of the voids between the particles were occupied by feldspar and were dense. This ceramic molded body is used for garden paving stones, materials for rainwater infiltration layer in residential land development, infiltration structural materials for park ground maintenance work, construction materials for road and subgrade embankment materials, and for tree planting, artificial ground planting, and slopes. It could be used as a horticultural material or the like including vegetation spraying and horticultural soil.

[0039]

According to the present invention, it is possible to produce a dense ceramic compact mainly containing coal ash, particularly fly ash, which is industrial waste. The ceramic molded article produced by the method of the present invention can be used for a wide range of applications such as construction materials, construction materials, horticultural materials, and randomly filled materials.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 35/64 C04B 35/14 35/64 L

Claims (2)

[Claims] A bulk density obtained by sintering coal ash and an inorganic sintered material is 1.0 to 2.0 g / cm ³ , and a water absorption is 0.01 to 2.0 g / cm ³ .
0.8 volume%, pore volume of 0.01 to 0.2 cc / g,
A ceramic molded body having a specific surface area of 0.1 to 0.4 m ² / g. 2. Coal ash having an average particle size of 10 to 40 μm is 60 to 90% by weight on a dry weight basis, and has a melting temperature of 1050 to 125%.
At 0 ° C., the inorganic sintered material having an average particle diameter of 0.2 to 15 μm is 10 to 40% by weight on a dry weight basis, and the inorganic thickener is 0 to 25% by weight on a dry weight basis (coal ash, inorganic sintered material and inorganic thickener). The mixture obtained by mixing the dry weight of the viscous material with 100% by weight) and water is kneaded and extruded while at least temporarily degassed, dried, and then dried.
The method for producing a ceramic molded article according to claim 1, wherein the heat treatment is performed at 0 ° C.