JP6337403B2 - Porous ceramic fired body and method for producing the same - Google Patents

Description

The present invention relates to a fired porous ceramic body and a method for producing the same.
This application claims priority based on Japanese Patent Application No. 2013-038700 for which it applied to Japan on February 28, 2013, and uses the content here.

Generally, a porous ceramic fired body is used as a fireproof heat insulating material, a water purification material, a humidity control material, a volatile organic compound (VOC) adsorbing material, or the like.
In recent years, porous ceramic fired bodies have various properties such as sound absorption, heat insulation, water retention, water permeability, or incombustibility derived from porous materials, for example, wall materials and roofing materials for buildings such as buildings, The use of roads and parking lots as roadbed materials is under consideration.

Examples of the structure of such a porous ceramic fired body include a closed-cell type, a lattice-structure type, an aggregate-type, a type having a minute crack pore, a type having a continuous through-hole, and the like. Is done.
For example, a porous ceramic sintered body obtained by sintering a molded body such as diatomaceous earth, slag, or clay has been proposed (for example, Patent Document 1). Since the porous ceramic fired body of Patent Document 1 has a binary structure in which macropores derived from diatomite and artificially generated millimeter-sized tunnel structure pores are interconnected, fire resistance and sound absorption are improved. In addition to being excellent, it is easy for water to penetrate and has excellent water retention.
However, although the technique of Patent Document 1 can improve fire resistance and sound absorption, there is a problem that strength required for building materials is insufficient. A versatile porous ceramic fired body as a building material is required to have sufficient strength, particularly sufficient bending strength, while maintaining various characteristics.

  By the way, in recent years, a large amount of fly ash has been discharged due to an improvement in the operating rate of coal-fired power plants using coal. For this reason, reuse of fly ash is desired, and for example, a porous ceramic fired body obtained by using fly ash, glass, or clinker ash has been proposed (for example, Patent Document 2).

JP 2005-239467 A JP 2012-131702 A

However, in the technique of Patent Document 2, although the strength is increased, since the porosity is low, various properties required for the porous ceramic fired body are insufficient.
In addition, with the technique of Patent Document 2, it is difficult to obtain a plate-like or columnar molded product.
Furthermore, fly ash may contain heavy metals such as chromium or arsenic. When fly ash is used, it is necessary to suppress elution of heavy metals.
Therefore, the present invention aims at a porous ceramic fired body having various properties and high strength.

The porous ceramic fired body of the present invention is obtained by firing a mixture containing fly ash, and has a saturated moisture content of 15 to 80% by mass.
The amount of elution of heavy metals is below the environmental standard related to soil contamination (August 23, 1991, Environment Agency Notification No. 46). More specifically, the porous ceramic fired body is immersed in water, In the concentration of the eluted heavy metal in the water, cadmium is 0.01 mg / L or less, lead is 0.01 mg / L or less, hexavalent chromium is 0.05 mg / L or less, arsenic is 0.01 mg / L or less, total Preferably, mercury is 0.0005 mg / L or less, alkylmercury is 0.0005 mg / L or less, and selenium is 0.01 mg / L, and the mixture includes the fly ash, clays, blowing agent, organic sludge, It is preferable that it is contained, it is preferable that it is a plate-shaped object or a columnar object, and it is preferable that bending strength is 3.0 N / mm < ² > or more.

The method for producing a fired porous ceramic body of the present invention includes a mixing step of obtaining a mixture containing fly ash, a forming step of forming the mixture to obtain a shaped body, firing the shaped body, and having a saturated moisture content. And a firing step for obtaining a porous ceramic fired body of 15 to 80% by mass.
In the mixing step, the fly ash, clays, foaming agent, and organic sludge are preferably mixed.
In the mixing step, the fly ash is 3 to 35% by mass, the clays are 10 to 50% by mass, the foaming agent is 20 to 65% by mass, and the organic sludge is based on the total mass of the mixture. It is preferable to mix 5-60 mass%.

  The fired porous ceramic body of the present invention can improve strength while having sufficient characteristics.

(Porous ceramic fired body)
The porous ceramic fired body according to one embodiment of the present invention is obtained by firing a mixture containing fly ash.

The size of the pores formed in the porous ceramic fired body can be determined in consideration of the application. For example, the pores may be nanometer-order pores having a pore diameter of 1 nm or more and less than 1000 nm, or micrometer-order pores having a pore diameter of 1 to 1000 μm. The pores may be pores or may be pores in the order of millimeters having a pore diameter of more than 1 mm and not more than 2000 mm.
The pore diameter can be adjusted by combining the types of raw materials and the firing conditions. The pore diameter refers to the major diameter of the pores.
The pore diameter of the order of millimeters is a value measured using a scale obtained by cutting a porous ceramic fired body along its thickness direction. The pore diameter of the nanometer-order pores and the pore diameter of the micrometer-order pores are values measured by cutting the porous ceramic fired body along the thickness direction and using an electron microscope.

The pores of the porous ceramic fired body may be independent or may be communication holes communicating with each other. The porous ceramic fired body preferably has communication holes from the viewpoint of improving heat insulation, sound absorption, water retention, water permeability, or air permeability. More preferably, the communication hole is formed through the porous ceramic fired body.
The porous ceramic fired body may contain two or more kinds selected from millimeter-order pores, micrometer-order pores, and nanometer-order pores, and these may be in communication with each other. Such a form is preferable because it can absorb water quickly (having a high permeability coefficient), increase water retention, and appropriately evaporate water, thereby suppressing the heat island phenomenon.

The porous ceramic fired body has a saturated moisture content of 15 to 80% by mass, preferably 20 to 70% by mass, and more preferably 30 to 50% by mass, which is determined by the formula described below. If it is less than the said lower limit, the porosity of a porous ceramic sintered body is inadequate, and sufficient characteristics cannot be exhibited. If the value exceeds the upper limit, the porosity becomes too high, and the strength of the porous ceramic fired body becomes insufficient.
The porosity is the ratio of the pore volume per unit volume.
Here, the saturated water content is the content of water relative to the total mass of the porous ceramic fired body in a saturated state of water. This saturated moisture content is calculated | required, for example with the following formula | equation.
Saturated water content (mass%) = [(saturated water content mass−absolute dry mass) / absolute dry mass] × 100
Here, the saturated state is a state in which the pores are almost filled with water, specifically, the porous ceramic fired body is immersed in water and the air in the pores is replaced with water. State. When measuring the saturated mass, for the porous ceramic fired body having parallel pores, immerse the porous ceramic fired body in water for about 30 to 120 minutes, take out from the water so that water does not flow out, The mass may be measured.
The absolutely dry state is a state where the porous ceramic fired body is dried at 105 to 115 ° C. (for example, 100 to 110 ° C.) until a constant weight is obtained (for example, 24 hours). More specifically, drying may be performed in accordance with JIS A 1509-3. When measuring the absolutely dry mass, you may measure using the drying loss method shown by JISK0067-1992, for example.

The apparent density represented by [mass of porous ceramic fired body (g)] / [volume of porous ceramic fired body (cm ³ )] is preferably 0.6 to 2 g / cm ³ , more preferably 0.00. It is 6-1.5 g / cm < ³ >, More preferably, it is 0.6-1.1 g / cm < ³ >, Most preferably, it is 0.65-0.85 g / cm < ³ >. If it is in the said range, while the intensity | strength of a porous ceramic sintered body can be raised more, various characteristics according to a use can be improved. Here, the mass of the porous ceramic fired body is a value in an absolutely dry state.

The shape of the porous ceramic fired body can be determined in consideration of the application and the like, and examples thereof include a flat plate-like product, a columnar product such as a prismatic shape or a cylindrical shape, or a granular material. Especially, the effect of this embodiment is remarkable in the plate-like thing or columnar thing suitable as building materials, such as a wall material, a floor material, or a roadbed material. As a guide, a plate-like object refers to a shape having a length and width that are large relative to the thickness, in particular, a size that is twice or more, and more preferably a long side of 3 cm or more. A columnar object refers to a shape having a length that is larger than a width and a height, particularly a size that is twice or more. Examples of the granular material include those obtained by crushing the plate-like material, and those obtained by forming pellets and firing, and having a long side of less than 3 cm, such as a columnar shape, needle shape, spherical shape, plate shape, or irregular shape. In addition, even if the major axis is 3 cm or more, an irregular shape is a granular material.
The size of the porous ceramic fired body can be determined in consideration of the use and construction method. For example, if the porous ceramic fired body is a plate-like material, the length is 5 to 200 cm × width is 5 to 200 cm × thick. It is set to 1-10 cm.
For example, in the case of a porous ceramic fired body that is a columnar product, the length is 5 to 200 cm × width 1 to 200 cm × height 1 to 200 cm.
The granular material is suitable for block aggregates, concrete aggregates, soil improvement materials, and the like.

When the porous ceramic sintered body has a plate-like material or pillars, its flexural strength is preferably 3.0 N / mm ² or more, 5N / mm ² or more, more preferably, 7N / mm ² or more and more preferably, 10 N / Mm ² or more is particularly preferable. If the bending strength is 3.0 N / mm ² or more and a sufficient strength as a roof material, a sufficient strength as a roadbed material of a road surface on which long 5N / mm ² or more tracks such passes.
The bending strength can be measured by a method based on JIS R5201, for example.

It is preferable that the porous ceramic fired body satisfies the environmental standard (August 23, 1991, Environment Agency Notification No. 46) relating to soil contamination in the amount of elution of each component, particularly heavy metals. The elution amount of heavy metal is the amount of heavy metal that is eluted when exposed to an environment such as being immersed in water. Specifically, the porous ceramic fired body is immersed in water (or an aqueous solution of acid or the like), and the concentration of heavy metal eluted in the water is measured. Although it is preferable to determine the conditions of immersion by each measuring method mentioned later, as an example, it is immersed for 1 to 30 minutes in general, and depending on the heavy metal which is hard to detect, it is immersed in the boiled water.
As a more specific example, the measurement is performed by each measurement method described in Table 2 and Table 3 described later. Satisfying the environmental standard means that the detected value of the elution amount satisfies each standard value described in the table. By satisfying the environmental standards in the fired porous ceramic body of the present embodiment, fly ash can be effectively utilized.
The heavy metals specified in the environmental standards are cadmium, lead, hexavalent chromium, arsenic, mercury and selenium. More specifically, the elution amount (detection value) of cadmium is 0.01 mg / L or less (for example, according to the measurement method of JIS K0102 55.4), and the elution amount of lead is 0.01 mg / L or less. (E.g., according to the measurement method of JIS K0102 54.4), the elution amount of hexavalent chromium is 0.05 mg / L or less (e.g., according to the measurement method of JIS K0102 65.201), and the elution amount of arsenic is 0.1. It must be 01 mg / L or less (for example, according to the measurement method of JIS K0102 61.4), and the total mercury elution amount must be 0.0005 mg / L or less (for example, Measurement of Environment Agency Notification No. 59, Appendix 1 in 1971) The amount of alkylmercury elution is 0.0005 mg / L or less (for example, according to the measurement method of 1971, Environment Agency Notification No. 59, Appendix 2), and The selenium elution amount is 0.01 mg / L or less (for example, according to the measurement method of JIS K0125 67.4).
In addition to those shown in Table 2, the elution amount of hexavalent chromium is 0.05 mg / L or less (for example, according to the measurement method of JIS K0102 65.2.1), and the quantification limit of arsenic is 0.005 mg / L. The quantitative limit of PCB may be 0.0005 mg / L, and the quantitative limit of dichloromethane may be 0.002 mg / L. In addition to those shown in Table 3, selenium is JIS K0102 67.4, fluorine is JIS K0102 34.1, boron is JIS K0102 47.3, nitrate nitrogen is JIS K0102 432.3, nitrite nitrogen is JIS K0102 43.1.1, ammoniacal nitrogen may be measured by the measuring method of JIS K0102 42.2, and the hydrogen ion concentration may be measured by the measuring method of JIS K0102 12.1, and these may be used in combination with the above-mentioned conditions.
The conditions for the elution amount of these heavy metals can be achieved by the composition of the mixture described later.

<Fly ash>
Fly ash is fired together with clays, foaming agents, organic sludge and the like, which will be described later, and the strength of the porous ceramic fired body can be increased by being taken into the porous ceramic fired body.
Fly ash is ash produced when coal is burned in a thermal power plant or the like, and is a particle having a size enough to be blown up together with fuel gas. Generally, fly ash is obtained by collecting the blown ash with an electric dust collector or the like.
As a fly ash in this embodiment, from the viewpoint of quality stability, a fly ash specified in JIS A6201 is preferable as a concrete fly ash, and I, II, III, or IV specified in JIS A6201. Either of these may be used.
The porous ceramic fired body of the present embodiment is obtained by firing a mixture containing fly ash, which will be described in the manufacturing method described later, but the total mass of the mixture is 3 to 35 with respect to the mixture before firing. It is baked after containing by mass.

<Optional component>
In addition to fly ash, the porous ceramic fired body of the present embodiment includes clay, foaming agent, organic sludge, diatomaceous earth, fluidizing agent, adsorbent, antibacterial agent, deodorant, pigment, clinker ash, tile A crushed material, a crushed glass material, or the like can be used. Further, in order to improve the strength of the porous ceramic fired body, a high melting point glass particle having a melting point of 900 ° C. or higher, a filler such as carbon fiber, basalt fiber, or rock wool may be used.
By firing the mixture obtained by mixing these raw materials, the porous ceramic fired body of the present embodiment can be easily obtained.
As a mixture in this embodiment, what contains fly ash, clays, a foaming agent, and organic sludge is preferable. A porous ceramic fired body obtained by firing a mixture containing clays, foaming agent, and organic sludge has excellent saturation moisture content, water absorption coefficient, heat insulation, heat island phenomenon suppression, plant growth performance, etc. It is expected to be used in various fields including building materials. Furthermore, the strength of the fired porous ceramic body can be remarkably increased by adding fly ash to the mixture.
In the porous ceramic fired body obtained by firing a mixture of clay, foaming agent and organic sludge, the bending strength of the porous ceramic fired body can be significantly increased by adding fly ash to the mixture.
Conventionally, in the mixing step of mixing clays, foaming agent, and organic sludge, large aggregates are formed, and clays (clay), foaming agent, and organic sludge used as raw materials are uniformly mixed. Therefore, it took a long time to blend, and the quality of the obtained porous ceramic fired body varied. By adding fly ash to the mixture, the raw materials can be mixed smoothly (good mixability) and the quality can be made uniform.

≪Clays≫
Clays (clay) in the present embodiment are mineral materials that exhibit clay-like properties that are generally used as ceramic materials. In the present embodiment, the clays exclude diatomaceous earth described later.
As clays, known materials used for ceramic fired bodies can be used, which are composed of a mineral composition such as quartz, feldspar, or clay, and the constituent minerals are mainly kaolinite, halloysite, montmorillonite, illite, bentonite. Or those containing pyrophyllite are preferred.
Among these, those containing coarse quartz grains having a particle size of 500 μm or more are preferred from the viewpoint of suppressing crack extension during firing and preventing destruction of the fired porous ceramic body. The coarse quartz particles preferably have a particle diameter of 5 mm or less. Examples of such clays include cocoon clay. As clays, various types having different physical properties such as composition (including the above-described various minerals), constituting particle diameters, and moisture content can be used alone or in appropriate combination of two or more.

  The content of clays in the mixture before firing can be determined in consideration of the strength and formability required of the porous ceramic fired body, and may be 5 to 60% by mass with respect to the total mass of the mixture. If the content of the clays in the mixture is within the above range, the moldability of the mixture can be smoothly formed without sacrificing, and the strength of the fired porous ceramic body can be made sufficient. For the advantage that the moldability of the mixture and the strength of the fired porous ceramic body are improved, the content may be 10 to 40% by mass. As described later, when emphasizing the point of preventing porosity and elution of heavy metals, it may be 10 to 50% by mass, and more preferably 20 to 45% by mass.

≪Foaming agent≫
The foaming agent in this embodiment foams at the time of baking, For example, well-known foaming agents for ceramics, such as calcium carbonate, silicon carbonate, magnesium carbonate, or slag, can be used. Of these foaming agents, slag is preferred.
Slag is not particularly limited, for example, blast furnace slag generated during metal refining, municipal waste melting slag generated during melting of municipal waste, sewage sludge melting slag generated during melting of sewage sludge, or generated in cast iron such as ductile cast iron Glass iron slag such as cast iron slag to be used, among others, because the composition is stable, a stable foamed state is obtained, and cast iron slag having a foaming ratio of about 1.5 to 2 times that of other slags Is more preferable. By using cast iron slag, for example, form pores in the order of millimeters with a shape in which the length in the thickness direction of the porous ceramic fired body is shorter than the length in the length direction or width direction of the porous ceramic fired body, It can increase the water permeability (speed of passing water) and increase water retention.
20-65 mass% may be sufficient with respect to the whole mass of a mixture for content of the foaming agent in a mixture.

≪Organic sludge≫
Organic sludge is sludge containing an organic substance as a main component. Any organic sludge added to the mixture can be used. Activated sludge derived from sewage or wastewater treatment at a factory or the like may be used. The activated sludge is discharged from a wastewater treatment facility using the activated sludge method through a coagulation / dehydration process. By using such organic sludge in the mixture, it is possible to form pores on the order of micrometers and even pores on the order of nanometers. Furthermore, the activated sludge derived from wastewater treatment, which has been positioned as waste, can be reused as a raw material.

  The water content of the organic sludge may be, for example, 5 to 90% by mass, preferably 60 to 90% by mass, and more preferably 65 to 85% by mass with respect to the total mass of the organic sludge. This is because, within the above range, a homogeneous mixture can be obtained in the mixing step described later, and good moldability can be maintained in the molding step. When the water content is 65 to 85% by mass, the homogeneity and the moldability can be further achieved.

  The content of the organic matter contained in the organic sludge is not particularly limited. For example, the organic matter content (organic matter content) in the solid content of the organic sludge is 70 to 100% by mass with respect to the total mass of the organic sludge. May be. This is because the larger the organic content, the easier the formation of micrometer-order pores. The content of the organic matter may be 80 to 90% by mass with respect to the entire mass of the organic sludge, and these pores can be more suitably formed within this range. The organic content is a value obtained by measuring the ash content (mass%) of the dried sludge in accordance with JIS M8812-1993 at a carbonization temperature of 700 ° C. and the following equation (1).

  Organic matter content (mass%) = 100 (mass%) − ash content (mass%) (1)

  The average particle diameter of the organic sludge can be determined according to the use of the porous ceramic fired body, and may preferably be 1 to 5 μm. More preferably, the average particle diameter may be 1 to 3 μm, and these pores can be more suitably formed within this range. The average particle diameter is a volume-based median diameter (50% volume diameter) measured by a particle size distribution measuring device (LA-920, manufactured by Horiba, Ltd.).

  The content of organic sludge in the mixture can be determined in consideration of the moldability of the mixture. 1-60 mass% may be sufficient with respect to the whole mass of a mixture. If it is in the said range, a mixture will have moderate fluidity | liquidity and plasticity, a moldability will improve, and it can shape | mold smoothly, without obstruct | occluding a shaping | molding apparatus. The content may be 5 to 60% by mass, may be 5 to 30% by mass, and may be 5 to 20% by mass.

≪Diatomaceous earth≫
Examples of diatomaceous earth include deposits made of diatom remains and containing porous particles having pores on the order of micrometers. By using diatomaceous earth for the mixture, fine pores derived from diatomaceous earth can be formed in the porous ceramic fired body.

Diatomaceous earth is not particularly limited, and those conventionally used for refractory bricks or filter media can be used. For example, it is not necessary to separately refine and refine clay minerals (montmorillonite, etc.), quartz, or feldspar, etc., and the amount of the mixture can be adjusted after recognizing these contents. Moreover, you may grind | pulverize and use what was used for the stove, the brick, etc., and waste can be reduced by applying these.
The moisture content of diatomaceous earth is not particularly limited, and for example, the moisture content in a naturally dry state is preferably 20 to 60 mass%, more preferably 30 to 50 mass%, and more preferably 35 to 45 mass% with respect to the entire mass of diatomaceous earth. Further preferred.
If it is within the above range, it is because a mixture with good moldability can be obtained by removing the coarse particles in the narrow material during mixing while recognizing the moisture content.
In addition, the moisture content of diatomaceous earth can be calculated | required by the drying weight loss system calculated | required using the following (2) formula from the mass of the sample before and after drying, for example. More specifically, it is preferable to use an infrared moisture meter and dry the sample at about 0 to 200 ° C. for 5 minutes or more, more preferably 10 to 30 minutes. In this embodiment, an infrared moisture meter having the following specifications is used, the sample is dried (200 ° C., 12 minutes), and the value obtained by the following equation (2) is used.

<Specifications>
Measurement method: Loss on drying method (heat drying / mass measurement method)
Minimum display: moisture content; 0.1% by mass
Measurement range: moisture content; 0.0 to 100% by mass
Drying temperature: 0-200 ° C
Measurement accuracy: sample weight 5g or more, moisture content ± 0.1% by mass
Heat source: infrared lamp; 185W

Water content (mass%) = [(m1-m2) / (m1-m0)] × 100 (2)
m1: Total mass (g) of the weight of the container before drying and the weight of the sample before drying
m2: Total mass (g) of the mass of the container after drying and the mass of the sample after drying
m0: Weight of container after drying (g)

  The content of diatomaceous earth in the mixture can be determined in consideration of the saturated moisture content and strength required for the porous ceramic fired body, and may be, for example, 1 to 55% by mass with respect to the total mass of the mixture. If it is below the above upper limit value, the moldability of the mixture is good, and if it is above the above lower limit value, a porous ceramic fired body having a desired saturation moisture content or a porous ceramic fired body having a desired strength can be obtained. Cheap. The content may be 1 to 45% by mass with respect to the total mass of the mixture, and in this range, a more preferable saturated water content and strength of the porous ceramic fired body can be obtained.

≪Fluidizer≫
As the fluidizing agent, conventionally known ones can be used. For example, naphthalene-based fluidizing agents such as Mighty 2000WH (trade name, manufactured by Kao Corporation), Melment F-10 (trade name, Showa Denko KK) Melamine-based fluidizing agents such as Dalex Super 100 pH (trade name, manufactured by Grace Chemicals Co., Ltd.) and the like.

≪Antimicrobial agent≫
A conventionally well-known antibacterial agent can be used as an antibacterial agent, Silver, copper, or zinc etc. are mentioned.

≪Adsorbent≫
A conventionally well-known thing can be used as an adsorbent, For example, adsorbents, such as a zeolite or apatite, are mentioned.

≪Deodorant≫
Moreover, when a bad odor arises from organic sludge, it is good to mix | blend a deodorizer. Examples of the deodorant component include ammonium chloride and zinc chloride. When a deodorant having such a component is used, it is possible to suppress bad odors produced from organic sludge by neutralizing odorous components such as hydrogen sulfide and deodorizing odor from organic sludge.

≪Filler≫
Examples of the filler include particles of high melting point glass having a melting temperature of 900 ° C. or higher, carbon fiber, basalt fiber, rock wool, and the like. For example, when a raw material containing a high-melting glass as a filler is fired, the high-melting glass is partially melted and fused with fillers or functions as a binder for clays, etc. Further improvement in strength can be achieved. In addition, carbon fiber, basalt fiber, or rock wool is incorporated into the porous ceramic fired body, thereby producing an effect of further improving the strength of the porous ceramic fired body.

(Production method)
The method for producing a porous ceramic fired body according to the present embodiment includes a mixing step of obtaining a mixture containing fly ash, a forming step of shaping the mixture to obtain a shaped body, and firing the formed body to obtain a porous ceramic fired body. And obtaining a firing step.
Below, the manufacturing method of the porous ceramic fired body of this embodiment is demonstrated taking the case where fly ash, clays, a foaming agent, and organic sludge are used for a raw material as an example.

<Mixing process>
The mixing step is a step of obtaining a mixture by mixing raw materials including clays. In this embodiment, in this step, a material containing fly ash, clays, foaming agent, and organic sludge is mixed to obtain a mixture.

  The content of clays in the mixture is, for example, preferably 10 to 50% by mass and more preferably 20 to 45% by mass with respect to the total mass of the mixture. If it is less than the said lower limit, a moldability may fall and it may be difficult to obtain a plate-shaped object and a columnar object, intensity | strength may fall, or a heavy metal derived from fly ash may become easy to elute. If the value exceeds the upper limit, the porosity may decrease, the saturated moisture content may decrease, and various characteristics may decrease.

The content of fly ash in the mixture can be determined in consideration of the strength required for the porous ceramic fired body, the amount of heavy metal contained in the fly ash, and the like, for example, 3 to 35% by mass with respect to the total mass of the mixture Preferably, 6-35 mass% is more preferable, and 9-35 mass% is further more preferable. If it is less than the said lower limit, intensity | strength cannot fully be raised or there exists a possibility that mixing property may fall. If the value exceeds the upper limit, the saturated moisture content may decrease and various characteristics may decrease, or the moldability may decrease and it may be difficult to obtain a plate-like object or a columnar object. In addition, if the value exceeds the upper limit, the molded product is difficult to dry and the productivity is lowered, or the molded product may be damaged during firing due to a large amount of residual moisture.
In the mixture, the mass ratio represented by fly ash / clay is preferably 0.1 to 1.3, more preferably 0.2 to 1.0, and still more preferably 0.3 to 0.6. If it is at least the above lower limit value, the strength can be further improved, and if it is at most the above upper limit value, the moldability can be further improved.

20-65 mass% is preferable with respect to the whole mass of a mixture, for example, and, as for content of the foaming agent in a mixture, 30-55 mass% is more preferable. If it is less than the above lower limit, the porosity may decrease, the saturated water content may decrease, and various properties may be deteriorated.If the above upper limit is exceeded, the moldability is impaired, the porosity is excessively increased, and the strength May decrease.
In the mixture, the mass ratio represented by the foaming agent / clay is preferably 0.5 to 3.5, and more preferably 0.6 to 3.0. If it is more than the said lower limit, further improvement of various characteristics can be aimed at, and if it is less than the said upper limit, the further improvement of a moldability and intensity | strength can be aimed at.

The content of organic sludge in the mixture may be, for example, 1 to 60% by mass, and preferably 5 to 60% by mass with respect to the total mass of the mixture. If it is less than the above lower limit, pores in the order of nanometers or micrometer order may be reduced, and various properties may be deteriorated. If the value exceeds the above upper limit, formability may be impaired or the strength may be decreased. is there. In order to improve the moldability of the mixture, 8 to 50% by mass is more preferable. In order to increase the strength of the mixture by reducing the amount of organic sludge, the content may be 5 to 30% by mass.
In the mixture, the mass ratio represented by organic sludge / clays is preferably 0.1 to 2.5, and more preferably 0.2 to 1.0. If it is more than the said lower limit, further improvement of various characteristics can be aimed at, and if it is less than the said upper limit, the further improvement of a moldability and intensity | strength can be aimed at.

  Although the moisture content of a mixture is not specifically limited, 10-35 mass% is preferable with respect to the whole mass of a mixture, and 15-30 mass% is more preferable. This is because the mixture has appropriate plasticity and fluidity within the above range and can maintain good moldability. In order to adjust the moisture content of the mixture, water may be added to the mixture.

In addition, in a mixing process, arbitrary components other than the above may be mixed as needed.
For example, when adding a filler to a mixture, content of the filler in a mixture is determined in consideration of the kind etc. As for content of the filler in a mixture, 0.01-20 mass parts is preferable with respect to a total of 100 mass parts of raw materials other than a filler, for example. By setting it as the said lower limit or more, the effect which added the filler is acquired suitably, and suitable moldability is acquired by setting it as the said upper limit or less. The content may be 0.01 to 10 parts by mass. If the content is within this range, both the strength of the porous ceramic and the moldability of the mixture can be obtained more suitably. In order to achieve both the strength of the porous ceramic and the moldability of the mixture, the content may be 0.05 to 5 parts by mass, and particularly preferably 0.1 to 2 parts by mass.

  The content of each raw material in the mixture described above is adjusted to be 100% by mass in the entire mixture, and when arbitrary components other than those described above are mixed, the total content including those components is adjusted to 100 parts by mass. The

  The order of mixing the raw materials in the mixing step is not particularly limited, and examples thereof include a method in which fly ash, clays, foaming agent, organic sludge, or other optional components are previously charged in a mixing apparatus and mixed.

As the mixing step, various mixing operations such as kneading, stirring, and shaking can be arbitrarily used. The mixing apparatus used for this mixing process is not specifically limited, A well-known mixing apparatus can be used.
For example, as a mixing apparatus, a kneader such as a mix muller (manufactured by Toshin Kogyo Co., Ltd.), a kneader (manufactured by Moriyama Co., Ltd.), a mixer (manufactured by Nippon Ceramic Science Co., Ltd.) or the like can be mentioned.

  The mixing time in the mixing step can be determined in consideration of the content of each raw material, the fluidity of the mixture, and the like, and it is preferable to determine the mixing time such that the mixture is in a plastic state. For example, the mixing time is preferably 15 to 45 minutes, more preferably 25 to 35 minutes.

<Molding process>
The forming step is a step of forming the mixture obtained in the mixing step into an arbitrary shape.
As the forming method, a known forming method can be used, which can be determined in consideration of the properties of the mixture and the shape of the porous ceramic fired body. For example, in the case of producing a porous ceramic fired body of a plate or columnar shape, a method of obtaining a molded body having a desired shape by performing an operation of extruding and cutting the mixture using a molding machine is desired. And a method of obtaining a molded body by filling a mold having a shape to be formed, or a method of stretching or rolling the mixture and then cutting it into a desired dimension.
Examples of the molding machine include a vacuum clay molding machine, a flat plate press molding machine, and a flat plate extrusion molding machine. Among these, a vacuum clay molding machine is preferable. By removing the air in the molded body using a vacuum clay molding machine, the porosity in the fired porous ceramic body can be controlled.

  When manufacturing a porous ceramic fired body of a granular material, for example, using a primary screw extrusion molding machine or a disk-type die horizontal extrusion molding machine, the mixture is cut while being extruded from a die hole, and is cylindrical or prismatic. To obtain a molded product. In this case, the size of the molded body is, for example, 5 to 20 mm in diameter.

<Baking process>
In the firing step, the molded body obtained in the molding step is dried (drying operation), the dried molded body is fired (firing operation), and optional components such as fly ash, clays, foaming agent, or organic sludge are fired. In this step, a porous ceramic fired body is obtained.

≪Drying operation≫
The drying operation is a step of adjusting the molded body to an arbitrary moisture content.
The drying method is not particularly limited, and a known method can be used. For example, the molded body may be naturally dried, or may be dried by treatment in a hot air drying oven at 50 to 220 ° C. for an arbitrary time. Although the moisture content of the dried molded object is not specifically limited, For example, less than 5 mass% is preferable and less than 1 mass% is more preferable.
This drying operation may be shortened or omitted. By appropriately shortening or omitting the drying operation, cracks and the like can be formed in the fired body.

≪Baking operation≫
The firing operation is an operation of firing the dried molded body at an arbitrary temperature.
The firing method is not particularly limited, and a known method such as a closed system or an open system can be used. For example, there is a method of firing at an arbitrary temperature using a continuous sintering furnace such as a roller hearth kiln or a batch sintering furnace such as a shuttle kiln. Among these, from the viewpoint of productivity, it is preferable to use a continuous sintering furnace for the firing operation.

The firing temperature (attainable temperature) can be determined in consideration of the blending ratio of raw materials. When fly ash, clay, or foaming agent and organic sludge are included in the raw material, fly ash and clay are fired, the organic matter contained in the organic sludge is volatilized and reduced by thermal decomposition, and foaming agents such as slag The condition is to expand. For example, the firing temperature is preferably 900 to 1250 ° C, and more preferably 950 to 1200 ° C. Most of organic substances start to decompose at around 700 ° C., and the odor peculiar to organic sludge is eliminated by thermally decomposing odor components at 950 ° C., and most of the organic substances in the organic sludge are volatilized and reduced. Moreover, most of the cast iron slag, which is a foaming agent, expands by crystallization at 800 to 850 ° C. Then, pores are formed by the reduction of the organic matter or the expansion of the cast iron slag, and the clays or a part of the fly ash is melted to contain the heavy metal contained in the fly ash.
When the firing temperature exceeds 1250 ° C., vitrification of the entire structure of the porous ceramic fired body proceeds, and the compact may be crushed or pores may be blocked during firing.

  In the firing operation, moisture is first evaporated from the compact before reaching the firing temperature, and then the organic matter of the organic sludge is volatilized through thermal decomposition. In this process, by appropriately adjusting the temperature rise (heat curve or temperature gradient), rapid evaporation of water or rapid evaporation of organic substances can be suppressed, and pulverization (explosion) of the compact can be prevented. In addition, the rapid cooling after reaching the firing temperature may cause breakage such as cracking or pulverization in the porous ceramic fired body. Such a phenomenon is particularly noticeable in a continuous sintering furnace. For this reason, it is preferable to provide a temperature gradient in the firing step.

The temperature gradient can be determined in consideration of the scale of the baking apparatus. For example, when firing using a continuous sintering furnace having an effective length of 15 m, the inlet and outlet of the continuous sintering furnace are at room temperature (20 ° C. ± 15 ° C.), and the central part of the continuous sintering furnace The firing temperature is 900 to 1250 ° C., and the passing speed of the compact in the continuous sintering furnace is 3 to 4 mm / sec. And the following temperature gradient conditions are preferable.
As for the temperature gradient, for example, the continuous sintering furnace is divided into 10 zones of equal distance, and the temperature gradient of the continuous sintering furnace is 0.4 to 0.6 ° C./sec. 0.1-0.2 ° C./sec. 0.3-0.4 ° C./sec. 0.4-0.6 ° C./sec. 0.7-1.0 ° C./sec. 0.004 to 0.005 ° C./sec. , −0.4 to −0.2 ° C./sec. , −0.8 to −0.5 ° C./sec. , −0.4 to −0.3 ° C./sec. , −0.3 to −0.1 ° C./sec. It can be.

  The firing time can be determined in consideration of the firing temperature, the moisture content of the molded body, and the like. For example, the residence time in the firing part is preferably 10 minutes to 72 hours, preferably 10 in the case of a continuous sintering furnace. Minutes to 300 minutes, more preferably 30 minutes to 120 minutes. If it is in the said range, it can be favorably fired while preventing the porous ceramic fired body from being damaged.

  The porous ceramic fired body obtained by firing is cut as it is, or cut into an arbitrary size or shape, or is hollowed out or joined, or the surface is ground or crushed for any use. Used.

  As described above, the porous ceramic fired body has high strength while having various characteristics. For this reason, the porous ceramic fired body of this embodiment is a building material such as a wall material, a roof material, a floor material, a roadbed material, or an aggregate, a cooling member for an outdoor unit, a plant growth base material, a water purification material, or It can be suitably used as a soil improving material. Further, for example, the porous ceramic fired body of the present embodiment can be used as a material in a production method for producing these.

  EXAMPLES Hereinafter, although an Example is shown and this embodiment is described in detail, this embodiment is not limited by the following description.

(Raw materials used)
<Fly ash>
As the fly ash, JIS A6201 “Fly ash for concrete” was used.
About this fly ash, the elution amount of each item was measured according to the environmental standard (September 23, 1991, Environment Agency Notification No. 46) concerning soil contamination, and the results are shown in Tables 2-3.
In Tables 2 and 3, the “standard value” is a standard value defined in the environmental standard (August 23, 1991, Environment Agency Notification No. 46).
<Organic sludge>
For the organic sludge, activated sludge discharged through a coagulation / dehydration process from a wastewater treatment facility using an activated sludge method at a dyeing factory (Komatsu Seiren Co., Ltd., Mikawa Factory) was used. The organic matter content (relative to the solid content) of the activated sludge was 83% by mass with respect to the total mass of the activated sludge. The water content was 85% by mass with respect to the total mass of the activated sludge.
<Clays>
As the viscosity (clay), Sasame clay (produced in Gifu Prefecture) was used.
<Foaming agent>
Dugtile cast iron slag was used as the foaming agent. This ductile cast iron slag is a ductile cast iron slag mainly composed of SiO ₂ , Al ₂ O ₃ , CaO, Fe ₂ O ₃ , FeO, MgO, MnO, K ₂ O, and Na ₂ O.

(Measuring method)
<Apparent density>
The external dimensions of the sample were measured with calipers to determine the volume. The sample was completely dried, the mass was measured with an electronic balance (mass dried), and the apparent density was calculated by the following equation (3). The number of samples (N) was N = 10, and the average value was obtained.
Apparent density (g / cm ³ ) = [absolutely dry mass (g)] / [volume (cm ³ )] (3)

<Saturated water content>
The porous ceramic fired body of each example was immersed in water for 60 minutes, taken out from the water, contacted with the fabric to such an extent that water droplets on the surface were removed, and immediately measured for mass (saturated hydrous mass). ) To obtain the saturated water content. The saturation moisture content was measured for the number of samples (N) = 10, and the average value was obtained. In addition, when the porous ceramic fired body is a plate-like material, the sample was taken out from the water with the surface facing up (the cut surface is the side surface) and the mass was measured (to prevent water from flowing out of the sample). ).
Saturated water content (mass%) = [(saturated water content mass−absolute dry mass) / absolute dry mass] × 100 (4)

<Bending strength>
Using a universal material testing machine AGS-500D (manufactured by Shimadzu Corporation), bending strength was measured in accordance with JIS R5201 (three-point bending strength test method, span interval 5 cm). The number of samples (N) was N = 10, and the average value was obtained. The unit was N / mm ² .

<Confirmation of pore communication>
Confirmation of the presence or absence of pores in the porous ceramic fired body was confirmed by immersing the obtained porous ceramic fired body in water, sufficiently absorbing water, cutting it, and observing its cross section.
When moisture was evenly distributed and retained in the porous ceramic fired body, it was judged that pores were in communication (indicated as “◯” in the table). When moisture did not spread inside the porous ceramic fired body, it was determined that the individual pores were independent and the pores were not communicated or the pores were not sufficiently communicated (in the table, “× ").

(Examples 1 to 3, Comparative Example 1)
According to the composition of the mixture in Table 1, each raw material was mixed with a mix muller (manufactured by Toshin Kogyo Co., Ltd.) to obtain a mixture. The obtained mixture was extruded into a cylindrical shape using a cylindrical extrusion molding machine (manufactured by Earth Engineering Co., Ltd.). The cylindrical mixture was cut to a length of 1 m, developed and rolled, and then dried with hot air (180 ° C., 0.5 hour) to obtain a plate-like molded body having a water content of 1% by mass or less.
Next, the plate-shaped molded body was fired using a roller hearth kiln (manufactured by Earth Engineering Co., Ltd.) as a continuous sintering furnace. The firing time in the firing process was 65 minutes, and the maximum temperature was fired at 1050 ° C. (firing process) to obtain a plate-like porous ceramic fired body having a length of 1 m × width of 1 m × thickness of 4 cm. The obtained porous ceramic fired body was measured for apparent density, saturated moisture content and bending strength, and was checked for the presence or absence of communication holes, and the results are shown in Table 1.
The porous ceramic fired body obtained in Example 1 was measured for the elution amount of each item in accordance with the environmental standards related to soil contamination (August 23, 1991, Environment Agency Notification No. 46), and the result Are shown in Tables 2-3. In Example 1, the items (hexavalent chromium, arsenic, fluorine, boron, selenium) detected from the raw fly ash were measured.

As shown in Table 1, the bending strength of Examples 1 to 3 to which the present embodiment was applied was 5 N / mm ² or more. The bending strengths of Examples 1 to 3 were 6.7 times, 2.5 times, and 1.8 times, respectively, as compared to the bending strength of Comparative Example 1 in which a mixture containing no fly ash was fired.
In addition, all of Examples 1 to 3 have pores communicating with each other, and are considered to have various properties such as water permeability and water retention.
As shown in Tables 2-3, in Example 1, although the fly ash containing heavy metal is used, the elution amount of heavy metal is an environmental standard related to soil contamination (August 23, 1991, Environmental Agency Notification No. 46) was satisfied. Although selenium was detected, it was 0.002 mg / L, which was significantly lower than the reference value of 0.01 mg / L or less.
From these results, it was found that by applying this embodiment, the strength can be improved while maintaining the various characteristics of the fired porous ceramic body.

Example 4
20% by mass of fly ash, 20% by mass of organic sludge, 20% by mass of clay, and 40% by mass of ductile cast iron slag were mixed with a mix muller (manufactured by Toshin Kogyo Co., Ltd.) to obtain a mixture.
The mixture was extruded into a solid cylinder having a diameter of 1.5 cm using a disk-type die horizontal extrusion molding machine (Earth Engineering Co., Ltd.), and cut to a length of 1 to 5 cm to obtain a cylindrical molded body. The columnar shaped body was dried with hot air (180 ° C., 0.5 hour) to a moisture content of 1% by mass or less.
Next, the cylindrical shaped body was fired using a roller hearth kiln (manufactured by Earth Engineering Co., Ltd.) as a continuous sintering furnace. The firing time in the firing step was 65 minutes and the maximum temperature was fired at 1050 ° C. to obtain a granular porous ceramic fired body having a major axis of 1 cm to 10 cm. Next, these were pulverized and divided into particle sizes of more than 5 mm to 10 mm or less, more than 1 mm to 5 mm or less, and 1 mm or less using a sieve to obtain granular porous ceramic fired bodies of various sizes. Among these, the porous ceramic fired body having a particle diameter of more than 1 mm and not more than 5 mm was measured for bulk density and saturated water content, and confirmed for presence or absence of communication. As a result, the bulk density was 0.50 g / cm ³ and the saturated water content was 43. Mass%, communication was “present”.
From these results, it was found that by applying this embodiment, various characteristics necessary for a porous ceramic fired body are provided even with a granular material.
The bulk density is measured during the measurement by measuring the three-phase distribution according to the three-phase distribution / volumetric weight (actual volume method) described in “Soil Standard Analysis / Measurement Method” (Hakutosha). The bulk density (g / cm ³ ) determined from the dry soil weight (g) was taken as the bulk density.

  The fired porous ceramic body of the present invention can improve strength while having sufficient characteristics.

Claims (8)

A porous ceramic fired body obtained by firing a mixture containing fly ash , clays, a foaming agent and organic sludge, and having a saturated moisture content of 15 to 80% by mass.   The amount of elution of heavy metal is such that the porous ceramic fired body is immersed in water, and the concentration of heavy metal eluted in the water is 0.01 mg / L or less for cadmium, 0.01 mg / L or less for lead, 6 Valence chromium is 0.05 mg / L or less, arsenic is 0.01 mg / L or less, total mercury is 0.0005 mg / L or less, alkylmercury is 0.0005 mg / L or less, and selenium is 0.01 mg / L or less. The porous ceramic fired body according to claim 1. Porous ceramic sintered body according to claim 1 or 2, characterized in that a plate-like material or pillars. The porous ceramic fired body according to claim 3 , wherein the bending strength is 3.0 N / mm ² or more. Mixing step of mixing fly ash, clay, foaming agent and organic sludge to obtain a mixture containing fly ash;
A molding step of molding the mixture to obtain a molded body;
A method for producing a porous ceramic fired body comprising firing the molded body to obtain a fired porous ceramic body having a saturated moisture content of 15 to 80% by mass. In the mixing step, the fly ash is 3 to 35% by mass, the clays are 10 to 50% by mass, the foaming agent is 20 to 65% by mass, and the organic sludge is based on the total mass of the mixture. The manufacturing method of the porous ceramic sintered body according to claim 5 , wherein 1 to 60% by mass is mixed.   The method for producing a fired porous ceramic body according to claim 5 or 6, wherein the moisture content of the organic sludge is 5 to 90 mass% with respect to the total mass of the organic sludge.   The method for producing a fired porous ceramic body according to any one of claims 5 to 7, wherein a content of an organic substance contained in the organic sludge is 70 to 100% by mass with respect to a total mass of the organic sludge. .