JP2958754B2 - Method for producing ceramic foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to the effective use of coal ash discharged from a coal-fired power plant or the like, pulp sludge discharged from a paper mill, and the like. And a method for producing a ceramic foam having high strength.

2. Description of the Related Art Fly ash (hereinafter referred to as FA)
), There are two types of lightweight ceramics: a sintered type and a foamed type. Among the lightweight aggregates of the sintering type, a type in which the raw material particles are sintered (for example, Japanese Patent Application Laid-Open No. 58-99160) and an organic substance are mixed, and the organic substance disappears during firing, and pores are formed. There is a type to be formed, etc., and since the holes are continuous, the specific gravity and the water absorption are relatively large, but industrially easy to produce.

On the other hand, a foaming type (for example,
197343) is generally a material in which closed cells are distributed in the form of foam, has a low specific gravity and a small water absorption, is high in strength, and is industrially useful. However, stable production is difficult, and high-quality raw materials are difficult to obtain. Shirasu balloons and the like that are required and put on the market use high-quality shirasu, clay, etc. as raw materials. These mines are ubiquitous and buried, making mining more difficult as urbanization progresses.

[0004] It is said that foamed ceramics are produced by generating some kind of gas component when a part of the raw material turns into a liquid phase or a glassy state during firing. It is thought to be a similar mechanism. That is, unless a liquid phase or a glass phase is formed as the first condition and a gas is generated as the second condition at the same time, a foamed ceramic cannot be obtained. R famous as a researcher of foam ceramics
The report of iley indicates the range of chemical components that may cause foaming, but even within that range, foaming often does not occur, which is not sufficient.

Gases required under the second condition include CO ₂ , CO, H ₂ O, etc. generated when organic substances are burned, CO ₂ , H ₂ O, etc. generated by thermal decomposition of inorganic substances in raw materials, and mainly O ₂ generated during the reduction of iron compounds in the raw material.
In the prior art, there are some which describe in detail the conditions for generating this gas. For example, JP-A-4-23884
In Patent Document 2, the ratio of iron oxide and combustibles, the firing atmosphere, and the like are strictly determined. However, not limited to this publication,
The conditions for forming a liquid phase or a glass phase, which are conditions, have not been sufficiently studied, and there are many unclear points. This can be imagined partly because the chemical composition of the raw materials is wide and the production conditions are greatly different in each case.

Further, even if a liquid phase or a glass phase is formed, it may cause fusion of particles. In general, foamable ceramics have a narrow foaming temperature range at which foaming can be performed, and advanced techniques are required for firing.

[Problems to be Solved by the Invention] As described above, foamed ceramics made of FA are not industrially and stably produced because of insufficient conditions for producing a liquid phase or a glass phase. Because the elucidation has not been clarified, the necessary conditions for foaming are unknown, there is a possibility that fusion of the foamed particles may occur, and an advanced firing technique is required. Accordingly, an object of the present invention is to provide an industrial production method of high performance foamed ceramics and to effectively utilize industrial waste such as FA.

[Means for Solving the Problems] The present inventors have made intensive studies on an industrial production method of foamed ceramics using industrial waste such as FA, which is unlikely to be depleted, as a main raw material. What is necessary is to use a raw material containing magnesium and control the amount of magnesium in the final product to obtain a foamed ceramic stably.Furthermore, by dispersing in a medium of a limited component, the particles are fused. Can be prevented.

That is, the object of the present invention is to provide (1) a powder containing at least coal ash, a powder containing at least 5 wt% of a magnesium compound in terms of magnesium oxide, and a powder having plasticity.
Using the kind, the composition of the product finally obtained is ₃ to 10 wt% as MgO, _{2 to} 16 wt% as Fe ₂ O ₃ , 10 to 25 wt% as Al ₂ O _{3 in} terms of oxide,
The first step of mixing 50 to 80 wt% as SiO ₂ , the obtained powder mixture is reduced in diameter from 0.1 mm to 10 mm.
mm, then from 1100 ° C to 130
A method for producing a ceramic foam comprising a third step of firing and foaming at 0 ° C.

(2) The method for producing a ceramic foam according to the above (1), wherein in the third step, firing is performed using a medium during firing. (3) The method for producing a ceramic foam according to the above (1) or (2), wherein in the third step, a fluidized bed firing furnace using a fluidized medium is used. (4) The method for producing a ceramic foam according to the above (2) to (3), wherein α-alumina is used as a medium used in the third step.

(5) The ceramic foam according to (1) to (4), wherein pulp sludge and / or pulp sludge incinerated ash is used as a powder containing a magnesium compound in an amount of 5 wt% or more in terms of magnesium oxide. Manufacturing method. (6) Magnesium compound is converted to magnesium oxide by 5
The method for producing a ceramic foam according to any one of (1) to (4), wherein peridotite crushed stone waste is used as the powder containing not less than wt%.

(7) From the above (1), wherein pulp sludge and / or incinerated pulp sludge ash and peridotite debris are simultaneously used as powder containing a magnesium compound in an amount of 5 wt% or more in terms of magnesium oxide. 4) The method for producing a ceramic foam according to the above. (8) The method for producing a ceramic foam according to any one of (1) to (7), wherein a dewatered cake from road excavation soil is used as the plastic powder. (9) The method for producing a ceramic foam according to the above (1) to (7), wherein cement is used instead of the powder having plasticity. Is achieved by

[Embodiment of the Invention] In the method for producing foamed ceramics according to the present invention, the amount of magnesium is controlled to stably foam and expand the ceramics, and the ceramics are sintered in the presence of a medium to fuse the particles. Prevention of adhesion and baking in a fluidized bed enabled a baking temperature distribution to be small and baking with a low defective rate. It is also possible to use various kinds of wastes that are finally disposed as raw materials. The absolute specific gravity of the foamed ceramic thus obtained is about 0.3 to 1.2, and is higher in strength than conventional products such as foamed pearlite. This foamed ceramic can be widely used as aggregate for concrete, artificial soil, soil for hydroponic cultivation, and filler for interior materials.

This will be described in detail below. The FA used in the present invention is composed of 50 wt% to 80 wt% of SiO ₂ , Al
₂ O ₃ from 10 wt% to 25 wt%, Fe ₂ O ₃ 2 w
It is desirable that the content be from t% to 16 wt%. If the chemical component is in this range, ignition loss, fineness by the Blaine method, and the like do not pose any particular problems as long as it is within the range of normal FA. The chemical components described in the present invention are obtained by converting each element determined by X-ray fluorescence analysis using a bead method into oxides, and are hereinafter referred to as% by weight unless otherwise specified.

The powder containing the magnesium compound is MgO
5% or more, preferably 10% or more must be contained in conversion. Normally, FA contains only about 1% of magnesium, and the final product MgO
In order to set the required ratio to 3 to 10%, it is desirable that the content be 5% or more.

As a powder containing magnesium, dolomite, peridotite, pyroxene, amphibolite, mica, serpentinite, sepiolite, talc, kieselite (MgSO ₄ .H
₂ O), Poriharitto _{(2CaSO 4} · MgSO 4 · K
₂ SO ₄ .2H ₂ O), Shane (K ₂ SO ₄ .M)
gSO ₄ · _6H 2 O), magnesite (MgCO _3),
Brucite (Mg (OH) ₂ ), Carnallite (Mg
Cl ₂ · KCl · 6H ₂ O), spinel (MgO · Al
Natural raw materials such as ₂ O ₃ ) and seawater magnesia, and magnesia clinker and dolomite clinker obtained by calcining them, and further, bittern (MgCl ₂ .6H
₂ 0), magnesia (MgO), basic magnesium carbonate _{(3MgCO 3 · Mg (OH)} 2 · 3H 2 O), industrial materials such as magnesium sulfate _(MgSO 4 · _7H 2 O) are exemplified.

However, even if it is not high in purity and price as described above, if it is contained at 5% or more in terms of MgO,
What is discarded as waste is sufficient. For example, pulp sludge generated in the recycling of waste paper, incinerated ash of pulp sludge, and crushed stones such as dolomite and peridotite may be used.

The powder having plasticity is used as a binder when molding the raw material of the present invention, such as a powder containing FA and a magnesium compound.
Smectite such as talc, montmorillonite, saponite, permiculite, mica, illite, chlorite, kaolinite, halloysite, attapulgite,
Clays such as allophane, starch, corn starch,
Animal and vegetable oils such as dextrin, alginic acid, sodium alginate, gum arabic, gum tragacanth, gatch gum, casein, casein soda, dextrose, gelatin, impure gelatin such as glue, flour, soy glue, peptone, molasses, shellac, soybean oil, and tallow , Liquid paraffin, carnauba wax, carbowax, and other natural products, Na-carboxymethylcellulose, methylcellulose, methylethylcellulose, cellulose acetate, sodium ligninsulfonate, calcium ligninsulfonate, Na-carboxymethyl starch, hydroxyethyl starch, starch phosphate Semi-synthetic products such as ester soda, hydroxypropylcellulose, hydroxypropylmethylcellulose, ethylcellulose, acetylcellulose, ester gum, etc. Synthesis of alcohol, polyvinyl methyl ether, polyacrylamide, sodium polyacrylate, polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, vinylpyrrolidone-vinyl acetate copolymer, tannic acid, urea, polyvinyl acetate, phenol resin, etc. Goods are illustrated.

However, inexpensive industrial materials, by-products, wastes, and the like are sufficient as long as they have the moldability that is the purpose of use of the plastic powder, even if they are not expensive substances as exemplified. Debris cake from road excavation soil,
Cement is awarded. What is road debris dewatered cake?
It is a silt with a particle size of 100 μm or less and a clay component separated from the subgrade soil and the subgrade soil excavated during road construction.

For example, in the case of Sapporo City, when renovating an existing pavement, in principle, layered excavation in which the excavation is divided into a subgrade and a subgrade is performed. Washed, crushed stone, sand and particle size 100
It is separated into dehydrated cakes of less than μm and reused. Dewatered cake from excavated soil contains about 30% moisture at the time of disposal, but may be dried during storage.

The excavated soil dewatered cake thus obtained is
The chemical composition and particle size are stable throughout the year.
O ₂ to about 60%, _Al 2 _{O 3} about 15%, _Fe 2 _{O 3} about 5
%, Average diameter of about 17 μm determined by laser diffraction method.
Looking at the mineral composition, it contains quartz and feldspar. Although the existence of clay minerals cannot be stated, the excavated soil dewatered cake is plastic. The cement is not particularly limited as long as it is commercially available. The amount used is 3 to 10 out of 100 parts by weight of the raw material.
Parts by weight, preferably 5 to 7 parts by weight.

In the first step, at least three kinds of powders containing FA, a magnesium compound and a powder having plasticity are used, and if necessary, other raw materials are added. Is oxide equivalent, MgO
3 to 10 wt%, preferably 5 to 8 wt%, Fe
₂ to 16 wt% as ₂ O ₃ , preferably 5 to 10 wt%
%, 10 to 25 wt% as Al ₂ O ₃ , preferably 1%
5~20wt%, 50~80wt% as SiO _2, preferably formulated so as to be 60~70wt%.

One of the objects of the present invention is to use FA as a main raw material. From the experience of the present inventors, it has been recognized that the three elements of silica, aluminum, and iron are the main components of FA, and that the ratio of the three elements rarely greatly deviates from the above range. In other words, the present invention has clarified the conditions for stably foaming with a composition close to FA. One of the conditions is 3 to 10 wt% of magnesium as MgO.
%.

There are various foaming conditions at compositions far away from the FA composition, but they are not the object of the present invention. The present invention
Since the product is fired at a high temperature in a later step, the product has almost no flammable components and moisture, and the target raw material usually contains almost no elements that can be volatilized during firing. The composition of the obtained product can be estimated from the components and the mixing ratio of the raw materials.

If the content of MgO is 3% or less, no glass component is formed and no foaming occurs. On the other hand, if the content is 10% or more, the melting is excessively advanced during the firing, and even if a gas is generated, the gas escapes immediately, so that a foam is not formed. If the content of Fe ₂ O ₃ is 2% or less, it does not foam, and if it exceeds 16%, it melts too much and does not foam. Also, A
also l ₂ O ₃ is out of the 10~25Wt%, SiO ₂ is also out of the 50~80wt%, does not foam.

The blended raw materials are then granulated in a second step. At this time, water may be added as needed. Granulation may be a conventional method, such as tumbling granulation, fluidized bed granulation, stirring granulation, crushing granulation, compression molding, extrusion molding, or a combination of these methods. It is not limited to these methods.

The particle size to be granulated is from 0.1 mm to 10 mm
Must be. In the case of the chemical composition of the present invention, if the particle diameter before foaming is 0.1 mm or less, it does not expand sufficiently,
If it exceeds 0 mm, it is too large for concrete aggregate, artificial soil, hydroponic soil, and interior material filler, which are the main uses of foamed ceramics, and it is difficult to form when performing fluidized bed firing using a fluid medium. It is not preferable because the granulated particles segregate in the furnace.

The particles thus granulated are then fired. If necessary, it may be dried before firing. The firing temperature is preferably from 1100 ° C to 1300 ° C. In the present invention,
The gas generated when the particle surface is vitrified is oxygen generated when trivalent iron oxide is reduced to divalent iron oxide, or generated oxygen gas and a small amount of remaining combustibles. It is estimated that it will be carbon dioxide and water produced by the reaction. The temperature at which trivalent iron is reduced varies depending on the oxygen partial pressure of the atmosphere and the like, but is usually 1100 ° C. to 1300 ° C. In the case of the present invention, the particles do not foam at a temperature of 1100 ° C. or less, and the foamed particles melt at a temperature exceeding 1300 ° C., which is not preferable.

The heating rate is not particularly problematic in terms of the degree of foaming, and is determined by the performance of the firing furnace used. The maximum temperature holding time varies depending on the particle diameter because the temperature needs to rise to the inside of the particles, but it is 3 minutes or more, preferably 5 to 30 minutes for particles having a diameter of about 1 mm.

When firing, it is necessary to pay attention to the fusion of the particles. Part of the inventive step lies in preventing fusion. The specific method of preventing fusion provided by the present invention is to fire with securing the distance between the particles, fire the particles in a medium, fire the particles in a fluidized bed using a fluidized medium,
It is. As a method of securing the distance between the first particles, for example, a method of spreading particles on a grate can be exemplified. This method can be immediately applied to a batch type firing furnace or a tunnel furnace, and does not require special equipment. However, since particles cannot be arranged in the longitudinal direction inside the furnace, the firing amount per unit furnace volume is low. The second method has improved that point.

That is, the particles obtained by granulating the foamed ceramics raw material and the medium powder are mixed, stuffed into pods, etc.
Alternatively, it is a method of firing in a tunnel furnace. By using this method, a large amount of products can be obtained by one firing because the inside of the furnace can be effectively used. At this time, it is preferable to select a material that does not react with the foamed ceramic as the medium. Due to its price, availability, and high thermal conductivity, α-
Alumina is awarded. The particle size of the medium is desirably 1/10 or less of the granulated foam ceramics. The disadvantage of this approach is that the medium carries away thermal energy, resulting in poor energy efficiency. The third method is a further improvement.

This is a method of firing foamed ceramics in a fluidized bed using α-alumina as a fluidized medium. By extracting the foamed ceramics and the fluidized medium from the fluidized bed, separating the fluidized medium, and returning the fluidized fluid to the fluidized bed again with the foamed ceramics granulated particles, it became possible to recover most of the energy carried away by the medium. In addition, the fluidization speed could be reduced by using a fluid medium having a small particle size. The thus obtained foamed ceramics is cooled and, if necessary, separated by specific gravity and particle size to obtain a product. Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to only these examples.

Examples Example 1 0.16% of MgO, 19.3% of Al ₂ O ₃ , SiO ₂ 6
7.3%, Fe ₂ O ₃ 2.83%, LOI 8.38%,
50 parts by weight of fly ash A having a specific surface area of 5730 cm ² / g, 0.98% of MgO, and Al ₂ O ₃ 19.
0%, SiO ₂ 55.2%, Fe ₂ O ₃ 15.6%, L
OI 2.21%, Blaine specific surface area 3960 cm ² / g
50 parts by weight of fly ash B, 10 parts by weight of reagent-grade magnesium hydroxide, 3.04% of MgO, Al ₂ O
₃ 13.4%, SiO ₂ 68.3%, Fe ₂ O ₃ 2.2
3 parts by weight of bentonite of 8% and 4.65% of LOI were sufficiently mixed using a crusher, water was added, and the mixture was stored in a sealed polyethylene bag for 24 hours.

This mixture was granulated into a sphere having a diameter of about 8 mm. The granulate was then dried at room temperature for 24 hours and placed on a ceramic fiber board at a sufficient distance. The ceramic fiber board and the granulated material were placed in an electric furnace, and fired under the conditions of a maximum firing temperature of 1200 ° C, a heating time from room temperature to 1200 ° C for 1 hour, a holding time at the maximum temperature of 30 minutes, and a natural cooling. . The obtained foamed ceramic is
When the absolute dry gravity and the water absorption for 24 hours were measured in accordance with IS A1134, the absolute dry gravity was 0.53 and the water absorption for 24 hours was 25.3%. The chemical composition of the foamed ceramic is 7.6% of MgO, 18.7% of Al ₂ O ₃ , and SiO ₂
60.6%, Fe ₂ O ₃ 8.9%, the particles were reddish-brown, and had such strength that they could not be grasped strongly.

Comparative Examples 1 and 2 Comparative Examples 1 and 2 were obtained by changing the maximum firing temperature of Example 1 to 1050 ° C. and Comparative Example 1 and 1350 ° C. Comparative Example 1 was an unbaked material having an absolute dry specific gravity of 1.93 and a water absorption of 45.3%, and Comparative Example 2 was a molten glassy material having an absolute dry specific gravity of 2.24 and a water absorption of 0%.

Example 2 The same operation as in Example 1 was carried out except that 10 parts by weight of the reagent primary magnesium hydroxide used in Example 1 was changed to 4 parts by weight. The obtained foamed ceramic has a reddish-brown color and has a strength that cannot be grasped strongly.
The chemical composition is MgO 3.6%, Al ₂ O ₃ 19.5%,
63.2% of SiO ₂ , 9.3% of Fe ₂ O ₃ , absolute specific gravity of 0.72, and a water absorption of 19.3% for 24 hours.

Example 3 The same operation as in Example 1 was carried out except that 10 parts by weight of the reagent primary magnesium hydroxide used in Example 1 was changed to 13 parts by weight. The obtained foamed ceramic has a reddish-brown color, has a strength that cannot be grasped strongly, and has a chemical composition of 9.5% of MgO and 18.3 of Al ₂ O _3.
%, SiO ₂ 59.3%, Fe ₂ O ₃ 8.7%, absolute dry specific gravity 0.40, and a water absorption of 35.3% for 24 hours.

Comparative Examples 3 and 4 Comparative Examples 3 and 4 were obtained by performing exactly the same operation as in Example 1 except that 10 parts by weight of the reagent primary magnesium hydroxide used in Example 1 was not used at all. 1
Comparative Example 4 was performed in the same manner as in Example 1 except that 10 parts by weight of the primary magnesium hydroxide used in Example 1 was changed to 20 parts by weight. Looking at the physical properties of Comparative Example 3, the MgO content was 0.7%, the absolute specific gravity was 1.54,
Foaming was insufficient at a water absorption of 30.6% for 4 hours. Looking at the physical properties of Comparative Example 4, it was a glassy substance which was melted at an MgO content of 13.6% and an absolute dry density of 2.11.

Example 4 The same operation as in Example 1 was carried out except that fly ash A used in Example 1 was changed from 50 parts by weight to 90 parts by weight, and fly ash B was changed from 50 parts by weight to 10 parts by weight. Was. The obtained foamed ceramic has a reddish-brown color, has a strength that cannot be grasped strongly, and is composed of Fe ₂ O ₃
The content was 4.1%, the absolute dry gravity was 0.93, and the water absorption in 24 hours was 23.5%.

Example 5 The same operation as in Example 1 was performed except that fly ash A used in Example 1 was changed from 50 parts by weight to 20 parts by weight, and fly ash B was changed from 50 parts by weight to 80 parts by weight. Was. The resulting foamed ceramic has a reddish brown, there is not casual also grab strong intensity, Fe ₂ O
₃ content 12.4%, specific gravity of absolute dryness 0.87, water absorption rate for 24 hours 18.5%.

Comparative Examples 5 to 6 Fly ash B50 as a raw material used in Example 1
The raw materials used in Comparative Example 5 and Example 1 were obtained by performing exactly the same operation as in Example 1 except that 8 parts by weight of reagent grade Al ₂ O _{3 and} 30 parts by weight of reagent grade silicon dioxide were used instead of parts by weight. Comparative Example 6 was performed in the same manner as in Example 1 except that 15 parts by weight of reagent-grade iron oxide (III) was further added and granulation was performed.

Looking at the physical properties of Comparative Example 5, the chemical composition, Mg
O7.9%, Al ₂ O ₃ 19.2%, SiO ₂ 69.9
%, Fe ₂ O ₃ 1.6%, absolute dry specific gravity 1.53, and water absorption in 24 hours were 29.3%. Looking at the physical properties of Comparative Example 6, the chemical composition, MgO 6.6%, Al ₂ O ₃ 16.
4%, 53.0% of SiO ₂ , 20.3% of Fe ₂ O ₃ , specific gravity of absolutely dry of 2.55, and a molten glassy substance.

Example 6 100 parts by weight of fly ash B used in Example 1, a chemical composition of MgO 11.3%, Al ₂ O ₃ 19.
0%, SiO ₂ 53.7%, Fe ₂ O ₃ 1.54%, L
4.57% OI, 25 parts by weight of pulp sludge incineration ash discharged from a paper mill, and a chemical composition of MgO 2.03
_{%, Al 2 O 3 17.1%} , SiO 2 59.9%, Fe
10 parts by weight of a dried product of dewatered cake of road excavated soil of 7.25% of ₂ O ₃ and 7.79% of LOI, and 1 part by weight of diethylene glycol used for the purpose of preventing grid formation were mixed for 24 hours using a pot mill.

Water was added to the mixed powder, stored for 24 hours in a sealed polyethylene bag, and then granulated into a spherical shape having a diameter of about 8 mm. Next, the granulated product was dried using a dryer at 105 ° C. for 24 hours and placed on a ceramic fiber board at a sufficient distance. Put the ceramic fiber board and the granulated material in an electric furnace and fire at a maximum temperature of 1200 ° C.
The temperature was raised from room temperature to 1200 ° C. for 1 hour, the holding time at the highest temperature was 30 minutes, and cooling was performed under natural cooling conditions.
The foamed ceramic thus obtained has a reddish-brown color and has a strength that cannot be grasped strongly.
_{MgO3.1%, Al 2 O 3 19.6} %, SiO 2 5
7.3%, Fe ₂ O ₃ 12.8%, absolute dry specific gravity 0.83,
The water absorption in 24 hours was 20.4%.

Example 7 Instead of 25 parts by weight of pulp sludge incineration ash used in Example 6, the chemical composition was 47.2% MgO,
₂ O ₃ 0.75%, SiO ₂ 40.0%, Fe ₂ O
₃ Except for changing the amount of waste olivine discharged from the peridotite mine to 8.24% and LOI 1.69%, to 10 parts by weight, and changing the usage of the dehydrated cake from road excavation soil from 10 parts by weight to 100 parts by weight Performed exactly the same operation as in Example 6. The thus obtained foamed ceramic has a reddish brown, there is a strong grab informal neither strength, chemical _{composition, MgO5.0%, Al 2 O 3} 17.8%, SiO 2
59.4%, Fe ₂ O ₃ 11.8%, absolute dry specific gravity 0.9
The water absorption for 5 and 24 hours was 27.5%.

Example 8 A commercial cement (chemical composition M) was used in place of 10 parts by weight of the dried soil dewatered cake from the road excavation soil used in Example 6.
gO 1.61%, Al ₂ O ₃ 5.20%, SiO ₂ 2
_{2.67%, Fe 2 O 3 3.08} %, LOI1.23
%, 36.8 cm ² / g of Blaine specific surface area), and mixed using a pot mill in the same manner as in Example 6.
Water was added to the obtained mixed powder, and the mixture was granulated into a sphere having a diameter of 8 mm. The granulated product was dried at room temperature for 24 hours and then fired in the same manner as in Example 6. The foamed ceramic thus obtained has a reddish-brown color, has a strength that cannot be grasped strongly, and when viewed from the chemical composition, it is found that MgO 3.1% and Al ₂ O ₃
19.1%, SiO ₂ 55.3%, Fe ₂ O ₃ 12.8
%, Absolute specific gravity 0.70, water absorption rate for 24 hours is 17.3%
Met.

Example 9 The raw material used in Example 6 was further added with a chemical composition of Mg
_{O0.63%, Al 2 O 3 5.17} %, SiO 2 60.
The same operation as in Example 6 was carried out except that 25 parts by weight of dust dust discharged from a foundry having 26%, Fe ₂ O _{3 of} 3.07% and LOI of 28.0% were added. The foamed ceramic thus obtained has a reddish-brown color, has a strength that cannot be grasped strongly, and has 2.8% of MgO and Al ₂ O ₃ 1
8.1%, SiO ₂ 60.7%, Fe ₂ O ₃ 11.8
%, Absolute dry specific gravity 0.52, water absorption rate for 24 hours is 30.3%
Met.

Example 10 The same operation as in Example 9 was carried out except that the amount of the dehydrated cake from the excavated soil from the road excavation used in Example 9 was increased from 10 parts by weight to 100 parts by weight. The foamed ceramic thus obtained has a reddish-brown color, has a strength that cannot be grasped strongly, and contains 2.6% of MgO, 18.3% of Al ₂ O ₃ , and
62.2% of O ₂ , 10.4% of Fe ₂ O ₃ , specific gravity of absolute dryness of 0.
The water absorption in 88 hours and 24 hours was 15.3%.

Example 11 To 10 parts by weight of the granulated product having a diameter of 8 mm produced in Example 9, 100 parts by weight of coarse alumina manufactured by Sumitomo Chemical Co., Ltd. was used as a medium and thoroughly mixed. The mixture was placed in a silicon carbide sagger and fired in an electric furnace. The firing conditions are a firing maximum temperature of 1200 ° C., a heating time from room temperature to 1200 ° C. for 3 hours, a holding time at the maximum temperature of 2 hours, and natural cooling. 10 ceramics fired in this way
Using a standard 0-mesh sieve, the powder was separated into alumina powder and foamed ceramics. The foamed ceramic thus obtained has a reddish-brown color, has a strength that cannot be grasped strongly, and has a specific gravity of 0.61 and a water absorption of 22.3 for 24 hours.
%Met.

Comparative Example 9 Only the granules having a diameter of 8 mm produced in Example 9 were
It was packed in a silicon carbide sagger and fired in the same manner as in Example 11. Looking at the container after the completion of firing, the container and the foamed ceramic were fused and the foamed ceramic was foamed, but the granulated particles were integrated.

Comparative Example 10 Example 1 was repeated except that the alumina medium used in Example 11 was replaced with No. 7 silica sand manufactured by Tohoku Silica Sand Co., Ltd.
A foam ceramics was produced in exactly the same manner as in Example 1. In the obtained foamed ceramics, the medium and the foamed ceramics reacted and fused to each other, and were integrated.

Example 12 100 parts by weight of fly ash B used in Example 9, 10 parts by weight of dehydrated cake from road excavation soil, 25 parts by weight of pulp sludge incineration ash, 25 parts by weight of foundry dust, and the prevention of grid formation 1 part by weight of diethylene glycol used for this purpose was charged into a pot mill and mixed for 24 hours. While adding water to this mixed powder, granulation was performed using an Omnimixer OM-5 model manufactured by Chiyoda Giken Kogyo Co., Ltd. Particles having a diameter of 2 mm to 4 mm were selected from the obtained granules using a standard sieve. The granulated particles are heated at 105 ° C.
Drying was performed for 24 hours. The alumina powder 10 used in Example 11 was used as a fluid medium for 10 parts by weight of the granulated particles.
0 parts by weight were added and mixed well.

As shown in FIG. 1, the outer diameter of the core tube is 70φ.
Attach a fluidized bed using an alumina core with an inner diameter of 60φ to a vertical double-tube siliconit electric furnace, flow air so that the flow rate in the fluidized bed is 5 liters per minute, and charge alumina powder to be a bed. Then, the electric furnace was heated. 120 fluidized beds
When the temperature reached 0 ° C., a mixture of the granulated particles and alumina was charged and calcined for 15 minutes. The temperature of the fluidized bed was lowered to room temperature over 3 hours after the completion of the firing. The fired ceramics were separated into alumina powder and foamed ceramics using a standard 100-mesh sieve. The foamed ceramic thus obtained had a reddish-brown color, had a strength that could not be grasped strongly, had an absolute dry specific gravity of 0.56, and had a water absorption of 29.3% for 24 hours.

[Effects of the Invention] As described above, the present invention makes it possible to stably obtain industrially useful foamed ceramics and to reuse various wastes finally disposed as raw materials. Became clear.

[Brief description of the drawings]

FIG. 1 is a fluidized bed firing furnace used in Example 12.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vertical double tube silicon-nit furnace 2 Alumina core tube 3 Fluidized bed 4 Alumina ball 5 Alumina honeycomb 6 Sleeve 7 Rushing ring

Claims (9)

(57) [Claims] 1. A powder containing at least 5 wt% of coal ash and a magnesium compound in terms of magnesium oxide,
And three types of powder having plasticity, the composition of the finally obtained product is calculated as oxide, and is 3 to 10 as MgO.
wt%, ₂ to 16 wt% as Fe ₂ O ₃ , Al ₂ O ₃
10~25wt% as, 50~80w as SiO ₂
The first step of compounding the powder mixture so as to have a concentration of 0.1%, the second step of granulating the obtained powder mixture to a diameter of 0.1 mm to 10 mm, and the third step of firing and foaming at 1100 ° C. to 1300 ° C. How to make the body. 2. The method for producing a ceramic foam according to claim 1, wherein in the third step, firing is performed using a medium during firing. 3. The method for producing a ceramic foam according to claim 1, wherein, in the third step, a fluidized-bed firing furnace using a fluidized medium is used. 4. The method for producing a ceramic foam according to claim 2, wherein α-alumina is used as a medium used in the third step. 5. The ceramic according to claim 1, wherein pulp sludge and / or pulp sludge incineration ash is used as a powder containing a magnesium compound in an amount of 5 wt% or more in terms of magnesium oxide. A method for producing a foam. 6. A method for producing a ceramic foam according to claim 1, wherein peridotite crushed stone waste is used as a powder containing a magnesium compound in an amount of 5 wt% or more in terms of magnesium oxide. Method. 7. A pulp sludge and / or incinerated pulp sludge ash and peridotite crushed stone as a powder containing at least 5 wt% of a magnesium compound in terms of magnesium oxide. 5. The method for producing a ceramic foam according to items 4 to 4. 8. The method for producing a ceramic foam according to claim 1, wherein dewatered cake from road excavation soil is used as the powder having plasticity. 9. The method for producing a ceramic foam according to claim 1, wherein cement is used in place of the powder having plasticity.