JPH0977542A - Production of hollow foamed body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily produce a high strength hollow foamed body using a coal ash as a main raw material, low in specific gravity, low in water absorption and having a dense foamed layer in the outside part and voids in the inside part. SOLUTION: A powdery raw material prepared by blending 80-120 pts.wt. active siliceous powder to 100 pts.wt. coal ash containing 20-40wt.% unburned carbon is molded and granulated and the granulated material is fired at the foaming temp. of 1150-1350 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a coal ash to form a hollow foam having a low specific gravity and a low water absorption, which has a low specific gravity and a low water absorption and has a dense foam layer on the outside and a hollow interior. The present invention relates to a method for industrially easy production.

[0002]

2. Description of the Related Art In recent years, in order to save energy, save resources, save labor, and improve earthquake resistance, structures such as buildings are required to be made lighter and have heat insulation materials such as wall materials, interior materials and structural materials. It is being advanced, and a large amount of hollow foam is used as an artificial lightweight aggregate for lightweight concrete. The characteristics required for the artificial lightweight aggregate are that it is lightweight, has a small water absorption, and can be manufactured industrially easily and inexpensively. Further, in an absorption tower of a chemical plant or the like, a large amount of magnetic Raschig rings, fillers such as balls are used in order to improve absorption efficiency. The characteristics required of the filler are such that it does not corrode, is lightweight, has a small water absorption amount, and is easy to handle.

Conventional hollow foams include shale, silica sand, volcanic rock,
Using various materials such as alumina, glass, shirasu, carbon, fly Ayu and synthetic resin, hollow bodies with a thickness of the outer shell of several μ and a particle size of 1 to 15,000 μ are made from liquid, melt or solution state. ing. Further, although the heat insulation property is somewhat inferior, there is an advantage that the weight reduction rate is increased, and further, coarse particles are used for the purpose of increasing the packing density to reduce the heat shrinkage property and enhancing the soundproofing property. Coarse-grained hollow bodies are not used as aggregates for structural lightweight concrete because of their high price, reduced strength due to thin outer shells, and poor foamable volcanic rock resources. In recent years, there has been a demand for the development of artificial lightweight aggregates that replace expanded shale foam, including the redevelopment of unused resources and the use of industrial waste. Combustion of coal in combustion furnaces of thermal power plants and various factories Granules coal ash that is discharged in large quantities during
A technique for producing a foam by firing is drawing attention and many proposals have been made.

However, the fact is that foams containing coal ash as a main raw material have not been commercialized yet. The main reason is that the conventionally proposed method is reasonably suitable for small-scale production such as production on a laboratory scale. As a result, the granulated product collapsed and a foam with the desired shape could not be obtained, only those with low strength and high water absorption could be obtained, and there were large variations in quality. This is probably due to higher costs and quality problems.

Regarding the foam made mainly of coal ash,
For example, Japanese Patent Publication No. 38-25820 and Japanese Patent Publication No. 40-1
6270, JP-B-54-64680, JP-A-59-39757, JP-B-6-11659, JP-A-3-88749, JP-A-3-2751.
34, JP-A-3-275134, JP-A-5
No. 170567, JP-A-6-263495 and JP-A-7-41343 have been proposed, but a hollow foam having a low specific gravity and a low water absorption having a dense foam layer outside and a hollow inside I can't find any suggestions for the body.

The method proposed in Japanese Examined Patent Publication No. 6-11659 discloses a coal ash having a standard mesh sieve 297 μm residue of 1% by weight or less, and a hydraulic property of 1 to 20 parts by weight based on 100 parts by weight of the coal ash. After curing a granulated product obtained by granulating a powdered raw material containing the material in the presence of water for 20 hours or more, 1000
According to this method, it is possible to produce an artificial lightweight aggregate having a low water absorption rate and a high strength on an industrial scale by firing at a temperature of up to 1500 ° C. There is no disclosure of hollow foam having low specific gravity and low water absorption, which is hollow.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a method for easily producing, on an industrial scale, a hollow foam mainly made of coal ash, which has a hollow inside and has a low specific gravity and low water absorption. This is an issue.

[0008]

DISCLOSURE OF THE INVENTION According to the present invention, 100 to parts by weight of coal ash having an unburned carbon content of 20 to 40% by weight is blended with 80 to 120 parts by weight of active siliceous powder to granulate a powder raw material. After molding, the granulated product is fired at a foaming temperature of 1150 to 1350 ° C to obtain a hollow foamed product having a dense foamed layer on the outside and a hollow inside Concerning the law. Further, the present invention is based on 100 parts by weight of coal ash having an unburned carbon content of 1 to 15% by weight and activated siliceous powder
~ 120 parts by weight and 5 to 39 parts by weight of carbon were granulated, and then the granulated product was granulated and molded.
The present invention relates to a method for producing a hollow foam, which comprises firing at a foaming temperature of C to obtain a hollow foam having a dense foam layer on the outside and a hollow interior.

In the present invention, as coal ash, coal ash generated when coal is burned in a combustion furnace of a thermal power plant or various factories, such as fly ash, cinder ash, bottom ash and clinker ash, is required. It is used after subjecting it to classification and the like. The unburned carbon content in the coal ash is preferably 20 to 40% by weight, preferably 20 to 30% by weight, but when the unburned carbon content in the coal ash is as small as 1 to 15% by weight, The carbon content is adjusted by adding 5 to 39 parts by weight of carbon to 100 parts by weight of coal ash. The carbon to be blended is not particularly limited as long as it burns at the firing temperature, but normally coal powder, oil coke powder or the like is used. If the amount of unburned carbon in the granulated product is too small, the whole fired product becomes a foam having fine, uniform-sized closed-type spherical pores, and a dense foam layer on the outside and a hollow inside. A hollow foam having a low specific gravity and a low water absorption cannot be obtained, and if it is too large, it is not possible to obtain a desired hollow body because it is pulverized during firing and the cavities are cracked.

The coal ash used preferably has a Blaine specific surface area of 2000 cm ² / g or more, more preferably 3000 cm ² / g or more, 3000-14000 c.
Those of m ² / g are particularly suitable. If the Blaine specific surface area is less than 2000 cm ² / g, granulation molding becomes difficult, and if it is too large, a special crushing device is required, which is not economical.

In the present invention, the active siliceous powder is S
The content of iO ₂ is 60% by weight or more, preferably 70% by weight
Thus, those containing 70% by weight or more of glass are suitable. Activated siliceous powder usually contains Al ₂ O ₃ component, CaO component, alkali component and the like in addition to SiO ₂ component. If the content of the SiO ₂ component of the active siliceous powder is too small, in other words, if the content of the Al ₂ O ₃ component, CaO component, alkali component, etc. is too large, the viscosity sharply decreases during the firing process and foaming occurs. Since bubbles are easily destroyed and open pores are apt to occur due to gas escape, in order to obtain a high-strength hollow foam having a dense foam layer outside and a hollow inside,
It is preferable that the content of iO ₂ is 70% by weight or more. Further, if the amount of glassy material is small, foaming failure tends to occur. Activated siliceous powder has a Blaine specific surface area of 2000.
˜14000 cm ² / g, preferably 2000-100
It is preferable that the density is 00 cm ² / g because a uniform dense foam layer can be formed on the outside. If the value of the Blaine specific surface area is too small, granulation molding becomes difficult. Typical examples of activated siliceous powder include quartz trachyte,
Natural materials such as obsidian, pearlite and shirasu can be mentioned.

The amount of the activated siliceous powder is 80 to 120 parts by weight, preferably 90 to 1 part by weight based on 100 parts by weight of coal ash.
10 parts by weight. If the amount of activated siliceous powder is too small,
The glass layer on the surface of the external dense foam layer of the fired product becomes thin,
It is difficult for the pores to become a closed type and open pores due to gas escape, and a hollow foam having a hollow inside cannot be obtained. On the other hand, if the amount of activated siliceous powder is too large, the amount of foaming components in the coal ash decreases, so that the foamability deteriorates and the desired foam cannot be obtained.

In the present invention, a predetermined amount of coal ash and activated siliceous powder, or coal ash, activated siliceous powder and unburned carbon are granulated and formed into granules. The coal ash and the activated siliceous powder, and the coal ash, the activated siliceous powder and the unburned carbon may be mixed at the time of granulation molding or may be mixed in advance. Granulation molding is usually performed in the presence of water, but in order to obtain a high-strength hollow foam with a dense foam layer outside the fired product and a hollow interior, it is used for granulation molding. The amount of water used is preferably as small as possible, in other words, the minimum amount necessary for the granulated product to retain its own form during the firing step. Usually, it is used by appropriately selecting from the range of 3 to 10 parts by weight with respect to 100 parts by weight of the powder raw material. If the amount of water increases, the granulated product may explode during firing,
The pores tend to be open type. For the granulation and molding, for example, a pan-type granulator, a rotary cylinder granulator, a briquette machine, a compression molding machine, a tableting machine and the like are appropriately used. The size and shape of the granulated product is not particularly limited, but it is usually molded into a spherical shape, a cylindrical shape, a rugby ball shape or the like having a particle size of 1 to 50 mm. The crushing strength of the granulated product is preferably 1 kgf or more.

In the present invention, when the coal ash and the activated siliceous powder are granulated and molded, the use of a hydrophilic paste material can improve the crushing strength of the granulated product, and the use of water during granulation. Not only can the amount be reduced to prevent the granulated material from exploding during firing, but the bubbles can easily become uniform, and the amount of heat required for evaporation of water can be reduced. If the amount of the hydrophilic paste material used is too large, it may be difficult to granulate and mold it into a desired shape.
It is used in an amount of 5 parts by weight or less, preferably 0.1 to 5 parts by weight, based on parts by weight. Typical examples of the hydrophilic paste material include polyvinyl alcohol, cellulose derivative, polyacrylate, polyacrylamide, synthetic rubber latex, and epoxy polymer emulsion. Among them, polyvinyl alcohol is preferable.

In the present invention, the granulated product obtained by the granulation molding may be immediately calcined, but it is preferable to calcinate and then calcinate the granulated product to evaporate the water content in the granulated product and tighten the granulated product. It is preferable because it can be solidified, the granulated product can be prevented from exploding or open pores can be generated during firing, and a uniform dense foam layer can be easily formed outside the fired product. Curing is generally carried out at a temperature of 100 to 700 ° C. for 0.5 to 24 hours in order to evaporate and condense water and the like in the granulated product.

By firing the granulated product, the coal ash particles and siliceous particles of the granulated product are brought into a semi-molten state to bond the particles to each other, and the moisture, carbon, sulfur and other components in the granulated product react with each other. Alternatively, it is not reacted and is discharged as a gas to generate a large cavity inside the granulated product, and a dense foam layer having a closed type spherical pore of uniform size is formed on the outside thereof to form a hollow foam. That is, a viscous glass layer is generated inside the granulated product that has become a semi-molten state by firing, and the generated bubbles grow into large closed cells, and uniform and minute pores are distributed outside the bubble. A dense foam layer is formed to form a hollow foam having a low specific gravity and a low water absorption, which is hollow inside.

The firing is carried out at a temperature of 1150 to 1350 ° C. in an oxygen-containing gas atmosphere. If the firing temperature is too low, the generation of bubbles is insufficient and the granulated product does not expand sufficiently to give a hollow body with a hollow interior, while if it is too high, fusion of the granulated product will occur. The calcination temperature is preferably in the above range because it becomes a lump and causes difficulty in operating the calcination device. The firing time is usually 0.25 to 3 hours. For firing,
For example, a commonly used firing device known per se such as a rotary kiln, a shaft furnace, and a sinter grade can be used.

The hollow foam obtained by firing is 24
The hourly water absorption rate is 1% by weight or less, the pressurized water absorption rate is 50% by weight or less, the crush strength is 10 kgf or more, and the absolute dry specific gravity is 0.5 or less, usually 0.2 to 0.4. As shown in the schematic cross-sectional view of the hollow foam body, a dense foam layer 2 having a cavity 1 inside and a closed spherical pore of uniform size on the outside thereof.
Are formed. A glass layer 3 is formed on the surface of the dense foam layer. Although the details of the mechanism for obtaining such a fired product are not fully clear, it is presumed that the firing temperature, unburned carbon of coal ash, bound moisture of siliceous powder, etc. are closely related.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

EXAMPLES In each example, the absolute dry specific gravity and the 24-hour water absorption (% by weight) were measured according to JIS A 1135 "Testing method for specific gravity and water absorption of lightweight structural aggregate". In addition, the amount of pressurized water absorption (% by weight) was measured by placing the foam (calcined product) in a 10 liter autoclave and using a pressure pump to measure the amount of pressurized water absorption at 40 kgf / cm ² . The crushing strength (kgf) was measured using a precision force measuring machine manufactured by Maruhishi Scientific Machinery Co., Ltd.

Further, the chemical composition (% by weight) of the coal ash and the activated siliceous powder used in each example is shown in Table 1, and the specific gravity, the Blaine specific surface area (cm ² / g), the average particle diameter (μm) and the glass. The quality content (% by weight) is shown in Table 2. The chemical composition of quartz trachyte G and H in Table 2 is the same as that of quartz trachyte F in Table 1.

[0021]

[Table 1]

[0022]

[Table 2]

The hollowing rate (%) of the fired products in Tables 3 and 4 is obtained by measuring the volume of the fired product, cutting the fired product, and measuring the volume of the internal cavity. I asked. Hollowing ratio (%) = volume of cavity / volume of fired product × 100

Example 1 To 100 parts by weight of coal ash A and 100 parts by weight of quartz trachyte F, 6 parts by weight of water was added and mixed with a magnetic pot mill, followed by pressure molding to obtain a particle size of 1 to 1. 10mm spherical ~
An elliptic spherical granule was obtained. The crushing strength of the granulated product was 4.3 kgf. The granulated product was heated at a temperature rising rate of 20 ° C./min using an electric furnace with a temperature rising program, and 1200
Firing at 30 ° C. for 30 minutes gave a hollow foam having a hollow inside and a dense foam layer outside (indicated as hollow body in Table 3). Physical properties such as absolutely dry specific gravity, 24-hour water absorption, pressurized water absorption, and crush strength of the obtained hollow foam were measured. The results are shown in Table 3.

Examples 2 to 3 The firing temperature of Example 1 was changed from 1200 ° C to 1300 ° C (Example 2) and 1170 at a temperature rising rate of 200 ° C / min.
A hollow foam was obtained in the same manner as in Example 1 except that the temperature was changed to ° C (Example 3). Absolute dry specific gravity of the obtained hollow foam,
Physical properties such as 24-hour water absorption, pressurized water absorption, and crush strength were measured. The results are shown in Table 3.

Example 4 A hollow foam was obtained in the same manner as in Example 1 except that 100 parts by weight of coal ash A in Example 1 was changed to 100 parts by weight of coal ash B. Physical properties such as absolutely dry specific gravity, 24-hour water absorption, pressurized water absorption, and crush strength of the obtained hollow foam were measured. The results are shown in Table 3.

Example 5 100 parts by weight of coal ash A of Example 1 was changed to 100 parts by weight of coal ash C, 10 parts by weight of carbon (purity 100% conversion) was added, and the firing temperature 1200 ° C was changed to 1190 ° C ( Aside from this, a hollow foam was obtained in the same manner as in Example 1.
As the added carbon, coal powder (14.3 parts by weight) having a carbon content of 70% by weight, a Blaine specific surface area of 12000 cm ² / g and an average particle diameter of 58 μm was used. Physical properties such as absolutely dry specific gravity, 24-hour water absorption, pressurized water absorption, and crush strength of the obtained hollow foam were measured. The results are shown in Table 3.

Example 6 The same procedure as in Example 1 was carried out except that 100 parts by weight of coal ash A in Example 1 was changed to 100 parts by weight of coal ash E and 20 parts by weight of unburned carbon similar to that in Example 5 was added. A foam was obtained. Physical properties such as absolutely dry specific gravity, 24-hour water absorption, pressurized water absorption, and crush strength of the obtained hollow foam were measured. The results are shown in Table 3.

Comparative Examples 1 to 2 Except that the firing temperature of 1200 ° C. of Example 1 was changed to 1100 ° C. (Comparative Example 1) and 1400 ° C. (Comparative Example 2),
An attempt was made to manufacture a hollow foam in the same manner as in Example 1. When the firing temperature was 1100 ° C, the inside of the fired product did not become a complete cavity, but a semi-hollow body was obtained. The firing temperature is 1400 ° C
In this case, the granulated product was fused and could not be fired. Table 3 shows the results of measuring physical properties.

Comparative Example 3 A hollow foam was produced in the same manner as in Example 6 except that 20 parts by weight of unburned carbon in Example 6 was changed to 10 parts by weight and the firing temperature was changed from 1190 ° C to 1310 ° C. Tried. The fired product was a foam having no voids inside. Table 3 shows the results of measuring physical properties.

COMPARATIVE EXAMPLE 4 An attempt was made to produce a hollow foam in the same manner as in Example 6 except that 20 parts by weight of unburned carbon in Example 6 was changed to 50 parts by weight. And a hollow foam could not be obtained.

Comparative Examples 5 and 6 100 parts by weight of the quartz trachyte F of Example 1 was changed to 60 parts by weight (Comparative Example 5), 150 parts by weight and the firing temperature was changed to 1.
An attempt was made to manufacture a hollow foam in the same manner as in Example 1 except that the temperature was changed to 170 ° C (Comparative Example 6). The fired product was a foam having no voids inside. Table 3 shows the results of measuring physical properties.

[0033]

[Table 3]

Examples 7 to 8 The firing temperature of Example 1 was changed from 1200 ° C to 1210 ° C, and 100 parts by weight of quartz trachyte F was added by 100 parts by weight of obsidian I (Example 7) and 100 parts by weight of shirasu K (Example). A hollow foamed body was obtained in the same manner as in Example 1 except that the procedure was changed to 8). Absolute dry specific gravity of the obtained hollow foam, water absorption for 24 hours,
Physical properties such as water absorption under pressure and crushing strength were measured. The results are shown in Table 4.

Examples 9 to 10 100 parts by weight of the quartz trachyte F of Example 1 is replaced with pearlite J100.
A hollow foam was obtained in the same manner as in Example 1 except that the mixture was changed to parts by weight (Example 9) and a mixture of 50 parts by weight of quartz trachyte F and 50 parts by weight of obsidian I (Example 10). Absolute dry specific gravity of the obtained hollow foam, 24-hour water absorption, pressurized water absorption,
Physical properties such as crush strength were measured. The results are shown in Table 4.

Example 11 A hollow foam was prepared in the same manner as in Example 1 except that 100 parts by weight of the quartz trachyte F of Example 1 was replaced by 100 parts by weight of the quartz trachyte G having a Blaine specific surface area of 9000 cm ² / g. Obtained.
Physical properties such as absolutely dry specific gravity, 24-hour water absorption, pressurized water absorption, and crush strength of the obtained hollow foam were measured. The results are shown in Table 4.

Comparative Example 7 100 parts by weight of the quartz trachyte F of Example 1 was used as shale L100.
Production of a hollow foam was tried in the same manner as in Example 1 except that the baking temperature was changed from 1200 ° C to 1170 ° C instead of parts by weight. The fired product was a foam having no voids inside. Table 4 shows the results of measuring physical properties.

Comparative Example 8 A hollow foam was prepared in the same manner as in Example 1 except that 100 parts by weight of coal ash A in Example 1 was changed to 100 parts by weight of coal ash C and the firing temperature was changed from 1200 ° C. to 1350 ° C. Tried to manufacture. The fired product was a foam having no voids inside.
Table 4 shows the results of measuring physical properties.

Comparative Example 9 A hollow foam was produced in the same manner as in Example 1 except that 100 parts by weight of coal ash A in Example 1 was changed to 100 parts by weight of coal ash D. At times, it could not be pulverized to obtain a hollow foam.

[0040]

[Table 4]

[0041]

According to the present invention, the main raw material is coal ash,
A high-strength hollow foam having a low specific gravity and low water absorption, a dense foam layer on the outside, and a hollow interior can be easily produced on an industrial scale. In addition, the hollow foam according to the present invention has high strength, low specific gravity and low water absorption, and thus can be suitably used as an artificial lightweight aggregate and as a filler and the like because it is not corrosive and lightweight.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a hollow foam according to the present invention.

[Explanation of symbols]

 1 Cavity inside 2 Dense foam layer outside 3 Surface glass layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiko Oyama 1-12-32 Nishihonmachi, Ube City, Yamaguchi Prefecture Ube Head Office Ube Head Office

Claims (5)

[Claims] 1. A coal ash having an unburned carbon content of 20 to 40% by weight.
After granulating a powder raw material in which 80 to 120 parts by weight of activated siliceous powder is mixed with 00 parts by weight, the granulated product is 115
A method for producing a hollow foam, which comprises firing at a foaming temperature of 0 to 1350 ° C. to obtain a hollow foam having a dense foam layer outside and a hollow inside. 2. A coal ash having an unburned carbon content of 1 to 15% by weight.
After granulating a powder raw material in which 80 to 120 parts by weight of active silicic acid powder and 5 to 39 parts by weight of carbon are blended with respect to 0 part by weight, the granulated product is fired at a foaming temperature of 1150 to 1350 ° C. A method for producing a hollow foam, characterized in that a hollow foam having a dense foam layer on the outside and a hollow inside is obtained. 3. The activated siliceous powder contains 60% by weight or more of SiO ₂ and 70% by weight or more of glass, and has a Blaine specific surface area of 2000 to 14000 cm ² / g. The method for producing a hollow foam according to 1. 4. The activated siliceous powder according to claim 1, 2 or 3, which is one or more kinds of powder selected from the group consisting of obsidian, quartz trachyte, shirasu and pearlite. Hollow foam manufacturing method. 5. A hollow foam having a hollow interior has an absolute dry specific gravity of 0.
The method for producing a hollow foam according to claim 1, claim 2, claim 3 or claim 4, which has a water absorption of 5% or less and a 24-hour water absorption of 1% by weight or less.