JPH10251048A - Production of artificial fly ash aggregate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high density and high strength artificial fly ash aggregate which does not change into low density and high water absorption by rapid foaming, by mixing a specified silica-alumina-contg. fine powder into fly ash, granulating and then calcining. SOLUTION: A fly ash produced by combustion of a solid fuel is mixed with a silica alumina fine powder having <10μm average particle size, containing >=95wt.% total amt. of silica and alumina, >=23wt.% alumina and >=1,500 deg.C melting point, by 10 to 30wt.% of the final product to obtain a mixture. If necessary, a granulating assistant, clay and thickener and the like are added to the mixture, and then the mixture is humidified, granulated, and dried to obtain a pellet of calcination. The pellet is calcined at 1,100 to 1,300 deg.C. Thereby, the obtd. artificial fly ash aggregate can be produced at <=1,300 deg.C calcining temp. of the fly ash which is economical, and the obtd. aggregate shows 40MPa strength calculated as tensile strength by compressive strength test using Instron.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an artificial aggregate using fly ash, which is industrial waste, as a main raw material.

[0002]

2. Description of the Related Art Burning coal as fuel in a boiler or the like of a thermal power plant generates a large amount of fly ash as industrial waste. Fly ash generated in one year is about 4 million tons, about half of which is used effectively in the construction of cement concrete and the like, the civil engineering field, and the ceramic industry. The amount of fly ash generated is steadily increasing every year. From the standpoint of environmental conservation and effective use of resources, it is desired that the effective use of fly ash be further promoted.

[0003] Various attempts have been made to use fly ash as concrete aggregate, but very few have reached practical use. The reason is that fly ash has a large variation in chemical and physical properties, and it is not possible to produce high-density, low-water-absorption, low-strength, high-quality, stable aggregates in high yields under certain production conditions. It is in.

[0004] The cause is a foaming phenomenon that occurs during manufacturing. Japanese Patent Application No. 7-90219 discloses a technique for producing an artificial aggregate in which foaming is suppressed by baking fly ash obtained by burning and removing unburned carbonaceous materials in an atmosphere having an oxygen concentration of 5% by volume or less. I have. Although this is an effective method, it is not economical because a special device for controlling the oxygen concentration is required. Also, Japanese Patent Application No. 7-90220 discloses a method in which fly ash is fired in a neutral or inert gas atmosphere to adjust the raw material for the artificial aggregate to suppress the foaming phenomenon during firing. Again, this is not an economic method.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to make it possible to produce fly ash at an economical temperature of 1300 ° C. or lower, and to reduce the density and increase the water absorption due to a rapid foaming phenomenon even when the production control temperature is exceeded. An object of the present invention is to provide a method for producing a high-density, high-strength fly ash artificial aggregate that does not cause efficiency.

[0006]

A high-melting silica-alumina-containing fine powder is mixed with fly ash, which is a main raw material. It has been found that a method for producing a fly ash artificial aggregate in which foaming is suppressed can be obtained by granulating and baking the mixture.

The production method of the present invention is based on the above findings. According to the present invention, there is provided a method for producing an artificial aggregate having the following constitution.

(1) Fly ash and melting point 1500 °
A method for producing an artificial fly ash aggregate, comprising mixing a fine powder containing silica-alumina of C or more, granulating the mixture, and firing.

(2) An artificial fly ash characterized in that the total amount of the silica-alumina component in the silica-alumina-containing fine powder is 95% by weight or more and the alumina component content is 23% by weight or more. Aggregate manufacturing method

(3) The mixing ratio of the silica-alumina-containing fine powder in the mixture is at least 10% by weight and 30% by weight
A method for producing an artificial aggregate, characterized in that:

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the production method of the present invention, ordinary fly ash generated by burning solid fuel is used.
The silica-alumina-containing fine powder having a melting point of 1500 ° C. or more may be a high-purity product, but molding waste, waste of sintered bodies, natural materials such as clay, waste of porcelain, and the like are also used in the oxide ceramic manufacturing process. be able to. Silica and alumina may be used as a mixture or may be contained in the form of aluminosilicate.

The silica-alumina-containing fine powder preferably has an average particle diameter of 10 μm or less. 10 in average particle size
If it is more than μm, the reaction speed becomes slow, the sintering temperature is delayed, and the expected effect may be reduced.

As a means for obtaining the fine powder, a usual pulverization method or dispersion method is used. The mixing means with fly ash may be a usual mixing means. The mixing ratio is desirably 10% by weight or more and 30% by weight or less.

The raw material whose particle size has been adjusted as described above may be further pulverized and mixed as necessary in order to secure the strength of the granulated material, or a small amount of clay,
A thickener or the like may be added. Then humidification, granulation,
Through a drying step, pellets for sintering are obtained. There is no particular limitation on the granulation method, but granulation by a punch pelletizer or an extrusion molding machine is desirable.

By heating and holding the thus obtained molded body at a temperature of 1100 ° C. or more and 1300 ° C. or less, a high-density high-strength fly ash artificial aggregate having a small variation in specific gravity can be obtained. Since the individual vitreous particles that constitute fly ash contain unburned carbonaceous material that becomes a foaming source during high-temperature heating, foaming at an excessively high temperature should be avoided in order to burn aggregate having a stable specific gravity. There must be. By mixing the above silica-alumina fine powder, 110
By heating and holding at a temperature of 0 ° C. or more and 1300 ° C. or less, a high-density high-strength fly ash artificial aggregate having little variation in specific gravity can be obtained.

The reason for this is not clear. Fly ash is an aggregate mainly composed of glassy particles having a spherical shape, crystal particles such as quartz and mullite, and unburned carbonaceous materials. In the case where fly ash is granulated and fired to form an aggregate, sintering of the aggregate occurs by vitrification prior to melting of quartz or mullite. Simultaneously with the melting of the vitreous, it is thought that the specific gravity of the aggregate is reduced by foaming of a very small amount of carbonaceous material trapped in the particles.

The present inventors disclose a sufficient amount of silica-alumina mixture fine powder particles in the vicinity of the vitreous particles for capturing carbonaceous material, and provide the entire vitreous inorganic material containing a foaming component. By reducing the relative amount to
We found that it was possible to control the melting temperature by changing the glassy chemical composition, reduce the effect of glass particle foaming on specific gravity reduction, widen the melting temperature range, and reduce the variation in aggregate density with respect to firing temperature changes. Was.

According to the method for producing a fly ash artificial aggregate thus obtained, the artificial aggregate can be produced at a relatively low sintering temperature in a much wider temperature range than before. Since the production control temperature is wide, it is easy to control the sintering process, and ordinary sintering equipment can be used without any special specification change.

The obtained fly ash artificial aggregate is a sintered material which can be used as a high-density and high-strength aggregate, and cannot be produced using a conventional fly ash production method. The water absorption was much smaller than that of the conventional fly ash aggregate, and the crush strength test result using Instron showed a tensile strength of 40 MPa, which was comparable to that of natural aggregate.

Examples and comparative examples are shown below to further clarify the features of the present invention.

[0021]

【Example】

Example 1 The weight ratio of silica to alumina in fly ash was 1.
A waste alumina powder having a ratio of 2: 95.4 was added by 10% by weight based on the internal ratio, and pulverized by a ball mill to an average particle diameter of 6 μm.
5% by weight of bentonite was added and mixed with the prepared raw material as a granulation auxiliary agent and a thickener, and the mixture was humidified using a pan pelletizer to form pellets having a diameter of 10 to 20 mm. After the pellets were dried by a drum type dryer, they were fired in an electric furnace under an air atmosphere at a heating rate of 20 ° C./min at a control temperature of 11600 ° C. for a sufficient time to form aggregates. The absolute dry specific gravity of the aggregate was measured to be 2.41 by the Archimedes method. The method of measuring the water absorption is a 24-hour immersion method. or,
The measured strength of the aggregate was 42 MPa, which was comparable to that of natural aggregate. In addition, when sintering proceeds beyond the control temperature, the absolute specific gravity decreases due to foaming,
The temperature range in which the absolute specific gravity at which high strength and low water absorption were obtained was 2.2 or more was determined as the sintering temperature range, and it was 90 ° C.

Example 2 The same waste alumina 20 as used in Example 1 was used.
%, And sintering was conducted in exactly the same manner as in Example 1, except that the sintering was performed at 1200 ° C for a sufficient time and the sintering temperature range of 2.2 or more was 110 ° C. Was.

Example 3 The same waste alumina 30 as used in Example 1 was used.
%, And sintering was performed in exactly the same manner as in Example 1, except that the raw materials were mixed. The absolute dry specific gravity of the aggregate was measured to be 2.52, and the water absorption was 0.0. The sintering temperature range was 240 ° C.

Comparative Example 1 Aggregate was sintered in the same manner as in Example 1 without adding waste alumina. Control temperature 1120
° C, the absolute specific gravity of the aggregate is 2.46, and the water absorption is 0.0
However, the sintering temperature range was as narrow as 50 ° C., and sintering control was difficult.

Comparative Example 2 Except for adding 40% of waste alumina, sintering of aggregate was performed in the same manner as in Example 1. Control temperature 12
At 40 ° C., the sintering temperature range was 340 ° C., but the absolute dry specific gravity 2.40, water absorption was 3.8, and the product was unsuitable as aggregate.

Example 4 Fly ash having a weight ratio of silica to alumina of 19.
A waste mullite powder having a ratio of 0: 78.5 was added by 10% by weight based on the internal ratio, and pulverized by a ball mill to an average particle diameter of 6 μm.
5% by weight of bentonite was added and mixed with the prepared raw material as a granulation auxiliary agent and a thickener, and the mixture was humidified using a pan pelletizer to form pellets having a diameter of 10 to 20 mm. After drying the pellets with a drum type dryer, the pellets were baked in an electric furnace under an air atmosphere at a heating rate of 20 ° C./minute and a control temperature of 1140 ° C. for a sufficient time to form aggregate. The absolute specific gravity 2.38 water absorption 0.0 of the aggregate sintered by the Archimedes method was measured. The method of measuring the water absorption is a 24-hour immersion method. or,
When the strength of the aggregate is measured, it is 43 MPa in terms of tensile strength.
It was comparable to natural aggregate. or,
When sintering proceeds beyond the control temperature, the absolute dry specific gravity decreases due to foaming, but the temperature range in which the absolute dry specific gravity with which high strength and low water absorption are obtained is 2.2 or more is determined as the sintering temperature width. And 100 ° C.

Example 5 Waste Mullite 20 exactly as used in Example 4
%, And sintering was performed in exactly the same manner as in Example 4, except that the mixture was baked at a control temperature of 1180 ° C. for a sufficient time to form an aggregate. The absolute dry specific gravity of the aggregate was 2.45 and the water absorption was 0.0.
The sintering temperature range was 100 ° C.

EXAMPLE 6 Waste Mullite 30 exactly as used in Example 4
%, And sintering was performed in exactly the same manner as in Example 4, except that the raw materials were mixed. Absolute dry specific gravity of aggregate 2.47, water absorption 0.0
Was measured. The sintering temperature range was 180 ° C.

Comparative Example 3 Waste Mullite 40 exactly the same as that used in Example 4
%, And sintering was carried out in exactly the same manner as in Example 4, except that the raw materials were mixed. The sintering temperature range was 260 ° C., but the absolute dry specific gravity of the aggregate was 2.35 and the water absorption did not fall below 4.3.

Example 7 The weight ratio of silica to alumina in fly ash was 40.
6: 10% by weight of waste porcelain powder that is 54.4
And ground with a ball mill to an average particle size of 6 μm. 5 Bentonite was added to this raw material as a granulation aid and thickener.
By weight addition and mixing, pellets having a diameter of 10 to 20 mm were obtained while humidifying using a pan pelletizer. After the pellets were dried by a drum type dryer, the temperature was raised in an electric furnace under an air atmosphere at a rate of 20 ° C./min.
It was baked at 130 ° C. for a sufficient time to form an aggregate. The absolute specific gravity of the aggregate sintered by the Archimedes method was 2.40 and the water absorption was 0.0. The method of measuring the water absorption is a 24-hour immersion method.
When the strength of the aggregate was measured, it was 41 MPa, which was comparable to that of natural aggregate. When the sintering proceeds beyond the control temperature, the absolute dry specific gravity decreases due to foaming. However, the temperature range where the absolute dry specific gravity for obtaining high strength and low water absorption is 2.22 or more is defined as the sintering temperature range. 800 °
C.

Example 8 Waste ceramic powder 20% exactly as used in Example 7
, And sintering, and sintering was carried out at a control temperature of 1150 ° C. for a sufficient time to obtain an aggregate. The absolute dry specific gravity of the aggregate was measured at 2.49, and the water absorption was measured at 0.0. The sintering temperature range was 100 ° C.

Example 9 The exactly same waste porcelain powder 30 as used in Example 7 was used.
%, And sintering was carried out in exactly the same manner as in Example 7, except that the raw materials were mixed. Absolute dry specific gravity of aggregate 2.51, water absorption 0.0
Was measured. The sintering temperature range was 180 ° C.

Comparative Example 4 Waste ceramic powder 40% exactly the same as that used in Example 7
, And sintering were performed in the same manner as in Example 7, and the mixture was baked at a control temperature of 1240 ° C for a sufficient time to form an aggregate. The sintering temperature range was 180 ° C, but the absolute dry specific gravity of the aggregate was 2.32 and the water absorption did not become 3.4 or less.

Example 10 The weight ratio of silica to alumina in fly ash was 74.
10% by weight of a waste material powder having a ratio of 3: 23.1 was added thereto, and pulverized by a ball mill to an average particle size of 6 μm. 5% by weight of bentonite was added and mixed with the prepared raw material as a granulation auxiliary agent and a thickener, and the mixture was humidified using a pan pelletizer to form pellets having a diameter of 10 to 20 mm. After the pellets were dried by a drum type dryer, they were baked in an electric furnace under an air atmosphere at a temperature rising rate of 20 ° C./min and at a control temperature of 1130 ° C. for a sufficient time to form aggregate. The absolute dry specific gravity of the aggregate sintered by the Archimedes method was 2.42, and the water absorption was 0.0. The method of measuring the water absorption is a 24-hour immersion method. When the strength of the aggregate was measured, it was 40 MPa, which was comparable to that of natural aggregate. Also, when sintering proceeds beyond the control temperature, the absolute dry specific gravity decreases due to foaming, but the temperature range where the absolute dry specific gravity for obtaining high strength and low water absorption is 2.2 or more is defined as the sintering temperature range. Was 90 ° C.

Example 11 Waste material powder 20% exactly as used in Example 10
, And sintering, and sintering was performed at a control temperature of 1150 ° C. for a sufficient time to form an aggregate. Absolute dry specific gravity of aggregate 2.53, water absorption 0.0
Was measured. The sintering temperature range was 110 ° C.

Example 12 Except that 30% of the same waste material powder as used in Example 7 was mixed, the same raw material preparation as in Example 7 was carried out and sintering was carried out. It was baked for a while to form an aggregate. The absolute dry specific gravity of the aggregate was measured to be 2.54, and the water absorption was measured to be 0.0. The sintering temperature range exceeding 1180 ° C is 140 °
C.

Comparative Example 5 Waste material powder 40% exactly the same as that used in Example 10
, And sintering, and sintering was performed at a control temperature of 1220 ° C. for a sufficient time to obtain an aggregate. The sintering temperature range exceeding 1220 ° C is 180 °
C, but the absolute specific gravity of the aggregate was 2.42, and the water absorption was 3.
Did not fall below 2.

Table 1 shows the production conditions of the above Examples and Comparative Examples, and the absolute dry water absorption of the obtained aggregates.

[0039]

[Table 1]

The method for producing an artificial aggregate according to the present invention can effectively reuse fly ash which is difficult to dispose, and has great significance for environmental conservation and effective utilization of resources. The method for producing an artificial aggregate of the present invention provides a high-density, low-water-absorption, high-strength artificial aggregate at a low cost by a production method that is easier to control. Reference number P-5531 Document describing chemical formula etc.

[Table 1]

Claims (3)

[Claims] 1. A method for producing a fly ash artificial aggregate, comprising mixing fly ash and silica-alumina-containing fine powder having a melting point of 1500 ° C. or higher, granulating the mixture, and firing. 2. The method according to claim 1, wherein the total amount of the silica-alumina component in the silica-alumina-containing fine powder is 95% by weight or more, and the content of the alumina component is 23% by weight or more. Method of Producing Fly Ash Artificial Aggregate 3. The method for producing an artificial fly ash aggregate according to claim 1, wherein the blending ratio of the silica-alumina-containing fine powder in the mixture is 10% by weight or more and 30% by weight or less.