JPH0977540A - Production of artificial aggregate and artificial aggregate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a producing method of an artificial aggregate capable of stably firing at a relatively low temp. and in a wide firing temp. range and having stable quality by using a fly ash containing a specific component as a raw material. SOLUTION: A fly ash containing 30-50wt.% vitreous particle, a fly ash containing 20-50wt.% mullite crystal particle or a fly ash containing 30-50wt.% vitreous particle and 20-50wt.% mullite crystal particle is granulated and fired as a main component. Or, a low temp. sintering fly ash to be sintered at <=1250 deg.C and a high temp. sintering fly ash to be sintered at >=1350 deg.C are mixed and fired. In such a case, the content of the low temp. sintered fly ash is usually controlled to 20-60wt.%. The firing is performed at 1100-1300 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an artificial aggregate and an artificial aggregate, particularly fly ash, which is fired at a relatively low temperature and in a wide firing temperature range, and has stable quality. The present invention relates to an artificial aggregate manufacturing method and an artificial aggregate that can be

[0002]

When coal is used as a fuel in a boiler or the like of a thermal power plant, a large amount of fly ash is generated as so-called industrial waste. The fly ash generated in one year is about 4 million tons, and about half of the fly ash is effectively used in the construction of cement concrete, the civil engineering field, and the ceramics field. However, looking at recent trends,
Although the amount of fly ash generated is steadily increasing, the effective utilization rate has remained below 50%, and it is hoped that the effective use of fly ash will be further promoted from the standpoint of environmental conservation. It

As one of the effective utilization of such fly ash, fly ash is used as a main raw material and is granulated,
Although there is an artificial aggregate obtained by firing, despite the fact that the history of research into an aggregate using fly ash as a raw material is old, very few are currently in practical use. The cause was that the fly ash had large variations in chemical and physical properties, so that aggregate with stable quality could not be produced at a high recovery rate under certain production conditions.

[0004]

[Problems to be Solved by the Invention] That is, the chemical and physical properties of fly ash vary greatly depending on the power generation conditions such as the coal type of coal used as fuel in a thermal power plant and the combustion temperature. In manufacturing an artificial aggregate using such fly ash as a raw material, the firing conditions for obtaining a predetermined quality also change, the amount of unsintered aggregate and the amount of fused aggregate increase, and The change in specific gravity also changed greatly, and there was a drawback that the recovery rate of non-defective products declined.

Therefore, according to the present invention, the fly ash is used as a raw material, and the artificial aggregate can be stably fired at a relatively low temperature and in a wide firing temperature range. The purpose is to provide an artificial aggregate.

[0006]

In order to achieve the above object, according to the method for producing an artificial aggregate of the present invention, fly ash having a glassy particle content of 30 to 50% by weight is used as a main raw material. Granulating and firing (Claim 1), granulating and firing with fly ash having a mullite crystal particle content of 20 to 50% by weight as a main raw material (Claim 2), glassy particles Content of 30 to 50% by weight,
Granulation and firing of fly ash having a mullite crystal particle content of 20 to 50% by weight as a main raw material (Claim 3) and firing in a temperature range of 1100 to 1300 ° C (Claim 4). Mixing two or more types of fly ash (claim 5), mixing and granulating low-temperature sintered fly ash that is sintered at 1250 ° C. or lower and high-temperature sintered fly ash that is sintered at 1350 ° C. or higher, 1100-1
It is characterized in that it is fired in a temperature range of 300 ° C. (claim 6), and the content of low temperature sintered fly ash is 20 to 60% by weight (claim 7).

According to the artificial aggregate of the present invention, fly ash having a glassy particle content of 30 to 50% by weight is granulated and fired as a main raw material (claim 8). Content of crystal particles of 20 to 50% by weight
The fly ash as a main ingredient is granulated and fired (claim 9), and the content of glassy particles is 30 to 5
It is characterized in that it is obtained by granulating and firing fly ash having 0 wt% and mullite crystal particle content of 20 to 50 wt% as a main raw material (claim 10). BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below, and% means% by weight.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Fly ash is composed mainly of spherical glassy particles, crystal particles such as quartz and mullite,
It is an aggregate consisting of unburned carbonaceous matter and the like. When fly ash is granulated and fired to form an aggregate, sintering of the aggregate occurs due to melting of vitreous particles prior to melting of crystal particles such as quartz and mullite. Simultaneously with the melting of the glassy particles, a small amount of carbonaceous matter captured in the particles is oxidized to form a high-strength lightweight aggregate in which foamed pores are uniformly dispersed.

The present inventors combined the fly ash having different vitreous particle content and mullite crystal particle content in the fly ash and different sintering temperatures to obtain a firing temperature and a firing temperature range. Therefore, the present invention has been completed. That is, although fly ash containing a large amount of glassy particles sinters at 1300 ° C. or lower, the firing temperature range is narrow, and process control becomes difficult in manufacturing. Fly ash containing a large amount of crystalline particles such as quartz and mullite has a wide firing temperature range, but requires a high temperature of 1350 ° C. or higher to sinter the aggregate, which is not preferable because of high manufacturing cost.

The first aspect of the present invention is to select a fly ash having a glassy particle content of 30 to 50% among various types of fly ash having different properties depending on the type of coal, the combustion conditions and the like. Characterize. The glassy particle content in fly ash is measured by a means such as a point counting method under a microscope or a powder X-ray diffraction method,
Artificial aggregate obtained from such fly ash as a raw material is sintered at a relatively low temperature of 1300 ° C or lower,
The firing can be performed within the above firing temperature range. The raw material may be prepared so that the content of the glassy particles is in the range of 30% to 50% by mixing two or more types of fly ash. If the content of the glassy particles is less than 30%, the sintering temperature becomes 1300 ° C. or higher, which is industrially expensive, which is not preferable. Further, if the content exceeds 50%, the firing temperature range becomes narrower than 100 ° C., not only the manufacturing control becomes difficult, but also the amount of unsintered aggregate or the aggregate that melts and fuses is generated. Increase, and the recovery rate of non-defective products decreases.

Next, the fly ash is selected so that the content of the mullite crystal particles in the fly ash is in the range of 20 to 50%. The aggregate obtained from such fly ash as a raw material can be fired with a firing temperature range of 100 ° C. or higher. The content of mullite crystal particles is 20-
Mixed ash composed of two or more kinds may be used as long as it is controlled to 50%. If the content of mullite crystal particles is less than 20%, the sintering temperature range will be less than 100 ° C., which not only makes it difficult to control the process in manufacturing, but also the amount of unsintered aggregate or fused aggregate generated. Increase, and the recovery rate of non-defective products decreases. When the content of mullite crystal particles exceeds 50%, the sintering temperature range is widened but the sintering temperature is 13%.
It is not preferable because the temperature rises extremely above 50 ° C. and the manufacturing cost increases.

Further, the present invention is a mixed ash comprising two types of fly ash which is sintered at 1250 ° C. or lower and fly ash which is sintered at 1350 ° C. or higher, and the content of low temperature sintered ash is 20% to 20%. The mixed ash prepared so as to be in the range of 60% is used as a raw material. Fly ash that sinters at a low temperature has a narrow firing temperature range, and fly ash that sinters at a high temperature has the disadvantages that it requires a higher temperature to form an aggregate. By mixing the ash in a certain ratio, it is possible to complement each other's drawbacks. The aggregate obtained by using the mixed ash thus prepared as a raw material can be sintered at 1300 ° C. or lower, and the firing temperature range is 100 ° C. or higher to produce an aggregate with stable quality in good yield. You can

If the content of the low-temperature sintered ash is less than 20%, the sintering temperature rises to 1300 ° C. or higher, which is costly in manufacturing, which is not preferable, and the low-temperature sintered ash content is 60%. %, The sintering temperature range becomes less than 100 ° C., which not only makes manufacturing process control difficult, but also increases the amount of unsintered aggregate and fused aggregate, which reduces the recovery rate of non-defective products. To do.

The fly ash selected or prepared in this manner is, of course, the fly ash specified by JIS, including fly ash usually called raw powder, and cinder ash, or fluidized bed fly ash. It is possible to use all kinds of coal ash in a broad sense that can be obtained regardless of the combustion method of coal, and crush these fly ash as necessary to secure the strength of the granulated material, or granulation aid A small amount of a binder such as bentonite is added as an agent.

Next, after the steps of humidification, granulation and drying,
Obtain pellets for firing. The granulation method is not particularly limited, but granulation with a pan pelletizer, an extrusion molding machine, or the like is preferable from the viewpoint of ease of molding and industrial mass productivity.

By heating the pellets obtained as described above at a temperature of 1100 to 1300 ° C. in a calcining furnace such as a rotary kiln, and then cooling, a good quality lightweight aggregate can be obtained. That is, as described above, the content of glassy particles in fly ash, and the content of mullite crystal particles, and by combining fly ash having different sintering temperatures, a relatively low temperature and a wide firing temperature range With this, it is possible to burn aggregate with stable quality.

[0017]

Examples (Examples 1 to 8 and Comparative Examples 1 to 8) Fly ash having a content of glassy particles shown in Table 1 of 11 to 84% was granulated, and in the air atmosphere, 1100 ° C to 1500 ° C. The artificial aggregate was obtained by firing at a predetermined temperature within the temperature range of 10 minutes, and the aggregate was evaluated by the sintering temperature and the firing temperature range. Table 1 shows the results
Are also shown. In Table 1, when fly ash having a glassy particle content of 30 to 50% of the present invention is used, the firing temperature is 1300 ° C. or lower, and the firing temperature range is 10.
It was 0 ° C or higher, and an aggregate with stable quality could be obtained. On the other hand, if the content of the glassy particles is less than 30%, the firing temperature rises extremely, which is industrially expensive, which is not preferable. Further, when the content of the glassy particles exceeds 50%, the firing temperature range becomes less than 100 ° C., unsintered aggregates are formed, or softening occurs, and fusion between the aggregates occurs. The recovery rate of was decreased.

[0018]

[Table 1]

Examples 9 to 12 and Comparative Examples 9 to 12 Fly ash having a glassy particle content of 15% and 67% fly ash were mixed, and the content of glassy particles shown in Table 2 was 21. % -57% of the mixed ash is granulated,
When the aggregate was obtained by firing at a predetermined temperature within the temperature range of 1100 ° C. to 1500 ° C. for 10 minutes in the air atmosphere, and evaluating the aggregate in the same manner as in the previous example, the same result was obtained.
Table 2 shows the results.

[0020]

[Table 2]

(Examples 13 to 19, Comparative Examples 13 to 18)
Fly ash having a content of mullite crystal particles of 0 to 61% is granulated, and the air is heated to 1100 ° C to 1500 ° C.
The aggregate was obtained by firing for 10 minutes at a predetermined temperature within the temperature range of ° C, and the aggregate was evaluated by the firing temperature range. The results are shown in Table 3. In Table 3, when the fly ash having a mullite crystal particle content of the present invention of 20 to 50% is used,
The firing temperature is 1300 ° C or lower, and the firing temperature range is 100 ° C.
As described above, the aggregate with stable quality could be obtained.
On the other hand, if the content of the mullite crystal particles is less than 20%, the firing temperature range will be less than 100 ° C., which will result in unsintered aggregate, or softening will result in fusion between aggregates. Then, the collection rate of non-defective products decreased. On the other hand, if the content of mullite crystal particles exceeds 50%, the firing temperature range can be satisfied, but the firing temperature rises extremely, which is industrially expensive, which is not preferable.

[0022]

[Table 3]

(Examples 20 to 22, Comparative Examples 19 to 20)
Fly ash with 0% mullite crystal particles and 3
4% fly ash was mixed to prepare a mixed ash having a mullite crystal particle content shown in Table 4 within a range of 7% to 27%. This mixed ash was granulated and calcined in the same manner as in the above-mentioned example to obtain an aggregate, and the aggregate was evaluated according to the calcining temperature range, and similar results were obtained. The results are also shown in Table 4.

[0024]

[Table 4]

(Examples 23 to 27, Comparative Examples 21 to 23)
1 low temperature sintering fly ash with a sintering temperature of 1220 ° C and 1 high temperature sintering fly ash with a sintering temperature of 1380 ° C
A mixed ash composed of two kinds of seeds, the mixed ash prepared so that the content of the low temperature sintered ash is within the range of 10% to 80% by weight, and the granulated pellets are subjected to an atmospheric atmosphere. The artificial aggregate was obtained by heating and holding at a predetermined temperature within a range of 1100 to 1400 ° C. for 10 minutes, and the aggregate was evaluated by the sintering temperature and the firing temperature range. Table 5 shows the results. Table 5
In, the content of the low temperature sintered ash of the present invention is 20 to 60.
With 100% fly ash, the firing temperature is 1300
Below 0 ° C, the firing temperature range was 100 ° C or above, and an aggregate with stable quality could be obtained. On the other hand, if the content of the low-temperature sintered ash is less than 20%, the firing temperature is extremely increased, which is industrially expensive, which is not preferable. If the content of low-temperature sintered ash exceeds 60%, the firing temperature range will be less than 100 ° C, resulting in unsintered aggregate or fusion of aggregates, resulting in a good product recovery rate. Fell.

[0026]

[Table 5]

[0027]

According to the present invention described above, fly ash, which is difficult to dispose of, can be effectively reused, which greatly contributes to environmental conservation, and has a low firing temperature and a wide firing temperature range. In this way, it is possible to produce aggregate with stable quality with a high recovery rate.Of course, as aggregate for concrete, aggregate for asphalt, backfill material, roadbed material, flooring material, etc. It can be used effectively.

Claims (10)

[Claims] 1. A method for producing an artificial aggregate, which comprises granulating fly ash having a glassy particle content of 30 to 50% by weight as a main raw material and firing the granules. 2. The content of mullite crystal particles is 20 to 5.
Granulate with 0 wt% fly ash as the main raw material,
A method for producing an artificial aggregate, which comprises firing. 3. Fly ash having a glassy particle content of 30 to 50% by weight and a mullite crystal particle content of 20 to 50% by weight is granulated and fired as a main raw material. Manufacturing method of artificial aggregate. 4. The method for producing an artificial aggregate according to claim 1, wherein the firing is performed in a temperature range of 1100 to 1300 ° C. 5. The method for producing an artificial aggregate according to claim 1, wherein two or more types of fly ash are mixed. 6. A low temperature sintered fly ash which is sintered at 1250 ° C. or lower and a high temperature sintered fly ash which is sintered at 1350 ° C. or higher are mixed, granulated and fired in a temperature range of 1100 to 1300 ° C. A method for producing a characteristic artificial aggregate. 7. The content of low temperature sintered fly ash is 20.
The method for producing an artificial aggregate according to claim 6, wherein the content is -60% by weight. 8. An artificial aggregate obtained by granulating and firing fly ash having a glassy particle content of 30 to 50% by weight as a main raw material. 9. The content of mullite crystal particles is 20 to 5.
An artificial aggregate characterized by being granulated and fired with 0% by weight of fly ash as a main raw material. 10. The content of glassy particles is 30 to 50% by weight, and the content of mullite crystal particles is 20 to 50% by weight.
An artificial aggregate characterized by being formed by granulating and firing fly ash as a main raw material.