JP2000247698A - Production of artificial lightweight aggregate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a material having small dry specific gravity by compounding incineration ash of sewage sludge and coal ash to prepare the source material, granulating the source material and then calcining. SOLUTION: Water is added to the source material prepared by preferably compounding 40 to 185 pts.wt. of coal ash to 100 pts.wt. of incineration ash of sewage sludge, and the obtd. mixture is granulated and calcined. The amt. of water added is controlled to obtain 15 to 35 wt.% of the water content in the source material during granulation. As for a granulating method, an extruding molding machine, pan-type pelletizer or the like is used. A rotary kiln, grate type furnace or fluidized bed furnace method, or the like is used to calcine the granulated material. The calcination temp. is preferably 1,000 to 1,150 deg.C. The compsn. of the incineration ash of sewage sludge consists of 20 to 80 wt.% of SiO2, 5 to 30 wt.% of Al2O3 and 2 to 20 wt.% of Fe2O3. The compsn. of the coal ash consists of 50 to 75 wt.% of SiO2, 15 to 30 wt.% of Al2O3 and 0.5 to 10 wt.% of Fe2O3. A binder (e.g. bentonite) is preferably added by 1 to 5 wt.% to the compounded source material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an artificial lightweight aggregate, and more particularly to a method for producing an artificial lightweight aggregate that can effectively utilize industrial waste as a raw material.

[0002]

2. Description of the Related Art In recent years, as an aggregate for lightweight concrete,
Artificial lightweight aggregates mainly produced by firing expansive shale are used. Lightweight concrete using the above-mentioned artificial lightweight aggregate is used as concrete for civil engineering and concrete for construction.

FIG. 3 shows a process of manufacturing a conventional artificial lightweight aggregate. The rough (expandable shale) is first coarsely crushed and sieved to obtain a shale having a particle size of 20 to 5 mm (hereinafter referred to as coarse shale), a shale having a particle size of 5 to 3 mm (hereinafter referred to as medium shale), And a shale having a particle size of 3 mm or less (hereinafter referred to as fine stone). next,
The obtained coarse crushed stone, medium crushed stone, and fine crushed stone are each fired and sieved to obtain coarse aggregate (particle diameter: 20 to 5 mm, absolute dry specific gravity: 1.29 ± 0.05), medium aggregate ( Particle size: 5 to 3 mm, absolute dry specific gravity: 1.45 ± 0.05) and fine aggregate (particle diameter: -3 mm, absolute dry specific gravity: 1.65 ± 0.05) are produced.

[0004] Coarse aggregate is used as a natural gravel, and fine aggregate is used as a concrete material corresponding to natural sand. Also, among the artificial lightweight aggregates manufactured by the above manufacturing method,
Coarse aggregates are mainly used for various types of civil engineering, such as roadbed materials or lightweight backing materials that cover ground strength.

[0005] Lightweight concrete using the above-mentioned coarse aggregate is 20 to 30% lighter than ordinary concrete, and has performance equivalent to that of ordinary concrete. On the other hand, in recent years, the treatment of industrial waste has become a problem, and the development of a treatment method that enables the recycling of industrial waste has been desired. Coal ash generated by the combustion of coal in boilers at thermal power plants Technology for using (fly ash) as a raw material for artificial lightweight aggregate has been developed.

[0006] That is, Japanese Patent Application Laid-Open No. 9-77543 discloses an artificial lightweight aggregate mainly composed of fly ash and blast furnace slag, both of which are industrial waste.
However, the above-mentioned artificial lightweight aggregate has an absolute dry specific gravity of 1.
It is as large as 32 to 1.99, which limits its use as a lightweight aggregate.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an artificial lightweight aggregate capable of effectively utilizing industrial waste, which has recently become a problem, and capable of producing an artificial lightweight aggregate having a small absolute dry weight. It is intended to provide a manufacturing method.

[0008]

SUMMARY OF THE INVENTION The present invention is a method for producing an artificial lightweight aggregate, which comprises granulating a raw material obtained by mixing sewer sludge incineration ash and coal ash and then firing. The more preferred embodiment of the present invention described above, the sewage sludge incineration ash 100
A method for producing an artificial lightweight aggregate, characterized in that a raw material in which 40 to 185 parts by weight of coal ash is blended with respect to parts by weight is granulated and then fired.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The present inventors have made effective use of industrial waste as a raw material, and as a result of intensive studies on a method for producing an artificial lightweight aggregate capable of producing an artificial lightweight aggregate having a small absolute specific gravity, the following findings ( 1) to (3) have been found, and the present invention has been achieved.

(1): Bubbling action of sewage sludge incineration ash; sewage sludge incineration ash, which is incineration ash of sewage sludge, has a composition close to that of shale and furthermore has a foaming action and is useful as a raw material for artificial lightweight aggregate. It is. (2): Effect of preventing coalescence of particles during firing by blending of coal ash; fusion of particles during burning of granulated raw material by blending coal ash as a raw material of artificial lightweight aggregate This makes it possible to produce an artificial lightweight aggregate having a predetermined particle size range by a method excellent in yield.

(3): Complementary effect by blending both sewage sludge incineration ash and coal ash; By blending both sewage sludge incineration ash and coal ash as raw materials for artificial lightweight aggregate, the characteristics of both are incompatible. As a result, it is possible to prevent the fusion of the granulated particles at the time of firing and to produce an artificial lightweight aggregate having a low absolute dry specific gravity and a low water absorption.

FIG. 1 shows an example of a process chart of the method for producing an artificial lightweight aggregate of the present invention. In the present invention, water is added to a raw material in which sewage sludge incineration ash and coal ash are blended, granulated, and then fired, whereby an intended artificial lightweight aggregate having a small absolute dry specific gravity can be obtained. This is because, under the above-described production conditions, the following actions and mechanisms do not cause fusion of the particles of the granulated material during firing, and an artificial lightweight aggregate having a small absolute dry specific gravity is formed. it is conceivable that.

(1): Bubbling action of sewage sludge incineration ash; sewage sludge incineration ash has a loss on ignition (JIS R 5202) of about 0.1 to 3.
0 wt%, and when firing the granulated material of the raw material mixed with the sewage sludge incineration ash, in the high temperature region, the generation of gas from inside the granulated material particles corresponding to the ignition loss of the sewage sludge incineration ash, The granulated particles expand.

As a result, according to the present invention, an artificial lightweight aggregate having a large number of air bubbles inside particles can be manufactured. (2) The effect of preventing coalescence of particles during firing by blending of coal ash; the blending of coal ash can prevent fusion of particles during burning when using sewage sludge incineration ash.

This is considered to be because the melting point of the raw material increases due to alumina in the coal ash. In the present invention, coal ash 40 to 100 parts by weight of sewage sludge incineration ash
It is preferred to blend 185 parts by weight. The amount of coal ash
When the amount is less than 40 parts by weight, the effect of preventing fusion between the particles of the granulated material due to the blending of the coal ash is small, and it is difficult to produce an artificial lightweight aggregate having a predetermined particle size range by a method excellent in yield. Become.

Conversely, if the blending amount of coal ash exceeds 185 parts by weight, the specific gravity of the bone-dry is increased, and it is difficult to obtain a lightweight aggregate. Also, if the blended amount of coal ash exceeds 185 parts by weight, the water absorption of the resulting artificial lightweight aggregate for 24 hours will increase significantly, and it will be necessary to prepare a pre-press It becomes necessary to absorb water sufficiently by soaking, and the productivity in the production and shipping of artificial lightweight aggregate is reduced.

The sewage sludge incineration ash, coal ash, binder, and a preferred production method used in the present invention will be described below. [Sewage sludge incineration ash:] Sewage sludge incineration ash as industrial waste has a composition similar to that of shale, which has been conventionally used as a raw material for artificial lightweight aggregates, and its main components are SiO ₂ , Al ₂ O ₃ and It is an oxide of iron and has a very small particle size.

The composition of the sewage sludge incineration ash used in the present invention is preferably the following composition as a sample composition after drying at 100 ° C. Preferred compositions of the Sewer sludge incineration _{ash; SiO 2: 20~80wt%, Al} 2 O
_{3: 5~30wt%, Fe 2 O} 3: 2~20wt% As the sewage sludge incineration ash, JIS R 5202-1989
The ignition loss by (chemical analysis method of Portland cement) is preferably 0.1 to 3.0% by weight, more preferably 0.1 to 3.0% by weight.
It is preferable to use sewage sludge incineration ash of 2 to 2.0 wt%.

This is because when the ignition loss is less than 0.1 wt%,
This is because the amount of gas generated is small and the weight reduction by foaming is insufficient, and if it exceeds 3.0 wt%, the foaming becomes remarkable and the strength of the obtained artificial lightweight aggregate may be insufficient. . Conventionally, disposal of sewage sludge incineration ash has been an important problem. According to the present invention, these problems can be largely solved.

[Coal ash:] Coal ash as industrial waste is mainly composed of oxides of SiO ₂ , Al ₂ O ₃ and iron, and has a composition close to that of shale. As the coal ash used in the present invention, it is preferable to use coal ash generated from the combustion of coal in a boiler of a thermal power plant from a quantitative point of view. There is no restriction.

The coal ash used in the present invention is preferably a coal ash having the following composition after drying at 100 ° C. Preferred compositions of coal _{ash; SiO 2: 50~75wt%, Al} 2 O 3: 15~30
_{wt%, Fe 2 O 3:} 0.5 ~10wt% [Binder:] In the present invention, it is preferable to add a binder in the formulation material.

The binder is preferably one or more selected from bentonite, lignin, pulp waste liquor, polyvinyl alcohol, styrene-butadiene latex, carboxymethylcellulose, and the like. Bentonite is more preferably used. When bentonite is used, for example, the amount of the binder added is preferably 1 to 5% by weight based on the total raw materials (dry amount).

[Manufacturing method:] As shown in FIG. 1 described above, in the present invention, water is added to a raw material in which sewage sludge incineration ash and coal ash are blended, granulated, fired, and then sieved. This produces an artificial lightweight aggregate. The amount of water added to the raw material should be such that the water content in the raw material during granulation is 15-35 wt%
It is preferable that the addition amount is as follows.

As the granulation method, an extrusion molding machine (: an extrusion granulation machine), a pan-type pelletizer, and the like can be used. The method of the granulation method is not particularly limited, but the obtained artificial It is more preferable to use an extrusion molding machine in view of the strength of the lightweight aggregate. In the firing of the granulated material, a rotary kiln, a great firing furnace, a fluidized roasting furnace, or the like can be used, and the firing method is not particularly limited.

The firing temperature is preferably from 1,000 to 1,150 ° C., and more preferably from 1,000 to 1,100 ° C. If the firing temperature is less than 1000 ° C, foaming in the granulated particles does not sufficiently proceed, and the absolute dry specific gravity of the obtained aggregate is large. Uniform and sufficient foaming and expansion do not progress,
The absolute specific gravity increases as described above.

According to the present invention, since both the incineration ash and the coal ash of the sewage sludge are fine, the crushing of the raw material necessary for the production of the artificial lightweight aggregate using the conventional shale shown in FIG. Is basically unnecessary, and an artificial lightweight aggregate can be manufactured by a simpler process than the conventional method. As described above, the method for producing the artificial lightweight aggregate of the present invention has been described.According to the present invention, both artificial sewage sludge incineration ash and coal ash, which are industrial wastes, are used to the maximum, and the artificial light weight having a small absolute specific gravity. Aggregate can be manufactured in a simple process.

In the present invention, in addition to sewage sludge incineration ash, coal ash and the above-mentioned binder, shale and lapilli used in the manufacture of artificial lightweight aggregates, unless the object of the present invention is impaired. Raw materials such as (pumice) and additives such as silicon carbide (foaming aid) may be blended. In this case, by mixing 40 to 185 parts by weight of coal ash with respect to 100 parts by weight of sewage sludge incineration ash in all the blended raw materials, an artificial lightweight aggregate having a low absolute dry specific gravity, which is the object of the present invention, is produced. It is possible.

[0028]

EXAMPLES The present invention will be described below more specifically based on examples. According to the manufacturing process shown in FIG. 1 described above, an artificial lightweight aggregate was manufactured using sewage sludge incineration ash and coal ash as raw materials. That is, the sewage sludge incineration ash and coal ash were blended in predetermined amounts as shown in Table 1, water was added to the blended raw materials, and the mixture was kneaded with a kneader.

It should be noted that bentonite was used as a binder in the raw material before water was added, and 2 wt% in the total blended raw material (dry amount).
Was added so that The amount of water added during kneading is
It was set so that the water content in all the ingredients was 25 wt%.
As the sewage sludge incineration ash, the sewage sludge incineration ash having the following composition and ignition loss was used, and as the coal ash, the following ash generated from a thermal power plant was used.

(Sewage sludge incineration ash :) Composition of sample after drying at 100 ° C .: SiO ₂ ; 35 wt%, Al ₂ O ₃ ;
wt%, Fe ₂ O ₃ ; 4 wt% Loss on ignition [JIS R 5202-1989]: 1 wt% (coal ash) SiO ₂ : 60 wt%, Al ₂ O ₃ : 22 wt%, Fe ₂ O ₃ : 4 wt% The obtained kneaded material is granulated using an extrusion molding machine (: an extrusion granulator), and is granulated by a rotary kiln.
After sintering at 80 ° C, sieving is performed with a mesh sieve 20mm (mesh size: 19mm) and a mesh sieve 5mm (mesh size: 4.75mm).
An artificial lightweight aggregate (coarse aggregate) of 20 to 5 mm was produced.

Next, the absolute dry specific gravity, the water absorption rate for 24 hours and the crushing strength of the obtained artificial lightweight aggregate (coarse aggregate) were measured. The absolute dry specific gravity and the water absorption rate for 24 hours were measured based on JIS A 1134 and 1135. The test results obtained are shown in Table 1 and FIG. As shown in Table 1 and FIG. 2, the use of the incineration ash and the coal ash of the sewage sludge was able to obtain the intended artificial lightweight aggregate having a small absolute dry specific gravity.

Further, by setting the blending amount of coal ash with respect to the sewage sludge incineration ash to a preferable range in the present invention,
The fusion of the particles during the firing of the granulated material was prevented, and an artificial lightweight aggregate having a low absolute dry specific gravity and a low water absorption for 24 hours was obtained. Further, from the test results, it was found that a high-strength artificial lightweight aggregate can be manufactured by using an extrusion molding machine.

[0033]

[Table 1]

[0034]

According to the present invention, it is possible to produce an artificial lightweight aggregate having a small absolute dry weight in a simple process using industrial waste as a raw material, by effectively utilizing the characteristics of sewage sludge incineration ash and coal ash. Became possible. Further, according to the present invention, as a raw material of the artificial lightweight aggregate, in place of conventionally used shale, sewage sludge incineration ash and coal ash as industrial waste are used, thereby achieving resource saving. It has become possible.

[Brief description of the drawings]

FIG. 1 is a process chart showing an example of a method for producing an artificial lightweight aggregate of the present invention.

FIG. 2 is a graph showing the relationship between the blending ratio of coal ash, the absolute dry specific gravity of artificial lightweight aggregate, and the 24-hour water absorption.

FIG. 3 is a process chart showing a conventional method for producing an artificial lightweight aggregate.

Claims (2)

[Claims] 1. A method for producing an artificial lightweight aggregate, comprising granulating a raw material obtained by mixing sewer sludge incineration ash and coal ash and then firing the raw material. 2. The method for producing an artificial lightweight aggregate according to claim 1, wherein 40 to 185 parts by weight of coal ash is mixed with 100 parts by weight of the sewage sludge incineration ash.