JP2001163647A - Producing method of artificial aggregate using waste incineration ash and artificial aggregate obtained by this method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a producing method for obtaining an artificial aggregate which has absolute dry specific weight of <=2.0, uniaxial compression breaking load of >=20 kgf and water absorption of <=10%, and the artificial aggregate obtained by this method. SOLUTION: In this producing method of the artificial aggregate, a caking agent, a reducing agent, coal ash and, if necessary, a foaming agent are mixed or mixingly pulverized into waste incineration ash in such a manner that a calcium content gets to <=40 wt.% expressed in terms of the oxide, are formed after adding water and the formed body is incinerated after drying as necessary. Therein, the foaming agent is added to the said waste incineration ash, further, the said reducing agent is charcoal material and the said foaming agent is at least one kind of iron oxide and silicon carbide. Furthermore, this artificial aggregate is obtained by the said producing method, has absolute dry specific weight of <=2.0, uniaxial compression breaking load of >=20 kgf and water absorption of <=10%.

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 for civil engineering and construction using waste incineration ash generated from a waste incineration facility or the like as a main material, and an artificial aggregate obtained by this method. It is.

[0002]

2. Description of the Related Art Conventionally, incineration ash generated from refuse incineration facilities includes main ash, which is incineration residue, and fly ash which collects ash scattered in exhaust gas. Most of the ash is landfilled as waste. Has been disposed of. And since fly ash contains heavy metals such as lead, cadmium and chromium, at present, it is melt-solidified, cement-solidified, chelated, and acid-washed to prevent leaching of heavy metals and detoxify them. Landfill disposal.

However, the melting and solidification method has a high processing cost,
Other methods have the problem of lack of long-term reliability.In addition, many municipalities are struggling to secure final disposal sites and extend the remaining years, so fly ash is not recycled as waste but as recycled. There is a long-awaited need for the development of technologies for effective use.

As one of such methods, the present inventors have previously used fly ash as a main raw material to control the composition of a binder such as a binder, silica sand, pottery stone and feldspar, and a foaming agent such as hematite and silicon carbide. Japanese Patent Application Laid-Open No. Hei 10-287675 discloses a method for producing an artificial aggregate for civil engineering and construction having a small amount of heavy metal elution by pelletizing by adding a reducing agent such as coke or the like and firing the pellet in a rotary kiln.

According to this method, waste incineration ash can be effectively used as artificial aggregate and can contribute to the extension of the remaining years of the final disposal site. In addition, since it greatly varies depending on the operating conditions and the like, it is indispensable to control the composition with additives in order to produce a desired artificial aggregate according to the application. From this point of view, the present inventors further disclosed a technique for adding a composition control agent in Japanese Patent Application No. 10-360909, but a detailed study on a production method using a less expensive composition control agent is further required. Met.

[0006]

Accordingly, the present invention provides a method for producing an artificial aggregate having an absolute dry specific gravity of 2.0 or less, a uniaxial compressive breaking load of 20 kgf or more, and a water absorption of 10% or less. And an artificial aggregate obtained by this method.

[0007]

Means for Solving the Problems The present inventors have increased the effective utilization rate of the above incinerated ash, have an absolute dry specific gravity of 2.0 or less, have a high uniaxial compression breaking load, and have a low water absorption rate. As a result of an in-depth study of a production method for obtaining the above, the present inventors have found that the above problem can be solved by adding a predetermined amount of coal ash as a composition control agent for aggregate, and have completed the present invention.

In order to achieve the above object, the method for producing an artificial aggregate using waste incineration ash according to the first embodiment of the present invention is characterized in that the calcium content of the waste incineration ash is 4 in terms of oxide.
A binder, a reducing agent, coal ash and, if necessary, a foaming agent are added and mixed or mixed and pulverized so as to be 0% by weight or less, and water is added to mold, and the molded body is dried if necessary. And then firing. Further, the reducing agent is a carbon material, and the foaming agent is at least one of iron oxide and silicon carbide.

The artificial aggregate according to the second embodiment of the present invention is obtained by the method according to the first embodiment, and has an absolute dry specific gravity of 2.0 or less and a uniaxial compressive breaking load. It is characterized in that it is 20 kgf or more and the water absorption is 10% or less.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention and its operation will be more specifically described below. The main components such as clay and shale, which are the raw materials of general artificial aggregate, are silica, alumina, calcia, and the like, and the incineration ash has almost the same composition. In order to give mechanical strength to the artificial aggregate, the inside of the pellet may be made semi-molten during firing and vitrified, and in order to reduce the weight, the inside is melted, and at the same time the viscosity decreases moderately What is necessary is just to capture the bubble by a volatile component inside. Specific gravity control can be performed by adjusting such a foaming state.

However, incineration ash generated from refuse incineration facilities and the like has different chemical and physical properties depending on the incineration facilities, combustion products, operating conditions, and the like, and is in comparison with natural minerals that are raw materials of general artificial aggregates. Therefore, since the content of silica, alumina and the like is low, it is difficult to vitrify the inside of the pellet in a semi-molten state and to impart mechanical strength.

According to the present invention, a binder, a reducing agent, coal ash and, if necessary, a foaming agent are added to the waste incineration ash so that the calcium content is 40% by weight or less in terms of oxide. The absolute specific gravity is 2.0 or less, the uniaxial compression breaking load is 20 kgf or more, and the water absorption is 10%.
It is characterized in that the following artificial aggregate can be manufactured.

[0013] The waste incineration ash that is the subject of the present invention is not particularly limited, and main ash, fly ash, or a mixture thereof can be used. Also, there is no particular effect on the particle size of the incineration ash. In the present invention, coal ash is used as a composition control agent, because silica in the coal ash contributes to vitrification at the time of firing and increases the mechanical strength of the aggregate. Therefore, the amount of coal ash added can be appropriately selected so as to obtain the required physical properties according to the use of the aggregate, but is preferably 40% by weight or less from the viewpoint of the effective utilization rate of the incineration ash and the calcium content. . The reason is that if the calcium content exceeds 40% by weight, the appropriate firing temperature range exceeds 1300 ° C. or more. Therefore, it is practically used due to the problem of heat energy cost and welding of aggregate to the inner wall of the rotary kiln or welding of aggregates. Not only that, but also the firing temperature range becomes narrow. The smaller the amount of coal ash is, the more preferable it is. However, if it is less than 5% by weight, the mechanical strength of the aggregate becomes insufficient, so the lower limit is 5% by weight.

The coal ash is not particularly limited as long as it is generated from a thermal power plant or a coal-fired boiler.
For example, all coal ash including fly ash, a mixture of fly ash and synda ash, fly ash, coarse powder, and clinker ash conforming to JIS A 6201 can be used. The particle size of the coal ash is not particularly limited. Further, some types of coal ash include unburned carbon, but such ash exhibits a function as a reducing agent described below, and thus has the advantage that it is not necessary to add a new reducing agent depending on the amount of unburned carbon. is there.

Further, the reason why the binder is used in the present invention is that it is added in order to give moldability and mechanical strength of pellets after hydration granulation. If the mechanical strength is weak, pellets will be powdered during firing in the rotary kiln and the product yield will be reduced, and powdered material will adhere to the pellet surface near the firing zone or adhere to the inner wall of the rotary kiln This would hinder continuous operation. The type of the binder is not particularly limited, for example, bentonite,
Examples include inorganics such as water glass, and organics such as starch, molasses, lignin, polyvinyl alcohol, methylcellulose, and natural rubber pulp waste liquid. Further, the amount of the binder added is not particularly limited, but is preferably in the range of 0.5 to 10% by weight in consideration of the effect of addition and cost.

The foaming agent and the reducing agent generate a gas by the action of the foaming agent and the reducing agent when the inside of the pellets is in a semi-molten state during firing, and the gas is trapped as bubbles in the pellets, whereby the specific gravity is reduced. Used to control

The type of the foaming agent or the reducing agent is not particularly limited as long as it exhibits the above-mentioned effects.
In the present invention, iron oxide or silicon carbide is preferable as the foaming agent, and carbonaceous material is preferable as the reducing agent. Further, hematite having a high degree of oxidation is particularly preferable as the iron oxide used as the foaming agent. The particle size of the iron oxide used as the foaming agent is not particularly limited, but is preferably 10 μm or less in order to promote a deoxidation reaction by the carbon material during firing. The preferred amount of hematite as a foaming agent is 1 to 10% by weight based on the whole aggregate-mixed raw material. The reason is that if it is less than 1% by weight, the effect as a foaming agent is small, and if it exceeds 10% by weight, the effect of weight reduction by foaming does not increase.

Further, the silicon carbide used as the foaming agent captures CO and CO ₂ gas generated by efficiently reacting with the iron oxide when the granulated pellets generate a large amount of liquid phase by heating, and foams and swells the pellets. To promote. The amount of silicon carbide to be added to the entire raw material of the aggregate is 0.1% by weight or more.
It is preferably 1.0% by weight. If the addition amount is less than 0.1% by weight, the effect on the weight reduction of the aggregate is not sufficient,
Further, even if it exceeds 1.0% by weight, the light weight effect does not increase.

The carbonaceous material as a reducing agent mainly functions to regulate the degree of reduction inside the pellets during firing, and to reduce iron oxide to exert a function of foaming by CO and CO ₂ gas. Examples of the carbon material include coal and coke. Therefore, it is possible to replace a part of silicon carbide with a carbon material.

Next, the amount of the carbonaceous material to be added to the whole raw material of the aggregate is preferably 0.2 to 10% by weight. If the amount is less than 0.2% by weight, the effect of weight reduction by foaming cannot be obtained, while if it exceeds 10% by weight, the effect of weight reduction by foaming expansion does not increase, and unburned carbon remains inside the pellet. Therefore, the strength of the artificial aggregate may be reduced.

When the mixture obtained by mixing the respective aggregate blending raw materials is pulverized, the method may be any method as long as the mixed aggregate blending raw material can be finely pulverized to an average particle size of 20 μm or less, preferably 15 μm or less. And a ball mill such as a pot mill, a vibration mill, and a planetary mill, a collision-type jet pulverizer, and a turbo pulverizer.

Next, the obtained pulverized material is wet-kneaded as necessary, but the kneading method to be employed is not particularly limited, and a known kneading apparatus can be used. As a molding method, any method can be used as long as it can be molded so as to have a predetermined diameter. For example, it is convenient to use a pan pelletizer or an extruder.

The obtained molded product is dried and fired if necessary, but the firing method is not particularly limited. For example, a rotary kiln is preferably used in consideration of continuous operation and uniformity of quality. The atmosphere can be arbitrarily selected according to the physical properties of the aggregate. For example, the oxygen concentration in the combustion gas is 3% to 12%, and the firing zone temperature is 1000 ° C to 130 ° C.
0 ° C., the residence time of the molded body at the firing zone temperature is 1 minute to 1 minute.
It is preferable to operate the rotary kiln so as to be 20 minutes in consideration of the gradient of the rotary kiln, the number of revolutions, the kiln structure such as the dam installation and the inner diameter, and the like. The drying method applied as necessary before firing is not particularly limited.

[0024]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. However, the present invention is not limited to the following examples. The main components of the waste incineration fly ash used were: SiO ₂ : 27.36% by weight, Al ₂ O ₃ :
13.00% by weight, Fe ₂ O ₃ : 1.51% by weight, Ca
O: 15.70% by weight, MgO: 3.31% by weight, Na
₂ O: 8.70% by weight, K ₂ O: 7.39% by weight. The main components of the coal ash used as the composition control agent were SiO ₂ : 66.5% by weight and Al ₂ O ₃ : 25.5.
_{Wt%, Fe} 2 O 3: 4.06 wt%, CaO: 0.8
4% by weight, MgO: 0.50% by weight, Na ₂ O: 0.3
0 _wt%, K 2 O: 0.82 wt%.

Example 1 67.5% by weight of incinerated fly ash, 5% by weight of bentonite, 5% by weight of hematite, coke 2
Wt%, silicon carbide 0.5 wt% and coal ash 20 wt%
Was mixed and pulverized to an average particle size of 15 μm using a ball mill. While adding water to the pulverized product, the mixture was granulated into a spherical shape having a diameter of about 5 to 15 mm using a pan pelletizer, and then dried at 105 ° C. with ventilation. Next, the dried aggregate is supplied to a rotary kiln having a brick inner diameter of 400 mm and a length of 8000 mm, and is calcined under the conditions that the oxygen concentration in the combustion gas is 5%, the temperature is about 1080 ° C., and the residence time is 30 minutes. I got As the quality evaluation of the obtained aggregate a,
The absolute dry specific gravity and the water absorption were measured based on JIS A 1110, and the uniaxial compressive breaking load (hereinafter referred to as “crush strength”) was measured using a crush tester. The obtained results are shown in Table 1 below. The measurement was performed for each aggregate having a diameter of about 10 mm, and the average value was obtained.

As can be seen from Table 1, aggregate a of Example 1 had an absolute dry specific gravity of 1.30, a crush strength of 32 kgf, and a water absorption of 3%. As a result of chemical analysis, calcium in the aggregate a in terms of oxide was 10.8% by weight.

[Examples 2 to 14 and Comparative Examples 1 to 3] Aggregate b (Example 2) and aggregate c (Example) except that the rotary kiln temperature was 1040 ° C. and 1060 ° C., respectively. Aggregate d (Example 4) was prepared in the same manner as in Example 1 except that Example 3) was changed to 73.0% by weight of incinerated fly ash, 5% by weight of bentonite, 2% by weight of coke, and 20% by weight of coal ash. 70.0% by weight of incinerated fly ash, 5% by weight of bentonite, 3% by weight of hematite, 2% by weight of coke
Aggregate e (Example 5) was prepared in the same manner as in Example 1 except that the amount of coal ash was 20% by weight, and 47.5% by weight of incinerated fly ash.
An aggregate f (Example 6) was prepared in the same manner as in Example 1 except that 5% by weight of bentonite, 5% by weight of hematite, 2% by weight of coke, 0.5% by weight of silicon carbide and 40% by weight of coal ash were used. Rotary kiln temperature 1100 ° C, 1120
Each in the same manner as in Example 1 except that the
(Example 7), aggregate h (Example 8) was incinerated fly ash 32.
Aggregate i (Example 1) except that 5% by weight, 5% by weight of bentonite, 5% by weight of hematite, 2% by weight of coke, 0.5% by weight of silicon carbide and 55% by weight of coal ash were used. 9), the rotary kiln temperature was set to 1060
The aggregate j (Example 10), the aggregate k (Example 11), and the aggregate 1 (Example 12) were incinerated fly ash, respectively, in the same manner as in Example 1 except that the temperature was 1 ° C., 1100 ° C., and 1120 ° C. 57.5
Weight%, bentonite 5 weight%, hematite 5 weight%,
Aggregate m in the same manner as in Example 1 except that coke was 2% by weight, silicon carbide was 0.5% by weight and coal ash was 30% by weight.
Example 13 was obtained by incineration fly ash 72.5% by weight, bentonite 5% by weight, hematite 5% by weight, coke 2% by weight, silicon carbide 0.5% by weight, coal ash 10% by weight and quick lime 5% by weight. % In the same manner as in Example 1 except that
(Example 14) was obtained by incineration fly ash 28.5% by weight, bentonite 5% by weight, hematite 5% by weight, coke 2% by weight, silicon carbide 0.5% by weight, coal ash 20% by weight and quicklime 39% by weight And the rotary kiln temperature is 1120
Except for the temperature, the aggregate o (Comparative Example 1) was prepared by incineration fly ash 17.5% by weight, bentonite 5% by weight, hematite 5% by weight, coke 2% by weight, silicon carbide Aggregate p (Comparative Example 2) was prepared in the same manner as in Example 1 except that the weight was 0.5% by weight and 70% by weight of coal ash, and aggregate was obtained in the same manner as in Comparative Example 2 except that the rotary kiln temperature was 1140 ° C. q (Comparative Example 3) was obtained.

The same measurements as in Example 1 were performed on Examples 2 to 14 of the obtained aggregates b to n and Comparative Examples 1 to 3 of the aggregates o to q. The evaluation results and the respective aggregates b to q The results of calcium chemical analysis in terms of oxides in the medium are also shown in Table 1 below.

[0029]

[Table 1]

As can be seen from Table 1, the aggregates b to n of the embodiment are shown.
Has an absolute dry gravity of 1.17 to 1.90 and a crushing strength of 20 kg
f or more, while the water absorption is 0.7 to 10%,
The aggregate o of Comparative Example 1 having a calcium content exceeding 40% by weight has a low crushing strength of 15 kgf, and the aggregates p and q of Comparative Examples 2 and 3 have a crushing strength of 65 kgf or more. The addition rate is too high as 70% by weight, and the effective utilization rate of the refuse incineration ash decreases, which is not preferable.

[0031]

As described above, according to the present invention, it is possible to efficiently produce aggregate having high strength by using incineration ash as a main raw material. Therefore, it is extremely useful for environmental conservation and effective use of resources, since industrial waste can be recycled without being landfilled and treated, particularly for civil engineering and building materials.

Claims (6)

[Claims] 1. A garbage incineration ash is mixed or ground with a binder, a reducing agent and coal ash so that the calcium content is 40% by weight or less in terms of oxide, and water is added to mold the ash. A method for producing an artificial aggregate using refuse incineration ash, wherein the molded body is fired. 2. The method for producing an artificial aggregate using waste incineration ash according to claim 1, wherein a foaming agent is further added to said waste incineration ash. 3. The method for producing an artificial aggregate using waste incineration ash according to claim 1, wherein the molded body is dried and then fired. 4. The method for producing an artificial aggregate using refuse incineration ash according to claim 1, wherein the reducing agent is a carbonaceous material. 5. The method for producing an artificial aggregate using waste incineration ash according to claim 2, wherein said foaming agent is at least one of iron oxide and silicon carbide. 6. A method obtained by the method according to claim 1, which has an absolute dry specific gravity of 2.0 or less, a uniaxial compression breaking load of 20 kgf or more, and a water absorption of 10% or less. An artificial aggregate, characterized in that there is.