JPH1043716A - Stabilizing and fixing method of incineration ash of garbage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize and fix not only an EP ash but a general incineration ash by mixing general incineration ash with an aluminum phosphate cement, adding and kneading a hardening agent and water to the mixture, predrying the kneaded material and heating the dried material to obtain an inorg. hardened body. SOLUTION: When incineration ash of garbage is to be stabilized and fixed as an inorg. hardened body, a general incineration ash is mixed with an aluminum phosphate cement in a same amt. and then a hardening agent (aluminum oxide powder) by 10% of the aluminum phosphate cement and a little amt. of water to control the viscosity are added and kneaded to the mixture. The kneaded material is predried in a drying chamber at 80 deg.C for 30min, and then the kneaded material after predried is pulverized into <=300μm size. The pulverized material is supplied to fill a metal die, pressed in a hotpress and heated for each one hour at 80 deg.C, at 150 deg.C and at 200 deg.C. Then the pressed body released from the die is put in another drying container and heat treated at 300 deg.C for 2 hours to obtain a specified hardened body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for stably solidifying refuse incineration ash.

[0002]

BACKGROUND OF THE INVENTION Garbage from homes is disposed of in incineration facilities. This incineration produces a large amount of general incineration ash. Since general incineration ash contains little harmful metals,
It is buried as it is. However, from the viewpoints of scattering by wind, volume reduction during transportation, and recycling, it is necessary to stabilize and solidify. In addition, stabilization is necessary because the soil may be eluted by acidification of soil due to acid rain or the like. Of the incineration ash generated in the incinerator, EP ash collected by an electric dust collector contains a large amount of harmful heavy metals and the like, so that it is required to stabilize heavy metals contained in the ash.

As methods for stabilizing EP ash, there have been developed (1) a plasma melting method, (2) a concrete solidification method, and (3) a chemical treatment method. Already, these methods have been implemented in some municipalities. However, the plasma melting method of (1) requires enormous equipment costs and operation costs. In the concrete solidification method (2), there is a concern about stabilization. If the matrix is alkaline, there will be no leaching of metal, but if neutralization occurs, it will be more liable to dissolve in water and will not always be stable for a long time. The chemical treatment method (3) has problems in terms of long-term stability and heat resistance because the chemical itself is an organic compound. In addition, solidification is not possible even though stabilization is possible.
To solve these problems, the present inventors have disclosed a method of using aluminum phosphate as an agent for stably solidifying lead in EP ash (Japanese Patent Application No. 7-197507).

[0004]

In view of the above situation, it is considered that it is necessary to stabilize and solidify general incinerated ash in order to preserve the clean earth in the 21st century. It is an object of the present invention to provide a method for stably solidifying general incineration ash.

[0005]

Means for Solving the Problems General incinerated ash and aluminum phosphate cement are mixed, a hardening agent and water are added to the mixture, and the mixture is kneaded. It is a cured product.

[0006]

EXAMPLES In order to solidify general incineration ash, an inorganic binder or a chemical is required. As the inorganic binder, there are cement, water glass, gypsum, etc.
These have problems in any of heat resistance, water resistance, neutral deterioration, adhesiveness, mechanical strength and the like. But,
The aluminum phosphate cement satisfied these points. It has been found that this chemical can be an inorganic cured product having excellent heat resistance and water resistance at a firing temperature of 300 ° C.

[0007] In the case of producing an inorganic cured product from general incinerated ash and aluminum phosphate cement, the effects of preparation conditions such as blending, mixing time, and drying time on the mechanical strength of the cured product and the elution behavior of lead are examined. As a result,
It was found that it was possible to produce an inorganic cured product having high mechanical strength and no elution of lead, and it was possible to stably solidify general incinerated ash. Hereinafter, a preliminary study of the method for producing an inorganic cured product will be described, and then the method of the present invention will be described.

A. Preliminary Study on Production Method of Inorganic Hardened Material (1) Raw Material Aluminum phosphate cement is an inorganic high-viscosity binder obtained by adding a hardening agent to aluminum phosphate. There are various aluminum phosphate cements depending on the mixing ratio of phosphorus and aluminum. P / Al (P ₂ O ₅ / Al ₂ ) of aluminum phosphate cement applicable to the present invention
Molar ratio of O ₃ ) is 3.0 to 0.1. The characteristics of this drug are that the solution stability is high, and the workability does not change for a long time after kneading with the sample. General incineration ash was separated by sifting waste discharged from urban garbage disposal plants, and large solids such as cans were removed before use.

(2) Selection of curing agent The aluminum phosphate cement alone has a low curing rate even when heated to 50 ° C., and does not cure even after one day. On the other hand, when a hardener such as metal oxide is added,
Cures rapidly. The setting speed of the aluminum phosphate cement was adjusted by adding a hardening agent. As the curing agent, various basic substances, for example, aluminum oxide,
It was an inorganic compound powder such as aluminum hydroxide, zinc oxide, zinc hydroxide, magnesium oxide, calcium oxide, calcium hydroxide, and boron oxide. Others include asbestos, talc and fly ash. Therefore,
Calcium oxide, aluminum oxide,
Since it contains compounds such as silicon oxide, general incineration ash itself can also be a curing agent.

When the mixture of the aluminum phosphate cement and the hardener is heated to about 500 ° C. or higher, the reaction between the two proceeds and the hardener becomes more and more hard. At 1200 ° C. or higher, aluminum triphosphate is Al ₂ O ₃ .P ₂ O ₅ , which is an oxide having excellent fire resistance. Preliminary studies were conducted on the type and amount of hardener necessary for hardening the aluminum phosphate cement, and the blending amount of ash and cement.
A predetermined amount of a curing agent and water were added to the general incineration ash, and the mixture was thoroughly kneaded. Further, aluminum phosphate cement was added and stirred in the same manner as general incineration ash. The kneaded material was dried at room temperature for one day, heated to 300 ° C. at a rate of 50 ° C./min, and kept at the same temperature for 1 hour to form a cured product. The surface hardness, surface smoothness, etc. of the produced cured product were examined.

The setting speed of the aluminum phosphate cement was as follows: magnesium oxide> zinc oxide> boron oxide> calcium oxide> aluminum oxide. In the case of a cured product using magnesium oxide, zinc oxide, boron oxide, calcium oxide, or the like, there were many deformations such as expansion and cracking. Therefore, it was found that aluminum oxide was suitable for producing a dense cured product. Therefore, the subsequent examination was performed with aluminum oxide.

(3) Selection of Mixing The mixing of general incineration ash and aluminum phosphate cement for producing a hardened body is performed by putting the kneaded material of both into a mold,
It examined by the embedding method which pressurizes under a hot press. Aluminum phosphate cement (ash 1)
0, 50 and 100 parts). Next, aluminum oxide as a curing agent was added and kneaded at 4% of the amount of aluminum phosphate cement. The kneaded material was filled in a mold and heated to 100 ° C. in a dryer. After releasing from the mold, it was heated to 300 ° C. and kept at the same temperature for 1 hour to form a cured product. Bulk density and flexural strength (three-point flexural strength test method) of the prepared cured product
And Young's modulus were determined.

The incineration ash and the aluminum phosphate cement were prepared by changing the mixing ratio. The mechanical properties of the obtained cured product were affected by the amount of aluminum phosphate cement. When the amount of aluminum phosphate cement was 10 parts with respect to the amount of general incinerated ash, it did not cure. On the other hand, when the amount of aluminum phosphate cement is 50 parts,
Although cured, its strength was as low as 2.0 MPa. However, when the same amount of general incinerated ash and aluminum phosphate cemet was used, a cured product having a bending strength of 6.0 MPa was obtained. We decided to use the compounding ratio.

B. Production method of inorganic hardened material (1) Basic production method A mixture of general incineration ash and the same amount of aluminum phosphate cement, 10% curing agent (aluminum oxide powder) of aluminum phosphate cement and viscosity adjustment For this, a small amount of water was added and kneaded for 10 minutes. The kneaded material was preliminarily dried in a dryer at 80 ° C. for 30 minutes. The pre-dried kneaded material was pulverized to 300 μm or less, and a metal mold (2.0
cm-5.0 cm). Next, in hot press 3
80 ° C, 150 ° C, then 20 while pressing to 0MPa
It was kept at 0 ° C. for 1 hour each. Then, the pressurized material taken out of the mold is put into another dryer, and is heated at 300 ° C.
For 2 hours to produce a cured product.

(2) Effect on mechanical properties of pre-drying time of kneaded material Aluminum phosphate cement contains about 50% of unbound free water, and how efficiently this water can be used at low temperature It was important to remove. Therefore, a predetermined amount of a mixture of general incinerated ash, aluminum phosphate cement, aluminum oxide and water is kneaded for 10 minutes, and dried in an oven at 80 ° C. for a predetermined time (2 hours, 5 hours, 10 hours, 15 hours, 20 hours). Hours, 25 hours and 30 hours). Thereafter, a cured product was prepared by the method (1).

[0016] The bulk density and mechanical strength of the obtained cured product were greatly affected by the pre-drying time of general incinerated ash and aluminum phosphate cement. Table 1 shows the mechanical strength of the obtained cured product. The bulk density of the cured product was 1.7 g / cm ³ in each case. In addition, the bending strength of the cured body was about 2.0 MPa when the preliminary drying time was short,
After 15 hours or more, the pressure was remarkably high at 20 MPa. Further, the bending strength increases as the pre-drying time increases.
The maximum value was 3.0 MPa. As the pre-drying time was further increased, the bending strength gradually decreased.

[0017]

[Table 1]

(3) Influence on mechanical properties by kneading time of kneaded material In order to produce a cured product having high mechanical strength, general incinerated ash and liquid aluminum phosphate cement are mixed uniformly.
Or dispersed. Therefore, a certain amount of general incineration ash,
The kneaded product of aluminum phosphate cement, aluminum oxide, and water was stirred and stirred for a predetermined time (10 minutes, 30 minutes).
Minutes, 1 hour, 2 hours, 4 hours and 8 hours). Thereafter, a cured product was prepared by the method described in 2.3.
The preliminary drying time was set to 20 hours, and the kneading time was changed to produce a cured product. Table 2 shows the mechanical strength of the cured product with respect to the kneading time. When the kneading time was 10 minutes, the cured product had a bulk density of 1.6 g / cm ³ and a bending strength of 10.0 MPa.
When the kneading time was further increased and the treatment was carried out for 4 hours, the bulk density was increased to 1.8 g / cm ^3, and the bending strength exhibited the maximum value of 23.0 MPa. However, when the kneading was further performed, the bending strength of the cured product was reduced. The difference in mechanical strength was also observed in the structure of the fracture surface of the cured product. 1 kneading time
In the hardened body of 0 minutes, general incineration ash was aggregated, and poor dispersion or many voids were found in the fractured surface.
On the other hand, the fractured surface of the cured product having a kneading time of 4 hours showed a dense state with few voids.

[0019]

[Table 2]

C. Heavy Metal Leaching Test of Inorganic Hardened Material (1) Lead Leaching from General Incineration Ash Ash general incineration ash used in the experiment was discharged from an urban waste management plant. Add 10 parts of water to 100 parts of this general incinerated ash.
The amount of lead eluted in the aqueous solution after shaking for 30 minutes was measured. P of a solution obtained by shaking general incineration ash and water
H was 11.2, and the lead elution amount was 0.2 ppm. Since lead precipitates hydroxide under basic conditions, lead hardly eluted in the aqueous solution. Therefore, aqueous solutions of various pHs were prepared with nitric acid, and general incineration ash was put therein, and filtered 30 minutes later to determine the amount of lead in the filtrate. As a result, the pH when dispersed in water was 11.2, and the lead elution amount was 0.2 ppm. However, when the pH was adjusted by adding nitric acid, the lead elution amount increased. For example, at pH 3.5, 34.9 ppm and pH 2.
1 was 53.1 ppm and pH 1.5 was 54.1 ppm. However, the pH of the filtrate of the reaction product of the aluminum phosphate cement used in the present invention and general incineration ash shows 5 to 9, and depending on the selection of the curing agent and the curing conditions,
It was possible to suppress the elution of lead. On the other hand, the hardness of the solidified product of water and incinerated ash was so fragile that it easily collapsed when pressed with a finger.

(2) Method of solidifying general incinerated ash (part 1) Solidification of general incinerated ash with aluminum phosphate cement was performed as follows. General incinerated ash was separated by a standard sieve and used having a particle size of 0.5 mm to 5.0 mm. A prescribed amount of aluminum phosphate cement (0.1 part, 0.2 part, 0.5 part of general incinerated ash) is added to 20 grams of this general incinerated ash.
Parts and 1.0 part) and a curing agent (aluminum oxide or zinc oxide, 0.1 part of aluminum phosphate cement)
(0.2 parts and 0.3 parts). Water was added to these kneaded materials in an amount of 0.5 parts of general incinerated ash, and the mixture was stirred well while kneading. The mixture is placed in an evaporating dish and left at room temperature or
Using an electric furnace, each firing condition (heating rate 200 ° C / hour, firing temperature 50 ° C, 100 ° C, 200 ° C, 300 ° C
And a calcination temperature holding time of 30 minutes) to obtain a solidified product.

The solidified product was sieved to make the particle size of the solidified product within a predetermined value. To 1 part of this solidified product, add 10 parts of water, and shake 200 times per minute with a horizontal shaking width of 4 cm or more and 5 cm or less according to the Environmental Agency Notification No. 13 for metals contained in industrial waste. Under shaking conditions, shaking was performed for 6 hours. The mixed solution was filtered, and the lead content in the filtrate was measured using a high-frequency inductively coupled plasma emission spectrometer (manufactured by Jarrell Ash KK, ICA).
P-575).

The results of the dissolution test of the solidified product A at room temperature are shown in Table 3. The elution amount of lead when the aluminum phosphate cement was 10 parts or 20 parts with respect to 100 parts of general incineration ash sometimes exceeded the reference value (0.3 ppm) of the waste cleaning method.
However, when the amount of the aluminum phosphate cement was 50 parts or more, it did not exceed the reference value (0.3 ppm). Therefore, it is shown that 50 parts or more of aluminum phosphate cement is appropriate for 100 parts of general incinerated ash. Aluminum phosphate cement is an acidic compound. When the proportion of aluminum phosphate cement increases, the acidity of the solution increases, but the amount of lead eluted tends to decrease. It is considered that the lead in the solidified product does not exist in the form of ions or hydroxides but reacts with the aluminum phosphate cement. The lead elution amount when solidified at room temperature or at a sintering temperature of 100 ° C. or less is 0.4 ppm.
And 0.5 ppm. The elution amount of lead at a firing temperature of 200 ° C. was 0.2 ppm or more. The firing temperature of the reaction product of general incinerated ash and aluminum phosphate cement was suitably 200 ° C. or higher. A comparison was made between aluminum oxide and zinc oxide having a high curing rate as a curing agent, but no difference was observed in the curing and elution states of the two.

[0024]

[Table 3]

(3) Method for solidifying general incinerated ash (part 2) The general incinerated ash was separated from a particle size of 0.3 mm to 0.5 mm by a standard sieve. A curing agent (aluminum oxide, zinc oxide, magnesium oxide, calcium oxide, boron oxide, etc.) is added to 100 parts of the general incinerated ash.
05 parts), a mixture of aluminum phosphate cement and pure water (each 0.5 parts of general incineration ash) was added at a time, and mixed with an automatic stirrer for a predetermined period of time. And baked under the conditions described above to obtain a solidified product. The stirring time with the automatic stirrer is 5 minutes, 10 minutes, 30 minutes.
Minutes, 60 minutes, 120 minutes, and 180 minutes. The solidified material is
The particle size was reduced to 0.3 mm or less. This solid 1
Add 10 parts of water to each part, and shake 200 times a minute with a horizontal shaking width of 4 cm or more and 5 cm or less according to the Environment Agency Notification No. 13 "Testing Methods for Metals Contained in Industrial Waste". Shake for 6 hours under the conditions.

The solution subjected to the dissolution test by the above two methods is filtered, and the lead content in the filtrate is measured by using a high-frequency inductively coupled plasma emission spectrometer (Jarre Ash KK, IC
AP-575). The amount of lead eluted from the solidified material produced by changing the stirring time in the automatic stirrer was almost the same even when the stirring time was different. Various hardeners were added, and the amount of lead eluted was measured using a solidified material adjusted at a firing temperature of 100 ° C. The amount of lead elution when no hardener is added is
Although it was 0.4 ppm, the elution amount of lead when a hardening agent such as aluminum oxide, zinc oxide, magnesium oxide, calcium oxide and boron oxide was added was about 0.3 ppm or less in all cases. No difference in the amount of lead eluted by type was observed.

(4) Hot water elution test of hardened product of general incinerated ash and aluminum phosphate cement In order to examine the state of elution of lead in the hot water of the solidified product, 10 parts for 1 part of the solidified product Was added and left in a 60 ° C. constant temperature bath for a predetermined time (1, 10, and 20 days) to perform a thermal dissolution test. As a result, the liquid after the dissolution test showed pH 6.5 to pH 7.5 in all cases. The lead elution amount was 0.1 ppm or less in each case.

(5) Stabilization of Artificial Ash with Aluminum Phosphate Cement Components considered to be contained in general incinerated ash were artificially mixed to produce artificial ash. Its component ratio (weight ratio)
8.96 parts of calcium oxide, 7.01 parts of silicon oxide, 3.83 parts of aluminum oxide and 0.11 part of lead oxide. The lead concentration in this artificial ash was 498 ppm (theoretical value). A solid B was prepared from the artificial ash and the aluminum phosphate cement and subjected to a room temperature dissolution test. Stirring time is 10
For minutes, the curing agent was Al ₂ O ₃ . After shaking for 6 hours, the pH of the solution showed 12.0 or more. The lead concentration (theoretical value) in the artificial ash is 498 ppm.
The lead elution amount when left for 8 hours was 17.5 ppm. However, the amount of lead eluted from the product cured under the curing conditions of 100 ° C. to 400 ° C. was 0.1 ppm. From these facts, it was found that the lead in the general incinerated ash was solidified more stably by mixing and heating the general incinerated ash and the aluminum phosphate cement.

In summary, by mixing general incinerated ash and aluminum phosphate cement and heating to about 300 ° C., an inorganic hardened material having high mechanical strength and no lead elution could be produced and was solidified stably. (1) In the case of producing a cured product, if the particle size of the incinerated ash is large, the cured product is solidified and stabilized, but has a low strength. Desirably, the particle size is less than about 20 microns. (2) When producing a cured product, it was important to control the water removal rate of the aluminum phosphate cement as a binder. And when the particle size is fine and homogeneous, the mechanical strength of the cured product is affected by the pre-drying time at 80 ° C,
When the pre-drying time is about 20 hours, the bulk density is 1.
A cured product of 7 g / cm ³ and a flexural strength of 23.2 MPa was obtained. (3) Further, the mechanical properties of the cured product depend on the kneading time of the general incinerated ash and the aluminum phosphate cement, and show a maximum value after 4 hours, a bulk density of 1.7 g / cm ³ and a bending strength of 23 MPa. Was obtained. (4) In the dissolution test of the cured product, there was no dissolution of heavy metals such as lead.

[0030]

As described above, by mixing aluminum phosphate cement with general incinerated ash and heating, it is possible to produce a hardened inorganic material having high mechanical strength and from which heavy metals such as lead are not eluted. Can be stably solidified, so that a clean environment can be preserved.

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Claims (1)

[Claims] 1. An incinerated ash and an aluminum phosphate cement are mixed, a curing agent and water are added to the mixture, and the mixture is kneaded. The pre-dried kneaded material is heated to obtain an inorganic cured product. A stable solidification method for refuse incineration ash.