JP3415066B2 - Manufacturing method of solidified waste incineration ash - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to municipal waste, industrial waste, and RDF (Refuse Derived Fue).
Solid waste solid ash and / or waste incineration fly ash (hereinafter collectively referred to as "waste incineration ash" or "incineration ash") generated when incinerating waste such as waste solid fuel) The present invention relates to a method of manufacturing.

[0002]

2. Description of the Related Art Waste incineration ash, especially Pb for incineration fly ash,
It contains a large amount of heavy metals such as Cd and cannot be directly landfilled. As specially controlled general waste, it is obliged to perform an intermediate treatment by melt solidification, cement solidification, chemical (chelate) treatment, or solvent extraction. However, for example, in the chemical treatment, an expensive chelating agent requires about several% of the ash to be treated, and in the melt treatment, equipment cost and a lot of energy are required, and these intermediate treatment methods require waste treatment cost. It is a factor of increase. Therefore, as an inexpensive heavy metal containment method that does not use chelating agents or cement, there is a method of adding fine blast furnace granulated slag powder with a Blaine value of 4000 cm ² / g or more and lime to fly ash and solidifying in the presence of water. Proposed (for example, Japanese Patent Laid-Open No. 9-10014).
No. 6 publication).

However, even if these methods are used alone or in combination, the elution of heavy metals from the solidified incinerated ash is such that the landfill standard is satisfied. Furthermore, a method for producing a solidified body by adding an additive such as cement or slaked lime to the incinerated ash for the effective use of the incinerated ash and performing a room temperature curing or a steam curing is also known. Although the elution of Cd and Se can be suppressed, the elution amount of Pb increases and the landfill standard is satisfied, but it is difficult to satisfy the soil environmental standard required for effective use.

[0004]

In the method for producing a solidified body using a calcium material such as cement or slaked lime or granulated blast furnace slag as an additive, as described above, a large amount of Pb is eluted from the solidified body. Although the landfill standard is satisfied, it is very difficult to satisfy the soil environmental standard required for effective use. In the above conventional method, when the amount of the additive is increased, the strength of the solidified product is increased, but the pH of the eluate from the solidified product is increased, the amount of Pb eluted is increased, and the soil environmental standard cannot be satisfied. I found out from the tests I conducted. Then, as a result of examining the elution of the heavy metal from the solidified body produced from the incinerated ash, it was found from the test conducted by the present inventor that the elution amount of Pb increases as the pH of the eluate increases (details will be described later). (See FIGS. 3 and 4).

Therefore, the eluate from the solidified body by the conventional method often has a high pH (12 or more), and therefore, the elution amount of heavy metals, especially Pb, is large, and the soil environmental standard may be satisfied. The inventor inferred that it was not possible.
Here, the production of a solidified product from incinerated ash is generally carried out by adding an additive and a proper amount of water to the combustion ash and kneading the mixture, and using hydrothermal reaction. Since it is necessary that the components once dissolve and reach a saturation concentration or higher, the pH of the kneaded product should be adjusted when the ash contains a small amount of alkaline components.
It is necessary to add an alkaline component as an additive so that the ratio is about 12.6 or more. However, the pH of the eluate from the solidified body produced in this way is often high (about 12 or more), which means that the alkaline component (mainly calcium component) in the ash and the alkaline component added as an additive are It is considered that CaO liberated by hydrothermal reaction and CaO liberated by the hydrothermal reaction elute in the eluate, and thus it is difficult for the elution amount of Pb to satisfy the soil environmental standard.

Therefore, as a result of various tests and studies, the present inventor has found that substances containing SiO ₂ as an additive, especially S.
By adding a fine substance containing iO ₂ , such as silica fume, CaO or the like remaining in the solidified body due to liberation etc. reacts with this SiO ₂ to produce a C-S-H gel, thereby solidifying the solidified body. The pH of the eluate from E. coli is suppressed to a low level, the elution of Pb is suppressed, the strength of the solidified body is increased by the formation of C-S-H gel, and the reaction is carried out by autoclave treatment under a saturated steam pressure. It was further found that the pH of the eluate was further accelerated and the elution of Pb was suppressed. Further, as a measure of amount of material containing SiO _2, the basicity of the mixture ash (CaO / SiO ₂ mol
As a result of examining the relationship between the ratio) and the pH of the eluate, the basicity was 0.8
By adjusting the pH of the eluate to the following, the Pb content is 1500 pp
pH of ash of m that can almost meet the soil environmental standard 11.
It turned out that it can be about 05 (details are described in Fig. 5 below).
(See FIGS. 6 and 7).

The present invention has been made on the basis of the above findings, and an object of the present invention is to use an expensive chemical agent such as a chelating agent, cement for solidification and a large amount of energy as in the conventional method. It is an object of the present invention to provide a method capable of inexpensively producing a high-strength waste incineration ash solidified body in which the amount of heavy metals such as Pb, Pb and the like dissolved out of soil environmental standards and which can be effectively used as a civil engineering material.

[0008]

In order to achieve the above object, the method for producing a solidified body of waste incinerated ash according to the present invention comprises a hydrothermal solidification reaction by adding an alkaline agent to the waste incinerated ash as an additive. When producing a solidified product by utilizing, the pH of the eluate from the obtained solidified product is 11.5 or less, preferably 11.0.
To so that is follows Do Ri elution Pb is suppressed, in addition to the alkali agent as an additive, silica fume, coal ash, silica sand,
It is configured to add slag, clay and / or dredging sludge . When the pH of the eluate exceeds the above value, the elution amount of Pb increases and the soil environmental standard is not satisfied. The lower limit of the pH of the eluate is not particularly limited, but it is about 10 if it is strongly limited.

In the method of the present invention, an alkaline agent is added as an additive to waste incineration ash, and when a solidified body is produced by utilizing a hydrothermal solidification reaction, the basicity in the incineration ash, that is, CaO / SiO 2 is used. _The molar ratio of ₂ is 1.0 or less, preferably 0.
8 follows Do pH of the eluate I is lowered Pb elution suppression of
To so that is, in addition to the alkali agent as an additive, silica
Of fume, coal ash, silica sand, slag, clay and dredging sludge
It is characterized by adding at least one of them . When the basicity exceeds the above value, the pH value of the eluate increases, the amount of Pb elution increases, and the soil environmental standard is not satisfied. The lower limit of the basicity is not particularly limited, but it is about 0.4 if strongly limited.

In these methods, in addition to alkaline agents as additives , silica fume, coal ash, silica sand and slurry are added.
After adding at least any one of clay, clay and dredging sludge and kneading, 80-250 ° C, preferably 100-
Steam curing is preferably performed at 250 ° C, more preferably 150 to 200 ° C. In this case, it is preferable to use an autoclave or the like. When the steam curing temperature is lower than the above lower limit, the reaction between CaO and the like and SiO ₂ does not proceed sufficiently and the released CaO and the like remain in the solidified body.
There is an inconvenience that the pH cannot be suppressed to a low level. On the other hand, when the pH exceeds the above upper limit, there is an inconvenience that the cost of the processing device, energy and the like becomes excessive with respect to the intended effect. As the alkaline agent, at least one of slaked lime, quick lime, limestone, gypsum, steel slag and cement is used. As the substance containing SiO ₂ , as described above , at least one of silica fume, coal ash, silica sand, slag, clay and dredging sludge is used. In this case, it is preferable to use a fine substance containing SiO ₂ , such as silica fume.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments, and can be appropriately modified and implemented. FIG. 1 shows a process chart of a method for producing a solidified waste incineration ash according to a first embodiment of the present invention. Waste incineration ash, an alkaline agent, a substance containing SiO ₂ and water are supplied to a kneader and kneaded. These may be supplied to the kneading machine separately, or may be supplied to the kneading machine in a state where two or more kinds are mixed in advance. The kneaded product is introduced into a molding machine (for example, a mold molding machine) to be molded, then pre-cured in a pre-curing chamber, and then demolded. The demolded pre-cured organism is steam-cured in the main curing room to become a solidified body. Further, the solidified body may be crushed by a crusher to form a crushed stone-like solidified body. A solidified body manufacturing apparatus (hydrothermal solidification reaction apparatus) is constituted by these series of apparatuses. It should be noted that it is possible to omit the molding step and the demolding step, omit the pre-curing step, add a granulation step, a pressure molding step, or the like. By curing the kneaded material, ettringite (3CaO ・ Al ₂ O ₃・ 3CaSO) is formed by hydration solidification reaction (hydrothermal solidification reaction).
₄ · 32H ₂ O), C—S—H (calcium silicate hydrate), etc. are generated and solidified to be a solidified body by a hydration reaction (hydrothermal reaction). Then, it is crushed if necessary. The obtained solidified body is stable and has high strength, and
Since the elution amount of heavy metals such as Pb is small and the soil environmental standard is satisfied, it is effectively used as a civil engineering material such as a roadbed material and a construction material.

[0012]

EXAMPLES Examples and comparative examples will be shown below to further clarify the features of the present invention. Examples 1 to 3 and Comparative Examples 1 and 2 Tests were performed using RDF incineration fly ash. Fly ash used (R
Table 1 shows the properties of DF fly ash 1 and RDF fly ash 2).

[0013]

[Table 1]

Slaked lime as an alkaline agent to these fly ash,
As shown in Table 2, silica fume as the SiO ₂ source,
An appropriate amount was added, and as shown in FIG. 2, water was added to the mixture and kneaded, and then the mixture was put into a mold and molded, and pre-cured and main-cured to obtain a solidified body. The pre-curing was performed at 40 ° C, and the main curing was performed at 95 ° C and 180 ° C (using an autoclave) with steam. Further, the molding of the mold after kneading is performed for the sake of convenience of the test, and granulation, pressure molding and the like can be used in addition to this, and there is no limitation. The results are shown in Table 2. Fig. 3 shows the relationship between compressive strength and eluate pH.
FIG. 4 shows the relationship between the pH of the eluate and the amount of Pb eluted, FIG. 5 shows the relationship between the basicity and the pH of the eluate, and FIG. 6 shows the relationship between the basicity and the amount of Pb eluted. Further, the amount of Pb elution due to the change in basicity was measured for the ash containing 1500 ppm Pb and the ash containing 900 ppm Pb, and the results are shown in FIG. 7.

[0015]

[Table 2]

From FIGS. 3 and 4, the same strength, for example, 10
At 0 kgf / cm ² , the pH of the eluate from the solidified bodies according to Examples 1 to 3 in which silica fume was added and subjected to autoclave curing was low, and as a result, the elution of Pb was suppressed and the soil environmental standard was 0. Satisfies less than 0.01 mg / l,
Or almost satisfied. The amount of Pb eluted varies depending on the amount of Pb contained in the fly ash. Next, using RDF fly ash 2, only slaked lime was added and steam curing was performed at 95 ° C, and slaked lime and silica fume were added to adjust the basicity to 0.
Comparing the cases where it was set to 8 or less and further cured by autoclave, the pH of the eluate from the solidified body by this method was 11
Below, the amount of Pb eluted was below the measurement limit. Furthermore, the compressive strength was over 250 kgf / cm ² . The eluate was prepared in accordance with Notification No. 46, and the compressive strength was measured by using an Amsra tester, and the average value of the measured values of three simultaneously prepared solidified products was adopted.

[0017]

Since the present invention is configured as described above, it has the following effects. (1) The elution amount of heavy metals such as Pb satisfies the soil environmental standard without requiring expensive chemical agents such as chelating agents as in the prior art, cement for solidifying or a large amount of energy, and civil engineering materials, etc. It is possible to inexpensively produce a high-strength waste incineration ash solidified body that can be effectively used. (2) When kneading and then steam curing at 80 to 250 ° C., the reaction is further promoted, the pH of the eluate is further lowered, and the elution of heavy metals such as Pb is further suppressed.

[Brief description of drawings]

FIG. 1 is a process diagram showing a method for producing a solidified waste incineration ash according to a first embodiment of the present invention.

FIG. 2 is a process diagram showing a method for producing a solidified waste incineration ash in Examples and Comparative Examples.

FIG. 3 Compressive strength and eluate pH in Examples and Comparative Examples
It is a graph which shows the relationship with.

FIG. 4 is a graph showing the relationship between the pH of the eluate and the amount of Pb eluted in Examples and Comparative Examples.

FIG. 5 is a graph showing the relationship between basicity and eluate pH in Examples and Comparative Examples.

FIG. 6 is a graph showing the relationship between basicity and Pb elution amount in Examples and Comparative Examples.

FIG. 7 Ash with Pb content of 1500 ppm and Pb content 9
It is a graph which shows the relationship between the basicity and the Pb elution amount in ash of 00 ppm.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-108649 (JP, A) JP-A-10-66947 (JP, A) JP-A-9-235147 (JP, A) JP-A-56- 161880 (JP, A) JP-A-10-28950 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B09B 3/00 301-304 C04B ^7/ 24-7/28 C04B 18 / 06-18/08

Claims (4)

(57) [Claims] 1. When an alkali agent is added to waste incineration ash as an additive to produce a solidified product utilizing a hydrothermal solidification reaction, the pH of the eluate from the obtained solidified product is 11.5 or less. in so that <br/> elution-than Pb is suppressed, in addition to the alkali agent as an additive, silica fume, coal ash, silica sand, Sula
A method for producing a solidified waste incineration ash, which comprises adding at least any one of slag, clay and dredging sludge . 2. A basicity in the incinerated ash, that is, a CaO / SiO ₂ molar ratio is 1. when an alkali agent is added to the waste incinerated ash as an additive to produce a solidified body by utilizing a hydrothermal solidification reaction. 0 soluble below pH of the eluate I Do and decreases Pb
In so that the out suppressed, in addition to the alkali agent as an additive, silica fume, coal ash, silica sand, slag, clay and
A method for producing a solidified waste incineration ash, which comprises adding at least one of dredging sludge . 3. Silica as an additive in addition to the alkaline agent
Of fume, coal ash, silica sand, slag, clay and dredging sludge
After adding at least one and kneading, 80-
The method for producing a solidified waste incineration ash according to claim 1 or 2, wherein steam curing treatment is performed at 250 ° C. 4. The method for producing a solidified waste incineration ash according to claim 1, 2 or 3, wherein the alkaline agent is at least one of slaked lime, quick lime, limestone, gypsum, steel slag and cement .