JP3303251B2 - How to treat incinerated ash - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating incinerated ash, and more particularly, to the elution of heavy metals when incinerated ash including fly ash discharged from municipal solid waste incineration facilities is used for landfill. The present invention relates to a method for treating incinerated ash that can be prevented.

[0002]

2. Description of the Related Art Incineration fly ash discharged from refuse incinerators is
It is designated as dust of special management municipal waste, and its intermediate treatment methods include (1) stabilization treatment of heavy metals by melting and solidification,
(2) Stabilization of heavy metals by solidification of cement, (3)
Four methods of stabilization of heavy metals by chemical treatment and (4) stabilization of heavy metals by acid extraction are specified, and stabilization of heavy metals by chemicals is used in a relatively wide range.

[0003] However, the stabilization treatment of heavy metals by chemicals involves treating alkaline fly ash sprayed with slaked lime or the like in a flue to treat hydrogen chloride in exhaust gas. , The heavy metal, for example, lead (Pb) is easily eluted,
In order to suppress this, a large amount of drug is required, or it is necessary to separately add a pH adjuster, and there is a problem that running costs increase.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, to reduce the amount of chemicals used, and to effectively confine heavy metals to reduce the amount of incinerated ash. Is to provide a processing method.

[0005]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive studies on the relationship between the method of stabilizing heavy metals by chemical treatment of incinerated ash and the amount of heavy metal eluted after the treatment. Heating the incinerated ash before adding the agent at a predetermined temperature reduces the amount of heavy metal eluted, and further reduces the amount of heavy metal eluted by adding and kneading the heavy metal and then press forming. And arrived at the present invention.

That is, the invention claimed in the present application is as follows. (1) Heating the incinerated ash at 400 to 550 ° C. to cause a reaction between carbon dioxide gas generated by burning unburned carbon in the incinerated ash and an alkali component in the incinerated ash. A method for treating incinerated ash, comprising adding a fixing agent and water, kneading the mixture, and solidifying the mixture. (2) The method for treating incinerated ash according to the above (1), wherein the mixture is kneaded by adding a heavy metal fixing agent and water and then kneaded.

[0007]

FIG. 1 and FIG. 2 are explanatory views showing the principle of the present invention. FIG. 1 shows a leaching test after heat treatment of fluidized bed municipal solid waste incineration fly ash with a heat dechlorination apparatus (Die Breaker). Is a graph showing the relationship between the heat treatment temperature and the pH of the eluate at the time of carrying out the above. The heating time is 15 minutes after reaching the predetermined temperature. In the figure, the incineration fly ash is 400
By performing the heat treatment at a temperature of 550 ° C. or more, the pH of the eluate is decreased by 1 or more, and it is found that heavy metals in the ash are hardly eluted. This is because the alkali component in fly ash is carbonated by carbon dioxide gas generated by burning unburned carbon or the like by heat treatment, thereby lowering the pH of the eluate. Therefore, it is considered that the pH of the eluate is maintained in a range in which the heavy metal is stabilized, and the heavy metal is fixed, for example, as a stable hydroxide.

FIG. 2 shows that the fluidized bed municipal solid waste incineration fly ash is heated at 450 ° C. for 15 minutes, added with 1% by weight of a chelating agent as a heavy metal fixing agent, kneaded, and then subjected to compression molding. Cadmium (Cd) which is pressure and heavy metal
The figure shows the relationship with the amount of eluted. The dissolution test was performed in accordance with the Notification of the Environment Agency No. 13, and hydrochloric acid was added to pure water as a solvent and the pH was adjusted to 5.8 to 6.3. The particles adjusted to a particle size of 5 mm were mixed so that the weight / volume ratio became 10%, and the mixture was shaken continuously for 6 hours to detect cadmium (Cd) in the solvent after the test was completed. In the figure, Cd
It can be seen that the elution amount of was surely reduced, and the elution amount was reduced as the compression pressure was increased.

That is, according to the present invention, as shown in the processing flow of FIG. 3, incineration ash before chemical treatment is preheat-treated and dechlorinated, and then a heavy metal additive and water are added and kneaded. Molding or compression molding.
In the present invention, the heating temperature for heat-treating the incinerated ash is 400 to 550 ° C, preferably 420 to 460.
° C. If the heating temperature is too low, the pH decrease of the eluate is small and the effect of suppressing the elution of heavy metals is reduced. On the other hand, if the heating temperature is too high, energy is lost and running costs are increased. Further, the heating time is 1 to 30 minutes after reaching the predetermined temperature, preferably 5 to 15 minutes If the heating time is too short, the effect of suppressing the elution of heavy metals is not obtained, if too long, the running cost is reduced. Bulky. The apparatus for heating the incinerated ash is not particularly limited.
Vertical continuous heating device, horizontal heating device, as shown in
A known device such as a rotary kiln type heating device is used.

In the present invention, the pressure at the time of pressure molding is not particularly limited, but is preferably, for example, 10 to 30 Mpa.
In the present invention, it is not necessary to use a solidifying agent such as cement, because the molding and solidification can be performed using the hydraulic component in the fly ash.

[0011]

Next, the present invention will be described in more detail by way of examples. Example 1 Fluid-bed municipal solid waste incineration fly ash having the composition shown in Table 1 was heated at 450 ° C. for 10 minutes using the vertical continuous heating apparatus shown in FIG. 5, and then 1 to 5 chelating agents were used as heavy metal fixing agents. weight%
And 10% by weight of water and kneaded for 5 minutes, and then compression molded at 30 MPa using a compression molding machine to obtain a fly ash molded product.

[0012]

[Table 1] Example 2 The same fly ash kneaded material was obtained in the same manner as in Example 1 except that compression molding was not performed (only kneading).

Comparative Example 1 The same fly ash mixture was obtained in the same manner as in Example 2 except that no heat treatment was performed. 100 g of each of the fly ash molded products obtained in Examples 1 and 2 and Comparative Example 1 was collected, and hydrochloric acid was added to pure water to adjust the pH to 5.8 to 6.3. The dissolution test was performed by shaking for 6 hours according to the method, and Pb eluted in the solvent was quantified. FIG. 4 shows the results.

In the figure, the fly ash molded product of Example 1 which was subjected to heat treatment and compression molding in addition to chemical treatment was lead (Pb).
It can be seen that the amount of heavy metal fixing agent used to clear the target value of Pb elution amount of 0.3 mg / liter is only slightly less than 1%. Further, the fly ash kneaded product of Example 2 which was not subjected to the heat treatment and compression molding required 1-2% of the heavy metal fixing agent to achieve the reference value of the Pb elution amount. On the other hand, the fly ash kneaded material of Comparative Example 1 by the conventional chemical treatment method in which neither the heat treatment nor the compression molding was performed was 3% in order to achieve the reference value.
The above heavy metal fixing agent was required.

[0015]

According to the invention of claim 1 of the present application, the incinerated ash before adding the heavy metal fixing agent is 400 to 400 in advance.
By heat treatment at 550 ° C, it can be molded and solidified well without adding a solidifying agent such as cement from the outside, and even if the amount of heavy metal fixing agent used is reduced, metal elution in the fly ash molded product The amount can be effectively reduced to stably confine heavy metals for a long time. By performing the heat treatment, harmful organic chlorine compounds such as dioxin can be effectively decomposed and removed.

According to the invention as set forth in claim 2 of the present application, in addition to the heat treatment, a heavy metal fixing agent is added and kneaded, followed by compression molding, whereby the heavy metal is physically confined. In addition, heavy metals can be stabilized with less heavy metal fixing agents.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing the principle of the present invention.

FIG. 2 is an explanatory diagram showing the principle of the present invention.

FIG. 3 is a diagram showing a processing flow of the present invention.

FIG. 4 is a diagram showing the effect of the embodiment of the present invention.

FIG.

FIG.

FIG. 7 is a diagram showing a heating device used in the present invention.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F23J 1/00

Claims (2)

(57) [Claims] An incinerated ash is heated at 400 to 550 ° C. to react carbon dioxide gas generated by burning unburned carbon in the incinerated ash with an alkali component in the incinerated ash.
A method for treating incinerated ash, comprising adding a heavy metal fixing agent and water to the reaction product, kneading the mixture, and solidifying the mixture. 2. After adding a heavy metal fixing agent and water and kneading,
2. The method for treating incinerated ash according to claim 1, wherein the incineration ash is formed by pressure molding.