JP3084731B2 - Decomposition method of halogenated dioxins in incineration ash - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for decomposing halogenated dioxins in incinerated ash, and more particularly to a method for treating halogenated dioxins such as polychlorinated dioxin in incinerated ash at a low treatment temperature. The present invention relates to a method for decomposing halogenated dioxins in incinerated ash that can be decomposed.

[Prior Art] Dioxin is a compound having a skeleton in which two benzene nuclei are bridged by two oxygen atoms, and the substance name is dipenso paradioxin. Its chemical structural formula is as shown in the following [I].
The compound in which is substituted by Cl is dioxin chloride, and there are many isomers depending on the number and position of Cl. These isomers are collectively referred to as polychlorinated dioxins (PCDDs).

Polychlorinated dioxins (PPDDs) are highly toxic, such as carcinogenic and teratogenic. In particular, PCDDs having two chlorine atoms in both benzene nuclei, especially
In the above formula [I], 2,3,7,8-tetrachlorinated dioxins (TCDDs) having chlorine at the positions of,, and are the most toxic, and this substance is sometimes simply referred to as dioxin.

Further, a compound having a chemical structure similar to dioxin has two benzene nuclei as shown in the following [II].
There are dibenzofuran which is bridged by one oxygen atom and the other is directly bonded, and biphenyl which is directly bonded to two benzene nuclei as shown in the following [III].

Chlorinated products of these compounds also have the same severe toxicity as dioxin. In particular, polychlorinated biphenyls (PCBs) have been strictly regulated for use and emissions for more than 10 years due to their remarkable damage record. ing.

In recent years, since these halogenated dioxins have been detected in dust collected from incineration facilities and incinerated ash, establishment of a technology for decomposing and removing these has been regarded as important.

These halogenated dioxins are decomposed by heating. For example, TCDDs decompose at a high temperature of about 700 ° C. for 1 second. It is known that halogenated dioxins in ash decompose at a lower temperature when heated in a state where oxygen is restricted, than in normal heating.

[Problems to be Solved by the Invention] However, even when heating is performed in a state where oxygen is restricted, 600 ° C. is required for decomposition of halogenated dioxins.
Nearly high temperatures are required, and the necessity of such high-temperature decomposition is a difficult point for practical use.

An object of the present invention is to provide a method for decomposing halogenated dioxins in incinerated ash, which can decompose halogenated dioxins in incinerated ash at a lower temperature in view of the above-mentioned conventional circumstances.

[Means for Solving the Problems] The method for decomposing halogenated dioxins in incinerated ash of the present invention is a method for decomposing halogenated dioxins contained by heating incinerated ash while limiting oxygen. there is, the incinerator ash under pressure of 200~300kg / cm ² 400~4
Heat to 50 ° C.

In the present invention, examples of the halogenated dioxins include chlorides of dibenzoparadioxin including PCDDs such as the above-mentioned TCDDs, halogenated dioxins such as fluoride, and chlorides of dibenzoparadioxin such as fluoride. Halogenated compounds, such as halogenated biphenyls such as polychlorinated dibenzofurans (PCDFs) and PCBs, and halogen-substituted compounds of aromatic compounds in which two benzene nuclei are linked with or without oxygen are included.

 Hereinafter, the present invention will be described in detail.

In the present invention, while limiting oxygen incinerated ash, 200
Heated to a temperature of 400 to 450 ° C. under a pressure of ~300kg / cm ^2.
Upon this heating, the operating pressure is less than 200 kg / cm ^2,
Since sufficient low-temperature decomposability cannot be obtained, the operating pressure must be 200 to 300 kg / cm ^{2 in} consideration of low-temperature decomposability and equipment setting conditions.
And If the heating temperature is lower than 400 ° C., the decomposition efficiency is low, and if the heating temperature is higher than 450 ° C., the material of the apparatus is restricted, and the energy cost increases.

When incineration ash is filled into a reaction tube and heated under pressure, there is almost no supply of oxygen, and the supply of oxygen itself is restricted, so an operation to restrict oxygen is required separately. Will not be.

Specific methods for carrying out the method of the present invention include the following:
And the like, but it is needless to say that the present invention is not limited to these methods.

The incinerated ash is filled in a reaction tube having a pressurizing means such as a piston, and heated from outside the reaction tube by a heater or the like (external heating method).

The incinerated ash is filled into a ceramic reaction tube having a pressurizing means such as a piston, and a high frequency voltage is applied using the piston or the like as an electrode to perform high frequency dielectric heating of the incinerated ash (internal heating method).

The incineration ash is filled in a reaction tube having a pressurizing means such as a piston, a voltage is applied using the piston or the like as an electrode, and the incineration ash is energized and heated by electric resistance heat (internal heating method).

[Action] By pressurizing and heating the incinerated ash while limiting oxygen, the contained halogenated dioxins are efficiently decomposed at a low temperature. 400 kg / cm ² under pressure
Almost 100% decomposition rate can be obtained by heating at ℃.

Moreover, pressurization, heating, high solid material of 100 kg / cm ² or more compression strength is obtained, this solid material because it does not contain harmful substances on a high strength, it is possible to effectively utilize the roadbed material, etc. it can. Further, by using such a solidified body, the volume of incinerated ash can be reduced.

[Examples] Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples, and Reference Examples.

Example 1 250 g of municipal waste incineration ash was filled into a steel reaction tube having an inner diameter of 50 mm and a height of 100 mm, and was pressurized with a piston from above and below at 300 kg / cm ² by an external heating method using an electric heater. 1
Heat to the temperature shown in the table for 20 minutes, in each case PCDDs
Alternatively, the concentration of PCDFs was examined, and the results are shown in Table 1.

As is clear from Table 1, by heating under pressure, halogenated dioxins can be decomposed at a low temperature.

In Example 1, the pressing force was set to 300 kg / cm ² or 200 kg / cm ^2.
kg / cm ^2, and the heat treatment at 100, 200 or 300 ° C. for 20 minutes was conducted to examine the compressive strength of the solidified product. The results are shown in FIG.

From FIG. 1, it is clear that the higher the reaction temperature, the higher the strength of the solidified body can be obtained.

Comparative Example 1 The incinerated ash Nos. 1 to 5 having the halogenated dioxins content shown in Table 2 were heated at the temperature shown in Table 2 in a state where oxygen was restricted under normal pressure without pressurization. In the case of (1), the concentrations of PCDDs and PCDFs were examined, and the results are shown in Table 2.

As is apparent from Table 2, high-temperature heating at 590 to 600 ° C. is required to decompose halogenated dioxins by heating without applying pressure.

[Effects of the Invention] As described in detail above, according to the method for decomposing halogenated dioxins in incineration ash of the present invention, halogenated dioxins in incineration ash are decomposed at a lower heating temperature than before. Which is extremely industrially advantageous. Moreover,
Pressurization and heating can reduce the volume of the incinerated ash, and a high-strength solidified body can be obtained, so that the incinerated ash can be effectively used.

[Brief description of the drawings]

 FIG. 1 is a graph showing the results of Reference Example 1.

Claims (1)

(57) [Claims] 1. A method for decomposing halogenated dioxins contained in incinerated ash by heating the incinerated ash while limiting oxygen, wherein the incinerated ash is heated under a pressure of 200 to 300 kg / cm ² . A method for decomposing halogenated dioxins in incinerated ash, wherein the method comprises heating to 400 to 450 ° C.