JP2001294846A - Agent and method for decomposing dioxins - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an agent for decomposing dioxins capable of carrying out decompositions of dioxins in a low-temperature range which has been regarded as impossible, and to provide a method for decomposing dioxins. SOLUTION: This agent for decomposing dioxins is characterized by comprising a peroxodisulfate represented by general formula (I) M2S2O8 (M is ammonium or a metal) (I). This method for decomposing dioxins is characterized by bringing the agent for decomposing dioxins into contact with dioxins or a substance containing dioxins.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dioxin decomposer and a method for decomposing dioxins, and more particularly to fly ash and incinerated ash discharged from various incinerators such as refuse incinerators. Ash)) contained in poly-chlorinated-p-dibenzodioxins (PCDD), polychlorinated dibenzofurans (PCDF), coplanar-PCB
The present invention relates to a decomposition agent and a decomposition method for efficiently decomposing organic chlorine compounds such as (co-PCB) (hereinafter, these are collectively referred to as “dioxins”).

[0002]

2. Description of the Related Art In an incinerator such as a refuse incinerator, dioxin precursors such as organic compounds such as phenol and benzene and chlorinated aromatic compounds such as chlorophenol and chlorobenzene are generated during combustion. When fly ash is present, these dioxin precursors are converted into dioxins by catalytic action and are present in the incinerated ash.

Conventionally, the following method has been proposed as a method for treating such fly ash containing dioxins.

(1) Dioxin-containing fly ash is subjected to 340 ° C. for 2 hours at 320 ° C. in a reducing atmosphere such as nitrogen gas.
A method for decomposing dioxins by holding for 1 to 1.5 hours (Hagenmeier process: Organoha
logen Compound, 27, 147-152 (1996), JP-A-64-5
00320).

(2) Dioxin-containing fly ash is removed in the presence of a dioxin generation inhibitor (pyridine) by 300 to 5
Heat treatment at 00 ° C. (JP-A-4-241880).

Conventionally, dioxins are not considered to be thermally decomposed below 300 ° C., and the above-mentioned method decomposes dioxins by heating to 300 ° C. or higher, according to this established theory. During the treatment, a dioxin generation inhibitor is added to the fly ash in the dioxin decomposition temperature range in order to suppress the generation of dioxins from the dioxin precursor.

[0007]

However, the above-mentioned conventional method has the following problems.

(A) Since the processing temperature is high and the processing time is long, much energy is required and the processing cost is high.

(B) Dioxins may be resynthesized upon cooling.

(C) Although it is necessary to perform the treatment in a reducing atmosphere such as nitrogen gas, the oxygen cannot be completely shut off.
The decomposition rate of dioxins decreases.

(D) Since the dechlorination reaction partially proceeds,
More toxic dioxins are produced.

The present invention solves these problems of the conventional method, and can decompose and remove dioxins in a short time even in a low temperature range where it was considered that dioxins could not be decomposed by the conventional method. Is, even in the presence of oxygen,
An object of the present invention is to provide a dioxin decomposer and a decomposition method capable of decomposing dioxins efficiently.

[0013]

In order to achieve the above object, the present invention provides a compound represented by the following formula I:

[0014]

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[0015] The present invention relates to a dioxin decomposer, comprising a peroxodisulfate represented by the formula (wherein M represents ammonium or a metal). The present invention also relates to a method for decomposing dioxins, which comprises contacting the dioxin decomposer with a dioxin or a substance containing dioxins.

[0016]

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, a chlorine atom in a dioxin and a dioxin-containing substance are contacted with a dioxin decomposing agent containing a peroxodisulfate of the formula I to thereby convert a chlorine atom in the dioxin into a compound of the formula I Reacts with the peroxodisulfate, and the dechlorination reaction of the dioxins or the cleavage reaction of the six-membered ring (benzene ring) proceeds rapidly to decompose the dioxins.

The dioxin decomposer according to the present invention may use only one peroxodisulfate of the formula I or a combination of two or more thereof. In the dioxin decomposer according to the present invention, the peroxodisulfate of the above formula I may be supported on a carrier. Carriers that can be used, for example, silica, alumina,
Examples include zeolite, diatomaceous earth, activated carbon, and the like. By supporting the peroxodisulfate of the formula I on such a carrier, a catalytic effect of the decomposition of dioxins by such a carrier is expected, and it becomes possible to decompose dioxins more efficiently.

According to the present invention, the chlorine in the dioxins reacts with the peroxodisulfate of the formula I,
Dioxins are not considered to be decomposed by the conventional method 3
At a temperature lower than 00 ° C., the dechlorination reaction of the dioxins or the cleavage reaction of the six-membered ring (benzene ring) proceeds rapidly, and the dioxins are decomposed.

Further, by contacting the dioxin decomposing agent according to the present invention with a dioxin or a dioxin-containing substance under a pressurized condition, the dioxins can be decomposed at a lower temperature.

In the present invention, the term "dioxin-containing substance" refers to an exhaust gas discharged from various incinerators such as a garbage incinerator or a factory incinerator, an incineration ash adsorbed with dioxins, and a dioxin adsorption treatment. Powdered activated carbon and soil contaminated with dioxins.

When the dioxin decomposing agent according to the present invention is decomposed by contacting it with incinerated ash or collected fly ash, the peroxodisulfate of the formula I is converted into incinerated ash or collected ash. 0.1 to 10% by weight based on the fly ash
In particular, it is preferable to make contact at a ratio of 1 to 5% by weight.

The collected fly ash may contain powdered activated carbon blown into the flue of the incinerator as an adsorbent for dioxins in the exhaust gas from the incinerator.

The form of contacting the dioxin decomposer according to the present invention with a dioxin or a dioxin-containing substance may be any of gaseous, liquid and aqueous solutions. However, when a dioxin or a dioxin-containing substance is brought into contact with a gaseous dioxin decomposing agent according to the present invention, the dioxins are most efficiently decomposed.
Those having a sufficiently high vapor pressure at temperatures below 0 ° C. are preferred. Further, when the dioxin decomposer according to the present invention in the form of a liquid or an aqueous solution is sprayed on the exhaust gas, or in the case where the dioxin is kneaded with incineration ash or the like in advance, the dioxin decomposing agent becomes sufficiently gaseous at a temperature lower than 300 ° C. Those having a vapor pressure are preferred. Specific examples of preferred peroxodisulfate of the formula I include ammonium or alkali metal peroxodisulfate.

When the dioxin-containing substance is soil, incineration ash, collected fly ash, or the like, the method for contacting the dioxin-decomposing agent according to the present invention with the dioxin-containing substance is as follows. A method can be adopted.

A. The dioxin-containing substance and the dioxin decomposer according to the present invention are mixed and brought into contact at room temperature. Alternatively, the mixture is heated to a temperature lower than 300 ° C. to gasify the dioxin decomposer and contact the dioxin. In these cases, the dioxin decomposer according to the present invention may be dissolved in water or another solvent.

B. The dioxin decomposing agent according to the present invention is gasified by heating to a temperature lower than 300 ° C., and an air stream containing this gas is brought into contact with the dioxin-containing substance.

C. The dioxin decomposer according to the present invention is supported on a carrier such as silica, alumina, zeolite, diatomaceous earth or activated carbon, and the supported decomposer is mixed with a dioxin-containing substance or placed on a dioxin-containing substance. To a temperature lower than 300 ° C.

In the case where heating is performed under pressurized conditions, the above temperature may be lower.

When the dioxins and the dioxin-containing substances are present in a gaseous state or in the form of particles and suspended in an air stream such as combustion exhaust gas, the dioxin-decomposing agent according to the present invention and the dioxin The following method can be adopted as a method of bringing the substance into contact with the class-containing substance. D. A vapor containing peroxodisulfate of the formula I or a gas containing the vapor is supplied to a gas stream containing dioxins or a substance containing dioxins. E. FIG. The peroxodisulfate of formula I is supplied in the form of a mist or droplets into an air stream containing dioxins or a substance containing dioxins. F. A solution obtained by dissolving a peroxodisulfate of the formula I in an air stream containing dioxins or a dioxin-containing substance,
Supplied in mist or droplet form.

In a combustion facility in which a dust collector for collecting fly ash in exhaust gas is provided in an exhaust gas flue, a gaseous, liquid or aqueous solution is stored in the exhaust gas flue or dust collector in front of the dust collector. It is preferable to supply a dioxin decomposer according to the present invention in the form of In a normal case, the gas temperature at the dust collector inlet of the electric dust collector is about 200 to 230 ° C., and the gas temperature at the dust collector inlet of the filtration type dust collector is 140 to 200 ° C.
Since the temperature is about ℃, it is preferable to supply the dioxin decomposer according to the present invention to the dust collector or the flue upstream of the dust collector.

Usually, dioxins are not decomposed at a temperature lower than 300 ° C. In the present invention, surprisingly, the dioxins can be decomposed by contacting the dioxins or the dioxin-containing substance with the dioxin decomposing agent according to the present invention at a temperature lower than 300 ° C. . When the dioxin decomposing agent according to the present invention is brought into contact with a dioxin or a dioxin-containing substance, chlorine in the dioxins reacts with the peroxodisulfate of the formula I,
Dechlorination of dioxins or six-membered ring (benzene ring)
Cleavage reaction proceeds rapidly, and dioxins are decomposed. The minimum temperature during this contact is determined by the vapor pressure or the ease of vaporization of the peroxodisulfate of formula I. In general, by contacting the dioxin decomposer according to the present invention with the dioxin or the dioxin-containing substance at a temperature of 200 ° C. or higher, dioxins can be decomposed at a high decomposition rate.

The longer the contact time between the dioxin decomposer according to the present invention and the dioxins or dioxin-containing substances, the higher the decomposition rate of dioxins, but the longer the contact time, the higher the cost. In the present invention, the contact time between the dioxin decomposer and the dioxins or the dioxin-containing substance is 3 to 60 minutes, particularly 5 to 3 minutes.
0 minutes is preferred.

The dioxin-decomposing agent according to the present invention can be contacted with dioxins or a dioxin-containing substance in a reducing atmosphere or in the presence of oxygen, that is, in the air or exhaust gas. Can be decomposed efficiently. Therefore, when implementing the method according to the present invention, equipment and work for adjusting the atmosphere are not required.

[0034]

The present invention will be described more specifically with reference to the following examples. The following examples are illustrative of preferred embodiments of the invention and do not limit the invention.

In the following examples, the concentration of dioxins was determined by gas chromatography / mass spectrometry using dioxins (PCDDs, PCDFs Tota).
1).

Example 1 5 g of ammonium salt of peroxodisulfuric acid and fly ash 100
g (dioxins concentration: 950 ng / g), and the mixture was transferred into a 500 mL-capacity square mortar with a lid, then room temperature (20 ° C.), 50 ° C., 100 ° C., 150 ° C., 2 ° C.
Heated at each temperature of 00 ° C. for 30 minutes. Thereafter, the dioxin concentration of the treated product was measured. Table 1 shows the results.

Example 2 5 g of sodium salt of peroxodisulfuric acid and 100 g of fly ash
(Dioxins concentration: 950 ng / g), and the mixture was transferred to a 500-mL square mortar with a lid, and then room temperature (20 ° C), 50 ° C, 100 ° C, 150 ° C, and 2 ° C.
Heated at each temperature of 00 ° C. for 30 minutes. Thereafter, the dioxin concentration of the treated product was measured. Table 1 shows the results.

Comparative Example 5 g of silica particles and 100 g of fly ash were mixed well, and a test was carried out in the same manner as in Example 1. Table 1 shows the concentration of dioxins in the treated product.

[0039]

[Table 1]

From Table 1, it can be seen that, in the comparative example, dioxins increase when the fly ash is heated, and in the temperature range from room temperature to 200 ° C., dioxins are not decomposed but are formed. On the other hand, in the embodiment of the present invention,
It can be seen that dioxins are effectively decomposed at a temperature of 200 ° C. or less.

[0041]

According to the dioxin decomposing agent and the decomposition method of the present invention, dioxins can be decomposed and removed in a short time in a low temperature range where dioxins could not be decomposed in the past. As a result, it is possible to significantly reduce energy costs, improve processing efficiency, and the like, and significantly reduce processing costs. Further, according to the present invention,
Dioxins can be decomposed and removed in the air or exhaust gas without using a reducing atmosphere as a processing atmosphere for dioxins, so that processing equipment is simple and can be easily implemented.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B09C 1/08 C07D 319/24 C07B 35/06 B01D 53/34 134E 61/00 B09B 3/00 304G C07C 23/18 304K C07D 319/24 304L F-term (reference) 2E191 BA12 BA13 BB00 BC01 BD11 4D002 AA21 AC04 BA03 BA12 CA11 DA01 DA07 DA14 GA01 GB03 4D004 AA36 AA37 AA41 AA47 AB06 AB07 CA22 CA34 CA50 CC11 DA03 DA06 4H006 AA02 BAA13 BC BE90 EA13

Claims (5)

[Claims] 1. The following formula I: (Wherein M represents ammonium or metal). A dioxin decomposer comprising a peroxodisulfate represented by the formula: 2. The method of claim 1, wherein the peroxodisulfate of formula I is silica,
The dioxin-decomposing agent according to claim 1, which is supported on a carrier selected from alumina, zeolite, diatomaceous earth, and activated carbon. 3. A method for decomposing dioxins, comprising contacting the dioxin decomposer according to claim 1 with a dioxin or a substance containing dioxins. 4. The method for decomposing dioxins according to claim 3, wherein the agent for decomposing dioxins is brought into contact with dioxins or a substance containing dioxins at a temperature of 300 ° C. or lower. 5. The method for decomposing dioxins according to claim 4, wherein the dioxin decomposer is brought into contact with dioxins or a dioxin-containing substance under pressure.