JP2001247840A - Agent and method for decomposing dioxins - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an agent and to provide a method both for decomposing dioxins whereby the decomposition of dioxins at low temperatures formerly regarded as impossible is made possible. SOLUTION: The agent contains an alkali salt, an alkaline earth metal salt, an ammonium salt, an amine salt, a zincate, or a nickel salt of a compound represented by formula I (wherein R1 and R2 are each an alkyl, a cycloalkyl or an arylalkyl group provided they may combine with each other to form a ring). The method comprises contacting the agent with dioxins or a dioxins- containing substance.

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]

Embedded image

(Wherein R ₁ and R ₂ may be the same or different and each represents an alkyl group, a cycloalkyl group or an arylalkyl group, or R ₁ and R ₂ may form a ring together with R ₁ and R ₂₎ The present invention relates to a dioxin decomposer comprising an alkali metal salt, an alkaline earth metal salt, an ammonium salt, an amine salt, a zincate or a nickel salt of the compound represented by the formula: 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.

In the above formula I, "alkyl" is preferably C ₁ -C ₈ alkyl, especially C ₁ -C ₄ alkyl, and specific examples include methyl, ethyl, propyl, i-propyl, butyl, i -Butyl, sec-butyl, 2-ethylhexyl and the like. Further, specific examples of the cycloalkyl group include cyclopentyl and cyclohexyl, and specific examples of the arylalkyl group include benzyl and phenethyl. Specific examples of the case where R ₁ and R ₂ form a ring include tetramethylene, pentamethylene, oxydiethylene, and the like.

[0017]

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 salt of a compound of the formula I to thereby allow a chlorine atom in the dioxin to be converted to a compound of the formula I. The reaction with the salt of the compound causes the dechlorination reaction of the dioxins or the cleavage reaction of the six-membered ring (benzene ring) to proceed rapidly, whereby the dioxins are decomposed.

The dioxin-decomposing agent according to the present invention may be used alone or in combination of two or more salts of the compound of the formula I. In the dioxin decomposing agent according to the present invention, a salt of the compound of the formula I may be supported on a carrier. Examples of the carrier that can be used include silica, alumina, zeolite, diatomaceous earth, activated carbon, and the like. By supporting a salt of the compound of the formula I on such a carrier, a catalytic effect of dioxin decomposition by such a carrier is expected,
Dioxins can be decomposed more efficiently.

The compound which is a main component of the dioxin decomposer according to the present invention is an alkali metal salt of the compound of the above formula I,
Alkaline earth metal salts, ammonium salts, amine salts, zincates or nickel salts. Here, the “alkali metal salt” includes, for example, lithium salt, potassium salt, sodium salt and the like, and the “alkaline earth metal salt” includes, for example, magnesium salt, calcium salt and the like, amine salt As, methylamine, ethylamine, propylamine, amylamine, hexylamine,
Monoalkylamine salts such as octylamine; dialkylamine salts such as dimethylamine, diethylamine, dipropylamine, dibutylamine, diamylamine, dihexylamine and dioctylamine; trimethylamine, triethylamine, tripropylamine, tributylamine, triamylamine, trialkylamine Trialkylamine salts such as hexylamine and trioctylamine; monocycloalkylamine salts such as cyclopentylamine and cyclohexylamine; dicycloalkylamine salts such as dicyclopentylamine and dicyclohexylamine; monoaralkylamine salts such as benzylamine and phenethylamine Diaralkylamine salts such as dibenzylamine and diphenethylamine; adialkylamine salts such as ethanolamine and propanolamine. Kanoruamin salts; diethanolamine, di alkanolamine salts, such as di-propanolamine; triethanolamine, trialkanolamine salts such as tripropanolamine; pyrrolidine, piperidine, pipecoline, cyclic amine salts such as a morpholine;
And aromatic amine salts such as aniline, triidine, and xylidine.

According to the present invention, the reaction of the chlorine in the dioxins with the salt of the compound of the formula I allows the dioxins to be reacted at a temperature lower than 300.degree. Dechlorination reaction or cleavage reaction of the six-membered ring (benzene ring) proceeds rapidly, and dioxins are decomposed.

Further, by contacting the dioxin decomposing agent according to the present invention with the dioxin or the dioxin-containing substance under a pressurized condition, the dioxin 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 refuse incinerator or a factory incinerator, an incineration ash adsorbing 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 salt of the compound of the formula I is converted into incinerated ash or collected fly ash. 0.1 to 10% by weight, especially 1 to 10% by weight
It is preferable to make contact at a ratio of 5% by weight.

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

When the dioxin decomposing agent according to the present invention is brought into contact with dioxins or a dioxin-containing substance, the form 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 lower temperatures 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 salts of the compound of the formula I include sodium salt of dimethyldithiocarbamic acid, calcium salt of dimethyldithiocarbamic acid, and methylamine salt of dimethyldithiocarbamic acid.

When the dioxin-containing substance is soil, incineration ash, collected fly ash, or the like, the method of 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 of heating under a pressurized condition, the above temperature may be lower.

When the dioxins and the dioxin-containing substances are present in gaseous form or in the form of particles 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 of a salt of the compound of the formula I or a gas containing the vapor is supplied to an air stream containing dioxins or a substance containing dioxins. E. FIG. The salt of the compound of formula I is supplied in the form of a mist or droplets in an air stream containing dioxins or a substance containing dioxins. F. A liquid in which a salt of the compound of the formula I is dissolved is supplied in the form of a mist or droplets into an air stream containing dioxins or a substance containing dioxins.

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.
° C, the dioxin-decomposing agent according to the present invention, in particular, the dioxin according to the present invention in which the salt of the compound of formula I is a sodium salt of dimethyldithiocarbamic acid, It is preferable to supply an analogous decomposer.

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 a salt of the compound of the formula I, and a dechlorination reaction of the dioxins or hexachloride. The cleavage reaction of the member ring (benzene ring) 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 salt of the compound 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 the dioxin-containing substance, the higher the decomposition rate of the 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 a dioxin 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.

[0036]

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 sodium salt of dimethyldithiocarbamic acid and 100 g of fly ash (dioxins concentration: 950 ng / g) were mixed well, transferred to a 500 mL-capacity square mortar with a lid, and then cooled to room temperature (20%). ℃), 50 ℃, 100 ℃, 150
It heated for 30 minutes at each temperature of 200 degreeC and 200 degreeC. Thereafter, the dioxin concentration of the treated product was measured. Table 1 shows the results.

Example 2 5 g of sodium salt of dioctyldithiocarbamic acid,
100 g of fly ash (dioxin concentration: 950 ng / g) was mixed well and transferred to a 500 mL-capacity square mortar with lid, then room temperature (20 ° C.), 50 ° C., 100 ° C., 15 ° C.
It heated at each temperature of 0 degreeC and 200 degreeC for 30 minutes. afterwards,
The dioxin concentration of the processed product was measured. Table 1 shows the results.

Example 3 5 g of sodium salt of dibenzyldithiocarbamic acid,
100 g of fly ash (dioxin concentration: 950 ng / g) was mixed well and transferred to a 500 mL-capacity square mortar with lid, then room temperature (20 ° C.), 50 ° C., 100 ° C., 15 ° C.
It heated at each temperature of 0 degreeC and 200 degreeC for 30 minutes. afterwards,
The dioxin concentration of the processed product was measured. Table 1 shows the results.

Example 4 Sodium salt of dicyclohexyldithiocarbamic acid 5
g and fly ash 100 g (dioxin concentration 950 ng /
g), and transferred into a 500 mL-capacity square mortar with a lid.
It heated at each temperature of 150 degreeC, 200 degreeC for 30 minutes.
Thereafter, the dioxin concentration of the treated product was measured. Table 1 shows the results.

Example 5 5 g of calcium salt of dimethyldithiocarbamic acid and 100 g of fly ash (concentration of dioxins: 950 ng / g) were mixed well, and transferred to a 500 mL-capacity square mortar with a lid. ℃), 50 ℃, 100 ℃, 150
It heated for 30 minutes at each temperature of 200 degreeC and 200 degreeC. Thereafter, the dioxin concentration of the treated product was measured. Table 1 shows the results.

Example 6 5 g of methylamine salt of dimethyldithiocarbamic acid,
100 g of fly ash (dioxin concentration: 950 ng / g) was mixed well and transferred to a 500 mL-capacity square mortar with lid, then room temperature (20 ° C.), 50 ° C., 100 ° C., 15 ° C.
It heated at each temperature of 0 degreeC and 200 degreeC for 30 minutes. afterwards,
The dioxin concentration of the processed product was measured. Table 1 shows the results.

Example 7 5 g of octylamine salt of dimethyldithiocarbamic acid
And fly ash 100g (dioxin concentration 950ng /
g), and transferred into a 500 mL-capacity square mortar with a lid.
It heated at each temperature of 150 degreeC, 200 degreeC for 30 minutes.
Thereafter, the dioxin concentration of the treated product was measured. Table 1 shows the results.

Example 8 5 g of dimethylamine salt of dimethyldithiocarbamic acid
And fly ash 100g (dioxin concentration 950ng /
g), and transferred into a 500 mL-capacity square mortar with a lid.
It heated at each temperature of 150 degreeC, 200 degreeC for 30 minutes.
Thereafter, the dioxin concentration of the treated product was measured. Table 1 shows the results.

Example 9 5 g of trimethylamine salt of dimethyldithiocarbamic acid
And fly ash 100g (dioxin concentration 950ng /
g), and transferred into a 500 mL-capacity square mortar with a lid.
It heated at each temperature of 150 degreeC, 200 degreeC for 30 minutes.
Thereafter, the dioxin concentration of the treated product was measured. Table 1 shows the results.

Example 10 5 g of cyclohexylamine salt of dimethyldithiocarbamic acid and 100 g of fly ash (dioxins concentration: 950 ng
/ G) and well-transferred into a 500 mL-capacity square mortar with a lid.
It heated at each temperature of 150 degreeC, 200 degreeC for 30 minutes.
Thereafter, the dioxin concentration of the treated product was measured. Table 1 shows the results.

Example 11 5 g of benzylamine salt of dimethyldithiocarbamic acid
And fly ash 100g (dioxin concentration 950ng /
g), and transferred into a 500 mL-capacity square mortar with a lid.
It heated at each temperature of 150 degreeC, 200 degreeC for 30 minutes.
Thereafter, the dioxin concentration of the treated product was measured. Table 1 shows the results.

Example 12 5 g of dibenzylamine salt of dimethyldithiocarbamic acid
And fly ash 100g (dioxin concentration 950ng /
g), and transferred into a 500 mL-capacity square mortar with a lid.
It heated at each temperature of 150 degreeC, 200 degreeC for 30 minutes.
Thereafter, the dioxin concentration of the treated product was measured. Table 1 shows the results.

Example 13 5 g of ethanolamine salt of dimethyldithiocarbamic acid
And fly ash 100g (dioxin concentration 950ng /
g), and transferred into a 500 mL-capacity square mortar with a lid.
It heated at each temperature of 150 degreeC, 200 degreeC for 30 minutes.
Thereafter, the dioxin concentration of the treated product was measured. Table 1 shows the results.

Example 14 A mixture of 5 g of dimethylamine salt of dimethyldithiocarbamic acid and 5 g of silica was mixed well with 100 g of fly ash (dioxins concentration: 950 ng / g) to give a capacity of 50 g.
After transfer to a 0 mL square mortar with lid, room temperature (20
° C), 50 ° C, 100 ° C, 150 ° C, and 200 ° C for 30 minutes. Thereafter, the dioxin concentration of the treated product was measured. Table 1 shows the results.

Example 15 5 g of piperidine salt of pentamethylenedithiocarbamic acid
And fly ash 100g (dioxin concentration 950ng /
g), and transferred into a 500 mL-capacity square mortar with a lid.
It heated at each temperature of 150 degreeC, 200 degreeC 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 heat-treated in the same manner as in Examples 1 to 14. Table 1 shows the concentration of dioxins in the treated product.

[0054]

[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 of room temperature to 200 ° C., the dioxins are not decomposed but are formed instead. 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.

[0056]

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.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yukio Tsurugimo 11-1 Haneda Asahimachi, Ota-ku, Tokyo Ebara Corporation (72) Inventor Hiroshi Shibuya 1-16-28-520F Fujimi, Tsurugashima-shi, Saitama Term (reference) 2E191 BA12 BB00 BC05 BD11 4D004 AA36 AA37 AA41 AA47 AB07 CA22 CC15 DA02 DA03 DA06 DA07

Claims (5)

[Claims] 1. The following formula I: (Wherein R ₁ and R ₂ may be the same or different,
An alkyl group, a cycloalkyl group or an arylalkyl group, or a ring formed by R ₁ and R ₂ ), an alkali metal salt, an alkaline earth metal salt, an ammonium salt, an amine salt A dioxin decomposer, comprising a zinc salt or a nickel salt. 2. The decomposition agent for dioxins according to claim 1, wherein the salt of the compound of the formula I is supported on a carrier selected from silica, alumina, zeolite, diatomaceous earth or 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.