JP3287301B2 - Decomposition method of dioxins - 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 decomposing dioxins, and more particularly to fly ash and incinerated ash discharged from various incinerators such as refuse incinerators (hereinafter, these are collectively referred to as "incinerated ash"). ) Efficiently decomposes organic chlorine compounds such as polychlorinated-p-dibenzodioxins (PCDD) and polychlorinated dibenzofurans (PCDF) (hereinafter, these are collectively referred to as "dioxins"). On how to do it.

[0002]

BACKGROUND OF THE INVENTION In incinerators such as refuse incinerators, during combustion, organic compounds such as phenol, benzene, and acetylene; chlorinated aromatic compounds such as chlorophenol and chlorobenzene; and dioxin precursors such as chlorinated alkyl compounds. The body develops. When dioxin precursors coexist with fly ash, they become dioxins by catalytic action and are present in incinerated ash.

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

The dioxin-containing fly ash is kept at 320 to 400 ° C. for 1 to 2 hours (for example, 2 hours at 320 ° C. and 1 to 1.5 hours at 340 ° C.) under a reducing atmosphere such as nitrogen gas (Hagen) Meyer process "ORGAN"
OHALOGEN COMPOUNDS Vo. 27
(1996) "pp. 147-152).

A fly ash containing dioxins is heat-treated at 300 to 500 ° C. in the presence of a dioxin production inhibitor (JP-A-4-241880). It is said that dioxin does not thermally decompose below 300 ° C,
This method basically decomposes dioxin by heating at 300 ° C. or higher as described above, and in order to suppress the generation of dioxin from the dioxin precursor during the heat treatment, a dioxin production inhibitor is used in the dioxin decomposition temperature band. Is added to fly ash. Specifically, fly ash is heated at 400 ° C. for 2 hours in the presence of pyridine vapor as a production inhibitor.
Heating for hours.

[0006] The above-mentioned conventional methods have the disadvantage that the processing temperature is high and the processing time is long, so that the required heating energy is large and the processing cost is high. In particular, in the above-described method, it is necessary to perform the treatment in a reducing atmosphere such as nitrogen gas, which increases labor and cost.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems, and is capable of decomposing and removing dioxins in a short time even in a low-temperature region where it has been considered that dioxins do not decompose in the conventional method. Another object of the present invention is to provide a method for decomposing dioxins which can be performed even in the presence of oxygen.

[0008]

The dioxins are decomposed by bringing a dioxin or a dioxin-containing substance into contact with an amine compound or an ammonium compound at a temperature lower than 300 ° C.

According to the present invention, the reaction of chlorine in a dioxin with an amine compound or an ammonium compound causes the removal of the dioxin at a temperature lower than 300 ° C., at which dioxins are not normally decomposed. The chlorine reaction proceeds rapidly, and dioxins are decomposed.

The effect of an amine compound or ammonium compound decomposing dioxins at a temperature lower than 300 ° C. has not been known.

Examples of the amine compound include alkanolamines such as monoethanolamine, diethanolamine, triethanolamine and methanolamine, alkylalkanolamines such as aminomethylpropanol, alkylamines such as diethylamine, propylamine and ethylenediamine, and rings such as aniline. Formula amines and the like are included.

Examples of the ammonium compound include ammonia, urea, and ammonium salts (eg, ammonium bicarbonate, ammonium carbonate, ammonium hydroxide, ammonium acetate, ammonium sulfate, ammonium phosphate, ammonium hydrogen phosphate, etc.).

The applicant of the present invention has disclosed a Japanese Patent Application No. 10-29789.
No. has been filed. The same reference is directed to a method for decomposing dioxins using an amine compound. Claim 1 of the present invention relates to a method for decomposing dioxins or a substance containing dioxins,
A method for decomposing dioxins, comprising bringing a gaseous amine compound into contact with a gas at a temperature of 100 ° C. or more and less than 300 ° C. Claim 2 is that after adding a liquid or gaseous amine compound to dioxins or a dioxin-containing substance, the amine compound is brought into gaseous contact under a condition of 100 ° C or more and less than 300 ° C. And a method for decomposing dioxins. "

In the same publication, monoamineamine, triethanolamine and methanolamine are exemplified as amine compounds.

In the present application, in order to avoid duplication with Japanese Patent Application No. 10-29789, amine compounds are classified and claimed according to contact temperatures as follows.

I When the temperature is lower than 100 ° C. All the above-mentioned amine compounds II When the temperature is higher than 100 ° C. and lower than 300 ° C. Alkanolamine (however, excluding monoethanolamine, triethanolamine and methanolamine) aminomethylpropanol Alkylamines such as alkylamines (eg, diethylamine and propylamine) and alkylamines such as alkyldiamines (eg, ethylenediamine) cyclic amines such as aniline Ammonium compounds are disclosed in Japanese Patent Application No. 10-29.
No. 789 has no disclosure. Therefore, in the present application, 300
Claims that ammonium compounds decompose dioxins in a temperature range lower than ° C.

In the present invention, various amine compounds and ammonium compounds may be used alone or in combination of two or more. An amine compound and an ammonium compound may be used in combination.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, examples of dioxins include dioxins contained in exhaust gas discharged from various incinerators such as garbage incinerators and factory incinerators. Examples of the dioxin-containing substance include incinerated ash that has adsorbed dioxins, powdered activated carbon added for adsorbing dioxins, soil contaminated with dioxins, and the like.

Examples of the amine compound include alkanolamines such as monoethanolamine, diethanolamine, triethanolamine and methanolamine, alkylalkanolamines such as aminomethylpropanol, alkylamines such as diethylamine, propylamine and ethylenediamine, and rings such as aniline. Examples thereof include formula amines. Of these, triethanolamine, diethanolamine, monoethanolamine, aniline, propylamine, ethylenediamine, and aminomethylpropanol are preferred.

Examples of the ammonium compound include ammonia, urea, and ammonium salts (eg, ammonium bicarbonate, ammonium carbonate, ammonium hydroxide, ammonium acetate, ammonium sulfate, ammonium phosphate, ammonium hydrogen phosphate, etc.).
Urea, ammonium bicarbonate, ammonium sulfate and ammonium hydrogen phosphate are preferred, with ammonia being most preferred.

Hereinafter, the form of contact between the amine compound and / or ammonium compound and the dioxin and the temperature at that time will be described. As described in the section of the means for solving the above-mentioned problems, the present invention employs 100 ° C. More than 30
Under a temperature condition of less than 0 ° C., the amine compounds described above are used.

When the dioxins are decomposed by contacting the amine compound or the ammonium compound with the incinerated ash or the collected fly ash, the amine compound or the ammonium compound is added to the incinerated ash or the collected fly ash in an amount of 0.1 to 0.1%. The contact is preferably carried out at a ratio of 10 to 10% by weight, particularly 1 to 5% by weight. It is preferable to increase the amount of the amine compound or the ammonium compound as the temperature at the time of contact decreases.

The addition form of the amine compound or ammonium compound may be any of gaseous, liquid and aqueous solutions. Since dioxins or dioxin-containing substances are efficiently decomposed by contact with a gaseous amine compound or ammonium compound, the amine compound or ammonium compound may have a sufficiently high vapor pressure at a temperature lower than 300 ° C. preferable.

When a liquid or aqueous solution of an amine compound or an ammonium compound is sprayed onto exhaust gas or kneaded with incineration ash or the like in advance, the amine compound or the ammonium compound is sufficiently gasified at a temperature lower than 300 ° C. It is preferable to select an amine compound or an ammonium compound having a high vapor pressure.

As a method for bringing the amine compound or the ammonium compound into contact with the object to be treated, when the dioxin-containing substance is soil, incinerated ash, collected fly ash, etc., for example, the following A, B, Method C can be adopted.

A: A dioxin-containing substance and an amine compound or an ammonium compound are mixed and brought into contact at room temperature. Alternatively, the mixture is heated to a temperature lower than 300 ° C. to gasify the amine compound or the ammonium compound, and contact the amine compound or the ammonium compound with dioxins. In these cases, the amine compound or ammonium compound is preferably dissolved in water or another solvent.

B: The amine compound or the ammonium compound is heated to a temperature lower than 300 ° C. to gasify, and an air stream containing this gas is brought into contact with a dioxin-containing substance.

C: An amine compound or an ammonium compound is attached to a solid substance, and the solid substance is mixed with the dioxin-containing substance or placed on the dioxin-containing substance and heated to a temperature lower than 300 ° C. Preferably, gas is flowed at this time.

When dioxins or dioxin-containing substances are present in gaseous form or in the form of particles and suspended in an air stream such as combustion exhaust gas, for example, the following D, E,
The method of F can be adopted.

D: A vapor of an amine compound or an ammonium compound or a gas containing the vapor is supplied into the gas stream.

E: A liquid amine compound or ammonium compound is supplied into the gas stream in the form of a mist or droplets.

F: A liquid in which an amine compound or an ammonium compound is dissolved in this gas stream is supplied in the form of a mist or droplets.

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 solution is stored in the exhaust gas flue or dust collector in front of the dust collector. It is preferable to supply the amine compound or the ammonium compound which is being used. In a normal case, the dust collector inlet gas temperature of the electric dust collector is 200 to 230 ° C., and the dust collector inlet gas temperature of the filtration type dust collector is about 140 to 200 ° C. It is desirable that the amine compound or ammonium compound supplied to the upstream side has a sufficiently high vapor pressure at 140 to 230 ° C.

In general, dioxins do not decompose at a temperature lower than 300 ° C. In the present invention, the temperature at which the dioxins or the dioxin-containing substance is brought into contact with the amine compound or the ammonium compound is lower than 300 ° C., but the chlorine in the dioxins reacts with the amine compound or the ammonium compound. Then, the dechlorination reaction of the dioxins proceeds, and the dioxins are decomposed. The minimum temperature at the time of this contact is determined by the vapor pressure or the ease of vaporization of the amine compound or ammonium compound. That is, monoethanolamine is at room temperature or higher (but lower than 100 ° C in the present application as described above), diethanolamine is at 150 ° C or higher, and aniline, n-propylamine, ethylenediamine, and aminomethylpropanol are at 150 ° C or higher. It is preferable to contact with a dioxin-containing substance. If the amine compound or the ammonium compound and the dioxin or the dioxin-containing substance come into contact at a temperature of 200 ° C. or higher, the dioxin is generally decomposed at a sufficiently high decomposition rate. Ammonia has a practically sufficiently high decomposition efficiency at room temperature or higher. Decomposition rate hardly improves even if both contact at 300 ° C. or higher.

The longer the contact time between the amine compound or ammonium compound and the object to be treated, the higher the decomposition rate of dioxins, but an excessively long contact time increases the treatment cost. In the method of the present invention, a sufficiently high decomposition rate can be obtained usually in a contact time of 3 to 60 minutes, particularly 4 to 40 minutes, especially about 5 to 30 minutes. It is preferable that the lower the temperature at the time of contact, the longer the contact time. For example, when the temperature at the time of contact is room temperature, the contact time is preferably about 20 to 40 minutes.

The amine compound or ammonium compound and the dioxin or the dioxin-containing substance can be sufficiently dioxin-contacted in a reducing atmosphere or in the presence of oxygen, that is, in the air or exhaust gas. Decompose. Therefore, when implementing the method of the present invention, equipment and work for adjusting the atmosphere are usually unnecessary.

However, when contacting a dioxin or a dioxin-containing substance with an amine compound or an ammonium compound, care should be taken to avoid explosion if this compound has a flash point lower than the temperature at the time of this contact. If the concentration of the compound in the atmosphere at the time of this contact is lower than the explosive limit concentration, explosion is avoided. If the oxygen concentration in this atmosphere is lower than the explosive limit oxygen concentration, the explosion is also effectively avoided. Therefore, measures to reduce the oxygen concentration in the atmosphere are effective in preventing explosion. Such measures include oxygen-free or low-oxygen gas such as nitrogen gas, carbon dioxide gas, water vapor, and combustion exhaust gas. Is provided.

Attention should be paid to explosions when carrying out decomposition reactions in a normal air atmosphere. Supplying a part of the combustion exhaust gas discharged from the dust collector by using a blower or the like and replacing it with air is a preferable low-cost method for lowering the oxygen concentration in the reaction atmosphere.

When treating incinerated ash or collected fly ash according to the method of the present invention, a chelating agent or a heavy metal fixing agent such as phosphoric acid is used in combination with decomposition of dioxins,
The heavy metal in the ash may be immobilized simultaneously.

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

Ash and soil treated by the method of the present invention are:
As it is or after further performing the above-described heavy metal fixing treatment, for example, solidification treatment, treatment of packing in a drum can, or landfilling.

[0042]

The present invention will be described more specifically with reference to the following examples and comparative examples.

Example 1 and Reference Example A glass column of 20 mmφ × 250 mm was filled with 3 g of fly ash (dioxin concentration: 1335 ng / g) collected from a municipal solid waste incinerator, and liquid monoethanolamine was placed thereon. Is placed on the glass beads, and room temperature (20 ° C.), 50 ° C., 100 ° C., 150 ° C.
It heated for 20 minutes at each temperature of 180 degreeC, 200 degreeC, 220 degreeC, 250 degreeC, and 290 degreeC.

Thereafter, the concentration of dioxins in the treated product was measured, and the results are shown in Table 1.

Example 2 Diethanolamine was used in place of monoethanolamine. Otherwise, the experiment was performed in the same manner as in Example 1.
Table 1 shows the measured values of the dioxin concentrations of the treated products.

Comparative Example 1 An experiment was performed in the same manner as in Example 1 except that nothing was attached to the glass beads. Table 1 shows the measured values of the dioxin concentrations of the treated products.

From the results of Examples 1 and 2 and the result of Comparative Example 1, the residual ratio of dioxins was calculated by the following equation, and the results are shown in Table 1.

[0048]

(Equation 1)

[0049]

[Table 1]

As is evident from Table 1, in Comparative Example 1 in which no amine compound was used, the residual ratio of dioxins increased when the fly ash was heated. In this temperature range, only the dioxins were formed, and no decomposition occurred. You can see that. On the other hand, in Examples 1 and 2 in which the fly ash was brought into contact with the amine compound, dioxin was effectively decomposed, and it can be seen that the lower limit of the decomposition temperature differs depending on the type of the amine compound. That is, monoethanolamine exhibits a decomposition rate of 85% or more at 50 ° C. and about 40% at room temperature. With diethanolamine, when the temperature exceeds 150 ° C., dioxins are decomposed at a high decomposition rate.

Examples 3 to 6 In Example 2, aniline was used in Example 3, instead of diethanolamine, n-propylamine was used in Example 4, ethylenediamine was used in Example 5, and aminomethyl was used in Example 6. The experiment was conducted in the same manner except that propanol was used and the heating temperature was 250 ° C. Table 2 shows the residual concentrations and decomposition rates of dioxins.

Example 7 An experiment was conducted in the same manner as in Example 1 except that an aqueous ammonia solution was used in place of monoethanolamine, and the heating temperature was changed to 250 ° C. Table 3 shows the residual concentrations and decomposition rates of dioxins. The amount of ammonia (NH ₃ ) attached to the glass beads was 150 mg.

[0053]

[Table 2]

Example 8 A small amount of glass wool was packed in a glass tube having a diameter of 20 mm, the glass tube was made vertical, and 3 g of the same municipal garbage incineration fly ash was inserted into the glass wool. 0.7g of ammonium bicarbonate powder on fly ash
(150 mg as ammonia).

The glass tube was inserted vertically into a tube furnace while being kept vertical, and the ash was heated to a temperature of 50 ° C., 100 ° C. or 250 ° C., and 15 mL of room temperature (20 ° C.) air was supplied from above.
Per minute for 20 minutes. Thereafter, the concentration of dioxins in the treated product was measured, and the results are shown in Table 3.

[0056]

[Table 3]

Examples 9 to 12 In Example 1, various amine compounds and ammonia shown in Table 4 were used in place of monoethanol, the reaction temperature was adjusted to room temperature (20 ° C.), 50 ° C. and 100 ° C., and dioxin was added. The same experiment was performed except that fly ash having a concentration of 310 ng / g was used. Table 4 shows the results.

Example 13 The same procedure as in Example 9 was carried out except that ammonia gas was used at room temperature (20%).
C)). Table 4 shows the results.

[0059]

[Table 4]

From Tables 2, 3 and 4, it is clear that dioxins can be decomposed at a high decomposition rate even in Examples 3 to 13.

[0061]

As described in detail above, according to the method for decomposing dioxins of the present invention, dioxins can be decomposed and removed in a short time in a low temperature range where decomposition normally does not occur. Reduction of necessary energy costs,
Processing efficiency can be improved, and processing costs can be significantly reduced. In addition, the method of the present invention can be carried out in the atmosphere or in exhaust gas without setting the treatment atmosphere to a reducing atmosphere, so that the treatment equipment is simple and easy to carry out.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI B09B 3/00 304Z (72) Inventor Mitsuhiro Mashiko 3-4-7 Nishi-Shinjuku, Shinjuku-ku, Tokyo Inside Kurita Water Industries Ltd. (72 ) Inventor Noboru Fujiwara Kurita Kogyo Co., Ltd., 3-4-7 Nishi Shinjuku, Shinjuku-ku, Tokyo (56) References JP-A-4-241880 (JP, A) JP-A-4-257609 (JP, A) JP-A-4-250817 (JP, A) JP-A-6-285453 (JP, A) JP-A-7-155723 (JP, A) JP-A-11-104453 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B09B 3/00 A62D 3/00 ZAB JICST file (JOIS) WPI (DIALOG)

Claims (5)

(57) [Claims] 1. A method for decomposing dioxins, comprising the step of bringing dioxins or a dioxin-containing substance into contact with an amine compound at a temperature lower than 100 ° C. to decompose dioxins. 2. The method according to claim 1, wherein the amine compound is 10
A method for decomposing dioxins, which is one or more of alkanolamines, alkylalkanolamines, alkylamines and cyclic amines having a vapor pressure at 0 ° C. or lower. 3. A dioxin or a dioxin-containing substance and one or two of an alkanolamine (excluding monoethanolamine, triethanolamine and methanolamine), an alkylalkanolamine, an alkylamine and a cyclic amine. A method for decomposing dioxins, comprising the step of contacting the above with a temperature of 100 ° C. or higher and lower than 300 ° C. to decompose dioxins. 4. A method for decomposing dioxins, comprising the step of bringing dioxins or a substance containing dioxins into contact with an ammonium compound at a temperature lower than 300 ° C. to decompose dioxins. 5. The method for decomposing dioxins according to claim 4, wherein the ammonium compound is at least one of ammonia, urea and ammonium salts.