JP2000288524A - Method for decomposing halogenated organic compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable dioxins in soil to be efficiently decomposed in decomposing a halogenated organic compound by thermally reacting the halogenated organic compound with a polyamine. SOLUTION: In decomposing dioxins contained in the soil of a refuse incineration site or its surroundings, dioxins or halogenated organic compound which is dioxins-containing substance is thermally reacted with a polyamine. A polyamine is a polymer having many nitrogen-containing groups such as amino or imino groups per molecule, and the reaction of the nitrogen groups of the polyamine with a halogen of the halogenated organic compound, such as chlorine of dioxins, causes the decomposition. Polyvinylformamide, polyvinylacetamide or the like which generates a polyamine when decomposed may be used as a polyamine, and so may a copolymer or copolycondensate of a polyamine with another monomer.

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 halogenated organic compounds, and relates to polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) contained in soil (hereinafter referred to as a combination thereof). (Hereinafter referred to as "dioxins").

[0002]

2. Description of the Related Art Incinerators, such as refuse incinerators, emit organic compounds such as phenol, benzene and acetylene, chlorinated aromatic compounds such as chlorophenol and chlorobenzene, and chlorinated alkyl compounds during combustion. Dioxin precursors are generated. When dioxin precursors coexist with fly ash, they become dioxins due to their catalytic action and are present in the fly ash. In addition, the generated dioxins may pollute the garbage incineration plant and the surrounding soil.

[0003] Conventionally, techniques for decomposing dioxins in soil include a method using supercritical water, a method using ozone and ultraviolet rays, a method using heating, a method using maitake, enoki mushroom or wood immortal fungus, and a method using a catalyst. Have been.

The following method has been proposed as a method for decomposing dioxins in fly ash.

The dioxin-containing fly ash is kept at 320 to 400 ° C. for 1 to 2 hours (for example, at 320 ° C. for 2 hours and at 340 ° C. for 1 to 1.5 hours) under a reducing atmosphere such as nitrogen gas (Hagenmeier) Process "ORGAN"
OHALOGEN COMPOUNDS Vo. 27
(1996) "pp. 147-152." The fly ash containing dioxins is heat-treated at 300-500 ° C in the presence of a dioxin production inhibitor such as pyridine (Japanese Patent Application Laid-Open No. 4-241880).

However, all of the above conventional methods for decomposing dioxins in soil have problems in terms of decomposition efficiency, treatment operation, and the like. In particular, the method using ultraviolet light has an effect only on the surface irradiated with ultraviolet light. Therefore, the decomposition rate is poor, and the treatment with a catalyst is difficult. In addition, the heat treatment has a problem of resynthesis and evaporation of dioxins, and decomposition efficiency by fungi is poor.

On the other hand, the above-mentioned method for decomposing dioxins in fly ash has the disadvantage that the processing temperature is relatively 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-mentioned method, it is necessary to perform the treatment in a reducing atmosphere such as nitrogen gas, which increases the labor cost. Moreover, these methods are not suitable for decomposing dioxins in soil.

[0008] On the other hand, the applicant of the present invention has found that dioxins can be decomposed and removed in a short time even in a low temperature range, where it was considered that the dioxins do not decompose in the conventional method, and the dioxins can be carried out in the presence of oxygen. As a possible method of decomposing dioxins, a method of decomposing dioxins by the action of a gaseous or liquid amine compound has been proposed (Japanese Patent Application No. 9-209,197).
-321357. Hereinafter, it is referred to as “first application”. ).

According to the method of the prior application, the chlorine of the dioxins reacts with the amino group (nitrogen atom) in the amine compound, so that the dioxins are usually not decomposed. In the above, the dechlorination reaction of dioxins proceeds rapidly, and it becomes possible to decompose and remove dioxins at low temperature in a short time.

[0010]

However, the above-mentioned prior application method is not suitable for decomposing dioxins in soil for the following reasons.

That is, even when an amine compound is used, the reaction temperature is preferably higher from the viewpoint of the decomposition efficiency of dioxins, and practically it is desirable to carry out the treatment at a temperature of about 250 to 300 ° C. However, at this temperature, the amine compound vaporizes, and all or most of the amine compound is present in gaseous form. However, the gaseous amine compound and dioxins in the soil are sufficiently contacted to achieve high decomposition efficiency. It is difficult to get. It is conceivable to increase the contact efficiency between dioxins in soil and the amine compound by stirring and mixing the gaseous amine compound and the soil, but in this case, a high-pressure airtight container is required, and the processing equipment is complicated and In addition to being expensive, many amine compounds which do not contribute to the reaction are also present, so that the required usage increases. In addition, the soil contains stones, gravel, silt, clay, etc., and may also contain grasses, glass fragments, cans, nails, etc. It is very difficult to do. Also, from an economic perspective,
After the treatment, it is desired to recover and reuse the remaining amine compound. However, the recovery of the gaseous amine compound requires complicated operation and complicated equipment, which is practically difficult.

An object of the present invention is to solve the above-mentioned problems of the prior application, and to provide a method for decomposing a halogenated organic compound which can decompose dioxins in soil efficiently.

[0013]

The method for decomposing a halogenated organic compound according to the present invention is characterized in that the halogenated organic compound is reacted with a polyamine under heating.

The polyamines according to the present invention refer to high molecular compounds having a large number of nitrogen-containing groups such as amino groups and imino groups in one molecule.

In the present invention, the decomposition is carried out by reacting nitrogen-containing groups such as amino group and imino group of these polyamines with halogens of halogenated organic compounds such as chlorine of dioxins.

The polyamines do not vaporize at a reaction temperature effective for decomposing dioxins, but are added to and mixed with a solid (eg, powder), liquid, or solution to be treated, such as soil, and easily. Heat reaction can be performed.

[0017]

Embodiments of the present invention will be described below in detail.

The polyamines used in the present invention are, as described above, high molecular compounds having a large number of nitrogen-containing substituents. In the course of the treatment, those which generate polyamines by heating, in the presence of an acid or alkali, are used. Those that generate polyamines, for example, polyvinyl formamide that decomposes to generate polyamines, polyvinyl acetamide, etc.
Alternatively, a copolymer or co-condensate of the following polyamines with another monomer may be used. Examples of the polyamines usable in the present invention include the following, but are not limited thereto.

Polyamine: poly (meth) allylamine, polyvinylamine, alkylenediamine-alkylene dichloride condensate, alkylenediamine-epichlorohydrin condensate, poly (N-alkylaminoalkyl (meth) acrylate), poly (N-alkylaminoalkyl (meth) acrylamide) , Polyvinylbenzylalkylamine, chitosan, etc. Polyimine: polyalkyleneimine Other cyclic N compounds: polyvinylimidazoline, polyvinylimidazole, polyvinylpyridine Note that polyamines may be those which do not vaporize at the reaction temperature, and the molecular weight is particularly limited. There is no.

The amount of these polyamines to be added is preferably about 0.1 to 10% by weight based on the air-dry weight of the object to be treated such as soil from the viewpoints of the decomposition efficiency of dioxins and the treatment cost.

The higher the reaction temperature, the faster the decomposition rate,
As a result, the decomposition rate also increases, but is generally 200 to 40.
The temperature is preferably set to 0 ° C, particularly 250 to 350 ° C. When the reaction temperature is lower than 200 ° C., the progress of the reaction is slow and the decomposition rate is low. When the reaction temperature exceeds 400 ° C., heat energy increases, processing costs rise, and in addition, problems such as the evaporation of a halogenated organic compound such as dioxins to a gaseous phase occur.

The reaction time varies depending on the reaction temperature, the form of the object to be treated, the concentration of dioxins, and other conditions, but can be appropriately set within a range of 10 to 180 minutes in the usual case.

In order to carry out the present invention, a polyamine is added to an object to be treated containing a halogenated organic compound such as soil containing dioxins and heated to a predetermined temperature for a predetermined time. There is no particular limitation on processing devices such as a mixing device and a heating device. Further, during the heating reaction, it is preferable to perform a little stirring to make the temperature of the treatment system uniform, but this stirring is not always required.

When the polyamines are added to the object to be treated, it is preferable to supply a small amount of water in order to enhance the uniform dispersibility of the polyamines in the object to be treated. It is convenient to add to water and mix uniformly.

The heating can be performed using, for example, a rotary kiln. That is, for example, while introducing the mixture from one end of the rotary kiln and discharging the mixture from the other end, the temperature inside the kiln is gradually increased from one end to the other end, dried in the kiln, and then dried in the kiln. The reaction is carried out while passing through a zone at or above the temperature, and the halogenated organic compound is discharged in a sufficiently decomposed state.

The treated material discharged from the kiln is disposed by landfill or the like. If there is a possibility that volatile matter from the soil or decomposition products of polyamines may be contained in the gas discharged from the kiln, the gas phase may be burned by a heavy oil burner, an electric furnace, or the like, and then discharged.

The method of the present invention can be carried out only by adding and mixing a polyamine in advance to an object to be treated such as soil and heating, and can be easily carried out by an extremely simple apparatus.

In the present invention, as the halogenated organic compound to be decomposed, the aforementioned PCDD or PCD is used.
F and other dioxins and dioxin-containing substances, polychlorinated biphenyls (PCB), pentachlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-
Environmental hormones such as dichlorophenol are exemplified.

The objects to be treated containing these halogenated organic compounds are not limited to soil at all, but include activated carbon, incinerated ash, incinerated fly ash, sediments for lakes and marshes, construction residue, bricks , Concrete, sludge, wood and the like.

[0030]

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

Comparative Example 1 A dioxin-contaminated soil (air-dried, particle size of 2 mm or less) was subjected to a dioxin decomposition test using a sample as a sample. The results of measuring the dioxin concentration of this sample are as shown in Table 1.

This sample was packed in a silica glass column, heated at the temperature shown in Table 1 for 40 minutes while flowing air, and then allowed to cool, and the concentration of dioxins was measured, and the decomposition rate was determined. 1 is shown.

The method for measuring the concentration of dioxins and the method for calculating the toxic equivalent shown in Table 1 are described in "Provisional Manual for Soil Investigations Concerning Dioxins", January 1998 (Soil Pesticide Division, Water Quality Conservation Bureau, Environment Agency, Japan). Depending on the method. The decomposition rate is a percentage of the dioxin concentration or the toxic equivalent with respect to the dioxin concentration or the toxic equivalent of the sample.

Example 1 In Comparative Example 1, an aqueous solution of a polyamine shown in Table 1 was previously added to a sample, and the amount of the polyamine added to the soil was 5.0.
After adding and mixing so as to obtain a concentration of dioxins, the mixture was filled in a quartz glass column in the same manner as in Comparative Example 1, heated at a temperature shown in Table 1 for 40 minutes while flowing air, and then cooled by standing. And the decomposition rate was determined, and the results are shown in Table 1.

From Table 1, it can be seen that the higher the heating temperature, the higher the decomposition efficiency of dioxins, and the addition of polyamines does not cause vaporization of the polyamines.
It is clear that high decomposition efficiency can be achieved even at such a high reaction temperature.

[0036]

[Table 1]

[0037]

As described in detail above, according to the method for decomposing a halogenated organic compound of the present invention, a halogenated organic compound such as dioxins contained in soil or the like can be removed without complicated operation or complicated equipment. Easy and efficient disassembly,
The content concentration can be reduced to an extremely low concentration.

Claims (2)

[Claims] 1. A method for decomposing a halogenated organic compound, comprising reacting a halogenated organic compound with a polyamine under heating. 2. The method for decomposing a halogenated organic compound according to claim 1, wherein the halogenated organic compound is a dioxin or a dioxin-containing substance.