JP2003181437A - Method for thermally decontaminating soil polluted with dioxins - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for decontaminating soil polluted with dioxins by which fear of secondary pollution such as dispersion associated with storage of the polluted soil and polluted waste does not occur. <P>SOLUTION: In the method for decontaminating the soil polluted with DXN, a material polluted with dioxins is heated at 250 to 700°C. The material polluted with dioxins to which this method is applied is, for example, incinerator disassembling waste or polluted soil containing it. Heating temperature is preferably 400 to 550°C and heating atmosphere is preferably air atmosphere. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying incinerator demolition waste and dioxin-contaminated soil containing it.

[0002]

2. Description of the Related Art Recently, soil pollution due to poorly water-soluble organic chlorine compounds such as dioxins (hereinafter abbreviated as DXN) has become a social problem in the vicinity of a refuse incinerator, and DXN contamination in the soil around the incinerator is some. Found. In addition, with the spread of waste incineration business, the dismantling of aging incinerators is in progress, but when the incinerator is dismantled, DXN-contaminated waste is generated. These wastes or contaminated soil containing them are often stored after excavation, but secondary contamination such as scattering of contaminated soil may occur during storage.

[0003]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to provide a method for purifying DXN-contaminated soil which is free from the risk of secondary pollution such as scattering due to storage of contaminated soil or waste. To do.

[0004]

A method for cleaning DXN-contaminated soil according to the present invention is a method for treating DXN-contaminated soil at a temperature of 250 to 70.
The method is characterized by heating at 0 ° C.

DXN pollutants applied to this method are, for example, incinerator demolition waste or contaminated soil containing it.

The heating temperature is preferably 400 to 550 ° C.

The heating atmosphere is preferably an air atmosphere.

Conventionally, the decomposition of DXN has required a high temperature of 800 ° C. or higher. Further, maintaining the oxygen deficient state is required for decomposition at low temperature for the stability of the reaction. The cause of these is that several% of heavy metals are mixed in the fly ash of the incinerator, and DXN is resynthesized by the catalytic action of these heavy metals. But,
The amount of heavy metals present in soil is small compared to the amount of fly ash,
Since the degree of DXN resynthesis may be low,
Low temperature heat treatment in air atmosphere was adopted. DXN with a low degree of chlorination is mostly volatilized at 300 to 400 ° C, so DXN decomposition by secondary combustion or the like may be performed, and DXN with a high degree of chlorination is decomposed by a dechlorination reaction or an oxidation reaction. It Therefore, the decomposition in the low temperature range has advantages that the equipment material is not required to be sophisticated, and the air atmosphere does not require auxiliary equipment such as a nitrogen gas generator.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be specifically described with reference to Examples.

Example 1 A 40 mm diameter SUS tube containing 20 g of DXN-contaminated soil was heat-treated in a horizontal tubular furnace for 1 hour. S during processing
Rotate the US tube at 1.7 rpm and add 0.5N nitrogen gas.
Aerated with m ³ / h. The heat treatment temperature is 250, 400,
550 and 700 ° C. After a predetermined time, the treated soil was rapidly cooled and the DXN content was measured. The treatment at a temperature of 250 ° C. was able to remove 15% of DXN contained in the soil before the treatment. Temperatures 400, 550 and 70
At 0 ° C, 99% or more of DXN could be removed.
These results are summarized in Table 1.

[0011]

[Table 1]

2) The same operation as in Example 1 was performed except that the nitrogen gas was replaced with air supplied at the same flow rate.

As a result, 20% of DXN contained in the soil before the treatment could be removed by the treatment at the temperature of 250 ° C. The treatment at a temperature of 400 ° C. was able to remove 90% of DXN. At the temperatures of 550 and 700 ° C., 99.9% or more of DXN could be removed. The results are summarized in Table 2.

[0014]

[Table 2]

Example 3 FIG. 1 shows an example of a method for cleaning dioxins-contaminated soil by the low temperature heating method according to the present invention.

After the DXN-contaminated soil is treated with the screen (1), it is thrown into the indirect heating kiln (2) to obtain 250-70.
It is heat-treated under rotation at a temperature of 0 ° C., preferably 400 to 550 ° C. The heat source of the indirect heating kiln (2) is electricity, steam, fossil fuel, heat medium, etc. The generated exhaust gas is then sent to the secondary combustion furnace (3), where it is 800-1000 ℃.
The gas is heated by, and the organic components, DXN, etc. in the gas are completely burned. Then, the treated gas is cooled by injecting air or water and then sent to the high temperature dust collector (4). Slaked lime is put in here, and dust and harmful substances in the exhaust gas are removed at 300 to 500 ° C. Next, the same gas is passed through a denitration catalyst device (8) and subjected to denitration treatment, after which heat is recovered in the heat exchanger (5) and water in the exhaust gas is condensed. The treated gas is discharged to the outside of the system from the chimney (7) through the induced draft fan (6). Dust transfer device (10) for ash, dust, etc. from the high temperature dust collector (4)
Will be sent in place. The purified soil discharged from the indirect heating kiln (2) is sent to the designated storage site by the cooling feeder (9).

[0017]

INDUSTRIAL APPLICABILITY DXN can be removed from DXN contaminants by heat-treating the DXN contaminants in a nitrogen atmosphere or preferably an air atmosphere. At this time, the higher the processing temperature, the more preferable, but in the case of an air atmosphere, DXN (T
If the removal rate of EQ) is 90% or more, the treatment is 400 ° C or more, if it is 99.6% or more, the treatment is 550 ° C or more, and in the case of a nitrogen atmosphere, 400 ° C if the DXN (TEQ) removal rate is 99% or more. It is preferable to perform the above treatment, and if necessary 99.9% or more, the treatment at 550 ° C. or more.

According to the present invention, there is thus no risk of secondary pollution such as scattering due to storage of contaminated soil or waste.
A method for cleaning XN-contaminated soil is provided.

[Brief description of drawings]

FIG. 1 is a flow sheet showing an example of a method for cleaning dioxins-contaminated soil by the low temperature heating method according to the present invention.

[Explanation of symbols]

(1): Screen (2): Indirect heating kiln (3): Secondary combustion furnace (4): High temperature dust collector (5): Heat exchanger (6): Induction fan (7): Chimney (8): DeNOx catalyst device (9): Cooling feeder (10): Dust carrier

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Osamu Hamano             1-89 Minami Kohoku 1-89, Suminoe-ku, Osaka             Standing Shipbuilding Co., Ltd. (72) Inventor Shozo Umemura             1-89 Minami Kohoku 1-89, Suminoe-ku, Osaka             Standing Shipbuilding Co., Ltd. F-term (reference) 2E191 BA12 BB00 BB01 BD11                 4D004 AA21 AA41 AB07 CA22 CA36                       CC02

Claims (4)

[Claims] 1. Dioxin contaminants at a temperature of 250 to 7
A method for cleaning dioxin-contaminated soil by a heating method, which comprises heating at 00 ° C. 2. The purification method according to claim 1, wherein the dioxin pollutant is incinerator demolition waste or contaminated soil containing the same. 3. The purification method according to claim 1, wherein the heating temperature is 400 to 550 ° C. 4. The heating atmosphere is an air atmosphere.
~ The purification method according to any one of 3 to 3.