JPH09192641A - Treatment of contaminated soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of chlorine and aromatic compds. and to make a material harmless by adding a sulfur compd.-contg. body to the material contaminated with an organochlorine compd. and heat-treating the admixture in a thermal decomposition furnace. SOLUTION: When the soil contaminated with organochlorine agricultural chemicals or PCB is treated, crushed coal or fuel oil-A W2 is admixed with the contaminated soil W1 , and the admixture is charged into a thermal decomposition furnace 2 from a hopper 1 and thermally decomposed. The gas G generated by the thermal decomposition is burned in a succeeding recombustion chamber 3, and the soil W3 leaving the furnace 2 is heated by a stabilizing burner 4 and discharged from a stoker 5. When a sulfur compd. such as coal and fuel oil-A W2 or a sulfur compd.-contg. body is preferably admixed with the contaminated soil W1 and thermally decomposed, Cl2 reacts with the sulfur compd., hence Cl2 is not generated, dioxins are never formed, and the soil is safely made harmless.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for treating contaminated soil, which is applied to a contaminated soil detoxification treatment apparatus.

[0002]

2. Description of the Related Art Conventionally, the treatment of soil contaminated with organochlorine pesticides and PCB (polychlorinated biphenyl) has been a problem in recent years. Since trace amounts of toxic substances such as substances are easily generated, detoxification treatment is not practically performed, and only conservative treatment such as slightly embedding contaminated soil in the ground and covering the surface with concrete is performed. The reality is that there is none.

[0003]

[Problems to be Solved by the Invention] Organochlorine pesticides and PC
In order to render the soil contaminated with B harmless, it is considered that the method of heating and decomposing organic chlorine-based pesticides and PCBs are combustible components. Since a small amount of dioxins and harmful substances are likely to be generated and there is a problem of such secondary pollution, practical application of the detoxification treatment cannot be achieved. Therefore, the present invention provides a treatment method for detoxifying soil contaminated with organochlorine pesticides and PCBs by a simple treatment method without secondary pollution such as generation of trace harmful substances such as dioxins.

[0004]

[Means for Solving the Problems] In order to achieve the above technical problems, the present invention contaminates organic chlorine compounds such as soil contaminated with organic chlorine pesticides and PCB (polychlorinated biphenyl) and dredged sludge. A sulfur compound-containing body, preferably a ground or liquid combustible material containing an ionic compound, specifically, coal or heavy oil, is added to a substance (hereinafter referred to as contaminated soil), and then heat treatment is performed in a pyrolysis furnace, Preferably, after the thermal decomposition treatment, the gas generated by the thermal decomposition treatment is re-combusted with gas or oil, and by carrying out a multi-stage heat treatment, the generation of aromatic compounds such as chlorine and dioxin is substantially generated. It is characterized by preventing and detoxifying.

That is, according to the present invention, the contaminated soil and the like contaminated with organochlorine pesticides and PCBs are detoxified without generation of trace harmful substances such as dioxins. After adding 10 wt% in advance, heat treatment of contaminated soil in a pyrolysis furnace, preferably after primary combustion, reburning with gas or oil to substantially prevent generation of aromatic compounds such as chlorine and dioxin The detoxification process is performed.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described. Dioxins are generated when organochlorine pesticides and PCBs are heated. This is because Cl ₂ (chlorine) and aromatic compounds (compounds having a benzene ring) are generated in the process of thermal decomposition of organochlorine pesticides and PCBs, and these react with each other to form dioxins. Therefore, if Cl ₂ (chlorine) generated in the thermal decomposition process can be suppressed, dioxins are not generated.

According to the present invention, when a sulfur (S) compound such as coal or heavy oil (A heavy oil) or a sulfur compound-containing body is added to a contaminated soil in advance and mixed, it is C when pyrolyzed.
l ₂ does not react with the sulfur compound to generate Cl ₂ and as a result dioxins cannot be formed. This can be explained by the following reaction. H ₂ S + Cl ₂ + O ₂ → 2HCl + SO ₂ That is, H ₂ S produced in the thermal decomposition of coal or heavy oil containing sulfur (S) compounds is an organochlorine pesticide or PCB.
This is because it reacts with Cl ₂ generated by the thermal decomposition of and cannot contribute to the formation of dioxins.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, unless otherwise specified, the proportions, types, shapes, relative arrangements, etc. of the components or materials described in this embodiment are not intended to limit the scope of the present invention thereto, but merely illustrative examples. Nothing more. FIG. 1 shows a heat treatment furnace for treating contaminated soil according to an embodiment of the present invention, in which W ₁ is the contaminated soil,
W ₂ is crushed coal or heavy oil A, which are contaminated soil W ₁
The crushed coal or A heavy oil W ₂ added and mixed,
From the hopper 1, the contaminated soil W ₃ mixed with coal or A heavy oil is put into the thermal decomposition furnace 2 to perform thermal decomposition treatment. The gas G generated by the thermal decomposition process is burnt in the rear reburning chamber 3. The soil W ₃ 'that has exited the pyrolysis furnace 2 is the burner burner 4
After being heated by, it is discharged from the stoker 5 (W ₄ ). As the auxiliary fuel W ₅ supplied to the auxiliary combustion burner 4, any combustion gas such as propane gas, city gas or oil is used.

Next, Examples and Comparative Examples conducted by using the above apparatus will be described. (Example 1) 0.5 wt% of coal pulverized to 100 μm was added to 100 kg of contaminated soil containing 0.01 wt% of PCB, and mixed, and then heated and decomposed in a thermal decomposition furnace 2 at 850 ° C. for 30 minutes. As a result of taking out the discharged soil and performing a dissolution test, PCB was not detected in the test solution (0.5 μg
/ Liter or less). Further, dioxins were not substantially detected in the exhaust gas discharged from the reburning chamber 3.
(0.05 ng (nanogram) -TEQ / μm ³ or less,
This value (0.05 ng) is the lower limit value that can be analyzed, and it is agreed that it is not substantially detected. )

Example 2 Agrochemical Chlornitrophen (C
100 kg of contaminated soil containing 0.001 wt% of NP)
0.1 liter of heavy oil A was diluted with n-hexane, and then added and mixed. After that, in the thermal decomposition furnace 2 at 850 ℃ 30
Heated for minutes and decomposed. As a result of taking out the discharged soil and performing a dissolution test, no pesticide was detected in the test solution (0.0
5 mg / liter or less). Dioxins were not detected in the exhaust gas from the reburning chamber (0.05 ng-T
EQ / μm ³ or less).

(Comparative Example 1) Pyrolysis furnace 2 was used without adding coal or heavy fuel oil A to contaminated soil containing 0.01 wt% of PCB.
It was heated and decomposed at 850 ° C. for 30 minutes. PCB was not eluted from the discharged soil, but 15 ng-TEQ / μm ³ dioxins were detected in the exhaust discharged from the reburning chamber 3.

Comparative Example 2 Agrochemical Chlornitrophen (C
No coal or heavy oil A was added to the contaminated soil containing 0.001 wt% of NP), and it was heated and decomposed in the thermal decomposition furnace 2 at 850 ° C. for 30 minutes. Chlornitrophen was not eluted from the discharged soil, but 10 ng-TEQ / Nm ³ dioxins were detected in the exhaust gas discharged from the reburning chamber 3.

[0013]

According to the present invention, organochlorine pesticides and PC
The soil and the like contaminated with B can be detoxified by a simple treatment method without causing secondary pollution such as generation of trace harmful substances such as dioxins.

[Brief description of the drawings]

FIG. 1 shows a heat treatment furnace for treating contaminated soil according to an embodiment of the present invention.

[Explanation of symbols]

W ₁ Contaminated soil W ₂ Pulverized coal or heavy oil A W ₃ Soil undergoing thermal decomposition W ₄ Discharged soil after treatment W ₅ Auxiliary fuel (gas or oil) 1 Hopper 2 Pyrolysis furnace 3 Reburning chamber 4 Auxiliary burner 5 Stalker

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location F23G 5/027 ZAB (72) Inventor Satoshi Okuno 12 Nishikicho, Naka-ku, Yokohama Mitsubishi Heavy Industries, Ltd. Yokohama Inside the factory

Claims (1)

[Claims] 1. A pulverized or liquid combustible substance containing a sulfur compound-containing substance, preferably an ionic compound, is added to a pollutant of an organochlorine compound in advance and then heat-treated in a thermal decomposition furnace, preferably in a plurality of stages. The method for treating contaminated soil, which comprises detoxifying treatment by substantially preventing generation of chlorine and aromatic compounds by performing heat treatment of.