JP2003245655A - Method for treating liquid to be treated containing dioxins - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating a liquid to be treated containing dioxins without reducing the decomposition efficiency of dioxins, even if the liquid to be treated containing the dioxins where a great deal of inorganic salts coexists therein. <P>SOLUTION: The method is for treating the liquid to be treated containing dioxins characterized by transferring the dioxins to a condensed water by conducting the evaporation treatment of the liquid to be treated containing the dioxins. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for treating a liquid to be treated containing dioxins.

[0002]

2. Description of the Related Art Dioxins are contained in the leachate at the final landfill of a refuse incinerator and the smoke effluent of an incinerator. As a method for detoxifying and treating the liquid to be treated containing such _{dioxins, UV-H 2 O 2,} UV- ozone, or accelerate oxidation such as ozone -H ₂ O _2, supercritical water method is there.

However, the above-mentioned liquid to be treated often contains a large amount of not only dioxins but also inorganic salts, and when the liquid to be treated is subjected to accelerated oxidation treatment, the reaction inhibition due to the inorganic salt may occur. Therefore, dioxins cannot be decomposed sufficiently.

On the other hand, even when the liquid to be treated containing dioxins is subjected to supercritical water oxidation, if a large amount of inorganic salt is present, the inorganic salt is not dissolved in the supercritical water, so the inorganic salt is eliminated. However, there is a problem that the supercritical water oxidation treatment must be performed, the structure of the reactor becomes complicated, and the manufacturing cost of the reactor increases.

[0005]

The problem to be solved by the present invention is to solve the above-mentioned drawbacks of the prior art, and to treat dioxins even in a liquid to be treated containing dioxins in which a large amount of inorganic salts coexist. It is an object of the present invention to provide a treatment method that does not reduce the decomposition efficiency.

[0006]

As a result of the studies conducted by the present inventors, surprisingly, although dioxins have a high boiling point, dioxins can be produced by evaporating a liquid containing dioxins. It was found that almost no dioxins remained in the residue after being transferred to the condensed water, and the present invention was completed.

That is, the present invention provides (1) a method for treating a liquid to be treated containing dioxins, characterized in that the liquid to be treated containing dioxins is vaporized to transfer the dioxins into condensed water. (2) The method for treating a liquid to be treated containing dioxin according to (1), characterized in that dioxin transferred to the condensed water is decomposed, (3) the dioxin is decomposed by the accelerated oxidation method. (4) The method for treating a liquid to be treated containing dioxins according to (2), wherein the decomposition of the dioxins is a decomposition by a supercritical water oxidation method (2) The present invention relates to a method for treating a liquid to be treated containing the above dioxins.

[0008]

[Function] Although the reason why dioxins migrate to the condensed water side has not been clarified so far, they may be entrained in water vapor or azeotropic with water. However, since there are almost no inorganic salts in the condensed water, the factor of is small,
It seems that it is mainly due to.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Dioxins in the present invention are defined as polydiodibenzo-para-dioxins (PCDDs) and polychlorodibenzofuran (PCDF) as defined in the "Act on Special Measures against Dioxins".
s), coplanar polychlorobiphenyl (Co-PC
B).

[0010] Examples of the liquid to be treated containing dioxins include leachate in the final landfill of the refuse incineration plant and smoke washing drainage in the incineration facility.

The evaporation treatment in the present invention means that the heated liquid is directly blown into the liquid to be treated to boil the liquid to be treated, or the outside of the container for containing the liquid to be treated is heated to boil the liquid to be treated. It evaporates the treatment liquid and can be performed under normal pressure or reduced pressure.

Dioxins are transferred to condensed water by the evaporation treatment. Since the condensed water does not contain an inorganic salt, dioxins can be efficiently decomposed by treating the condensed water by the accelerated oxidation method or the supercritical water oxidation method.

The method of decomposing dioxins transferred to the condensed water is not particularly limited, and examples thereof include an accelerated oxidation method, a supercritical water oxidation method, a hydrothermal oxidation method, and a catalytic oxidation method. The accelerated oxidation method or the supercritical water oxidation method is preferable because of the high decomposition performance of dioxin.

The accelerated oxidation method in the present invention means ozone,
It is a method of decomposing dioxins by utilizing oxidizing power by adding an oxidizing agent such as hydrogen peroxide water and / or irradiating with ultraviolet rays.

The supercritical water oxidation treatment in the present invention is a method of oxidatively decomposing dioxins in the presence of supercritical water and an oxidizing agent. The supercritical water oxidation reaction is not particularly limited as long as it is a temperature and pressure condition that brings water into a supercritical state, but is, for example, a temperature of 374 ° C. or higher, preferably 500 to 650 ° C., and a pressure of 22 MPa or higher, preferably May be 22 to 25 MPa. As an example of the most preferable temperature / pressure / reaction time (second), 600 ° C. /
25 MPa / 30 s is mentioned. Examples of the oxidizing agent include air, pure oxygen, and hydrogen peroxide. These oxidizing agents may be used in a stoichiometrically required amount or more. The reactor for supercritical hydroxylation decomposition may be either a vessel type or a pipe (tubular) type. Since the target of the supercritical water oxidation is condensed water, it does not contain inorganic salts, and there is no need for equipment or devices for removing inorganic salts.

The inorganic salt is recovered as an evaporation residue by subjecting the liquid to be treated containing a large amount of inorganic salt and dioxins to evaporation. The inorganic salt residue contains almost no dioxins and can be disposed of without any special treatment.

An embodiment of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 is a flow chart showing an embodiment in which dioxins are decomposed and removed by the accelerated oxidation method.

First, the liquid to be treated containing the inorganic salts and dioxins is vaporized. By evaporation, a solid residue containing inorganic salts and condensed water are separated. Dioxins in the liquid to be treated move to the condensed water side, and hardly remain on the solid residue side. Dioxins can be efficiently decomposed by subjecting the condensed water to an accelerated oxidation step (indicated as “AOP step” in FIG. 1). Condensed water that does not contain inorganic salts is treated by the accelerated oxidation method, and no reduction in the treatment effect due to inorganic salts is observed. Since the treatment liquid after the accelerated oxidation step contains almost no dioxin, it can be discharged to the environment. Since the accelerated oxidation method is mainly intended to treat a small amount of organic matter, it is not suitable for a system in which a large amount of organic matter is present on the condensed water side, so it should be decomposed by the supercritical water oxidation method of the following embodiment. Is preferred.

Embodiment 2 FIG. 2 is a flow chart showing an embodiment in which dioxins are decomposed and removed by a supercritical water oxidation method.

First, the liquid to be treated containing the inorganic salts and dioxins is vaporized. Similar to the first embodiment, a solid residue containing inorganic salts and condensed water are separated by evaporation.
Since dioxins migrate to the condensed water side, the dioxins can be efficiently decomposed by subjecting the condensed water to a supercritical water oxidation step (indicated as “SCWO” step in FIG. 2). Since the condensed water does not contain inorganic salts, it is not necessary to add the function of removing inorganic salts to the supercritical water oxidation apparatus, so that the equipment cost can be reduced.

Since the solid residue produced by the evaporation treatment contains almost no dioxins, it can be disposed of as it is.

In the above step, as shown in FIG. 2, the organic substance-containing waste liquid containing no inorganic salt may be combined with the condensed water obtained in the above evaporation step and treated in a supercritical water oxidation apparatus.

[0024]

Example 1 Water containing dioxins and an inorganic salt was charged in a rotary evaporator, and an evaporation operation was carried out under reduced pressure and atmospheric pressure until the mixture was dried.

Dioxins in the stock solution, condensed water and solid residue were analyzed to calculate the mass balance of dioxins. The results are shown in Table 1.

[0026]

[Table 1]

From the results shown in Table 1, it is clear that dioxins hardly remain in the solid residue. Although there is no dioxin emission regulation for solid matter, the amount of dioxins remaining in the solid residue is not a problem level when the environmental standard value of soil of 1000 pg-TEQ / g is used as an index. I understand.

Example 2 Condensed water obtained in Example 1 (condensed water of atmospheric evaporation in Table 1)
Was subjected to a treatment by an accelerated oxidation method using hydrogen peroxide and ultraviolet rays. Hydrogen peroxide of 100 ppm was injected into the liquid to be treated, the treatment was carried out by irradiating with ultraviolet rays at 26.7 kW / m3, and the concentration of dioxins in the treated water was measured and found to be 10 pg-TEQ / L or less. It was Concentration of water discharged from equipment other than currently designated equipment is not specified, but the emission standard for designated equipment is 10 pg-TEQ.
Considering that it is / L, it can be seen that it has decomposed to a level at which it can be discharged.

[0029]

According to the present invention, even in a liquid to be treated containing a large amount of inorganic salts and dioxins, dioxins can be efficiently decomposed by the accelerated oxidation method or the supercritical water oxidation method.

[Brief description of drawings]

FIG. 1 is a flow chart showing an embodiment of a method of the present invention.

FIG. 2 is a flowchart showing an embodiment of the method of the present invention.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C07B 35/06 C07B 35/06 37/06 37/06 C07C 25/18 C07C 25/18 C07D 319/24 C07D 319/24 (72) Inventor Osamu Nakamori 1-8-8 Shinsuna, Koto-ku, Tokyo Organo Co., Ltd. F-term (reference) 4D034 AA11 BA01 CA12 4D037 AA13 AA15 AB14 AB16 BA18 CA11 CA12 4D050 AA13 AB19 BB01 BB02 BB09 BC01 BC02 BC09 BD02 BD03 BD06 CA02 4H006 AA05 AC13 AC26

Claims (4)

[Claims] 1. A method for treating a liquid to be treated containing dioxins, characterized in that dioxins are transferred to condensed water by subjecting a liquid to be treated containing dioxins to an evaporation process. 2. The method for treating a liquid to be treated containing dioxin according to claim 1, wherein the dioxin transferred to the condensed water is decomposed. 3. The method for treating a liquid to be treated containing dioxin according to claim 2, wherein the dioxin is decomposed by an accelerated oxidation method. 4. The method for treating a liquid to be treated containing dioxin according to claim 2, wherein the decomposition of the dioxins is decomposition by a supercritical water oxidation method.