JP2000246266A - Decomposition treatment of organohalogen compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To treat even a highly conc. polychlorinated biphenyles, in such a case that an organohalogen compd. contained in electric insulating oil, an org. waste liquid soln. or the like is dechlorinated to be subjected to decomposition treatment, by supplying a soln. to be treated to a reaction tank housing an alkali metal to decompose the organohalogen compd. SOLUTION: When a polychlorinated biphenyl as one example of an organohalogen compd. is subjected to decomposition treatment, at first, insulating oil for adjusting the concn. of a sodium dispersant and polychlorinated biphenyl-containing insulating oil are respectively distilled in distillation devices 4, 2 under vacuum to remove moisture in respective insulating oils. Next, the insulating oil distilled in the distillation device 4 under vacuum is supplied to a sodium dispersant adjusting tank 3 to adjust the concn. of the sodium dispersant and the sodium dispersant-containing insulating oil is supplied to a reaction tank 1. Subsequently, the polychlorinated biphenyl-containing insulating oil is supplied to the reaction tank 1 and the polychlorinated biphenyl in the insulating oil is reacted with a metal sodium in the sodium dispersant to dechlorinate the polychlorinated biphenyl.

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 an organic halogen compound, and more particularly, to a method for decomposing an organic halogen compound such as polychlorinated biphenyl contained in an electric insulating oil, a heat medium, an organic effluent or the like. It relates to a method of chlorinating and decomposing.

[0002]

2. Description of the Related Art As is well known, polychlorinated biphenyls are very stable and hard to be decomposed, and have high insulation (electrical resistance). Used for such insulating materials, heat transfer media, carbonless copy paper, etc., but their use is currently prohibited for environmental reasons.

[0003] However, there have been cases where they have been used for a long time and remain as trace components in organic wastewater and wastewater in addition to the materials themselves, and it is important how these are decomposed and treated. Is an important issue.

As a means for decomposing and treating such polychlorinated biphenyls, generally, incineration is widely used, and the incineration method is recognized as the only treatment method by law. For example, there is a risk of producing other harmful substances such as dioxin, which is not always sufficient from the viewpoint of environmental destruction and safety.Currently, materials and waste containing this compound are being treated. Absent.

Therefore, as another means for solving this,
For example, a method of treating by adding water and metallic sodium to insulating oil containing polychlorinated biphenyl has been developed.

According to this method, as shown in FIG. 3, an insulating oil containing polychlorinated biphenyl is supplied into a reaction tank, and metal sodium is dispersed in the insulating oil. After adding a reaction accelerator such as water and the like, and then separating and extracting the reaction product generated by the reaction between the organic halogen compound and the metallic sodium from the insulating oil, the insulating oil is removed from the extraction tank. It is a method of further separating.

However, according to this method, processing can be performed when the concentration of polychlorinated biphenyl is lower than 1%, but not sufficiently when the concentration is higher than 1%.

The present invention has been made in order to solve such a problem, and an object of the present invention is to enable processing even when polychlorinated biphenyl is at a high concentration.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a means for solving the problem is to store an alkali metal in a reaction tank in advance and then react the alkali metal. An object of the present invention is to supply a liquid to be treated containing an organic halogen compound into a tank to decompose the organic halogen compound.

In the present invention, since the alkali metal is contained in advance before the liquid to be treated containing the organic halogen compound to be treated is supplied to the reaction tank as described above, the organic halogen compound is reduced to 1%. Even in the case of a high-concentration liquid to be treated as contained above, the decomposition treatment of the organic halogen compound can be surely performed.

Various factors can be considered as a reason why the decomposition treatment of the high-concentration liquid to be processed is performed reliably, but before the liquid to be treated containing an organic halogen compound is supplied, Since the alkali metal is supplied, it is presumed that one reason is that the reaction is performed under the condition that the alkali metal is always excessive.

It is preferable that a reaction accelerating substance is contained in the reaction tank together with the alkali metal.

As a reaction promoting substance, for example, isopropyl alcohol is used.

As the alkali metal, for example, sodium is used.

The alkali metal is preferably dispersed in a dispersion medium and used as an alkali metal dispersant. As the dispersant, when the dispersion medium of the liquid to be treated containing an organic halogen compound is, for example, insulating oil, It is preferable to use the same type of insulating oil.

[0016]

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

FIG. 1 is a schematic block diagram of a decomposition treatment apparatus for carrying out a method for decomposing an organic halogen compound as one embodiment.

In FIG. 1, reference numeral 1 denotes adding a sodium dispersant obtained by dispersing metallic sodium powder in insulating oil, and supplying an insulating oil containing polychlorinated biphenyl as an example of an organic halogen compound therein. Is a reaction tank for reacting polychlorinated biphenyl with metallic sodium. To this reaction tank 1, isopropyl alcohol, which is a reaction promoting substance, is further added.

Reference numeral 2 denotes a distillation apparatus for removing water in the insulating oil containing polychlorinated biphenyl in advance by distillation under reduced pressure. The distillation apparatus is provided before the reaction tank 1.

Reference numeral 3 denotes a sodium dispersant adjusting tank for adjusting the concentration of the sodium dispersant added to the reaction tank 1 in advance.

Reference numeral 4 denotes a distillation apparatus for distilling the insulating oil supplied to the sodium dispersant adjusting tank 3, which is provided in front of the sodium dispersant adjusting tank 3.

5 is an extraction tank for separating and extracting reaction products, such as biphenyl and sodium chloride, produced by the reaction between polychlorinated biphenyl and sodium metal from insulating oil using extraction water. It is provided after the tank 1.

Reference numeral 6 denotes a separation device for separating the insulating oil from the extraction tank 5 from the extraction water, and the separation by the separation device 6 is performed by stationary separation.

Next, a decomposition treatment method for decomposing polychlorinated biphenyl as an example of an organic halogen compound with the above-mentioned organic halogen compound decomposition treatment apparatus is shown in FIG.
And FIG.

First, the insulating oil for adjusting the concentration of the sodium dispersant is distilled under reduced pressure by the distillation apparatus 4, and the insulating oil containing polychlorinated biphenyl to be treated is distilled under reduced pressure by the distillation apparatus 2.

As a result, the water of each insulating oil evaporates and the water is removed.

Next, the insulating oil distilled under reduced pressure in the distillation apparatus 4 is supplied to the sodium dispersant adjusting tank 3, where the concentration of the sodium dispersant is adjusted.

Next, the sodium dispersant whose concentration has been adjusted is supplied to the reaction tank 1.

[0029] Isopropyl alcohol is further added to the reaction tank 1.

The inside of the reaction tank 1 is purged with nitrogen gas, and the generated gas is discharged through an activated carbon filter.

Next, an insulating oil containing polychlorinated biphenyl, which is an object to be treated, which has been distilled under reduced pressure, is supplied to the reaction tank 1.

The polychlorinated biphenyl in the insulating oil reacts with the metallic sodium in the sodium dispersant previously supplied to the reaction tank 1, and the polychlorinated biphenyl is dechlorinated.

The reaction between polychlorinated biphenyl and sodium metal is promoted by isopropyl alcohol added in advance.

The reaction between polychlorinated biphenyl and sodium produces an organic by-product such as biphenyl and sodium chloride.

The liquid to be treated containing organic by-products such as biphenyl and the like and sodium chloride produced in the reaction tank 1 is supplied to the extraction tank 5, and water and carbon dioxide gas are supplied to the extraction tank 5. .

In the extraction tank 5, the metallic sodium in the unreacted sodium dispersant becomes caustic soda by the added water and is further neutralized by carbon dioxide.

The liquid to be treated in the extraction tank 5 is supplied to a separation device 6 and separated into an aqueous solution containing by-products such as biphenyl and sodium chloride and an insulating oil by static separation.

The insulating oil separated by the separation device 6 is reused, and the aqueous solution of by-products such as biphenyl and the sodium chloride separated by the separation device 6 is subjected to the next biological treatment step (not shown). Supplied to

(Example) The concentration of polychlorinated biphenyl was 1
%, The test was performed using the treatment method of the above embodiment (Examples 1 and 2) and the conventional treatment method (Comparative Examples 1 and 2).

Further, the treatment method of the above embodiment (Example 3,
The test was performed in Example 4).

The amount of the sodium dispersant was determined in Examples 1-4.
Then 18.0 L, 24.0 L, 49.5 L, 49.5 L respectively.

In Comparative Examples 1 and 2, 6.5
L and 18.1 L.

As a reaction accelerator, isopropyl alcohol was used in Examples 1 to 4 and Comparative Example 2, and water was used in Comparative Example 1.

The amount of isopropyl alcohol was determined in Example 1.
In Nos. 4 to 4, they were 4.86 L, 5.0 L, 19.1 L, and 19.1 L, respectively.

In Comparative Example 2, the amount was 4.36 L.

The amount of water in Comparative Example 1 was 0.15 L.

Table 1 shows the results.

[0048]

[Table 1]

As is apparent from Table 1, the residual concentration of polychlorinated biphenyl was 400 ppb in Comparative Example 1, and the residual concentration in Comparative Example 2 was 400 ppb.
In contrast to 78 ppb, in Examples 1 to 4, it was 20 ppb or less, which is the lower limit of quantification of the gas chromatograph used in this example.

In the above embodiment, metallic sodium was used because of its advantages of being inexpensive and easily available. However, the present invention is not limited to this, and metallic potassium, metallic strontium, metallic lithium, or an alloy thereof may be used. It is possible.

The point is that a dispersant obtained by dispersing an alkali metal in a dispersion medium such as oil may be used.

In this embodiment, isopropyl alcohol is used as the reaction accelerator. However, the type of the reaction accelerator is not limited to this, and for example, ethanol, methanol or the like can be used.

Isopropyl alcohol has many functional groups (reactive groups) and is low in viscosity, so it has excellent reactivity, and is also excellent in safety, such as being used in medicines such as disinfectants. Furthermore, there is an advantage that biodegradability is good.

Further, in the above embodiment, before supplying to the reaction tank 1, an insulating oil containing polychlorinated biphenyl,
Since the insulating oil for adjusting the concentration of the sodium dispersant was distilled under reduced pressure, a favorable effect that water in the insulating oil was suitably removed was obtained. However, such a vacuum distillation step is an essential step of the present invention. is not.

As a means for removing water, a means using a moisture adsorbent such as zeolite can be employed other than distillation under reduced pressure. However, vacuum distillation is preferred in that no secondary contaminants are formed.

Further, in the above-described embodiment, since the metallic sodium is dispersed in the dispersion medium such as the insulating oil, the affinity is improved, and a favorable effect that the reaction between the alkali metal and the organic halogen compound is performed more reliably is obtained. However, dispersion in such a dispersion medium is not an essential condition of the present invention.

In addition, a method in which a solid such as soil to which an alkali metal is added is stirred while being heated to a temperature higher than the melting point of the alkali metal, a method in which pulverization and mixing are performed, and a method in which alkali metal vapor is supplied to the solid. It is also possible to disperse sodium in the object.

Further, in the above embodiment, the case of treating polychlorinated biphenyl was described. However, the type of the organic halogen compound to be treated is not limited to the polychlorinated biphenyl of the above embodiment. Such a thing may be used. Also, DDT and BHC
And the like. In short, it is only necessary that the object to be treated contains an organic halogen compound.

Further, in the above-described embodiment, the means for separating the insulating oil by means of stationary separation is used. However, in addition to the stationary separation, the insulating oil is separated by, for example, centrifugal separation, membrane separation, or electrophoretic separation means. It is also possible.

Further, the type of the liquid to be treated is not limited to the insulating oil containing an organic halogen compound as described above, but may be a wastewater, a heat medium or the like. Any material containing an organic halogen compound may be used.

Although the present invention is intended to treat a liquid having a high concentration of 1% or more as described above, the present invention is applied to a liquid having a low concentration of 1% or less. It is also possible to apply.

[0062]

As described above, according to the present invention, before the liquid to be treated containing the organic halogen compound to be treated is supplied to the reaction tank, an alkali metal such as metallic sodium is stored in advance. Therefore, there is an effect that the decomposition treatment of the organic halogen compound can be reliably performed even on a high-concentration liquid to be treated such as containing 1% or more of the organic halogen compound.

When a reaction accelerating substance such as isopropyl alcohol is added, the reaction between the alkali metal and the organic halogen compound is further promoted, and the organic halogen compound can be more reliably decomposed. effective.

Further, since an organic halogen compound such as polychlorinated biphenyl to be treated is contained in insulating oil or the like, when an alkali metal to be added is dispersed in a dispersion medium such as insulating oil or the like, the affinity is low. Thus, the reaction between the alkali metal and the organic halogen compound is performed more reliably.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an organic halogen compound decomposition treatment apparatus as one embodiment.

FIG. 2 is a schematic block diagram showing an organic halogen compound decomposition treatment step as one example.

FIG. 3 is a schematic block diagram showing a conventional process for decomposing an organic halogen compound.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Reaction tank 2 ... Distillation apparatus 3 ... Distillation apparatus 5 ... Extraction tank 6 ... Separation apparatus

Claims (6)

[Claims] An organic halogen compound characterized in that after an alkali metal is previously contained in a reaction tank, a liquid to be treated containing the organic halogen compound is supplied into the reaction tank to decompose the organic halogen compound. Decomposition method. 2. An alkali metal and a reaction accelerating substance are contained in a reaction vessel in advance, and then a liquid to be treated containing an organic halogen compound is supplied into the reaction vessel to decompose the organic halogen compound. A method for decomposing an organic halogen compound. 3. The method according to claim 1, wherein the reaction promoting substance is isopropyl alcohol. 4. The method according to claim 1, wherein the alkali metal is sodium. 5. The method for decomposing an organic halogen compound according to claim 1, wherein the alkali metal is dispersed in a dispersion medium. 6. The method according to claim 5, wherein the dispersion medium for dispersing the alkali metal is an insulating oil.