JP2002012561A - Method for treating organohalogen compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treating method capable of regenerating a medium containing an organohalogen compound in a short process without carrying out troublesome waste-water disposal simplifying treating facility, suppressing treating expense and effectively re-utilizing an alkali component in a method for treatment of organohalogen compound, etc., using an alkali metal, etc. SOLUTION: This method is characterized by: (1) capability of carrying out after treatment after decomposition in a short step without using large scale discharge treatment facility by integrating a step using water in order to remove an alkali metal halide and an excess alkali metal, etc., and recovering water from the resultant alkaline discharge, (2) capability of removing highly polar component by washing a medium with an alkali having certain concentration or above and (3) capability of re-utilizing the alkali component to other step in good operability by controlling concentrated concentration in a concentrating step of alkaline water discharge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for treating an organic halogen compound such as polychlorinated biphenyl.

[0002]

2. Description of the Related Art Organic halogen compounds represented by polychlorinated biphenyls and the like are known as environmental pollutants, and several treatment methods for detoxification have been proposed. Among them, a chemical treatment method using an alkali metal or an alkali metal hydroxide is a treatment method that has received the most attention because it can be treated safely and reliably.

However, the chemical treatment method using an alkali metal or the like involves the following steps: (1) To regenerate a medium containing an organic halogen compound such as an electric insulating oil as an electric insulating oil or a fuel oil; It is necessary to remove the compound and the alkali metal used in a large excess with respect to the organic halogen compound from the medium containing the organic halogen compound. (2) Highly polar components generated by the reaction and deterioration due to long-term storage However, there are problems such as the necessity of removing by-produced high-polarity components such as alkali metal halide compounds in the medium because they are dissolved in the medium.

[0004] Regarding (1), for example, Japanese Patent Laid-Open No. 7-2
No. 23974, a polychlorinated aromatic compound contained in a hydrocarbon oil is reacted with an alkali metal hydroxide in the presence of polyethylene glycol dialkyl ether, and after cooling, excess alkali metal hydroxide is converted to a solid content. It describes recovering, separating water from hydrocarbon oil by adding water, and recovering polyethylene glycol dialkyl ether from the aqueous layer by distillation.

[0005] Also, in Japanese Patent Application Laid-Open No. 9-253602,
When an organic chlorine compound and an excess alkali are stirred and mixed at 100 ° C. to 300 ° C. in an aprotic polar solvent to perform a dechlorination reaction, and after cooling, a solid is generated.
It is described that solid-liquid separation is performed, and an excess alkali component is recovered from a solid content using a lower alcohol, and a protic polar solvent is recovered by distillation.

[0006] Japanese Patent Laid-Open No.
No. 16 discloses a method for recovering inorganic substances from wastes in which organic substances and inorganic substances such as alkalis and salts are mixed, and more specifically, a method for efficiently recovering inorganic substances from residues obtained by decomposing PCBs. Specifically, a mixture of an organic substance and an inorganic substance is neutralized by being placed in the presence of a water-insoluble polar solvent, an acid, and water, and subjected to a pretreatment of extracting a water-soluble organic substance with a water-insoluble polar solvent layer. And that the recovery of inorganic substances is facilitated.

Japanese Patent Application Laid-Open No. 11-92771 discloses that salts and alkalis are contained as impurities, the particle diameter of impurities in waste oil is small, and / or the waste oil is deteriorated and deteriorates with water as a by-product. Waste oil whose impurities cannot be completely removed by solid-liquid separation such as sedimentation, centrifugation, filtration, etc. It is described that, by extraction, more preferably, impurities are previously adsorbed to a treating agent such as acid clay in advance of solid-liquid separation, and furthermore, it can be reused as fuel oil or insulating oil by extraction into water or the like.

[0008]

However, any of these methods has a problem of wastewater treatment because an operation such as washing with water is finally required to remove an alkali metal compound and the like. In addition, it is desired that the post-processing step is as simple as possible in relation to the processing cost, the problem of the processing equipment, and the like. Furthermore, it is conceivable that inexpensive alkali metal hydroxides as industrial raw materials are recovered and reused in the decomposition process, but in consideration of the cost required for recovery and equipment, they can be reused in another safe form. Processing costs can be reduced.

Further, all of the above methods are premised on a treatment method using an alkali such as sodium hydroxide.
There is no description about the post-treatment of the treatment method using an alkali metal. When an alkali metal is used, as a method for removing the excess alkali metal, it is difficult to separate and recover the alkali metal from the medium. However, this method has a problem of treating a large amount of alkaline wastewater. Conventionally, this alkaline wastewater has to be discharged into the environment after wastewater treatment such as activated sludge treatment after neutralization treatment. However, such a wastewater treatment requires a large-scale treatment facility and has a problem that the subsequent management cost is large.

From the above, the present invention provides a method for treating an organic halogen compound or the like using an alkali metal or the like.
A processing method that can regenerate a medium containing an organic halogen compound in a short process without complicated wastewater treatment, and furthermore, simplifies the processing equipment, reduces the processing cost, and effectively reuses the alkali component. The purpose is to provide.

[0011]

The present inventors have conducted intensive studies to solve the above-mentioned problems. As a result, (1) water was used for removing alkali metal halides and excess alkali metals, and the obtained alkaline By incorporating a process to recover water from wastewater, post-processing after decomposition can be performed in a short process without using large-scale wastewater treatment equipment.
(2) The high-polarity component can be removed by washing the medium with an alkali having a certain concentration or higher. (3) In the concentration step of the alkaline wastewater, the operability is improved by adjusting the concentration concentration, and the alkali component can be re-used. They found that they could be used, and completed the present invention.

That is, the present invention includes (I) (1) a step of decomposing an organic halogen compound using an alkali metal or alkali, and (2) a decomposition product of the organic halogen compound by adding water after the decomposition is completed. A step of washing the medium with water, (3) a step of collecting water and an alkali component from the alkaline washing liquid used in the water washing, (4) a decomposition of an alkali metal, and a decomposition product of an organic halogen compound, using the collected water excessively. A method for treating an organic halogen compound, comprising washing the medium with water, or having a step of reusing it in a step of decomposing the organic halogen compound using an alkali metal or alkali,

(II) The method for treating an organic halogen compound according to (I), wherein the alkali metal is a sodium dispersion, and (III) a method for keeping the alkali concentration of the alkaline washing water used for washing constant. The method for treating an organic halogen compound according to (I), wherein water is added. (IV) The method for treating an organic halogen compound according to (III), wherein the alkali concentration is 10 to 40% by weight;

(V) In the step of recovering water and an alkali component from the alkaline washing liquid used for washing with water,
The method for treating an organic halogen compound according to (I), wherein the alkali component is concentrated to 54 to 65% by weight using an evaporator and discharged from the evaporator at 60 ° C or higher.
(I) The method for treating an organic halogen compound according to (I), wherein a thin film descending evaporator is used in the step of recovering moisture and an alkali component from the alkaline cleaning liquid used for the water washing.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The organic halogen compound to be subjected to the decomposition treatment of the present invention includes, for example, polychlorinated biphenyl (hereinafter abbreviated as PCB in the text), polychlorodibenzodioxin, polychlorodibenzofuran, 1,2,2 3
Hardly decomposable organic halogen compounds such as -trichloro-4'-nitro-biphenyl ether, polychlorinated benzene, and chlorofluorocarbon. These compounds are substances that are regulated for release into the environment and must be disposed of after decomposing the halogen moiety. PCB is a compound widely used in capacitors as an electrical insulator. After use, it is removed from the capacitor and stored, but remains as a contaminant in electrical insulating oil that was subsequently used as a substitute. .

Examples of the alkali metal used in the present invention include lithium, sodium, potassium, rubidium, cesium, and alloys thereof. In consideration of ease of handling and reactivity, sodium is considered as an alkali metal. Most preferably, a sodium dispersion is preferable in consideration of reactivity. The sodium dispersion can be produced by a known method. Metallic sodium can be prepared by converting liquid sodium into aliphatic hydrocarbons such as paraffin and decalin, aromatic hydrocarbons such as toluene and xylene, kerosene, and electric insulating oil (trans oil). ) In a solvent such as
A method of heating and melting at 0 ° C. is used. In particular, sodium dispersions produced in electrical insulating oil are excellent in stability, dispersibility and reactivity. In addition, electrical insulating oil is Japanese Industrial Standard J
IS2380 is also an oil for electrical insulation used for one to seven types of capacitors and the like described, among which the first type of electrical insulating oil is preferred.

The solvent of the sodium dispersion used for the decomposition reaction may be the same as or different from the solvent used for the decomposition reaction of the organic halogen compound. In addition, a dispersant such as aluminum stearate or an anti-agglomeration agent may be added in advance. It is not necessary to add.

Any concentration of alkali metal in the alkali metal dispersion can be used.
% Is preferable. The average particle size of the alkali metal dispersion is preferably 20 μm or less, more preferably 10 μm or less. The addition amount of the alkali metal dispersion is 1 to 50 equivalents per 1 mol of halogen atom in the organic halogen compound,
Preferably, 1.05 to 20 times equivalent is used.

Specific examples of the alkali include lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, sodium hydrogen carbonate, magnesium hydroxide, potassium t-butoxide and the like. It is preferable to use one or more selected from these groups, and two or more may be used in combination. The properties are not particularly limited, and any of granules, flakes, powders, and the like can be used. As for the amount of the alkali to be added, it is preferable to use 10 to 300 equivalents of aromatics such as PCB with respect to, for example, chlorine of a proverbial compound.

In the step of decomposing the organic halogen compound, for example, in the case of decomposing the PCB contained in the electric insulating oil, (1) an alkali such as sodium hydroxide or the like is contained in the electric insulating oil contained in the PCB. A boiling olefin compound, and / or
Or 250 ° C. to 400 ° C., preferably 3 ° C. in the presence of a catalyst.
A method of heating to 20 ° C to 360 ° C, (2) 100 ° C to 300 ° C in the presence of an alkali such as sodium hydroxide, an aprotic polar solvent such as polyethylene glycol dialkyl ether or the like in an electrical insulating oil contained in PCB.
C., preferably a method of heating to 150 to 250 ° C.,
(3) Sodium dispersion and P prepared in electrical insulating oil
A method of heating the electrical insulating oil contained in the CB in the range of room temperature to 200 ° C., (4) adding the sodium dispersion prepared in the electrical insulating oil and the electrical insulating oil contained in the PCB to water, low-grade A method of adding an active hydrogen compound such as an alcohol and heating the mixture at room temperature to 200 ° C. can be exemplified.

When the organic halogen compound is not contained in a medium such as a solvent, the decomposition reaction can be carried out directly with an alkali metal or the like in the absence of a solvent. preferable. The solvent to be used is not particularly limited as long as it is a solvent inert to an alkali metal or the like. Specifically, hexane, cyclohexane, an aromatic hydrocarbon such as decalin, or an aromatic solvent such as benzene, toluene, or xylene. Solvents such as aromatic hydrocarbons, kerosene, and electric insulating oil can be exemplified. Also, (4)
Examples of the active hydrogen compound to be added in the method include water,
Examples thereof include low molecular weight compounds such as methanol and acetic acid.
It is preferably used in a molar amount of not more than twice, preferably 0.1 to 1.5 times.

The decomposition reaction is carried out with nitrogen,
It is preferable to carry out under an atmosphere of an inert gas such as argon.
In the present invention, after the decomposition reaction is completed, in order to remove the generated alkali metal halide, excess alkali metal, and the like, the solid-liquid separation or the like is not performed, and the medium containing the decomposition product of the organic halogen compound is directly applied to the medium. It is characterized by adding water. The amount of water to be added is not particularly limited as long as it is not less than an amount capable of dissolving the generated alkali metal halide compound and excess alkali metal and the like, but the distillation step in the subsequent water and alkali component recovery step is stably operated. For this purpose, it is preferable to add water so that the concentration of the aqueous alkali solution is constant regardless of the amount of the alkali metal or the like used. The concentration of the aqueous alkali solution is not particularly limited as long as the concentration is below the concentration at which it solidifies at room temperature. For example, when the PCB in the electric insulating oil is treated with the alkali metal using the electric insulating oil as a solvent, a highly polar component may be generated as described above. This highly polar component is completely or partially dissolved in the electric insulating oil at neutral to weak alkalinity. Therefore, when the electric insulating oil after the treatment is reused, it dissolves the metal halide compound and the like. This can be problematic.

In the present invention, it has been found that this highly polar component, when strongly alkaline, precipitates as a tar-like component insoluble in water and electric insulating oil. That is, the alkali concentration is 10 to 40% by weight, more preferably 15 to 30% by weight.
By washing the medium such as the electric insulating oil after decomposition within the range, liquids are separated without being suspended, and no inorganic substances such as metal halides are dissolved in the medium. Also, in the subsequent distillation step, it is preferable that the amount of water is small in terms of distillation efficiency. The generated tar-like component can be recovered together with the alkali component in the water and alkali component recovery step.

The water and alkali component recovery step is a step of heating an alkaline cleaning solution in which an alkali metal halide or an excess alkali metal is decomposed and dissolved, evaporating and cooling the water, and recovering the alkali component from the residue. It consists of a collecting step. In the step of evaporating water, any of a forced circulation evaporator, a natural circulation evaporator, a thin film evaporator, and a thin film evaporator that are generally used in industry can be used. It can also be carried out using a single evaporator or a multi-effect can. Above all, it is preferable to use a thin film descending evaporator in consideration of the distillation efficiency, the size of the apparatus, and the like. In the step of evaporating and cooling the water, the alkali mist component that is partially scattered can be completely removed, for example, by installing a mist separator before the cooling step.

The components contained in the evaporation residue include alkali metal hydroxides, alkali metal halides and the above-mentioned tar-like substances. When an alkali metal or the like is excessively used for the decomposition, an alkali metal hydroxide which is a residue of the used alkali metal or the like becomes a main component. When these are treated as ordinary industrial waste or reused as a neutralizing agent for incinerated ash, they are preferably transported in a solid state. However, evaporating to dryness or providing a further drying step in the evaporating step involves operational or equipment problems. In the present invention, the alkali component is concentrated to 54 to 65% by weight,
By discharging the evaporator from the evaporator at a temperature of not less than ℃, the concentrated component retains fluidity and is easy to handle, and when cooled in a drum or the like, it is easily solidified at room temperature, which is advantageous for transportation. It was found that the above problem was solved.

The water evaporated by the evaporator is cooled and recovered by a condenser, and the excess alkali metal is decomposed, the medium containing the decomposition product of the organic halogen compound is washed with water, or the organic halogen compound is decomposed using an alkali metal or alkali. Is reused in active hydrogen compounds and the like in the step of decomposing. Also, the steam discharged from the evaporation step is
In the case of a multi-effect tube, it can also be used as a heat source for another effect tube. As a result, water is not directly discharged into the environment, and therefore, there is no need to newly provide a wastewater treatment facility.

[0027]

EXAMPLES The present invention will be described in detail below with reference to examples, but the scope of the present invention is not limited to the examples.

EXAMPLE FIG. 1 is a schematic view showing a step of decomposing an electric insulating oil containing PCB using a sodium dispersion. The reaction is P
The CB-containing insulating oil 4 and the sodium dispersion 6 are charged into the reaction tank 1, and the reaction is carried out while heating to 90 to 100 ° C. in a nitrogen stream while adding an activator 5 such as water. The reaction solution was analyzed, and the reaction was terminated when PCB was no longer detected. The reaction solution was transferred to the post-cooling treatment layer 10 and fresh replenishing water 11 and recovered water 14 were added with stirring so that the alkali concentration became 15%. Since hydrogen is generated by the decomposition of sodium, the reaction is performed under a nitrogen (12) gas stream, and the hydrogen is released together with the nitrogen through the abatement device (13). This operation is repeated twice if necessary. After standing still
Separated into two layers and the treated oil layer 15 is sequentially subjected to an acid neutralization treatment (18,
21), it is stored through activated clay treatment (22, 24). Table 1 shows the properties of the regenerated electric insulating oil.

[0029]

[Table 1]

From the above results, the regenerated oil does not contain sodium chloride, and can be reused as an electric insulating oil and as a fuel oil. The water tank (27) used in the acid neutralization step is supplied to an evaporator, where water is recovered and salts are recovered together with other alkali components. After standing, a tar-like high-polarity component (16) insoluble in both water and treated oil could be separated. When this tar-like component was analyzed, it was the component shown in Table 2.

[0031]

[Table 2]

From the above results, the tar-like component is harmless and can be treated as industrial waste. Also,
When the amount is small, it is recovered together with the alkali component through an evaporation step. After standing, the alkaline cleaning liquid (17) is supplied to the evaporator (28) at a constant speed, concentrated until the alkali concentration becomes 60% by weight, and the liquid (29) is removed from the evaporator at 60 ° C. ), Filled in a drum and allowed to cool to room temperature before solidification. The evaporated water vapor (30) passed through an alkali mist separator (31) to recover an alkali component (32), was cooled by a condenser (33), and was supplied to the treatment tank 10 as recovered water (14). The water recovery was 97% or more. The use of the recovered water had little effect on the post-treatment process.

[0033]

As described above, by using the processing method of the present invention, (1) post-processing and regeneration of a medium such as an electrical insulating oil can be performed in a short process, and (2) equipment cost is required. The wastewater treatment equipment is not required, and (3) there is an unprecedented advantage that there is no need to use an extra treatment in the middle. Thus, the treatment equipment can be made compact and the treatment cost can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a process of decomposing an electric insulating oil containing PCB using a sodium dispersion.

[Explanation of symbols]

 1. Reaction tank 2. Jacket 3. Stir bar 4. 4. PCB-containing insulating oil Activator 6. 6. sodium dispersion Nitrogen 8. Nitrogen removal 9. Reaction solution 10. Post-treatment tank 11. Makeup water 12. Nitrogen 13. (Nitrogen + hydrogen) abatement 14. Collected water 15. Processing oil 16. High polarity component 17. Alkaline washing water 18. Washing / neutralization tank 19. Sulfuric acid 20. Water 21. Separation tank 22. Activated clay treatment tank 23. Activated clay 24. Filtration machine 25. Waste activated clay 26. Regenerated oil 27. Water layer 28. Evaporator 29. (Alkali + salt) component 30. Steam 31. Alkaline mist separator 32. Alkaline component 33. condenser

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C07C 25/18 C07C 25/18 (72) Inventor Yoshiaki Uchida Niigata Prefecture Nakakujo-gun Nakago-mura Oaza Fujisawa 950 Nippon Soda Co., Ltd. Nihongi Plant Production Technology Research Laboratory (72) Inventor Tohru Kondo 1070-3 Fujiwara, Nakago-mura, Nakakushijo-gun, Niigata Nisso Engineering Co., Ltd. Shin-Etsu Office (72) Inventor Susumu Sekiguchi 1-6 Kanda Jimbocho, Chiyoda-ku, Tokyo No. 1 F-term in Nisso Engineering Co., Ltd. (reference) 2E191 BA13 BC01 BD11 4D034 AA27 BA01 CA17 4D076 AA05 AA16 AA24 BA12 FA02 FA12 HA06 JA01 4H006 AA05 AC13 AC26 BA02 BE21

Claims (6)

[Claims] (1) a step of decomposing an organic halogen compound using an alkali metal or an alkali; (2) a step of adding water after the decomposition is completed and washing a medium containing a decomposition product of the organic halogen compound with water; 3) a step of recovering water and an alkali component from the alkaline cleaning liquid used for the water washing;
(4) A step of reusing the collected water for decomposing an excessively used alkali metal, washing a medium containing a decomposition product of an organic halogen compound with water, or decomposing an organic halogen compound using an alkali metal or alkali. A method for treating an organic halogen compound, comprising: 2. The method for treating an organic halogen compound according to claim 1, wherein the alkali metal is a sodium dispersion. 3. The method for treating an organic halogen compound according to claim 1, wherein water is added so that the alkali concentration of the alkaline washing water used for washing with water becomes constant. 4. The method for treating an organic halogen compound according to claim 3, wherein the concentration of the alkali is 10 to 40% by weight. 5. An alkaline cleaning solution used for washing with water,
In the step of recovering water and alkali components, the alkali components are concentrated to 54 to 65% by weight using an evaporator,
The method for treating an organic halogen compound according to claim 1, wherein the organic halogen compound is discharged from the evaporator at 0 ° C or higher. 6. The alkaline washing liquid used for washing with water,
2. The method for treating an organic halogen compound according to claim 1, wherein a thin film descending evaporator is used in the step of recovering moisture and alkali components.