JP2008100166A - Method for separating and recovering pcb, and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for extracting, separating and recovering PCB in order to treating low concentration PCB-containing insulation oil with safety and at a low cost, and to provide an apparatus therefor. <P>SOLUTION: In separating and recovering PCB from the low concentration PCB-containing insulation oil, the method comprises (1) mixing the PCB-containing insulation oil with an aprotic organic polar solvent and separating the insulation oil and the solution of the aprotic organic polar solvent of PCB, (2) adding water and a hydrocarbon solvent to the solution of the aprotic organic polar solvent of PCB to mix and separating the same to water, the solution of the aprotic organic polar solvent and the solution of the hydrocarbon solvent of PCB, and then (3) recovering the hydrocarbon solvent from the solution of the hydrocarbon solvent of PCB and recovering and separating PCB. Also the apparatus used for the method is obtained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a method for separating / recovering PCB from insulating oil containing low-concentration PCB, and an apparatus used therefor.

Halogenated organic substances such as polychlorinated biphenyls (PCBs) and dioxins are generally harmful to humans and often contaminate the environment. In particular, PCB is a serious social problem as an environmental pollutant because it is persistent and remains persistent for a long time. Further, since PCB is a chemically very stable substance, there is a problem that it is difficult to make it harmless upon disposal.

Currently, the methods recognized as waste treatment methods that regulate the treatment of waste oils including PCBs include the high temperature pyrolysis method, dechlorination decomposition method, hydrothermal oxidation decomposition method, reductive thermochemical decomposition method, light A decomposition method and a plasma decomposition method are known. Among these, the dechlorination decomposition method is preferable in that a particularly large and special decomposition apparatus is not required, no harmful by-products are generated, and by-products can be reused.

In general, in the dehalogenation decomposition method, metal halogen, organic alkali metal, catalyst, or the like is mixed with a halogenated organic substance and chemically reacted to replace the halogen in the halogenated organic substance with hydrogen or the like. . However, metals and catalysts used for dehalogenation decomposition are expensive and have drawbacks and problems such as the need to carry out the reaction in an anhydrous organic solvent (see Patent Documents 1 to 3).
JP 2002-756 A JP 2001-269673 A JP-A-8-66494

As a method for detoxifying PCB or the like by a relatively simple operation / means, a method of reducing and dehalogenating by adding metallic calcium to an alcohol solution such as PCB and mixing it has also been proposed (see Patent Document 4). However, this method also has a problem that an organic solvent must be used.
JP 2002-265391 A

There has also been proposed a method in which PCB is mixed with a solvent such as water or acetonitrile and the PCB is treated by electrolysis. This method is excellent because it can detoxify PCBs and the like relatively easily. However, there is a problem that dehalogenation does not always proceed completely if electrolysis is performed using a normal method or apparatus. (See Patent Document 5).
Japanese Patent Laid-Open No. 2002-349591

The present inventor used a diaphragm electrolytic cell in which an anode and a cathode are separated when electrolyzing a halogenated organic substance or a liquid containing the same to perform dehalogenation, and using the ultrasonic wave generating means to remove the halogenated organic substance-containing liquid. Halogenation characterized in that it is emulsified and electrolysis is carried out while utilizing the cavitation effect that is said to create a vacuum state of 1000 atm and 5000 ° C. at normal temperature and pressure, and stirring the liquid by a stirring means. A method for dehalogenating organic substances has been proposed (see Patent Document 6). According to this method, the halogenated organic substance was completely and fully dehalogenated by electrolysis, and recovered and removed as a detoxifying substance.
International Patent Publication No. WO2005 / 92448

By the way, the capacitors and transformers produced before the PCB manufacturing ban uses PCB as insulating oil, and is divided into high-concentration PCB and low-concentration PCB depending on the PCB content. The insulating oil is a high concentration PCB. The condenser uses only PCB without any other oil, and 60% PCB and 40% trichlorobenzene are used for large condensers. On the other hand, in transformer oil for small equipment such as a pole transformer, PCB of about several tens of ppm is used in a large amount of mineral oil, which is called low-concentration PCB.

Currently, many technologies for processing high-concentration PCBs have been developed, and processing of high-concentration PCBs has been started as a business. However, when low-concentration PCBs are processed in the same manner as high-concentration PCBs, the processing costs are high, and there is a policy that the national policy is not to treat them in the same way as high-concentration PCB processing. Therefore, at present, development of a method for treating low-concentration PCB at low cost is desired, and dehalogenation of halogenated organic substances by electrolysis proposed by the present inventor is a very promising method. However, when the target is a mixture of a large amount of mineral oil and low-concentration PCB, there is a problem that the method by electrolysis cannot be applied suitably.

An object of the present invention is to provide a PCB extraction / separation / recovery method for processing insulating oil containing PCB having a relatively low concentration at a safe and low cost. In particular, the present invention provides a method for extracting, separating and recovering PCB from insulating oil such as transformer oil as pre-processing of PCB processing by the ultrasonic electrolysis apparatus previously proposed by the present inventor.

According to the first aspect of the present invention, when separating and recovering PCB from insulating oil containing PCB having a relatively low concentration, that is, 1000 ppm or less, (1) insulating oil containing PCB and aprotic The organic polar solvent is mixed to separate the insulating oil from the PCB aprotic organic polar solvent solution. (2) Water and a hydrocarbon solvent are added to and mixed with the PCB aprotic organic polar solvent solution. And a mixture of aprotic organic polar solvent and a hydrocarbon solvent solution of PCB, and then (3) a method of recovering the hydrocarbon solvent from the hydrocarbon solvent solution of PCB and separating and recovering PCB. .

In the invention according to claim 2, when separating and collecting PCB from insulating oil containing PCB of 1000 ppm or less, (1) mixing insulating oil containing PCB, aprotic organic polar solvent and hydrocarbon solvent, A mixed liquid of insulating oil and hydrocarbon solvent and an aprotic organic polar solvent solution of PCB are separated. (2) Water and a hydrocarbon solvent are added to and mixed with the aprotic organic polar solvent solution of PCB. And a mixture of aprotic organic polar solvent and a hydrocarbon solvent solution of PCB, and then (3) a method of recovering the hydrocarbon solvent from the hydrocarbon solvent solution of PCB and separating and recovering PCB.

The invention described in claim 4 includes a mixing stirrer for mixing and stirring an insulating oil containing PCB, an aprotic organic polar solvent, water, and a hydrocarbon solvent, and a PCB connected to the mixing stirrer. A distillation apparatus A for separating a hydrocarbon solvent by distillation and a distillation apparatus B for separating water and an aprotic organic polar solvent by distillation, which are used in the method for separating and recovering PCBs according to claim 1 or 2. Device.

Any of the methods of the present invention is particularly suitable as a pretreatment method for a PCB processing method by the ultrasonic electrolysis apparatus previously proposed by the present inventor. According to the method of the present invention, PCB can be efficiently extracted / separated / recovered from insulating oil such as transformer oil. By using the PCB obtained by this method, a transformer or the like can be obtained by the ultrasonic electrolysis apparatus. When processing a low-concentration PCB, it is not necessary to process other oils together, which significantly increases the processing efficiency and the processing cost. The apparatus of the present invention also provides an apparatus that can be used effectively in such a method.

The subject of the present invention is an insulating oil containing PCB at a low concentration, i.e. 1000 ppm or less, preferably 100 ppm or less. Insulating oil is an oil mainly used in electrical equipment such as transformers and condensers, which is mainly composed of mineral oil, synthetic oil, or mixed oil for the purpose of insulation and cooling of equipment.

In the present invention, the aprotic organic polar solvent is dimethyl sulfoxide, sulfolane, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, acetolitol, N-methylacetamide, hexamethylphosphoric triamide, acetone, Aprotic solvents such as nitrobenzene, pyridine and propylene carbonate. Among these, dimethyl sulfoxide, sulfolane, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, acetolitol, or a mixed solvent thereof is preferable, and dimethyl sulfoxide is particularly preferable.

Moreover, as a hydrocarbon solvent, a liquid thing at normal temperature of C5-C18 is suitable, for example, hexane, heptane, and a cyclohexane are preferable.

The invention described in claim 1 of the present invention is, first, (1) an insulating oil containing PCB and an aprotic organic polar solvent are mixed, and the insulating oil, an aprotic organic polar solvent solution of PCB, (2) Water and a hydrocarbon solvent are added to and mixed with the PCB aprotic organic polar solvent solution, and then separated into a water and aprotic organic polar solvent solution and a PCB hydrocarbon solvent solution; (3) The hydrocarbon solvent is recovered from the hydrocarbon solvent solution of the PCB, and the PCB is separated and recovered. Hereinafter, each process is demonstrated using the flowchart of FIG.

FIG. 1 shows an example in which a trans-oil containing a low concentration of PCB (made of mineral oil other than PCB) is treated with DMSO as an aprotic organic polar solvent and hexane as a hydrocarbon solvent. It was. First, (1) Trans oil is mixed with 1 to 1000 times DMSO and stirred. By this operation, PCB is separated and extracted from mineral oil, dissolved in DMSO, and separated into two layers of upper layer mineral oil and lower layer PCB + DMSO. At this stage, if PCB does not remain in the upper mineral oil, the mineral oil is processed as waste oil, but if PCB remains, the process returns to (1) above and the separation / extraction step by DMSO again. repeat.

Next, (2) water is added to the PCB + DMSO solution and stirred. In this operation, DMSO is mixed with water and PCB is separated or released. Further, hexane is added to a mixed solution of the separated PCB, water and DMSO and mixed and stirred. By this operation, the separated PCB is dissolved in hexane and separated into two layers of PCB + hexane and DMSO + water.

Next, (3) the upper PCB + hexane layer is separated, and hexane is distilled off to separate the PCB. Hexane is recovered and recycled. On the other hand, from the lower layer DMSO + water layer, water is distilled off and DMSO is recovered and recycled. Then, the separated PCB is decomposed by an ultrasonic electrolyzer installed separately.

In FIG. 2, the invention described in claim 2 of the present invention, that is, a transformer oil containing a low concentration of PCB (made of mineral oil other than PCB) is used as DMSO as an aprotic organic polar solvent, Another example was given using hexane as the hydrocarbon solvent. First, (1) Trans oil is mixed with 1 to 1000 times of a mixed solution of DMSO and hexane and stirred. By this operation, it is separated into an upper layer composed of mineral oil and hexane and a lower layer of DMSO in which PCB is dissolved. At this stage, if no PCB remains in the upper mineral oil and hexane layers, the mineral oil and hexane are treated as waste oil, but if PCB remains, return to (1) above again to return to DMSO. Repeat the separation and extraction process. Next, (2) water and hexane are added to the PCB + DMSO solution and stirred. In this operation, DMSO is mixed with water and separated from hexane in which PCB is dissolved.

Thereafter, the PCB is separated by the same processing as in FIG. 1, and is decomposed by a separate ultrasonic electrolyzer.

The method of the present invention can be effectively carried out by using an apparatus as shown in FIG. That is, an insulating oil containing PCB (trans oil), an aprotic organic polar solvent (DMSO), water, and a mixing and stirring device for mixing and stirring a hydrocarbon solvent (hexane), both connected to this, It is an apparatus comprising a distillation apparatus A for separating PCB and hydrocarbon solvent by distillation, and a distillation apparatus B for separating water and aprotic organic polar solvent by distillation.

The mixing and stirring device can be provided with means for introducing each liquid through a pipe or the like from a tank of insulating oil containing PCB, aprotic organic polar solvent, water or hydrocarbon solvent, for example. Further, the distillation apparatuses A and B can be appropriately provided with means for separating the separated product, heating and cooling means, and the like. There are no particular restrictions on the method and means for connecting the mixing and stirring apparatus and the distillation apparatuses A and B, and known ones can be used. As shown in FIG. 3, an aprotic organic polar solvent (DMSO), water, and a hydrocarbon solvent (hexane) can be reused.

The PCB separated or collected by the method / apparatus of the present invention or the collected liquid containing PCB can be treated as follows. The oil after extracting PCB from insulating oil such as transformer oil has a PCB content of 0.5 ppm or less, and can be processed normally as waste oil. Then, the extracted / collected PCB can be carried to a conventional processing facility for processing. Alternatively, the apparatus of the present invention (extractor) for carrying out the method of the present invention on the site where the insulating oil containing PCBs scattered throughout the country is present, and the ultrasonic wave of the PCB already proposed by the present inventor PCB can be easily processed on site by bringing in an electrolyzer.

The ultrasonic electrolysis apparatus for PCB already proposed by the present inventor has a diaphragm electrolytic cell in which an anode and a cathode are separated in electrolyzing a halogenated organic substance such as PCB or a liquid containing the same to perform dehalogenation. While using the ultrasonic wave generation means, the halogenated organic substance-containing liquid is emulsified, and at the same time, utilizing the cavitation effect that is said to create a vacuum state of 1000 atm. This is a method for dehalogenating halogenated organic substances such as PCB, wherein electrolysis is performed while stirring. In this case, it is more efficient to put the halogenated organic substance or a liquid containing the same on the cathode side, apply ultrasonic waves on the cathode side using ultrasonic wave generation means, and perform electrolysis while stirring with the stirring means. is there. It is preferable to use a hydrogen storage metal or alloy as the cathode, and the application of ultrasonic waves and stirring are not always required, and may be performed intermittently depending on the situation.

As electrolysis conditions, although it changes with the state of the halogenated organic substance made into object or its containing liquid, a voltage is normally adjusted in 5-500V and an electric current in the range of 5-100A. For the electrolysis, it is appropriate to use a DC power source. For example, an AC power source of 50 to 60 Hz or a high frequency power source of 1 KHz may be used. In electrolysis, in order to increase the electrical conductivity, a salt such as a hydroxide or chloride of an alkali metal or alkaline earth metal is added to the halogenated organic substance or a liquid containing the same, or a treatment liquid containing them. Addition and electrolysis are also preferred. At that time, for example, the voltage required for water of 200 V is desirable, because it drops to about one tenth of 20 V, and the temperature rise of the treatment liquid can be suppressed. The amount to be added is 1 to 50 g, preferably 3 to 10 g, per liter of the treatment liquid.

The invention already proposed by the present inventor causes a substitution reaction between a halogen of an organic halide and hydrogen generated by electrolysis of water as a reduction reaction at an electrolysis cathode. However, since a reversible reaction may occur at the anode, it is desirable to prevent the reversible reaction by not physically contacting the product at the cathode with the anode. As the method, a diaphragm electrolytic cell that separates the anode chamber and the cathode chamber is used. Examples of diaphragms include ion exchange membranes, organic or inorganic microporous membranes, etc., and appropriate ones can be easily selected in consideration of corrosion resistance, mechanical strength, pore diameter / distribution, electrical resistance, etc. be able to. The shape is not particularly limited as long as it can prevent substances generated and present at the anode and the cathode from being dissolved in the electrolytic solution and mixed by diffusion convection.

A halogenated organic substance such as PCB or a liquid containing the same is used for electrolysis as it is or in the form of an organic solvent solution, an aqueous emulsion, or a mixed solution with water (treatment liquid). For example, in the case of PCB separated and recovered from insulating oil containing low-concentration PCB by the method of the present invention, an appropriate amount of water is added to the recovered PCB or a hydrocarbon solvent solution containing PCB at a high concentration. A mixed solution or an emulsion with an appropriate surfactant may be used, and the obtained solution may be used for electrolysis. In the reaction, of course, the treatment liquid may be stirred by an electric / mechanical stirring means.

When performing a dehalogenation reaction by electrolysis, if an ultrasonic wave is applied to the reaction system using an ultrasonic generator, for example, an ultrasonic generator, the reaction liquid is not only cavitation effect but also halogenated by the ultrasonic wave. Organic matter or other liquid and other liquids form minute clusters by the emulsion effect, and the reaction proceeds more efficiently. As the ultrasonic wave generating means, for example, a known or commercially available ultrasonic wave generating device can be used. The ultrasonic power is about 1 to 100 W, preferably 10 to 40 W per liter of the processing liquid. The ultrasonic wave generation means may be a means for applying vibration to an object with a frequency other than so-called ultrasonic waves such as microwaves.

The reaction temperature is generally conveniently carried out at room temperature, but it can be adjusted in the range from the lowest temperature at which the halogenated organic compound or the liquid containing it does not freeze to the reflux temperature. The reaction time depends on the amount of treatment, but is usually adjusted between 10 and 100 minutes. The reaction atmosphere does not require special consideration and may be an open system and normal pressure. However, in order to avoid the influence of air as much as possible, the reaction may be performed in an inert atmosphere such as nitrogen.

Electrolysis is an electrolytic cell for electrolyzing and dehalogenating a halogenated organic substance or a liquid containing the same, and comprises an anode and a cathode separated by the above-mentioned diaphragm, ultrasonic generating means, and stirring means. This is done using an electrolytic cell. For example, platinum, titanium, or carbon is used as the anode. As the cathode, for example, a metal such as palladium or titanium or an alloy thereof is used. Any ultrasonic generator may be used as long as the treatment liquid is sufficiently emulsified by the emulsion effect and dehalogenation is promoted by the cavitation effect, but an ultrasonic oscillating rod connected to the ultrasonic generator is used. A type that is inserted into the processing solution is suitable. A known or commercially available stirrer may be used as the stirring means. As a processing tank, it is not necessary to use a special tank, and practically, for example, electrolysis can be performed using a general container / device made of stainless steel, glass, or vinyl chloride.

It is preferable to use a hydrogen storage metal or alloy as the cathode. When a hydrogen storage metal such as palladium or a hydrogen storage alloy such as a titanium-iron alloy is used, hydrogen generated by electrolysis is stored in the cathode and then discharged. Hydrogen is preferable because it efficiently substitutes for halogen and contributes to the dehalogenation reaction, and the reduction reaction is carried out efficiently. In this case as well, a method using a diaphragm electrolytic cell is preferable for the electrolysis, and furthermore, a method of applying ultrasonic waves to the treatment liquid and performing electrolysis while stirring using ultrasonic generation means and stirring means is adopted. Then, a more preferable result is obtained.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, in the Example, PCB was measured by GC / MAS method.

Separation / extraction operation was performed according to the flowchart of FIG. (1) 200 ml of DMSO and 250 ml of hexane were added to and mixed with 50 ml of trans oil containing 100 ppm of PCB (made of mineral oil except for PCB). And the upper layer which consists of mineral oil and hexane isolate | separated into two layers, and the lower layer which consists of DMSO solution which melt | dissolved PCB were isolate | separated. The operation of adding DMSO, mixing, stirring, and solution separation was repeated until no PCB was detected in the upper layer. Mineral oil and hexane from which PCB is no longer detected can be reused by separately treating them as waste oil.

Next, (2) 250 ml of water and 188 ml of hexane were added to 250 ml of DMSO solution in which PCB was dissolved, and mixed and stirred. By this operation, DMSO was mixed with water, and PCB and hexane (PCB hexane solution) were separated or released, and thus both were separated. The operation of hexane addition, mixing, stirring, and solution separation was repeated until no PCB was detected in the DMSO and water layers. As shown in FIG. 2, the mixed solution of DMSO and water can be separated from water and DMSO by distillation at 100 to 160 ° C., and DMSO can be reused.

Next, (3) hexane was distilled off from the separated hexane solution of PCB to separate 100 ppm of PCB. Hexane can be recovered and recycled. The separated PCB was subjected to a decomposition treatment as described below through an ultrasonic electrolysis apparatus (apparatus disclosed in Patent Document 6) installed separately.

100 ppm of PCB obtained above was mixed with 100 g of sodium hydroxide and 20 L of water to prepare a treatment solution. Using the electrolytic cell disclosed in Patent Document 6 (the treatment tank is made of stainless steel), this treatment solution is put into the cathode chamber, while the anode chamber is filled with 20 L of an aqueous solution containing 100 g of sodium hydroxide and used as a three-phase power source. The direct current of the power source was used, and electrolysis was performed at normal temperature and pressure for 30 minutes while applying ultrasonic waves. The average voltage of electrolysis was 20V, and the average current was 50A. As a radio wave bar as an ultrasonic wave generating means, a metal bar having a diameter of 45 mm and a length of 35 cm was used, and an ultrasonic wave of 20 KHz was applied thereto. The ultrasonic power was 255 W on average. The applied voltage in electrolysis was almost constant for 30 minutes, but the current and ultrasonic power gradually increased. The treatment liquid in the cathode chamber was stirred 1400 times / m using a commercially available mixer. The concentration of PCB in the treatment liquid after electrolysis was 0.5 ppm or less, which was significantly reduced compared to 100 ppm before electrolysis.

According to the method of the present invention, oil after extracting PCB from insulating oil such as transformer oil can be processed normally as waste oil, and the extracted / collected PCB can be transported to a conventional processing facility for processing. It becomes possible. Alternatively, an apparatus (extractor) for carrying out the method of the present invention at a site where insulating oil including PCBs scattered throughout the country is present, and an ultrasonic electrolysis apparatus for a PCB already proposed by the present inventor PCB can be easily processed on site. According to the method and apparatus of the present invention, transformer oil and other PCB-containing liquids containing PCB or the like, which has been a problem in recent years, can be treated with a relatively simple method and apparatus, and therefore very economically. . In addition, since the operation is performed at normal temperature and pressure, it is safe and can be rendered harmless by a clean process using water and electricity, so its utility value is very large in industry and environment.

It is a flowchart which shows an example of the flow of separation / extraction of PCB of the method of this invention. It is a flowchart which shows the other example of the isolation | separation / extraction flow of PCB of this invention method. It is a figure which shows an example of the apparatus used for implementation of the method of this invention.

Claims (4)

When separating and recovering PCB from insulating oil containing PCB of 1000 ppm or less, (1) Insulating oil containing PCB and aprotic organic polar solvent are mixed, and insulating oil and PCB aprotic organic polar solvent (2) Water and a hydrocarbon solvent are added to and mixed with the aprotic organic polar solvent solution of PCB, and the mixture is separated into a mixture of water and aprotic organic polar solvent and a hydrocarbon solvent solution of PCB. Then, (3) a method of recovering a hydrocarbon solvent from the hydrocarbon solvent solution of the PCB and separating and recovering the PCB. When separating and recovering PCB from insulating oil containing PCB of 1000ppm or less, (1) Mixing insulating oil containing PCB, aprotic organic polar solvent and hydrocarbon solvent, and mixing insulating oil and hydrocarbon solvent And an aprotic organic polar solvent solution of PCB. (2) Water and a hydrocarbon solvent are added to and mixed with the aprotic organic polar solvent solution of PCB, and water and an aprotic organic polar solvent solution are mixed. Separating the mixture into a hydrocarbon solvent solution of PCB and then (3) recovering the hydrocarbon solvent from the hydrocarbon solvent solution of PCB and separating and recovering PCB. The method for separating and recovering PCB according to claim 1 or 2, wherein the aprotic organic polar solvent is dimethyl sulfoxide, sulfolane, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, acetritryl or a mixed solvent thereof. An insulating oil containing PCB, an aprotic organic polar solvent, water, a mixing and stirring device for mixing and stirring a hydrocarbon solvent, and a PCB and a hydrocarbon solvent, both connected to this, for separating by distillation An apparatus used in the method for separating and recovering PCBs according to claim 1 or 2, comprising a distillation apparatus A and a distillation apparatus B for separating water and aprotic organic polar solvent by distillation.

Images