KR20100011216A - Method for removing pcbs from transfomer insulation oil and method for washing transfomer - Google Patents

Abstract

PURPOSE: A method for removing PCBs from transformer insulation oil and a method for washing transformer are provided to recycle metals such as iron, copper, and the insulation oil by completely separating PCBs contained in the insulation oil. CONSTITUTION: A method for removing PCBs from transformer insulation oil includes the following steps: storing waste insulation oil collected from a contaminated transformer in a collecting tank(10); transferring the waste insulation oil to a PCBs dissolving tank(20) in which an agitator is installed; dissolving PCBs in DMSO by agitating the waste insulation oil and the DMSO; transferring the dissolved DMSO to a back-extraction tank(30); backward dissolving PCBs in hexane; transferring a hexane layer in a distillation facility(40); and storing the PCBs to a PCBs storage tank(50).

Description

METHODS FOR REMOVING PCBs FROM TRANSFOMER INSULATION OIL AND METHOD FOR WASHING TRANSFOMER}

The present invention relates to a polychlorinated biphenyl separation method and a transformer cleaning method contained in the transformer insulating oil.

In the past, polychlorinated Biphenyls (hereinafter referred to as 'PCBs'), which are excellent in stability and insulation, were used as transformer insulating oils.However, since PCBs are known as carcinogens, their use is currently banned and paraffin-based naphthenes ( Naphthen-based mineral oils are being used.

However, due to problems such as recycling some of the waste insulating oil mixed with PCBs or filling the new insulating oil with the PCBs remaining in the transformer due to the failure of the transformer being completely cleaned, during the transformer regeneration process, many of the transformers currently in use are PCBs. Is expected to be contaminated, but it is not easy to investigate the contamination (currently, more than 20% of transformers are contaminated with PCBs) or even determine if it is contaminated.

In fact, there are millions of transformer transformers currently owned by KEPCO, and the number of transformers installed in other single buildings (factories, large buildings, etc.) is not easy to figure out. There are only 14 analytical institutions in Korea, and the cost of analysis is quite high (about 200,000 won per sample), so it is difficult to determine whether PCBs of all transformers are contaminated.

Especially seriously, this method of treating waste insulating oil contaminated with PCBs was legally possible only by high-temperature incineration, but domestic treatment was not possible due to civil complaints, and all of them were entrusted to foreign countries. However, it is currently being stored after being declared at each business site due to the prohibition of the export of hazardous substances, but it is urgent to seek a treatment plan due to the excessive storage volume. The recently promulgated persistent organic pollutant management method has been proposed and performed as a treatment method that can be chemically or cleansed in addition to high temperature incineration treatment, but the practical application is still insufficient. In the case of nearby Japan alone, the installation of processing facilities for PCBs takes hundreds of billions to hundreds of billions, so it is not easy to install processing facilities in Korea.

KEPCO has entrusted foreign transformers containing more than 50mg / l of PCBs in insulating oil to foreign countries. However, as mentioned above, it is difficult to do so due to international hazardous substance management situation. Currently, PCBs containing more than 2ppm PCBs As it is only in the field of storage or storage, there is a concern about environmental risks from delayed transformer replacement or long-term storage of the closed transformer due to lack of storage capacity.

In the meantime, insulating oil contaminated with PCBs over 50mg / ℓ is being enclosed in transformers, so it is a pity that Korea lacks resources, and it is a pity that the copper outside of expensive transformers and the copper of inner core parts are left abroad. In addition, treating contaminated insulating oil from several mg / l to several tens mg / l as it is, results in waste of enormous cost and resources in terms of quantity, and even if processed domestically within a few years, The installation of a large capacity facility is costly and is likely to bring difficult results in practice.

PCBs treatment technology is known as dechlorination, hydrothermal decomposition, thermochemical decomposition, photocatalytic decomposition, plasma decomposition, and reduction thermochemical decomposition. Currently, facilities using domestic dechlorination are in operation. It is operated as a corporation. In particular, there is no known case of industrializing the technology of recycling insulating oil by selectively separating and extracting PCBs from waste insulating oil.

The present invention has been proposed to solve the above problems, and the object of the present invention is to selectively separate and extract PCBs contained in transformer insulating oil so that only PCBs can be managed and processed separately.

In addition, another object is to allow the insulating oil to be recycled by completely separating PCBs contained in the insulating oil.

It is also another goal to be able to recycle metals such as iron and copper in transformers by completely removing PCBs remaining in the waste transformer.

In order to achieve the above object, the present invention has been conceived that even though PCBs contained in a small amount of insulating oil have insulating properties, they are different from mineral oils and can be selectively separated from mineral oils. DMSO (dimethylsulfoxide, Dimethylsulfoxide) is used as a solvent to separate and dissolve the insulating oil mainly composed of paraffinic and naphthenic mineral oil and PCBs, which are aromatic compounds, and to prevent the second and third pollution. The solvent or wash solution used in the process is recycled in the process.

The polychlorinated biphenyl separation method of the transformer insulating oil according to the present invention, PCBs elution step of mixing and stirring the insulating oil contaminated with PCBs with DMSO; In the previous process, the PCBs dissolved DMSO is separated from the insulating oil, followed by mixing and stirring with hexane (hexane) back extraction of PCBs; And a distillation step of separating PCBs from hexane by distilling hexane in which PCBs are dissolved in the entire process.

DMSO from which PCBs are removed in the PCBs back extraction process is reused in the PCBs elution process, and hexane from which PCBs are removed in the distillation process is reused in the PCBs back extraction process.

On the other hand, the transformer washing method according to the present invention, the first washing step of filling the perchlorethylene (Perchloro Ethlyne) in the transformer shaking and then drying; And a secondary washing step of separating the inner core part from the transformer dried in the previous step, washing the core part and the transformer from which the core part is separated with perchloroethylene, and then drying the transformer.

Preferably, the perchloroethylene used in the processes is distilled after recovery, and the perchlorethylene from which the insulating oil has been removed in this distillation process is reused in the processes, and further separated from the perchloroethylene in the distillation process. The insulating oil is recovered and put into the PCBs elution process of the polychlorinated biphenyl separation method in the transformer insulating oil described above.

Also preferably, the core portion is ultrasonically cleaned using perchloroethylene.

Further, preferably, the transformer is shaken at least once with DMSO, and the core portion separated from the transformer is ultrasonically cleaned at least once with DMSO. And, it is preferable that the DMSO used in this way is recovered and put into the PCBs back extraction process of the polychlorinated biphenyl separation method in the transformer insulating oil described above.

According to the present invention as described above, the PCBs contained in the transformer insulating oil can be almost completely separated and separately stored and consigned.

In addition, the insulating oil can be recycled by completely separating the PCBs contained in the waste insulating oil.

In addition, by completely removing the PCBs remaining in the waste transformer, useful metals such as iron and copper can be extracted from the waste transformer and recycled.

In addition, since the DMSO, hexane and perchloroethylene used in the above processes are all recovered and reused in the process, there is no concern about environmental pollution.

Therefore, according to the present invention, there is a shortage of waste transformer storage capacity, which has been raised as a problem in the past, concerns about environmental pollution due to long-term neglecting of the waste transformer, and waste of resources and costs caused by entrusting the entire waste transformer contaminated with PCBs abroad. Can solve all the problems.

Hereinafter, with reference to the accompanying drawings looks at the PCBs separation method and transformer cleaning method in the transformer insulating oil according to an embodiment of the present invention.

A method of separating PCBs from a transformer insulating oil according to an embodiment will be described with reference to FIG. 1.

(1) PCBs elution process

Waste insulating oil collected from transformers contaminated with PCBs is stored in a separate collection tank (10). In order to remove the PCBs, the waste insulating oil stored in the collection tank 10 is transferred to the PCBs dissolution tank 20 in which the stirrer is installed, and then the waste insulating oil and DMSO are mixed and stirred in the PCBs dissolution tank 20 (200). ~ 400rpm) to dissolve PCBs contained in waste insulating oil in DMSO. The mixing ratio of DMSO and waste insulating oil can be properly adjusted according to the concentration of PCBs, and the stirring time may vary depending on the amount of the mixture, but will be approximately 20-30 minutes. On the other hand, since the crystal is formed when the temperature of DMSO is 18 ℃ or less, mixing and stirring is carried out at 20 ℃ or more.

As soon as the agitation is completed, separation is started into a waste insulating oil layer (upper layer) and a DMSO layer (lower layer), which is left for a predetermined time, for example, about 1 hour, for complete separation. After standing, the two layers are separated, and the insulating oil in which the upper PCBs are separated is recycled (21), and the DMSO in which the PCBs are dissolved is transferred to the back extraction tank (30) provided with the stirrer. On the other hand, a dye may be added to the DMSO in order to facilitate the distinction between the waste insulating oil layer and the DMSO layer.

(2) PCBs back extraction process

The PCBs dissolved in DMSO were dissolved in hexane by mixing and stirring (200-300 rpm) of DMSO, water, and hexane in which the PCBs were dissolved in the back extraction tank 30. Here, the mixing ratio between DMSO, water and hexane can be appropriately adjusted according to the PCBs concentration in DMSO, for example 1: 1: 1 may be mixed.

After agitation in the back extraction tank is completed for a certain time, for example, about 1 hour, or left standing, it is separated into a hexane layer (upper layer) and a DMSO layer (lower layer) containing PCBs. In addition, DMSO from which PCBs have been removed is transferred to a PCBs dissolution tank for reuse, and the hexane layer in which PCBs are dissolved is transferred to a distillation unit.

(3) distillation process

Heat the hexane dissolved PCBs transferred to the distillation facility, condensate the distilled hexane and transfer it to the back extraction tank for reuse. The remaining PCBs are separately stored and consigned.

Meanwhile, the DMSO and hexane used to dissolve the PCBs are reused in the process so that the PCBs are not leaked to the outside during the execution of the above process to cause secondary or tertiary contamination.

With reference to Figure 2 looks at with respect to the transformer cleaning method according to the first embodiment.

(1) Waste insulating oil collection process

After dismantling the upper lid of the waste transformer, the waste insulating oil filled inside is collected (S10) and stored in a separate waste insulating oil collection tank (10). The waste insulating oil thus collected is transferred to the PCBs dissolution tank 20 in the PCBs separation process described above for separating the PCBs.

(2) DMSO cleaning process

DMSO is filled and sealed inside the waste transformer where the waste insulating oil is collected. Then, by using a shaker (shaker) to shake the intermittent transformer for a certain period of time to remove the PCBs remaining inside the closed transformer (S20).

(3) perchlorethylene washing process

After filling the perchlorethylene as a washing liquid for removing insulating oil in the waste transformer in which the DMSO washing is completed, the waste transformer is intermittently shaken for a predetermined time using a shaker. The shake-transformed lung transformer is dried in an enclosed space (S30).

(4) Dismantling and re-cleaning the waste transformer

After separating the internal core part from the closed transformer transformer in which the perchlorethylene washing is completed (S40), each of the waste transformer housing and the core part is rewashed (S50 to S90).

The waste transformer housing is filled with perchloroethylene to remove residual insulating oil, and then shaken (S50) for a predetermined time with a shaker and dried (S60). The spent perchloroethylene is sent to the distillation plant and the dried waste transformer housing is recycled.

The core part is further washed with perchloroethylene after DMSO washing since insulating oil or PCBs may remain between the parts. DMSO cleaning is an ultrasonic cleaning for effective removal of PCBs, which is subjected to a physical impact (S70) such as cutting, crushing, or deformation, soaked in a DMSO filled ultrasonic cleaner and then ultrasonically cleaned until the PCBs are completely separated (S80). )do. The DMSO ultrasonically cleaned core portion is again washed with perchloroethylene to remove residual insulating oil and then dried (S90), and useful metals such as copper contained in the core portion are recycled.

(5) treatment of washing liquid

All the cleaning liquids used in the transformer cleaning process are reused in the transformer cleaning process or the PCBs separation process in the insulating oil. DMSO used in S20 and S80 process is put into PCBs back extraction process in PCBs separation process. Perchlorethylene (liquid) after used in the S30, S50, S90 process is sent to the distillation as it is, the perchlorethylene gas collected in the drying process is condensed and sent to the distillation. Perchlorethylene distilled from the distillation plant can be reused in the S30, S50, S90 process, and insulating oil separated from the perchlorethylene can be recycled, but it may be left in the PCBs elution process during PCBs separation process to prevent contamination by PCBs. Reseat the PCBs

Referring to Figure 3 looks at with respect to the transformer cleaning method according to a second embodiment. For reference, the second embodiment does not use DMSO, but the present invention is not necessarily limited thereto, but it may be used for washing the already-washed waste transformer even if the degree of contamination of PCBs of waste insulating oil is low or simply. The waste insulating oil collection step (S1), core part separation step (S4), waste transformer housing cleaning step (S5, S6), core part cutting step (S7), distillation step and treatment of the washing liquid are the same as in the first embodiment. Since it is implemented in the same manner, duplicate description thereof will be omitted.

(1) perchlorethylene washing process

Perchlorethylene is filled and sealed inside the waste transformer where the waste insulating oil is collected. And shaking the lung transformer for a predetermined time using a shaker (S2), and then dry the lung transformer. As long as the residual concentration of PCBs inside the transformer is not very high, this shaking wash effectively removes PCBs with oil.

(2) washing process of core part

The core part separated from the closed transformer is a plurality of components coupled to each other, so that insulating oil or PCBs may remain between the components. Therefore, the core portion is cut, crushed, deformed by physical impact, and then deposited in a ultrasonic cleaner filled with perchloroethylene, and ultrasonically cleaned (S8) until the oil and PCBs are completely removed, followed by drying ( S9). The useful metal contained in the core portion is recycled.

(3) treatment of washing liquid

All perchlorethylene used in the transformer cleaning process is reused in the transformer cleaning process. That is, the perchlorethylene collected in the S2 ~ S3, S5 ~ S6, S8 ~ S9 process is sent to the distillation facility, the distilled perchloroethylene is reused in the S2, S5, S8 process, the insulating oil separated from the perchlorethylene Can be recycled, but in order to prevent contamination by PCBs, it is put into the PCBs elution process during the PCBs separation process to re-separate the PCBs that may remain.

In order to confirm the effectiveness of the PCBs separation method in the transformer insulating oil described above, waste insulating oil contaminated with PCBs was introduced into a PCBs dissolution tank equipped with a stirrer at a ratio of 1: 1 with DMSO, and stirred for 20 minutes at 200 to 400 ppm for 1 hour. The experiment was performed to stand still.

Before treatment After treatment 7.21 mg / L Not detected

As shown in Table 1 above, PCBs were not detected in the waste oil layer in the PCBs dissolution tank after DMSO treatment under the condition that the PCBs content in the waste oil before DMSO treatment was 7.21 mg / L.

Before treatment After treatment 345 ppm 1. PCBs concentration in insulating oil: Not detected 2. PCBs concentration in DMSO: 345ppm 4.5 ppm 1. PCBs concentration in insulating oil: Not detected 2. PCBs concentration in DMSO: 4.5 ppm

As shown in Table 2 above, in the condition that the PCBs content in the waste insulating oil before the DMSO treatment is 345ppm, PCBs were not detected in the waste insulating oil layer in the PCBs dissolution tank after DMSO treatment, and 345ppm PCBs were detected in the DMSO layer. In addition, even when the PCBs content in the waste insulating oil was considerably low at 4.5 ppm, PCBs were not detected in the waste insulating oil layer after DMSO treatment, and 4.5 ppm PCBs were detected in the DMSO layer. These results show that PCBs can be almost completely removed even with very low levels of waste insulating oil.

On the other hand, even when the average contamination of PCBs in the transformer is 50mg / L, the total separation and concentration of PCBs in the waste transformer can reduce the amount of PCBs in the waste insulating oil by 5 / 100,000, at least 5 / 10,000.

While specific embodiments of the present invention have been illustrated and described, those of ordinary skill in the art may vary the present invention without departing from the spirit of the invention as set forth in the following claims. It is to be understood that modifications and variations are possible.

1 is a block diagram for explaining a polychlorinated biphenyl separation method in a transformer insulating oil according to an embodiment of the present invention,

2 is a block diagram for explaining a transformer cleaning method according to an embodiment of the present invention;

3 is a block diagram for explaining a transformer cleaning method according to another embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

10: waste oil collection tank 20: PCBs melting tank

30: back extraction tank 40: distillation plant

50: PCBs storage tank

Claims (8)

PCBs elution process of mixing and stirring insulating oil contaminated with PCBs with DMSO; A PCBs back extraction process in which the DMSO in which the PCBs are dissolved is separated from the insulating oil, and then mixed and stirred with hexane; And It includes; distillation step of separating the PCBs from the hexane by distilling the hexane dissolved PCBs in the previous step, DMSO from which PCBs are removed in the PCBs back extraction process is reused in the PCBs elution process, and hexane from which PCBs are removed in the distillation process is reused in the PCBs back extraction process. Way. Filling the perchlorethylene in the transformer shaking and washing first and then drying; A second washing step of separating the inner core part from the transformer dried in the previous step, washing the core part and the transformer from which the core part is separated with perchloroethylene, and then drying the transformer; The method of claim 2, wherein the perchloroethylene used in the processes is distilled after recovery, and the perchlorethylene from which the insulating oil is removed in the distillation process is reused in the processes. 4. The method of claim 3, wherein the insulating oil separated from the perchloroethylene in the distillation process is recovered and added to the PCBs eluting step of the polychlorinated biphenyl separation step of the transformer insulating oil of claim 1. The method of claim 2, wherein the core portion is ultrasonically cleaned using perchloroethylene. The method of claim 2, wherein the transformer is shaken at least once with DMSO. The method of claim 2, wherein the core portion separated from the transformer is ultrasonically cleaned using DMSO at least once. 8. The transformer cleaning method according to claim 6 or 7, wherein the DMSO used in the processes is recovered and put into the PCBs back extraction process of the polychlorinated biphenyl separation process in the transformer insulating oil of claim 1.

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