JPH11286463A - Recovery of pcb-containing oil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for efficiently recover PCB-containing oil without adverse effect on environment, when PCB-containing oil remaining in the gaps between respective silicon steel plates constituting the iron cores. SOLUTION: The iron cores 1 that are formed by laminating a plurality of silicon steel plates in which PCB-containing oil remain between them are soaked in a solvent that is kept at a lowered temperature by indirectly cooling with a coolant. Then, the iron cores are crushed with a crusher, the crushed iron cores are washed with a solvent using a washer whereby the PCB- containing oil is eluted in the washing solvent. Finally, the PCB-containing oil is separated from the washing solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PCB used as an electrical insulating oil in a component of a transformer.
The present invention relates to a method for recovering (polychlorinated biphenyl) -containing oil.

[0002]

2. Description of the Related Art PCBs have properties such as chemical stability, heat resistance, and high insulation properties. These properties are utilized to make use of electrical insulating oils such as transformers and capacitors, pressure-sensitive paper, and machine oils. , Plasticizers and paints. However, the situation of environmental pollution became clear after the Kanemi Yusho incident in 1968, and production, import and use in open-type applications were banned by 1974. Furthermore, in 1992, waste PCB, waste oil including PCB, and PCB contaminants were designated as specially managed industrial waste based on the Waste Management Law, and were required to be stored at business establishments. As a result, a considerable number of transformers are currently stored in business establishments and the like.

The transformer is mainly composed of members such as a coil, an iron core and an insulator, and these members are immersed in PCB-containing oil. As a method of recovering the PCB-containing oil remaining after being absorbed into the iron core after extracting the PCB-containing oil, methods such as solvent washing and vacuum heating (evaporation / recovery) have been studied. The iron core is 300-500mm in length and 3 in width.
The thickness is about 100 to 200 mm, the depth is about 100 to 200 mm, the weight is 30 to 200 kg, and the thickness is about 200 mm. P in the gap of about 0.02mm
The CB-containing oil has penetrated and remains.

[0004] Although a sufficient technique for recovering the above-mentioned residual PCB-containing oil has not been provided yet, if a cleaning method using a solvent is used, even if the iron core is immersed in the solvent, the PC is not removed.
It is difficult for the solvent to penetrate into the gaps between the silicon steel sheets impregnated with the B-containing oil. Some iron cores are coated with a resin such as varnish on the surface, and it is extremely difficult for the solvent to penetrate into the core. Therefore, there is a problem that the PCB-containing oil cannot be sufficiently recovered. Usually, the amount of PCB remaining on the iron core is about 0.1 mg / Kg iron core when the resin such as varnish is applied on the surface, and about 0.25 mg / Kg iron core when the resin is not applied. It is a target. As a pretreatment for solvent cleaning to solve these problems, for example, a method of finely crushing an iron core using a hammer crusher or the like at room temperature can be considered, but crushing suitable for solvent cleaning is obtained. In addition, since it is expected that a large amount of mist including PCB is generated, it is considered that a method of directly crushing the iron core should be avoided as much as possible in consideration of adverse effects on the environment.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a PC which remains in a gap between respective silicon steel plates constituting an iron core.
An object of the present invention is to provide a method for recovering a PCB-containing oil with high efficiency without adversely affecting the environment when recovering the B-containing oil.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to solve the above-mentioned problems, and as a result, as a pretreatment for solvent washing, a solvent which is liquid at room temperature is indirectly heat-exchanged with a refrigerant. After immersing the iron core in a solvent kept at a low temperature, if the iron core in a low temperature state is crushed by a press machine, crushing suitable for solvent washing can be obtained, and a large amount of mist containing PCB is not generated It has been found that PCB-containing oil can be efficiently recovered. That is, according to the present invention, a plurality of silicon steel sheets are laminated, and the iron core in which the PCB-containing oil remains is immersed in a solvent which is indirectly maintained at a low temperature by a refrigerant, then subjected to crushing means, and then crushed. A method for recovering a PCB-containing oil, wherein the PCB-containing oil is eluted into a washing solvent by applying the iron core to a washing means, and the PCB-containing oil is separated from the washing solvent.

In the present invention, the refrigerant is preferably liquid nitrogen, liquefied LNG or liquefied carbon dioxide, and these solvents are indirectly heat-exchanged with the solvent to keep the solvent at a low temperature.
The temperature of the solvent kept at a low temperature is -70 to -50C.
The solvent used may be solidified at a temperature of −70 ° C. or less, and no special difference is recognized in the effect of the iron core crushing even when the temperature is further cooled. At a temperature of −50 ° C. or more, The width of the silicon steel plate, which is a component of the iron core, is 10
It is difficult to crush into strips of up to several tens of mm, and the crushing effect cannot be obtained.

[0008] In the present invention, the iron core is added to a low temperature solvent.
It is preferable to immerse for a period of up to 30 minutes. If it is less than 5 minutes, the temperature inside the iron core will not reach a temperature suitable for crushing.
There is no difference in the effect of cryogenic crushing even after cooling for more than a minute. In the present invention, it is preferable to use the same type of solvent as the solvent and the washing solvent that are kept at a low temperature, and it is preferable to use cumene, amylbenzene, 1,3-diethylbenzene, dipentene or p-cymene as the solvent. The solvent is a hydrocarbon solvent that does not solidify at a temperature of about -70 ° C, and has a flash point of normal temperature or higher and is safe to handle. Furthermore, the boiling point of the solvent is 100 ° C. or higher, it is liquid at room temperature, the solvent does not evaporate when immersed in the iron core, and the boiling point difference between the PCB-containing oil and the solvent, which is a temperature suitable for distillation separation, is required to be about several tens degrees Celsius. Can be

In the present invention, a pressing machine is used as a means for crushing the iron core cooled to a low temperature. The press machine
Since the reciprocating operation is performed at a low speed, no mist including PCB is generated at the time of crushing. Therefore, it is not necessary to consider the influence on the environment. The press may be a commercially available one, and for example, a biaxial press or a triaxial press may be appropriately selected and used.

In the present invention, the temperature for washing the PCB-containing oil may be appropriately set in consideration of the washing effect and safety from the viscosity of the PCB-containing oil and the flash point of the solvent used.

[0011]

Next, the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing the shape of the iron core. The iron core 1 has a space 3 in the center, and a plurality of silicon steel plates 2
Are laminated.

FIG. 2 is a process diagram showing an embodiment of the present invention. The solvent in the immersion tank 4 is indirectly heated by a heat exchanger 9 in which liquid nitrogen, liquefied LNG or liquefied carbon dioxide is circulated. It has been replaced and cooled to a low temperature of -70 to -50 ° C. The iron core 1 is put into the immersion tank 4 and
It is immersed for 30 minutes and is a temperature suitable for crushing.
After being cooled to a low temperature of 50 ° C., it is taken out of the immersion tank 4 and crushed by a press machine 5. The silicon steel sheet, which is a component of the iron core, has a property of breaking in a certain direction, and is crushed into a strip having a width of 10 to several tens of mm for crushing at a low temperature.

The finely crushed iron core is dropped and stored in a washing container 6 installed at the lower part of the press machine 5.
This container 6 is put into a washing tank 7. In the cleaning tank 7, the same kind of solvent as that for cooling the iron core is used. Although not shown, for example, a pipe may be provided in the cleaning tank, and the cleaning tank may be maintained at a desired temperature through hot water.

In the cleaning tank 7, P remaining in the iron core
After the CB-containing oil is sufficiently eluted in the solvent, the solvent is sent from the line 10 through the line 11 to the distillation column 8, which is a means for separating the PCB-containing oil and the solvent, and the PC eluted in the solvent.
The B-containing oil is distilled off from the solvent and sent from line 12 to a storage tank. The solvent from which the PCB-containing oil has been separated is circulated from the line 15 via the line 13 to the immersion tank 4 for cooling the iron core or from the line 14 to the washing tank 7 for reuse.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments. In addition, each Example was implemented according to the process drawing shown in FIG.

Example 1 An iron core whose surface was not coated with a resin such as varnish was used. First, after extracting the PCB-containing oil from the transformer, the core portion composed of the iron core, the coil, and the like was taken out, leaving only the iron core.

Next, cumene as a solvent is liquefied LNG.
The iron core was placed in a dipping bath cooled to -50 ° C, and was dipped for 30 minutes. The iron core immersed at a low temperature was taken out of the immersion tank and crushed by a press. The silicon steel sheet, which is a component of the iron core, was finely crushed into a strip having a width of about 20 mm. At this time, generation of mist including PCB due to crushing was not observed. The finely crushed iron core was transferred to an ultrasonic cleaning tank in which cumen as a cleaning agent was maintained at a temperature of 20 ° C., and washed for 10 minutes. After the washing, the finely crushed iron core was taken out of the washing tank, heated and vacuum-dried. The finely crushed iron core was visually observed, but no residual PCB-containing oil and no residual cleaning solvent were observed.

The washing solvent from which the PCB-containing oil was eluted was separated into the PCB-containing oil and the washing solvent by a distillation apparatus. Since the cleaning solvent separated from the PCB-containing oil by the distillation separation had a purity of 99.5%, the cleaning solvent was circulated to the ultrasonic cleaning tank for reuse, and the PCB-containing oil was transferred to the storage tank and stored.

(1) The finely crushed iron core was washed under the following conditions. Cleaning tank device: Simple ultrasonic cleaning tank YP-600 (trade name) Cleaning solvent: Cumene Cleaning temperature: 20 ° C Cleaning time: 10 minutes Drying device: vacuum dryer YP-552VD (trade name) Heating temperature: 90 ° C Heating time : 10 minutes Vacuum drying time: 5 minutes

(2) The recovery of the PCB-containing oil eluted in the washing solvent was performed under the following conditions. Distillation apparatus: Thin-film evaporator F-70 (trade name) Distillation temperature: 100 ° C. Operating vacuum: 60 Tool Concentration of PCB in cleaning solvent Concentration before distillation: 3% / PCB-containing oil / cumen Concentration after distillation : 97% / PCB-containing oil / cumen Recovery of PCB-containing oil: 99.95% Purity of cumene recovered after distillation: 99.5%

(3) The residual amount of PCB in the PCB-containing oil is:
It was calculated by the following measurement. In the test, a transformer using electric insulating oil containing no PCB was used. After washing with a solvent, the silicon steel plate was cut into 1 cm squares, and the PCB-containing oil was extracted with a 10-fold volume of normal hexane. The extract was concentrated, and the amount of the PCB-containing oil was quantified by gas chromatography. Generally, low concentration PCB contaminated oil is 50mg-P
Because it refers to less than CB / Kg oil, the PCB-containing oil content is
It was calculated from the remaining amount of insulating oil as 50 mg-PCB / Kg oil. The results are shown in Table 1.

Example 2 An iron core whose surface was not coated with a resin such as varnish was used. The immersion bath temperature was -70 ° C, the immersion time was 3 minutes, the cleaning bath temperature was 40 ° C, and the other conditions were the same as in Example 1. The results are shown in Table 1.

Example 3 An iron core having a surface coated with a resin such as varnish was used. The immersion bath temperature was -60 ° C, the washing bath temperature was 40 ° C, and the other conditions were the same as in Example 1. The results are shown in Table 1.

Example 4 An iron core whose surface was not coated with a resin such as varnish was used. Solvent is amylbenzene, immersion tank temperature is -60
C., the temperature of the washing tank was 60 ° C., and the other conditions were the same as in Example 1. The results are shown in Table 1.

Example 5 An iron core whose surface was not coated with a resin such as varnish was used. The solvent was 1,3-diethylbenzene, the immersion tank temperature was -60 ° C, the washing tank temperature was 50 ° C, and the other conditions were the same as in Example 1. The results are shown in Table 1.

Example 6 An iron core whose surface was not coated with a resin such as varnish was used. The solvent is dipentene, the immersion tank temperature is -60 ° C,
The temperature of the washing tank was set to 40 ° C., and the other conditions were the same as in Example 1. The results are shown in Table 1.

Example 7 An iron core whose surface was not coated with a resin such as varnish was used. The solvent is p-cymene, the immersion tank temperature is -60 ° C,
The temperature of the washing tank was set to 40 ° C., and the other conditions were the same as in Example 1. The results are shown in Table 1.

COMPARATIVE EXAMPLE 1 An iron core whose surface was not coated with a resin such as varnish was used. Immersion tank temperature is -60 ° C, washing tank temperature is -30
C., and the other conditions were the same as in Example 1. Although the crushing was good, the viscosity of the PCB-containing oil was high due to the low washing tank temperature, and the PCB removal rate was 40%.
The results are shown in Table 1.

COMPARATIVE EXAMPLE 2 An iron core whose surface was not coated with a resin such as varnish was used. Immersion tank temperature is -30 ° C, washing tank temperature is 40 ° C
The other conditions were the same as in Example 1. The temperature of the immersion tank was not a temperature suitable for crushing, crushing suitable for washing could not be performed, and the PCB removal rate was 40%. Table 1 shows the results
It was shown to.

COMPARATIVE EXAMPLE 3 An iron core whose surface was not coated with a resin such as varnish was used. The immersion bath temperature was -60 ° C, the immersion time was 1 minute, the washing bath temperature was 40 ° C, and the other conditions were the same as in Example 1. Due to the short immersion time, the iron core did not reach a temperature suitable for crushing, and the PCB removal rate was 40%. The results are shown in Table 1.

COMPARATIVE EXAMPLE 4 An iron core whose surface was not coated with a resin such as varnish was used. Crushing was performed at an ambient temperature of 30 ° C. without immersing the iron core in the immersion tank. The temperature of the washing tank was set to -30 ° C, and the other conditions were the same as in Example 1. Since crushing suitable for washing could not be performed and the temperature of the washing tank was low, the viscosity of the PCB-containing oil was high, and the PCB removal rate was 4%. The results are shown in Table 1.

Comparative Example 5 The core used was not coated with a resin such as varnish on the surface. Crushing was performed at an atmospheric temperature of 25 ° C. without immersion in the immersion tank. The cleaning tank temperature was 40 ° C., and the other conditions were the same as those in Example 1.
Under the same conditions. Since the crushing suitable for washing could not be performed, the PCB removal rate was 20%. The results are shown in Table 1.

[0033]

[Table 1]

[0034]

According to the present invention, since the core is immersed in a low-temperature solvent and then crushed as a pretreatment, no mist including PCB is generated at the time of crushing, and it is not necessary to consider the effect on the environment. When the same type of solvent is used in the immersion tank and the washing tank, the solvent separated in the distillation tower can be circulated to the washing tank or the low-temperature immersion tank and reused.

[Brief description of the drawings]

FIG. 1 is a view showing a shape of an iron core.

FIG. 2 is a flow chart showing the recovery of PCB-containing oil remaining in the iron core by crushing the iron core at a low temperature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Iron core 2 Silicon steel plate 3 Space 4 Immersion tank 5 Press machine 6 Container 7 Washing tank 8 Distillation tower 9 Heat exchanger 10-15 lines

Claims (6)

[Claims] Claims: 1. A plurality of silicon steel sheets are stacked and configured,
The core containing the PCB-containing oil is immersed in a solvent that is indirectly kept at a low temperature by a refrigerant, and then subjected to crushing means. Then, the crushed core is subjected to washing means, and the PCB-containing oil is added to the washing solvent. A method for recovering a PCB-containing oil, wherein the PCB-containing oil is eluted and the PCB-containing oil is separated from the washing solvent. 2. The method according to claim 1, wherein the refrigerant is liquid nitrogen, liquefied LNG or liquefied carbon dioxide. 3. The same kind of solvent is used for the solvent kept at low temperature and the washing solvent, and the solvent is cumene, amylbenzene, 1,3-diethylbenzene, dipentene or p-pentene.
The method for recovering a PCB-containing oil according to any one of claims 1 to 2, which is a cymene. 4. The temperature of the solvent kept at a low temperature is -70.
The method for recovering a PCB-containing oil according to any one of claims 1 to 3, wherein the temperature is in the range of -50C. 5. The solvent whose iron core is kept at a low temperature is 3 to 3 times.
The method for recovering a PCB-containing oil according to claim 1, wherein the PCB-containing oil is immersed for 0 minutes. 6. The method for recovering PCB-containing oil according to claim 1, wherein the means for crushing the iron core is a press machine.