JP2001176731A - Method for reproducing of transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for reproducing a transformer, having an insulation oil contaminated by low concentration of PCB in a short time by removing PCB, without leaving other impurities inside the transformer. SOLUTION: A used insulation oil inside a transformer is pulled out, and the transformer is heated and dried at the temperature that allows an insulating material in the transformer to be reused. Next, new oil is vacuum-injected, so as to remove the PCB in the transformer and to reproduce a transformer. In this method, two operational steps vacuum pressure reduction and a warmed gas supply are repeated at least twice respectively as a heating and drying process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for regenerating a transformer, and more particularly, to easily and economically removing impurities from a transformer in order to reuse a transformer containing an insulating oil containing PCB. On how to do it.

[0002]

2. Description of the Related Art PCBs are once useful materials for use as heat transfer media, insulating oil for electrical equipment such as transformers and capacitors, carbonless paper, lubricating oils, various plasticizers, paints, sealants, and the like. Has been produced. However, the effects on living organisms and the environment became apparent in the wake of the Kanemi Yusho incident, etc., and production was discontinued by 1972. Production and importing were banned by 1974. In addition, use in open applications and use in new applications was prohibited. Some closed systems are still being used. Most of the PCB for the heat medium was recovered, but the PCB for electrical equipment is still being used. After use, it is stored by the employer. However, as the storage of electric devices and the like contaminated with used PCBs has been prolonged, cases of loss or missing of those devices have been reported. Also, PC
The danger that leakage of B or leakage due to other accidents may occur at any time is increasing. already,
According to a survey by the Ministry of Health and Welfare in 1993, about 7% were actually missing. Recently, PCBs have been widely detected in the environment or living organisms, suggesting that they may have entered the environment through various routes. Also, originally P
Among pole transformers that should use insulating oil not containing CB, there is an example in which PCB is mixed for some reason. That is, there is a case in which a PCB-contaminated oil having a low concentration of about 50 ppm or less is contained as an insulating oil. Transformers are required to check the insulation and change the insulating oil if necessary. In a transformer contaminated with PCB, even if the PCB concentration immediately after the replacement of the insulating oil is low, there is a possibility that recontamination due to elution from the impregnating substance such as paper or wood inside may occur over time. If re-contamination cannot be prevented, it cannot be recycled and must be stored or treated as PCB-contaminated equipment. Therefore, when exchanging the insulating oil, it is required to minimize the content of impurities such as PCB in the transformer, especially in the impregnating substance.

[0003] As a method of this, in a published gazette, a step of extracting the regenerated oil of a transformer by a power means or the like,
A step of inverting the transformer and draining oil, a step of heating the insulating material downward at a reusable temperature of the insulating material and forcibly exhausting evaporants, and vacuum-injecting new oil with the opening upward. There has been proposed a method comprising the steps of: Also,
The U.S. patent describes a method in which electrical equipment is depressurized and heated with superheated steam from a solvent, and after the inlet and outlet steam temperatures are equal, the pressure is reduced again to evaporate off the residual insulating oil. Have been.

[0004]

The method proposed in the published gazette has the following problems. -It takes a long time to heat because the heat source temperature of the vacuum heating chamber cannot be increased and the heat transfer efficiency is poor in a vacuum. -In a vacuum, the stirring effect is very small, and the heat transfer is limited to conduction, so the temperature distribution in the transformer becomes more biased. -Since there is no carrier gas, it is difficult to remove evaporated impurities from the vacuum heating chamber. In particular, when the scale is increased, the distance to be moved becomes longer, so that the removal effect tends to decrease. -Since there is no carrier gas and the concentration of impurities in the exhaust gas is high, if there is a low temperature part in the path, the evaporated impurities will condense and become a new pollution source. In the method proposed by the U.S. patent specification,
Since the solvent condenses while the temperature of the electric equipment is low, the condensed solvent needs to be again heated and evaporated. In addition, there is a problem that the solvent may remain in the electric equipment and may become impurities after the injection of new oil. Therefore, the conventional method has a problem that a very long time is required for the regeneration process. There is also a problem that another impurity may remain in the transformer. Therefore, the present invention provides a method for regenerating a low-concentration PCB-contaminated insulating oil transformer in a short processing time by removing PCB without leaving another impurity in a transformer.

[0005]

The present invention has solved the above-mentioned problems by the following means. (1) The old insulating oil in the transformer is extracted, the transformer is heated and dried at a temperature at which the insulating material in the transformer can be reused, and then the new oil is vacuum-injected, so that the PC in the transformer is removed.
In the method of regenerating the transformer by removing B, the heating and drying step includes a vacuum decompression step and a heating gas supply step.
A method for regenerating a transformer, wherein each step is repeated at least twice. (2) The method for regenerating a transformer according to the above (1), wherein exhaust gas generated from the heating and drying step is purified, reheated, and circulated and supplied to the heating and drying step. (3) The method for regenerating a transformer according to the above (2), wherein the gas to be circulated is stored in a pressurized tank during the vacuum depressurization step and is used repeatedly. The method for regenerating a transformer according to any one of (1) to (3), wherein when the liquid is generated and separated, the PCB-containing liquid is subjected to a dechlorination decomposition treatment.

[0006]

FIG. 1 is a process chart showing an embodiment of the present invention. In the embodiment, as shown in the process diagram, old insulating oil in the transformer is extracted (1). There are two ways to remove oil from the transformer:
The pressure may be reduced using a power means such as a pump (2). After discharging as much as possible, it is desirable to leave once for several hours or several days and then discharge again. It may be dropped downward and discharged during standing, but if it is difficult to recover the dripping liquid for a long time, drain as much as possible, then turn the container upward as usual during standing and reinvert it when re-discharging. You may. At the time of discharge, if the ambient temperature is higher than room temperature, discharge may be promoted. The operation of extracting and discharging oil is desirably performed indoors with an air purification device in order to prevent leakage of discharge of insulating oil vapor and the like into the environment during the extraction and discharging process. Transformers that have been left unattended should be sealed again, stored in a closed container, or stored in a room equipped with an air purification device to prevent insulating oil and the like from being discharged into the environment during leaving. desirable. The transformer from which the insulating oil has been removed is heated and dried at a temperature at which the insulating material in the transformer can be reused by circulating a heated gas (3). Heat drying is performed by extracting the oil in the transformer, then carrying the oil into the vacuum drying chamber, and reducing the pressure (4) in the carried vacuum drying chamber.

[0007] The reusable temperature means a temperature at which the insulating material does not substantially undergo thermal denaturation even when subjected to heat. Preferably, it refers to the highest temperature within a range that does not cause thermal denaturation. Examples of the insulating material in the transformer other than the insulating oil include paper and wood, and plastics such as polypropylene. If the insulation is paper or wood, the reusable temperature of the insulation is
The upper limit is about 110 ° C. When plastics such as polypropylene are included, swelling due to residual oil,
In order to prevent deterioration and the like, the upper limit is about 80 ° C. FIG.
FIG. 1 is a flowchart when an embodiment of the present invention is implemented. Transformer filled with old insulating oil is vacuum dried
Carry in 1. In the vacuum drying chamber 11, two steps of a vacuum depressurizing step and a heating gas supply step are repeated at least twice or more until the purification is sufficiently performed. The vacuum decompression step is
Using the pump 12, the inside of the vacuum drying chamber 11 into which the transformer is carried is reduced to a pressure lower than the vapor pressure of the contaminants, thereby evaporating the contaminants. The vaporized vapor is collected by the cooling condenser 13 and the activated carbon 14. It is desirable to reduce the pressure to as low a pressure as possible to promote evaporation of the contaminants. The vacuum depressurizing step and the heating gas supply step may be performed earlier than the vacuum depressurizing step. The first vacuum depressurization step also has the significance of reducing the oxygen concentration in the vacuum drying chamber by eliminating air in the vacuum drying chamber and preventing oxidation during heating.

In the step of supplying the heating gas to the vacuum drying chamber, the transformer may be heated using only the heating gas passed through the heater 15 using the heater 15, but the vacuum drying chamber 11 itself or A heater may be provided inside the vacuum drying chamber 11, and the heater may be used in combination for heating. Due to the presence of the flowing heated gas, the temperature gradient in the vacuum drying chamber 11 is reduced, the heat transfer efficiency is improved, and the object can be quickly and uniformly heated. When a heater is used in combination, the heating gas flows, so that the heating from the heater does not need to rely solely on radiant heat. There is no need to excessively increase the set temperature of the heater, and the possibility that organic substances present in the gas in the vacuum drying chamber 11 are thermally denatured is low. Further, by supplying the heating gas to the vacuum drying chamber 11, the gas flows. As a result, transport and removal of the vaporized contaminants are promoted. Contaminants deeply impregnated in the fine gaps are further promoted when the contaminants in the shallow part of the surface are removed. The exhaust gas emitted from the vacuum drying chamber 11 is not mainly composed of contaminant vapors but mainly composed of a newly introduced heating gas for heating. Due to the low concentration of contaminants,
It does not condense at unexpected locations and become a new source of pollution.
By repeating the two steps of the vacuum depressurization step and the heating gas supply step, contaminants can be quickly removed.
The exhaust gas from the vacuum drying chamber 11 is purified and discharged, or re-heated after purification and circulated and supplied to the vacuum drying chamber as a heated gas. The purifying means may be any as long as it can remove contaminants from the exhaust gas. Usually, a separation method using a cooling condenser 13,
Alternatively, an adsorption treatment method using activated carbon 14 or the like is used. The heating means of the gas to be heated is not particularly limited. A heat exchanger, an electric heater, or the like can be used, but it is preferable that the device has a temperature control function.

The heating gas may be any gas that does not condense in the vacuum drying chamber 11, and air or an inert gas is used. When an inert gas is used as the heating gas, oxidation in the vacuum drying chamber 11 is prevented, and processing can be performed at a higher temperature than when a gas containing oxygen such as air is used. As the inert gas, a nitrogen gas obtained from a nitrogen gas cylinder (inert gas tank 16) is the cheapest and easy, but helium, argon or the like may be used. The inert gas after purifying the exhaust gas from the vacuum drying chamber 11 is recovered, reheated, and circulated again as a heated gas. This reduces the amount of exhaust gas into the environment,
The amount of pollutants that can be emitted can also be reduced. The gas used for circulation during heating is temporarily stored in the pressurized tank during the vacuum depressurizing step. In this case, it can be used repeatedly in each circulation step. Not only the gas consumption can be reduced, but also the amount of exhaust gas discharged into the environment, that is, the amount of pollutants that can be discharged, can be further reduced. In the regeneration of PCB-contaminated transformers, purification of extracted insulating oil and exhaust from the vacuum drying chamber
A B-containing liquid is generated. The PCB concentration in this case is basically the same as the insulating oil concentration in the transformer, and is dechlorinated and decomposed as waste PCB or the like. After repeating heating and decompression,
Inject new oil (5).

[0010]

According to the present invention, which has the above-described structure, a method for regenerating a low-concentration PCB-contaminated insulating oil transformer in a short time by removing the PCB without leaving another impurity in the transformer. Can be provided.

[Brief description of the drawings]

FIG. 1 is a process chart showing one embodiment of the present invention.

FIG. 2 is a flowchart when implementing an embodiment of the present invention.

[Explanation of symbols]

 1 Transformer oil extraction 2 Decompression 3 Heat gas circulation 4 Decompression 5 New oil injection 11 Vacuum drying chamber 12 Pump 13 Cooling condenser 14 Activated carbon 15 Heater 16 Inert gas tank

Claims (4)

[Claims] 1. Extracting the old insulating oil in the transformer, heating and drying the transformer at a temperature at which the insulating material in the transformer can be reused, and then injecting the new oil into a vacuum, A method for regenerating a transformer by removing a PCB, wherein at least two times of a vacuum depressurizing step and a heating gas supply step are repeated at least twice as a heating and drying step. . 2. The method for regenerating a transformer according to claim 1, wherein the exhaust gas generated from the heating and drying step is purified, reheated, and circulated and supplied to the heating and drying step. 3. The method for regenerating a transformer according to claim 2, wherein the gas to be circulated is stored in a pressurized tank during the vacuum depressurizing step and is used repeatedly. 4. The method for regenerating a transformer according to claim 1, wherein when the PCB-containing liquid is generated and separated during the process, the PCB-containing liquid is subjected to a dechlorination decomposition treatment.