GB2182925A - Process and apparatus for removing PCB's from electrical apparatus - Google Patents

Abstract

A process for removing polychlorinated biphenyls from electrical apparatus, particularly transformers, to achieve concentration levels of 50ppm or less as required by the EPA uses a dielectric fluid having a relatively low boiling point as compared to polychlorinated biphenyls and other contaminants and in which PCB's are soluble. There is an external cooling loop through which the dielectric fluid is circulated maintaining the temperature and pressure of the transformer within its design limits. There is an external distillation loop where the liquid removed from the transformer is heated to boiling point of the selected dielectric fluid thereby vaporizing the dielectric fluid and leaving the polychlorinated biphenyls in liquid phase in the distillation vessel. The dielectric fluid vapor is then condensed and returned to solubilize remaining PCB's in the transformer.

Description

SPECIFICATION Process and apparatus for removing PCB's from electrical apparatus Background ofthe invention Field of the invention The invention relates in general to electrical inductive apparatus, such as transformers, and more part icularly to the removal of residual polychlorinated biphenyl from the internal components in electrical inductive apparatus.

Description of the priorart Since the early 1930's, electrical transformers used in locations sensitive to fires orfire-damage such as subways, buildings and factories have been constructed with a polychlorinated biphenyl insulating and cooling liquid, which liquids are commonly called PCB's. The PCB's were chosen for these applications because oftheir high dielectric strength and their fire resistant characteristics.

In 1976, the manufacture of PCB was outlawed in the United States (15 U.S.C.A. S2605 (3) (A)(i)) because of evidence of their carcinogenic nature, The Federal Toxic Substances Control Act has made it mandatorythattheuseofPCB(.'sin industry be phased out over a short period of time. The Environmental Protection Agency has determined that PCB concentrations of 50ppm or less in the dielectricfluid of a transformer are considered safefortransformer operation. The EPA has further designated that a PCB transformer may be re-classified as "Non-PCB" if after decontamination is completed (and disengaged) for 90 days, the residual PCB concentration in the dielectric fluid is below 50 ppm.

Because initial PCB concentrations in these transformers was as high as 600,000-1,000,000 ppm and the PCB's impregnate the solid cellulosic insulation (wood and paper) and otheradsorbentinsulating materials used in transformers, merely flushing the transformer with another dielectric fluid or a solvent may have the affect of immediately reducing the PCB concentration to an acceptable level, but after a period of operation, the concentration will rise above the limit set by the EPA due to the concentrated PCB's continuously leaching out ofthe solid insulation.

The prior art purports to teach a method of removing PCB's from transformers through the use of an activated carbon filter located in a thermal siphon attached to th e the transformerwhile it is energized (U.S. Patent No.4,124,834). The activated carbon filters have a finite ability to absorb PCB's. It is therefore necessary to continually change out the activated carbon filters and monitor the concentrations of PCB's. The process is continued until the concentration of PCB in the dielectricfluid is below 50 ppm.

Although able to reach 50 ppm in approximately 3060 days, when disengaged from the tra nsformer, the fluid which is a poor solvent for PCB, rapidly leaches back to concentration well above 50 ppm. To date, this process has been operated continuously on transformers for two (2) to three (3) years without successfully keeping the PCB concentration below 50 ppm after disengagement.

There is also in the prior art a process which appears to suggest circulation of a chlorinated or halogonated aliphatic hydrocarbon vaporthrough the transformer (U.S. Patent No.4,425,949). Equipment required for this method include two pumps, one decanter, onethermosiphoned reboiler, two inert chillers, one condenser, one superheat exchanger, one reservoir and an optional distillation vessel.

The requirement of this quantity and complexity of equipment is apparently dictated by the fact that the transformer cleansing is performed in vapor rather than liquid phase. This magnitude of complexity would obviously create high initial costs, high operating costs and high maintenance costs. Also, the process described in U.S. Patent No.4,425,949 must be practiced while the transformer is out of service because existing PCB transformer are not designed to operate in a dielectric gas atmosphere and the resuIting lack of heat dissipation would cause the transformer to fault or melt down. The inability to operate the transformer while decontamination is taking place precludes the heating of and subsequent expansion ofthe transformerwindings and core. The non-energized condition excludes the vapor cleansing process of U.S.Patent No.4,425,949 from access to internally trapped PCB which will remain there until the transformer is refilled and re-energized.

Summary ofthe invention Afeature and advantage of the present invention resides in the provision for an apparatus and process for removing PCB's from transformers and for maintaining a satisfactorily low level of PCB's therein.

Anotherfeature and advantage of the present invention resides in the provision for both a cost and time efficient apparatus and process that will effectively remove PCB's from a transformer so that the leaching of residual PCB into the dielectricfluid will not exceed 50 ppm.

Anotherfeatu re and advantage of the present in- vention is the provision for an apparatus and process removing PCB's from transformers that does not require constant monitoring.

Yet anotherfeature of the present invention is the provision for an economical apparatus and process for removing PCB's from transformers which is not equipment intensive.

Yet anotherfeature and advantage of the present invention resides in the provision for an apparatus and process which can be used while a transformer is in service without substantially affecting the transformers efficiency or power rating.

Another feature and advantage ofthe present invention resides in the provision for an apparatus and process which can be used while a transformer is not in service.

Astill furtherfeature of the present invention is the availability of apparatus and process for PCB removal which is easily retrofitted on an existing PCB's filled or contaminated transformer.

An additional advantage of the present invention is that the transformer may be placed back into service quickly and the decontamination process allowed to continue without additional interruption of electrical service.

Afurtherfeature ofthe present invention is the provision for an apparatus and process which is of sufficient compactness and lightweight enough to permit access to the PCB transformer vaults which are often characterized as being in remote, hard to reach areas.

These and numerous other numerous features and advantages ofthe present invention will become apparent upon careful reading ofthe detailed description, claims and drawings herein, wherein is described an apparatus and process for removing, col- lecting and isolating PCB's. This is accomplished by the use oftrichlorotrifluoroethane as both a dielectricfluid and a solvent and the connection of two fluid circuuit means to a transformer. Other fluids having similar characteristics of dielectric strength and nonflammability as well as a boiling point much lower than the boiling point of PCB's and in which PCB's are soluble could be used in the process. Perchloroethylene is such a material.

Other suitable dielectric fluid/solvents may include perfluorocyclicether(C6Fl2O), perfluorobicyclo (2.2.1) heptane, perfluorotriethyl amine,monochloropentadecafluorheptane, perfluorodibutyl ether, and perfluoro-nheptane, although testing has not been-performed on the dielectricsto determine: (1)lfPCB'saresolubleinthem; (2) if they are nondestructively compatable with transformer internals; and (3) If they form an azeotropewith PCB's. If PCB's are not soluble in one ofthe above listed dielectrics, or if a particular dielectric will damage the transformer, or if a particular dielectric azeotropes with PCB's, then that dielectric is unsuitable.

The second of these fluid circuit means contains a condenser or other means of cooling through which the dielectric fluid vapor generated by the heat ofthe transformerwill be circulated and the resulting condensate returnedtothetransformertherebyremov- ing latent heat and controlling the internal atmosphere pressure of the transformer while approximately maintaining the temperature of the dielectric fluid at its boiling fluid in the transformer.

Thefirstfluid circuit means contains a distillation means in which the temperature ofthe dielectric fluid is raised to the boiling pointofthe solventtrichlorotrifluoroethane. Advantage is taken of the excess heat generated by the transformer to offset the energy required to distill the solvent. The resulting vapor in the first fluid circuit means is taken overhead from the distillation means to a condenser via a conduit. The condensate is gravitationally transmit- ted via a conduitto atankand pumped backtothe transformerfrom the tank.Because the temperature within the distillation means is maintained atthe boiling point oftrichlorotrifluoroethane, the PCB's, which have a much higher boiling point, remain in liquid phase and are collected at the bottom ofthe distillation means.

Periodicallythe PCB's are drained from the bottom ofthe distillation means to a PCB's waste tank.

Operating the process of the present invention while the transformer is in service is the most effective method of practicing the invention. The porous internals of a transformer expand due to the rise in temperature that occurs when the transformer is in operation. This expansion exposes greatersurface area of the porous internals to the dielectric fluid and allows the PCB's saturated in the porous internals to leach out.

Because the leaching or diffusion rate of PCB from the transformer core is largely affected bytemperature and concentration gradient (difference in concentration between the PCB in the core and the PCB in the dielectric), it is important to reduce the concentration of PCB in the dielectric to a very low value (less than 2 ppm) as rapidly as possible. The invention causes thus to happen within the first one (1) to five (5) days, depending on transformer volume, and then continuously removes (via distillation) any residual PCB that leaches into the low PCB concentrated dielectric. An additional advantage of operating the transformer while decontaminating it is that the fluctuation of electric current through the transformer causes a swelling and contraction (pumping) action that accelerates the release of PCB from its internal windings and insulation material.

Since the first fluid circuit means draws from the bottom the transformer, other soluble contaminants as well as contaminants of a heavy or particulate nature should also be removed from the transformer by the distillation process ofthe first fluid circuit means. Other undesirable contaminants may in clude dust, water, sludge, trichlorobenzene and tetrachlorobenzene.

Brief description ofthe drawings Figure lisa flow diagram of the invention as it is operated in conjunction with an existing PCB transformer.

Figure 2 is a flow diagram of the invention as it is operated in conjunction with an existing PCB transformer showing an alternate embodiment cooling means.

Description of the preferred embodiment Referring now to the drawing, Figure 1 shows an existing transformer to which has been added two fluid circuit means that when operated serve to cool and cleanse the transformer.

For a brief period when the transformer is taken out of service. During this non-operative period, the PCB's are drained from the transformer and the transformer is flushed with a solvent to remove gross residues of PCB and dielectric. That solvent should but is not restricted to being the dielectric fluid which is later used to decontaminate the trans- former. The transformer is then refilled (using trichlorotrifluoroethane as the dielectric fluid) and a partial vacuum pulled on thetransformerto evacuate anyairand/or moisturethat may have been introduced during the flushing and filling stages.

A quick connect fitting 3 is coupled with the existing drain port on thetransformer. The dielectricfluid flows through this quick connectfitting 3 and into a conduit 20. This first fluid circuit means begins by taking dielectric fluid from the transformer and ends by returning dielectric fluid to the transformer.

The first fluid circuit means operates to cleanse the transformer of PCB's. Cleansing is performed by circulating dielectric fluid in liquid phase through the transformer. The PCB's contained in the transformer are soluble in the dielectric fluid and therefore, when the dielectric fluid leaves the transformer in thefirst fluid circuit means, the dielectricfluid is in solution with PCB's. The solution is then distilled. In the distilling operation, the dielectric fluid is vaporized while the PCB's remain in liquid phase. This is because the dielectric fluid has a boiling point significantly lower than the boiling point of PCB's. The boiling pointof the dielectric fluid vapor is then condensed and returned to the transformer where it is able to solubilize more PCB.

During the first several hours of opearation of the process, the concentration of PCB's in the dielectric fluid rises dramatically (20,000-60,000) ppm). This is because the initial flush of the transformer with trichlorotrifluoroethane does not reach the largely unexposed areas of the porous transformer internals.

Therefore, as the transformer heats up during oper- ation, residual PCB'ssaturated ortrapped in the porous internals begin to leach out and go into solution with the dielectricfluid, trichlorotrifluoro ethane.

In the first fluid circuit means,fromthe quickcon nectfitting 3, the dielectric fluid is transmitted via a conduit 20 through a solenoid valve 21 which con trolsflowofthedielectricfluidintothedistillation means 23. Within the distillation means 23 there is a high level sensor 25 and a low level sensor 27. High level sensor25signalsa high level controller29 and a low level sensor27 signals a low level controller31.

The high level controller 29 and the low level con stroller 31 actuatethe solenoid valve 21 so asto maintain a proper liquid level within the distillation means 23. Necessary heat energy required to reach the boil ing point of the dielectric fluid within the distillation means 23 is supplied by an electric resistance coil heater 33. A heat recovery, heat exchangerwhich draws its energy from the exhaust heat from the con denser 37 may be substituted for the electrical resist ance heater. A proper level is any level which allows for a vapor space at the top of the distillation means 23 while maintaining a liquid level in which electric resistance coil heater 33 is completely submerged.

As the dielectric fluid boils, the resulting vapor is transmitted through a conduit 35 into a condenser 37. Condensed dielectric fluid from the condenser37 is conducted via conduit 38 to fluid from the con denser 37 is conducted via conduit 38 to watersepar ator 40 to separate anywaterwhich may have been removed from the transformer from the dielectric fluid. Water thus separated from the dielectricfluid is transmitted to the distillation means 23 through con duit42. The remaining dielectricfluid is collected via conduit 46 in a condensate tank 39. Located nearthe bottom ofthe condensate tank 39 is a suction conduit 41 which feeds a pump 43. There is a high level sensor 45 and a low level sensor 47 located within the condensatetank39.The high level sensor 45 signals a high level controller 49 and the low level sensor47 signals a low level controller 51. The high level controller49 and the low level controller 51 ac tuate the pu m p 43 mai ntaining a proper level within the condensate tank 39. A proper level is any level wherethe pump43 is not pumped dry and thetank 39 is not overflowed. The pump 43 discharges through a pressure check valve 44 and a return conduit 53 backto the transformertying into the existing fill port on the transformer. The pressure check valve 44 in connection with solenoid valve 21,allowsthe distillation portion of the system to operate at atmos pheric pressure or at a different and lower pressure than that at which the transformer operates.This permits the distillation of the dielectric at a lower boiling point (dueto lower pressure) and insure lessen ergyrequirementforboiling aswell as good separation of the dielectric from the contaminant. There is a fill line 54which empties into condensate tank39 through which make-up trichlorotrifluoroethane can be added to replace the volume of PCB's and anytrichlorotrifluorethane removed. Condensate tank 39 yields some distinct advantages to the process.

Although it can be seen that condensate tank 39 can be omitted by merely placing condenser 37 at an elevation above the transformer and draining condenser 37 directly to the transformer, revelation of these advantages will make it clear by condensate tank 37 is part of the preferred embodiment. First, condensatetank37allowsforasurplusofdielectric fluid/solventto be placed in the system initially so that there should be no need to add make-up dielectric fluid/solvent to replace that which exists the system when the still bottoms are drained to the PCB waste tank 69.Also, it allows larger quantities of pure dielectric fluid/solvent to be placed within the transformer during the continuous operation ofthe process while simultaneously allowing larger quantities of PCB contaminated dielectricfluid/solventto be drained to the distillation means 23. This speeds up the entire process by greatly increasing the rate at which PCB's within the transformed are diluted by the dielectric fluid/solvent. Further, omitting condensate tank 39 and pump 43 would necessitate the omission of check valve 44 and the benefits achieved as previously stated by using a check valve 44would also be lost.

Atthebaseofdistillation means 23 there is a con- duit58throughwhich still bottomsaretransmitted to manually operated gate valve 76 which is normally closed, orto solenoid valve 61. Solenoid valve 61 is operated by controller 67 and which receives a signal from temperature sensor 65 located in the vapor space of distillation means 23. As the concentration of PCB's and other higher boiling contaminants in distillation means 23 rises, the boiling point of the solution oftrichlorotrifluoroethane and PCB's also rises which in turn causes a rise in the temperature of the vapor space in distillation means 23.

When temperature sensor 65 senses a temperature of approximately 16SF, controller 67 will open solenoid valve 61 and still bottoms will flow into PCB waste tank 69 via conduit 59. The temperatu re at which controller 67 is set to actuate solenoid valve 61 can be varied over a large range although it should be remembered that separation by distillation is enhanced as the boiling point ofthe solution approaches the boiling point of the dielectricfluid. Certainly, a temperature setting otherthan 1 65'Fwould be selected if a dielectricfluid otherthan trichlorotrifluoroethane was used in the process.As this occurs, a low liquid level will be sensed by low level sensor 27 and lower level controller31 will cause solenoid valve 21 to open allowing additional dielectricfluid to flow into the distillation means 23 and flush the still bottoms which are highly con- centrated in PCB's into the PCB waste tank 69. After the passing of a preset period oftime on timer 73 sufficient to drain and flush the still bottoms, solenoid valve 61 will close and distillation means 23 will resume normal operation. Afterflushing the PCB's already removed from the transformer to the PCB waste tank 69, the dielectric fluid contained in the distillation means 23will contain much fewer PCB contaminants.This will mean thatthe boiling pointofthe solution will again approach the boiling point of pure trichlorotrifluoroethane and therefore, separation by distillation will be at its optimum.

Although it is possible for PCB waste tank 69 to be of a permanent or disposable nature, it is preferable that if be disposable. By making PCB waste tank 69 disposable, it may be removed and replaced by an othertank at anytime during the process, thereby also removing thecontaminant PCB'sfrom the site.

This capability reduces the hazard that may occur if a fire or spill situation were to arise since the majority ofthe PCB's would already have been removed from the site.

Manually operated gate valve 76 allows the dis tillation means 23 to be drained at any time during operation or at the completion of operation via conduit 77.

There is a manuallyoperatedgatevalve75 through which PCB waste tank 69 may be drained.

There is a second fluid circuit means which operatesto cool the dielectricfluid as the dielectricfluid is circulated through itthereby dissipating heat generated by the transformer. The second fluid circuit means also serves to maintainthe pressure inside the transformer within the transformer's operating limits. Note that existing PCB transformers were builtforlow pressure operation (5-7 PSIA) and must have adequate vapor pressure control are accomplished through the use of of a condenser 15. A portion of the dielectric fluid is vaporized bythe heat generated by the operation ofthe transformer. This dielectric fluid vapor is transmitted to the condenser 15 via conduit 17 by convection.Aforced draft system fortransmitting vaporthrough the second fluid circuit means could also be employed where more rapid cooling is required or where elevations prevent the natural rise required for convective cool- ing.

The dielectricfluid condensed to liquid phase by condenser 15 transmitted gravitationally backto the transformer via conduit 19. Removing the latent heat of the dielectric fluid in this manner is an extremely efficient way to cool the transformer. While simultaneously limiting the vapor pressure within the transformer.

There is an emergency pressure vent 85 which is connected to condenser 15 byconduit84. Should a power failure occur, the second fluid circuit means will not serve to cool the dielectric fluid and re- sidual heat remaining inthetransformerwill no be dissipated. This may cause a pressure buildup in condenser 15. In such a situation, emergency pressure vent 85 will open thereby relieving pressure within the condenser. Vapor escaping the condenser 15 is transmitted through conduit 84, emergency pressure vent 85, conduit 86, carbon vaporabsorp- tion column 82,and conduit 83.Vapor absorption column 82 absorbs the dielectric fluid/solvent vapor thereby preventing the flooding of any enclosed area where the transformer may be located with dielectric vapor which can be asphixiating. Further, although it is extremely unlikelythatthetemperature reached in such situation will be sufficientto causeanyvaporiz- ation ofPCB's,thevaporadsorption column 82 will also adsorb any PCB's attempting to migrate with the dielectricvaporthrough emergency pressure vent 85.

An alternative method of cooling the transformer is shown in Figure 2. Here, the second fluid circuit means may accomplish cooling ofthe dielectric fluid through the use of an air or mechanically cooled heat exchanger 16. Dielectricfluid is transmitted to pump 9via quick connect fitting 3, conduittee 5 and conduit 7. There is a temperature sensor 11 located in the conduit 20. The temperature sensor 11 signals a temperature controller 13 which serves to actuate the pump 9. The pump 9 discharges the dielectric fluid through a cooled heat exchanger 15. The die lectric fluid is then circulated through conduit 18 and back to the transformer.The dielectric fluid is circula- ted through this second fluid circuit means by the pump 9 which is controlled by the temperature con troller 13 to maintainthetemperatureofthedielect- rio fluid in the transformer near but below its boiling point.

This alternate method of cooling is particularly useful when there is a potential nucleate boiling situation at the surface of the transformerwindings.

Nucleate boiling is boiling in which bubbleformation is at the liquid-solid interface. It is possible that such a bubble would stretch from one winding to an other thereby displacing the dielectric fluid. lfthis were to occur, it is likely that for high voltage operation there would be damaging arcing between the windings. This alternate method of cooling can be used to prevent nucleate boiling by maintaining the temperature of the dielectric fluid below its boiling point.

In an another alternative embodiment, it can be seen that condenser 15 and condenser 37 shown in Figure 1 could be replaced byasinglecondenserser- ving a dual role of maintaining the temperature and pressure within the transformer and condensing distilleddielectricfluidvaporforreturntothetransformer.

Further, placing such a dual purpose condenser at an elevation above the transformerwould eliminate the need to do any pumping. Vaporwould rise by convection from both the transformer and the distillation means 23 to the dual purpose condenser and the resulting dielectricfluid in liquid phase would flow gravitationally from the dual purpose con denserto the transformer.

It should also be noted that if perchloroethylene is used as the dielectric fluid/solvent in an operating transformer, it may not be necessary to use an external cooling loop. This is because the boiling point of perchloroethylene is significantly higher than the boiling point oftrichlorotrifluoroethane and, depending on the transformer, the heat generated by the operation of the transformer may not be sufficient to boil perchloroethylene. The disadvantage of using perchloroethylene is that PCB's are more difficultto separate from the perchloroethylene because the perchloroethylene has a substantially higher boiling point and latent heat of vaporization than trichlorotrifluoroethane.

In summary, there has been disclosed a method of removing PCB's from transformers relying on distillation, which, except for a brief, initial shut-down period, can, but need not be performed while the transformer is in operation . This is important due to the fact that many existing PCB transformers are in locations that make it impractical if not impossible for replacement or, at least, make it impractical for the transformer to be outofserviceforan extended period.

Additionally the process is extremely energy efficient in that in uses the heat generated by an operating transformer to accelerate the extraction of PCB's. Further, because the dielectricfluid is maintained at temperature approximately equal to its boi ling, the amount of additional heat required for distillation is minimized.

Should it be desired to practice the invention while the transformer is not in service, it may not be neces sarytoinstall or usethe second fluid circuitmeans because the transformer itself would not be adding heat to the dielectric fluid/solvent and vaporization of the dielectricfluid/solventwithin the transformer would not occur. In otherwords,cooling ofthedie lectricfluid/solvent in the transformer would not be required because, in this situation, the dielectric fluid/solventwould not be serving to dissipate the heat generated by an active transformer.

However, practicing the invention in such manner will not be as efficient as practicing the invention while the transformer is active. When the trans former is operating the resulting heat causes expan sion of the transformer internals, especially the internal windings wrapped with cellulosic material thereby allowing more rapid and complete penetration of the dielectric fluid/solvent.

Note that the invention may be practiced on a transformer in non-operating mode at an accelerated rate if an external heat source is used to heat the die lectric fluid/solvent or the transformer core. In either case, the added heat would cause an expansion of transformer internals similarto that described for an operating transformer. However, in such case, care would have to be taken not to overpressure the trans- formerduetotheadded heat causing significant vaporization ofthedielectricfluid/solvent. lfthetem- perature of the dielectricfluid/solvent reaches its boi ling point, it would be necessary to utilize an external cooling means.

It is contemplated that once the transformer is cleansed of PCB's, the dielectric fluid/solvent is drained from the transformer and replaced with another suitable dielectricfluid such as silicon oil. However, itwould also be possible to removethecleansing circuit from the transformer while leaving the coolingcircuitin place. Thiswould allowthetrans- former to be operated on a permanent basis using trichlorotrifluoroethane as the dielectric fluid.

Claims (19)

1. A process for removing polychlorinated bi phenylsfrom both an operating and non-operating electrical appartus comprising: a) Introducing a dielectric fluid in which PCB's and other contaminants are soluble, to the electrical apparatus so thatthe polychlorinated biphenyls contained within the electrical apparatus form a solution with said dielectricfluid; b) Conducting said solution from the electrical apparatus to a cleansing means in the path thereof, so that said dielectric fluid may be separated from the polychlorinated biphenyls and other contaminants; c) Cleansing said solution to thereby separate polychlorinated biphenyls and other contaminants from said dielectric fluid so that said dielectric fluid may be reused in substantially pure form; and d) Recirculating said dielectricfluid backto the el ectrical apparatus for reuse.

2. A process for removing polychlorinated biphenyls and other contaminants from operating and non-operating transformers or other electrical apparatus comprising: a) Introducing a dielectric fluid in which polychlorinated biphenyls and other contaminants are soluble, to the electrical apparatus so that the polychlorinated biphenyls contained within the electrical apparatus form a solution with said dielectric fluid; b) Conducting said solution from the electrical apparatus to a cleansing means in the path thereof, so that said dielectric fluid may be separated from the polychlorinated biphenyls and other contaminants; c) Cleansing said solution to thereby separate polychlorinated biphenyls and other contaminants from said dielectricfluid so that said dielectricfluid may be reused in substantially pure form;; d) Recirculating said dielectricfluid vapor back to the electrical apparatus; and e) Cooling the operating transformer or other electrical apparatus so that the temperature and atmospheric pressure of the operating transformer or other electrical apparatus is maintained within its operating limits.

3. A process as recited in claim 2 wherein: said cooling is accomplished by: a) Conducting the vapor of said dielectricfluid generated by the heat ofthe operating transformer or other electrical apparatus from the transformer or other electrical apparatus to a condensing means in the path thereof; b) Condensing said dielectric fluid vapor generated by the heat of the operating transformer or other electrical apparatus to liquid phase so that the latent heat of said dielectric fluid is removed; c) Recirculating said dielectric fluid condensed by said condensing means back to the transformer or other electrical apparatus so that the transformer or other electrical apparatus is maintained atatemperature approximately equal to the boiling point of said dielectricfluid.

4. A process as recited in claim 1 wherein: said cooling is accomplished by circulating said dielectricfluid from the transformerthrough a mechanical heat exchanger means and back to the transformer so that the temperature within the transformer may be maintained at the desired level.

5. A process as recited in claim 1 or 3, wherein said dielectric fluid is trichlorotrifluoroethane.

6. A process as recited in claim 1 or 2 wherein: said dielectric fluid is perchloroethylene.

7. A process as recited in claim 3, further com- prising: draining polychlorinated biphenylsfrom said distilling means into a wate receptacle.

8. A process as recited in claim 1 or 2 wherein: said dielectric fluid has a boiling point lowerthan the boiling point of polychlorinated biphenyls so that said dielectric fluid may be separated from the polychlorinated biphenyls by distillation.

9. A process as recited in claim 1 or 2 wherein: said cleansing is accomplished by distilling said solution causing vaporization of said dielectricfluid while PCB's remain in liquid phase; and condensing said dielectric fluid vapor generated said distilling.

10. The internals of an electrical apparatus which have been decontaminated of polychlorinated biphenyls to less than 50 ppm by the process of claim 1 or2.

11. An apparatus for removing contaminants such as polychlorinated biphenyls from transformers and from the dielectric fluid contained therein comprising: a) A conduitfortransmitting polychlorinated biphenyl contamined dielectric fluid to a distillation means; b) A distillation means for receiving a polychlorinated biphenyl contaminated dielectric fluid via said conduit, for distilling the polychlorinated biphenyl contaminated dielectric fluid via said conduit, for distilling the polychlorinated biphenyl con taminated dielectricfluid to thereby produce a residual quantity of polychlorinated biphenyl contaminants in liquid phase; c) A condenser means in fluid communication with said distillation means adapted to condense the vapor generated by said distillation meansto a liquid phase;; d) Meansfortransmitting the purified dielectric fluid produced by said distillation and condensation means back to the transformer while separatelycol- lecting the polychlorinated biphenyl contaminants.

12. The apparatus recited in claim 7, wherein there is included a dielectricfluid characterized by a concentration of polychlorinated biphenylstherein contained within the transformer.

13. An apparatus as recited in claim 8, wherein: said dielectricfluid has a boiling point lowerthan the boiling point of polychlorinated biphenyls and in which polychlorinated biphenyls are soluble.

14. The apparatus as recited in claim 9, wherein the dielectric fluid istrichlorotrifluoroethane.

15. The apparatus as recited in claim 7, further comprising: meansforcooling thetransformertodissipatethe heat generated by the operating transformerso that said apparatus may be used while the transformer is in operation.

16. A process for removing polychlorinated biphenyls and other contaminants from non-operating transformers and other electrical apparatus, and wherein the steps for so removing PCB's from nonoperating electrical apparatus are: introducing to the apparatus a liquid solvent having a boiling point lowerthanthatofpolychlorinated biphenyls and in which the polychlorinated biphenyls are soluble so as to be dissolved within said solvent; removing the liquid solvent from the electrical apparatus and cleansing the polychlorinated biphenylstherefrom; and recirculating the cleansed liquid solvent backto the electrical apparatus for reuse therein.

17. Aprocessforremoving polychlorinatedbiphenyls and other contaminants from operating transformers and other electrical apparatus, and wherein the stepsfor so removing PCB's from operating electrical apparatus are; introducing to the apparatus a liquid solvent having a boiling point lower than that of polychlorinated biphenyls and in which the polychlorinated biphenyls are soluble so as to be dissolved within said solvent, said solvent having sufficient dielectric properties to serve as the dielectric fluid; removing said liquid solvent from the electrical apparatus and cleansing the polychlorinated biphenylstherefrom; and recirculating said cleansed liquid solvent backtot he electrical apparatus for reuse therein.

18. A process for removing polychlorinated bi phenylsfrom both an operating and non-operating electrical apparatus as claimed in Claim 1,substanti- ally as hereinbefore described.

19. An apparatus for removing contaminants such as polychlorinated biphenyls from transformers as claimed in Claim 11, substantially as described herein with reference to and as illustrated by any one of the examples shown in the accompanying drawings.