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EP0147860B1 - Procédé pour remplacer, dans les appareils d'induction électrique, les réfrigérants contenant du polychlorobiphényl (PCB) par des réfrigérants diélectriques totalement exempts de PCB - Google Patents

Procédé pour remplacer, dans les appareils d'induction électrique, les réfrigérants contenant du polychlorobiphényl (PCB) par des réfrigérants diélectriques totalement exempts de PCB Download PDF

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Publication number
EP0147860B1
EP0147860B1 EP84116402A EP84116402A EP0147860B1 EP 0147860 B1 EP0147860 B1 EP 0147860B1 EP 84116402 A EP84116402 A EP 84116402A EP 84116402 A EP84116402 A EP 84116402A EP 0147860 B1 EP0147860 B1 EP 0147860B1
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EP
European Patent Office
Prior art keywords
pcb
coolant
tank
cooling liquid
interim
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP84116402A
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German (de)
English (en)
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EP0147860A2 (fr
EP0147860A3 (en
Inventor
Gilbert Richard Atwood
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Union Carbide Corp
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Union Carbide Corp
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Priority to AT84116402T priority Critical patent/ATE25895T1/de
Publication of EP0147860A2 publication Critical patent/EP0147860A2/fr
Publication of EP0147860A3 publication Critical patent/EP0147860A3/en
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Publication of EP0147860B1 publication Critical patent/EP0147860B1/fr
Expired legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/08—Cooling; Ventilating
    • H01F27/10—Liquid cooling
    • H01F27/12—Oil cooling
    • H01F27/14—Expansion chambers; Oil conservators; Gas cushions; Arrangements for purifying, drying, or filling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
    • B08B3/04—Cleaning involving contact with liquid
    • B08B3/08—Cleaning involving contact with liquid the liquid having chemical or dissolving effect
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G21/00—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents
    • C10G21/006—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents of waste oils, e.g. PCB's containing oils

Definitions

  • This invention relates to electrical induction apparatus, e.g. electric power transformers, specifically to the dielectric liquid coolants contained therein and especially to those coolants consisting of or containing as a constituent, polychlorinated biphenyl, PCB. More particularly, the present invention relates to methods for converting PCB-containing electrical induction apparatus, e.g. transformers, into substantially PCB-free transformers in order to qualify said transformers as "non-PCB transformers" under U.S. government regulations.
  • PCB's Because of their fire resistance, chemical and thermal stability, and good dielectric properties, PCB's have been found to be excellent transformer coolants.
  • US-A-2,582,200 discloses the use of PCB's alone or in admixture with compatible viscosity modifiers, e.g., trichlorobenzene, and such trichlorobenzene-PCB mixtures have been termed generically "askarels". These askarels may also contain minor quantities of additives such as ethyl silicate, epoxy compounds and other materials used as scavengers for halogen decomposition products which may result from potential electric arcing.
  • ASTM D-2283-75 describes several types of askarels and delineates their physical and chemical specifications.
  • PCB's have been cited in the U.S. Toxic Substances Control Act of 1976 as an environmental and physiological hazard, and because of their high chemical stability they are non- biodegradable. Hence, they will persist in the en- vironmentand are even subject to biological magnification (accumulation in higher orders of life through the food chain). Accordingly, in the U.S., transformers are no longer made with PCB or askarel fluids. While older units containing PCB may still be used under some circumstances, it is necessary to provide special precautions such as containment dikes and maintain regular inspections.
  • Transformers containing PCB's are at a fur- therdisadvantage since maintenance requiring the core to be detanked is prohibited, and the transformer owner remains responsible for all environmental contamination, including clean-up costs, due to leakage, tank rupture, or other spillage of PCB's, or due to toxic by-product emissions resulting from fires.
  • To replace a PCB-containing transformer it is necessary to (1 ) removethetrans- former from service, (2) drain the PCB and flush the unit in a prescribed manner, (3) remove the unit and replace with a new transformer, and (4) transport the old transformer to an approved landfill for burial (or to a solid waste incinerator).
  • a desired approach to the problem would be to replace the PCB oil with an innocuous, compatible fluid.
  • a number of fluid types have been used in new transformers as reported in Robert A. Westin, "Assessment of the Use of Selected Replacement Fluids for PCB's in Electrical Equipment", EPA, NTIS, PB-296377, March 1,1979; J. Reason and W. Bloomquist, "PCB Replacements: Where the Transformer Industry Stands Now", Power, October, 1979, p. 64-65; Harry R. Sheppard, "PCB Replacement in Transformers", Proc. of the Am. Power Conf., 1977, pp. 1062-68; Chem. Week, 130, 3, 24 (1/20/82); A. Kaufman, Chem.
  • silicone oils e.g., polydimethylsiloxaneoils, modified hydrocarbons (for high flash points, e.g. RTEmp, a proprietary fluid of RTE Corp.), synthetic hydrocarbons (poly-alpha-olefins), high viscosity esters (e.g. dioctyl phthalate and PAO-13-C, a proprietary fluid of Uniroyal Corp.), and phosphate esters.
  • halogenated alkyl and aryl compounds have been used.
  • liquid trichloro- and tetrachlorobenzenes and toluenes and proprietary mixtures thereof e.g. liquid mixtures of tetrachlorodiarylmethane with trichlorotoluene isomers.
  • Liquid mixtures of the trichloro- and tetrachlorobenzene isomers are particularly suitable because of their low flammabilities (e.g., high fire points) and similar physical and chemical properties to askarels being removed.
  • Other proposed fluids are tetrachloroethylene (e.g. Diamond Shamrock's Perclene TG) and polyols and other esters.
  • silicone oils have been the most widely accepted. Their chemical, physical, and electrical properties are excellent. They have high fire points (>300°C), and no known toxic or environmental problems. These oils are trimethylsilyl end-blocked poly(dimethyl- siloxanes) : wherein n is of a value sufficient to provide the desired viscosity, e.g., viscosity at 25° C of about 50 centistokes. Commercial silicone oils suitable for use are available from Union Carbide (L-305), and others.
  • the U.S. government regulations have designated those fluids with greater than 500 ppm PCB as "PCB transformers", those with 50-500 ppm PCB as “PCB contaminated transformers”, and those with less than 50 ppm PCB as “non-PCB transformers". While major expenses may be entailed with the first two classifications in the event of a spill or the necessity of disposal, the last category is free of U.S. government regulation. To achieve the last classification, the PCB concentration must remain below 50 ppm for at least 90 days, with the transformer in service and sufficiently energized that temperatures of 50° C or higher are realized. This requires a 90-day averaged rate of elution of about 0.56 ppm/day. It is anticipated that most, if not all, states of the U.S. will adopt regulations which may be the same as, or stricter, than U.S. government regulations. More lenient regulations may be possible elsewhere.
  • the transformer When the initial clean-out procedure is complete, the transformer is filled with silicone fluid. As effective as these elaborate flushing procedures might have been expected to be, they cannot remove PCB adsorbed into the interstices of the cellulosic material. Consequently, the PCB content of the silicone coolant gradually rises as the residual PCB leaches out while the transformer is in use. Therefore, if one wishes to reach a PCB-free state ("non-PCB" as defined by U.S. government regulation), it is necessary to either periodically change-out, or continually clean up, the silicone fluid until a leach rate of less than 50 ppm for 90 days is reached.
  • a PCB-free state as defined by U.S. government regulation
  • the present invention is based on the fact that there are suitable cooling fluids which are more suitable than silicone oil for operation over a limited time while leach is being accomplished. They are reasonably volatile for distillation from PCB, readily miscible therewith, and of relatively low viscosity for rapid diffusion into the pores of the insulation.
  • the other constituents of askarel, i.e. trichlorobenzene and tetrachlorobenzene, are found to be ideal fluids for this purpose. They can be used as temporary or interim, leaching, cooling fluids where fire may be a potential hazard, while light hydrocarbons could be used if fire is not a hazard.
  • the present invention is based upon the use of a suitable temporary or interim cooling liquid as a substitute for PCB-containing coolants in electrical induction apparatus, e.g. transformers, having a vessel (e.g. tank) containing the coolant and an electrical winding and porous solid cellulosic electrical insulation immersed in and impregnated with PCB while electrically operating the transformer for a sufficient period of time to elute the PCB from the solid electrical insulation contained in the transformer.
  • the interim dielectric cooling liquid is changed to speed up the elution process, the preferred goal being to elute so much of the leachable PCB that the transformer can be operated for 90 days and not exceed 50 ppm PCB content in the permanent coolant intended for the transformer.
  • the interim dielectric cooling liquid is removed from the tank and the tank is then filled with a PCB-free permanent dielectric cooling liquid compatible with the transformer.
  • a PCB-containing fluid in a transformer is replaced with a permanent PCB-free liquid coolant:
  • flushing step While efficient draining and flushing techniques should be used, these do not in themselves constitute the invention, but are a part of all heretofore known retrofill procedures. They are a prelude to the most efficient embodiment of the invention itself, but their value heretofore has been overrated, in that it is the slow leach rate, not the efficiency of flush which has been found to limit the rate of PCB removal.
  • solvents may be used in the flushing step, including hydrocarbons such as gasoline, kerosene, mineral oil or mineral spirits, toluene, turpentine, or xylene, a wide range of chlorinated aliphatic or aromatic hydrocarbons, alcohols, esters, ketones, and so forth.
  • Fluids other than normally liquid trichlorobenzene, TCB, or a mixture thereof with tetrachlorobenzene can be used.
  • the preferred interim fluid has the following characteristics: (a) it is compatible with PCB (i.e. preferably dissolving at least 50% of its weight of PCB, more preferably, at least 90% of its weight of PCB and, most preferably, being miscible in all proportions with PCB); (b) it is of low enough molecular weight to have good molecular mobility to be able to enter the pores or interstices of the solid insulating material and it promotes rapid mutual diffusion, preferably, having a viscosity at 25° C of 10 mm 2 /s or less and, more preferably, 3 mm 2 /s or less; (c) it can be easily separated, e.g.
  • TCB tetrachlorobenzene
  • PCB preferably, having a boiling point of 275° C or less and, more preferably, 260° C or less, from PCB; (d) it is presently considered environmental innocuous; and (e) it is compatible with typical transformer internals.
  • TCB or mixtures with tetrachlorobenzene, is preferred, a number of alternatives, as above- mentioned can be used. These would include modified and synthetic hydrocarbons, and a variety of halogenated aromatic and aliphatic compounds. There are also a variety of liquid trichlorobenzene isomer mixtures. The preferred TCB fluid would be a mixture of these isomers with or without tetrachlorobenzene isomers.
  • the advantage lies in the fact that such a mixture has a lower freezing point than do the individual isomers, thus reducing the chance of it solidifying within the transformers in very cold climates. Further, the mixtures are often the normal result of manufacture and hence can cost less than the separated and purified individual isomers.
  • the preferred embodiment involves operating the transformer to obtain the fastest possible diffusion rates as specified in step (3) above.
  • a transformer should automatically provide enough heat for this purpose.
  • sufficiently elevated temperatures e.g. at least 50° C
  • this thermal control represents a preferred embodiment of this invention, it is optional and not an essential requirement, there being many transformers for which such lagging or heating may be impractical. Leaching at lower temperatures, even ambient, is workable but will take longer.
  • Fluid circulation as specified in step (3) is optional but is an advantageous embodiment in that such circulation will prevent the buid-up of concentration gradients which can act to retard diffusion. Since elution is a slow process, the circulation rate need not be very rapid. Violent circulation, of course, is to be avoided in order to avoid damage to the internal structure of the transformer. It is recognized that many transformers may not, by their construction or placement, be readily modified to utilize a circulation loop, and such circulation is not considered a necessary aspect, but only one embodiment of this invention to increase elution rates. In most transformers, natural thermal gradients alone will induce sufficient circulation especially in those cases where a relatively low viscosity, mobile coolant, such as TCB, is used.
  • mobile coolant such as TCB
  • coolant changes are made after selected periods of electrical operation, until the coolant fails to elute 50 ppm of PCB per 90 days operation.
  • Periods of electrical operation between coolant changes can be selected to be 20 days to 1 year (or more, if the transformer owner's needs prevent shutting down the transformer except at rare specified times, e.g., special holiday periods, such that there may be more than one year between shutdowns and possibly shutdowns can take place only every other year), preferably 30 to 120 days and most preferably 45 to 90 days.
  • the contaminated leach fluid may then be distilled off and condensed for re-use to leave a PCB bottom product which is incinerated or otherwise disposed of pursuant to U.S. government regulations. While a complete change of interim coolant is preferred, it is possible that the inconvenience of additional shutdowns predicates a different procedure, i.e., that of simultaneously introducing new fresh fluid and removing the old contaminated fluid while the transformer remains in operation. It is less efficient because the fresh fluid mixes with the old in the transformer, and fluid of reduced PCB concentration is actually removed. Thus to eliminate all the PCB, more leach fluid will have to be removed than for the preferred procedure. This penalty can be reduced if one takes pains to avoid excessive mixing.
  • new chilled TCB or other interim dielectric cooling fluid can be introduced into the bottom of the transformer, while old, warm, PCB-laden interim dielectric cooling fluid is removed from the top.
  • the density difference will retard mixing.
  • the process will require repetition until the desired PCB level, e.g., less than 50 ppm in silicone oil coolant can be maintained for at least 90 days.
  • PCB can be removed from the PCB-laden silicone oil that may result from step (7) by contacting it (e.g. on-site while step (7) is being carried out or off-site after PCB-laden silicone oil has been removed) with activated charcoal, zeolites or other adsorbants capable of adsorbing the PCB from the silicone oil. Any other method for removing PCB from the spent silicone oil can be employed.
  • the chlorinated portion of the coolant can be replaced and the old batch sent to a still for easy purification. Two orthreesuch changes over a period of several months will give a substantially halogen free system, if one is desired.
  • Suitable coolants of a permanent nature that can be used in place of the final fill of silicone oil include dioctylphthalate, modified hydrocarbon oils, e.g. RTEmp of RTE Corp., polyalphaolefins, e.g. PAO-13-C of Uniroyal, synthetic ester fluids, and any other compatible permanent fluid. It is also preferred that the permanent dielectric fluid be characterized by a high boiling point compared to said interim dielectric solvent so that the interim dielectric solvent can be separated from the permanent fluid if the need arises and also to avoid releasing permanent fluid due to volatilization in the event the transformer tank is ruptured.
  • the trichlorobenzene isomers, the tetrachlorobenzene isomers, and mixtures thereof have high flammability ratings and other physical propertiessim- ilar to askarel and therefore are preferred amongst the less preferred permanent fluids.
  • a “cycle” is the period of time between changes in the coolant.
  • a “part” of a cycle is a portion of a cycle where the leach rate into the coolant is markedly different from the rate in the earlier or later portion of the cycle.
  • the coolant in the transformer prior to draining and rinsing was mineral oil (Exxon Univolt inhibited oil, transformer grade) containing the initial PCB concentration shown in Table I.
  • Transformer #459 and #461 of Examples A and 1 at one time had been askarel-filled transformers that had been previously switched to mineral oil and respectively contained 9,150 and 7,800 ppm PCB.
  • Transformer #459 of Example A was drained, spray rinsed with mineral oil and then filled with fresh mineral oil.
  • Transformer #461 of Example was drained, spray rinsed with TCB mix and then filled with fresh TCB mix. The transformers were operated at about 80° C for the time periods listed in Table I. In Example 1, the transformer was drained of TCB mix and refilled with TCB mix 2 more times to provide two complete cycles and one ongoing cycle.
  • each respective transformer was a member of a bank of three identical Westinghouse transformers having a rated capacity of 333 KVA each. Each of these transformers contained about 719 I (190 gallons) of type A askarel that was a coolant having a 60/40 wt. ratio of Aroclor 1260 (PCB) and trichlorobenzene. These 3 transformers were all tied into the same three- phase bank and were all operated at the same capacity and otherwise encountered the same conditions except as hereinafter designated. The normal service of the transformers of Examples 2, B and C was far below their rating and the annual average operating temperature was around 40° C except as otherwise designated.
  • Transformer #669 (Example 2) and transformer #667 (Example C) were drained of askarel, spray rinsed twice with TCB mix and subsequently refilled with TCB mix.
  • Transformer #668 (Example B) was drained, spray rinsed twice with silicone oil (L-305) and subsequently refilled with silicone oil, L-305. All transformers were reenergized and liquid samples were taken periodically to check the PCB content.
  • Example 2 transformer #669 was operated for 96 days then drained, spray rinsed with TCB mix and refilled with TCB mix and operation was continued in Cycle 2 and the same sequence was repeated for Cycles 3 and 4 for the transformer.
  • Example 2 at the end of Cycle 4 in the case of transformer #669, the transformer was drained and spray rinsed with TCB mix and thereafter filled with TCB mix and it continued to be electrically operated.
  • the day intervals, PCB concentrations at the end of the day intervals and overall rate of elution and converted rate of elution in terms of ppm per day are given in Table I in respect to each cycle.
  • Example B transformer #668 was initially drained of askarel, spray rinsed twice with L-305 and filled with fresh L-305. At the end of the 390th day the transformer was again drained, spray rinsed with L-305 and subsequently filled with fresh L-305 and continued to operate in Cycle 2.
  • the day intervals, PCB concentration at the end of the day intervals, and the overall rates of elution in ppm per day are correspondingly listed in Table I.
  • Transformer #667 (Example C) was initially drained of askarel, spray rinsed twice with TCB mix and filled with TCB mix. At the end of the 96th day, it was drained, spray rinsed and filled with fresh TCB mix. Subsequent cycles are as indicated in Table I.
  • Example A transformer # 459, the leach rate had been reduced to an average PCB leach rate of 0.36 ppm/day in the second part of the first cycle. This was below the 0.55 ppm/day or 50 parts per million in 90 days required for reclassification as non-PCB. Accordingly, at day 220, the mineral oil was drained and replaced with the permanent L-305 silicone coolant. As can be seen from Table I the total PCB removed during Cycle 1 was equivalent to 475 ppm in the volume of coolant held by that transformer. This is less than the 1220 ppm removed during the same interval of time by TCB mix in #461, a similar size and type of transformer, and indicates that the mineral oil had not been as effective a leachant as TCB mix.
  • transformer #461 was leached with TCB mix.
  • the TCB solvent was drained and reintroduced into the same transformer.
  • the TCB mix was drained and replaced with fresh TCB mix.
  • the overall rate for Cycle 3 was 1.64 ppm per day, the rate decreased during the cycle and as of day 245 the PCB elution rate was reduced to 0.05 ppm per day which was well below the target rate of 0.55 ppm PCB per day. Accordingly, the fluid can at this point be replaced with a permanent silicone coolant.
  • Transformer #669 (Example 2) was originally filled with askarel. Hence, it had much more PCB in the insulation than #461 (Example 1) to be leached. Therefore, it required many more cycles and a considerably longer period of time to leach to an acceptable level. When the rate of leach falls below the target rate of 50 ppm in 90 days then the TCB mix can be replaced by silicone. The rate figures in the last column of Table I show a continual decrease with time, and the target rate should be reached around day 600. It should be pointed out that transformers #667, #668 and #669 were expected to be among the most difficult to leach. They are spiral wound transformers in which the paper insulation, and hence diffusional path length, can be several inches in depth. In contrast, many transformers are of the "pancake" design in which path lengths will be less than an inch.
  • Examples B and C, transformers #668 and #667, are comparative examples because in Example B the initial coolant used was silicone oil, and in Example C, the change over to silicone oil was made before the elution reached 0.55 ppm PCB per day.
  • Transformers #667 and #669 were filled initially with askarel which was replaced with TCB mix, while transformer #668 was filled initially with askarel which was replaced with L-305 silicone oil.
  • Figure 1 compares PCB analyses for the first cycle of these three transformers. The data have been converted to the total actual grams of PCB removed. While about 60,000 to 70,000 grams of PCB were quickly removed (within thefirst 28 days), subsequent removal was much slower, and the rates are indicated by the straight lines drawn through the points. It is presumed that the major quantity of PCB held up in the looser insulation is easily extracted regardless of solvent, but that it is the PCB held up in the tighter wound paper and pressboard insulation which is limiting to the process, and in this case the effectiveness of the eluants differs.
  • Figure 1 shows this difference. While the data points are somewhat scattered due to the difficulties of precise PCB analysis, it appears that the silicone takes 400 days to remove the same quantity which the TCB mix can remove in 60 days. A comparison of the slopes of the lines shows the TCB mix to be about 8.5 to 9.0 times as effective a leachant as L-305. The key point in this invention is that the ratio of effectiveness is so high. Thus, a process which might take 5 to 10 years with silicone alone could be carried out in a much shorter time with an interim coolant such as TCB mix.
  • FIG. 2 illustrates the effect of the transformer temperature on the rate of PCB elution.
  • 0667 and #669 were at about 40°C during the first cycle. They were changed out to fresh TCB mix after 96 days. Because winter was approaching and the transformers were not utilized to that capacity required to keep their temperatures high, it was anticipated that low temperatures might interfere with the leaching. Accordingly, 0 667 was artificially heated by applying heat to the cooling fins. Transformer #669 was left unheated for comparison. The temperature of #667 averaged about 55°C, while that of # 669 averaged about 23°C. Again, the data points are quite scattered, but it is clear that the warmer transformer eluted PCB faster than the colder one by a factor of 1.6. This factor may not be linear, and, consequently, the rate gain may not be as dramatic for higher temperatures. Further leaching was carried out at 85°C when possible, and thus most leaching listed in Table I was done at this higher temperature.
  • Example 3-5 By way of further example the following illustrative cases of Example 3-5 are presented. While they do not represent results from actual transformers, they are based upon the performance to be expected from the process of this invention under the conditions outlined below for each example as applied to transformers from which it is relatively easier to elute PCB by the process of this invention than those transformers used in Examples 1, 2, A, B and C.
  • Example 3-5 there is used a transformer of 757 (200 gallon) fluid volume capacity, the internals of which hold up to 6 gallons in the cellulosic materials, i.e., the paper insulating the coils, and which contains 757 I (200 gallons), more or less, of an askarel of 50% PCB (500,000 ppm), except for Example 4 wherein the transformer contains 757 I (200 gallons), more or less, of mineral oil containing 10,000 ppm PCB.
  • Figures 3 through 5 are plots of concentration of PCB in ppm in interim dielectric fluid (TCB) in the transformer plotted on a vertical logarithmic scale versus days elapsed (or soak time) and graphically illustrate the anticipated results sought to be obtained by this invention.
  • Example 3 the transformer is first deenergized. Then it is drained of its askarel, the latter being ultimately disposed of in an approved manner. The transformer is flushed out with a small quantity (e.g. 95 I (25 gallons) ) of trichlorobenzene, so as to reduce the residual askarel in the free fluid system to 0.5% of its initial value. The system is then logically inspected for leaky bushings or other physical problems which may require repair at this time.
  • a small quantity e.g. 95 I (25 gallons)
  • the transformer is filled with 200 gallons of trichlorobenzene, TCB (or, alternatively, a trichlorobenzene-tetrachlorobenzene mixture), is sealed up, and, after appropriate testing, is reenergized. Because the flush is not totally thorough, the initial PCB level in the newfluid in thetransformer is anticipated at 2500 ppm, i.e. 0.5% of the initial PCB levels. It is assumed that the PCB held up in the cellulosic materials leaches out at a rate varying from 0.001 to 0.01 % per day.
  • Fig. 3 shows the concentration (on a logarithmic scale) of PCB that can be expected to be found in the transformer fluid as a function of time. In actual commercial applications of the process one would not need to determine all these concentrations. However, one would want to sample the old fluid being replaced and determine its PCB concentration. This is shown by the open circles in Fig. 3. While the exact length of the leaching periods is arbitrary, experience with a given type of transformer will indicate the most practical period lengths in terms of overall process time and total number of fluid replacements. In this example, 60 day leach periods are used.
  • the transformer is once more deenergized, the fluid is drained, and a sample taken for analysis.
  • the system may be reflushed with about 95 1 (25 gallons) of TCB, and the flush fluid, along with the bulk fluid, is taken to a site where the TCB may be recovered by distillation (and the residual PCB properly disposed of by EPA approved methods).
  • the transformer is refilled with TCB, and this time the initial expected PCB concentration (due to residual prior fluid) is about 83 ppm. Again the anticipated PCB concentration follows along the second highest curve in Fig. 3 for the next 60 days (to 120 days), whereupon the TCB in the transformer is changed as before, with one exception. Since the drained TCB fluid has a concentration of PCB less than the initial value for the first fill, the drained fluid need not be sent to the still for separation, but instead can be used as the initial fill for a second PCB transformer to be converted to an non-PCB condition. This saves valuable distillation time and energy, as well as transportation or handling costs.
  • Table ll gives a list of the anticipated analytical results which are represented by the circles on the graph of Fig. 3. It is clear from the data of Table II and Fig. 3 thatthe fourth refill will not rise above 50 ppm PCB content, the U.S. government cut-off value for the designation of non-PCB transformers. Therefore, at the end of 180 days, the transformer is refilled with its permanent fluid, a silicone oil, e.g., L-305.
  • the PCB value expected to be reached after another 60 days (240 days) is only 16 ppm, and afterthe prescribed U.S. government 90 day period (270 days) it is anticipated to be at still only 18 ppm.
  • the transformer may be reclassified as a non-PCB transformer.
  • Example 4 60 day leach periods are used but flushing out of the transformers is eliminated. It is assumed that 98% of the fluid can be adequately drained, leaving 2% in the transformer. In this case the initial concentrations will be 2% of the previously drained fluids instead of the 0.5% of Example 3. The procedure of Example 3 is repeated in this example.
  • Example 4 The results to be expected for Example 4 are given in Table III and are shown in the graph of Fig. 4. Note that the objective is still obtained and the system can be refilled with silicone or other permanent oil at 180 days. The lack of highly efficient flushing is expected to lead to slightly higher PCB contents in the final fluid, but this does not substantially change the achievement of the goal of a non-PCB transformer.
  • Example 5 is identical to Example 4, except that30 day leach periods are used.
  • the expected analytical results are given in Table IV and the plots are shown in Fig. 5.
  • the trend is obvious from the graphs of Fig. 5.
  • the initial refill shows a reduction almost as good as that for Example 4, but subsequently the reductions start to curve off.
  • the sixth refill can be made with the permanent fluid, and sometime has been saved, about 30 days, at the expense of the two extra refills with TCB.
  • This example illustrates the availability of a trade-off of time vs. number of refills, and the choice depends upon which is valued the most highly for the specific case at hand.
  • the present invention is not limited to use in transformers but can be used in the case of any electrical induction apparatus using a dielectric coolant liquid including electromagnets, liquid cooled electric motors, and capacitors, e.g., ballasts employed in fluorescent lights.
  • a dielectric coolant liquid including electromagnets, liquid cooled electric motors, and capacitors, e.g., ballasts employed in fluorescent lights.

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  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
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  • Insulating Of Coils (AREA)
  • Processing Of Solid Wastes (AREA)

Claims (16)

1. Procédé pour remplacer un fluide de refroidissement contenant des PCB dans un appareil à induction électrique comportant une cuve contenant ledit fluide de refroidissement, un enroulement électrique et un isolant électrique cellulosique, solide, poreux immergé dans ledit fluide de refroidissement contenant des PCB, par un fluide de refroidissement permanent diélectrique, à haut point d'ébullition, pratiquement sans PCB, pour convertir ledit appareil électrique en un appareil dans lequel la vitesse d'élution des PCB dans ledit fluide de refroidissement est inférieure à la vitesse maximale admissible d'élution dans le fluide de refroidissement d'un appareil électrique classé comme non-PCB, ledit isolant électrique poreux solide étant imprégné dudit fluide de refroidissement contenant des PCB, ledit procédé comprenant les étapes qui consistent:
(a) à vider ladite cuve dudit fluide de refroidissement contenant des PCB afin de retirer de cette cuve une partie majeure dudit fluide de refroidissement contenant des PCB;
(b) à remplir ladite cuve d'un liquide de refroidissement diélectrique intermédiaire qui est miscible auxdits PCB, est d'une viscosité suffisamment basse pour circuler à l'intérieur de la cuve et pour pénétrer dans les interstices dudit isolant électrique, solide, poreux, et est capable d'être aisément séparé desdits PCB;
(c) à faire fonctionner électriquement ledit appareil à induction électrique et à poursuivre ledit fonctionnement électrique pendant une période suffisante pour, par élution, faire passer dudit isolant solide poreux dans ledit liquide de refroidissement diélectrique intermédiaire, les PCB contenus dans ledit fluide de refroidissement contenant des PCB, imprégné dans ledit isolant solide poreux;
(d) à vider ensuite de ladite cuve ledit liquide de refroidissement diélectrique intermédiaire contenant lesdits PCB élués;
(e) à répéter le cycle des étapes (b), (c) et (d) lorsque la vitesse d'élution des PCB dans ledit liquide de refroidissement diélectrique intermédiaire dépasse 0,50 ppm de PCB par jour sur la base du poids dudit fluide de refroidissement diélectrique permanent; et
(f) à remplir ladite cuve d'un fluide de refroidissement permanent, sensiblement sans PCB, choisi dans le groupe constitué d'huiles siliconées à haut point d'ébullition et haute viscosité, de fluides à base d'esters synthétiques, des huiles poly-alpha- oléfiniques et des huiles hydrocarbonées afin de reclasser dans un état non- PCB ledit appareil électrique.
2. Procédé selon la revendication 1, dans lequel le liquide de refroidissement diélectrique intermédiaire est du trichlorobenzène, du tétrachloroben- zène ou des mélanges de ceux-ci et le fluide de refroidissement permanent est un fluide diélectrique de refroissement à huiles siliconées.
3. Procédé selon la revendication 1 ou 2, dans lequel chaque étape (c) est prolongée pendant 20 jours à 1 an ou 30 à 120 jours ou 45 à 90 jours.
4. Procédé selon les revendications 1 à 3, dans lequel, lors de l'exécution de l'étape (d) du cycle précédent et de l'étape (b) du cycle immédiatement suivant, le liquide de refroidissement intermédiaire est vidé du sommet de la cuve tandis qu'un liquide de refroidissement diélectrique intermédiaire refroidi et frais est introduit dans le fond de la cuve et que le fonctionnement électrique de l'appareil se poursuit.
5. Procédé selon les revendications 1 à 4, dans lequel les étapes (d) et (f ) sont effectuées par l'introduction du fluide de refroidissement permanent, sans PCB, dans le fond de la cuve tandis que le liquide de refroidissement diélectrique intermédiaire présent dans la cuve est retiré du sommet de ladite cuve, et que le fonctionnement électrique de l'appareil se poursuit.
6. Procédé selon les revendications 1 à 5, dans lequel la cuve est équipée d'un isolant thermique afin d'élever la température du liquide de refroidissement diélectrique qu'elle contient durant chaque étape (c) pendant que ledit appareil à induction électrique fonctionne.
7. Procédé selon les revendications 1 à 6, dans lequel le liquide de refroidissement diélectrique intermédiaire présent dans la cuve est chauffé pendant l'étape (c) pendant que l'appareil à induction électrique fonctionne.
8. Procédé selon les revendications 1 à 6, dans lequel, durant l'étape (c), le liquide de refroidissement diélectrique intermédiaire est retiré de ladite cuve, chauffé et renvoyé à ladite cuve tandis que suffisamment de fluide diélectrique intermédiaire est maintenu dans ladite cuve et que ledit appareil à induction électrique fonctionne.
9. Procédé selon les revendications 1 à 8, dans lequel le liquide diélectrique intermédiaire est plus volatil que les PCB et est séparé des PCB contenus par distillation du liquide diélectrique de refroidissement intermédiaire.
10. Procédé selon les revendications 1 à 8, dans lequel le liquide de refroidissement diélectrique intermédiaire contenant des PCB élués à partir de l'isolant solide est retiré de la cuve sous forme d'un courant décalé tandis que l'appareil à induction électrique fonctionne et qu'un liquide de refroidissement diélectrique intermédiaire frais est ajouté en quantité sensiblement équivalente à celle du fluide diélectrique intermédiaire contenant des PCB retiré dans le courant décalé.
11. Procédé selon l'une des revendications 1 à 10, dans lequel la cuve est rincée avec un solvant pour les PCB après l'étape (a) et avant l'étape (b).
12. Procédé selon la revendication 11, dans lequel le solvant de rinçage est le même liquide que le liquide de refroidissement diélectrique intermédiaire utilisé à l'étape (b).
13. Procédé selon la revendication 11, dans lequel le solvant de rinçage et le liquide de refroidissement diélectrique intermédiaire sont du trichlorobenzène.
14. Procédé selon les revendications 1 à 12, dans lequel le liquide de refroidissement diélectrique intermédiaire est du 1,2,4-trichlorobenzène ou un mélange de trichlorobenzène et de tétra- chlorobenzène.
15. Procédé selon les revendications 1 à 14, dans lequel le fluide de refroidissement permanent utilisé pour remplir la cuve est une huile siliconée.
16. Procédé selon la revendication 15, dans lequel le fluide de refroidissement permanent utilisé à l'étape (f ) est une huile siliconée ayant la formule suivante:
Figure imgb0010
dans laquelle n est un nombre d'une valeur telle qu'une viscosité d'environ 50 mm2/s à 25° C est établie.
EP84116402A 1983-12-28 1984-12-27 Procédé pour remplacer, dans les appareils d'induction électrique, les réfrigérants contenant du polychlorobiphényl (PCB) par des réfrigérants diélectriques totalement exempts de PCB Expired EP0147860B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT84116402T ATE25895T1 (de) 1983-12-28 1984-12-27 Verfahren zum ersetzen von polychlorbiphenyl (pcb) enthaltenden kuehlfluessigkeiten in elektrischen induktionsapparaten durch pcb-freie dielektrische kuehlfluessigkeiten.

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US56630683A 1983-12-28 1983-12-28
US67527884A 1984-11-27 1984-11-27
US566306 1984-11-27
US675278 1984-11-27

Publications (3)

Publication Number Publication Date
EP0147860A2 EP0147860A2 (fr) 1985-07-10
EP0147860A3 EP0147860A3 (en) 1985-08-07
EP0147860B1 true EP0147860B1 (fr) 1987-03-11

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EP84116402A Expired EP0147860B1 (fr) 1983-12-28 1984-12-27 Procédé pour remplacer, dans les appareils d'induction électrique, les réfrigérants contenant du polychlorobiphényl (PCB) par des réfrigérants diélectriques totalement exempts de PCB

Country Status (20)

Country Link
EP (1) EP0147860B1 (fr)
JP (1) JPH0644534B2 (fr)
KR (1) KR900005687B1 (fr)
AR (1) AR244461A1 (fr)
AU (1) AU570294B2 (fr)
BR (1) BR8407245A (fr)
CA (1) CA1262606A (fr)
DE (1) DE3462640D1 (fr)
ES (1) ES8605653A1 (fr)
FI (1) FI78367C (fr)
GR (1) GR82586B (fr)
HK (1) HK56389A (fr)
IL (1) IL73971A (fr)
IN (1) IN163604B (fr)
MX (1) MX168456B (fr)
NZ (1) NZ210768A (fr)
PH (1) PH23329A (fr)
PT (1) PT79758A (fr)
SG (1) SG22889G (fr)
WO (1) WO1985002937A1 (fr)

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4790337A (en) * 1984-07-18 1988-12-13 Quadrex Hps Inc. Apparatus for removing PCB's from electrical apparatus
US4738780A (en) * 1984-11-27 1988-04-19 Union Carbide Corporation Method for replacing PCB-containing coolants in electrical induction apparatus with substantially PCB-free dielectric coolants
DE3540291C2 (de) * 1985-11-13 1994-11-24 Ensr Corp Verfahren zum Entfernen von Polychlorbiphenylen von elektrischen Vorrichtungen
US4879004A (en) * 1987-05-07 1989-11-07 Micafil Ag Process for the extraction of oil or polychlorinated biphenyl from electrical parts through the use of solvents and for distillation of the solvents
US4950837A (en) * 1989-07-18 1990-08-21 General Electric Company Method for reclassifying PCB transformers
US6380454B1 (en) 1991-03-15 2002-04-30 Luciano A. Gonzalez Destruction of polychlorinated biphenyls
JPH0555054A (ja) * 1991-08-26 1993-03-05 Mitsubishi Electric Corp 電気機器への媒体充填方法
FR2705140B1 (fr) * 1993-05-11 1995-07-28 Elf Antar France Procédé de remplacement du produit de lubrification pour la conversion des systèmes de réfrigération existant à des fluides frigorigènes sans action sur l'ozone atmosphérique.

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BR7703653A (pt) * 1976-06-08 1978-04-04 Rhone Poulenc Ind Novos liquidos dieletricos
US4124834A (en) * 1977-10-05 1978-11-07 Westinghouse Electric Corp. Electrical inductive apparatus
US4357175A (en) * 1980-04-10 1982-11-02 Stauffer Chemical Company Process for cleaning the interiors of vessels
US4299704A (en) * 1980-05-19 1981-11-10 General Electric Company Method for removing polychlorinated biphenyls from contaminated transformer dielectric liquid
US4379746A (en) * 1980-08-18 1983-04-12 Sun-Ohio, Inc. Method of destruction of polychlorinated biphenyls
US4396436A (en) * 1981-07-20 1983-08-02 Aluminum Company Of America Method and flushing for removing hydraulic fluid from hydraulic systems

Also Published As

Publication number Publication date
CA1262606A (fr) 1989-11-07
PH23329A (en) 1989-07-14
AU3783285A (en) 1985-07-12
FI853299A0 (fi) 1985-08-28
FI78367B (fi) 1989-03-31
AU570294B2 (en) 1988-03-10
KR900005687B1 (ko) 1990-08-06
EP0147860A2 (fr) 1985-07-10
IN163604B (fr) 1988-10-15
FI853299L (fi) 1985-08-28
JPH0644534B2 (ja) 1994-06-08
EP0147860A3 (en) 1985-08-07
PT79758A (en) 1985-01-01
FI78367C (fi) 1989-07-10
HK56389A (en) 1989-07-21
MX168456B (es) 1993-05-25
GR82586B (en) 1985-04-30
KR850700178A (ko) 1985-10-25
ES8605653A1 (es) 1986-03-16
BR8407245A (pt) 1985-11-26
ES539090A0 (es) 1986-03-16
IL73971A (en) 1988-12-30
DE3462640D1 (en) 1987-04-16
AR244461A1 (es) 1993-10-29
NZ210768A (en) 1988-07-28
SG22889G (en) 1990-07-06
JPS61500880A (ja) 1986-05-01
WO1985002937A1 (fr) 1985-07-04

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