EP0144216B1 - Verfahren zum Entfernen polychlorierter Biphenyle mittels Lösungsmittelextraktion - Google Patents

Verfahren zum Entfernen polychlorierter Biphenyle mittels Lösungsmittelextraktion Download PDF

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Publication number
EP0144216B1
EP0144216B1 EP84308299A EP84308299A EP0144216B1 EP 0144216 B1 EP0144216 B1 EP 0144216B1 EP 84308299 A EP84308299 A EP 84308299A EP 84308299 A EP84308299 A EP 84308299A EP 0144216 B1 EP0144216 B1 EP 0144216B1
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European Patent Office
Prior art keywords
pcb
solvent
oil
extraction
phase
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Expired
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EP84308299A
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English (en)
French (fr)
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EP0144216A1 (de
Inventor
Peter F Way
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Electric Power Research Institute Inc
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Electric Power Research Institute Inc
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Priority to AT84308299T priority Critical patent/ATE32463T1/de
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    • 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
    • C10G21/28—Recovery of used solvent
    • 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
    • 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

  • the present invention is directed to a method for continuously removing polychlorinated biphenyl (PCB) compounds from oil contaminated therewith, comprising the steps of: in an extraction zone, continuously extracting PCB compounds from contaminated oil with a PCB selective solvent separating the solvent and the extracted PCB compounds, and returning the separated solvent to the extraction zone.
  • PCB polychlorinated biphenyl
  • PCB polychlorinated biphenyls
  • PCB PCB
  • oil used as heat transfer fluids in transformers, capacitors, and other electrical devices.
  • various chemical and physical methods have been developed to treat PCB contaminated oils, it has been found that it is difficult to develop a process which will be effective in meeting the increasingly stringent Government regulations pertaining to PCB concentration, yet will be economically feasible for industrial use.
  • Another difficulty encountered in removing contaminants from oils by conventional solvent extraction is the limitation imposed by the high boiling point of such oils and the degradation that occurs when they are processed at elevated temperatures, generally over about 150°C.
  • the solvent is separated from the oil fraction in the extract by distillation.
  • the oil fraction being the less volatile material becomes the bottom residue in the distillation column.
  • the energy requirements of the distillation are supplied by vaporizing a portion of the bottom residue, and thus if solvent removal from the oil fraction is essentially complete, as is conventionally the case, the temperature- pressure relationship is fixed solely by the volatility of the contaminant/oil fraction. The result may be either excessively high temperatures if moderate vacuum conditions are used, or extremely low vacuum if acceptable temperatures are used.
  • the present invention provides a method for removing PCB from PCB-contaminated oil without the complexity, expense, and oil loss characterizing known methods.
  • a method of the type defined initially hereinbefore is characterised in that the extraction zone is a multiple stage extraction zone having a stripping section and an enriching section, and
  • PCB compounds are continuously extracted from contaminated oil with a PCB-selective solvent in a countercurrent, multistage extractor comprising two sections: 1) a stripping section in which the contaminated oil feed is extracted, and 2) an enriching section in which the extract reflux recycled from the solvent separation step is extracted.
  • a stream of contaminated oil is continuously fed into the extractor where it enters the first stage of the stripping section.
  • the PCB-selective solvent enters the last stage of the stripping section of the extractor, passes countercurrently to the contaminated oil from stage to stage, exits from the first stage of the stripping section, and flows to the last stage of the enriching section.
  • the recycled extract reflux enters the first stage of the enriching section, and the solvent phase from the stripping section passes countercurrently to the extract reflux from stage to stage, and exits the extractor from the first stage of the enriching section as a PCB-enriched extract.
  • the extract reflux exits the last stage of the enriching section, partially stripped of its PCB content, and joins the contaminated oil feed to enter the first stage of the stripping section.
  • the combined oil stream, from which the PCB compounds have been extracted by the solvent exits the last stage of the stripping section as the purified oil product.
  • the extract leaving the extractor is partially distilled in a distillation column and the bottom residue therefrom is cooled and then separated into a solvent phase, which is returned to the distillation column, and an oil/PCB phase.
  • the major portion of the oil/PCB phase is continuously recycled back to the extractor as the extract reflux, and is extracted in the enriching section as described above.
  • the minor portion of the oil/PCB phase from the solvent separating step is withdrawn as the disposable PCB residue.
  • the solvent chosen should be highly selective for PCB while at the same time having a low solubility for the oil and other constituents in the oil.
  • the solvent itself should have a low solubility in oil.
  • the solvent should have a volatility in a range that allows separation from a PCB/oil phase by distillation and a specific gravity sufficiently different from that of the oil to permit phase separation in the extraction stages.
  • the solvent should have a reasonable viscosity and surface tension, as well as a low level of toxicity.
  • Suitable solvents for the extraction method of the present invention include those selected from the following solvent classes:-atkyt substituted formamides and acetamides, pyrrolidones, sulfoxides, glycols, glycol ethers, aldehydes, and alcohols.
  • Preferred solvents from these classes include N-methyl pyrrolidone, dimethyl sulfoxide, diethylene glycol monomethyl ether, commonly known as methyl Carbitol, and furfural.
  • the most preferred solvent is diethylene glycol monomethyl ether.
  • a solvent may still possess a measurable solubility for the desirable oil constituents and thus in a conventional solvent extraction process, the oil loss could become excessive. For instance, if the solubility of oil in the solvent is about 10 percent and the solvent/oil ratio is about 1, the extract leaving a conventional extraction process would be carrying away about 10 percent of the oil feed. After distillation and separation of the solvent, the 10 percent of the original oil becomes the residue stream containing the extracted PCB. Thus, not only is 10 percent of the oil lost, but the PCB concentration has only been increased in the residue by a factor of 10. When the solvent/oil ratio is increased to achieve a higher PCB removal efficiency, the situation becomes worse. For instance, if the solvent/oil ratio is increased to 2, then the oil loss would increase to about 20 percent. In addition to the value of the lost oil, the overall operating cost is increased substantially by the increased cost of disposal for this large PCB residue stream.
  • the oil loss due to solubility of the oil in the solvent is effectively eliminated by recycling a major portion of the oil/PCB phase from the solvent separation step back to the extractor, as an extract reflux.
  • the oil carried out with the extract is returned to the enriching section of the extractor, and ultimately to the main oil stream entering the stripping section of the extractor and exiting as the purified oil product.
  • the PCB in the recycled portion is transferred to the outflowing extract, thereby markedly increasing its PCB concentration.
  • increasing the solvent/oil ratio does not increase the oil loss or reduce the PCB concentration in the residue, as would be the case in a conventional solvent extraction process.
  • the solvent separation from the extract is carried out in two steps. First, there is a partial separation by distillation and then, a final purification by phase separation made possible by lowering the temperature of the bottom residue from the distillation step.
  • the partial separation by distillation is accomplished by maintaining sufficient solvent in the bottom residue to permit operating the column under economical vacuum conditions and acceptable temperatures. In order to achieve such conditions, there should be about 20 to 80 percent solvent in the bottom residue.
  • the distillate product from this step comprising PCB-free solvent is recycled back to the extractor.
  • the bottom residue is cooled to a temperature below the limits of mutual solubility to form a PCB/oil phase and a solvent phase.
  • the two phases are separated by decanting, and the solvent phase is returned to the distillation column.
  • the PCB/oil phase for the most part, is recycled back to the extractor as extract reflux.
  • a small portion of the PCB/oil phase is withdrawn as the final PCB residue.
  • a stream of oil contaminated with PCB is introduced into the extractor 6 at a controlled rate through lines 1, 3 and 5, using pump 2 and heater 4 to raise the temperature of the oil to between about 20 and 65°C.
  • the oil stream enters extractor 6 at an intermediate feed point.
  • the extractor consists of two sections, a stripping section 51 and an enriching section 52. In the stripping section, the oil contacts the solvent in a process of countercurrent mixing and coalescing whereby the PCB compounds are continuously extracted from the oil in multiple stages and the purified oil exits the extractor 6 through line 7.
  • the purified oil product is suitable for reuse as a dielectric fluid.
  • the number of theoretical stages in the stripping section required to achieve a PCB removal efficiency in the range of 90 to 98 percent is 3 to 10, preferably 6, when employing a solvent/oil ratio in the range of about 1:1 to 4:1.
  • the desired solvent/oil ratio is determined by the type of PCB compound being extracted and the PCB concentration in the contaminated oil.
  • the solvent phase flows from the-first stage of the stripping section 51 through the enriching section 52 in countercurrent flow with the recycled extract reflux entering by line 43, and leaves the extractor 6 through line 8 and control valve 9, flowing through line 10 as the extract feed to the distillation column 11.
  • Distillation is carried out in the range of 50 to 150 torr (6.7 to 20 kPa), preferably about 100 torr (13.3 kPa).
  • the vapor flow rate through the distillation column 11 is maintained by adjusting the heat input to reboiler 27.
  • Purified solvent vapor exiting the top of the distillation column by line 12 is condensed in condenser 13 and flows to separator 15 through line 14.
  • Noncondensable gases are removed through line 16 by means of a vacuum pump 17.
  • a portion of the condensed solvent is returned to the distillation column as reflux by line 18, while the other solvent portion flows through line 19 to tank 20, and is recycled as PCB-free solvent back to the extractor 6 by line 21, pump 22, line 23, flow controller 24, and line 25.
  • the bottom residue from the distillation column 11 exits the column by line 29 and is pumped by pump 30 through line 31 to cooler 32.
  • cooler 32 the bottom residue is cooled to a temperature in the range of about 25-50°C and a PCB/oil phase and solvent phase are formed.
  • the two phases flow through line 33 to decanter 34 where they are separated.
  • the solvent phase is returned to the distillation column 11 by lines 44 and 46, and pump 45.
  • the PCB/oil phase which is removed from the decanter by lines 35 and 37, and pump 36, is divided into a major portion, the extract reflux, and a minor portion, the disposable PCB residue.
  • the residue portion exits the process through lines 38 and 40, and control valve 39.
  • the larger reflux portion is continuously recycled to the extractor 6 by lines 41 and 43, and flow control valve 42, and enters the enriching section 52 of the extractor 6.
  • the extract reflux is contacted with the solvent phase flowing from the first stage of the stripping section 51 in a similar process of countercurrent mixing and coalescing stages to increase the PCB content of the extract.
  • the number of theoretical stages in this section is in the range of 1 to 6, preferably 3, depending upon the desired concentration of PCB in the final residue exiting the process. Leaving the enriching section by line 8 and control valve 9, the extract flows by line 10 to the distillation column 11 where it is distilled, then separated and recycled as described above.
  • an agitated baffled extraction column with a diameter of 150 mm, an extraction section height of about 1000 mm, and an enriching section height of about 500 mm, operating at 38°C with a transformer oil feed rate of 25 liters/hour, an extractor reflux rate of 1.6 liters/hour, and using diethylene glycol monomethyl ether as the solvent at a rate of 59 liters/hour
  • the PCB a blend of polychlorinated biphenyls with a chlorine content of 54 weight percent, commonly known as Aroclor 1254
  • content of 389 ppm in the transformer oil was reduced to 8 ppm in the purified oil exiting the extractor.
  • the distillation column with a diameter of 150 mm and a packed height of about 1800 mm which was operated in conjunction with the extraction column in a continuous process, effected a separation of the solvent from the extract stream to a solvent purity of less than 1 ppm PCB.
  • the residue produced by cooling the distillation column bottom product and separating the PCB/oil phase from the solvent phase was accumulated at a rate of 0.56 liters/hour and had a PCB concentration of 1.7 percent.
  • the PCB a blend of polychlorinated byphenyls with a chlorine content of 60 weight percent, commonly known as Aroclor 1260
  • the PCB content of the solvent from the distillation column was less than 1 ppm.
  • the residue product accumulated at a rate of 0.15 liters/hour and had a PCB content of 4.6 percent.

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  • Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Extraction Or Liquid Replacement (AREA)

Claims (11)

1. Verfahren zum kontinuierlichen Entfernen von polychlorierten Biphenyl-(PCB)-Verbindungen aus von damit verunreinigtem Öl, das die folgenden Schritte umfaßt:
Kontinuierliches Extrahieren in einer Extraktionszone (6) von PCB-Verbindungen aus verunreinigtem Öl mit einem PCB-selektiven Lösungsmittel, Trennen von Lösungsmittel und extrahierten PCB-Verbindungen, und Rückführen des abgetrennten Lösungsmittels zur Extraktionszone (6), dadurch gekennzeichnet, daß die Extraktionszone eine Mehrstufen-Extraktionszone (6) ist, die einen Abziehbereich (51) und einen Anreicherungsbereich (52) aufweist, und
a) im Abziehbereich (51) PCB-Verbindungen kontinuierlich aus verunreinigtem Öl mit einem PCB-selektiven Lösungsmittel extrahiert werden,
b) der Extrakt (10) aus der Extraktionszone (6) in einer Destillationszone (11) teilweise destilliert wird,
c) der Sumpfrückstand von Schritt b) gekühlt (32) wird, und die resultierenden Phasen in eine Lösungsmittelphase (44) und eine ÖI/PCB-Phase (35) getrennt (34) werden,
d) ein Großteil (43) der Öl/PCB-Phase von Schritt c) kontinuierlich als Extractrückfluß zum Anreicherungsbereich (52) der Extraktionszone (6) von Schritt a) zurückgeführt wird, worin PCB-Verbindungen vom rückgeführten Teil durch die Lösungsmittelphase extrahiert werden, die den Abziehbereich (51) der Extraktionszone (6) in Schritt a) verläßt, um den PCB-Gehalt des Extrakts zu erhöhen, und
e) eine geringer Teil (40) der ÖI/PCB-Phase von Schritt c) als verwerfbarer PCB-Rückstand entfernt wird.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß das destillierte Lösungsmittel, das im Schritt b) erzeugt wurde, zur Verwendung im kontinuierlichen Extraktionsschritt a) rückgeführt (23) wird.
3. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß das Lösungsmittel aus einer Gruppe bestehend aus Alkyl-substituierten Formamiden und Acetamiden, Pyrrolidonen, Sulfoxiden, Glykolen, Glykoläthern, Aldehyden und Alkoholen ausgewählt ist.
4. Verfahren nach Anspruch 3, dadurch gekennzeichnet, daß das Lösungsmittel ausgewählt ist aus der Gruppe bestehend aus N-Methylpyrrolidon, Dimethylsulfoxid, Diethylenglykolmonomethyläther und Furfural.
5. Verfahren nach Anspruch 4, dadurch gekennzeichnet, daß das Lösungsmittel Diethylenglykolmonomethyläther ist.
6. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß im Extraktionsschritt a) 90 bis 98 Prozent der PCB-Verbindungen in drei bis zehn theoretischen Extraktionsstufen vom verunreinigten Öl entfernt werden, und daß das Lösungsmittel/Öl-Beschickungsverhältnis im Bereich von 1:1 bis 4:1 liegt.
7. Verfahren nach Anspruch 6, dadurch gekennzeichnet, daß der Extraktionsschritt a) in etwa sechs theoretischen Extraktionsstufen durchgeführt wird.
8. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß der Extraktionsschritt d) in einer bis sechs theoretischen Extraktionsstufen durchgeführt wird.
9. Verfahren nach Anspruch 7, dadurch gekennzeichnet, daß der Extraktionsschritt d) in etwa drei theoretischen Extraktionsstufen durchgeführt wird.
10. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß der Sumpfrückstand von Schritt b) 20 bis 80 Prozent Lösungsmittel enthält.
11. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß der Druck im Bereich von 6,7 vis 20,0 kPa (50 bis 150 Torr) liegt, und daß die Temperatur ungefähr 150°C nicht übersteigt.
EP84308299A 1983-12-07 1984-11-29 Verfahren zum Entfernen polychlorierter Biphenyle mittels Lösungsmittelextraktion Expired EP0144216B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT84308299T ATE32463T1 (de) 1983-12-07 1984-11-29 Verfahren zum entfernen polychlorierter biphenyle mittels loesungsmittelextraktion.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US55919183A 1983-12-07 1983-12-07
US559191 1983-12-07

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EP0144216A1 EP0144216A1 (de) 1985-06-12
EP0144216B1 true EP0144216B1 (de) 1988-02-10

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EP (1) EP0144216B1 (de)
AT (1) ATE32463T1 (de)
CA (1) CA1265086A (de)
DE (1) DE3469301D1 (de)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2617066B1 (fr) * 1987-06-29 1989-10-20 Font Pierre Dispositif d'eclatement et de decontamination, en particulier de transformateur electrique
FR2626582B1 (fr) * 1988-02-03 1990-06-22 Sepulcre Patrick Procede de regeneration d'huiles minerales et de fluides dielectriques au silicone souilles par des polychlorobiphenyls et dispositif de decontamination
US5414203A (en) * 1991-03-28 1995-05-09 International Technology Corporation Treatment of particulate material contaminated with polyhalogenated aromatics
ES2142697B1 (es) * 1996-02-08 2000-12-01 Arratibel Jose Luis Zurutuza Procedimiento perfeccionado y equipo detoxificador de aceites contaminados con pcbs y pcts.
DE19852007C2 (de) * 1998-11-11 2002-06-13 Mineraloel Raffinerie Dollberg Verfahren zur Wiederaufarbeitung von Altölen

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4328092A (en) * 1980-03-07 1982-05-04 Texaco Inc. Solvent extraction of hydrocarbon oils
US4387018A (en) * 1982-03-17 1983-06-07 The United States Of America As Represented By The United States Department Of Energy Method of removing polychlorinated biphenyl from oil
US4405448A (en) * 1982-03-31 1983-09-20 Googin John M Process for removing halogenated aliphatic and aromatic compounds from petroleum products
US4477354A (en) * 1982-09-07 1984-10-16 Electric Power Research Institute Destruction of polychlorinated biphenyls during solvent distillation

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EP0144216A1 (de) 1985-06-12
CA1265086A (en) 1990-01-30
DE3469301D1 (en) 1988-03-17
ATE32463T1 (de) 1988-02-15

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