US4764256A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Removal of polychlorinated biphenyls by solvent extraction
Assignee: Electric Power Research Institute
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Filing: 1987-12-16
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Granted: 1988-08-16
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Expires: 2007-12-16
Abstract
Abstract A method is provided for continuous removal of polychlorinated biphenyl compounds (PCB) from oil contaminated therewith, comprising the steps of continuously extracting PCB compounds from contaminated oil with a PCB-selective solvent in the stripping section of a multistage extraction zone, partially distilling the extract from the extraction zone in a distillation zone, cooling and separating the bottom residue into a solvent phase and an oil/PCB phase, continuously recycling a major portion of the oil/PCB phase as extract reflux to the enriching section of the extraction zone where PCB compounds are extracted from the recycled portion by the solvent phase produced in the stripping section of the extraction zone to increase the PCB content of the extract, and withdrawing a minor portion of the oil/PCB phase from the separation step as a disposable PCB residue.
Inventors
- 👤 Peter F. Way
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 09:34
CPC Classifications
C; C10; C10G; C10G21/00; C10G21/28; C10G21/006
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
229 words
A method for continuously removing polychlorinated biphenyl compounds from oil contaminated therewith, comprising the steps of: (a) in a multiple stage extraction zone having a stripping section and an enriching section, continuously extracting polychlorinated biphenyl compounds from contaminated oil fed into said stripping section with a solvent selective for polychlorinated biphenyl compounds; (b) partially separating said solvent from extract produced in said extraction zone by partially distilling said extract in a distillation zone to produce residue containing about 20 to 80% of said solvent; (c) separating said solvent from said bottom residue by cooling said bottom residue to produce a solvent phase and an oil/polychlorinated biphenyl phase and then separating said solvent phase from said oil/polychlorinated biphenyl phase; (d) continuously recycling a major portion of said oil/polychlorinated biphenyl phase from step (c) to said enriching section of said extraction zone to extract polychlorinated biphenyl compounds from said recycled portion with solvent exiting said stripping section of said extraction zone to increase the polychlorinated biphenyl content of said extract exiting said extraction zone and to minimize oil loss; (e) withdrawing a minor portion of said oil/polychlorinated biphenyl phase from step (c) as a disposable polychlorinated biphenyl residue; (f) recycling said separated solvent phase from step (c) to said distillation zone of step (b); and (g) recycling said separated solvent phase from step (b) to said extraction zone of step (a).
Claim 2
Independent Claim
229 words
A method for continuously removing polychlorinated biphenyl compounds from oil contaminated therewith, comprising the steps of: (a) in a multiple stage extraction zone having a stripping section and an enriching section, continuously extracting polychlorinated biphenyl compounds from contaminated oil fed into said stripping section with a solvent selective for polychlorinated biphenyl compounds; (b) partially separating said solvent from extract produced in said extraction zone by partially distilling said extract in a distillation zone to produce residue containing about 20 to 80% of said solvent; (c) separating said solvent from said bottom residue by cooling said bottom residue to produce a solvent phase and an oil/polychlorinated biphenyl phase and then separating said solvent phase from said oil/polychlorinated biphenyl phase; (d) continuously recycling a major portion of said oil/polychlorinated biphenyl phase from step (c) to said enriching section of said extraction zone to extract polychlorinated biphenyl compounds from said recycled portion with solvent exiting said stripping section of said extraction zone to increase the polychlorinated biphenyl content of said extract exiting said extraction zone and to minimize oil loss; (e) withdrawing a minor portion of said oil/polychlorinated biphenyl phase from step (c) as a disposable polychlorinated biphenyl residue; (f) recycling said separated solvent phase from step (c) to said distillation zone of step (b); and (g) recycling said separated solvent phase from step (b) to said extraction zone of step (a).
Claim 3
Dependent Claim
31 words
A method according to claim 1, wherein said distillation step (b) is carried out at a pressure of about 50 to 150 torr and a temperature not exceeding about 150° C.
Claim 4
Dependent Claim
29 words
A method according to claim 1, wherein said solvent is selected from the group consisting of alkyl substituted formamides and acetamides, pyrrolidones, sulfoxides, glycols, glycol ethers, aldehydes, and alcohols.
Claim 5
Dependent Claim
26 words
A method according to claim 3, wherein said solvent is selected from the group consisting of N-methyl pyrrolidone, dimethyl sulfoxide, diethylene glycol monomethyl ether, and fufural.
Claim 6
Dependent Claim
14 words
A method according to claim 4, wherein said solvent in diethylene glycol monomethyl ether.
Claim 7
Dependent Claim
48 words
A method according to claim 1, wherein said extraction step (a) removes about 90 to 98 percent of the polychlorinated biphenyl compounds from the contaminated oil in about three to ten theoretical extraction stages and the solvent/oil feed ratio is in the range of about 1:1 to 4:1.
Claim 8
Dependent Claim
20 words
A method according to claim 6, wherein said extraction step (a) is carried out in about six theoretical extraction stages.
Claim 9
Dependent Claim
32 words
A method according to claim 1, wherein said extraction of said polychlorinated biphenyl compounds from said recycled portion in step (d) is carried out in about one ot six theoretical extraction stages.
Claim 10
Dependent Claim
30 words
A method according to claim 8, wherein said extraction of said polychlorinated biphenyl compounds from said recycled portion in step (d) is carried out in about three theoretical extraction stages.
References Cited (Backward Citations)
US2201549A
Cited
US2111360A
Cited
US3544453A
Cited
US3825489A
Cited
US4297206A
Cited
GB2071137A
Cited
US4299704A
Cited
US4387018A
Cited
US4405448A
Cited
US4477354A
Cited
US4430208A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-08-16 | 1992-02-15 | 1992-08-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-08-16 | 1996-02-15 | 1996-08-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-08-16 | 2000-02-15 | 2000-08-16 | $7700.00 | Window Closed / Lapsed |