NCD980602163_19811001_Warren County PCB Landfill_SERB C_Electric Utility Experience in Incineration of PBC-Contaminated Mineral Oil-OCR

Electric Utility Experience in Incineration of
PCB -Contaminated Mineral Oil
D. P . Roche
Duke Power Company
Presented at:
Southeastern Electric Exchange
Environmental Committee Meeting
Asheville, North Carolina
October 1, 1981
Electric Utility Experience in Incineration of
PCB -Contaminated Mineral Oil
Polychlorinated byphenyl (PCB), a chemical made from benzene, has been used
since 1929 for its dielectric and flame-resistant properties. The chemical
was originally manufactured by Monsanto and that company's trade names for
the various PCB compounds are used to identify them. For example, a commonly
occuring PCB in askarel (a generic name for PCB transformer fluid) is
Arochlor 1254, which is a pentachlorobiphenyl, 54% chlorine by weight.
Most capacitors in use by electric utilities contain pure PCB, usually
Arochlor 1016, a trichlorobiphenyl. Some power and distribution transformers
use askarel, which is 60% PCB and 40% chlorobenzene, as an insulating fluid
when there is a need for a highly non-flammable oil, as in public buildings,
on rooftops, or in underground vaults. Most transformers, however, especially
in the distribution network, use mineral oil, not PCB, for cooling. Some
mineral oil-filled transformers become contaminated with PCB during manufac-
ture or servicing, usually at a level below 500 ppm.
Because PCB is a highly stable, man-made chemical, it does not easily decom-
pose and can bioaccumulate and bioconcentrate. It is this property of PCB
that is of concern and is truer for the higher chlorinated PCB's. Despite
the frequent use of the words "cancer-causing" by the media in referring to
PCB, the carcinogenicity of PCB is unresolved. There is, furthermore, no
evidence of a toxic dose in humans from typical exposure to electrical grade
PCB. People have worked with PCB, in manufacturing and railroad industries
as well as in utilities, for many years without any d etectable ill hea lth
effects.
The manufacture of PCB was banned by the Environmental Protection Agency in
1979 under the Toxic Substances Control Act, and detailed regulations for
the disposal of the chemical were promulgated. The disposal regulations
will eventually be consolidate d with the h azardous waste program under the
Resource Conservation and Recovery Act. The TOSCA disposal regulations for
PCB, based on the r mal decomposition testing performed at the University of
Dayton Research Institute and also at the Sanford plant of Florida Power &
Light, require that capacitors and high-concentration PCB liquid be incin-
erated a t EPA-approved commercial facilities, and tha t PCB solid waste
(transformer c arcasses and spill cleanup waste) be buried in EPA-approved
chemcial landfills. Low-level PCB liquids (be low 500 ppm) may be incinerated
in high-efficiency boilers such as those operated by electric utilities.
Although most utility boilers can meet the requirements under TOSCA for
incinerating PCB-contaminated mineral oil, a relative few utilities have
chosen this disposa l option, including Potomac Electric Power, Baltimore Gas &
Electric, Houston Lighting & Power, Hartford Electric Light, Union Electric,
and Duke Power.
Duke Power is using a coal-fired boiler at its Riverbend Steam Station near
Mt. Holly, N. C. for its mineral oil incineration program. The plant was
selected because it is the closest to the company's central transformer shop,
PCB storage, and mineral oil recycling facility. When oil-filled transformers
needing repair o r drums of used mineral oil arrive at the facility, the oil
is analyzed for PCB at the gas chromatograph laboratory on site. If the oil
contains less than 50 ppm PCB, it is reprocessed to be used in transformers.
If the oil contains between 50 and 500 ppm PCB, or is too dirty to be re-
cycled even though it is uncontaminated, the oil is shipped by tank truck
to Riverbend for incineration, Prior to burning, the waste mineral oil is
stored at the station in a 20,000-gallon holding tank which is surrounded
by containment walls.
Mineral oil is fed to the boiler through existing atomization nozzles when
the 100 MW unit is operating at 75% load or greater, and is only burned during
the swnmer months to ensure the necessary oil temperature for proper atomiza-
tion. The oil line can be purged with fuel oil after mineral oil is burnid.
The system is equipped with an electrical interlock to trip the oil pump
if there is a loss of a coal mill or power, a low level of oil in the storage
tank, or if an emergency oil pump stop switch is actuated. Carbon monoxide
and excess oxygen in the flue gas and oil flow rate are monitored as
required by EPA. An alarm would sound in the control room if the CO concen-
tration exceeded 100 ppm. The CO concentration in the flue gas during burning
has, however, been below 30 ppm. So far this year, 10,698 gallons of PCB-
contaminated oil, and 24,515 gallons of uncontaminated waste mineral oi.l ,
have been burned at Riverbend.
During Riverbend's initial burn of PCB-contaminated oil in July, when 3,441
gallons of oil containing 464 ppm of PCB were incinerated, samples of flue
gas and fly and bottom ash were collected for PCB analysis by an outside
laboratory. Stack testing was done by Duke personnel using EPA's recommended
modified Method 5 sampling method for PCB incinerators . The sampling train
includes a thimble-type filter in the probe to trap particulates and a tube
packed with activated Florisil between the third and fourth impingers to
capture any PCB. Teflon seals were used for the glassware, and the probe
and glassware were rinsed with acetone and hexane before and after sampling.
Samples were extracted and perchlorinated, using EPA-recommended procedures,
and analyzed using a Tracor MT 220 gas chromatograph equipped with an elec-
tron capture detector. Optimum techniques for PCB recovery had been developed
in laboratory experiments by the consultant prior to the test samples. The
results of the analyses are incomplete at this time, but we do have the data
from the ash analyses. No PCB was found in the fly ash above the one ppm
detection limit of the instrument, with a demonstrated recovery of 80%. Less
than 2 ppm PCB was detected in the bottom ash slurry, with 98% recovery. The
method verification work performed in the laboratory indicates that the barely
detectable PCB concentration found in the bottom ash is probably due to back-
ground interference.
The Environmental Protection Agency is now reconsidering the PCB regulations
in response to a court order. The Edison Electric Institute and National
Electrical Manufacturers Association are jointly submitting data to EPA to
provide a basis for this rulemaking. The new regulations, when they are
issued next year, may create a need for greater disposal capability for PCB
waste. Duke Power's data, along with test results from other utilities that
have incinerated low-level PCB, support the continued or expanded use of
utility boilers for PCB destruction.