v>EPA
United States
Environmental Protection
Agency
Industrial Environmental Researc
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S7-81-031 July 1981
Project Summary
Facilities Evaluation of
High Efficiency Boiler
Destruction PCB Waste
J. E. Cotter and R. J. Johnson
A rendering plant by-product,
yellow grease, was found to be
contaminated by PCB's from a trans-
former leak. The PCB content (under
500 ppm) determines the method of
disposal under 40 CFR Part 761. For
this evaluation, destruction in a high-
efficiency boiler was evaluated as an
alternative to landfill disposal. The
process steam boiler belonging to the
waste owner, Seattle Rendering
Works, was evaluated as a candidate
site for waste destruction. The logis-
tics and fuel handling requirements
were found to be feasible to set up in a
short time, and the boiler size and
residence time were determined to be
likely to allow high destruction effi-
ciency. With 99.9% destruction of
PCB's, the downwind concentration
was estimated by diffusion modeling
to be less than OSHA limits for
industrial exposure. Fuel characteris-
tics of the yellow grease were used to
support the recommendation for
100% grease fired as fuel.
A second high-efficiency boiler
candidate was also evaluated. The
Shuffleton power plant, operated by
Puget Sound Power & Light Company,
operates three boilers from a common
oil fuel supply system. The size and
facilities at this site were determined
to satisfy all the prerequisites for high-
efficiency boilers (40 CFR Part 761),
and to best be operated by blending
the waste with the normal fuel oil
supply. A 30% waste blend was
evaluated and found to be completely
miscible and feasible with respect to
logistical support.
A verification test burn was recom-
mended and outlined for either candi-
date site. Current EPA protocol and
policy developments for PCB destruc-
tion were found to be appropriate for
the preparation of a candidate facility
test plan and an example public
notice.
This report is submitted in fulfill-
ment of Contract No. 68-02-3174,
Work Assignment No. 11, by TRW
Environmental Engineering Division,
under sponsorship of the U.S. Envi-
ronmental Protection Agency. This
report covers the period January 10,
1980 to April 1,1980, and work was
completed as of July 1, 1980.
This Project Summary was develop-
ed by EPA's Industrial Environmental
Research Laboratory. Research Tri-
angle Park. NC. to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Source of Contaminated
Waste
A quantity of tallow (yellow grease),
produced from the rendering of chicken
packing by-products, was contaminated
by a transformer leak at a packing plant
in Billings, MT. The incident occurred in
1979, and by mid-1979 the contamina-
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ted yellow grease had already been sold
to distributors who had combined the
contaminated material with other
stocks. Routine FDA inspections identi-
fied the PCB contamination, and subse-
quent analyses of blended stocks were
carried out. The FDA notified the EPA
Region X headquarters in September
1979 of the results of those analyses
where the PCB content was greater
than 50 ppm, and therefore subject to
EPA jurisdiction.
All grease stocks containing more
than 50 ppm of PCB were traced to two
tanks at 290011 th Avenue SW, Seattle,
WA. The tanks contain (as of the date of
this report) approximately 500,000 Ibs
and 600,000 Ibs, or about 150,000
gallons total. FDA inspection of the
grease revealed PCB concentrations
ranging from 116 to 391 ppm, based on
four samples taken from the tanks, and
duplicate assays.
Disposal Options
The contaminated grease, having a
PCB content of under 500 ppm, does not
require destruction in an EPA-approved
incinerator. The final ruling governing
PCB disposal, 40 CFR Part 761, identi-
fies destruction in high-efficiency
boilers or disposal in chemical landfills
as acceptable alternatives.
"High-efficiency" boilers are defined
to include power generation boilers and
industrial boilers that operate at a high
combustion efficiency (99.9%) as
def i ned by the percentage ratio of CO 2to
CO+COz concentrations in the combus-
tion gases. These boilers are assumed
to be capable of achieving 99.9% or
greater PCB destruction efficiency.
There are two approved locations in
EPA Region X where PCB contaminated
waste may be disposed. These chemical
landfills are Chem-Nuclear Systems
(Arlington, OR) and Wes-Con (Grand
View, ID). It was estimated by Region X
that landfilling would cost a waste
owner around 80/lb.
Prerequisites for High-
Efficiency Boiler Destruction
The Regional Administrator may
grant approval for PCB thermal destruc-
tion in a boiler if a number of prerequi-
sites are met:
1. The boileris rated at a minimum of
50 million Btu/hour.
2. The PCB contaminated waste
comprises no more than 10% of
the total volume of fuel.
3. The waste will not be added to the
combustion chamber during
boiler start-up or shut-down
operations.
4. The combustion emissions will
contain at least 3% excess oxygen
and the carbon monoxide
concentration will be less than 50
ppm for oil- or gas-fired boilers or
100 ppm for coal-fired boilers.
5. The combustion process will be
monitored continuously or at least
once each hour that the PCB con-
taminated wastes are being
burned to determine the percent-
age of excess oxygen and the
carbon monoxide level in the com-
bustion emissions.
6. The primary fuel and waste feed
rates are monitored at least every
15 minutes whenever burning the
waste.
7. The carbon monoxide and excess
oxygen levels are monitored at
least once an hour, and if they fall
below the levels specified, the
flow of wastes to the boiler is
stopped immediately.
8. Records are maintained that
include the monitoring data in (5)
and (6), above, and the quantities
of PCB-contaminated waste
burned each month. When burn-
ing PCB wastes, the boiler must
operate at a level of output no less
than the output at which the
reported carbon monoxide and
excess oxygen measurements
were taken.
Candidate Sites for Waste
Destruction
Two boiler/incinerator sites were
selected for study in this report: the
steam boiler at the Seattle Rendering
Works plant in Seattle, WA, and the
utility boilers at Puget Sound Power &
Light's Shuffleton Plant in Renton, WA.
Seattle Rendering Works
Analysis
Facility Operations
Background
The Seattle Rendering Works, Inc.,
facility is located at 5795 S. 130th
Place, Seattle, WA, adjacent to the
Duwamish River and the Foster Golf
Course. It is a dual-fuel (gas and/or No.
6 oil) water-tube Cleaver-Brooks model
(Delta D-60) with a design capacity of
35,000 Ibs steam/hr. The oil burner is a
low-pressure air-atomizing type. The
rated gas-fuel efficiency is 78%, so the
design heat input is 46,000,000
Btu/hour. The furnace volume is 755 cu
ft in the immediate combustion zone,
excluding the upper radiant section.
Typical stack temperatures at maximum
firing are 550-560°F. The combustion
zone temperatures are in excess of
2200°F at the back wall. A steam-
heated preheater is capable of raising
incoming oil temperatures of 100-
240°F. The oil feed pressure is main-
tained by a gear pump, which is protec-
ted by a duplex 30-mesh strainer on the
suction side.
The boiler operates at full modulation
from a low- to high-fire position, regula-
ted by steam pressure, which is directly
affected by steam demand. Since a PCB
destruction program would be required
to operate at a steady rate of waste fuel
consumption, there would be a change
from normal boiler operating practice. If
the fuel waste were consumed at maxi-
mum fuel feed rates, then some of the
generated steam would have to be
dumped when process demands
dropped off. In the case of waste fuel
consumption at some intermediate rate,
auxiliary heating must be made up by
firing natural gas simultaneously during
high demand periods, and excess steam
would have to be dumped at low
demand conditions.
Recommendations on the
Feasibility of Using the
Seattle Rendering Boiler
Suitability of Yellow Grease as
Boiler Fuel
The inspection of a grease sample
from one of the contaminated ship-
ments (Fujitsuki Maru No. 1, port tank
09-15-79) produced the results, shown,
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in Table 1; two grades of fuel oil are
shown by comparison. These inspection
results provide some confidence that
the grease could be burned undiluted,
since:
• The viscosity is between that of
No. 5 and No. 6 fuel oil, so
atomization should be good with a
burner that is usually run with No.
6 oil.
• The fuel value of the grease is 93%
of a No. 6 oil value.
• The ash content is low.
Furthermore, Pierce Packing*
confirmed that they had burned 600,-
000 Ibs of grease in their steam boiler,
with good combustion characteristics.
Estimated Destruction
Efficiency
The residence time of the PCB's in the
furnace combustion zone has to be
determined as part of the evaluation of
destruction efficiency. At a waste feed-
rate of 6 gpm, the actual volumetric
flowrate of combustion gases through
the 755-cu ft furnace volume is 43,097
acfm, yielding a residence time of 1.1
seconds. The residence time will be
twice as long at a feedrate of 3 gpm,
since the gas volumetric rate is half as
much.
The estimated destruction efficiencies
under these conditions depend on a
number of factors, including:
• Comparison of residence.time and
temperature to those specified in
40 CFR, Part 761, Subpart E:
1200°C (2191 °F) @ 2 seconds, or
1600°C (2912°F) @ 1.5 seconds
dwell: (these conditions are for
waste incinerators, burning PCB
wastes of any concentration).
• Estimated efficiency of the
Cleaver-Brooks burner, and the
ease of atomization of the grease
fuel, as compared to No. 6 fuel oil.
• The likelihood of achieving high
destruction efficiencies with PCB
concentrations of a few hundred
ppm, vs. percentage range con-
centrations found in some other
wastes (it's always easier to
remove high percentages of high
concentrations). A 99.9%
destruction efficiency is often
obtained with high efficiency
incinerators and high PCB
concentrations.
The likelihood of achieving 99.9 + %
PCB destruction is estimated to be very
good at a 3 gpm feedrate, since the time
and temperature relationships may
approximate those of good incinerator
practice. It is less certain that a 6 gpm
feedrate would yield equivalent de-
struction efficiency, but the operation at
6 gpm would certainly be preferred for
reducing the program length. Therefore,
the verification test should determine
the destruction efficiency and combus-
tion temperature at both feedrates.
The boiler operation under automatic
control will allow full modulation from
low- to high-fire, regulated by steam
pressure. High-fire fuel demand would
be about 6 gpm, since the Btu content of
grease and No. 6 oil are similar. Low-fire
demand is about 25% of high fire, or
about 1.5 gpm.
Although the Cleaver-Brooks boiler at
Seattle Rendering does not meet the
standard prerequisite of 50 million Btu/
hr heat input (at full output), it comes
close at 46 million Btu/hr.
It is recommended that the standard
prerequisite of a maximum blend of 10%
waste (with the remainder fuel oil) is
less appropriate for the Seattle Render-
ing program than a 100% waste fuel
choice. The 10% blend is based on the
possibility of using any waste, including
those with very low fuel value. As al-
ready noted, the Btu content of yellow
grease is very close to No. 5 or No. 6 fuel
oils, and the combustion characteristics
are judged to be good. Furthermore,
there are no facilities available for
blending grease and fuel oil.
Environmental Impact
The anticipated impact of PCB waste
burning at the Seattle Rendering facility
was modeled with a point-source dis-
persion model, actual stack dimensions,
and a range of local meteorological con-
ditions, as reported from the PSAPCA*
•Billings, MT.
"Puget Sound Air Pollution Control Agency.
station at Tuckwila/South Center,
about 2 miles south of the plant.
The flat-terrain dispersion model is
only useful for impact analysis up to the
point of a significant terrain change. The
prevailing winds at the source location
'(35% of the time) are south to south-
west, with neutral (Class "D") atmos-
pheric stability.
There is a sharp terrain rise of 50 m
only 400 m in a prevailing (SSW) direc-
tion from the rendering plant source.
The calculated effective stack height is
40-65 m. Model predictions at 400 m of
PCB concentrations at the plume
centerline (which is a worst-case condi-
tion) are as follows:
Feed Wind No PCB 99.9% PCB
Rate Speed Destruction Destruction
gpm m/sec figm3 ng/m3
6 10 6.4 6.4
6 4 16.4 16.0
3 10 1.6 1.6
3 4 4.0 4.0
The modeling estimates are based on
calculated emission quantities as
follows:
• 6 gpm feedrate using worst-case
of 400 ppm PCB's: 9110 scfm
stack discharge, 0.12 g/sec
uncontrolled, 0.12 mg/sec con-
trolled emission rates.
• 3 gpm feedrate, using moderate-
case of 175 ppm PCB's: 4555 scfm
stack discharge, 0.03 g/sec un-
controlled, 0.03 mg/sec control-
led emission rates.
The ground-level concentration of the
plume under flat-terrain assumptions
may be more realistic at 1.5 to 2 km
downwind, after the plume has passed
over the bluff. The atmospheric PCB
concentrations for a 99.9% efficient de-
struction operation are in the range of
0.1 to 0.4 ng/m3.
Techniques for ambient monitoring of
these extemely low PCB concentrations
are still being developed, but it is recom-
mended that an attempt be made to
make such a measurement at the most
likely downwind position, in support of
the verification test.
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An analysis of downwash concentra-
tions of PCB's was also done, using the
building as an area source. In a down-
wash model, dispersal of pollutants
occurs in the immediate, ground level
vicinity of a source, rather than through
an elevated plume. Calculated atmos-
pheric concentrations of PCB's were
estimated to be around 0.2 ng/m3 with
99.9% destruction. The OSHA limit for
worker exposure to PCB's on an 8-hour
day, 40-hour week basis is 1 mg/m3
with 42% PCB chlorine content, so that
the downwash concentration certainly
does not threaten worker safety.
Shuffleton Power Plant
Analysis
Facility Operation Background
The Shuffleton Power Plant, owned
by the Puget Sound Power and Light
Co., (PSPL), is located at 1101 Lake
Washington Blvd., Renton, WA.
Shuffleton is operated at a steady level
of 330,000 Ib/hr of steam in each of
three oil-fired boilers. The Shuffleton
boilers are balanced draft type (FD, ID
fans); there are 16 Peabody mechanical
burners in each boiler, burning No. 6
fuel oil heated to 200°F.
The available measurements include
air/fuel ratio, oil pressure, windbox
pressure, furnace draft, fuel oil temper-
ature, air preheater temperature and
pressure, and oxygen in the stack gases.
Fuel oil is not presently metered, al-
though an orifice exists in the fuel oil
line.
The fuel oil is supplied from large
storage tanks to two smaller service
tanks, each having a working capacity of
800 bbls. The tanks are run alternately,
on about a 5-hour cycle, while 3600 to
3900 bbl per day of fuel oil are con-
sumed. The tanks have open hatches at
the top which could be used for pumping
in other fuels to get a mixed fuel. The
fuel is kept at 150°F in the service tanks.
The fuel oil is pumped out of the service
tanks by three 80 gpm pumps, and dis-
tributed through heat exchangers to
raise the fuel temperature to 200°F. The
fuel is then injected into each of the
burners in the three boilers. The viscos-
ity of No. 6 oil is sufficiently lowered by
the 200°F preheat to get good burner
and combustion performance.
The operations of the Shuffleton
power plant are not expected to be
hindered by the proposed PCB waste
incineration, as indicated by the follow-
ing discussion on feasibility. Three-shift
operations coverage of the boiler and
fuel handling system will provide the
necessary surveillance of combustion
performance that is needed for PCB
incineration. There is reason to believe
that close surveillance is mandatory for
maintaining good combustion at
Shuffleton. The plant has received
frequent citations for opacity violations,
despite a test of the No. 1 boiler which
showed paniculate emissions within
compliance. A combustion consul-
tant's report submitted to Puget Power
identified possible causes of poor
combustion to include inadequate fuel
atomization (due to lowfuel oil tempera-
ture) and dirty burner.
Recommendations on the
Feasibility of Using the
Shuffleton Boilers for PCB
Waste Incineration
Suit ability of Yellow
Grease as a Boiler Fuel
The first consideration for suitability
is the determination of miscibility, or
degree of mixing, of grease and No. 6
fuel oil, since using a blended fuel is
technically the simplest method for
waste incineration in a large boiler.
Yellow grease and No. 6 fuel oil mixing
tests were conducted by Northwest
Laboratories at two blend ratios (10%
and 30% grease, by volume) and two
temperatures (180°F and 200°F). The
results of these four tests were consis-
tent; the blends were miscible, with no
stratification, at all conditions.
The inspection of a grease sample
from one of the contaminated batches
by Northwest Laboratories produced the
results reported in Table 1; two grades
of fuel oil are shown by comparison.
The previous inspection results pro-
vide further confidence that the grease
will combust well with No. 6 fuel oil.
since:
The viscosity is between that of
No. 5 and No. 6 fuel oil, so burner
atomization with the blended fuel
should be good.
The fuel value of the grease is 93%
of a No. 6 oil value.
The ash content is low.
Estimated Destruction
Efficiency
The residence time of the PCB's in the
boiler combustion zone is a considera-
tion in the evaluation of destruction effi-
ciency. At a typical fuel feedrate of 38
gpm, and 4-5% excess oxygen, the cal-
culated rate of combustion gas flow is
1111 std cu ft/sec. The estimated resi-
dence time in the lower half of the boiler
is 2.5 seconds, with another 2.5
seconds dwell in the upper zone. The
temperature in the combustion zone, in
the vicinity of the burners, has been
measured at 2800°F.
The estimated destruction efficiencies
under these conditions depend on a
number of factors, including:
• Comparison of residence time and
temperature to those specified in
40 CFR, Part 761, Subpart E:
1200°C (2192°F) @ 2 seconds, or
1600°C (2912°F) @ 1.5 seconds
dwell: (these conditions are for
waste incinerators, burning PCB
wastes of any concentration).
• Efficiency of the burners and the
ease of atomization of the grease
and No. 6 fuel oil blend.
• The likelihood of achieving high
destruction efficiencies with
blended PCB concentrations of
less than 100 ppm, vs. percentage
range concentrations found in
some other wastes (it's always
easier to remove high percentages
of high concentrations). A 99.9%
destruction efficiency is often ob-
tained with high efficiency incin-
erators and high PCB concentra-
tions.
The likelihood of achieving 99.9%
PCB destruction is estimated to be good,
given the similarity of the boiler condi-
tions to good incinerator practice, and
the compatibility of the grease and No. 6
fuel oil.
It is recommended that the PCB incin-
eration be conducted with a grease-to-
fuel oil ratio of 30/70 instead of the
standard prerequisite ratio of 10/90.
There are good arguments for using a
30% blend, since the length of time
needed to complete the effort will be
shortened by a proportionate amount,
and the grease is not expected to cause
any combustion problems or available
heat reductions. The environmental
consequences of burning a 30% blend,
and the logistical limitations of support- |
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Table 1. Laboratory Inspections
Grease
Viscosity
SUS @ 122°F
SUS @ 200°F
Density, Ib/gal
@ 122°F
@ 180°F
Btu/lb
Moisture %
Water & Sediment %
Carbon %
Hydrogen %
Oxygen %
Sulfur %
Ash %
143.7
59.8
7.459
7.266
16.779
0.41
2.8
76.6
11.9
10.5
0.01
0.12
40
@ 60°, 8.0
18,250
0.05
1
87.5
10.2
—
1.1
—
300
@ 60°, 8.33
18,000
0.05
2
88.3
9.5
—
1.2
0.1
worker exposure on an 8-hour day, 40-
hour week basis is 1 mg/m3 with 42%
chlorine content in the PCB's.
No. 5 Fuel Oil No. 6 Fuel Oil Techniques for ambient monitoring of
these extremely low PCB concentra-
tions are still being developed, but it is
recommended that an attempt be made
to make such a measurement at the
most likely downwind position, in sup-
port of the verification test.
Stability Class
FED
Data Factor— 3.95 2.11 0.027
Location of
max. 1 hr
PCB con-
concentration at 2 km 2km 12km
groundlevel NE NE NE
ing a higher grease percentage, are
discussed below.
Environmental Impact
The anticipated impact of PCB waste
burning at Shuffleton power plant was
modeled with the EPA "Valley" model,
which takes into account a certain
amount of terrain variation. The com-
puter program was run by the PSPL
quality control staff, using terrain and
stack dimension parameters already set
up for the Shuffleton plant and vicinity.
The model was run with a low wind
speed of 2.5 m/sec and a prevailing
southwest wind, over a range of atmos-
pheric stability conditions. The most
stable conditions ("F" stability) usually
yield the highest ground concentrations
of a pollutant, since dispersion by air
mixing is minimal. The following nor-
malized data factors were computed for
stability Classes A through F (A being
the most unstable). The data factors are
multiplied by an estimated emission
rate to get a maximum 1-hour concen-
tration at the indicated downwind
distance.
The maximum 1 -hour PCB concentra-
tion can then be estimated using "F"
stability conditions, from the emission
rates determined as follows:
a. 10% blend, 3200 gal of 400 ppm
(worst-case) grease burned over a
5-hour period yield 0.24 g/sec(no
control), or 0.24 mg/sec (99.9%
controlled) emission rate.
Worst-case model prediction for
downwind PCB concentration =
3.95 x 0.24 = 0.9 fjg/m3 (no
control), or 0.9 ng/m3(99.9% con-
trol) at 2 km NE of plant.
b. 30% blend yields three times the
emission rate above—0.71 g/sec
(no control), or 0.71 mg/sec (99.9%
control).
Estimated downwind PCB con-
centration at 2 km NE then will be:
2.7 fjg/m3 (no control), or 2.7
ng/m (99.9% control).
These estimates can be compared to
the OSHA exposure limit for PCB's. The
OSHA allowable concentration for
Data Factor —
Stability Class
C B A
0.129 0.245 0.20
Location of
max. 1 hr
PCB con-
concentration at 4 km
groundlevel NE
2km
NE
near
plant
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J. E. Cotter and R. J. Johnson are with TRW, Inc., Redondo Beach, CA 90278.
David C. Sanchez is the EPA Project Officer (see below).
The complete report, entitled "Facilities Evaluation of High Efficiency Boiler
Destruction PCB Waste," (Order No. PB 81-178 287; Cost: $6.50, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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United States Center for Environmental Research Fees Paid
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