United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-85/113 Dec. 1985
&ER& Project Summary
Test Firing Refuse-Derived
Fuel in an Industrial
Coal-Fired Boiler
R. J. Vetter, M. L Smith, K. W. Ragland, R. K. Ham, and R. P. Madding
This research program evaluated the
performance of an industrial boiler
when co-firing coal and refuse-derived
fuel (RDF). An optimum boiler operating
load and RDF feed rate were determined
for the boiler tested. Boiler efficiencies
and stack emissions were also studied,
and the economics of preparing and
utilizing RDF in the boiler were eval-
uated. The operational characteristics
of the RDF feed system and the reli-
ability and practicability of receiving,
storing, and firing RDF are reported.
An RDF Receiving and Feed Facility
was designed and constructed to feed
RDF to boiler No. 5, which had been
modified to fire RDF, at the Oscar Mayer
and Company, Madison, Wisconsin
plant. Boiler No. 5 is one of two base
load coal-fired boilers used by Oscar
Mayer to produce steam for electrical
generation and process purposes. The
co-firing tests' were conducted at var-
ious boiler loads and feed rates to
determine an optimum operating condi-
tion. RDF from the Madison Area Re-
source Recovery Center was augered
onto a slider belt conveyor and trans-
ported to the boiler house, where it was
mechanically split into six fuel streams
and fed into the test boiler.
Twenty-one tests were run from July
1980 to May 1981. Studies included
evaluation of the coal and RDF; bottom
ash, economizer ash, cyclone ash, and
fly ash; underfire and overfire air; boiler
efficiency; and gaseous emissions in-
cluding SO2, NO, HCI, and CO. Sixty-
two trace elements in the fuel and ashes
were measured.
The tests demonstrated that RDF
coutd reliably be fed into an industrial
boiler at feed rates up to 48%, on a heat
input basis, while maintaining a steady
steam load. Particulate emissions under
these test conditions were not signif-
icantly increased when firing RDF.
There was no negative physical impact
on the boiler.
This Project Summary was developed
by EPA's Hazardous Waste Engineering
Research Laboratory, Cincinnati, OH,
to announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Purpose and Objective
This research project was structured
to:
1. Evaluate an industrial boiler's per-
formance when cofiring coal and
RDF at various boiler loads and feed
rates to determine optimum operat-
ing conditions.
2. Evaluate air emissions and the
performance of an existing me-
chanical air cleaning system when
cofiring coal and RDF in an indus-
trial boiler.
3. Analyze the economics of utilizing
RDF in an industrial boiler.
4. Evaluate the operational character-
istics of the RDF feed system and
the reliability and practicability of
receiving, storing, and firing RDF at
an industrial operation.
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Operation and
Performance
The project was to demonstrate that
RDF prepared from municipal solid waste
can be effectively co-fired with coal m a
retrofitted industrial spreader-stoker boil-
er rated at 125,000 Ib steam/hr (55,555
kg/hr) equipped with a multi-cyclone
paniculate collector
The best operating load, based on steam
demand and boiler operation, was judged
to be 90,000 Ib steam/hr (40,000 kg/hr)
with 33% of the steam load carried by
RDF. This represents a coal feed rate of
3.5 ton/hr (3,200 kg/hr) and an RDF feed
rate of 3.8 ton/hr (3,500 kg/hr).
The RDF, as produced for the test
program, had an average heating value of
5,785 Btu/lb (13,455 kJ/kg) with 21%
moisture and 14% ash as received. The
RDF had a nominal top size of 2 inches (5
cm), 90% less than 3A inch (1 9 cm), and
mass mean size of 0.30 inches (0.76 cm).
Fuel Analysis and Emissions
Analyses of coal and RDF indicated that
RDF had higher volatile matter and lower
fixed carbon contents than coal. The
ultimate analyses showed that RDF was
lower in carbon, nitrogen, and sulfur, and
higher in moisture, hydrogen, chlorine,
ash, and oxygen contents than coal. Coal
had about twice as high a heating value
as RDF on an as-fired basis. The main
reason for the difference in heating values
is the higher oxygen, moisture, and ash
content of RDF.
Boiler efficiency decreased 1 % for each
10% of heat load replaced by RDF. This
decrease in efficiency was due primarily
to additional moisture in the RDF and
additional moisture from combustion of
hydrogen in the RDF.
Paniculate emissions ranged from 0.60
to 1 28 Ib/million Btu (0.26 to 0.55
kg/million kJ). Co-firing tests in the Fall
of 1980 produced excessive paniculate
emissions, but those conducted in the
Spring of 1981 showed no significant
increase in paniculate emissions as
compared to the coal-only tests. It is
believed that operating experience and
lower RDF ash content contributed to the
improvement in the later tests.
When RDF and Illinois coal were co-
fired at 90,000 Ib steam/hr (40,000
kg/hr) with 33% of the heat load carried
by the RDF, the sulfur dioxide emissions
were reduced by half to 2.8 Ib/million Btu
(1.2 kg/million kJ), the hydrogen chloride
emissions were increased 50% to 0.33
Ib/million Btu (0.14 kg/million kJ), the
carbon monoxide emissions were insig-
nificant, and the nitric oxide emissions
remained about the same at 0.4 Ib/million
Btu (0.17 kg/million kJ).
The trace element analyses of the fuels
indicated that RDF was higher than coal
in 36 out of 63 elements analyzed.
Elements that were higher in concentra-
tion mRDFthan in coal showed a general
increase in all ashes with an increasing
input of RDF When RDF was burned,
trace metals were measured in the fly
ash. Lead and zinc were each 2% of the
total paniculate emissions. The other
trace metals were each one to three
orders of magnitude lower
The RDF receiving and feed system
operated dependably, providing a clean
and constant flow of RDF to the boiler
The combination feeders distributed the
RDF evenly throughout the boiler, main-
taining a constant steam load
Economic Analysis
The RDF storage and feed system at the
Oscar Mayer and Company Plant in
Madison, Wl could be expanded to burn
12,500 to 15,000 tons per year of RDF
while operating at 5 tons/hr, 10 to 12 hrs.
per day, 5 days per week. The fuel
replacement rate would be approximately
40%. The projected operating costs to
receive and burn 12,500 and/or 15,000
tons of RDF annually in the system
described is $90,000 or $7.20 and $6.00
per ton respectively. The total September
1981 capital cost to install a permanent
system as described would be $700,000.
The cost to expand the test facility to a
permanent installation is estimated to be
about $400,000. The economic analysis
for this project indicates that the condi-
tions to develop a market appear favor-
able.
Recommendations
The cofiring of RDF and coal in a
retrofitted industrial spreader-stoker
boiler should be further examined. It is
recommended that additional cofiring of
coal and RDF examine boiler performance
while firing RDF in the size range of 1 inch
to 4 inches. RDF in this size range can be
recovered from the residue stream at
Madison's Energy Recovery Plant, further
reducing the quantity of waste being
landfilled.
Proper air distribution in a boiler retro-
fitted to cofire coal and RDF is essential.
Further testing is needed to optimize air
distribution in a boiler which is cofiring
coal and RDF in order to minimize excess
air and reduce paniculate emissions.
Tests should include varying the ratio of
underfire air to overfire air, and the
location, angle, and penetration of the
overfire air jet stream.
The short-term cofiring of coal and RDF
was successfully accomplished in a retro-
fitted industrial spreader-stoker boiler.
No significant problems related to boiler
operation or performance were evident
during this test program. To further
substantiate these preliminary findings, a
long-term coal and RDF cofired test
program at optimum boiler load and RDF
feed rates should be conducted to:
1. Ensure boiler operator proficiency.
2. Establish a broad basis for eval-
uating emissions
3. Investigate boiler fouling, corrosion,
slagging, superheater degradation,
and additional maintenance prob-
lems.
The composition and characteristics of
paniculate from a coal and RDF cofired
boiler varies from that of a straight coal-
fired unit; therefore, the performance of
various types of paniculate control equip-
ment need to be studied under the cofired
condition.
Finally, the cofiring of coal and RDF in
an industrial spreader-stoker boiler
should be encouraged, both as a method
of energy recovery and as a means of
reducing landfill space requirements.
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R. J. Vetter is with the City of Madison, Madison, Wl 53709; M. L. Smith is with M.
L Smith Environmental. Oak Brook. IL 60521 ;K. W. Rag/and. R. K. Ham, andR.
P. Madding are with the University of Wisconsin, Madison, Wl 53706.
Michael Black is the EPA Project Officer (see below).
The complete report, entitled "Test Firing Refuse-Derived Fuel in an Industrial
Coal-Fired Boiler," (Order No. PB 86-115 094/AS; Cost: $16.95, 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:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES P/
EPA
PERMIT No G-35
Official Business
Penalty for Private Use $300
EPA/600/S2-85/113
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