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
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   PERMIT No G-35
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Penalty for Private Use $300
EPA/600/S2-85/113

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