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United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-85/116 Dec 1985
Project Summary
Emissions Assessment for
Refuse-Derived Fuel Combustion
Bruce W. Rising and John M. Allen
This project examines the emissions
resulting from the combustion of refuse-
derived fuels (RDF) and coal. The two
RDFs used were Eco-Fuel II, a pulver-
ized product, and a shredded RDF from
Americology. Both were palletized be-
fore burning.
The RDF and coal were burned in a
small spreader-stoker fired boiler. The
parameters that were varied in this
program were RDF type and amount of
coal burned with the RDF. In two
experiments a waste chemical, trietha-
nolamine, was added to the fuel, and its
destruction efficiency was assessed.
Analyses of the flue gases identified
low levels of hydrocarbons, nitric oxide,
carbon monoxide, and sulfur dioxide.
The participate loadings increased as
the percentage of RDF in the total fuel
increased. More than half of the partic-
ulate loading was submicron in size
when RDF was fired without coal. Large
quantities of polycyclic organic mate-
rials were detected in those experiments
in which the shredded and pelletized
RDF was fired in the furnace. Nodioxins
were detected in those tests in which it
was analyzed. In the experiments in
which RDF was the only fuel, lead
emissions were several orders of mag-
nitude above the levels detected in the
coal base run. Based upon the flue gas
analysis, the destruction of the trietha-
nolamine was complete.
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).
Introduction
The use of waste materials as a fuel
substitute is a concept that has received
close examination in recent years.
Waste-to-energy combustion systems
have been used for many years in Europe.
However, the United States' approach is
somewhat different from the approach
used in Europe. In the United States a
major effort has been organized to pro-
mote the combustion of RDF in waste-to-
energy systems in contrast to the mass
burning approach utilized in Europe. An
RDF is a processed municipal solid waste
which has had as much non-combustible
material (sand, metals, etc.) removed as is
technically and economically feasible.
The combustible part of the waste (paper,
plastics, etc.) is then subjected to shred-
ding to reduce the size of the fuel. The
final product (RDF) may then be burned in
a suspension burning mode, a turbulent
well mixed bed, or a fixed bed.
The RDF may also be further processed
into a form known as densified RDF (d-
RDF) which requires palletizing, briquet-
ting or otherwise compacting the RDF
into larger more dense pieces.
In this study, a pelletized form of RDF
was used as a fuel in the emissions
assessment program. Two types of RDF
(Eco-Fuel II,* obtained from Combustion
Equipment Associates, E. Bridgewater,
MA, and Americology, obtained from
American Can Co., Milwaukee, Wl) were
fired with and without the addition of coal
in a small spreader-stoker fired boiler. A
complete assessment of the flue gases
was performed by continuous monitors
and by batch collection techniques and
•Mention of trade names or commercial products
does not constitute endorsement or recommenda-
tion for use.
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analysis techniques. Also, analyses were
performed on the gaseous and particulate
samples extracted by the Source Assess-
ment Sampling System (SASS)
A further addition to the experimental
program required an assessment of the
destruction of a hazardous waste material
that was co-fired with the coal/RDF fuel.
The degree of destruction of the waste
was determined by monitoring the antic-
ipated by-products of the waste material.
This waste material was mixed with the
RDF before pelletization, andthe resulting
pellets were co-fired with coal.
Objective and Scope
The objective of this program was to
perform an emissions assessment of the
combustion of RDF both with and without
the co-firing of coal. The combustion was
in a stoker-fired boiler, with most of the
combustion occurring in a fixed bed of
burning fuel on a grate. The assessment
was performed by sampling gaseous and
particulate emissions and by conducting
analyses on the samples extracted from
the flue gas stream. Additionally, chem-
ical analyses were performed on the fuels
used, and other effluent solids from the
boiler.
The research program included two
different RDFs and a low sulfur coal. Each
fuel was fired separately and each RDF
was co-fired with the coal. The coal was
fired separately in one test as a bench-
mark, permitting comparison of the emis-
sions from the two RDFs with those from
coal.
Also, the program included an assess-
ment of the destruction of a hazardous
waste material that was co-fired with a
coal/RDF fuel. The degree of destruction
of the waste was determined by monitor-
ing all of the anticipated by-products of
the material. Triethanolamine was used
as the hazardous material.
Particulate Emissions
The boiler used in these tests did not
have a specific particulate control device
such as a cyclone, although small
amounts of fly ash settled in the boiler
tubes. With Eco-Fuel II pellets burning as
the only fuel, the stack emissions were
lower than when burning only coal, or
when burning both coal and pelletized
Eco-Fuel II. Burning the Amencology
pellets resulted in appreciable higher
particulate emissions than when burning
Eco-Fuel pellets
The particles less than 1 fjm in diameter
comprised the largest fraction of the
particulate concentration in experiments
in which RDF was used. In the coal-only
run, the submicron particulates com-
prised 20 percent of the total loading. In
three tests in which coal and Eco-Fuel II
were co-fired, the submicron particles
comprised approximately 55 percent of
the total particulate loading. In the exper-
iment which used Eco-Fuel as the only
fuel, the submicron particulates com-
prised 83 percent of the total loading,
although this experiment had the lowest
total particulate concentration. The ex-
periments in which the Americology RDF
was co-fired with coal and then fired as
the only fuel, the submicron particulate
loadings comprised 71 percent and 85
percent of the total loading, respectively.
Also, these two experiments produced
the highest total particulate concentra-
tions.
Based on the data collected, it is evident
that both RDFs have a tendency to
produce large quantities of submicron
particulate matter; morethan when burn-
ing coal. Also, a pale blue haze was
evident at the stack during the two
Americology tests, indicating the pres-
ence of a large amount of small-sized
particulates. The fact that this haze was
not observed during the Eco-Fuel tests
may be attributed to the lower concentra-
tions of submicron particulates in the
gases, the higher strength of the Eco-Fuel
pellets, or the chemical/physical process-
ing that produced the Eco-Fuel
Sulfur Dioxide (SO2)
The SO2 emissions ranged from a high
value of approximately 480 ppm in the
coal-only experiment to a low value of
approximately 98 ppm in the Americology
only experiment. Although the Eco-Fuel II
had a lower sulfur content than coal on a
weight basis, the sulfur content per Btu
was nearly the same. Thus, in comparison
of tests with and without coal co-firing,
only a small reduction in sulfur emissions
was achieved in the Eco-Fuel runs. The
fraction of sulfur fired that was emitted as
SC>2 varied between 75 and 100 percent
of the sulfur fired in all runs
Nitrogen Oxides (NOX)
The nitric oxide (NO) emissions varied
from a low of 1 50 ppm in tests firing coal +
Americology to a high of 260 ppm in tests
firing coal + Eco-Fuel II in which trietha-
nolamme had been added to the Eco-Fuel
II. Since the addition of triethanolamine
raised the nitrogen content of the fuel, it
would be expected that the NO emissions
would increase. In those tests in which no
triethanolamine had been added, the NO
levels ranged from 1 50 ppm to 220 ppm
Thus, the addition of the amine had a
perceptible but small influence of NO,
emissions.
When the RDF was co-fired with coal,
the nitrogen emitted as NO represented
approximately one quarter of the fuel-
bound nitrogen. Higher emissions of NO
relative to the nitrogen in the fuel were
observed in the RDF-only test runs.
Chlorides
As expected, chloride emissions in-
creased as the chloride concentration in
the fuel increased. The lowest stack
concentrations, 126 ppm were recorded
in the coal-only test. The highest concen-
trations, 245 ppm were recorded in the
Americology test.
A chloride mass balance was achieved
in only two tests, one in which the
Americology + coal was the fuel, the other
in which the Americology was the only
fuel In the test in which Eco-Fuel II was
the only fuel, 10 percent of the total
chloride was accounted for in the flue
gases and flyash. In the coal and the coal
+ Eco-Fuel II tests, 36.7 and 67 0 percent,
respectively, of the chlorides entering the
boiler with the fuel were accounted for in
the flue gas.
Total Hydrocarbons
Total hydrocarbon emissions, as meas-
ured by the on-line monitoring instru-
ment, were quite low (<20 ppm) for all
tests. The hydrocarbon analyzer sampled
gases that had been filtered through a
trap and were heated to 200°F. It is
possible that some hydrocarbon species
were scrubbed out of the sampled stack
gases before the gases were analyzed,
however, flame ionization gas chroma-
tography analyses supported the low
hydrocarbon emissions.
Organic Species
Gaseous organic materials extracted
from the flue gas were noticeably higher
when the Americology was burned than
when the Eco-Fuel II was burned. The
burning of both RDFs resulted in higher
organic emissions than when coal was
the only fuel. Measureable organic mate-
rial was observed in the respirable particle
emissions only when burning Americol-
ogy as the only fuel, and the concent rat ion
per cubic meter of the flue gas was about
a factor of 50 below the concentration of
organics collected from the gas stream
itself.
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Polycyclic Organic Materials
(POM)
ROMs were detected and measured in
three tests, both in the flue gas and in the
suspended particulates TheAmencology
RDF fired without coal appeared to result
in higher POM emissions than the Eco-
Fuel II RDF fired without coal Also, the
Amencology RDF fired without coal pro-
duced more ROMs than when co-fired
with coal.
Dioxins
The emissions from the burning of RDF
without coal were analyzed for the dioxm
2,3,7,8 TCDD. No positive identification
of this species was made in either the
suspended paniculate or the gaseous
emissions.
Emissions Analyses
This section summarizes the emissions
measured and analyzed for seven tests.
The distinctions between tests were
primarily related to the different composi-
tions of the fuels fired, although the
physical properties of the RDF fuels
presumably also affected the emissions
and cannot be overlooked. Other than
fuels, there were no major changes in
feed system or boiler operation during the
test program. When coal and RDF were
co-fired, each fuel provided half of the
total heat input to the furnace.
The seven tests conducted were:
• Coal fired only
• Coal co-fired with Eco-Fuel II (50/50
by heat content)
• Eco-Fuel II fired only
• Coal co-fired with Amencology (50/50
by heat content)
• Amencology fired only
• Coal co-fired with Eco-Fuel II + 10 wt
percent hazardous waste
• Coal co-fired with Eco-Fuel II + 5 wt
percent hazardous waste
The weight fraction of hazardous waste
that is reported is the weight of hazardous
waste contained in the Eco-Fuel II pellets,
not the weight fraction of waste in the
coal + Eco-Fuet II.
Table 1 summarizes the emissionsthat
were observed. The average carbon
dioxide (CO2> measured in the stack is
shown for each test The excess air in
each test was maintained at a level just
sufficient to reduce carbon monoxide (CO)
in the stack gas, and the average CO
during all tests was less than 20 ppm.
Applications of Test Results
The principal value of the results of
these tests lies in their comparison with
two related programs using laboratory
scale systems. This comparison should
demonstrate the effects of type of RDF
burning on stack emissions more accu-
rately than a direct comparison of these
laboratory-scale data with full-scale RDF
co-firing data. The temperatures, mixing,
fuel compositions and fuel preparations,
and firing obtained in these small labo-
ratory-scale systems can be more directly
related to larger systems than the resi-
dence times involved. The residence time
in full-scale industrial RDF burning is
much longer, especially in the gas phase
reactions that occur above a bed in a
stoker-fired boiler.
Table 1. Summary of Emission Measurements Burning Coal and Densified RDF in Stoker Fired Boiler
7"esf No.
Fuel Fired"
1
Coal
Only
2
Coal +
Eco-Fuel II
3
Eco-Fuel II
Only
4
Coa/ +
Americology
5
Americology
Only
6
Coal +
Eco-Fuel II
+ TEA™
7
Coal +
Eco-Fuel II
+ TEA1*
Stack Emissions
COi, percent
Particulates, mg/M3
SOz ppm
A/O», ppm
Cr'3', ppm
Organics™, mg/M3
POM™, mg/M3
85
145
477
200
37
?
ND
94
167
462
175
67
576
ND
8.5
111
403
170
12
965
12.1
4.9
323
271
150
115
1170
•19.9
85
417
98
220
245
2870
55.0
87
186
394
260
ND
ND
ND
9 7
206
388
251
ND
ND
ND
ND—not detected.
(1) Coal + RDF runs used as fuels on a 50-50 basis based on heating value.
(2) Triethanolamine, simulating a hazardous waste, was incorporated into RDF fuel pellets @ 10 and 5 wt percent in tests 6 and 7, respectively.
(3) Emitted in gaseous form.
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Bruce Rising and John A lien are with Battelle Columbus Laboratories, Columbus.
OH 43 201.
Michael Black is the EPA Project Officer (see below).
The complete report, entitled "Emissions Assessment for Refuse-Derived Fuel
Combustion," (Order No. PB86-111 218/AS; Cost: $11.95. 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
Official Business
Penalty for Private Use $300
EPA/600/S2-85/116
QOOC3?9 PS
2?0 S DEARBORN STREET
CHICAGO it 60604
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