United States
Environmental Protection
Agency
Atmospheric Sciences ~,
Research Laboratory *
Research Triangle Park NC 27711 ' i'
Research and Development
EPA/600/S3-86/055 Feb. 1987
&EPA Project Summary
Characterization of Stack
Emissions from Municipal
Refuse-to-Energy Systems
J. E. Howes, Jr., D. F. Kohler, F. L. DeRoos, R. M. Riggin, R. L. Barbour, and
R. L. Bennett
Stack emissions from three munici-
pal refuse-to-energy systems were
characterized: refuse-derived fuel
(RDF), mass burning (MASS) and mod-
ular (MOD). A comprehensive set of
measurements was performed at each
site to determine the physical and
chemical properties of the particulate
and gaseous stack emissions.
The physical characterization in-
cluded measurement of the mass con-
centration, and size distribution of the
stack particulate matter. Inorganic
chemical characterization of the stack
emissions included determination of
gaseous HCI and HF emissions, and de-
termination of volatile trace element
levels. The characterization of organic
materials in the stack emissions in-
cluded specific measurements for
polynuclear aromatic hydrocarbons
(PAH), tetrachlorinated benzo-p-
dioxins (TCDD) and dibenzofurans
(TCDF), and aldehydes. Screening
analyses were performed to provide
tentative identification of organic com-
pounds in the stack emissions.
This Project Summary was devel-
oped by EPA's Atmospheric Sciences
Research Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title. (See Project Report ordering infor-
mation at back).
Introduction
Vast quantities of municipal refuse
are generated daily throughout the
United States. Although incineration
has been used for reduction of refuse
volume in the past, the most common
and economical method of disposal has
been the use of landfills or open dumps.
However, the availability and cost of
convenient landfill sites and public ac-
ceptance makes this option less eco-
nomically attractive as a future disposal
method. A second important factor
which will impact on future waste dis-
posal practice is the increased empha-
sis on energy conservation. Municipal
refuse represents an energy source
which when burned can supply steam
for heat and electricity production. Be-
cause of these land and energy conser-
vation considerations, it is anticipated
that there may be a significant increase
in refuse-to-energy incineration of mu-
nicipal refuse in the future.
An important issue which must be ad-
dressed in view of the expected prolifer-
ation of energy-to-refuse incineration
systems is the potential release of haz-
ardous pollutants into the environment
from these facilities. The information
base is limited and additional work is
needed to develop emission data to an-
swer the environmental questions, par-
ticularly in the case of newer refuse-to-
energy incinerator systems.
The purpose of the research program
described in this report was to charac-
terize the physical and chemical compo-
sition of airborne emissions from mu-
nicipal refuse-to-energy units. The
study included a comprehensive set of
physical and chemical measurements
which identify and quantify the emis-
sions of three refuse-to-energy units; a
refuse-derived fuel, mass burning, and
modular design. Thus, the emission
data provides an important contribution
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to the data base available to assess the
environmental impact of refuse-to-
energy systems, to identify specific pol-
lutants which may have adverse health
and/or environmental effects, and to de-
termine the need for process and/or
control technology modifications to re-
duce pollutant emissions.
Procedures
The study involved a comprehensive
set of measurements to characterize the
physical and chemical composition of
stack emissions from three refuse-to-
energy units. A summary of the meas-
urements that were performed and the
sampling and analytical methods that
were employed in the study is given in
Table 1.
Stack emission measurements were
performed on three refuse-to-energy in-
cineration units. A summary of the char-
acteristics of the units is provided in
Table 2. The sites included recently con-
structed units of three different designs;
refuse-derived fuel (RDF), mass burning
(MASS) and modular (MOD). All three
units were fueled with solid municipal
refuse, however, approximately 30 per-
cent of the modular unit feed came from
industrial sources. Refuse feed for the
RDF unit was shredded and pneumati-
cally and magnetically classified while
the MASS and MOD units burned un-
classified bulk refuse. The feed rate data
given in the table are estimates for the
period during which tests were con-
ducted and do not necessarily represent
the design capacity of the units.
At all sites, the emission measure-
ments were performed by sampling
from a duct or stack downstream of the
control devices, if present. Operating
conditions considered "normal" for
each unit prevailed during the respec-
tive test periods.
Results and Discussion
Particulate Mass and Size
Distribution
The particulate mass concentrations
were measured in the emissions from
the RDF, MASS, and MOD units with
EPA Method 5. Additional mass concen-
tration data were obtained from the
SASS tests. Based on the Method 5
data, the mass concentration of particu-
late material in the RDF emissions
ranged from 272 to 441 mg/dscm and
the emission rate ranged from 22.4 to
36.1 kg/hr. For the MASS unit, the ex-
tremes in particulate mass concentra-
tion were approximately 261 and 599
Table 1.
Measurement
Sampling and Analytical Methods Used for Characterization of Refuse-to-EnergyA
System Stack Emissions ™
Sampling Method
Analytical Method
Particulate Mass
Particle Size Distribution
Elemental Composition of
Flyash
Volatile Trace Elements
HCI/HF
Anions in flyash
Polyaromatic hydrocarbons
(PAH)
Tetrachlorodibenzo-p-
dioxins/tetrachlorodibenzo
furans (TCDD/TCDF)
Aldehydes
Organic compound
screening
Volatile organic compounds
EPA Method 5
Gravimetric
Andersen In-Stack Impactor Gravimetric
Source Assessment
Sampling System (SASS)
(Cyclones/filter catch)
SASS (impingers loaded
with ammonium
persulfate/silver nitrate
solution
Impinger train with IN
NaOH solution
SASS (Cyclones/filter catch)
SASS
(Cyclones/filter/XAD-2
catch)
SASS
(Cyclones/filter/XAD-2
catch)
Impinger train with
dinitrophenyl hydrazine
solution
SASS (Cyclones/filter/
XAD-2)
Stainless steel cannister
grab samples
(1) Spark-source mass
spectrometry
(2) X-ray fluorescence
(3) Combustion
Atomic absorption
Ion chromatography
Ion chromatography
Combined high resolution
gas chromatography/
mass spectrometry
(HRGC/MS)
Combined high resolution
gas chromatography/high
resolution mass
spectrometry
(HRGC/HRMS)
High performance liquid
chromatography (HPLC/
fluorescence
HRGC/MS—computer
search/spectra matching
Capillary column gas
chromatography with FID
and EC detection
mg/dscm and the particulate emissions
of the MOD unit based on two valid
tests ranged from approximately 153 to
261 mg/dscm in mass concentration
and from 2 to 3.6 k/g in mass emission
rate.
Particulate size distribution data were
obtained for the three incinerator units.
From the curves obtained, it is evident
that the emissions from none of the
units follow a log-normal distribution.
The approximate mass median diame-
ter of particulate emissions determined
by measurements made with an An-
dersen impactor were: 6 (im for the RDF
unit, 12 fim for the MASS unit, and 0.8
H,m or less for MOD unit. The RDF and
MASS units were equipped with elec-
trostatic precipitators.
Inorganic Emissions
Elements detected in the particulate
emissions of the three units at levels of
10 percent by weight or higher were C
and Cf. Those generally present at or
above 1 percent by weight were Ca, Zn,
Fe, S, Si, KyAI; Madrid Pr>. The prmcipal
anions common to samples from all
three units were sulfate, chloride, and
bromide. The soluble fraction of the fly
ash from the three units varied from ap-
proximately 13 to 77 percent by weight
with the MOD sample exhibiting the
least solubility.
Of the volatile elements measured in
the stack emissions of the three inciner-
ator units, the most abundant element
was Hg, which was found at widely
varying levels; 16 to 6250 jixj/dscm.
Concentrations of As, Se, Sb, and Pb
were generally less than 10 n-g/dscm,
although Sb was detected at a concen-
tration of 42 fig/dscm in one of the
MASS samples. Levels of HCI ranging
from 352 to 516 mg/dscm (263 to 340
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Table 2. Summary of Study Site Characteristics
Refuse-Derived Fuel Unit
Mass Burning Unit
Modular Unit
Site Code
Process characteristics
Feed
Estimated feed rate during study
Emission control
Stack gas temperature
RDF
• shredding
• air classification
• magnetic separation
• semi-suspension stoker-grate
boiler
Municipal refuse
600 TPD
Electrostatic precipitator
230°C
MASS
* mass burning
• bulk refuse
Municipal refuse
125 TPD
Electrostatic precipitator
270°C
MOD
• Consumatunit
• bulk refuse
Municipal and commercial
refuse
SO TPD
None
255°C
ppm) were measured in the RDF and
MASS units. Lower levels of HCI, 53 to
231 mg/dscm (35 to 153 ppm), were de-
tected in the MOD emissions. The con-
centration of HF in the emissions of the
three units was fairly uniform, ranging
from 0.3 to 1.4 mg/dscm (0.4 to
1.7 ppm).
The results of the infrared analysis of
emission samples from the refuse-to-
energy units are summarized and the
infrared spectra of the various samples
are presented in the report. Identifica-
tion of compounds in the paniculate
emission samples from the three units
are given as positive, probable or possi-
ble. In all cases, those identifications
which are only tentative (marked possi-
ble) are of minor or trace components;
because the component is present in
such low concentration, a positive iden-
tification is not possible.
The three samples are similar in com-
position in that they are mixtures of sul-
fatesr, silicates and quartz. Perhaps
more striking is the number of possible
compound types not present, in particu-
lar, metal oxides. Most fly ashes from
combustion sources contain significant
quantities of metal oxides. These sam-
ples contain neither these nor any other
oxide with the possible exception of the
oxides which adsorb only in the far in-
frared region. In addition, though less
surprising, these samples show no indi-
cation of nitrates, phosphates or ammo-
nium compounds which are also fre-
quently found in fly ash.
Organic Emissions
Concentrations of polynuclear aro-
matic hydrocarbons (PAH) compounds
found in the stack emissions of the
refuse-to-energy systems varied widely
for the same unit as well as among the
three units. The lowest values were ob-
served in the MOD emissions and the
highest in the MASS emissions. Com-
pounds present in emissions of all three
units included: naphthalene, phenan-
threne/anthracene, pyrene, ace-
napthylene. The higher molecular
weight PAH compounds, e.g., benzopy-
renes were detected only in the MASS
emissions. Data for the RDF and MASS
units shows that the PAH distribution in
the emissions heavily favors the gas
phase at the temperature maintained
during sample collection (205°C). Sepa-
rate analysis of the paniculate and gas
phase samples was not performed on
the MOD samples.
The TCDD and TCDF data show con-
siderable variation in levels among
tests on the same unit and between
units, however, the variations are not as
great as observed for the PAH com-
pounds. The average total TCDD con-
centrations measured in the RDF,
MASS, and MOD stack emissions were
174, 245, and 11 ng/dscm, respectively.
The 2,3,7,8-TCDD isomer constituted a
significantly larger fraction of the total
TCDD emission from MASS unit than
from the other two incinerators. The av-
erage total TCDF emissions from the
RDF, MASS, and MOD units were 458,
385, and 73 ng/dscm, respectively. The
distribution of TCDD generally appears
to favor the paniculate phase although
RDF Test No. 2 shows the major fraction
in the gas phase. The TCDF data does
not show a clear trend in distribution
between the paniculate and gaseous
phases of the emissions.
The concentrations of aldehydes
found in the incinerator emissions show
large variations in aldehyde levels both
within and between sites. Generally
higher concentrations were observed in
the MASS emissions. The Mass Test
No. 2 data show that the aldehydes
were efficiently collected by the im-
pinger train.
Conclusions and
Recommendations
This study provides physical and
chemical characterization data to sup-
port assessment of the impact of munic-
ipal refuse-to-energy system emissions
on public health and the environment
and to guide future similar studies. The
data show wide variations in the com-
position and levels of various species in
the stack emissions both among the
various units studied and among repeti-
tive measurements at the same unit.
These variations may be due to influ-
ences from one or a combination of the
following factors: unit type, unit design,
refuse composition, or operating condi-
tions. The scope of this study did not
encompass the collection of data and
measurement of the parameters re-
quired to evaluate the factors that influ-
ence refuse-to-energy system emis-
sions. It is assumed that "normal"
operating conditions prevailed during
the emission measurements, however,
the possibility that abnormal operating
events occurred during test period and
that these events influenced the emis-
sion characteristics, cannot be dis-
counted. This possibility should be kept
in mind in considering the following
conclusions.
The high concentration and the rela-
tively large size paniculate emissions
indicate either inefficient operation of
the electrostatic precipitators (ESP)
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on the RDF and MASS units or com-
bustion conditions for which the
ESP's were not designed.
The paniculate emissions from the
three types of refuse-to-energy units
are similar in inorganic chemical
composition. Inorganic compounds
in the emissions are present primarily
as chlorides and sulfates.
The emissions from the municipal
refuse-to-energy units varied greatly
in organic chemical composition. This
result is presumably due to design
differences and variations in refuse
feed composition and operating
parameters of the units.
The study has yielded a comprehen-
sive data base to support environmen-
tal assessment of municipal refuse-to-
energy systems and to identify areas
that may require additional research.
The most urgent need of future studies
is to acquire the supporting data re-
quired to establish the incinerator oper-
ating conditions during emission meas-
urement periods. This information
would identify abnormal conditions
and, in general, would permit the eluci-
dation of the relationship between de-
sign and operating parameters and
emission characteristics.
Based on data obtained in this study,
it appears that improvements in design
or operation of municipal refuse-to-
energy systems could be made to re-
duce stack emissions. In general, modi-
fications e.g., in refuse preparation,
combustion air feed, etc., that increase
combustion efficiency should signifi-
cantly reduce emission levels. Control
devices should also be selected and op-
erated to provide more efficient capture
of particles from the emission stream.
Future studies should adopt a paramet-
ric experimental design to clearly iden-
tify the design and operational variables
that influence emission levels and to op-
timize conditions for emission reduc-
tion.
J. E. Howes. Jr., D. F. Kohler. F. L DeRoos, R. M. Riggin, and R. L. Barbour
are with Battelle Columbus Laboratories, Columbus. OH 43201; the EPA
author Roy L. Bennett (also the EPA Project Officer, see below) is with the
Atmospheric Sciences Research Laboratory, Research Triangle Park, NC
27711.
The complete report, entitled "Characterization of Stack Emissions from
Municipal Refuse-to-Energy Systems." (Order No. PB 87-110 482/AS; Cost:
$18.95, 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:
Atmospheric Sciences Research Laboratory
U.S'. Environmental Protection Agency
Research Triangle Park, NC 27711
United States Center for Environmental Research
Environmental Protection Information
Agency Cincinnati OH 45268
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