United States
Environmental Protection
Agency
Environmental Sciences Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S3-82-095 Aug. 1983
v>EPA Project Summary
Inorganic Compound
Identification of Fly Ash
Emissions from Municipal
Incinerators
W. M. Henry, R. L Barbour, R. J. Jakobsen, and P. M. Schumacher
Paniculate matter emitted as fly ash
from municipal refuse and sludge in-
cineration operations consists largely
(>90 percent) of inorganic substances.
including soot Although it is evident
from the compositions of the wastes
being incinerated that chlorides, sul-
fates, and, in the case of sludge, phos-
phates are potential reactant products
in the combustion process, the inor-
ganic particulate emissions frequently
are referred to as metallic oxides.
Actual inorganic speciation of complex
environmental samples is difficult to
perform and, as a result little direct
information exists on the exact chem-
ical nature of incinerator fly ash emis-
sions. In order to obtain more specific
data on the inorganic compounds pre-
sent a group of stack fly ash emissions
was collected from both municipal
refuse and municipal sludge incinerator
operations. After these emissions were
analyzed for their cation and anion
contents. X-ray diffraction (XRD) and
Fourier Transform infrared (FT-IR) tech-
niques were applied for compound
identification analyses. These latter
analyses showed the presence of many
inorganic species in addition to oxides
in the fly ashes. The use of the FT-IR
technique is detailed in the report
because its application to inorganic
species identification is relatively new.
This Project Summary was developed
by EPA's Environmental Sciences Re-
search 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
information at back).
Introduction
The increasing tonnages of particulate
matter emitted to the atmosphere are a
serious concern in the field. In past years,
waste disposal by incineration lost favor in
some municipalities concerned about their
inability to meet pending air pollution
standards and the concomitant higher
operational costs. Also, greater technical
skill is required for incinerator operation
than for landfill disposal methods. For-
tunately, resistance to incineration is les-
sening because of the magnitude of dis-
posal tonnages, the decreasing availability
of landfill sites, and the attraction of ener-
gy recovery from waste combustion
processes.
Municipal officials charged with the
responsibility for waste disposal must
know the environmental consequences of
incineration, including identification of the
chemical nature of the particulate species
being emitted. These particulates are prin-
cipally inorganic fly ashes.
Because methods for inorganic specia-
tion of emission particulates from inciner-
ation are limited, time consuming, and
technically difficult inorganic emission
constituents are usually determined on
the basis of their metal contents only.
Frequently, these metal contents are math-
ematically converted to oxides in order to
show an approximate material balance for
the fly ash composition; e.g.. Si to SiOj, Al
to AI203. Such arbitrary conversions can
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be misleading, since the incineration fly
ash participates can have a mixture of
origins including:
(1) Mineral residues not destroyed by
the brief passage through the flame
zone or that bypass the central
flame zone.
(2) Molten or solid material formed by
condensation of elementary species
in the immediate post-flame zone.
(3) Nucleated material from supersatu-
rated vapors in the subsequent
cooling zones.
(4) Material added to the existing par-
ticulate by physical and/or chemical
absorption
(5) Compositions formed by reactions
of species in 1 through 4 above.
(6) Physical reconstitution, e.g., crystal-
lization.
Note that in origin 2 (above), the material
undergoes rapid temperature change on
the order of 2000° F in a few seconds, and
there can be a considerable deviation from
the equilibrium composition determined
thermodynamically. Based on these pa-
rameters, fly ashes from the incineration
process will consist of a complex mixture
of amorphous and crystalline substances.
Inorganic speciation, what little has
been done, has relied mostly on X-ray
diffraction, morphological characterization
of particle groups by microscopy, and,
indirectly, by scanning electron transmis-
sion and electron microprobe spectroscopy.
X-ray diffraction is applicable only to crys-
talline compounds, and, as in the case of
fossil-fuel-combustion fly ash, incinera-
tion of waste should result in high concen-
trations of glassy, amorphous species.
Petrographic and other microscopic tech-
niques can look at only small areas and
surfaces of samples that are not repre-
sentative of the total sample. Because of
these limitations, the use of FourierTrans-
form infrared (FT-IR) spectroscopy in this
study emphasized identification of inor-
ganic species in fly ash emissions from
waste incineration operations.
The primary objective of this research
was to identify the inorganic compounds
present in fly ash emissions from incinera-
tion of municipal refuse and sludge. Due to
the high combustion temperature used,
these inorganic constituents should rep-
resent the major portion (>90 weight
percent) of these emissions. Since the
application of FT-IRto inorganic compound
identification and analysis is relatively new,
its use in this program entailed consid-
erable development efforts, including the
preparation of additional spectra to the
researchers' spectral reference library.
These FT-IR development efforts limited
the number of samples to which the
compound analysis could be applied, prin-
cipally to three incinerator fly ash samples,
two from municipal refuse and one from
municipal sludge. These samples were
judged representative of the incineration
fly ashes based on their elemental contents.
A secondary objective of the program
was to obtain data on the elemental
(cation/anion) contents of fly ashes emitted
from waste incineration operations. Most
data given in the literature are for bottom-
ash and precipitator-ash contents and not
for ashes emitted to the atmosphere. To
provide the data needed for this study, six
incinerator operations were sampled and
analyzed.
Conclusions
Samples of fly ash were collected as
paniculate matter emitted from the stacks
of municipal refuse and municipal sludge
incinerators. Based on elemental analyses
of these samples and their compound
structures, the following conclusions were
reached:
(1) The paniculate emissions from the
incinerators are largely (>90 per-
cent) inorganic in nature.
(2) The paniculate emissions are from
one-third to one-half water soluble.
(3) The water soluble phase of the
municipal refuse incinerator fly ashes
is principally chloride and sulfate
salts of Na, K, Ca, and Zn, and, to a
lesser extent NH4+ salts.
(4) The water soluble phase of the
municipal sludge incineratorfly ashes
is principally sulfate, and, to a lesser
extent, phosphate and chloride salts,
also of Na, K, Ca, Zn, and NH4+.
(5) The water insoluble phase of the
municipal refuse incineratorfly ashes
is principally oxide and silicate salts
of Al, Si, Ca, Pb, Zn and Fe, plus
some insoluble sulfate salts and
carbon products.
(6) The water insoluble phase of the
municipal sludge incineratorfly ashes
is principally oxide, silicate, and
phosphate salts of Al, Si, Ca, Pb, Zn
and Fe plus insoluble carbon prod-
ucts.
(7) The major differences between the
composition of the fly ashes from
the two types of incineration pro-
cesses are the high concentrations
of chlorides, derived from plastics in
the municipal refuse feed, and the
high concentration of phosphates,
derived from human and animal
wastes in the municipal sludge feed.
(8) With respect to compound iden- i
tification, the FT-IR technique pro-
vided more definitive information
than was obtained by X-ray diffrac-
tion. Based on the comparatively
low intensities of the X-ray patterns,
both types of incinerator fly ashes
appear to be highly amorphous in
nature and, as such, not as amenable
to XRD as to FT-IR analysis.
Compositional Analysis
Fly ash samples collected from the stack-
sampling ports (beyond any control device)
of municipal refuse and municipal sludge
incinerator plants were analyzed for their
cation/anion contents. As would be ex-
pected from the high-temperature com-
bustion processes, the paniculate emis-
sions consist principally of inorganic mat-
ter including relatively high concentrations
of carbon, presumably uncombusted soot
MeCI2 solubility data indicate an approxi-
mate total organic fraction of 3 to 7
percent The analyses showed the fly ash
emissions to be from 34 to 47 percent
water soluble and weakly acidic in the
water extraction solution. The refuse
ashes are characterized by high concen-
trations of SO4=, Cl~, and low P04~3, and
N03~ contents, whereas the sludge-derived
incinerator fly ashes contain high SO4=
and P04-3 but low Cl~ anions. The N03~
and NH4+ contents of the sludge fly ashes
are higher than those found in the munici-
pal refuse fly ashes, as are many of the
heavy metals, especially Cr, Ni, Cu, Ag, Cd,
Sn, Pb, and Bi. There are only small dif-
ferences between the municipal refuse
and municipal sludge fly ash types with
respect to the concentrations of the major
alkali, alkaline earth, and silicon compo-
nents. The total oxygen contents of the
samples were not determined.
Compound Identification
Prior work on coal- and oil-fired power
plant fly ash emissions has shown that it is
advantageous to analyze the water-insol-
uble'and water-soluble phases of the sam-
ples, as well as the total unseparated
sample when seeking the compounds
present. The insoluble phase should con-
tain the oxides and glass phases of the
samples, as well as insoluble sulfate,
chloride, nitrate, and any soluble phos-
phate forms contained in the total samples.
Identification of compounds in the sep-
arated phases aids in the interpretation of
XRD patterns and FT-IR spectra found in
the total samples.
X-ray Diffraction Analyses
Two municipal refuse samples and one \
municipal sludge fly ash sample were
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analyzed by X-ray diffraction using CuKa
excitation and strip chart recording over
2 6 range from 15 to 70 degrees.
The X-ray diffraction pattern intensities
obtained were relatively weak, possibly
attributable to a low concentration of crys-
talline substances in the samples. The
qualitative identifications are given in
Table 1. In each sample, compounds were
identified in the water-insoluble phase
which could not be identified in the total
sample. The identification of l<2ZnCl4 was
noteworthy. Because little data exist in the
literature on this compound, a reference
sample was prepared to confirm the pat-
tern. Although the reference was prepared
from a solution rather than from a gas-
phase state, this identification appears to
be reasonably certain.
FT-IR Analyses
The same three samples were analyzed
by FT-IR using techniques previously de-
veloped for fossil-fuel power plant par-
ticulate emissions. Infrared spectra were
obtained in the H20 soluble and H20
insoluble fractions of the samples both
before (unbaked) and after heating at
200°C (baked to remove waters of crystal-
lization and readily volatile components).
Our computerized spectral search program"
was used for the water soluble fraction
spectra. Presently, this search program is
of substantial use only on sulfate species
(mainly on the H20 soluble fraction in
which the sulfates predominate), since the
researchers' reference spectra library is
primarily composed of sulfate salts. A new
technique, that of obtaining second deriva-
tive spectra, was used to assist in the data
interpretation. The second derivative spec-
tra are useful in resolving a complex peak
into its components. This overcomes a
major problem in identifying specific com-
pounds in a mixture of similar compounds
by determining the exact frequencies of
several overlapping bands.
Summary of Compound
Identification
Although IR and XRD data are not in
complete agreement correlations between
the two sets of data fit relatively well (see
Table 2) when the data from the total,
water soluble and water insoluble analyses
have been combined. In general, the IR
technique gives more total information
due to the capability of the IR to provide
analyses and speciation of the water
soJuble to components, the amorphous
components, and the organics. The latter
F capability was not utilized on this program.
The incineration fly ash samples do not
Table 1. XRD Analysis of Refuse and Sludge Fly Ashes
Sample Compound PDF #
Pattern Strength
I
As Received
Halite (NaCI)
Anhydrite (CaSO^J
Quartz (
K2ZnCI4
KAJ (804)2
Unknown
5-628
6-226
5-490
30-1015
3-337
100
60
20
20
20
25
I
H2O Insoluble
II
As Received
II
H2Olnsoluble
IV
As Received
IV
H2O Insoluble
V
As Received
Quartz (^-SiO^
Anhydrite (CaSOJ
Anglesite (PbSO^J
Magnetite (FejOjJ
Hematite (oc-Fe2O3)
Halite (NaCI)
Unknown
Halite (NaCI)
Quartz (^-SiO^
Anhydrite (CaSOJ
K2ZnCI4
Unknown (MeCI2 Soluble)
Unknown (MeCI2 Insoluble)
Quartz (oc-SiO^
Calcite (CaCOs)
Anhydrite (CaSOJ
Magnetite (FejOjJ
Unknown
Anhydrite fCaSO^J
Quartz (x-SiO^
Unknown (MeCI2 Soluble)
Unknown (MeCI2 Insoluble)
Quartz ('x-SiO^
Unknown
Calcite (CaCOa)
Goethite (o-FeOOH)
Fe4(P2O7)3
Quartz (•x-Si02)
Halite (NaCI)
Calcite (CaCO^
Unknown
5-490
6-226
5-577
19-629
13-534
5-628
5-628
5-490
6-226
30-1015
5-490
5-586
6-226
19-629
6-226
5-490
5-49O
5-586
29-713
24-526
5-490
5-628
5-586
100
60
60
40
30
10
60
100
10
10
10
30
20
100
30
20
15
30
50
40
100
70
90
100
50
40
70
30
30
30
20
appear to be highly crystalline. This does
not adversely affect the obtaining of IR
spectra, but of course, does limit identi-
fication by XRD. XRD, on the other hand,
provides information on inorganic chlorides
(which give no IR bands) and identifies
oxides with more certainty.
From the IR data alone, it is relatively
easy to distinguish between types of in-
cineration emission sources (i.e., between
refuse and sewage sludge fly ash sam-
ples). For example, the sewage sludge fly
ash samples contain inorganic P-0 com-
pounds and (NH4)2S04 which are found
only in very low amounts in the refuse fly
ashes.
Both fly ash types contain high quanti-
ties (34 to nearly 50 percent) of water
soluble components, mostly sulfate, chlor-
ide and, in the case of sludge fly ashes.
phosphate salts. Obviously, these emis-
sions pose more of an environmental
problem than would be encountered if
they were of a more chemically inert
nature, such as glassy or oxide structures.
The FT-IRtechnique has been shown in
this work and in prior, related studies to be
useful for the identification of inorganic
species in environmental samples. With a
more complete spectral reference library,
sulfate, nitrate, oxide and other metal and
ammonium salts can be individually iden-
tified in samples; in most cases, more
completely identified than can be done
using XRD. In areas where inorganic com-
pound identification is of concern, such as
acid deposition studies, the FT-IR tech-
nique should be considered for use, at
least as a complement to XRD and other
compound-identification techniques.
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Table 2. Identifications Made on Incinerator Fly Ash Samples by IR and XRD
Sample IR Identifications XRD Identifications
I Municipal refuse CaSO4 CaSO4
fly ash- ZnSO4
Na2S04
K2S04
KAI (804)2 KAKSOJ2
PbSO4
NaCI
K2ZnCI4
SiO2 SiO2
Fe304 Fe304
AI203
Inorganic unknown Inorganic unknown
Aliphatic hydrocarbon
Aromatic or olefinic
hydrocarbon
Ester carbonyl
Acid carbonyl
II Municipal refuse CaSO4 CaSO4
fly ash- K2SO4
ZnS04
Na2SO4
PbS04
NaCI
K2ZnCI4
SiO2 Si02
Fe304 Fe304
AI203
CaC03
XHC03
Inorganic unknown Inorganic unknown
Aliphatic hydrocarbon
Aromatic or olefinic
hydrocarbon
Ester carbonyl
Acid carbonyl
Organic unknown
IV Sewage sludge (NH412SO4
fly ash - CaSO4 CaSO4
ZnS04
K2S04
Na2SO4
SiO2 SiO2
Fe203
CaHPO4 CaPO4 CaP2Oj
Inorganic unknown Inorganic unknown
Aliphatic hydrocarbon
Aromatic hydrocarbon
Aromatic ester
Carboxylic acid
Lactone, anhydride, or
peroxide
Organic unknown
. S. GOVERNMENT PRINTING OFFICE: 1983/659-095/0724
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W. M. Henry, R. L Barbour, R. J. Jakobsen, and P. M. Schumacher are with
Battelle, Columbus Laboratories, Columbus, OH 43201.
Kenneth T. Knapp is the EPA Project Officer (see below).
The complete report, entitled "Inorganic Compound Identification of Fly Ash
Emissions from Municipal Incinerators," (Order No. PB 83-146 175; Cost:
$8.50, 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:
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
PS 0000329
U S ENVIR PROTECTION AGENCY
REGION 5 LIBRARY
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CHICAGO IL 60604
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